Subjects -> CHEMISTRY (Total: 928 journals)
    - ANALYTICAL CHEMISTRY (59 journals)
    - CHEMISTRY (661 journals)
    - CRYSTALLOGRAPHY (23 journals)
    - ELECTROCHEMISTRY (28 journals)
    - INORGANIC CHEMISTRY (45 journals)
    - ORGANIC CHEMISTRY (47 journals)
    - PHYSICAL CHEMISTRY (65 journals)

CHEMISTRY (661 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
Accounts of Materials Research     Hybrid Journal   (Followers: 1)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 30)
ACS Applied Polymer Materials     Hybrid Journal   (Followers: 9)
ACS Catalysis     Hybrid Journal   (Followers: 51)
ACS Chemical Neuroscience     Hybrid Journal   (Followers: 23)
ACS Combinatorial Science     Hybrid Journal   (Followers: 21)
ACS Environmental Au     Open Access   (Followers: 11)
ACS Macro Letters     Hybrid Journal   (Followers: 25)
ACS Materials Letters     Open Access   (Followers: 3)
ACS Medicinal Chemistry Letters     Hybrid Journal   (Followers: 41)
ACS Nano     Hybrid Journal   (Followers: 187)
ACS Photonics     Hybrid Journal   (Followers: 14)
ACS Symposium Series     Full-text available via subscription   (Followers: 3)
ACS Synthetic Biology     Hybrid Journal   (Followers: 31)
Acta Chemica Malaysia     Open Access  
Acta Chimica Slovaca     Open Access   (Followers: 2)
Acta Chimica Slovenica     Open Access   (Followers: 2)
Acta Chromatographica     Full-text available via subscription   (Followers: 7)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 8)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 7)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 10)
Adsorption Science & Technology     Open Access   (Followers: 7)
Advanced Electronic Materials     Hybrid Journal   (Followers: 7)
Advanced Functional Materials     Hybrid Journal   (Followers: 72)
Advanced Journal of Chemistry, Section A     Open Access   (Followers: 3)
Advanced Journal of Chemistry, Section B     Open Access   (Followers: 1)
Advanced Science Focus     Free   (Followers: 6)
Advanced Theory and Simulations     Hybrid Journal   (Followers: 2)
Advanced Therapeutics     Hybrid Journal   (Followers: 1)
Advances in Chemical Engineering and Science     Open Access   (Followers: 111)
Advances in Chemical Science     Open Access   (Followers: 51)
Advances in Chemistry     Open Access   (Followers: 34)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 15)
Advances in Environmental Chemistry     Open Access   (Followers: 11)
Advances in Enzyme Research     Open Access   (Followers: 10)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 33)
Advances in Nanoparticles     Open Access   (Followers: 17)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Polymer Science     Hybrid Journal   (Followers: 51)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 18)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Sample Preparation     Open Access   (Followers: 9)
Advances in Science and Technology     Full-text available via subscription   (Followers: 16)
Aerosol Science and Engineering     Hybrid Journal  
African Journal of Chemical Education     Open Access   (Followers: 5)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 6)
Aggregate     Open Access   (Followers: 1)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Al-Kimia : Jurnal Penelitian Sains Kimia     Open Access  
Alchemy : Journal of Chemistry     Open Access   (Followers: 4)
Alchemy : Jurnal Penelitian Kimia     Open Access  
Alotrop     Open Access  
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 44)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 20)
American Journal of Chemistry     Open Access   (Followers: 37)
American Journal of Plant Physiology     Open Access   (Followers: 9)
Analyst     Hybrid Journal   (Followers: 35)
Analytical Science Advances     Open Access   (Followers: 1)
Angewandte Chemie     Hybrid Journal   (Followers: 144)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 236)
Annales Universitatis Mariae Curie-Sklodowska, sectio AA – Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 6)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 4)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 5)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 13)
Antiviral Chemistry and Chemotherapy     Open Access   (Followers: 1)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 31)
Arabian Journal of Chemistry     Open Access   (Followers: 4)
ARKIVOC     Open Access   (Followers: 1)
Asian Journal of Applied Chemistry Research     Open Access   (Followers: 1)
Asian Journal of Biochemistry     Open Access   (Followers: 2)
Asian Journal of Chemical Sciences     Open Access  
Asian Journal of Chemistry and Pharmaceutical Sciences     Open Access  
Asian Journal of Physical and Chemical Sciences     Open Access   (Followers: 2)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 7)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Hybrid Journal   (Followers: 203)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 5)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access  
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 2)
Biomacromolecules     Hybrid Journal   (Followers: 23)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 3)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 84)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 61)
Bioorganic Chemistry     Hybrid Journal   (Followers: 7)
Biopolymers     Hybrid Journal   (Followers: 15)
Biosensors     Open Access   (Followers: 3)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 3)
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: 24)
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: 1)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 11)
Canadian Mineralogist     Full-text available via subscription   (Followers: 5)
Carbohydrate Polymer Technologies and Applications     Open Access  
Carbohydrate Polymers     Hybrid Journal   (Followers: 9)
Carbohydrate Research     Hybrid Journal   (Followers: 23)
Carbon     Hybrid Journal   (Followers: 65)
Carbon Capture Science & Technology     Open Access  
Carbon Trends     Open Access   (Followers: 5)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 9)
Catalysis Science and Technology     Hybrid Journal   (Followers: 9)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 4)
Catalysts     Open Access   (Followers: 11)
Cell Reports Physical Science     Open Access  
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
Chem     Hybrid Journal   (Followers: 1)
Chem Catalysis     Hybrid Journal  
ChemBioEng Reviews     Full-text available via subscription   (Followers: 3)
ChemCatChem     Hybrid Journal   (Followers: 7)
Chemical and Engineering News     Free   (Followers: 22)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Hybrid Journal   (Followers: 79)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 26)
Chemical Physics Impact     Full-text available via subscription  
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 4)
Chemical Research in Toxicology     Hybrid Journal   (Followers: 22)
Chemical Reviews     Hybrid Journal   (Followers: 178)
Chemical Science     Open Access   (Followers: 41)
Chemical Science International Journal     Open Access  
Chemical Technology     Open Access   (Followers: 75)
Chemical Thermodynamics and Thermal Analysis     Open Access   (Followers: 2)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 4)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 40)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 17)
ChemInform     Hybrid Journal   (Followers: 5)
Chemistry     Open Access  
Chemistry & Biodiversity     Hybrid Journal   (Followers: 7)
Chemistry & Industry     Full-text available via subscription   (Followers: 6)
Chemistry - A European Journal     Hybrid Journal   (Followers: 119)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 19)
Chemistry Africa : A Journal of the Tunisian Chemical Society     Hybrid Journal  
Chemistry and Materials Research     Open Access   (Followers: 18)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 6)
Chemistry Education Review     Open Access   (Followers: 1)
Chemistry in Education     Open Access   (Followers: 3)
Chemistry Letters     Full-text available via subscription   (Followers: 42)
Chemistry of Heterocyclic Compounds     Hybrid Journal   (Followers: 4)
Chemistry of Materials     Hybrid Journal   (Followers: 166)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 10)
Chemistry World     Hybrid Journal   (Followers: 20)
Chemistry-Didactics-Ecology-Metrology     Open Access  
ChemistryOpen     Open Access   (Followers: 1)
ChemistrySelect     Hybrid Journal  
Chemistry–Methods     Open Access   (Followers: 1)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
ChemNanoMat     Hybrid Journal   (Followers: 1)
Chemoecology     Hybrid Journal   (Followers: 2)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 13)
Chemosensors     Open Access   (Followers: 1)
ChemPhotoChem     Hybrid Journal  
ChemPhysChem     Hybrid Journal   (Followers: 12)
ChemPhysMater     Full-text available via subscription  
ChemPlusChem     Hybrid Journal   (Followers: 2)
Chempublish Journal     Open Access  
ChemSystemsChem     Hybrid Journal   (Followers: 1)
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: 9)
Chromatographia     Hybrid Journal   (Followers: 21)
Chromatography     Open Access   (Followers: 2)
Chromatography Research International     Open Access   (Followers: 4)
Ciencia     Open Access  
Clay Minerals     Hybrid Journal   (Followers: 8)
Cogent Chemistry     Open Access   (Followers: 3)
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 6)
Colloids and Interfaces     Open Access  
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 8)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 2)
Combustion Science and Technology     Hybrid Journal   (Followers: 26)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 1)
Communications Chemistry     Open Access   (Followers: 2)
Communications Materials     Open Access  
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comptes Rendus : Chimie     Open Access  
Comptes Rendus : Physique     Open Access   (Followers: 3)

