Subjects -> CHEMISTRY (Total: 1001 journals)
    - ANALYTICAL CHEMISTRY (59 journals)
    - CHEMISTRY (726 journals)
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    - ELECTROCHEMISTRY (28 journals)
    - INORGANIC CHEMISTRY (45 journals)
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CHEMISTRY (726 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
Accounts of Materials Research     Hybrid Journal  
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 36)
ACS Applied Polymer Materials     Hybrid Journal   (Followers: 15)
ACS Catalysis     Hybrid Journal   (Followers: 78)
ACS Chemical Neuroscience     Hybrid Journal   (Followers: 25)
ACS Combinatorial Science     Hybrid Journal   (Followers: 25)
ACS Macro Letters     Hybrid Journal   (Followers: 34)
ACS Materials Letters     Open Access   (Followers: 4)
ACS Medicinal Chemistry Letters     Hybrid Journal   (Followers: 49)
ACS Nano     Hybrid Journal   (Followers: 452)
ACS Photonics     Hybrid Journal   (Followers: 19)
ACS Symposium Series     Full-text available via subscription   (Followers: 3)
ACS Synthetic Biology     Hybrid Journal   (Followers: 40)
Acta Chemica Iasi     Open Access   (Followers: 8)
Acta Chemica Malaysia     Open Access  
Acta Chimica Slovaca     Open Access   (Followers: 4)
Acta Chimica Slovenica     Open Access   (Followers: 2)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access   (Followers: 1)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 10)
Acta Scientifica Naturalis     Open Access   (Followers: 3)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 9)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 10)
Adsorption Science & Technology     Open Access   (Followers: 9)
Advanced Electronic Materials     Hybrid Journal   (Followers: 7)
Advanced Functional Materials     Hybrid Journal   (Followers: 81)
Advanced Journal of Chemistry, Section A     Open Access   (Followers: 15)
Advanced Journal of Chemistry, Section B     Open Access   (Followers: 14)
Advanced Science Focus     Free   (Followers: 7)
Advanced Theory and Simulations     Hybrid Journal   (Followers: 5)
Advanced Therapeutics     Hybrid Journal   (Followers: 1)
Advances in Chemical Engineering and Science     Open Access   (Followers: 108)
Advances in Chemical Science     Open Access   (Followers: 50)
Advances in Chemistry     Open Access   (Followers: 39)
Advances in Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 21)
Advances in Drug Research     Full-text available via subscription   (Followers: 27)
Advances in Environmental Chemistry     Open Access   (Followers: 11)
Advances in Enzyme Research     Open Access   (Followers: 13)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 20)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 11)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 35)
Advances in Nanoparticles     Open Access   (Followers: 20)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 20)
Advances in Polymer Science     Hybrid Journal   (Followers: 54)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 19)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 22)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 7)
Advances in Science and Technology     Full-text available via subscription   (Followers: 17)
Aerosol Science and Engineering     Hybrid Journal  
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 6)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Aggregate     Open Access   (Followers: 3)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 3)
Al-Kimia : Jurnal Penelitian Sains Kimia     Open Access  
Alchemy : Journal of Chemistry     Open Access   (Followers: 5)
Alchemy : Jurnal Penelitian Kimia     Open Access   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
Alotrop     Open Access  
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 71)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 24)
American Journal of Chemistry     Open Access   (Followers: 41)
American Journal of Plant Physiology     Open Access   (Followers: 13)
Analyst     Full-text available via subscription   (Followers: 40)
Analytical Science Advances     Open Access   (Followers: 2)
Angewandte Chemie     Hybrid Journal   (Followers: 234)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 352)
Annales Universitatis Mariae Curie-Sklodowska, sectio AA – Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 8)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 4)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 6)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 13)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 16)
Antiviral Chemistry and Chemotherapy     Open Access   (Followers: 2)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 12)
Applied Spectroscopy     Full-text available via subscription   (Followers: 27)
Applied Surface Science     Hybrid Journal   (Followers: 33)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 1)
Asian Journal of Applied Chemistry Research     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 3)
Asian Journal of Chemical Sciences     Open Access   (Followers: 1)
Asian Journal of Chemistry and Pharmaceutical Sciences     Open Access   (Followers: 2)
Asian Journal of Physical and Chemical Sciences     Open Access   (Followers: 3)
Atomization and Sprays     Full-text available via subscription   (Followers: 8)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 7)
Avances en Quimica     Open Access  
Biochemical Pharmacology     Hybrid Journal   (Followers: 11)
Biochemistry     Hybrid Journal   (Followers: 483)
Biochemistry Insights     Open Access   (Followers: 7)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 11)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 3)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 4)
Biomacromolecules     Hybrid Journal   (Followers: 27)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 11)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 4)
BioNanoScience     Partially Free   (Followers: 6)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 214)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 88)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 4)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of Institute of Chemistry and Chemical Technology, Mongolian Academy of Sciences     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 1)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 26)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 5)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 2)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 13)
Canadian Mineralogist     Full-text available via subscription   (Followers: 7)
Carbohydrate Polymer Technologies and Applications     Open Access   (Followers: 3)
Carbohydrate Polymers     Hybrid Journal   (Followers: 13)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 76)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 9)
Catalysis Science and Technology     Hybrid Journal   (Followers: 13)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 4)
Catalysts     Open Access   (Followers: 14)
Cell Reports Physical Science     Open Access  
Cellulose     Hybrid Journal   (Followers: 17)
Cereal Chemistry     Full-text available via subscription   (Followers: 6)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 3)
ChemCatChem     Hybrid Journal   (Followers: 11)
Chemical and Engineering News     Free   (Followers: 24)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 88)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 28)
Chemical Physics Letters : X     Open Access   (Followers: 4)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 4)
Chemical Research in Toxicology     Hybrid Journal   (Followers: 25)
Chemical Reviews     Hybrid Journal   (Followers: 266)
Chemical Science     Open Access   (Followers: 44)
Chemical Science International Journal     Open Access   (Followers: 1)
Chemical Technology     Open Access   (Followers: 71)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 56)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 23)
ChemInform     Hybrid Journal   (Followers: 9)
Chemistry     Open Access  
Chemistry & Biodiversity     Hybrid Journal   (Followers: 7)
Chemistry & Biology     Full-text available via subscription   (Followers: 31)
Chemistry & Industry     Full-text available via subscription   (Followers: 8)
Chemistry - A European Journal     Hybrid Journal   (Followers: 223)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 20)
Chemistry Africa : A Journal of the Tunisian Chemical Society     Hybrid Journal  
Chemistry and Materials Research     Open Access   (Followers: 24)
Chemistry Central Journal     Open Access   (Followers: 5)
Chemistry Education Research and Practice     Free   (Followers: 8)
Chemistry Education Review     Open Access   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry Letters     Full-text available via subscription   (Followers: 49)
Chemistry of Heterocyclic Compounds     Hybrid Journal   (Followers: 4)
Chemistry of Materials     Hybrid Journal   (Followers: 337)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 10)
Chemistry World     Full-text available via subscription   (Followers: 20)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 1)
ChemistrySelect     Hybrid Journal  
Chemistry–Methods     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
ChemNanoMat     Hybrid Journal   (Followers: 1)
Chemoecology     Hybrid Journal   (Followers: 3)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 14)
Chemosensors     Open Access   (Followers: 1)
ChemPhotoChem     Hybrid Journal  
ChemPhysChem     Hybrid Journal   (Followers: 14)
ChemPlusChem     Hybrid Journal   (Followers: 2)
Chempublish Journal     Open Access   (Followers: 1)
ChemSystemsChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal   (Followers: 1)
CHIMIA International Journal for Chemistry     Open Access   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 13)
Chromatographia     Hybrid Journal   (Followers: 22)
Chromatography     Open Access   (Followers: 3)
Chromatography Research International     Open Access   (Followers: 5)
Ciencia     Open Access   (Followers: 1)
Clay Minerals     Hybrid Journal   (Followers: 9)
Cogent Chemistry     Open Access   (Followers: 3)
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 12)
Colloids and Interfaces     Open Access  
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 8)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 24)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)

        1 2 3 4 | Last

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Number of Followers: 1  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2227-9040
Published by MDPI Homepage  [238 journals]
  • Chemosensors, Vol. 9, Pages 237: Study of Photoregeneration of Zinc
           Phthalocyanine Chemiresistor after Exposure to Nitrogen Dioxide

    • Authors: David Tomeček, Lesia Piliai, Martin Hruška, Přemysl Fitl, Virginie Gadenne, Mykhailo Vorokhta, Iva Matolínová, Martin Vrňata
      First page: 237
      Abstract: In this work, we present a complex study of photoregeneration of a zinc phthalocyanine (ZnPc) sensor by illumination from light-emitting diodes (LEDs). It includes an investigation of photoregeneration effectivity for various wavelengths (412–723 nm) of incident light carried out at sensor operating temperatures of 55 °C. It is demonstrated that the efficiency of photoregeneration is increasing with a decrease in the light wavelength. In the region of longer wavelengths (723–630 nm), the regeneration degree (RD) was low and ranged from 12% to 15%. In the region of shorter wavelengths (518–412 nm), the RD rose from 35% for 518 nm to 94% for 412 nm. The efficiency of photoregeneration is also shown to be higher in comparison with the temperature regeneration efficiency. In order to understand the chemism of photoregeneration processes, the electrical measurements are supplemented with Raman and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) studies. The spectroscopic results showed that nitrogen dioxide bonds to the Zn atom in ZnPc in the form of NO2− and NO−, i.e., partial decomposition of NO2 molecules occurs during the interaction with the surface. NAP-XPS spectra proved that light illumination of the ZnPc surface is essential for almost complete desorption of NOx species. At the same time, it is demonstrated that in case of long-time exposure or exposure of a ZnPc chemiresistor with a high concentration of NO2, the oxygen, released due to the NO2 decomposition, slowly but irreversibly oxidizes the layer. This oxidation process is most probably responsible for the sensor deactivation observed in sensor experiments with high NO2 concentrations. Based on these studies, the mechanism of nitrogen dioxide interaction with zinc phthalocyanine both under LED illumination and in dark conditions is proposed, and a special method for the sensor operation called “constant exposure dose” is established.
      Citation: Chemosensors
      PubDate: 2021-08-24
      DOI: 10.3390/chemosensors9090237
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 238: Novel Electrochemical Molecularly
           Imprinted Polymer-Based Biosensor for Tau Protein Detection

    • Authors: Amira Ben Hassine, Noureddine Raouafi, Felismina T. C. Moreira
      First page: 238
      Abstract: A novel electrochemical biosensor based on a molecularly imprinted polymer (MIP) was developed for the impedimetric determination of Tau protein, a biomarker of Alzheimer’s disease (AD). Indeed, a recent correlation between AD symptoms and the presence of Tau proteins in their aggregated form made hyperphosphorylated Tau protein (Tangles) a promising biomarker for Alzheimer’s diagnosis. The MIP was directly assembled on a screen-printed carbon electrode (C-SPE) and prepared by electropolymerization of 3-aminophenol (AMP) in the presence of the protein template (p-Tau-441) using cyclic voltammetry. The p-Tau-441 protein bound to the polymeric backbone was digested by the action of the proteolytic activity of proteinase K in urea and then washed away to create vacant sites. The performances of the corresponding imprinted and non-imprinted electrodes were evaluated by electrochemical impedance spectroscopy. The detection limit of the MIP-based sensors was 0.02 pM in PBS buffer pH 5.6. Good selectivity and good results in serum samples were obtained with the developed platform. The biosensor described in this work is a potential tool for screening Tau protein on-site and an attractive complement to clinically established methodologies methods as it is easy to fabricate, has a short response time and is inexpensive.
      Citation: Chemosensors
      PubDate: 2021-08-25
      DOI: 10.3390/chemosensors9090238
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 239: Optimization of Plastic Scintillator for
           Detection of Gamma-Rays: Simulation and Experimental Study

    • Authors: Sujung Min, Youngsu Kim, Kwang-Hoon Ko, Bumkyung Seo, JaeHak Cheong, Changhyun Roh, Sangbum Hong
      First page: 239
      Abstract: Plastic scintillators are widely used in various radiation measurement applications, and the use of plastic scintillators for nuclear applications including decommissioning, such as gamma-ray detection and measurement, is an important concern. With regard to efficient and effective gamma-ray detection, the optimization for thickness of plastic scintillator is strongly needed. Here, we elucidate optimization of the thickness of high-performance plastic scintillator using high atomic number material. Moreover, the EJ-200 of commercial plastic scintillators with the same thickness was compared. Two computational simulation codes (MCNP, GEANT4) were used for thickness optimization and were compared with experimental results to verify data obtained by computational simulation. From the obtained results, it was confirmed that the difference in total counts was less than 10% in the thickness of the scintillator of 50 mm or more, which means optimized thickness for high efficiency gamma-ray detection such as radioactive 137Cs and 60CO. Finally, simulated results, along with experimental data, were discussed in this study. The results of this study can be used as basic data for optimizing the thickness of plastic scintillators using high atomic number elements for radiation detection and monitoring.
      Citation: Chemosensors
      PubDate: 2021-08-25
      DOI: 10.3390/chemosensors9090239
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 240: Impedimetric Detection of Albumin-Bound
           Fatty Acids Using Graphene Oxide Electrode

    • Authors: Zihni Onur Uygun, Soner Duman, Ismail Oran
      First page: 240
      Abstract: The fatty acid/albumin (FA/Alb) molar ratio is ≤1 in healthy subjects; this ratio can reach 3–4 in patients with acute myocardial ischemia. We describe the spontaneous desorption–adsorption kinetics of FAs from albumin to a graphene electrode at neutral pH. Albumin-depleted human serum was prepared via ultrafiltration and then mixed with defatted human albumin and sodium oleate at different FA/Alb molar ratios, at a final albumin concentration of 0.6 mM. A commercially available screen-printed graphene oxide (GO)-modified carbon electrode was used for the electrochemical experiments. Frequency-ranged Faradaic electrochemical impedance spectroscopy (EIS) and a single-frequency non-Faradaic impedance measure (chronoimpedance) were used to derive the desorption–adsorption kinetics. The surface of the GO electrode was finally evaluated with the aid of X-ray photoelectron spectroscopy (XPS). With the chronoimpedance experiment, the measured impedance increased accordingly to the FA/Alb ratios. The frequency-ranged EIS showed good linearity between the impedance and the FA/Alb ratio, with a limit of quantification value of 1.06. XPS surface analysis revealed that the FA was adsorbed onto the electrode, with the amount of the adsorbed FA proportional to the FA/Alb ratio. The electrochemical method applied on this peculiar desorption–adsorption kinetics of FAs has the ability to differentiate serum having excess FAs.
      Citation: Chemosensors
      PubDate: 2021-08-26
      DOI: 10.3390/chemosensors9090240
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 241: Nickel Manganite-Sodium Alginate
           Nano-Biocomposite for Temperature Sensing

    • Authors: Milena P. Dojcinovic, Zorka Z. Vasiljevic, Janez Kovac, Nenad B. Tadic, Maria Vesna Nikolic
      First page: 241
      Abstract: Nanocrystalline nickel manganite (NiMn2O4) powder with a pure cubic spinel phase structure was synthesized via sol-gel combustion and characterized with XRD, FT-IR, XPS and SEM. The powder was mixed with sodium alginate gel to form a nano-biocomposite gel, dried at room temperature to form a thick film and characterized with FT-IR and SEM. DC resistance and AC impedance of sensor test structures obtained by drop casting the nano-biocomposite gel onto test interdigitated PdAg electrodes on an alumina substrate were measured in the temperature range of 20–50 °C at a constant relative humidity (RH) of 50% and at room temperature (25 °C) in the RH range of 40–90%. The material constant obtained from the measured decrease in resistance with temperature was determined to be 4523 K, while the temperature sensitivity at room temperature (25 °C) was −5.09%/K. Analysis of the complex impedance plots showed a dominant influence of grains. The decrease in complex impedance with increase in temperature confirmed the negative temperature coefficient effect. The grain resistance and grain relaxation frequency were determined using an equivalent circuit. The activation energy for conduction was determined as 0.45 eV from the temperature dependence of the grain resistance according to the small polaron hopping model, while the activation energy for relaxation was 0.43 eV determined from the Arrhenius dependence of the grain relaxation frequency on temperature.
      Citation: Chemosensors
      PubDate: 2021-08-27
      DOI: 10.3390/chemosensors9090241
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 242: Enantioselective Monitoring of
           Biodegradation of Ketamine and Its Metabolite Norketamine by Liquid

    • Authors: Ariana Pérez-Pereira, Alexandra Maia, Virgínia Gonçalves, Cláudia Ribeiro, Maria Elizabeth Tiritan
      First page: 242
      Abstract: Ketamine (K) and its main metabolite, norketamine (NK), are chiral compounds that have been found in effluents from wastewater treatment plants (WWTPs) and aquatic environments. Little is known about their enantioselective biodegradation during sewage treatment; however, this information is pivotal for risk assessment, the evaluation of WWTP performance and wastewater epidemiological studies. The aim of this study was to investigate the biodegradation pattern of the enantiomers of K by activated sludge (AS) from a WWTP. For that, an enantioselective liquid chromatography with diode array detection (LC-DAD) method was developed and validated to quantify the enantiomers of K and NK. Both K and NK enantiomers were separated, in the same chromatographic run, using a Lux® 3 µm cellulose-4 analytical column under isocratic elution mode. The method was demonstrated to be linear (r2 > 0.99) and precise (<11.3%). Accuracy ranged between 85.9 and 113.6% and recovery ranged between 50.1 and 86.9%. The limit of quantification was 1.25 µg/mL for the enantiomers of NK and 2.5 µg/mL for K. The method was applied to monitor the biodegradation assay of the enantiomers of K by AS for 14 days. K was poorly biodegraded, less than 15% for both enantiomers, and enantioselectivity in the biodegradation was not observed. The metabolite NK and other possible degradation products were not detected. This work reports, for the first time, the behavior of both enantiomers of K in biodegradation studies.
      Citation: Chemosensors
      PubDate: 2021-08-30
      DOI: 10.3390/chemosensors9090242
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 243: Performance Analysis of MAU-9
           Electronic-Nose MOS Sensor Array Components and ANN Classification Methods
           for Discrimination of Herb and Fruit Essential Oils

    • Authors: Mansour Rasekh, Hamed Karami, Alphus Dan Wilson, Marek Gancarz
      First page: 243
      Abstract: The recent development of MAU-9 electronic sensory methods, based on artificial olfaction detection of volatile emissions using an experimental metal oxide semiconductor (MOS)-type electronic-nose (e-nose) device, have provided novel means for the effective discovery of adulterated and counterfeit essential oil-based plant products sold in worldwide commercial markets. These new methods have the potential of facilitating enforcement of regulatory quality assurance (QA) for authentication of plant product genuineness and quality through rapid evaluation by volatile (aroma) emissions. The MAU-9 e-nose system was further evaluated using performance-analysis methods to determine ways for improving on overall system operation and effectiveness in discriminating and classifying volatile essential oils derived from fruit and herbal edible plants. Individual MOS-sensor components in the e-nose sensor array were performance tested for their effectiveness in contributing to discriminations of volatile organic compounds (VOCs) analyzed in headspace from purified essential oils using artificial neural network (ANN) classification. Two additional statistical data-analysis methods, including principal regression (PR) and partial least squares (PLS), were also compared. All statistical methods tested effectively classified essential oils with high accuracy. Aroma classification with PLS method using 2 optimal MOS sensors yielded much higher accuracy than using all nine sensors. The accuracy of 2-group and 6-group classifications of essentials oils by ANN was 100% and 98.9%, respectively.
      Citation: Chemosensors
      PubDate: 2021-08-31
      DOI: 10.3390/chemosensors9090243
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 244: Insights about CO Gas-Sensing Mechanism
           with NiO-Based Gas Sensors—The Influence of Humidity