        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  [84 journals]
  • Chemosensors, Vol. 10, Pages 234: Quantification of a COVID-19 Antibody
           Assay Using a Lateral Flow Test and a Cell Phone

    • Authors: Pearl Thompson, Ana Lívia de Carvalho Bovolato, Gisela Ibáñez-Redín, Alexandre G. Brolo
      First page: 234
      Abstract: Although several biomedical assays have been developed to screen for antibodies against SARS-CoV-2, very few can be completed without drawing blood. We developed a rapid lateral flow screening tool that used saliva samples and yielded rapid results that could be quantified using a cell phone. This assay provided the sensitive detection of IgG antibodies against SARS-CoV-2 within 10 min. We started by synthesising, modifying, and characterising gold nanoparticles. Using these particles as a coloured label, we developed a lateral flow strip made of nitrocellulose, glass fibre, and cellulose material. We quantified our visual results using pictures acquired with a cell phone and calculated a limit of detection of 4 ng/mL of antibodies against the SARS-CoV-2 spike protein.
      Citation: Chemosensors
      PubDate: 2022-06-21
      DOI: 10.3390/chemosensors10070234
      Issue No: Vol. 10, No. 7 (2022)
  • Chemosensors, Vol. 10, Pages 235: YAP/TAZ Promote Fibrotic Activity in
           Human Trabecular Meshwork Cells by Sensing Cytoskeleton Structure

    • Authors: Shan Huang, Zhicheng Liu, Xiuqing Qian, Lin Li, Haixia Zhang, Shanshan Li, Zhicheng Liu
      First page: 235
      Abstract: Trabecular meshwork (TM) is the main channel of aqueous humor (AH) outflow and the crucial tissue responsible for intraocular pressure (IOP) regulation. The aberrant fibrotic activity of human TM (HTM) cells is thought to be partially responsible for the increased resistance to AH outflow and elevated IOP. This study aimed to identify the TM cell fibrotic activity biomarker and illustrate the mechanisms of fibrotic activity regulation in HTM cells. We used TGFβ2-treated HTM cells and detected the changes in the cytoskeletal structure, the Yes-associated protein (YAP) and its transcriptional co-activator with PDZ-binding domain (TAZ) activation, and the expression levels of the fibrosis-related proteins Collagen I and α-SMA in HTM cells by immunofluorescence staining or western bolt analyses. The expression of YAP was inhibited using siRNA transfection. The results showed that the expression levels of YAP/TAZ and the fibrosis-related proteins Collagen I and α-SMA in HTM cells were elevated under TGF-β2 treatment, which was correlated with the structural change of the cellular F-actin cytoskeleton. Furthermore, the inhibition of YAP decreased the expression of connective tissue growth factor (CTGF), Collagen I, and α-SMA in HTM cells. These findings demonstrate that YAP/TAZ are potential biomarkers in evaluating the TM cell fibrotic activity, and it could sense cytoskeletal structure cues and regulate the fibrotic activity of TM cells.
      Citation: Chemosensors
      PubDate: 2022-06-21
      DOI: 10.3390/chemosensors10070235
      Issue No: Vol. 10, No. 7 (2022)
  • Chemosensors, Vol. 10, Pages 236: Pd-GaSe and Pd3-GaSe Monolayers: Two
           Promising Candidates for Detecting Dissolved Gases in Transformer Oil

    • Authors: Tianyu Hou, Wen Zeng, Qu Zhou
      First page: 236
      Abstract: In this paper, the adsorption behaviors of three gases (H2, CO, and C2H2) decomposed by the transformer oil on Pd-GaSe and Pd3-GaSe monolayers were calculated by density functional theory. Compared with Pd single-atom doping, Pd3 cluster doping changed the original structure and charge distribution to a greater extent, and more obviously improved the conductivity. According to the analysis of adsorption energy, charge transfer and deformation charge density, the results show that the two doped structures have better adsorption performance for the three gas molecules (H2, CO, and C2H2) than the intrinsic GaSe monolayer. Compared with Pd-GaSe, Pd3-GaSe showed stronger adsorption property for the three gases. Analysis of frontier molecular orbitals and recovery characteristics shows that Pd3-GaSe can be used as an ideal gas sensitive material for H2 detection because of its good desorption properties and obvious conductivity changes. Pd-GaSe can be used as a disposable resistive sensor for CO. Pd3-GaSe is a kind of sensing material suitable for disposable resistance sensors for CO and C2H2. These two doped structures have great application potential in gas adsorption and detection, and provide indications for further study on gas sensor detection by means of metal-doped GaSe monolayer.
      Citation: Chemosensors
      PubDate: 2022-06-21
      DOI: 10.3390/chemosensors10070236
      Issue No: Vol. 10, No. 7 (2022)
  • Chemosensors, Vol. 10, Pages 237: Hybrid Nanocomposites of Plasmonic Metal
           Nanostructures and 2D Nanomaterials for Improved Colorimetric Detection

    • Authors: Caterina Serafinelli, Alessandro Fantoni, Elisabete C. B. A. Alegria, Manuela Vieira
      First page: 237
      Abstract: Plasmonic phenomena and materials have been extensively investigated for a long time and gained popularity in the last few years, finding in the design of the biosensors platforms promising applications offering devices with excellent performances. Hybrid systems composed of graphene, or other 2D materials, and plasmonic metal nanostructures present extraordinary optical properties originated from the synergic connection between plasmonic optical effects and the unusual physicochemical properties of 2D materials, thus improving their application in a broad range of fields. In this work, firstly, an overview of the structures and properties of 2D nanomaterials will be provided along with the physics of surface plasmon resonance and localized surface plasmon resonance. In the second part of the work, some examples of colorimetric biosensors exploiting the outstanding properties of hybrids nanocomposites will be presented. Finally, concluding perspectives on the actual status, challenges, and future directions in plasmonic sensing biosensing will be provided. Special emphasis will be given to how this technology can be used to support digitalization and virtualization in pandemic handling.
      Citation: Chemosensors
      PubDate: 2022-06-22
      DOI: 10.3390/chemosensors10070237
      Issue No: Vol. 10, No. 7 (2022)
  • Chemosensors, Vol. 10, Pages 238: High-Performance Liquid
           Chromatography–Diode Array Detection Combined with Chemometrics for
           Simultaneous Quantitative Analysis of Five Active Constituents in a
           Chinese Medicine Formula Wen-Qing-Yin

    • Authors: Jun-Chen Chen, Hai-Long Wu, Tong Wang, Ming-Yue Dong, Yue Chen, Ru-Qin Yu
      First page: 238
      Abstract: In this work, a simple analytical strategy combining high-performance liquid chromatography–diode array detection (HPLC-DAD) and the chemometric method was developed for the simultaneous quantification of 5-hydroxymethyl-2-furfural (HMF), paeoniflorin (PAE), ferulic acid (FER), baicalin (BAI), and berberine (BER) in a Chinese medicine formula Wen-Qing-Yin (WQY). The alternating trilinear decomposition (ATLD) algorithm and alternating trilinear decomposition assisted multivariate curve resolution (ATLD-MCR) algorithm were used to realize the separation and rapid determination of five target analytes under the presence of time shifts, solvent peaks, peak overlaps, and unknown interferences. All analytes were eluted within 10 min and the linear correlation coefficients of calibration sets were between 0.9969 and 0.9996. In addition, the average recoveries of the five active compounds obtained by ATLD and ATLD-MCR analysis were in the range of 91.8–112.5% and 88.6–101.6%, respectively. For investigating the accuracy and reliability of the proposed method, figures of merit including limit of detection (LOD), limit of quantitation (LOQ), sensitivity (SEN), and selectivity (SEL) were calculated. The proposed analytical strategy has the advantages of being fast, simple, and sensitive, and can be used for the qualitative and quantitative analysis of WQY, providing a feasible option for the quality monitoring of the traditional Chinese medicine formula.
      Citation: Chemosensors
      PubDate: 2022-06-23
      DOI: 10.3390/chemosensors10070238
      Issue No: Vol. 10, No. 7 (2022)
  • Chemosensors, Vol. 10, Pages 239: Machine Learning-Based Radon Monitoring

    • Authors: Diego Valcarce, Alberto Alvarellos, Juan Ramón Rabuñal, Julián Dorado, Marcos Gestal
      First page: 239
      Abstract: Radon (Rn) is a biological threat to cells due to its radioactivity. It is capable of penetrating the human body and damaging cellular DNA, causing mutations and interfering with cellular dynamics. Human exposure to high concentrations of Rn should, therefore, be minimized. The concentration of radon in a room depends on numerous factors, such as room temperature, humidity level, existence of air currents, natural grounds of the buildings, building structure, etc. It is not always possible to change these factors. In this paper we propose a corrective measure for reducing indoor radon concentrations by introducing clean air into the room through forced ventilation. This cannot be maintained continuously because it generates excessive noise (and costs). Therefore, a system for predicting radon concentrations based on Machine Learning has been developed. Its output activates the fan control system when certain thresholds are reached.
      Citation: Chemosensors
      PubDate: 2022-06-24
      DOI: 10.3390/chemosensors10070239
      Issue No: Vol. 10, No. 7 (2022)
  • Chemosensors, Vol. 10, Pages 240: Voltammetric Electrochemical Behavior of
           Carbon Paste Electrode Containing Intrinsic Silver for Determination of

    • Authors: Maša Buljac, Denis Krivić, Ivana Škugor Rončević, Nives Vladislavić, Marijo Buzuk
      First page: 240
      Abstract: In this paper, the electrochemical behavior of cysteine is described, using carbon paste electrodes (CPEs) modified with ternary silver-copper sulfide containing intrinsic silver at two pH values (pH 3 and 5). Experiments have revealed that presence of cysteine has a large impact on the electrochemical behavior of modified CPEs. Observed phenomena take place in solution, as well as at the surface of the modified CPEs, and can be applied for electroanalytical purposes. Based on the electrochemical behavior observed in the examined system, differential pulse voltammetry (DPV) was selected as an electroanalytical method for determination of cysteine. The effects of the various parameters on the electroanalytical signal, such as the amount of electroactive material, electroanalytical parameters, pH etc., were investigated using differential pulse voltammograms. The results indicated that electrochemical signal characterized with well-defined cathodic peak at 0.055 V vs. Ag/AgCl (3 M) in acetic buffer solution at pH 5 can be used for indirect electrochemical determination of cysteine. The optimization procedure revealed that the most sensitive and stabile electrode was that containing 5% modifier. The DPV response of the electrode, in the presence of cysteine, showed two different linear concentration ranges of 0.1 to 2.5 μM, and 5.6 to 28 μM. The explanation of the origin of two linear ranges is proposed. The lower concentration range was characterized by remarkable sensitivity of the 11.78 μA μM–1, owing to the chosen indirect method of determination. The calculated limit of detection (LOD), as well as limit of quantification (LOQ) were 0.032 and 0.081 μM, respectively. The influence of interfering agents on the electroanalytical response was examined, and low or no interference on the DPVs was observed. The proposed method was validated and applied for the determination of cysteine in pharmaceutical preparations with satisfactory recoveries in the range of 97 to 101.7%.
      Citation: Chemosensors
      PubDate: 2022-06-24
      DOI: 10.3390/chemosensors10070240
      Issue No: Vol. 10, No. 7 (2022)
  • Chemosensors, Vol. 10, Pages 241: Broadband Dielectric Spectroscopic
           Detection of Ethanol: A Side-by-Side Comparison of ZnO and HKUST-1 MOFs as
           Sensing Media

    • Authors: Papa K. Amoah, Zeinab Mohammed Hassan, Pengtao Lin, Engelbert Redel, Helmut Baumgart, Yaw S. Obeng
      First page: 241
      Abstract: The most common gas sensors are based on chemically induced changes in electrical resistivity and necessarily involve making imperfect electrical contacts to the sensing materials, which introduce errors into the measurements. We leverage thermal- and chemical-induced changes in microwave propagation characteristics (i.e., S-parameters) to compare ZnO and surface-anchored metal–organic-framework (HKUST-1 MOF) thin films as sensing materials for detecting ethanol vapor, a typical volatile organic compound (VOC), at low temperatures. We show that the microwave propagation technique can detect ethanol at relatively low temperatures (<100 °C), and afford new mechanistic insights that are inaccessible with the traditional dc-resistance-based measurements. In addition, the metrological technique avoids the inimical measurand distortions due to parasitic electrical effects inherent in the conductometric volatile organic compound detection.
      Citation: Chemosensors
      PubDate: 2022-06-25
      DOI: 10.3390/chemosensors10070241
      Issue No: Vol. 10, No. 7 (2022)
  • Chemosensors, Vol. 10, Pages 242: Study on Microdamage Quantitative
           Analysis of Cd and Pb in Leaves by Laser Induced Breakdown Spectroscopy