    • Authors: Cristian E. Simion, Corneliu Ghica, Catalina G. Mihalcea, Daniela Ghica, Ionel Mercioniu, Simona Somacescu, Ovidiu G. Florea, Adelina Stanoiu
      First page: 244
      Abstract: Polycrystalline NiO thick film-based gas sensors have been exposed to different test gas atmospheres at 250 °C and measured via simultaneous electrical resistance and work function investigations. Accordingly, we decoupled different features manifested toward the potential changes, i.e., work function, band-bending, and electron affinity. The experimental results have shown that the presence of moisture induces an unusual behavior toward carbon monoxide (CO) detection by considering different surface adsorption sites. On this basis, we derived an appropriate detection mechanism capable of explaining the lack of moisture influence over the CO detection with NiO-sensitive materials. As such, CO might have both chemical and dipolar interactions with pre-adsorbed or lattice oxygen species, thus canceling out the effect of moisture. Additionally, morphology, structure, and surface chemistry were addressed, and the results have been linked to the sensing properties envisaging the role played by the porous quasispherical–hollow structures and surface hydration.
      Citation: Chemosensors
      PubDate: 2021-09-01
      DOI: 10.3390/chemosensors9090244
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 245: Identification of Chiral-Specific Carbon
           Nanotube Binding Peptides Using a Modified Biopanning Method

    • Authors: Rachel Krabacher, Steve Kim, Yen Ngo, Joseph Slocik, Christina Harsch, Rajesh Naik
      First page: 245
      Abstract: Peptides can recognize and selectively bind to a wide variety of materials dependent on both their surface properties and the environment. Biopanning with phage or cell peptide display libraries can identify material-specific binding peptides. However, the limitations with sequence diversity of traditional bacteriophage (phage) display libraries and loss of unique phage clones during the amplification cycles results in a smaller pool of peptide sequences identified. False positive sequences tend to emerge during the biopanning process due to highly proliferating, yet nonspecific, phages. In order to overcome this limitation of traditional biopanning methodology, a modified method using high-throughput next generation sequencing (HTS) was tested to select for unique peptides specific to two types of single wall carbon nanotube (SWNTs) sources with varying diameter distribution and chirality. Here, the process, analysis, and characterization of peptide sequences identified using the modified method is further described and compared to a peptide identified in literature using the traditional method. Selected sequences from this study were incorporated in a SWNT dispersion experiment to probe their selectivity to the nanotube diameter. We show that NHTS can uncover unique binding sequences that might have otherwise been lost during the traditional biopanning method.
      Citation: Chemosensors
      PubDate: 2021-09-01
      DOI: 10.3390/chemosensors9090245
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 246: Chemiresistors Based on Li-Doped
           CuO–TiO2 Films

    • Authors: Alfio Torrisi, Jiří Vacík, Giovanni Ceccio, Antonino Cannavò, Vasily Lavrentiev, Pavel Horák, Roman Yatskiv, Jan Vaniš, Jan Grym, Ladislav Fišer, Martin Hruška, Přemysl Fitl, Jaroslav Otta, Martin Vrňata
      First page: 246
      Abstract: Chemiresistors based on thin films of the Li-doped CuO–TiO2 heterojunctions were synthesized by a 2-step method: (i) repeated ion beam sputtering of the building elements (on the Si substrates and multisensor platforms); and (ii) thermal annealing in flowing air. The structure and composition of the films were analyzed by several methods: Rutherford Backscattering (RBS), Neutron Depth Profiling (NDP), Secondary Ion Mass Spectrometry (SIMS), and Atomic Force Microscopy (AFM), and their sensitivity to gaseous analytes was evaluated using a specific lab-made device operating in a continuous gas flow mode. The obtained results showed that the Li doping significantly increased the sensitivity of the sensors to oxidizing gases, such as NO2, O3, and Cl2, but not to reducing H2. The sensing response of the CuO–TiO2–Li chemiresistors improved with increasing Li content. For the best sensors with about 15% Li atoms, the detection limits were as follows: NO2 → 0.5 ppm, O3 → 10 ppb, and Cl2 → 0.1 ppm. The Li-doped sensors showed excellent sensing performance at a lower operating temperature (200 °C); however, even though their response time was only a few minutes, their recovery was slow (up to a few hours) and incomplete.
      Citation: Chemosensors
      PubDate: 2021-09-02
      DOI: 10.3390/chemosensors9090246
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 247: Nickel-Oxide Based Thick-Film Gas Sensors
           for Volatile Organic Compound Detection

    • Authors: Sai Kiran Ayyala, James A. Covington
      First page: 247
      Abstract: In this paper, we report on the development of a highly sensitive and humidity-tolerant metal-oxide-based volatile organic compound (VOC) sensor, capable of rapidly detecting low concentrations of VOCs. For this, we successfully fabricated two different thicknesses of nickel oxide (NiO) sensors using a spin-coating technique and tested them with seven different common VOCs at 40% r.h. The measured film thickness of the spin-coated NiO was ~5 μm (S-5) and ~10 μm (S-10). The fastest response and recovery times for all VOCs were less than 80 s and 120 s, respectively. The highest response (Rg/Ra = 1.5 for 5 ppm ethanol) was observed at 350 °C for both sensors. Sensors were also tested in two different humidity conditions (40% and 90% r.h.). The humidity did not significantly influence the observed sensitivity of the films. Furthermore, S-10 NiO showed only a 3% drift in the baseline resistance between the two humidity conditions, making our sensor humidity-tolerant compared to traditional n-type sensors. Thus, we propose thick-film NiO (10 μm) sensing material as an interesting alternative VOC sensor that is fast and humidity-tolerant.
      Citation: Chemosensors
      PubDate: 2021-09-03
      DOI: 10.3390/chemosensors9090247
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 248: Alveolus Lung-on-a-Chip Platform: A

    • Authors: Noelia Campillo, Vinicius Rosa Oliveira, Renata Kelly da Palma
      First page: 248
      Abstract: Respiratory diseases are top-ranked causes of deaths and disabilities around the world, making new approaches to the treatment necessary. In recent years, lung-on-a-chip platforms have emerged as a potential candidate to replace animal experiments because they can successfully simulate human physiology. In this review, we discuss the main respiratory diseases and their pathophysiology, how to model a lung microenvironment, and how to translate it to clinical applications. Furthermore, we propose a novel alveolus lung-on-a-chip platform, based on all currently available methodologies. This review provides solutions and new ideas to improve the alveolar lung-on-a-chip platform. Finally, we provided evidence that approaches such as 3D printing, organ-a-chip devices and organoids can be used in combination, and some challenges could be overcome.
      Citation: Chemosensors
      PubDate: 2021-09-03
      DOI: 10.3390/chemosensors9090248
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 249: Single Nanowire Gas Sensor Able to
           Distinguish Fish and Meat and Evaluate Their Degree of Freshness

    • Authors: Matteo Tonezzer
      First page: 249
      Abstract: A non-invasive, small, and fast device is needed for food freshness monitoring, as current techniques do not meet these criteria. In this study, a resistive sensor composed of a single semiconductor nanowire was used at different temperatures, combining the responses and processing them with multivariate statistical analysis techniques. The sensor, very sensitive to ammonia and total volatile basic nitrogen, proved to be able to distinguish samples of fish (marble trout, Salmo trutta marmoratus) and meat (pork, Sus scrofa domesticus), both stored at room temperature and 4 °C in the refrigerator. Once separated, the fish and meat samples were classified by the degree of freshness/degradation with two different classifiers. The sensor classified the samples (trout and pork) correctly in 95.2% of cases. The degree of freshness was correctly assessed in 90.5% of cases. Considering only the errors with repercussions (when a fresh sample was evaluated as degraded, or a degraded sample was evaluated as edible) the accuracy increased to 95.2%. Considering the size (less than a square millimeter) and the speed (less than a minute), this type of sensor could be used to monitor food production and distribution chains.
      Citation: Chemosensors
      PubDate: 2021-09-03
      DOI: 10.3390/chemosensors9090249
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 250: Application of a Fluorescent Biosensor in
           Determining the Binding of 5-HT to Calmodulin

    • Authors: L. X. Vásquez-Bochm, Isabel Velázquez-López, Rachel Mata, Alejandro Sosa-Peinado, Patricia Cano-Sánchez, Martin González-Andrade
      First page: 250
      Abstract: Here, we show the utility of the fluorescent biosensor hCaM-M124C-mBBr in detecting and determining the affinity of serotonin (5-HT). We obtained a Kd of 5-HT (0.71 μm) for the first time, the same order of magnitude as most anti-CaM drugs. This data can contribute to understanding the direct and indirect modulation of CaM on its binding proteins when the 5-HT concentration varies in different tissues or explain some of the side effects of anti-CaM drugs. On the other hand, molecular modeling tools help the rational design of biosensors and adequately complement the experimental results. For example, the docking study indicates that 5-HT binds at the same site as chlorpromazine (site 1) with a theoretical Ki of 2.84 μM; while the molecular dynamics simulations indicate a stability of the CaM–5-HT complex with a theoretical ΔG of −4.85 kcal mol−1, where the enthalpy contribution is greater. Thus, the combination of biotechnology and bioinformatics helps in the design and construction of more robust biosensors.
      Citation: Chemosensors
      PubDate: 2021-09-05
      DOI: 10.3390/chemosensors9090250
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 251: Design and Calibration of Moisture Sensor
           Based on Electromagnetic Field Measurement for Irrigation Monitoring

    • Authors: Daniel A. Basterrechea, Javier Rocher, Mar Parra, Lorena Parra, Jose F. Marin, Pedro V. Mauri, Jaime Lloret
      First page: 251
      Abstract: Soil moisture control is crucial to assess irrigation efficiency in green areas and agriculture. In this paper, we propose the design and calibration of a sensor based on inductive coils and electromagnetic fields. The proposed prototypes should meet a series of requirements such as low power consumption, low relative error, and a high voltage difference between the minimum and maximum moisture. We tested different prototypes based on two copper coils divided into two different sets (P1–P15 and NP1–NP4). The prototypes have different characteristics: variations in the number and distribution of spires, existence or absence of casing, and copper wires with a diameter of 0.4 or 0.6 mm. In the first set of experiments carried out in commercial soil, the results showed that the best prototypes were P5, P8, and P9. These prototypes were used in different types of soils, and P8 was selected for the subsequent tests. We carried the second set of experiments using soil from an agricultural field. Based on the data gathered, mathematical models for the calibration of prototypes were obtained and verified. In some cases, two equations were used for different moisture intervals in a single prototype. According to the verification results, NP2 is the best prototype for monitoring the moisture in agricultural lands. It presented a difference in induced voltage of 1.8 V, at 500 kHz, between wet and dry soil with a maximum voltage of 5.12 V. The verification of the calibration determined that the calibration using two mathematical models offers better results, with an average absolute error of 2.1% of moisture.
      Citation: Chemosensors
      PubDate: 2021-09-06
      DOI: 10.3390/chemosensors9090251
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 252: Additive Manufacturing as a Means of Gas
           Sensor Development for Battery Health Monitoring

    • Authors: Oleg Lupan, Helge Krüger, Leonard Siebert, Nicolai Ababii, Niklas Kohlmann, Artur Buzdugan, Mani Teja Bodduluri, Nicolae Magariu, Maik-Ivo Terasa, Thomas Strunskus, Lorenz Kienle, Rainer Adelung, Sandra Hansen
      First page: 252
      Abstract: Lithium-ion batteries (LIBs) still need continuous safety monitoring based on their intrinsic properties, as well as due to the increase in their sizes and device requirements. The main causes of fires and explosions in LIBs are heat leakage and the presence of highly inflammable components. Therefore, it is necessary to improve the safety of the batteries by preventing the generation of these gases and/or their early detection with sensors. The improvement of such safety sensors requires new approaches in their manufacturing. There is a growing role for research of nanostructured sensor’s durability in the field of ionizing radiation that also can induce structural changes in the LIB’s component materials, thus contributing to the elucidation of fundamental physicochemical processes; catalytic reactions or inhibitions of the chemical reactions on which the work of the sensors is based. A current method widely used in various fields, Direct Ink Writing (DIW), has been used to manufacture heterostructures of Al2O3/CuO and CuO:Fe2O3, followed by an additional ALD and thermal annealing step. The detection properties of these 3D-DIW printed heterostructures showed responses to 1,3-dioxolan (DOL), 1,2-dimethoxyethane (DME) vapors, as well as to typically used LIB electrolytes containing LiTFSI and LiNO3 salts in a mixture of DOL:DME, as well also to LiPF6 salts in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) at operating temperatures of 200 °C–350 °C with relatively high responses. The combination of the possibility to detect electrolyte vapors used in LIBs and size control by the 3D-DIW printing method makes these heterostructures extremely attractive in controlling the safety of batteries.
      Citation: Chemosensors
      PubDate: 2021-09-06
      DOI: 10.3390/chemosensors9090252
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 253: Electrochemical Sensing and Removal of
           Cesium from Water Using Prussian Blue Nanoparticle-Modified Screen-Printed

    • Authors: Prem. C. Pandey, Hari Prakash Yadav, Shubhangi Shukla, Roger J. Narayan
      First page: 253
      Abstract: Selective screening followed by the sensing of cesium radionuclides from contaminated water is a challenging technical issue. In this study, the adsorption functionality of Prussian blue (PB) nanoparticles was utilized for the detection and efficient removal of cesium cations. An efficient PB nanoparticle-modified screen-printed electrode (SPE) in the three-electrode configuration was developed for the electrochemical sensing and removal of Cs+. PB nanoparticles inks were obtained using a facile two-step process that was previously described as suitable for dispensing over freshly prepared screen-printed electrodes. The PB nanoparticle-modified SPE induced a cesium adsorption-dependent chronoamperometric signal based on ion exchange as a function of cesium concentration. This ion exchange, which is reversible and rapid, is associated with electron transfer in the PB nanoparticle-modified SPE. Using this electrochemical adsorption system (EAS) based on chronoamperometry, the maximum adsorption capacity (Qmax) of Cs+ ions in the PB nanoparticle-modified SPE reached up to 325 ± 1 mg·g−1 in a 50 ± 0.5 μM Cs+ solution, with a distribution coefficient (Kd) of 580 ± 5 L·g−1 for Cs+ removal. The cesium concentration-dependent adsorption of PB nanoparticles was also demonstrated by fluorescence spectroscopy based on fluorescence quenching of PB nanoparticles as a function of cesium concentration using a standard fluorophore like fluorescein in a manner analogous to that previously reported for As(III).
      Citation: Chemosensors
      PubDate: 2021-09-07
      DOI: 10.3390/chemosensors9090253
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 254: Recent Advances in Electrochemical
           Chitosan-Based Chemosensors and Biosensors: Applications in Food Safety

    • Authors: Rita Petrucci, Mauro Pasquali, Francesca Anna Scaramuzzo, Antonella Curulli
      First page: 254
      Abstract: Chitosan is a biopolymer derived from chitin. It is a non-toxic, biocompatible, bioactive, and biodegradable polymer. Due to its properties, chitosan has found applications in several and different fields such as agriculture, food industry, medicine, paper fabrication, textile industry, and water treatment. In addition to these properties, chitosan has a good film-forming ability which allows it to be widely used for the development of sensors and biosensors. This review is focused on the use of chitosan for the formulation of electrochemical chemosensors. It also aims to provide an overview of the advantages of using chitosan as an immobilization platform for biomolecules by highlighting its applications in electrochemical biosensors. Finally, applications of chitosan-based electrochemical chemosensors and biosensors in food safety are illustrated.
      Citation: Chemosensors
      PubDate: 2021-09-08
      DOI: 10.3390/chemosensors9090254
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 255: Dummy Molecularly Imprinted Polymers
           Using DNP as a Template Molecule for Explosive Sensing and Nitroaromatic
           Compound Discrimination

    • Authors: Anna Herrera-Chacon, Andreu Gonzalez-Calabuig, Manel del Valle
      First page: 255
      Abstract: This work reports a rapid, simple and low-cost voltammetric sensor based on a dummy molecularly imprinted polymer (MIP) that uses 2,4-dinitrophenol (DNP) as a template for the quantification of 2,4,6-trinitrotoluene (TNT) and DNP, and the identification of related substances. Once the polymer was synthesised by thermal precipitation polymerisation, it was integrated onto a graphite epoxy composite (GEC) electrode via sol–gel immobilisation. Scanning electron microscopy (SEM) was performed in order to characterise the polymer and the sensor surface. Responses towards DNP and TNT were evaluated, displaying a linear response range of 1.5 to 8.0 µmol L−1 for DNP and 1.3 to 6.5 µmol L−1 for TNT; the estimated limits of detection were 0.59 µmol L−1 and 0.29 µmol L−1, for DNP and TNT, respectively. Chemometric tools, in particular principal component analysis (PCA), demonstrated the possibilities of the MIP-modified electrodes in nitroaromatic and potential interfering species discrimination with multiple potential applications in the environmental field.
      Citation: Chemosensors
      PubDate: 2021-09-08
      DOI: 10.3390/chemosensors9090255
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 256: Biosensors for Detection and Monitoring
           of Joint Infections

    • Authors: Umile Giuseppe Longo, Sergio De Salvatore, Alessandro Zompanti, Calogero Di Naro, Simone Grasso, Carlo Casciaro, Anna Sabatini, Alessandro Mazzola, Giorgio Pennazza, Marco Santonico, Vincenzo Denaro
      First page: 256
      Abstract: The aim of this review is to assess the use of biosensors in the diagnosis and monitoring of joint infection (JI). JI is worldwide considered a significant cause of morbidity and mortality in developed countries. Due to the progressive ageing of the global population, the request for joint replacement increases, with a significant rise in the risk of periprosthetic joint infection (PJI). Nowadays, the diagnosis of JI is based on clinical and radiological findings. Nuclear imaging studies are an option but are not cost-effective. Serum inflammatory markers and the analysis of the aspirated synovial fluid are required to confirm the diagnosis. However, a quick and accurate diagnosis of JI may remain elusive as no rapid and highly accurate diagnostic method was validated. A comprehensive search on Medline, EMBASE, Scopus, CINAH, CENTRAL, Google Scholar, and Web of Science was conducted from the inception to June 2021. The PRISMA guidelines were used to improve the reporting of the review. The MINORS was used for quality assessment. From a total of 155 studies identified, only four articles were eligible for this study. The main advantages of biosensors reported were accuracy and capability to detect bacteria also in negative culture cases. Otherwise, due to the few studies and the low level of evidence of the papers included, it was impossible to find significant results. Therefore, further high-quality studies are required.
      Citation: Chemosensors
      PubDate: 2021-09-08
      DOI: 10.3390/chemosensors9090256
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 257: Controlled Growth of WO3 Pyramidal Thin
           Film via Hot-Filament Chemical Vapor Deposition: Electrochemical Detection
           of Ethylenediamine