    • Authors: Li Fang, Mingjun Ma, Gaofang Yin, Xiaowei Chen, Fuqiang Chen, Nanjing Zhao
      First page: 242
      Abstract: Recent years, research on the detection of heavy metals in Traditional Chinese Medicine (TCM) by laser induced breakdown spectroscopy (LIBS) have gradually increased. Current main methods of establishing calibration curve are based on grounding and pelleting of the tested samples. Although compared to digested samples, grounding and pelleting of the sample is already quite simple, it cannot fully reflect the advantages of LIBS: rapid analysis, and, also, the uneven distribution of heavy metals in the TCM is ignored. In order to avoid grinding and pelleting sample to be tested, and to achieve microdamage quantitative analysis by LIBS, this article presents a new method for establishing calibration curve. The experiment in this paper based on a study with Cd and Pb in leaves of laurel. The preparation of calibration samples and the establishment of calibration methods for microdamage quantitative analysis were presented, which proved the feasibility of microdamage quantitative analysis by LIBS. The square of the linear relationship coefficient R of Pb was higher than 0.82. This method provides a guiding method for the rapid quantitative analysis of heavy metals in TCM by LIBS.
      Citation: Chemosensors
      PubDate: 2022-06-25
      DOI: 10.3390/chemosensors10070242
      Issue No: Vol. 10, No. 7 (2022)
  • Chemosensors, Vol. 10, Pages 198: α-Glucosidase-Mediated Glucometer
           Readout for Portable Monitoring of Acarbose and Migliol

    • Authors: Hao Zhang, Feng-Qing Yang
      First page: 198
      Abstract: The α-glucosidase inhibitor is regarded as one of the most important drugs for the treatment of diabetes, which can control postprandial blood glucose levels via prolonging the carbohydrate digestion time and retarding the carbohydrates’ absorption. The present work aims to establish a facile bioanalytical method, based on α-glucosidase catalyzing the hydrolysis of 2-O-alpha-D-Glucopyranosyl-L-ascorbic acid (AA-2G), for the quantification of acarbose and migliol using a personal glucose meter (PGM). The hydrolysis products (ascorbic acid and glucose) can trigger the reduction of K3[Fe(CN)6] to K4[Fe(CN)6] in the glucose test strips, which results in the formation of the electron, which can be measured by PGM. Thus, ascorbic acid and glucose can be simultaneously measured by a simplified and miniaturized PGM method. However, the products produced by the hydrolysis of AA-2G will be decreased after the addition of acarbose or migliol to inhibit the activity of α-glucosidase, thereby resulting in a decreased PGM readout. After being incubated with α-glucosidase for 3.0 min and enzymatic reaction for 5.0 min, the quantitative detection of acarbose and migliol can be achieved within the ranges of 1.0–30.0 μM with the limit of detection of 0.33 μM and 3.0–33.3 μM with the limit of detection of 1.0 μM, respectively. IC50 values for acarbose and migliol are calculated to be 10.0 μM and 16.0 μM, respectively. The recoveries of the acarbose and migliol spiked with three different concentrations (final concentrations of 10.0, 20.0, and 30.0 μM) in human serum sample are in the ranges of 89.6–114.5% and 93.9–106.5%, respectively. These results demonstrate that the developed PGM method may be useful in future studies on therapeutic monitoring of acarbose and migliol.
      Citation: Chemosensors
      PubDate: 2022-05-24
      DOI: 10.3390/chemosensors10060198
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 199: State of the Art of Chemosensors in a
           Biomedical Context

    • Authors: Erich Kny, Ciril Reiner-Rozman, Jakub Dostalek, Achim-Walter Hassel, Christa Nöhammer, Florian Pfaffeneder-Mantai, Sabine Szunerits, Viktoria Weber, Wolfgang Knoll, Christoph Kleber
      First page: 199
      Abstract: Healthcare is undergoing large transformations, and it is imperative to leverage new technologies to support the advent of personalized medicine and disease prevention. It is now well accepted that the levels of certain biological molecules found in blood and other bodily fluids, as well as in exhaled breath, are an indication of the onset of many human diseases and reflect the health status of the person. Blood, urine, sweat, or saliva biomarkers can therefore serve in early diagnosis of diseases such as cancer, but also in monitoring disease progression, detecting metabolic disfunctions, and predicting response to a given therapy. For most point-of-care sensors, the requirement that patients themselves can use and apply them is crucial not only regarding the diagnostic part, but also at the sample collection level. This has stimulated the development of such diagnostic approaches for the non-invasive analysis of disease-relevant analytes. Considering these timely efforts, this review article focuses on novel, sensitive, and selective sensing systems for the detection of different endogenous target biomarkers in bodily fluids as well as in exhaled breath, which are associated with human diseases.
      Citation: Chemosensors
      PubDate: 2022-05-24
      DOI: 10.3390/chemosensors10060199
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 200: An In Vitro HL-1 Cardiomyocyte-Based
           Olfactory Biosensor for Olfr558-Inhibited Efficiency Detection

    • Authors: Qunchen Yuan, Chunlian Qin, Saisai Zhang, Jianguo Wu, Yong Qiu, Changming Chen, Liquan Huang, Ping Wang, Deming Jiang, Liujing Zhuang
      First page: 200
      Abstract: Some short-chain fatty acids with a pungent or unpleasant odor are important components of human body odor. These malodors severely threaten human health. The antagonists of malodors would help to improve odor perception by affecting the interaction between odors and their receptors. However, the traditional odor detection and analysis methods, such as MOS, electrochemical, conductive polymer gas sensors, or chromatography-mass spectrometry are not suitable for screening the antagonists since they are unable to detect the ligand efficacy after odor-receptor binding. In this study, RT-PCR results showed that HL-1 cardiomyocytes endogenously express the olfactory receptor 558 (Olfr558) which can be activated by several malodorous short-chain fatty acids. Therefore, an in vitro HL-1 cardiomyocyte-based olfactory biosensor (HCBO-biosensor) was developed by combining cardiomyocytes and microelectrode array (MEA) chips for screening the potential antagonists of the Olfr558. Firstly, it showed that the biosensor specifically responded to ligands of Olfr558 through odor stimulation experiments. Then, an odor response model of HL-1 cardiomyocytes was constructed by a ligand of Olfr558 (isovaleric acid). The response feature of the in vitro HCBO-biosensor to individual odors and mixtures with a potential antagonist (citral or β-damascenone) were extracted and compared. Finally, the Olfr558-inhibited efficiency was indirectly detected by comparing the half-maximal inhibitory concentration of isovaleric acid. The results showed that β-damascenone greatly inhibited Olfr558 while citral showed no significant inhibitory effect. In conclusion, we built a novel screening method for the antagonists of Olfr558 based on HL-1 cardiomyocytes and the MEA chip which will assist odor-related companies to develop novel antagonists of Olfr558.
      Citation: Chemosensors
      PubDate: 2022-05-24
      DOI: 10.3390/chemosensors10060200
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 201: Polyethylene and Semiconducting Polymer
           Blends for the Fabrication of Organic Field-Effect Transistors: Balancing
           Charge Transport and Stretchability