    • Authors: Mohammad Imran, Eun-Bi Kim, Dong-Heui Kwak, Mohammad Shaheer Akhtar, Sadia Ameen
      First page: 257
      Abstract: In this work, the structural, optical, morphological, and sensing features of tungsten oxide (WO3) thin film deposited on a silicon substrate via hot-filament chemical vapor deposition (HFCVD) are described. The experimental characterization tools, such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet-visible (UV-Vis), and Fourier transform infra-red (FTIR) spectroscopies, etc., were used to determine the properties of WO3 NPys thin films. The grown WO3 thin film illustrated closely packed porous pyramidal nanostructures (NPys) of improved grain size properties. The diffraction analysis revealed (100) and (200) of WO3 phases, suggesting the classic monoclinic crystal WO3 structure. HFCVD grown WO3 NPys thin film was employed as electro-active electrode for detecting ethylenediamine in 10 mL of 0.1 M phosphate buffer solution (PBS) by varying the ethylenediamine concentrations from 10 μM to 200 μM at room temperature. With a detection of limit (LOD) of ~9.56 μM, and a quick reaction time (10 s), the constructed chemical sensor achieved a high sensitivity of ~161.33 μA μM−1 cm−2. The durability test displayed an excellent stability of electrochemical sensor by maintaining over 90% sensitivity after 4 weeks of operation. This work provides a strategy for a facile preparation of WO3 NPys thin film electrode for sensor applications.
      Citation: Chemosensors
      PubDate: 2021-09-08
      DOI: 10.3390/chemosensors9090257
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 258: A Bio-Fluorometric Acetone Gas Imaging
           System for the Dynamic Analysis of Lipid Metabolism in Human Breath

    • Authors: Takahiro Arakawa, Naoki Mizukoshi, Kenta Iitani, Koji Toma, Kohji Mitsubayashi
      First page: 258
      Abstract: We constructed an imaging system to measure the concentration of acetone gas by acetone reduction using secondary alcohol dehydrogenase (S-ADH). Reduced nicotinamide adenine dinucleotide (NADH) was used as an electron donor, and acetone was imaged by fluorescence detection of the decrease in the autofluorescence of NADH. In this system, S-ADH–immobilized membranes wetted with buffer solution containing NADH were placed in a dark box, and UV-LED excitation sheets and a high-sensitivity camera were installed on both sides of the optical axis to enable loading of acetone gas. A hydrophilic polytetrafluoroethylene (H-PTFE) membrane with low autofluorescence was used as a substrate, and honeycomb-like through-hole structures were fabricated using a CO2 laser device. After loading the enzyme membrane with acetone gas standards, a decrease in fluorescence intensity was observed in accordance with the concentration of acetone gas. The degree of decrease in fluorescence intensity was calculated using image analysis software; it was possible to quantify acetone gas at concentrations of 50–2000 ppb, a range that includes the exhaled breath concentration of acetone in healthy subjects. We applied this imaging system to measure the acetone gas in the air exhaled by a healthy individual during fasting.
      Citation: Chemosensors
      PubDate: 2021-09-09
      DOI: 10.3390/chemosensors9090258
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 259: Estimation of Enantiomeric Excess Based
           on Rapid Host–Guest Exchange

    • Authors: Jan Labuta, Shinsuke Ishihara, Daniel T. Payne, Kazuyoshi Takimoto, Hisako Sato, Lenka Hanyková, Katsuhiko Ariga, Jonathan P. Hill
      First page: 259
      Abstract: Chiral molecules possess enantiomers that have non-superimposable chemical structures but exhibit identical nuclear magnetic resonance (NMR) spectra. This feature prevents the use of NMR spectroscopic methods for the determination of enantiomeric excesses (ee) of chiral molecules, using simple mixtures of their enantiomers. Recently, however, it was reported that the addition of a symmetrical prochiral molecule (a reporter or host) into a solution of chiral analyte can lead to estimation of ee through interactions involving rapid exchange of the chiral analyte (guest) in the formed host–guest complex. This is due to the ee-dependent splitting of NMR resonances of the prochiral host molecule based on averaging the chemical shift non-equivalency caused by the presence of a chiral guest. The mechanism is not dependent on diastereomer formation, and 1:1 host–guest complexes can also show ee-dependent NMR peak splitting. Prochiral molecules capable of ee sensing using the NMR technique are now referred to as so-called prochiral solvating agents (pro-CSAs). pro-CSAs represent a family of reagents distinct from the commonly used NMR chiral derivatizing reagents (where chiral auxiliaries are used to derivatize enantiomers to diastereomers) or chiral solvating agents (where chiral auxiliaries interact in an asymmetric manner with analyte enantiomers). pro-CSA methods are unique since neither pro-CSA nor NMR contains chiral factors, making the technique neutral with respect to chirality. Here, we review our recent work on this matter involving several different nominally achiral receptor molecules whose unique guest binding properties and solution characteristics (especially with regard to NMR spectroscopy) allow for the estimation of ee in the corresponding chiral guests.
      Citation: Chemosensors
      PubDate: 2021-09-09
      DOI: 10.3390/chemosensors9090259
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 260: Recent Advances in Silicon FET Devices
           for Gas and Volatile Organic Compound Sensing

    • Authors: Anwesha Mukherjee, Yossi Rosenwaks
      First page: 260
      Abstract: Highly sensitive and selective gas and volatile organic compound (VOC) sensor platforms with fast response and recovery kinetics are in high demand for environmental health monitoring, industry, and medical diagnostics. Among the various categories of gas sensors studied to date, field effect transistors (FETs) have proved to be an extremely efficient platform due to their miniaturized form factor, high sensitivity, and ultra-low power consumption. Despite the advent of various kinds of new materials, silicon (Si) still enjoys the advantages of excellent and reproducible electronic properties and compatibility with complementary metal–oxide–semiconductor (CMOS) technologies for integrated multiplexing and signal processing. This review gives an overview of the recent developments in Si FETs for gas and VOC sensing. We categorised the Si FETs into Si nanowire (NW) FETs; planar Si FETs, in which the Si channel is either a part of the silicon on insulator (SOI) or the bulk Si, as in conventional FETs; and electrostatically formed nanowire (EFN) FETs. The review begins with a brief introduction, followed by a description of the Si NW FET gas and VOC sensors. A brief description of the various fabrication strategies of Si NWs and the several functionalisation methods to improve the sensing performances of Si NWs are also provided. Although Si NW FETs have excellent sensing properties, they are far from practical realisation due to the extensive fabrication procedures involved, along with other issues that are critically assessed briefly. Then, we describe planar Si FET sensors, which are much closer to real-world implementation. Their simpler device architecture combined with excellent sensing properties enable them as an efficient platform for gas sensing. The third category, the EFN FET sensors, proved to be another potential platform for gas sensing due to their intriguing properties, which are elaborated in detail. Finally, the challenges and future opportunities for gas sensing are addressed.
      Citation: Chemosensors
      PubDate: 2021-09-10
      DOI: 10.3390/chemosensors9090260
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 261: Odor Recognition of Thermal Decomposition
           Products of Electric Cables Using Odor Sensing Arrays

    • Authors: Yuanchang Liu, Shintaro Furuno, Sosuke Akagawa, Rui Yatabe, Takeshi Onodera, Nobuyuki Fujiwara, Hidekazu Takeda, Seiichi Uchida, Kiyoshi Toko
      First page: 261
      Abstract: An odor sensing system with chemosensitive resistors was used to identify the gases generated from overheated cables to prevent fire. Three different electric cables for a distribution cabinet were used. The cables had an insulation layer made of polyvinyl chloride (PVC) or cross-linked polyethylene (XLPE). The heat resistance of the cables was tested by differential thermal and thermogravimetric analyses. The thermal decomposition products of the cables were investigated by gas chromatography-mass spectrometry (GC-MS). For the odor sensing system, two types of 16-channel array were used to detect the generated gases. One contains high-polarity GC stationary phase materials and the other contains GC stationary phase materials of high to low polarity. The system could distinguish among three cable samples at 270 °C with an accuracy of about 75% through both arrays trained with machine learning. Furthermore, the system could achieve a recall rate of 90% and a precision rate of 70% when the abnormal temperature was set above the cables’ allowable conductor temperature at 130 °C. The odor sensing system could effectively detect the abnormal heating of the cables before the occurrence of fire. Therefore, it is helpful for fire prediction and detection systems in factories and substations.
      Citation: Chemosensors
      PubDate: 2021-09-10
      DOI: 10.3390/chemosensors9090261
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 262: A Comprehensive Review on Raman
           Spectroscopy Applications

    • Authors: Andrea Orlando, Filippo Franceschini, Cristian Muscas, Solomiya Pidkova, Mattia Bartoli, Massimo Rovere, Alberto Tagliaferro
      First page: 262
      Abstract: Raman spectroscopy is a very powerful tool for material analysis, allowing for exploring the properties of a wide range of different materials. Since its discovery, Raman spectroscopy has been used to investigate several features of materials such carbonaceous and inorganic properties, providing useful information on their phases, functions, and defects. Furthermore, techniques such as surface and tip enhanced Raman spectroscopy have extended the field of application of Raman analysis to biological and analytical fields. Additionally, the robustness and versatility of Raman instrumentations represent a promising solution for performing on-field analysis for a wide range of materials. Recognizing the many hot applications of Raman spectroscopy, we herein overview the main and more recent applications for the investigation of a wide range of materials, such as carbonaceous and biological materials. We also provide a brief but exhaustive theoretical background of Raman spectroscopy, also providing deep insight into the analytical achievements.
      Citation: Chemosensors
      PubDate: 2021-09-13
      DOI: 10.3390/chemosensors9090262
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 263: Chemical Sensing Properties of
           BaF2-Modified hBN Flakes towards Detection of Volatile Organic Compounds

    • Authors: Boitumelo J. Matsoso, Clara Garcia-Martinez, Thomas H. Mongwe, Bérangère Toury, José P. M. Serbena, Catherine Journet
      First page: 263
      Abstract: The application of BaF2-modified hBN flakes as rapid response and recovery as well as sensitive chemoresistive sensing device materials for detection of acetone and/or ethanol is presented in this study. Modification of the hBN flakes was achieved by using the modified polymer derived ceramics (PDCs) process through the use of 0–10 wt% BaF2 and 5 wt% Li3N. Upon exposure to individual acetone and ethanol vapours, room temperature sensing studies revealed high LoD values (−144–460 ppmacetone and −134–543 ppmethanol) with extremely compromised sensitivities of −0.042–0.72 × 10−2 ppm−1acetone and −0.045–0.19 × 10−2 ppm−1ethanol for the structurally improved 5–10 wt% BaF2-modified hBN flakes. Moreover, enhanced sensing for 0–2.5 wt% BaF2-modified hBN flakes, as shown by the low LoDs (−43–86 ppmacetone and −30–62 ppmethanol) and the high sensitivities (−1.8–2.1 × 10−2 ppm−1acetone and −1.5–1.6 × 10−2 ppm−1ethanol), was attributed to the presence of defects subsequently providing an abundance of adsorption sites. Overall, the study demonstrated the importance of structural properties of hBN flakes on their surface chemistry towards room temperature selective and sensitive detection of VOCs.
      Citation: Chemosensors
      PubDate: 2021-09-13
      DOI: 10.3390/chemosensors9090263
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 264: Optimization of a Handwriting Method by
           an Automated Ink Pen for Cost-Effective and Sustainable Sensors

    • Authors: Florin C. Loghin, José F. Salmerón, Paolo Lugli, Markus Becherer, Aniello Falco, Almudena Rivadeneyra
      First page: 264
      Abstract: In this work, we present a do-it-yourself (DIY) approach for the environmental-friendly fabrication of printed electronic devices and sensors. The setup consists only of an automated handwriting robot and pens filled with silver conductive inks. Here, we thoroughly studied the fabrication technique and different optimized parameters. The best-achieved results were 300 mΩ/sq as sheet resistance with a printing resolution of 200 µm. The optimized parameters were used to manufacture fully functional electronics devices: a capacitive sensor and a RFID tag, essential for the remote reading of the measurements. This technique for printed electronics represents an alternative for fast-prototyping and ultra-low-cost fabrication because of both the cheap equipment required and the minimal waste of materials, which is especially interesting for the development of cost-effective sensors.
      Citation: Chemosensors
      PubDate: 2021-09-16
      DOI: 10.3390/chemosensors9090264
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 265: Methodology of Selecting the Optimal
           Receptor to Create an Electrochemical Immunosensor for Equine Arteritis
           Virus Protein Detection

    • Authors: Mateusz Brodowski, Marcin Kowalski, Wioleta Białobrzeska, Katarzyna Pałka, Rafał Walkusz, Justyna Roguszczak, Tomasz Łęga, Marta Sosnowska, Małgorzata Biedulska, Joanna Kreczko Kurzawa, Ewelina Bięga, Joanna Wysocka, Marta Lisowska, Katarzyna Niedźwiedzka, Tomasz Lipiński, Sabina Żołędowska, Dawid Nidzworski
      First page: 265
      Abstract: The study reports a methodology of selecting the optimal receptor to create an electrochemical immunosensor for equine arteritis virus (EAV) protein detection. The detection was based on antigen recognition by antibodies immobilized on gold electrodes. Modification steps were controlled by electrochemical impedance spectroscopy and cyclic voltammetry measurements. In order to obtain the impedance immunosensor with the best parameters, seven different receptors complementary to equine arteritis virus protein were used. In order to make the selection, a rapid screening test was carried out to check the sensor’s response to blank, extremely low and high concentrations of target EAV protein, and negative sample: M protein from Streptococcus equi and glycoprotein G from Equid alphaherpesvirus 1. F6 10G receptor showed the best performance.
      Citation: Chemosensors
      PubDate: 2021-09-16
      DOI: 10.3390/chemosensors9090265
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 266: Optimization of Electronic Nose Sensor
           Array for Tea Aroma Detecting Based on Correlation Coefficient and Cluster

    • Authors: Jin Wang, Cheng Zhang, Meizhuo Chang, Wei He, Xiaohui Lu, Shaomei Fei, Guodong Lu
      First page: 266
      Abstract: The electronic nose system is widely used in tea aroma detecting, and the sensor array plays a fundamental role for obtaining good results. Here, a sensor array optimization (SAO) method based on correlation coefficient and cluster analysis (CA) is proposed. First, correlation coefficient and distinguishing performance value (DPV) are calculated to eliminate redundant sensors. Then, the sensor independence is obtained through cluster analysis and the number of sensors is confirmed. Finally, the optimized sensor array is constructed. According to the results of the proposed method, sensor array for green tea (LG), fried green tea (LF) and baked green tea (LB) are constructed, and validation experiments are carried out. The classification accuracy using methods of linear discriminant analysis (LDA) based on the average value (LDA-ave) combined with nearest-neighbor classifier (NNC) can almost reach 94.44~100%. When the proposed method is used to discriminate between various grades of West Lake Longjing tea, LF can show comparable performance to that of the German PEN2 electronic nose. The electronic nose SAO method proposed in this paper can effectively eliminate redundant sensors and improve the quality of original tea aroma data. With fewer sensors, the optimized sensor array contributes to the miniaturization and cost reduction of the electronic nose system.
      Citation: Chemosensors
      PubDate: 2021-09-17
      DOI: 10.3390/chemosensors9090266
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 267: New Organic Materials Based on Multitask
           2H-benzo[d]1,2,3-triazole Moiety

    • Authors: Iván Torres-Moya, José Ramón Carrillo, Ángel Díaz-Ortiz, Pilar Prieto
      First page: 267
      Abstract: Multifunctionality is a desirable aspect in materials science. Indeed, the development of multifunctional compounds is crucial for sustainable chemistry by saving resources and time. In this sense, 2H-benzo[d]1,2,3-triazole (BTz) is an excellent candidate with promising characteristics, including its ability to self-assemble; its acceptor character, which enables the synthesis of donor-acceptor structures; and its facile modulation using standard chemical methods. Thus, due to its interesting properties, it is possible to produce different derivatives with applications in different fields, as summarized in this article, with the correct substitution at the BTz cores. Optoelectronic or biomedical applications, amongst others, are highlighted.
      Citation: Chemosensors
      PubDate: 2021-09-17
      DOI: 10.3390/chemosensors9090267
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 268: Non-Local Patch Regression
           Algorithm-Enhanced Differential Photoacoustic Methodology for Highly
           Sensitive Trace Gas Detection

    • Authors: Le Zhang, Lixian Liu, Huiting Huan, Xukun Yin, Xueshi Zhang, Andreas Mandelis, Xiaopeng Shao
      First page: 268
      Abstract: A non-local patch regression (NLPR) denoising-enhanced differential broadband photoacoustic (PA) sensor was developed for the high-sensitive detection of multiple trace gases. Using the edge preservation index (EPI) and signal-to-noise ratio (SNR) as a dual-criterion, the fluctuation was dramatically suppressed while the spectral absorption peaks were maintained by the introduction of a NLPR algorithm. The feasibility of the broadband framework was verified by measuring the C2H2 in the background of ambient air. A normalized noise equivalent absorption (NNEA) coefficient of 6.13 × 10−11 cm−1·W·Hz−1/2 was obtained with a 30-mW globar source and a SNR improvement factor of 23. Furthermore, the simultaneous multiple-trace-gas detection capability was determined by measuring C2H2, H2O, and CO2. Following the guidance of single-component processing, the NLPR processed results showed higher EPI and SNR compared to the spectra denoised by the wavelet method and the non-local means algorithm. The experimentally determined SNRs of the C2H2, H2O, and CO2 spectra were improved by a factor of 20. The NNEA coefficient reached a value of 7.02 × 10−11 cm−1·W·Hz−1/2 for C2H2. The NLPR algorithm presented good performance in noise suppression and absorption peak fidelity, which offered a higher dynamic range and was demonstrated to be an effective approach for trace gas analysis.
      Citation: Chemosensors
      PubDate: 2021-09-18
      DOI: 10.3390/chemosensors9090268
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 269: A Preliminary Study for Tunable Optical
           Assessment of Exhaled Breath Ammonia Based on Ultrathin
           Tetrakis(4-sulfophenyl)porphine Nanoassembled Films

    • Authors: Sergiy Korposh, Seung-Woo Lee
      First page: 269
      Abstract: The detection of chemical substances excreted from the human body offers an attractive approach for non-invasive, early diagnostics of certain diseases. In this preliminary study, we proposed a susceptible optical sensor capable of quantitatively detecting ammonia from exhaled breath. The proposed sensor consists of nanoassembled ultrathin films composed of tetrakis(4-sulfophenyl)porphine (TSPP) and poly(diallyldimethylammonium chloride) (PDDA) deposited on quartz substrates using a layer-by-layer method. Measurement principles are based on the ammonia-induced absorbance changes at 489 (Soret band) and 702 nm (Q band), associated with the deprotonation of the J-aggregated TSPPs inside the film. Before exposure to breath, the PDDA/TSPP thin film was calibrated using known concentrations of ammonia gases with a projected detection limit of 102 ± 12 parts per billion (ppb). Calibrated sensor films were then exposed to human breath and urine samples to determine the ammonia concentration. Concentrations of exhaled ammonia are influenced significantly by the consumption of food or the amount of urea. Sensor response and maximum sensitivity, obtained from the absorbance changes induced by ammonia, were achieved by initial sensor exposure to HCl vapor. Previously reported procedures for the Helicobacter pylori (HELIC Ammonia Breath) test based on urea reaction with urease were reproduced using the proposed sensor. The observed behavior corresponded very well with the kinetics of the interactions between urea and urease, i.e., ammonia reached a maximum concentration approximately 5 min after the start of the reaction. A large-scale study involving 41 healthy volunteers in their 20s to 60s was successfully conducted to test the capabilities of the sensor to determine the concentration of exhaled ammonia. The concentration of ammonia for the healthy volunteers ranged between 0.3 and 1.5 ppm, with a mean value of ca. 520 ppb in the morning (before eating) and ca. 420 ppb in the afternoon (immediately after eating). These real-test mean values are meaningful when considered against the projected LOD.
      Citation: Chemosensors
      PubDate: 2021-09-18
      DOI: 10.3390/chemosensors9090269
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 270: Atomistic Descriptions of Gas-Surface
           Interactions on Tin Dioxide

    • Authors: Stefan Kucharski, Chris Blackman
      First page: 270
      Abstract: Historically, in gas sensing literature, the focus on “mechanisms” has been on oxygen species chemisorbed (ionosorbed) from the ambient atmosphere, but what these species actually represent and the location of the adsorption site on the surface of the solid are typically not well described. Recent advances in computational modelling and experimental surface science provide insights on the likely mechanism by which oxygen and other species interact with the surface of SnO2, providing insight into future directions for materials design and optimisation. This article reviews the proposed models of adsorption and reaction of oxygen on SnO2, including a summary of conventional evidence for oxygen ionosorption and recent operando spectroscopy studies of the atomistic interactions on the surface. The analysis is extended to include common target and interfering reducing gases, such as CO and H2, cross-interactions with H2O vapour, and NO2 as an example of an oxidising gas. We emphasise the importance of the surface oxygen vacancies as both the preferred adsorption site of many gases and in the self-doping mechanism of SnO2.
      Citation: Chemosensors
      PubDate: 2021-09-18
      DOI: 10.3390/chemosensors9090270
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 271: Label Free, Lateral Flow Prostaglandin E2
           Electrochemical Immunosensor for Urinary Tract Infection Diagnosis

    • Authors: Antra Ganguly, Tahmineh Ebrahimzadeh, Philippe E. Zimmern, Nicole J. De Nisco, Shalini Prasad
      First page: 271
      Abstract: A label-free, rapid, and easy-to-use lateral flow electrochemical biosensor was developed for urinary tract infection (UTI) diagnosis in resource challenged areas. The sensor operates in non-faradaic mode and utilizes Electrochemical Impedance Spectroscopy for quantification of Prostaglandin E2, a diagnostic and prognostic urinary biomarker for UTI and recurrent UTI. To achieve high sensitivity in low microliter volumes of neat, unprocessed urine, nanoconfinement of assay biomolecules was achieved by developing a three-electrode planar gold microelectrode system on top of a lateral flow nanoporous membrane. The sensor is capable of giving readouts within 5 min and has a wide dynamic range of 100–4000 pg/mL for urinary PGE2. The sensor is capable of discriminating between low and high levels of PGE2 and hence is capable of threshold classification of urine samples as UTI positive and UTI negative. The sensor through its immunological response (directly related to host immune response) is superior to the commercially available point-of-care UTI dipsticks which are qualitative, have poor specificity for UTI, and have high false-positive rates. The developed sensor shows promise for rapid, easy and cost-effective UTI diagnosis for both clinical and home-based settings. More accurate point-of-care UTI diagnosis will improve patient outcomes and allow for timely and appropriate prescription of antibiotics which can subsequently increase treatment success rates and reduce costs.
      Citation: Chemosensors
      PubDate: 2021-09-19
      DOI: 10.3390/chemosensors9090271
      Issue No: Vol. 9, No. 9 (2021)
  • Chemosensors, Vol. 9, Pages 197: Low-Dimensional Nanostructures Based on
           Cobalt Oxide (Co3O4) in Chemical-Gas Sensing

    • Authors: Gayan W. C. Kumarage, Elisabetta Comini
      First page: 197
      Abstract: Highly sensitive, stable, low production costs, together with easy maintenance and portability, sensors are ever most demanded nowadays for monitoring and quantification of hazardous chemicals/gases in the environment. The utilization of one dimensional (1D) metal oxide nano structured chemical/gas sensors for environmental monitoring is vastly investigated because of their superior surface to volume ratio, stability, and low production costs, to provide information on the presence of chemical species. Several outstanding attempts have been pursued investigating 1D nano structures of Co3O4 over the past decades as an active material for chemical analytes detection owing to its superior catalytic effect together with its excellent stability. This article reviews the state-of-the-art of growth and characterization of Co3O4 1D nano structures and their functional characterization as chemical/gas sensors. Moreover, fundamental concepts and characteristic features, that enhance the key performances of chemical/gas sensors, are discussed. Finally, challenges and prospective for growth and fabrication of 1D Co3O4 chemical/gas sensors are discussed.
      Citation: Chemosensors
      PubDate: 2021-07-29
      DOI: 10.3390/chemosensors9080197
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 198: One-Dimensional Nanomaterials in
           Resistive Gas Sensor: From Material Design to Application

    • Authors: Ze Wang, Lei Zhu, Shiyi Sun, Jianan Wang, Wei Yan
      First page: 198
      Abstract: With a series of widespread applications, resistive gas sensors are considered to be promising candidates for gas detection, benefiting from their small size, ease-of-fabrication, low power consumption and outstanding maintenance properties. One-dimensional (1-D) nanomaterials, which have large specific surface areas, abundant exposed active sites and high length-to-diameter ratios, enable fast charge transfers and gas-sensitive reactions. They can also significantly enhance the sensitivity and response speed of resistive gas sensors. The features and sensing mechanism of current resistive gas sensors and the potential advantages of 1-D nanomaterials in resistive gas sensors are firstly reviewed. This review systematically summarizes the design and optimization strategies of 1-D nanomaterials for high-performance resistive gas sensors, including doping, heterostructures and composites. Based on the monitoring requirements of various characteristic gases, the available applications of this type of gas sensors are also classified and reviewed in the three categories of environment, safety and health. The direction and priorities for the future development of resistive gas sensors are laid out.
      Citation: Chemosensors
      PubDate: 2021-07-30
      DOI: 10.3390/chemosensors9080198
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 199: Label-Free Electrochemical Test of
           Protease Interaction with a Peptide Substrate Modified Gold Electrode

    • Authors: Anna Wcisło, Izabela Małuch, Paweł Niedziałkowski, Tadeusz Ossowski, Adam Prahl
      First page: 199
      Abstract: Efficient deposition of biomolecules on the surface, maintaining their full activity and stability, is a most significant factor in biosensor construction. For this reason, more and more research is focused on the development of electrochemical biosensors that have the ability to electrically detect adsorbed molecules on electrode surface with high selectivity and sensitivity. The presented research aims to develop an efficient methodology that allows quantification of processes related to the evaluation of enzyme activity (proprotein convertase) using electrochemical methods. In this study we used impedance spectroscopy to investigate the immobilization of peptide substrate (Arg-Val-Arg-Arg) modified with 11-mercaptoundecanoic acid on the surface of gold electrode. Both the synthesis of the peptide substrate as well as the full electrochemical characteristics of the obtained electrode materials have been described. Experimental conditions, including concentration of peptide substrate immobilization, modification time, linker, and the presence of additional blocking groups have been optimized. The main advantages of the described method is that it makes it possible to observe the peptide substrate–enzyme interaction without the need to use fluorescent labels. This also allows observation of this interaction at a very low concentration. Both of these factors make this new technique competitive with the standard spectrofluorimetric method.
      Citation: Chemosensors
      PubDate: 2021-07-29
      DOI: 10.3390/chemosensors9080199
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 200: Multi-Sensor Characterization of
           Sparkling Wines Based on Data Fusion

    • Authors: Anais Izquierdo-Llopart, Javier Saurina
      First page: 200
      Abstract: This paper is focused on the assessment of a multi-sensor approach to improve the overall characterization of sparkling wines (cava wines). Multi-sensor, low-level data fusion can provide more comprehensive and more accurate vision of results compared with the study of simpler data sets from individual techniques. Data from different instrumental platforms were combined in an enriched matrix, integrating information from spectroscopic (UV/Vis and FTIR), chromatographic, and other techniques. Sparkling wines belonging to different classes, which differed in the grape varieties, coupages, and wine-making processes, were analyzed to determine organic acids (e.g., tartaric, lactic, malic, and acetic acids), pH, total acidity, polyphenols, total antioxidant capacity, ethanol, or reducing sugars. The resulting compositional values were treated chemometrically for a more efficient recovery of the underlaying information. In this regard, exploratory methods such as principal component analysis showed that phenolic compounds were dependent on varietal and blending issues while organic acids were more affected by fermentation features. The analysis of the multi-sensor data set provided a more comprehensive description of cavas according to grape classes, blends, and vinification processes. Hierarchical Cluster Analysis (HCA) allowed specific groups of samples to be distinguished, featuring malolactic fermentation and the chardonnay and red grape classes. Partial Least Squares-Discriminant Analysis (PLS-DA) also classified samples according to the type of grape varieties and fermentations. Bar charts and complementary statistic test were performed to better define the differences among the studied samples based on the most significant markers of each cava wine type. As a conclusion, catechin, gallic, gentisic, caftaric, caffeic, malic, and lactic acids were the most remarkable descriptors that contributed to their discrimination based on varietal, blending, and oenological factors.
      Citation: Chemosensors
      PubDate: 2021-07-30
      DOI: 10.3390/chemosensors9080200
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 201: Ionogels Based on a Single Ionic Liquid
           for Electronic Nose Application

    • Authors: Wellington B. Gonçalves, Evelyn P. Cervantes, Ana C. C. S. Pádua, Gonçalo Santos, Susana I. C. J. Palma, Rosamaria W. C. Li, Ana C. A. Roque, Jonas Gruber
      First page: 201
      Abstract: Ionogel are versatile materials, as they present the electrical properties of ionic liquids and also dimensional stability, since they are trapped in a solid matrix, allowing application in electronic devices such as gas sensors and electronic noses. In this work, ionogels were designed to act as a sensitive layer for the detection of volatiles in a custom-made electronic nose. Ionogels composed of gelatin and a single imidazolium ionic liquid were doped with bare and functionalized iron oxide nanoparticles, producing ionogels with adjustable target selectivity. After exposing an array of four ionogels to 12 distinct volatile organic compounds, the collected signals were analyzed by principal component analysis (PCA) and by several supervised classification methods, in order to assess the ability of the electronic nose to distinguish different volatiles, which showed accuracy above 98%.
      Citation: Chemosensors
      PubDate: 2021-07-30
      DOI: 10.3390/chemosensors9080201
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 202: Carbon Quantum Dots from Lemon Waste
           Enable Communication among Biodevices

    • Authors: Federico Calì, Valentina Cantaro, Luca Fichera, Roberta Ruffino, Giuseppe Trusso Sfrazzetto, Giovanni Li-Destri, Nunzio Tuccitto
      First page: 202
      Abstract: A bioinspired method of communication among biodevices based on fluorescent nanoparticles is herein presented. This approach does not use electromagnetic waves but rather the exchange of chemical systems—a method known as molecular communication. The example outlined was based on the fluorescence properties of carbon dots and follows a circular economy approach as the method involves preparation from the juice of lemon waste. The synthesis is herein presented, and the fluorescence properties and diffusion coefficient are evaluated. The application of carbon dots to molecular communication was studied from a theoretical point of view by numerically solving the differential equation that governs the phenomenon. The theoretical results were used to develop a prototype molecular communication platform that enables the communication of simple messages via aqueous fluids to a fluorescence-detecting biodevice receiver.
      Citation: Chemosensors
      PubDate: 2021-07-30
      DOI: 10.3390/chemosensors9080202
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 203: Selective Determination of Hydrogen
           Sulfide Using SnO2–Ag Sensor Working in Non-Stationary Temperature

    • Authors: Alexey V. Shaposhnik, Pavel V. Moskalev, Alexey A. Zviagin, Margarita V. Duykova, Stanislav V. Ryabtsev, Dina A. A. Ghareeb, Alexey A. Vasiliev
      First page: 203
      Abstract: The application of a non-stationary regime of temperature modulation in metal oxide semiconductor sensor based on SnO2–Ag leads not only to a strongly increased sensor response, but also to a considerably improved sensor selectivity toward hydrogen sulfide. Selectivity with respect to other reducing gases (CO, NH3, H2) is about five orders of magnitude, enabling a correct selective determination of H2S in the presence of interfering gas components.
      Citation: Chemosensors
      PubDate: 2021-08-02
      DOI: 10.3390/chemosensors9080203
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 204: Recognition and Sensing of Chiral Organic
           Molecules by Chiral Porphyrinoids: A Review

    • Authors: Gabriele Travagliante, Massimiliano Gaeta, Roberto Purrello, Alessandro D’Urso
      First page: 204
      Abstract: Porphyrinoids are extremely attractive for their electronic, optical, and coordination properties as well as for their versatile substitution at meso/β-positions. All these features allow porphyrinoids to behave as chiroptical hosts for chiral recognition by means of non-covalent interactions towards chiral guests. Over the years, chiral discrimination of chiral molecules such as amino acids, alcohols, amines, hydroxy-carboxylic acids, etc. has aroused the interest of the scientific community. Hence, this review aims to report on the progress to date by illustrating some relevant research regarding the chiral recognition of a multitude of chiral organic guests through several chiral mono- and bis-porphyrins via different spectroscopic techniques.
      Citation: Chemosensors
      PubDate: 2021-08-03
      DOI: 10.3390/chemosensors9080204
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 205: Novel Prostate Cancer Biomarkers:
           Aetiology, Clinical Performance and Sensing Applications

    • Authors: Tomas Bertok, Aniko Bertokova, Stefania Hroncekova, Erika Chocholova, Natalia Svecova, Lenka Lorencova, Peter Kasak, Jan Tkac
      First page: 205
      Abstract: The review initially provides a short introduction to prostate cancer (PCa) incidence, mortality, and diagnostics. Next, the need for novel biomarkers for PCa diagnostics is briefly discussed. The core of the review provides details about PCa aetiology, alternative biomarkers available for PCa diagnostics besides prostate specific antigen and their biosensing. In particular, low molecular mass biomolecules (ions and metabolites) and high molecular mass biomolecules (proteins, RNA, DNA, glycoproteins, enzymes) are discussed, along with clinical performance parameters.
      Citation: Chemosensors
      PubDate: 2021-08-04
      DOI: 10.3390/chemosensors9080205
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 206: Comparison of Optical Ammonia-Sensing
           Properties of Conducting Polymer Complexes with Polysulfonic Acids

    • Authors: Oxana Gribkova, Varvara Kabanova, Vladimir Tverskoy, Alexander Nekrasov
      First page: 206
      Abstract: Thin films of conducting polymer complexes with polysulfonic acids of various structures were electrochemically deposited onto transparent FTO electrodes. The behavior of the polymer-based optical ammonia vapor sensors in response to various concentrations of ammonia vapors, ranging from 5 to 135 ppm, was investigated, including the response time and response amplitude. It was found that the nature of the conducting polymers (poly (3,4-ethylenedioxythiophene), polypyrrole, polyaniline), as well as the structure of the polyacids, affected the sensing performance of the obtained complexes.
      Citation: Chemosensors
      PubDate: 2021-08-04
      DOI: 10.3390/chemosensors9080206
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 207: MEMS-Based Cantilever Sensor for
           Simultaneous Measurement of Mass and Magnetic Moment of Magnetic Particles

    • Authors: Wilson Ombati Nyang’au, Tamara Kahmann, Thilo Viereck, Erwin Peiner
      First page: 207
      Abstract: This study presents a measurement approach suitable for the simultaneous determination of both the mass mp and magnetic moment µp of magnetic particles deposited on a micro electro mechanical system (MEMS) resonant cantilever balance, which is operated in parallel to an external magnetic field-induced force gradient F′(z). Magnetic induction B(z) and its second spatial derivative δ2B/δz2 is realized, beforehand, through the finite element method magnetics (FEMM) simulation with a pair of neodymium permanent magnets configured in a face-to-face arrangement. Typically, the magnets are mounted in a magnet holder assembly designed and fabricated in-house. The resulting F′ lowers the calibrated intrinsic stiffness k0 of the cantilever to k0-F′, which can, thus, be obtained from a measured resonance frequency shift of the cantilever. The magnetic moment µp per deposited particle is determined by dividing F′ by δ2B/δz2 and the number of the attached monodisperse particles given by the mass-induced frequency shift of the cantilever. For the plain iron oxide particles (250 nm) and the magnetic polystyrene particles (2 µm), we yield µp of 0.8 to 1.5 fA m2 and 11 to 19 fA m2 compared to 2 fA m2 and 33 fA m2 nominal values, respectively.
      Citation: Chemosensors
      PubDate: 2021-08-04
      DOI: 10.3390/chemosensors9080207
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 208: One-Class Drift Compensation for an
           Electronic Nose

    • Authors: Xiuxiu Zhu, Tao Liu, Jianjun Chen, Jianhua Cao, Hongjin Wang
      First page: 208
      Abstract: Drift compensation is an important issue in an electronic nose (E-nose) that hinders the development of E-nose’s model robustness and recognition stability. The model-based drift compensation is a typical and popular countermeasure solving the drift problem. However, traditional model-based drift compensation methods have faced “label dilemma” owing to high costs of obtaining kinds of prepared drift-calibration samples. In this study, we have proposed a calibration model for classification utilizing a single category of drift correction samples for more convenient and feasible operations. We constructed a multi-task learning model to achieve a calibrated classifier considering several demands. Accordingly, an associated solution process has been presented to gain a closed-form classifier representation. Moreover, two E-nose drift datasets have been introduced for method evaluation. From the experimental results, the proposed methodology reaches the highest recognition rate in most cases. On the other hand, the proposed methodology demonstrates excellent and steady performance in a wide range of adjustable parameters. Generally, the proposed method can conduct drift compensation with limited one-class calibration samples, accessing the top accuracy among all presented reference methods. It is a new choice for E-nose to counteract drift effect under cost-sensitive conditions.
      Citation: Chemosensors
      PubDate: 2021-08-04
      DOI: 10.3390/chemosensors9080208
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 209: MOS Sensors Array for the Discrimination
           of Lung Cancer and At-Risk Subjects with Exhaled Breath Analysis

    • Authors: Davide Marzorati, Luca Mainardi, Giulia Sedda, Roberto Gasparri, Lorenzo Spaggiari, Pietro Cerveri
      First page: 209
      Abstract: Lung cancer is characterized by a tremendously high mortality rate and a low 5-year survival rate when diagnosed at a late stage. Early diagnosis of lung cancer drastically reduces its mortality rate and improves survival. Exhaled breath analysis could offer a tool to clinicians to improve the ability to detect lung cancer at an early stage, thus leading to a reduction in the associated survival rate. In this paper, we present an electronic nose for the automatic analysis of exhaled breath. A total of five a-specific gas sensors were embedded in the electronic nose, making it sensitive to different volatile organic compounds (VOCs) contained in exhaled breath. Nine features were extracted from each gas sensor response to exhaled breath, identifying the subject breathprint. We tested the electronic nose on a cohort of 80 subjects, equally split between lung cancer and at-risk control subjects. Including gas sensor features and clinical features in a classification model, recall, precision, and accuracy of 78%, 80%, and 77% were reached using a fourfold cross-validation approach. The addition of other a-specific gas sensors, or of sensors specific to certain compounds, could improve the classification accuracy, therefore allowing for the development of a clinical tool to be integrated in the clinical pipeline for exhaled breath analysis and lung cancer early diagnosis.
      Citation: Chemosensors
      PubDate: 2021-08-05
      DOI: 10.3390/chemosensors9080209
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 210: Development of Neutral Red as a pH/pCO2
           Luminescent Sensor for Biological Systems