    • Authors: Piumi Kulatunga, Nastaran Yousefi, Simon Rondeau-Gagné
      First page: 201
      Abstract: Polyethylene is amongst the most used polymers, finding a plethora of applications in our lives owing to its high impact resistance, non-corrosive nature, light weight, cost effectiveness, and easy processing into various shapes from different sizes. Despite these outstanding features, the commodity polymer has been underexplored in the field of organic electronics. This work focuses on the development of new polymer blends based on a low molecular weight linear polyethylene (LPE) derivative with a high-performance diketopyrrolopyrrole-based semiconducting polymer. Physical blending of the polyethylene with semiconducting polymers was performed at ratios varying from 0 to 75 wt.%, and the resulting blends were carefully characterized to reveal their electronic and solid-state properties. The new polymer blends were also characterized to reveal the influence of polyethylene on the mechanical robustness and stretchability of the semiconducting polymer. Overall, the introduction of LPE was shown to have little to no effect on the solid-state properties of the materials, despite some influence on solid-state morphology through phase separation. Organic field-effect transistors prepared from the new blends showed good device characteristics, even at higher ratios of polyethylene, with an average mobility of 0.151 cm2 V−1 s−1 at a 25 wt.% blend ratio. The addition of polyethylene was shown to have a plasticizing effect on the semiconducting polymers, helping to reduce crack width upon strain and contributing to devices accommodating more strain without suffering from decreased performance. The new blends presented in this work provide a novel platform from which to access more mechanically robust organic electronics and show promising features for the utilization of polyethylene for the solution processing of advanced semiconducting materials toward novel soft electronics and sensors.
      Citation: Chemosensors
      PubDate: 2022-05-24
      DOI: 10.3390/chemosensors10060201
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 202: An Enzyme-Based Interdigitated
           Electrode-Type Biosensor for Detecting Low Concentrations of H2O2

    • Authors: Farnoosh Vahidpour, Yousef Alghazali, Sevilay Akca, Gregor Hommes, Michael J. Schöning
      First page: 202
      Abstract: This work introduces a novel method for the detection of H2O2 vapor/aerosol of low concentrations, which is mainly applied in the sterilization of equipment in medical industry. Interdigitated electrode (IDE) structures have been fabricated by means of microfabrication techniques. A differential setup of IDEs was prepared, containing an active sensor element (active IDE) and a passive sensor element (passive IDE), where the former was immobilized with an enzymatic membrane of horseradish peroxidase that is selective towards H2O2. Changes in the IDEs’ capacitance values (active sensor element versus passive sensor element) under H2O2 vapor/aerosol atmosphere proved the detection in the concentration range up to 630 ppm with a fast response time (<60 s). The influence of relative humidity was also tested with regard to the sensor signal, showing no cross-sensitivity. The repeatability assessment of the IDE biosensors confirmed their stable capacitive signal in eight subsequent cycles of exposure to H2O2 vapor/aerosol. Room-temperature detection of H2O2 vapor/aerosol with such miniaturized biosensors will allow a future three-dimensional, flexible mapping of aseptic chambers and help to evaluate sterilization assurance in medical industry.
      Citation: Chemosensors
      PubDate: 2022-05-26
      DOI: 10.3390/chemosensors10060202
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 203: Kinetics of Odorant Recognition with a
           Graphene-Based Olfactory Receptor Mimicry

    • Authors: Caroline Bonazza, Klaus Bonazza
      First page: 203
      Abstract: Malaria vector mosquito species rely on a handful of specific pheromones for mating; one of them, sulcatone (6-methyl-5-hepten-2-one), is also found in human exudation. Therefore, a complete understanding of the insect’s olfaction, and rapid real-time methods for odorant detection, are required. Here, we mimic the odorant recognition of the nerve cells of an insect’s antenna with a synthetic graphene-based bio-electro-interfacial odorant receptor. By this means, we obtain the kinetics of the genuine odorant recognition reaction and compare them to electro-antennogram data that represent the more complex scenario of a living insect. The odorant-binding proteins OBP 9A and 9B only associate with their ligands weakly, showing KDs of between 2.1 mM and 3 mM, while the binding kinetics of OBP proteins depend on the structural feature of a cystine knot and are modulated by the local milieu within a protein-aided enhancement zone.
      Citation: Chemosensors
      PubDate: 2022-05-27
      DOI: 10.3390/chemosensors10060203
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 204: The Usefulness of Autoradiography for
           DNA Repair Proteins Activity Detection in the Cytoplasm towards
           Radiolabeled Oligonucleotides Containing

    • Authors: Karolina Boguszewska, Bolesław T. Karwowski, Julia Kaźmierczak-Barańska
      First page: 204
      Abstract: Autoradiography of 32P-radiolabeled oligonucleotides is one of the most precise detection methods of DNA repair processes. In this study, autoradiography allowed assessing the activity of proteins in the cytoplasm involved in DNA repair. The cytoplasm is the site of protein biosynthesis but is also a target cellular compartment of synthetic therapeutic oligonucleotide (STO) delivery. The DNA-based drugs may be impaired by radiation-induced lesions, such as clustered DNA lesions (CDL) and/or 5′,8-cyclo-2′-deoxypurines (cdPu). CDL and cdPu may appear in the sequence of STO after irradiation and subsequently impair DNA repair, as shown in previous studies. Hence, the interesting questions are (1) is it safe to combine STO treatment with radiotherapy; (2) are repair proteins active in the cytoplasm; and (3) is their activity different in the cytoplasm than in the nucleus' This unique study examined whether the proteins involved in the DNA repair are affected by the CDL while they are still present in the cytoplasm of xrs5, BJ, and XPC cells. Double-stranded oligonucleotides with bi-stranded CDL were used (containing AP site in one strand and a (5′S) or (5′R) 5′,8-cyclo-2′-deoxyadenosine (cdA) in the other strand located 1 or 4 bp in both directions). The results have shown that the proteins involved in the repair were active in the cytoplasm, but less than in the nucleus. The general trends aligned for cytoplasm and nucleus—lesions located in the 5′-end direction inhibited the course of DNA repair. The combination of STO with radiotherapy should be applied carefully, as unrepaired lesions within STO may impair their therapeutic efficiency.
      Citation: Chemosensors
      PubDate: 2022-05-28
      DOI: 10.3390/chemosensors10060204
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 205: Investigating Organic Vapor Sensing
           Properties of Composite Carbon Nanotube-Zinc Oxide Nanowire

    • Authors: Mostafa Shooshtari, Saeideh Pahlavan, Saeideh Rahbarpour, Hasan Ghafoorifard
      First page: 205
      Abstract: The low operating temperature of nanowire gas sensors along with their high surface-to-volume ratio are two factors that make gas sensors more practical. In this paper, the growth of ZnO nanowires on a vertically aligned CNT forest is reported. The utilized method for ZnO growth was a rapid microwave-assisted hydrothermal route, which facilitates low-temperature and ultra-fast fabrication. Organic vapor sensing properties of fabricated samples were studied in response to different alcoholic vapors at a wide operating temperature range of 25 to 300 °C. Enhancement of the gas response was observed with increasing operating temperature. Moreover, the effect of the ZnO nanowire length on organic vapor sensing properties of CNT-ZnO samples was investigated. Results proved that CNT-ZnO samples with long ZnO wires exhibit higher sensitivity to examined analytes. Different length ZnO nanowires were attained via variation of the microwave exposure time and power. Fabrication parameters were selected based on numerous runs. The length of ZnO synthesized at each distinct run was calculated based on SEM micrographs of the samples.
      Citation: Chemosensors
      PubDate: 2022-05-29
      DOI: 10.3390/chemosensors10060205
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 206: Recent Progresses in NIR-II Luminescent
           Bio/Chemo Sensors Based on Lanthanide Nanocrystals

    • Authors: Tingyu Yang, Jinglei Qin, Jinling Zhang, Lanying Guo, Mu Yang, Xi Wu, Mei You, Hongshang Peng
      First page: 206
      Abstract: Fluorescent bio/chemosensors are widely used in the field of biological research and medical diagnosis, with the advantages of non-invasiveness, high sensitivity, and good selectivity. In particular, luminescent bio/chemosensors, based on lanthanide nanocrystals (LnNCs) with a second near-infrared (NIR-II) emission, have attracted much attention, owing to greater penetration depth, aside from the merits of narrow emission band, abundant emission lines, and long lifetimes. In this review, NIR-II LnNCs-based bio/chemo sensors are summarized from the perspectives of the mechanisms of NIR-II luminescence, synthesis method of LnNCs, strategy of luminescence enhancement, sensing mechanism, and targeted bio/chemo category. Finally, the problems that exist in present LnNCs-based bio/chemosensors are discussed, and the future development trend is prospected.
      Citation: Chemosensors
      PubDate: 2022-05-30
      DOI: 10.3390/chemosensors10060206
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 207: A Ratiometric Selective Fluorescent
           Probe Derived from Pyrene for Cu2+ Detection

    • Authors: Chunwei Yu, Mei Yang, Shuhua Cui, Yuxiang Ji, Jun Zhang
      First page: 207
      Abstract: A novel ratiometric Cu2+-selective probe was rationally constructed based on pyrene derivative. Compared to other tested metal ions, the probe presented the selective recognition for Cu2+ which could be detected by a significant turn-on fluorescent response at 393 nm and 415 nm. Under the optimized conditions, a detection limit of 0.16 μM Cu2+ in aqueous media was found. Besides this, a 1:1 metal–ligand complex was confirmed by MS spectra and Job’s plot experiment, and the binding mode was also studied by 1H NMR experiment. Meanwhile, the fluorescence imaging in living cells was performed to detect Cu2+ with satisfactory results.
      Citation: Chemosensors
      PubDate: 2022-05-31
      DOI: 10.3390/chemosensors10060207
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 208: A Taste Bud Organoid-Based
           Microelectrode Array Biosensor for Taste Sensing

    • Authors: Shuge Liu, Ping Zhu, Yulan Tian, Yating Chen, Yage Liu, Miaomiao Wang, Wei Chen, Liping Du, Chunsheng Wu
      First page: 208
      Abstract: The biological taste system has the unique ability to detect taste substances. Biomaterials originating from a biological taste system have been recognized as ideal candidates to serve as sensitive elements in the development of taste-based biosensors. In this study, we developed a taste bud organoid-based biosensor for the research of taste sensation. Taste bud organoids prepared from newborn mice were cultured and loaded onto the surface of a 64-channel microelectrode array (MEA) chip to explore the electrophysiological changes upon taste; an MEA chip was used to simultaneously record multiple-neuron firing activities from taste bud organoids under different taste stimuli, which helped to reveal the role of taste buds in taste sensing. The obtained results show that taste cells separated from the taste epithelium grew well into spherical structures under 3D culture conditions. These structures were composed of multiple cells with obvious budding structures. Moreover, the multicellular spheres were seeded on a 64-channel microelectrode array and processed with different taste stimuli. It was indicated that the MEA chip could efficiently monitor the electrophysiological signals from taste bud organoids in response to various taste stimuli. This biosensor provides a new method for the study of taste sensations and taste bud functions.
      Citation: Chemosensors
      PubDate: 2022-06-02
      DOI: 10.3390/chemosensors10060208
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 209: A Highly Sensitive Electrochemical
           Sensor for Cd2+ Detection Based on Prussian Blue-PEDOT-Loaded
           Laser-Scribed Graphene-Modified Glassy Carbon Electrode

    • Authors: Londhe Akash Machhindra, Yi-Kuang Yen
      First page: 209
      Abstract: Heavy metal ion pollution has had a serious influence on human health and the environment. Therefore, the monitoring of heavy metal ions is of great practical significance. In this work, we describe the development of an electrochemical sensor to detect cadmium (Cd2+) using a Prussian blue (PB), poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT)-loaded laser-scribed graphene (LSG) nanocomposite-modified glassy carbon electrode (GCE). In this nanocomposite material, we successfully brought together the advantages of an extraordinarily large surface area. The accumulation of PB nanoparticles results in an efficient electrochemical sensor with high sensitivity and selectivity and fast detection ability, developed for the trace-level detection of Cd2+. Electrochemical features were explored via cyclic voltammetry (CV), whereas the stripping voltammetry behavior of modified electrodes was analyzed by utilizing differential pulse voltammetry. Compared with bare GCE, the LSG/PB-PEDOT/GCE modified electrode greatly increased the anodic stripping peak currents of Cd2+. Under the optimized conditions, the direct and facile detection of Cd2+ was achieved with a wide linear range (1 nM–10 µM) and a low LOD (0.85 nM).
      Citation: Chemosensors
      PubDate: 2022-06-02
      DOI: 10.3390/chemosensors10060209
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 210: Isothermal Amplification and Lateral
           Flow Nucleic Acid Test for the Detection of Shiga Toxin-Producing Bacteria
           for Food Monitoring