    • Authors: Megan N. Ericson, Sindhu K. Shankar, Laya M. Chahine, Mohammad A. Omary, Ione Hunt von Herbing, Sreekar B. Marpu
      First page: 210
      Abstract: Neutral Red (NR), a eurhodin dye, is often used for staining living cells, but we demonstrated for the first time that NR can also serve as a CO2 sensor, because of NR’s unique optical properties, which change with dissolved carbon dioxide (dCO2) concentrations. In the present study, optical sensitivity of NR was quantified as a function of changes in absorption and emission spectra to dCO2 in a pH 7.3 buffer medium at eight dCO2 concentrations. NR exhibited a response time of two minutes for equilibration in pure N2 to 100% CO2 with an ~200% percent change (%∆) in emission intensity and >400%∆ in absorbance, with full reversibility. Important to its application to biological systems, NR exhibited zero sensitivity to dissolved oxygen, which has routinely caused interference for CO2 measurements. NR exhibited pH sensitive emission and excitation energies with dual excitation wavelengths at 455 nm and 540 nm, and a single emission at 640 nm. The CO2 sensing properties of NR were benchmarked by a comparison to pyranine (8-hydroxypyrene-1, 3,6-trisulfonic acid trisodium salt) (HPTS). Future studies will evaluate the feasibility of NR as an intracellular in vivo pCO2 sensor in aquatic organisms critically impacted by increasing global CO2 levels.
      Citation: Chemosensors
      PubDate: 2021-08-05
      DOI: 10.3390/chemosensors9080210
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 211: Current Progress of Magnetoresistance

    • Authors: Songlin Yang, Jin Zhang
      First page: 211
      Abstract: Magnetoresistance (MR) is the variation of a material’s resistivity under the presence of external magnetic fields. Reading heads in hard disk drives (HDDs) are the most common applications of MR sensors. Since the discovery of giant magnetoresistance (GMR) in the 1980s and the application of GMR reading heads in the 1990s, the MR sensors lead to the rapid developments of the HDDs’ storage capacity. Nowadays, MR sensors are employed in magnetic storage, position sensing, current sensing, non-destructive monitoring, and biomedical sensing systems. MR sensors are used to transfer the variation of the target magnetic fields to other signals such as resistance change. This review illustrates the progress of developing nanoconstructed MR materials/structures. Meanwhile, it offers an overview of current trends regarding the applications of MR sensors. In addition, the challenges in designing/developing MR sensors with enhanced performance and cost-efficiency are discussed in this review.
      Citation: Chemosensors
      PubDate: 2021-08-05
      DOI: 10.3390/chemosensors9080211
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 212: Functionalization Strategies of PEDOT and
           PEDOT:PSS Films for Organic Bioelectronics Applications

    • Authors: Gonzalo E. Fenoy, Omar Azzaroni, Wolfgang Knoll, Waldemar A. Marmisollé
      First page: 212
      Abstract: Organic bioelectronics involves the connection of organic semiconductors with living organisms, organs, tissues, cells, membranes, proteins, and even small molecules. In recent years, this field has received great interest due to the development of all kinds of devices architectures, enabling the detection of several relevant biomarkers, the stimulation and sensing of cells and tissues, and the recording of electrophysiological signals, among others. In this review, we discuss recent functionalization approaches for PEDOT and PEDOT:PSS films with the aim of integrating biomolecules for the fabrication of bioelectronics platforms. As the choice of the strategy is determined by the conducting polymer synthesis method, initially PEDOT and PEDOT:PSS films preparation methods are presented. Later, a wide variety of PEDOT functionalization approaches are discussed, together with bioconjugation techniques to develop efficient organic-biological interfaces. Finally, and by making use of these approaches, the fabrication of different platforms towards organic bioelectronics devices is reviewed.
      Citation: Chemosensors
      PubDate: 2021-08-06
      DOI: 10.3390/chemosensors9080212
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 213: Evaluating the Effect of a Brewery
           By-Product as Feed Supplementation on the Quality of Eggs by Means of a
           Human Panel and E-Tongue and E-Nose Analysis

    • Authors: Juan Pablo Aguinaga Bósquez, Zoltan Kovacs, Zoltán Gillay, György Bázár, Csaba Palkó, Hajnalka Hingyi, Éva Csavajda, Márta Üveges, Zsuzsanna Jókainé Szatura, Iuliana Diana Barbulescu, Mihaela Begea, Tamás Tóth
      First page: 213
      Abstract: The objective of our research was to evaluate the possible alteration of the organoleptic properties of eggs produced by hens (Lohmann Brown-Classic) fed with diets containing different doses of an industrial by-product enriched with organic zinc (Zincoppyeast, ZP): Control 0%, ZP 2.5%, and ZP 5.0%. Eggs were collected after 30 days (batch 1) and 60 days (batch 2) of feeding with the experimental diets and subjected to chemical, microbiological, human sensory, e-nose, and e-tongue analyses. There was no significant difference among the microbiological status of eggs of the three groups, but there were significant differences (p < 0.05) in the fat (9.5% vs. 9.3%) and protein contents (12.7% vs. 13.4%) of the Control and ZP 5.0% groups, respectively. Human sensory analysis showed no clear change in the organoleptic characteristics of the eggs. Using linear discriminant analysis (LDA), the e-tongue could recognize the three groups of eggs in batch 1 and batch 2 with 95.9% and 100% accuracy and had a prediction accuracy of 64.8% and 56.2%, respectively. When the eggs were incubating at 50 °C or 80 °C before the e-nose analysis, the groups of eggs could be recognized with 98.0% and 82.7% accuracy, and predicted with 68.5% and 62.2% accuracy, respectively, using principal component analysis-based discriminant analysis (PCA–DA). The aroma compounds and respective sensory descriptors showing changes among the different groups of eggs (batch, storage, and feeding) were identified based on the e-nose analysis. The supplementation of laying hens’ feed with the investigated industrial by-product can be applied without any substantial effect on egg quality, which can, however, be detected with advanced analytical methods.
      Citation: Chemosensors
      PubDate: 2021-08-06
      DOI: 10.3390/chemosensors9080213
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 214: On the Radiolytic Stability of
           Potentiometric Sensors with Plasticized Polymeric Membranes

    • Authors: Julia Savosina, Marina Agafonova-Moroz, Maria Khaydukova, Andrey Legin, Vasiliy Babain, Peter Tolstoy, Dmitry Kirsanov
      First page: 214
      Abstract: There is not much known on the stability of plasticized polymeric sensor membranes against ionizing radiation. While recent studies have indicated the applicability of potentiometric sensors with such membranes for quantification of actinides and lanthanides in spent nuclear fuel reprocessing solutions, the real industrial application of such sensors will require their stability in ionizing radiation fields. The present study explores this problem and evaluates the stability of potentiometric sensitivity towards lanthanides and actinides for a variety of plasticized polymeric membranes based on different neutral ligands. We demonstrate that most of the studied sensor compositions retain their sensitivity up to 50–100 kGy of the absorbed gamma radiation dose. The higher doses lead to the gradual loss of sensitivity due to the radiolysis of ligands and a polymer membrane matrix as confirmed by electrochemical impedance and nuclear magnetic resonance studies.
      Citation: Chemosensors
      PubDate: 2021-08-08
      DOI: 10.3390/chemosensors9080214
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 215: Perovskite@Graphene Nanohybrids for
           Breath Analysis: A Proof-of-Concept

    • Authors: Juan Casanova-Chafer, Rocio Garcia-Aboal, Pedro Atienzar, Carla Bittencourt, Eduard Llobet
      First page: 215
      Abstract: Nanohybrids comprising graphene loaded with perovskite nanocrystals have been demonstrated as a potential option for sensing applications. Specifically, their combination presents an interesting synergistic effect owing to greater sensitivity when bare graphene is decorated with perovskites. In addition, since the main drawback of perovskites is their instability towards ambient moisture, the hydrophobic properties of graphene can protect them, enabling their use for ambient monitoring, as previously reported. However not limited to this, the present work provides a proof-of-concept to likewise employ them in a potential application as breath analysis for the detection of health-related biomarkers. There is a growing demand for sensitive, non-invasive, miniaturized, and inexpensive devices able to detect specific gas molecules in human breath. Sensors gathering these requirements may be employed as a screening tool for reliable and fast detection of potential health issues. Moreover, perovskite@graphene nanohybrids present additional properties highly desirable as the capability to be operated at room temperature (i.e., reduced power consumption), reversible interaction with gases (i.e., reusability), and long-term stability. Within this perspective, the combination of both nanomaterials, perovskite nanocrystals and graphene, possibly includes the main requirements needed, being a promising option to be employed in the next generation of sensing devices.
      Citation: Chemosensors
      PubDate: 2021-08-08
      DOI: 10.3390/chemosensors9080215
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 216: 2,12-Diaza[6]helicene: An Efficient
           Non-Conventional Stereogenic Scaffold for Enantioselective Electrochemical

    • Authors: Francesca Fontana, Benedetta Bertolotti, Sara Grecchi, Patrizia Romana Mussini, Laura Micheli, Roberto Cirilli, Matteo Tommasini, Simona Rizzo
      First page: 216
      Abstract: The new configurationally stable, unsymmetrical 2,12-diaza[6]helicene was synthesized as a racemate and the enantiomers were separated in an enantiopure state by semi-preparative HPLC on chiral stationary phase. Under selected alkylation conditions it was possible to obtain both the enantiopure 2-N-mono- and di-N-ethyl quaternary iodides. Metathesis with bis(trifluoromethanesulfonyl)imide anion gave low-melting salts which were tested as inherently chiral additives to achiral ionic liquids for the electrochemical enantiodiscrimination of chiral organic probes in voltammetric experiments. Remarkable differences in the oxidation potentials of the enantiomers of two probes, a chiral ferrocenyl amine and an aminoacid, were achieved; the differences increase with increasing additive concentration and number of alkylated nitrogen atoms.
      Citation: Chemosensors
      PubDate: 2021-08-10
      DOI: 10.3390/chemosensors9080216
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 217: Fluorescence Enhancement via Dual
           Coupling of Dye Molecules with Silver Nanostructures

    • Authors: Vien Thi Tran, Heongkyu Ju
      First page: 217
      Abstract: We demonstrate the enhancement of fluorescence emitted from dye molecules coupled with two surface plasmons, i.e., silver nanoparticles (AgNPs)-induced localized surface plasmons (LSP) and thin silver (Ag) film supported surface plasmons. Excitation light is illuminated to a SiO2 layer that contains both rhodamine 110 molecules and AgNPs. AgNPs enhances excitation rates of dye molecules in their close proximity due to LSP-induced enhancement of local electromagnetic fields at dye excitation wavelengths. Moreover, the SiO2 layer on one surface of which a 50 nm-thick Ag film is coated for metal cladding (air on the other surface), acts as a waveguide core at the dye emission wavelengths. The Ag film induces the surface plasmons which couple with the waveguide modes, resulting in a waveguide-modulated version of surface plasmon coupled emission (SPCE) for different SiO2 thicknesses in a reverse Kretschmann configuration. We find that varying the SiO2 thickness modulates the fluorescent signal of SPCE, its modulation behavior being in agreement with the theoretical simulation of thickness dependent properties of the coupled plasmon waveguide resonance. This enables optimization engineering of the waveguide structure for enhancement of fluorescent signals. The combination of LSP enhanced dye excitation and the waveguide-modulated version of SPCE may offer chances of enhancing fluorescent signals for a highly sensitive fluorescent assay of biomedical and chemical substances.
      Citation: Chemosensors
      PubDate: 2021-08-10
      DOI: 10.3390/chemosensors9080217
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 218: Bovine Serum Albumin Protein Detection by
           a Removable SPR Chip Combined with a Specific MIP Receptor

    • Authors: Francesco Arcadio, Luigi Zeni, Chiara Perri, Girolamo D’Agostino, Giudo Chiaretti, Giovanni Porto, Aldo Minardo, Nunzio Cennamo
      First page: 218
      Abstract: Nowadays, the development of simple, fast, and low-cost selective sensors to detect substances of interest is of great importance in several application fields. Among this kind of sensors, those based on surface plasmon resonance (SPR) represent a promising category, since they are highly sensitive, versatile, and label-free. In this work, an SPR probe, based on a poly(methyl methacrylate) (PMMA) slab waveguide covered by a gold nanofilm, combined with a specific molecularly imprinted polymer (MIP) receptor for bovine serum albumin (BSA) protein, has been realized and experimentally characterized. The obtained experimental results have shown a limit of detection (LOD) equal to about 8.5 × 10−9 M. This value is smaller than the one achieved by another SPR probe, based on a D-shaped plastic optical fiber (POF), functionalized with the same MIP receptor; more specifically, the obtained LOD was reduced by about three orders of magnitude with respect to the POF configuration. Moreover, concerning the D-shaped POF configuration, no manufacturing process is present in the proposed sensor configuration. In addition, fibers are used only to connect the simple sensor chip with a light source and a detector, promoting a bio-chemical sensing approach based on disposable, low-cost, and removable chips.
      Citation: Chemosensors
      PubDate: 2021-08-11
      DOI: 10.3390/chemosensors9080218
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 219: UV-Light-Driven Enhancement of
           Peroxidase-Like Activity of Mg-Aminoclay-Based Fe3O4/TiO2 Hybrids for
           Colorimetric Detection of Phenolic Compounds

    • Authors: Yoon Jung Jang, Vu Khac Hoang Bui, Phuong Thy Nguyen, Young-Chul Lee, Moon Il Kim
      First page: 219
      Abstract: Light-activated nanozymes possess several advantages, such as light-mediated activity regulation, utilization of molecular oxygen as a green oxidant, and highly enhanced activity; however, the types of light-activated nanozymes are still limited. In this study, we found that Mg aminoclay-based Fe3O4/TiO2 hybrids (MgAC-Fe3O4/TiO2) exhibited peroxidase-like catalytic activity to catalyze the oxidation of the peroxidase substrate 2,2′-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS) in the presence of H2O2, which was significantly enhanced under ultraviolet (UV)-light irradiation. Compared with MgAC-Fe3O4 and MgAC-TiO2, MgAC-Fe3O4/TiO2 showed around three-fold enhancement in the absorption intensity corresponding to the oxidized ABTS under UV-light irradiation, presumably due to the synergistic effect between Fe3O4 and TiO2, thereby facilitating photocatalytic electron transfer during the catalytic action. In addition, the MgAC-Fe3O4/TiO2 showed vivid stability enhancement in wide range of pH and temperature values compared with natural peroxidase. The UV-light-driven MgAC-Fe3O4/TiO2-based system was successfully applied for the colorimetric detection of phenolic compounds, including pyrocatechol and resorcinol, in a dynamic linear range of 0.15–1.30 mg/mL with a limit of detection as low as 0.1 mg/mL. Further, the system could successfully determine the phenolic compounds in spiked tap water, and thus, it can be used for practical applications. We believe that the UV-light-driven enhancement in the peroxidase-like catalytic performances highlights the potential of MgAC-Fe3O4/TiO2 for detecting phenolic compounds as well as other clinically and environmentally important substances.
      Citation: Chemosensors
      PubDate: 2021-08-11
      DOI: 10.3390/chemosensors9080219
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 220: Theoretical and Experimental Research on
           Ammonia Sensing Properties of Sulfur-Doped Graphene Oxide

    • Authors: Yao Yu, Zhijia Liao, Fanli Meng, Zhenyu Yuan
      First page: 220
      Abstract: In this paper, gas sensing characteristics of sulfur-doped graphene oxide (S-GO) are firstly presented. The results of the sensing test revealed that, at room temperature (20 °C), S-GO has the optimal sensitivity to NH3. The S-GO gas sensor has a relatively short response and recovery time for the NH3 detection. Further, the sensing limit of ammonia at room temperature is 0.5 ppm. Theoretical models of graphene and S-doped graphene are established, and electrical properties of the graphene and S-doped graphene are calculated. The enhanced sensing performance was ascribed to the electrical properties’ improvement after the graphene was S-doped.
      Citation: Chemosensors
      PubDate: 2021-08-11
      DOI: 10.3390/chemosensors9080220
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 221: Ultrathin Leaf-Shaped CuO Nanosheets

    • Authors: Ahmad Umar, Hassan Algadi, Rajesh Kumar, Mohammad Shaheer Akhtar, Ahmed A. Ibrahim, Hasan Albargi, Mohsen A. M. Alhamami, Turki Alsuwian, Wen Zeng
      First page: 221
      Abstract: Herein, a simple, economical and low temperature synthesis of leaf-shaped CuO nanosheets is reported. As-synthesized CuO was examined through different techniques including field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), fourier transform infrared spectroscopic (FTIR) and Raman spectroscopy to ascertain the purity, crystal phase, morphology, vibrational, optical and diffraction features. FESEM and TEM images revealed a thin leaf-like morphology for CuO nanosheets. An interplanar distance of ~0.25 nm corresponding to the (110) diffraction plane of the monoclinic phase of the CuO was revealed from the HRTEM images XRD analysis indicated a monoclinic tenorite crystalline phase of the synthesized CuO nanosheets. The average crystallite size for leaf-shaped CuO nanosheets was found to be 14.28 nm. Furthermore, a chemo-resistive-type gas sensor based on leaf-shaped CuO nanosheets was fabricated to effectively and selectively detect H2S gas. The fabricated sensor showed maximum gas response at an optimized temperature of 300 °C towards 200 ppm H2S gas. The corresponding response and recovery times were 97 s and 100 s, respectively. The leaf-shaped CuO nanosheets-based gas sensor also exhibited excellent selectivity towards H2S gas as compared to other analyte gases including NH3, CH3OH, CH3CH2OH, CO and H2. Finally, we have proposed a gas sensing mechanism based upon the formation of chemo-resistive CuO nanosheets.
      Citation: Chemosensors
      PubDate: 2021-08-11
      DOI: 10.3390/chemosensors9080221
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 222: Aptamer-Sensitized Nanoribbon Biosensor
           for Ovarian Cancer Marker Detection in Plasma

    • Authors: Yuri D. Ivanov, Kristina A. Malsagova, Tatyana O. Pleshakova, Rafael A. Galiullin, Andrey F. Kozlov, Ivan D. Shumov, Vladimir P. Popov, Svetlana I. Kapustina, Irina A. Ivanova, Arina I. Isaeva, Fedor V. Tikhonenko, Nikolay E. Kushlinskii, Alexander A. Alferov, Vadim Yu. Tatur, Vadim S. Ziborov, Oleg F. Petrov, Alexander V. Glukhov, Alexander I. Archakov
      First page: 222
      Abstract: The detection of CA 125 protein in buffer solution with a silicon-on-insulator (SOI)-based nanoribbon (NR) biosensor was experimentally demonstrated. In the biosensor, sensor chips, bearing an array of 12 nanoribbons (NRs) with n-type conductance, were employed. In the course of the analysis with the NR biosensor, the target protein was biospecifically captured onto the surface of the NRs, which was sensitized with covalently immobilized aptamers against CA 125. Atomic force microscopy (AFM) and mass spectrometry (MS) were employed in order to confirm the formation of the probe–target complexes on the NR surface. Via AFM and MS, the formation of aptamer–antigen complexes on the surface of SOI substrates with covalently immobilized aptamers against CA 125 was revealed, thus confirming the efficient immobilization of the aptamers onto the SOI surface. The biosensor signal, resulting from the biospecific interaction between CA 125 and the NR-immobilized aptamer probes, was shown to increase with an increase in the target protein concentration. The minimum detectable CA 125 concentration was as low as 1.5 × 10−17 M. Moreover, with the biosensor proposed herein, the detection of CA 125 in the plasma of ovarian cancer patients was demonstrated.
      Citation: Chemosensors
      PubDate: 2021-08-13
      DOI: 10.3390/chemosensors9080222
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 223: Selective Enhancement of SERS Spectral
           Bands of Salicylic Acid Adsorbate on 2D Ti3C2Tx-Based MXene Film