    • Authors: Sabrina Petrucci, Emre Dikici, Sylvia Daunert, Sapna K. Deo
      First page: 210
      Abstract: Foodborne bacteria have persisted as a significant threat to public health and to the food and agriculture industry. Due to the widespread impact of these pathogens, there has been a push for the development of strategies that can rapidly detect foodborne bacteria on-site. Shiga toxin-producing E. coli strains (such as E. coli O157:H7, E. coli O121, and E. coli O26) from contaminated food have been a major concern. They carry genes stx1 and/or stx2 that produce two toxins, Shiga toxin 1 and Shiga toxin 2, which are virulent proteins. In this work, we demonstrate the development of a rapid test based on an isothermal recombinase polymerase amplification reaction for two Shiga toxin genes in a single reaction. Results of the amplification reaction are visualized simultaneously for both Shiga toxins on a single lateral flow paper strip. This strategy targets the DNA encoding Shiga toxin 1 and 2, allowing for broad detection of any Shiga toxin-producing bacterial species. From sample to answer, this method can achieve results in approximately 35 min with a detection limit of 10 CFU/mL. This strategy is sensitive and selective, detecting only Shiga toxin-producing bacteria. There was no interference observed from non-pathogenic or pathogenic non-Shiga toxin-producing bacteria. A detection limit of 10 CFU/mL for Shiga toxin-producing E. coli was also obtained in a food matrix. This strategy is advantageous as it allows for timely identification of Shiga toxin-related contamination for quick initial food contamination assessments.
      Citation: Chemosensors
      PubDate: 2022-06-02
      DOI: 10.3390/chemosensors10060210
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 211: Preparation of Au@ZnO Nanofilms by
           Combining Magnetron Sputtering and Post-Annealing for Selective Detection
           of Isopropanol

    • Authors: Guodong Wang, Pengju Wu, Lanlan Guo, Wei Wang, Wenqiang Liu, Yuanyuan Wang, Tingyu Chen, Haohan Wang, Yonghao Xu, Yingli Yang
      First page: 211
      Abstract: We demonstrate the highly sensitive and fast response/recovery gas sensors for detecting isopropanol (IPA), in which the Au-nanoparticles-modified ZnO (Au@ZnO) nanofilms act as the active layers. The data confirm that both the response and the response/recovery speed for the detection of IPA are significantly improved by adding Au nanoparticles on the surface of ZnO nanofilms. The gas sensor with an Optimum Au@ZnO nanofilm exhibits the highest responses of 160 and 7 to the 100 and 1 ppm IPA at 300 °C, which indicates high sensitivity and a very low detecting limit. The sensor also exhibits a very short response/recovery time of 4/15 s on the optimized Au@ZnO nanofilm, which is much shorter than that of the sensor with a pure ZnO nanofilm. The mechanisms of the performance improvement in the sensors are discussed in detail. Both the electronic sensitization and the chemical sensitization of the ZnO nanofilms are improved by the modified Au nanoparticles, which not only regulate the thickness of the depletion layer but also increase the amount of adsorbed oxygen species on the surfaces. This work proposes a strategy to develop a highly sensitive gas sensor for real-time monitoring of IPA.
      Citation: Chemosensors
      PubDate: 2022-06-03
      DOI: 10.3390/chemosensors10060211
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 212: Gas-Sensing Properties of Dissolved
           Gases in Insulating Material Adsorbed on SnO2–GeSe Monolayer

    • Authors: Liang-Yan Guo, Suning Liang, Zhi Yang, Lingfeng Jin, Yaxiong Tan, Zhengyong Huang
      First page: 212
      Abstract: In a transformer, the insulation materials will produce different dissolved gases due to various faults in the operation of the transformer, in which C2H2, CH4, and H2 are the main dissolved gases. In this study, the adsorption characteristics of the above three gases on the SnO2–GeSe monolayer surface were discussed and analyzed based on the density functional theory. The adsorption energy, transfer charge, geometric structure parameters, electronic density of states, electronic local function, charge difference density, and recovery time were calculated and compared to characterize the gas-sensing adsorption mechanism. The results showed that the SnO2–GeSe monolayer exhibited good adsorption capacity, selectivity, and repeatability for the three characteristic dissolved gases. After adsorbing CH4 gas molecules, the conductivity of the SnO2–GeSe monolayer decreased. After adsorbing C2H2 and H2 gas molecules, the conductivity of the SnO2–GeSe monolayer increased. Therefore, the SnO2–GeSe monolayer has great application potential in the real-time monitoring of dissolved gases in insulating materials, which may become a new type of resistive gas sensor.
      Citation: Chemosensors
      PubDate: 2022-06-05
      DOI: 10.3390/chemosensors10060212
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 213: Nitrogen Dioxide Optical Sensor Based on
           Redox-Active Tetrazolium/Pluronic Nanoparticles Embedded in PDMS Membranes

    • Authors: Esteban Araya-Hermosilla, Rodrigo Araya-Hermosilla, Francesco Visentin, Francesco Picchioni, Andrea Pucci, Virgilio Mattoli
      First page: 213
      Abstract: Anthropogenic toxic vapour and gases are a worldwide threat for human health and to the environment. Therefore, it is crucial to develop highly sensitive devices that guarantee their rapid detection. Here, we prepared redox-switchable colloids by the in-situ reduction of 2,3,5-triphenyl-2H-tetrazolium (TTC) into triphenyl formazan (TF) stabilised with Pluronic F127 in aqueous media. The colloids were readily embedded in polydimethylsiloxane (PDMS) to produce a selective colour-switchable membrane for nitrogen dioxide (NO2) detection. We found that the TTC reduction resulted in the production of red-coloured colloids with zeta potential between −1 to 3 mV and hydrodynamic diameters between 114 to 305 nm as hydrophobic dispersion in aqueous media stabilised by Pluronic at different molar concentrations. Moreover, the embedded colloids rendered highly homogenous red colour gas-permeable PDMS elastomeric membrane. Once exposed to NO2, the membrane began to bleach after 30 s due to the oxidation of the embedded TF and undergo a complete decolouration after 180 s. Such features allowed the membrane integration in a low-cost sensing device that showed a high sensitivity and low detection limit to NO2.
      Citation: Chemosensors
      PubDate: 2022-06-06
      DOI: 10.3390/chemosensors10060213
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 214: Screen-printed Gold Electrode
           Functionalized with Deferoxamine for Iron(III) Detection

    • Authors: Giancarla Alberti, Camilla Zanoni, Sara Rovertoni, Lisa Rita Magnaghi, Raffaela Biesuz
      First page: 214
      Abstract: Deferoxamine (DFO), a hydroxamic siderophore with a high affinity for Fe(III), is immobilized as a functionalized self-assembled monolayer of a thiol (SAM) on the gold surface of a screen-printed cell to develop a voltammetric sensor for iron(III). The surface of the working electrode was characterized, before and after functionalization, by determining surface properties such as the area and the double-layer capacitance. The Fe(III) detection was performed by DPV analysis after preconcentration of the cation at the open circuit potential in solution at pH = 1 for two minutes. The method was applied to the iron(III) quantification in water samples giving promising results.
      Citation: Chemosensors
      PubDate: 2022-06-06
      DOI: 10.3390/chemosensors10060214
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 215: Detecting the Bitterness of
           Milk-Protein-Derived Peptides Using an Electronic Tongue