    • Authors: Sonata Adomavičiūtė-Grabusovė, Simonas Ramanavičius, Anton Popov, Valdas Šablinskas, Oleksiy Gogotsi, Arūnas Ramanavičius
      First page: 223
      Abstract: In this research, we have demonstrated that 2D Ti3C2Xn-based MXene (MXene) films are suitable for the design of surface-enhanced Raman spectroscopy (SERS)-based sensors. The enhanced SERS signal was observed for a salicylic acid molecule on Ti3C2Tx-based MXene film. Confirmation of the adsorption of the salicylic acid molecule and the formation of a salicylic acid–MXene complex were determined by experimental SERS-based spectral observations such as greatly enhanced out-of-plane bending modes of salicylic acid at 896 cm−1 and a band doublet at 681 cm−1 and 654 cm−1. Additionally, some other spectral features indicate the adsorption of salicylic acid on the MXene surface, namely, a redshift of vibrational modes and the disappearance of the carboxyl deformation spectral band at 771 cm−1. The determined enhancement factor indicates the value that can be expected for the chemical enhancement mechanism in SERS of 220 for out-of-plane vibrational modes. Theoretical modeling based on density functional theory (DFT) calculations using B3LYP/6311G++ functional were performed to assess the formation of the salicylic acid/MXene complex. Based on the calculations, salicylic acid displays affinity of forming a chemical bond with titanium atom of Ti3C2(OH)2 crystal via oxygen atom in hydroxyl group of salicylic acid. The electron density redistribution of the salicylic acid–MXene complex leads to a charge transfer effect with 2.2 eV (428 nm) and 2.9 eV (564 nm) excitations. The experimentally evaluated enhancement factor can vary from 220 to 60 when different excitation wavelengths are applied.
      Citation: Chemosensors
      PubDate: 2021-08-13
      DOI: 10.3390/chemosensors9080223
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 224: Gas Chromatography Multiresidue Method
           for Enantiomeric Fraction Determination of Psychoactive Substances in
           Effluents and River Surface Waters

    • Authors: Ivan Langa, Maria Elizabeth Tiritan, Diana Silva, Cláudia Ribeiro
      First page: 224
      Abstract: Determination of psychoactive substances (PAS) and/or their metabolites in surface waters is crucial for environmental risk assessment, and disclosure of their enantiomeric fractions (EF) allows discrimination between consumption, direct disposal, and synthesis pathways. The aim of this study was to develop and validate an indirect method by gas chromatography coupled to mass spectrometry (GC–MS) based on derivatization using (R)-(−)-α-methoxy-α-(trifluoromethyl) phenylacetyl chloride as chiral derivatization reagent, for enantiomeric quantification of amphetamine (AMP), methamphetamine (MAMP), 3,4-methylenedioxymethamphetamine (MDMA), norketamine, buphedrone (BPD), butylone, 3,4-dimethylmethcathinone (3,4-DMMC), 3-methylmethcathinone, and quantification of 1-benzylpiperazine and 1-(4-metoxyphenyl)-piperazine. The method allowed to evaluate the occurrence, spatial distribution, and the EF of the target chiral PAS in Portuguese surface waters and in effluents from 2 wastewater treatment plants (WWTP). For that, water samples were pre-concentrated by solid phase extraction using OASIS® MCX cartridges, derivatized and further analyzed by GC–MS. Both enantiomers of AMP, (R)-MDMA, (S)-MAMP, and the first eluted enantiomer of BPD (configuration not assigned) were found in surface waters, while effluent samples showed both enantiomers of MDMA, (S)-MAMP, (R)-AMP, and the first eluted enantiomer of BPD and 3,4-DMMC. According to our knowledge, this is the first multiresidue analytical method by CG–MS enrolling cathinones, amphetamines, and piperazines. The presence of illicit synthetic cathinones in Douro River estuary is here reported for the first time, along with other amphetamine derivatives. The potential of the method to monitor consumption of the target PAS was demonstrated.
      Citation: Chemosensors
      PubDate: 2021-08-13
      DOI: 10.3390/chemosensors9080224
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 225: Preparation and Application of 2D
           MXene-Based Gas Sensors: A Review

    • Authors: Qingting Li, Yanqiong Li, Wen Zeng
      First page: 225
      Abstract: Since MXene (a two-dimensional material) was discovered in 2011, it has been favored in all aspects due to its rich surface functional groups, large specific surface area, high conductivity, large porosity, rich organic bonds, and high hydrophilicity. In this paper, the preparation of MXene is introduced first. HF etching was the first etching method for MXene; however, HF is corrosive, resulting in the development of the in situ HF method (fluoride + HCl). Due to the harmful effects of fluorine terminal on the performance of MXene, a fluorine-free preparation method was developed. The increase in interlayer spacing brought about by adding an intercalator can affect MXene’s performance. The usual preparation methods render MXene inevitably agglomerate and the resulting yields are insufficient. Many new preparation methods were researched in order to solve the problems of agglomeration and yield. Secondly, the application of MXene-based materials in gas sensors was discussed. MXene is often regarded as a flexible gas sensor, and the detection of ppb-level acetone at room temperature was observed for the first time. After the formation of composite materials, the increasing interlayer spacing and the specific surface area increased the number of active sites of gas adsorption and the gas sensitivity performance improved. Moreover, this paper discusses the gas-sensing mechanism of MXene. The gas-sensing mechanism of metallic MXene is affected by the expansion of the lamellae and will be doped with H2O and oxygen during the etching process in order to become a p-type semiconductor. A p-n heterojunction and a Schottky barrier forms due to combinations with other semiconductors; thus, the gas sensitivities of composite materials are regulated and controlled by them. Although there are only several reports on the application of MXene materials to gas sensors, MXene and its composite materials are expected to become materials that can effectively detect gases at room temperature, especially for the detection of NH3 and VOC gas. Finally, the challenges and opportunities of MXene as a gas sensor are discussed.
      Citation: Chemosensors
      PubDate: 2021-08-14
      DOI: 10.3390/chemosensors9080225
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 226: Application of Metal-Organic
           Framework-Based Composites for Gas Sensing and Effects of Synthesis
           Strategies on Gas-Sensitive Performance

    • Authors: Bo Huang, Yanqiong Li, Wen Zeng
      First page: 226
      Abstract: Gas sensing materials, such as semiconducting metal oxides (SMOx), carbon-based materials, and polymers have been studied in recent years. Among of them, SMOx-based gas sensors have higher operating temperatures; sensors crafted from carbon-based materials have poor selectivity for gases and longer response times; and polymer gas sensors have poor stability and selectivity, so it is necessary to develop high-performance gas sensors. As a porous material constructed from inorganic nodes and multidentate organic bridging linkers, the metal-organic framework (MOF) shows viable applications in gas sensors due to its inherent large specific surface area and high porosity. Thus, compounding sensor materials with MOFs can create a synergistic effect. Many studies have been conducted on composite MOFs with three materials to control the synergistic effects to improve gas sensing performance. Therefore, this review summarizes the application of MOFs in sensor materials and emphasizes the synthesis progress of MOF composites. The challenges and development prospects of MOF-based composites are also discussed.
      Citation: Chemosensors
      PubDate: 2021-08-14
      DOI: 10.3390/chemosensors9080226
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 227: Nitrogen Dioxide Gas Sensor Based on
           Ag-Doped Graphene: A First-Principle Study

    • Authors: Qichao Li, Yamin Liu, Di Chen, Jianmin Miao, Xiao Zhi, Shengwei Deng, Shujing Lin, Han Jin, Daxiang Cui
      First page: 227
      Abstract: High-performance tracking trace amounts of NO2 with gas sensors could be helpful in protecting human health since high levels of NO2 may increase the risk of developing acute exacerbation of chronic obstructive pulmonary disease. Among various gas sensors, Graphene-based sensors have attracted broad attention due to their sensitivity, particularly with the addition of noble metals (e.g., Ag). Nevertheless, the internal mechanism of improving the gas sensing behavior through doping Ag is still unclear. Herein, the impact of Ag doping on the sensing properties of Graphene-based sensors is systematically analyzed via first principles. Based on the density-functional theory (DFT), the adsorption behavior of specific gases (NO2, NH3, H2O, CO2, CH4, and C2H6) on Ag-doped Graphene (Ag–Gr) is calculated and compared. It is found that NO2 shows the strongest interaction and largest Mulliken charge transfer to Ag–Gr among these studied gases, which may directly result in the highest sensitivity toward NO2 for the Ag–Gr-based gas sensor.
      Citation: Chemosensors
      PubDate: 2021-08-14
      DOI: 10.3390/chemosensors9080227
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 228: Botulinum Neurotoxin-C Detection Using
           Nanostructured Porous Silicon Interferometer

    • Authors: Dashananda Nanda Kumar, Zina Baider, Daniel Elad, Shlomo E. Blum, Giorgi Shtenberg
      First page: 228
      Abstract: Botulinum neurotoxins (BoNT) are the most potent toxins, which are produced by Clostridium bacteria and cause the life-threatening disease of botulism in all vertebrates. Specifically, animal botulism represents a serious environmental and economic concern in animal production due to the high mortality rates observed during outbreaks. Despite the availability of vaccines against BoNT, there are still many outbreaks of botulism worldwide. Alternative assays capable of replacing the conventional in vivo assay in terms of rapid and sensitive quantification, and the applicability for on-site analysis, have long been perused. Herein, we present a simple, highly sensitive and label-free optical biosensor for real-time detection of BoNT serotype C using a porous silicon Fabry–Pérot interferometer. A competitive immunoassay coupled to a biochemical cascade reaction was adapted for optical signal amplification. The resulting insoluble precipitates accumulated within the nanostructure changed the reflectivity spectra by alternating the averaged refractive index. The augmented optical performance allowed for a linear response within the range of 10 to 10,000 pg mL−1 while presenting a detection limit of 4.8 pg mL−1. The practical aspect of the developed assay was verified using field BoNT holotoxins to exemplify the potential use of the developed optical approach for rapid bio-diagnosis of BoNT. The specificity and selectivity of the assay were successfully validated using an adjacent holotoxin relevant for farm animals (BoNT serotype D). Overall, this work sets the foundation for implementing a miniaturized interferometer for routine on-site botulism diagnosis, thus significantly reducing the need for animal experimentation and shortening analysis turnaround for early evidence-based therapy.
      Citation: Chemosensors
      PubDate: 2021-08-16
      DOI: 10.3390/chemosensors9080228
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 229: Gold Nanoparticles/Carbon Nanotubes and
           Gold Nanoporous as Novel Electrochemical Platforms for L-Ascorbic Acid
           Detection: Comparative Performance and Application

    • Authors: Cristina Tortolini, Federico Tasca, Mary Anna Venneri, Cinzia Marchese, Riccarda Antiochia
      First page: 229
      Abstract: Herein, the effects of nanostructured modifications of a gold electrode surface in the development of electrochemical sensors for L-ascorbic acid detection have been investigated. In particular, a bare gold electrode has been modified by electrodeposition of gold single-walled carbon nanotubes (Au/SWCNTs) and by the formation of a highly nanoporous gold (h-nPG) film. The procedure has been realized by sweeping the potential between +0.8 V and 0 V vs. Ag/AgCl for 25 scans in a suspension containing 5 mg/mL of SWCNTs in 10 mM HAuCl4 and 2.5 M NH4Cl solution for Au/SWCNTs modified gold electrode. A similar procedure was applied for a h-nPG electrode in a 10 mM HAuCl4 solution containing 2.5 M NH4Cl, followed by applying a fixed potential of −4 V vs. Ag/AgCl for 60 s. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the properties of the modified electrodes. The developed sensors showed strong electrocatalytic activity towards ascorbic acid oxidation with enhanced sensitivities of 1.7 × 10−2 μA μM−1cm−2 and 2.5 × 10−2 μA μM−1cm−2 for Au/SWCNTs and h-nPG modified electrode, respectively, compared to bare gold electrode (1.0 × 10−2 μA μM−1cm−2). The detection limits were estimated to be 3.1 and 1.8 μM, respectively. The h-nPG electrode was successfully used to determine ascorbic acid in human urine with no significant interference and with satisfactory recovery levels.
      Citation: Chemosensors
      PubDate: 2021-08-16
      DOI: 10.3390/chemosensors9080229
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 230: Highly Sensitive Quartz-Based Sensing
           System for the Detection of Subpercentage Changes in the Relative
           Permittivity of Liquids Flowing in Microchannels

    • Authors: Vojko Matko, Miro Milanovič
      First page: 230
      Abstract: We describe a highly sensitive quartz sensor for measuring changes in the relative permittivity of liquids flowing in microchannels. The proposed method uses a highly stable oscillator and capacitance-dependent quartz crystal together with a capacitance-sensitive element attached along the microchannel. A change in the relative permittivity of the fluid induces a change in the capacitance of the sensitive element in the aF range, which is detected as a change in the resonant frequency. The advantages of the proposed measurement technique are the extreme sensitivity (changes in the relative permittivity as low as 0.01% can be detected), the temperature independence of the setup between 10 and 40 °C, the stability (the frequency reading fluctuates within 0.025 Hz), and the low cost compared with the methods that use impedance analyzers or lock-in amplifiers. We present the use of the method to detect changes in mixtures of liquids if the temperature, volume fractions, or properties of one liquid change. The method presents a useful tool for applications in biology, chemistry, pharmacy, and technology in general wherever accurate monitoring of compositions of fluids is required and where changes, for example, due to temperature variation or mixture aging, need to be detected in real time.
      Citation: Chemosensors
      PubDate: 2021-08-18
      DOI: 10.3390/chemosensors9080230
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 231: Phenolic Compounds from Irradiated Olive
           Wastes: Optimization of the Heat-Assisted Extraction Using Response
           Surface Methodology

    • Authors: Joana Madureira, Bruno Melgar, Celestino Santos-Buelga, Fernanda M. A. Margaça, Isabel C. F. R. Ferreira, Lillian Barros, Sandra Cabo Verde
      First page: 231
      Abstract: Olive pomace, an environmentally detrimental residue generated during olive oil extraction, contains bioactive compounds in demand by the food industry. To valorize this waste product a suitable yield for the extraction process is required. Heat-assisted extraction of bioactive compounds from olive pomace was optimized by a circumscribed central composite design and response surface methodology. Our previous studies indicated that irradiation could improve 2.4-fold the extractability of the main phenolic compounds from olive pomace. The effect of extraction time, temperature and solvent concentration on the yield of polyphenols from irradiated olive pomace at 5 kGy was tested. Hydroxytyrosol-1-β-glucoside, hydroxytyrosol, tyrosol and caffeic acid were quantified by High Performance Liquid Chromatography to calculate the total polyphenol content. The optimal general conditions by RSM modeling were extraction time of 120 min, temperature of 85 °C, and 76% of ethanol in water. Using these selected conditions, 19.04 ± 1.50 mg/g dry weight, 148.88 ± 8.73 mg/g extract of total polyphenols were obtained, representing a yield of 13.7%, which was consistent with the value predicted by the model. This work demonstrated the potential of residues from the olive oil industry as a suitable alternative to obtain compounds that could be used as ingredients for the food industry.
      Citation: Chemosensors
      PubDate: 2021-08-19
      DOI: 10.3390/chemosensors9080231
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 232: Advances in Antimicrobial Resistance
           Monitoring Using Sensors and Biosensors: A Review

    • Authors: Eduardo C. Reynoso, Serena Laschi, Ilaria Palchetti, Eduardo Torres
      First page: 232
      Abstract: The indiscriminate use and mismanagement of antibiotics over the last eight decades have led to one of the main challenges humanity will have to face in the next twenty years in terms of public health and economy, i.e., antimicrobial resistance. One of the key approaches to tackling antimicrobial resistance is clinical, livestock, and environmental surveillance applying methods capable of effectively identifying antimicrobial non-susceptibility as well as genes that promote resistance. Current clinical laboratory practices involve conventional culture-based antibiotic susceptibility testing (AST) methods, taking over 24 h to find out which medication should be prescribed to treat the infection. Although there are techniques that provide rapid resistance detection, it is necessary to have new tools that are easy to operate, are robust, sensitive, specific, and inexpensive. Chemical sensors and biosensors are devices that could have the necessary characteristics for the rapid diagnosis of resistant microorganisms and could provide crucial information on the choice of antibiotic (or other antimicrobial medicines) to be administered. This review provides an overview on novel biosensing strategies for the phenotypic and genotypic determination of antimicrobial resistance and a perspective on the use of these tools in modern health-care and environmental surveillance.
      Citation: Chemosensors
      PubDate: 2021-08-19
      DOI: 10.3390/chemosensors9080232
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 233: Evaluation of Photosensitive Paper
           Coatings as Detectors for Instrumentation-Free UV Photometric Analysis
           Based on Photography-Based Photometry

    • Authors: Tatiana G. Choleva, Afroditi Sfakianaki, Athanasios G. Vlessidis, Dimosthenis L. Giokas
      First page: 233
      Abstract: Photography-based photometry is a technique developed to perform high throughput UV photometric analysis without instrumental detectors in resource-limited settings. Its principle relies on the illumination of a sample with UV irradiation and then capturing the transmitted irradiation on a photosensitive paper surface. Therefore, the photosensitive surface acts as a detector for the determination of the concentration of analytes in the sample. This work aims to investigate the optimum photosensitive paper coatings for capturing the transmitted UV irradiation. To this end, photosensitive coatings based on silver, iron, and dichromate salts were tested using three assays of pharmaceutical and biochemical interest. The results from both calibrations, using standard solutions and the application in real samples, show that photosensitive coatings based on iron salts provide the best results. Importantly, the detection limits and the linear range of the calibration curves were better than those obtained with standard photometry. Based on these findings, cyanotype green papers, are proposed as optimum detectors for photography-based photometry. This finding simplifies the operation of the technique enabling the fabrication of prototype readers for analytical assays performed in resource limited settings, point-of-need applications or in the field.
      Citation: Chemosensors
      PubDate: 2021-08-20
      DOI: 10.3390/chemosensors9080233
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 234: A Novel Dialkylamino GFP Chromophore as
           an Environment-Polarity Sensor Reveals the Role of Twisted Intramolecular
           Charge Transfer

    • Authors: Cheng Chen, Sean A. Boulanger, Anatolii I. Sokolov, Mikhail S. Baranov, Chong Fang
      First page: 234
      Abstract: We discovered a novel fluorophore by incorporating a dimethylamino group (–NMe2) into the conformationally locked green fluorescent protein (GFP) scaffold. It exhibited a marked solvent-polarity-dependent fluorogenic behavior and can potentially find broad applications as an environment-polarity sensor in vitro and in vivo. The ultrafast femtosecond transient absorption (fs-TA) spectroscopy in combination with quantum calculations revealed the presence of a twisted intramolecular charge transfer (TICT) state, which is formed by rotation of the –NMe2 group in the electronic excited state. In contrast to the bright fluorescent state (FS), the TICT state is dark and effectively quenches fluorescence upon formation. We employed a newly developed multivariable analysis approach to the FS lifetime in various solvents and showed that the FS → TICT reaction barrier is mainly modulated by H-bonding capability instead of viscosity of the solvent, accounting for the observed polarity dependence. These deep mechanistic insights are further corroborated by the dramatic loss of fluorogenicity for two similar GFP-derived chromophores in which the rotation of the –NMe2 group is inhibited by structural locking.
      Citation: Chemosensors
      PubDate: 2021-08-23
      DOI: 10.3390/chemosensors9080234
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 235: Evaluating TiO2 Photocatalysis
           Performance in Microtubes on Paper Background by Smartphone: Principles
           and Application Examples

    • Authors: Xian Liu, Chengxiang Xu, Shiwei Xie, Lei Zhu, Xun Wang
      First page: 235
      Abstract: Titanium dioxide (TiO2) photocatalysis is a popular and promising technology in water treatment, but the performance evaluation usually depends on expensive equipment. In this study, using a smartphone for colorimetric detection, a self-invented method based on paper and microtubes (PMTs) is proposed to test the photocatalytic performance of TiO2. Firstly, the study has identified that PMTs achieved a correlation coefficient of above 0.9 between the greyscale values and concentrations during the physical process of different color dyes (i.e., rhodamine B (RhB), reactive yellow (RY), methylene blue (MB), and mixtures of the two or three dyes). The results indicate that when the principle of solution color follows the CMYK (Cyan, Magenta, Yellow, Black) color model, its photo color on white paper background conforms to the RGB (Red, Green, Blue) color model. Compared to the results obtained from the absorbance method, the PMTs method showed high reliabilities up to 99.36% on the monitoring of the photocatalytic process of the different dye solutions. Interestingly, the colorless solution of salicylic acid (SA) could also be analyzed by the PMTs after complexed with Fe(III) ion to develop a purple solution. These results suggest that the PMTs could be an alternative analysis method to evaluating physical and chemical reaction processes when the high-tech analysis equipment is unviable.
      Citation: Chemosensors
      PubDate: 2021-08-23
      DOI: 10.3390/chemosensors9080235
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 236: Fabrication of an All-Solid-State
           Carbonate Ion-Selective Electrode with Carbon Film as Transducer and Its
           Preliminary Application in Deep-Sea Hydrothermal Field Exploration

    • Authors: Chuqing Zhang, Yang He, Jianbo Wu, Manqing Ai, Wei Cai, Ying Ye, Chunhui Tao, Pingping Zhang, Quan Jin
      First page: 236
      Abstract: Real-time measurements of carbonate ion concentrations in the ocean are critical to advancing marine environmental monitoring and research into deep-sea hydrothermal activity. Herein, we report the first example of deep-sea hydrothermal field exploration using a carbonate ion-selective electrode (ISE). The novel carbonate ISE was composed of a Ni wire as substrate, carbon film as transducers and carbonate-selective membrane layers. This paper describes the preparation process of the electrode and characterises its performance via scanning electron microscopy (SEM) and electrochemical analysis. The detection limit of the electrode for CO32− is 2.821 × 10−6 mol/L, the linear response range is 1.0 × 10−5–1.0 × 10−1 mol/L and the Nernst slope was −30.4 mV/decade. In April 2021, the carbonate ISE was mounted on multi-parameter sensors with pH and Eh (redox) electrodes for the search of hydrothermal activity at the Southwest Indian Ridge. The simultaneous potential anomalies appeared at this carbonate electrode with the pH and Eh electrodes when passing through the hydrothermal field. The study of the hydrothermal field was supported by the in situ camera video and the sulphide samples. Additionally, the carbonate electrode provides enhanced information of water chemistry for the study of the hydrothermal field.
      Citation: Chemosensors
      PubDate: 2021-08-23
      DOI: 10.3390/chemosensors9080236
      Issue No: Vol. 9, No. 8 (2021)
  • Chemosensors, Vol. 9, Pages 294: Development of Electrochemical
           Sensors/Biosensors to Detect Natural and Synthetic Compounds Related to
           Agroalimentary, Environmental and Health Systems in Argentina. A Review of
           the Last Decade

    • Authors: Adrian M. Granero, Héctor Fernández, María A. Zon, Sesbastián N. Robledo, Gastón D. Pierini, Aylen Di Tocco, Roodney A. Carrillo Palomino, Sabrina Maccio, Walter I. Riberi, Fernando J. Arévalo
      First page: 294
      Abstract: Electrochemical sensors and biosensors are analytical tools, which are in continuous development with the aim of generating new analytical devices which are more reliable, cheaper, faster, sensitive, selective, and robust than others. In matrices related to agroalimentary, environmental, or health systems, natural or synthetic compounds occur which fulfil specific roles; some of them (such as mycotoxins or herbicides) may possess harmful properties, and others (such as antioxidants) beneficial ones. This imposes a challenge to develop new tools and analytical methodologies for their detection and quantification. This review summarises different aspects related to the development of electrochemical sensors and biosensors carried out in Argentina in the last ten years for application in agroalimentary, environmental, and health fields. The discussion focuses on the construction and development of electroanalytical methodologies for the determination of mycotoxins, herbicides, and natural and synthetic antioxidants. Studies based on the use of different electrode materials modified with micro/nanostructures, functional groups, and biomolecules, complemented by the use of chemometric tools, are explored. Results of the latest reports from research groups in Argentina are presented. The main goals are highlighted.
      Citation: Chemosensors
      PubDate: 2021-10-20
      DOI: 10.3390/chemosensors9110294
      Issue No: Vol. 9, No. 11 (2021)
  • Chemosensors, Vol. 9, Pages 295: Tungsten-Based Cost-Effective Gas Sensors
           for H2S Detection

    • Authors: Fasquelle, Verbrugghe, Députier
      First page: 295
      Abstract: Tungsten trioxide thin films were deposited on silicon substrates by non-reactive RF sputtering from a WO3 target at room temperature. The WO3 films were post-annealed at two different temperatures, 400 °C and 500 °C. The morphological and microstructural properties of these films were analyzed by using atomic force microscopy and X-ray diffraction. X-ray diffraction patterns only show WO3 oxide phases. The AFM images show different morphologies with smaller grains for the film annealed at 400 °C. WO3 sensing films and W heating elements were embedded in commercial cases for the fabrication of cost-effective gas sensors. The sensitivity and dynamic response of the sensors were analyzed under various concentrations of H2S, from 20 to 100 ppm, at SIMTRONICS SAS (3M Company, Saint Paul, MN, USA). A good sensitivity G/G0 of about 6.6 under H2S 100 ppm was obtained with the best sensor. An interesting dynamic response was observed in particular with a short response time. Additionally, the evolution of the sensitivity was studied, and a conduction model was proposed for explaining the conduction mechanism under H2S exposition.
      Citation: Chemosensors
      PubDate: 2021-10-20
      DOI: 10.3390/chemosensors9110295
      Issue No: Vol. 9, No. 11 (2021)
  • Chemosensors, Vol. 9, Pages 296: VinegarScan: A Computer Tool Based on
           Ultraviolet Spectroscopy for A Rapid Authentication of Wine Vinegars

    • Authors: Rocío Ríos-Reina, Daniel Caballero, Silvana M. Azcarate, Diego L. García-González, Raquel M. Callejón, José M. Amigo
      First page: 296
      Abstract: Ultraviolet-visible (UV-vis) spectroscopy has shown successful results in the last few years to characterize and classify wine vinegar according to its quality, particularly those with a protected designation of origin (PDO). Due to these promising results, together with the simplicity, price, speed, portability of this technique and its ability to create robust hierarchical classification models, the objective of this work was the development of a computer tool or software, named VinegarScan, which uses the UV-vis spectra to be able to perform quality control and authentication of wine vinegar in a quick and user-friendly way. This software was based on the open-source GUI created in C++ using several data mining algorithms (e.g., decision trees, classification algorithms) on UV-vis spectra. This software achieved satisfactory prediction results with the available analytical UV-vis data. The future idea of utility is to combine the VinegarScan tool with a portable UV-vis device that could be used by control bodies of the wine vinegar industry to achieve a clear differentiation from their competitors to avoid fraud.
      Citation: Chemosensors
      PubDate: 2021-10-22
      DOI: 10.3390/chemosensors9110296
      Issue No: Vol. 9, No. 11 (2021)
  • Chemosensors, Vol. 9, Pages 272: MagnetoPlasmonic Waves/HOMO-LUMO Free
           π-Electron Transitions Coupling in Organic Macrocycles and Their Effect
           in Sensing Applications

    • Authors: Maria Grazia Manera, Gabriele Giancane, Simona Bettini, Ludovico Valli, Victor Borovkov, Adriano Colombelli, Daniela Lospinoso, Roberto Rella
      First page: 272
      Abstract: Optical and magneto-optical surface plasmon resonance (MOSPR) characterization and preliminary sensing test onto single- and multi-layers of two organic macrocycles have been performed; TbPc2(OC11H21)8 phthalocyanine and CoCoPo2 porphyrin were deposited by the Langmuir-Schäfer (LS) technique onto proper Au/Co/Au magneto-optical transducers. Investigations of the MOSPR properties in Kretschmann configuration by angular modulation, gives us an indication about the potential discrimination of two organic macrocycles with absorption electronic transition in and out of the propagating plasmon energy spectral range. An improved molecular vapors sensitivity increase by the MOSPR sensing probe can be demonstrated depending on the overlap between the plasmonic probe energy and the absorption electronic transitions of the macrocycles under investigation. If the interaction between the plasmon energy and molecular HOMO-LUMO transition is preserved, a variation in the complex refractive index takes place. Under this condition, the magneto-plasmonic effect reported as 1/ MOSPR signal allows us to increase the detection of molecules deposited onto the plasmonic transducer and their gas sensing capacity. The detection mechanism appears strongly enhanced if the Plasmon Wave/HOMO-LUMO transitions energy are in resonance. Under coupling conditions, a different volatile organic compounds (VOC) sensing capability has been demonstrated using n-butylamine as the trial molecule.
      Citation: Chemosensors
      PubDate: 2021-09-22
      DOI: 10.3390/chemosensors9100272
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 273: Comprehensive Characterization of 76
           Pharmaceuticals and Metabolites in Wastewater by LC-MS/MS

    • Authors: Cristian Gómez-Canela, Sílvia Edo, Natalia Rodríguez, Gemma Gotor, Sílvia Lacorte
      First page: 273
      Abstract: Wastewaters are considered one of the main sources of pollution in the aquatic environment as release a large number of contaminants every day. Emerging contaminants such as pharmaceuticals have special interest due to the high levels of consumption by the global population, their bioactive properties and because actual directives do not include the monitoring of pharmaceuticals. Moreover, it is well-known that pharmaceuticals can be degraded to metabolites or transformation products (TPs), which could be more toxic than the parental compound. In this study, we have developed an analytical method based on solid-phase extraction (SPE) and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) to determine 76 highly consumed pharmaceuticals, including metabolites and TPs in wastewater effluents. In the 10 wastewaters analysed, the mean concentrations were in the µg L−1 levels, being mycophenolic acid, levodopa, ibuprofen, 4-aminoantypirine, losartan, amylmetacresol, amoxicillin, fluticasone, tramadol, budesonide, chlorpheniramine and diclofenac the pharmaceuticals with the highest concentrations. This study provides a comprehensive optimization on the MS conditions to determine pharmaceutical compounds and their metabolites and provides a spectral characterization to be used for the identification of these compounds in water.
      Citation: Chemosensors
      PubDate: 2021-09-24
      DOI: 10.3390/chemosensors9100273
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 274: Potentiometric C2H4-Selective Detection
           on Solid-State Sensors Activated with Bifunctional Catalytic Nanoparticles

    • Authors: Fidel Toldra-Reig, Jose Manuel Serra
      First page: 274
      Abstract: This work presents a solid-state ionic-based device to selectively detect C2H4 in car exhaust gases. The sensor consists of 8YSZ as the electrolyte and two electrodes: Fe0.7Cr1.3O3/8YSZ and LSM/8YSZ. The main aim of this work is to optimize the catalytic behavior of the working electrode to C2H4 and reduce cross-sensitivity toward CO and H2O. Several catalyst nanoparticles were infiltrated to tailor C2H4 adsorption and electrochemical oxidation properties while diminishing adsorption and conversion of other gas components such as CO. The infiltrated metal catalysts were selected, taking into account both adsorption and redox properties. Infiltration of Ti or Al, followed by a second infiltration of Ni, enabled the selective detection of C2H4 with low cross-sensitivity toward CO and H2O in a moist gas environment. Further insight into potentiometric C2H4 sensing is achieved by electrochemical impedance analysis of the electrodes activated with bifunctional catalysts.
      Citation: Chemosensors
      PubDate: 2021-09-27
      DOI: 10.3390/chemosensors9100274
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 275: Current State of Laser-Induced
           Fluorescence Spectroscopy for Designing Biochemical Sensors

    • Authors: Adam Thomas Taylor, Edward P. C. Lai
      First page: 275
      Abstract: Laser-induced fluorescence (LIF) has been a valuable analytical technique since the 1970s that has only been made more useful through advances in other scientific fields such as biochemistry. Moreover, advances in laser and detector technology have seen a decrease in LIF detector costs and an increase in their ease of use. These changes have allowed for LIF technology to be widely adopted for various sensor designs in combination with advanced instruments. With advances in biochemistry necessitating the detection of complex metabolites, labelling with fluorescent chemical reagents may be necessary to improve detection sensitivity. Furthermore, advances made in fluorescent labeling technologies have allowed for the use of LIF in the detection of nanoparticles as well as for imaging techniques using nanoparticles as signal amplifiers. This technology has become invaluable in the detection of environmental pollutants, monitoring of biological metabolites, biological imaging, and cancer diagnosis, making it one of the most valuable analytical science techniques currently available.
      Citation: Chemosensors
      PubDate: 2021-09-27
      DOI: 10.3390/chemosensors9100275
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 276: Ultrathin PANI-Decorated, Highly Purified
           and Well Dispersed Array Cncs for Highly Sensitive HCHO Sensors

    • Authors: Qingmin Hu, Zhiheng Ma, Jie Yang, Tiange Gao, Yue Wu, Zhe Dong, Xuyi Li, Wen Zeng, Shichao Zhao, Jiaqiang Xu
      First page: 276
      Abstract: The flocculation of small surficial groups on pristine CNCs (carbon nanocoils) bundles limit their application. In this study, we designed and fabricated novel array CNCs with a surficial decoration of polyaniline (PANI) using in situ methods. Atomic layer deposition (ALD) and chemical vapor deposition (CVD) methods were employed to fabricate the highly pure array CNCs. The array CNCs decorated with ultra-thin PANI were confirmed by different characterizations. Furthermore, this material displayed a good performance in its detection of formaldehyde. The detection results showed that the CNCs coated with PANI had a low limit of detection of HCHO, as low as 500 ppb, and the sensor also showed good selectivity for other interfering gases, as well as good repeatability over many tests. Furthermore, after increasing the PANI loading on the surface of the CNCs, their detection performance exhibited a typical volcanic curve, and the value of the enthalpy was extracted by using the temperature-varying micro-gravimetric method during the process of detection of the formaldehyde molecules on the CNCs. The use of array CNCs with surficial decoration offers a novel method for the application of CNCs and could be extended to other applications, such as catalysts and energy conversion.
      Citation: Chemosensors
      PubDate: 2021-09-28
      DOI: 10.3390/chemosensors9100276
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 277: Electrochemical Performance of
           Lithographically-Defined Micro-Electrodes for Integration and Device

    • Authors: Zohreh Hirbodvash, Mohamed S. E. Houache, Oleksiy Krupin, Maryam Khodami, Howard Northfield, Anthony Olivieri, Elena A. Baranova, Pierre Berini
      First page: 277
      Abstract: Small; lithographically-defined and closely-spaced metallic features of dimensions and separation in the micrometer range are of strong interest as working and counter electrodes in compact electrochemical sensing devices. Such micro-electrode systems can be integrated with microfluidics and optical biosensors, such as surface plasmon waveguide biosensors, to enable multi-modal sensing strategies. We investigate lithographically-defined gold and platinum micro-electrodes experimentally, via cyclic voltammetry (CV) measurements obtained at various scan rates and concentrations of potassium ferricyanide as the redox species, in potassium nitrate as the supporting electrolyte. The magnitude of the double-layer capacitance is estimated using the voltammograms. Concentration curves for potassium ferricyanide are extracted from our CV measurements as a function of scan rate, and could be used as calibration curves from which an unknown concentration of potassium ferricyanide in the range of 0.5–5 mM can be determined. A blind test was done to confirm the validity of the calibration curve. The diffusion coefficient of potassium ferricyanide is also extracted from our CV measurements by fitting to the Randles–Sevcik equation (D = 4.18 × 10−10 m2/s). Our CV measurements were compared with measurements obtained using macroscopic commercial electrodes, yielding good agreement and verifying that the shape of our CV curves do not depend on micro-electrode geometry (only on area). We also compare our CV measurements with theoretical curves computed using the Butler–Volmer equation, achieving essentially perfect agreement while extracting the rate constant at zero potential for our redox species (ko = 10−6 m/s). Finally, we demonstrate the importance of burn-in to stabilize electrodes from the effects of electromigration and grain reorganization before use in CV measurements, by comparing with results obtained with as-deposited electrodes. Burn-in (or equivalently, annealing) of lithographic microelectrodes before use is of general importance to electrochemical sensing devices
      Citation: Chemosensors
      PubDate: 2021-09-28
      DOI: 10.3390/chemosensors9100277
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 278: Thiourea Organocatalysts as Emerging
           Chiral Pollutants: En Route to Porphyrin-Based (Chir)Optical Sensing

    • Authors: Nele Konrad, Matvey Horetski, Mariliis Sihtmäe, Khai-Nghi Truong, Irina Osadchuk, Tatsiana Burankova, Marc Kielmann, Jasper Adamson, Anne Kahru, Kari Rissanen, Mathias O. Senge, Victor Borovkov, Riina Aav, Dzmitry Kananovich
      First page: 278
      Abstract: Environmental pollution with chiral organic compounds is an emerging problem requiring innovative sensing methods. Amino-functionalized thioureas, such as 2-(dimethylamino)cyclohexyl-(3,5-bis(trifluoromethyl)phenyl)thiourea (Takemoto’s catalyst), are widely used organocatalysts with virtually unknown environmental safety data. Ecotoxicity studies based on the Vibrio fischeri luminescence inhibition test reveal significant toxicity of Takemoto’s catalyst (EC50 = 7.9 mg/L) and its NH2-substituted analog (EC50 = 7.2–7.4 mg/L). The observed toxic effect was pronounced by the influence of the trifluoromethyl moiety. En route to the porphyrin-based chemosensing of Takemoto-type thioureas, their supramolecular binding to a series of zinc porphyrins was studied with UV-Vis and circular dichroism (CD) spectroscopy, computational analysis and single crystal X-ray diffraction. The association constant values generally increased with the increasing electron-withdrawing properties of the porphyrins and electron-donating ability of the thioureas, a result of the predominant Zn⋯N cation–dipole (Lewis acid–base) interaction. The binding event induced a CD signal in the Soret band region of the porphyrin hosts—a crucial property for chirality sensing of Takemoto-type thioureas.
      Citation: Chemosensors
      PubDate: 2021-09-29
      DOI: 10.3390/chemosensors9100278
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 279: Advances in Chirality Sensing with
           Macrocyclic Molecules

    • Authors: Xiaotong Liang, Wenting Liang, Pengyue Jin, Hongtao Wang, Wanhua Wu, Cheng Yang
      First page: 279
      Abstract: The construction of chemical sensors that can distinguish molecular chirality has attracted increasing attention in recent years due to the significance of chiral organic molecules and the importance of detecting their absolute configuration and chiroptical purity. The supramolecular chirality sensing strategy has shown promising potential due to its advantages of high throughput, sensitivity, and fast chirality detection. This review focuses on chirality sensors based on macrocyclic compounds. Macrocyclic chirality sensors usually have inherent complexing ability towards certain chiral guests, which combined with the signal output components, could offer many unique advantages/properties compared to traditional chiral sensors. Chirality sensing based on macrocyclic sensors has shown rapid progress in recent years. This review summarizes recent advances in chirality sensing based on both achiral and chiral macrocyclic compounds, especially newly emerged macrocyclic molecules.
      Citation: Chemosensors
      PubDate: 2021-09-29
      DOI: 10.3390/chemosensors9100279
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 280: Electrosynthesized Poly(o-aminophenol)
           Films as Biomimetic Coatings for Dopamine Detection on Pt Substrates

    • Authors: Rosanna Ciriello, Martina Graziano, Giuliana Bianco, Antonio Guerrieri
      First page: 280
      Abstract: Dopamine (DA) is a neurotransmitter, and its levels in the human body are associated with serious diseases. The need for a suitable detection method in medical practice has encouraged the development of electrochemical sensors that take advantage of DA electroactivity. Molecularly imprinted polymers (MIPs) are biomimetic materials able to selectively recognize target analytes. A novel MIP sensor for DA is proposed here based on a thin film of poly(o-aminophenol) electrosynthesized on bare Pt. A fast and easy method for executing the procedure for MIP deposition has been developed based on mild experimental conditions that are able to prevent electrode fouling from DA oxidation products. The MIP exhibited a limit of detection of 0.65 μM, and appreciable reproducibility and stability. The high recognition capability of poly(o-aminophenol) towards DA allowed for the achievement of notable selectivity: ascorbic acid, uric acid, serotonin, and tyramine did not interfere with DA detection, even at higher concentrations. The proposed sensor was successfully applied for DA detection in urine samples, showing good recovery.
      Citation: Chemosensors
      PubDate: 2021-09-30
      DOI: 10.3390/chemosensors9100280
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 281: Advances in Colorimetric Assay Based on
           AuNPs Modified by Proteins and Nucleic Acid Aptamers

    • Authors: Sopio Melikishvili, Ivan Piovarci, Tibor Hianik
      First page: 281
      Abstract: This review is focused on the biosensing assay based on AuNPs (AuNPs) modified by proteins, peptides and nucleic acid aptamers. The unique physical properties of AuNPs allow their modification by proteins, peptides or nucleic acid aptamers by chemisorption as well as other methods including physical adsorption and covalent immobilization using carbodiimide chemistry or based on strong binding of biotinylated receptors on neutravidin, streptavidin or avidin. The methods of AuNPs preparation, their chemical modification and application in several biosensing assays are presented with focus on application of nucleic acid aptamers for colorimetry assay for determination of antibiotics and bacteria in food samples.
      Citation: Chemosensors
      PubDate: 2021-10-02
      DOI: 10.3390/chemosensors9100281
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 282: Conductive Hydrogel-Based Electrochemical
           Sensor: A Soft Platform for Capturing Analyte

    • Authors: Li Fu, Aimin Yu, Guosong Lai
      First page: 282
      Abstract: Electrode modifications for electrochemical sensors attract a lot of attention every year. Among them, hydrogels are a relatively special class of electrode modifier. Since hydrogels often contain polymers, even though they are conductive polymers, they are not ideal electrode modifiers because of their poor conductivity. However, the micro-aqueous environment and the three-dimensional structure of hydrogels are an excellent platform for immobilizing bioactive molecules and maintaining their activity. This gives the hydrogel-modified electrochemical sensor the potential to perform specific recognition. At the same time, the rapid development of nanomaterials also makes the composite hydrogel have good electrical conductivity. This has led many scientists to become interested in hydrogel-based electrochemical sensors. In this review, we summarize the development process of hydrogel-based electrochemical sensors, starting from 2000. Hydrogel-based electrochemical sensors were initially used only as a carrier for biomolecules, mostly for loading enzymes and for specific recognition. With the widespread use of noble metal nanoparticles and carbon materials, hydrogels can now be used to prepare enzyme-free sensors. Although there are some sporadic studies on the use of hydrogels for practical applications, the vast majority of reports are still limited to the detection of common model molecules, such as glucose and H2O2. In the review, we classify hydrogels according to their different conducting strategies, and present the current status of the application of different hydrogels in electrochemical sensors. We also summarize the advantages and shortcomings of hydrogel-based electrochemical sensors. In addition, future prospects regarding hydrogel for electrochemical sensor use have been provided at the end.
      Citation: Chemosensors
      PubDate: 2021-10-04
      DOI: 10.3390/chemosensors9100282
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 283: pH-Induced Modulation of Vibrio fischeri
           Population Life Cycle

    • Authors: Ana Rita Silva, Cláudia Sousa, Daniela Exner, Ruth Schwaiger, Maria Madalena Alves, Dmitri Y. Petrovykh, Luciana Pereira
      First page: 283
      Abstract: Commonly used as biological chemosensors in toxicity assays, Vibrio fischeri bacteria were systematically characterized using complementary physicochemical and biological techniques to elucidate the evolution of their properties under varying environmental conditions. Changing the pH above or below the optimal pH 7 was used to model the long-term stress that would be experienced by V. fischeri in environmental toxicology assays. The spectral shape of bioluminescence and cell-surface charge during the exponential growth phase were largely unaffected by pH changes. The pH-induced modulation of V. fischeri growth, monitored via the optical density (OD), was moderate. In contrast, the concomitant changes in the time-profiles of their bioluminescence, which is used as the readout in assays, were more significant. Imaging at discrete timepoints by scanning electron microscopy (SEM) and helium-ion microscopy (HIM) revealed that mature V. fischeri cells maintained a rod-shaped morphology with the average length of 2.2 ± 1 µm and diameter of 0.6 ± 0.1 µm. Detailed morphological analysis revealed subpopulations of rods having aspect ratios significantly larger than those of average individuals, suggesting the use of such elongated rods as an indicator of the multigenerational environmental stress. The observed modulation of bioluminescence and morphology supports the suitability of V. fischeri as biological chemosensors for both rapid and long-term assays, including under environmental conditions that can modify the physicochemical properties of novel anthropogenic pollutants, such as nanomaterials and especially stimulus-responsive nanomaterials.
      Citation: Chemosensors
      PubDate: 2021-10-05
      DOI: 10.3390/chemosensors9100283
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 284: Ppb-Level Butanone Sensor Based on
           ZnO-TiO2-rGO Nanocomposites

    • Authors: Zhijia Liao, Yao Yu, Zhenyu Yuan, Fanli Meng
      First page: 284
      Abstract: In this paper, ZnO-TiO2-rGO nanocomposites were successfully synthesized by the hydrothermal method. The morphology and structure of the synthesized nanomaterials were characterized by SEM, XRD, HRTEM, and XPS. Butanone is a typical ketone product. The vapors are extremely harmful once exposed, triggering skin irritation in mild cases and affecting our breathing in severe cases. In this paper, the gas-sensing properties of TiO2, ZnO, ZnO-TiO2, and ZnO-TiO2-rGO nanomaterials to butanone vapor were studied. The optimum operating temperature of the ZnO-TiO2-rGO sensor is 145 °C, which is substantially lower than the other three sensors. The selectivity for butanone vapor is greatly improved, and the response is 5.6 times higher than that of other organic gases. The lower detection limit to butanone can reach 63 ppb. Therefore, the ZnO-TiO2-rGO sensor demonstrates excellent gas-sensing performance to butanone. Meanwhile, the gas-sensing mechanism of the ZnO-TiO2-rGO sensor to butanone vapor was also analyzed.
      Citation: Chemosensors
      PubDate: 2021-10-06
      DOI: 10.3390/chemosensors9100284
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 285: Tetraphenylethylene-Substituted
           Bis(thienyl)imidazole (DTITPE), An Efficient Molecular Sensor for the
           Detection and Quantification of Fluoride Ions

    • Authors: Ranjith Kumar Jakku, Nedaossadat Mirzadeh, Steven H. Privér, Govind Reddy, Anil Kumar Vardhaman, Giribabu Lingamallu, Rajiv Trivedi, Suresh Kumar Bhargava
      First page: 285
      Abstract: Fluoride ion plays a pivotal role in a range of biological and chemical applications however excessive exposure can cause severe kidney and gastric problems. A simple and selective molecular sensor, 4,5-di(thien-2-yl)-2-(4-(1,2,2-triphenylvinyl)-phenyl)-1H-imidazole, DTITPE, has been synthesized for the detection of fluoride ions, with detection limits of 1.37 × 10−7 M and 2.67 × 10−13 M, determined by UV-vis. and fluorescence spectroscopy, respectively. The variation in the optical properties of the molecular sensor in the presence of fluoride ions was explained by an intermolecular charge transfer (ICT) process between the bis(thienyl) and tetraphenylethylene (TPE) moieties upon the formation of a N-H---F− hydrogen bond of the imidazole proton. The sensing mechanism exhibited by DTITPE for fluoride ions was confirmed by 1H NMR spectroscopic studies and density functional theory (DFT) calculations. Test strips coated with the molecular sensor can detect fluoride ions in THF, undergoing a color change from white to yellow, which can be observed with the naked eye, showcasing their potential real-world application.
      Citation: Chemosensors
      PubDate: 2021-10-06
      DOI: 10.3390/chemosensors9100285
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 286: Paper-Based Device for Sweat Chloride

    • Authors: Tatiana G. Choleva, Christina Matiaki, Afroditi Sfakianaki, Athanasios G. Vlessidis, Dimosthenis L. Giokas
      First page: 286
      Abstract: A new method for the determination of chloride anions in sweat is described. The novelty of the method relies on the different photochemical response of silver ions and silver chloride crystals when exposed to UV light. Silver ions undergo an intense colorimetric transition from colorless to dark grey-brown due to the formation of nanosized Ag while AgCl exhibits a less intense color change from white to slightly grey. The analytical signal is obtained as mean grey value of color intensity on the paper surface and is expressed as the absolute difference between the signal of the blank (i.e., in absence of chloride) and the sample (i.e., in the presence of chloride). The method is simple to perform (addition of sample, incubation in the absence of light, irradiation, and offline measurement in a flatbed scanner), does not require any special signal processing steps (the color intensity is directly measured from a constant window on the paper surface without any imager processing) and is performed with minimum sample volume (2 μL). The method operates within a large chloride concentration range (10–140 mM) with good detection limits (2.7 mM chloride), satisfactory recoveries (95.2–108.7%), and reproducibility (<9%). Based on these data the method could serve as a potential tool for the diagnosis of cystic fibrosis through the determination of chloride in human sweat.
      Citation: Chemosensors
      PubDate: 2021-10-08
      DOI: 10.3390/chemosensors9100286
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 287: Spectroscopic and Colorimetric Studies
           for Anions with a New Urea-Based Molecular Cleft

    • Authors: Sanchita Kundu, Tochukwu Kevin Egboluche, Zehra Yousuf, Md. Alamgir Hossain
      First page: 287
      Abstract: A new simple urea-based dipodal molecular cleft (L) has been synthesized and studied for its binding affinity for a variety of anions by 1H-NMR, UV-Vis and colorimetric techniques in DMSO-d6 and DMSO, respectively. The results from titration studies suggest that the receptor forms a 1:2 complex with each of the anions used via hydrogen bonding interactions and exhibits strong selectivity for fluoride among halides, showing the binding affinity in the order of fluoride > chloride > bromide > iodide; meanwhile, it displays moderate selectivity for acetate among oxoanions, showing the binding affinity in the order of acetate > dihydrogen phosphate > bicarbonate > hydrogen sulfate > nitrate. Colorimetric studies of L for anions in DMSO reveal that the receptor is capable of detecting fluoride, acetate, bicarbonate and dihydrogen phosphate, displaying a visible color change in the presence of the respective anions.
      Citation: Chemosensors
      PubDate: 2021-10-11
      DOI: 10.3390/chemosensors9100287
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 288: Electrical and Humidity-Sensing
           Properties of EuCl2, Eu2O3 and EuCl2/Eu2O3 Blend Films

    • Authors: Pi-Guey Su, Nok-Him Choy
      First page: 288
      Abstract: Impedance-type humidity sensors based on EuCl2, Eu2O3 and EuCl2/Eu2O3 blend films were fabricated. The electrical properties of the pure EuCl2 and Eu2O3 films and EuCl2/Eu2O3 blend film that was blended with different amounts of EuCl2 were investigated as functions of relative humidity. The influences of the EuCl2 to the humidity-sensing properties (sensitivity and linearity) of the EuCl2/Eu2O3 blend film were thus elucidated. The impedance-type humidity sensor that was made of a 7 wt% EuCl2/Eu2O3 blend film exhibited the highest sensitivity, best linearity, a small hysteresis, a fast response time, a small temperature coefficient and long-term stability. The complex impedance plots were used to elucidate the role of ions in the humidity-sensing behavior of the EuCl2/Eu2O3 blend film.
      Citation: Chemosensors
      PubDate: 2021-10-11
      DOI: 10.3390/chemosensors9100288
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 289: Sensitive Electrochemical Detection of
           Bioactive Molecules (Hydrogen Peroxide, Glucose, Dopamine) with
           Perovskites-Based Sensors

    • Authors: Imane Boubezari, Ali Zazoua, Abdelhamid Errachid, Nicole Jaffrezic-Renault
      First page: 289
      Abstract: Perovskite-modified electrodes have received increasing attention in the last decade, due to their electrocatalytic properties to undergo the sensitive and selective detection of bioactive molecules, such as hydrogen peroxide, glucose, and dopamine. In this review paper, different types of perovskites involved for their electrocatalytic properties are described, and the proposed mechanism of detection is presented. The analytical performances obtained for different electroactive molecules are listed and compared with those in terms of the type of perovskite used, its nanostructuration, and its association with other conductive nanomaterials. The analytical performance obtained with perovskites is shown to be better than those of Ni and Co oxide-based electrochemical sensors. Main trends and future challenges for enlarging and improving the use of perovskite-based electrochemical sensors are then discussed.
      Citation: Chemosensors
      PubDate: 2021-10-12
      DOI: 10.3390/chemosensors9100289
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 290: Mercaptosuccinic-Acid-Functionalized Gold
           Nanoparticles for Highly Sensitive Colorimetric Sensing of Fe(III) Ions

    • Authors: Nadezhda S. Komova, Kseniya V. Serebrennikova, Anna N. Berlina, Svetlana M. Pridvorova, Anatoly V. Zherdev, Boris B. Dzantiev
      First page: 290
      Abstract: The development of reliable and highly sensitive methods for heavy metal detection is a critical task for protecting the environment and human health. In this study, a qualitative colorimetric sensor that used mercaptosuccinic-acid-functionalized gold nanoparticles (MSA-AuNPs) to detect trace amounts of Fe(III) ions was developed. MSA-AuNPs were prepared using a one-step reaction, where mercaptosuccinic acid (MSA) was used for both stabilization, which was provided by the presence of two carboxyl groups, and functionalization of the gold nanoparticle (AuNP) surface. The chelating properties of MSA in the presence of Fe(III) ions and the concentration-dependent aggregation of AuNPs showed the effectiveness of MSA-AuNPs as a sensing probe with the use of an absorbance ratio of A530/A650 as an analytical signal in the developed qualitative assay. Furthermore, the obvious Fe(III)-dependent change in the color of the MSA-AuNP solution from red to gray-blue made it possible to visually assess the metal content in a concentration above the detection limit with an assay time of less than 1 min. The detection limit that was achieved (23 ng/mL) using the proposed colorimetric sensor is more than 10 times lower than the maximum allowable concentration for drinking water defined by the World Health Organization (WHO). The MSA-AuNPs were successfully applied for Fe(III) determination in tap, spring, and drinking water, with a recovery range from 89.6 to 126%. Thus, the practicality of the MSA-AuNP-based sensor and its potential for detecting Fe(III) in real water samples were confirmed by the rapidity of testing and its high sensitivity and selectivity in the presence of competing metal ions.
      Citation: Chemosensors
      PubDate: 2021-10-14
      DOI: 10.3390/chemosensors9100290
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 291: Sensing Methods for Hazardous Phenolic
           Compounds Based on Graphene and Conducting Polymers-Based Materials

    • Authors: Hazwani Suhaila Hashim, Yap Wing Fen, Nur Alia Sheh Omar, Nurul Illya Muhamad Fauzi
      First page: 291
      Abstract: It has been known for years that the phenolic compounds are able to exert harmful effects toward living organisms including humans due to their high toxicity. Living organisms were exposed to these phenolic compounds as they were released into the environment as waste products from several fast-growing industries. In this regard, tremendous efforts have been made by researchers to develop sensing methods for the detection of these phenolic compounds. Graphene and conducting polymers-based materials have arisen as a high potential sensing layer to improve the performance of the developed sensors. Henceforth, this paper reviews the existing investigations on graphene and conducting polymer-based materials incorporated with various sensors that aimed to detect hazardous phenolic compounds, i.e., phenol, 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol, 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, and 2,4-dimethylphenol. The whole picture and up-to-date information on the graphene and conducting polymers-based sensors are arranged in systematic chronological order to provide a clearer insight in this research area. The future perspectives of this study are also included, and the development of sensing methods for hazardous phenolic compounds using graphene and conducting polymers-based materials is expected to grow more in the future.
      Citation: Chemosensors
      PubDate: 2021-10-14
      DOI: 10.3390/chemosensors9100291
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 292: Off-Grid Electrical Cell Lysis
           Microfluidic Device Utilizing Thermoelectricity and Thermal Radiation

    • Authors: Duong-Duy Duong, Nae-Yoon Lee
      First page: 292
      Abstract: Microfluidic devices have enormous potential and a wide range of applications. However, most applications end up as chip-in-a-lab systems because of power source constraints. This work focuses on reducing the reliance on the power network and expanding on the concept of a lab-on-a-chip for microfluidic devices. A cellulose-based radiator to reflect infrared (IR) radiation with wavelengths within the atmospheric window (8–13 µm) into outer space was fabricated. This process lowered the temperature inside the insulated environment. The difference in temperature was used to power a thermoelectric generator (TEG) and generate an electric current. This electric current was run through a DC-DC transformer to increase the voltage before being used to perform electrical cell lysis with a microfluidic device. This experimental setup successfully achieved 90% and 50% cell lysis efficiencies in ideal conditions and in field tests, respectively. This work demonstrated the possibility of utilizing the unique characteristics of a microfluidic device to perform an energy-intensive assay with minimal energy generated from a TEG and no initial power input for the system. The TEG system also required less maintenance than solar, wind, or hydroelectricity. The IR radiation process naturally allows for more dynamic working conditions for the entire system.
      Citation: Chemosensors
      PubDate: 2021-10-14
      DOI: 10.3390/chemosensors9100292
      Issue No: Vol. 9, No. 10 (2021)
  • Chemosensors, Vol. 9, Pages 293: Rapid Algae Identification and
           Concentration Prediction Based on Discrete Excitation Fluorescence Spectra

    • Authors: Shihan Shan, Xiaoping Wang, Zhuoyun Xu, Mengmeng Tong
      First page: 293
      Abstract: In this paper, an algal identification and concentration determination method based on discrete excitation fluorescence spectra is proposed for online algae identification and concentration prediction. The discrete excitation fluorescence spectra of eight species of harmful algae from four algal categories were assessed. After determining typical excitation wavelengths according to the distribution of photosynthetic pigments and eliminating strongly correlated wavelengths by applying the hierarchical clustering, seven characteristic excitation wavelengths (405, 435, 470, 490, 535, 555, and 590 nm) were selected. By adding the ratios between feature points (435 and 470 nm, 470 and 490 nm, as well as 535 and 555 nm), standard feature spectra were established for classification. The classification accuracy in pure samples exceeded 95%, and that of dominant algae species in a mixed sample was 77.4%. Prediction of algae concentration was achieved by establishing linear regression models between fluorescence intensity at seven characteristic excitation wavelengths and concentrations. All models performed better at low concentrations, not exceeding the threshold concentration of red tide algae outbreak, which provides a proximate cell density of dominant algal species.
      Citation: Chemosensors
      PubDate: 2021-10-18
      DOI: 10.3390/chemosensors9100293
      Issue No: Vol. 9, No. 10 (2021)
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