    • Authors: Arijit Nath, Burak Atilla Eren, John-Lewis Zinia Zaukuu, András Koris, Klára Pásztorné-Huszár, Emőke Szerdahelyi, Zoltan Kovacs
      First page: 215
      Abstract: Bitterness is a considerable limiting factor for the application of bioactive peptides in the food industry. The objective of this study was to compare the level of bitterness of milk-protein-derived peptides using an electronic tongue (E-tongue). Liquid milk protein concentrate (LMPC) was prepared from ultra-heat-treated skimmed cow’s milk. It was initially hydrolyzed with different concentrations of trypsin, namely, 0.008 g·L−1, 0.016 g·L−1 and 0.032 g·L−1. In a later exercise, tryptic-hydrolyzed LMPC (LMPC-T) was further hydrolyzed using Lactobacillus bulgaricus and Streptococcus thermophilus. The effect of glucose in microbial hydrolysis was studied. The bitterness of peptides was evaluated with respect to quinine, a standard bittering agent. The level of bitterness of the peptides after microbial hydrolysis of LMPC-T (LMPC-T-F and LMPC-T-FG) was evaluated using a potentiometric E-tongue equipped with a sensor array that had seven chemically modified field-effect transistor sensors. The results of the measurements were evaluated using principal component analysis (PCA), and subsequently, a classification of the models was built using the linear discriminant analysis (LDA) method. The bitterness of peptides in LMPC-T-F and LMPC-T-FG was increased with the increase in the concentration of trypsin. The bitterness of peptides was reduced in LMPC-T-FG compared with LMPC-T-F. The potential application of the E-tongue using a standard model solution with quinine was shown to follow the bitterness of peptides.
      Citation: Chemosensors
      PubDate: 2022-06-07
      DOI: 10.3390/chemosensors10060215
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 216: Deep Eutectic Solvents Enhance Stability
           of Ag/AgCl Solid State Miniaturised Reference Electrode

    • Authors: Sahar S. M. Alabdullah, Amina M. Abass, Huda Ghalib Salman
      First page: 216
      Abstract: A new class of solid-state miniaturised reference electrodes with a deep eutectic solvent as an alternate enhancement electrode system is described. A simple and accurate stable electrochemical sensor was prepared by developing a conventional reference electrode using an Ag/AgCl planar micro-reference electrode covered with a PVC polymer. A conductive deep eutectic solvent (DES), ethaline, was added in small quantities and mixed with an internal electrolyte to maintain the Cl− ion concentration in the constructed electrode. The fabricated microelectrode showed good stability, reproducibility, and long-term stability against varying concentrations of different ions. The potential response of the fabricated microelectrode was studied under varying concentrations of Cl− ions in the presence of 0.1 to 1.0% DES in a concentrated electrolyte system (20 mM Na2SO4). The stability of the fabricated microelectrode was addressed against Br− and Cl− ions using different inorganic salts, and the potential measurements were found to be insensitive toward all responsive ions. The stability response of the fabricated microelectrode against Cl− ions was optimised in the presence of 1.0% DES. The experimental data showed good agreement with the potential change of the fabricated electrode in the presence of the supporting DES electrolyte. The liquid junction-free PVC solid-state miniaturised reference electrode demonstrated a constant potentiometric measurement over a long period of time. The concentrated supporting DES electrolyte solution (20 mM) exhibited better stability values and was a more suitable fabricated microelectrode than other additive concentrations. The long-term stability of the developed microelectrode displayed a good lifetime and high stability of around 60 days.
      Citation: Chemosensors
      PubDate: 2022-06-07
      DOI: 10.3390/chemosensors10060216
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 217: A Plankton Detection Method Based on
           Neural Networks and Digital Holographic Imaging

    • Authors: Kaiqi Lang, Hui Cai, Xiaoping Wang
      First page: 217
      Abstract: Detecting marine plankton by means of digital holographic microscopy (DHM) has been successfully deployed in recent decades; however, in most previous studies, the identification of the position, shape, and size of plankton has been neglected, which may negate some of the advantages of DHM. Therefore, the procedure of image fusion has been added between the reconstruction of initial holograms and the final identification, which could help present all the images of plankton clearly in a volume of seawater. A new image fusion method called digital holographic microscopy-fully convolutional networks (DHM-FCN) is proposed, which is based on the improved fully convolutional networks (FCN). The DHM-FCN model runs 20 times faster than traditional image fusion methods and suppresses the noise in the holograms. All plankton in a 2 mm thick water body could be clearly represented in the fusion image. The edges of the plankton in the DHM-FCN fusion image are continuous and clear without speckle noise inside. The neural network model, YOLOv4, for plankton identification and localization, was established. A mean average precision (mAP) of 97.69% was obtained for five species, Alexandrium tamarense, Chattonella marina, Mesodinium rubrum, Scrippsiella trochoidea, and Prorocentrum lima. The results of this study could provide a fast image fusion method and a visual method to detect organisms in water.
      Citation: Chemosensors
      PubDate: 2022-06-08
      DOI: 10.3390/chemosensors10060217
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 218: Detection of Acetoin and Diacetyl by a
           Tobacco Mosaic Virus-Assisted Field-Effect Biosensor

    • Authors: Melanie Welden, Robin Severins, Arshak Poghossian, Christina Wege, Johannes Bongaerts, Petra Siegert, Michael Keusgen, Michael J. Schöning
      First page: 218
      Abstract: Acetoin and diacetyl have a major impact on the flavor of alcoholic beverages such as wine or beer. Therefore, their measurement is important during the fermentation process. Until now, gas chromatographic techniques have typically been applied; however, these require expensive laboratory equipment and trained staff, and do not allow for online monitoring. In this work, a capacitive electrolyte–insulator–semiconductor sensor modified with tobacco mosaic virus (TMV) particles as enzyme nanocarriers for the detection of acetoin and diacetyl is presented. The enzyme acetoin reductase from Alkalihalobacillus clausii DSM 8716T is immobilized via biotin–streptavidin affinity, binding to the surface of the TMV particles. The TMV-assisted biosensor is electrochemically characterized by means of leakage–current, capacitance–voltage, and constant capacitance measurements. In this paper, the novel biosensor is studied regarding its sensitivity and long-term stability in buffer solution. Moreover, the TMV-assisted capacitive field-effect sensor is applied for the detection of diacetyl for the first time. The measurement of acetoin and diacetyl with the same sensor setup is demonstrated. Finally, the successive detection of acetoin and diacetyl in buffer and in diluted beer is studied by tuning the sensitivity of the biosensor using the pH value of the measurement solution.
      Citation: Chemosensors
      PubDate: 2022-06-08
      DOI: 10.3390/chemosensors10060218
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 219: Folic Acid-Modified Cerium-Doped Carbon
           Dots as Photoluminescence Sensors for Cancer Cells Identification and
           Fe(III) Detection

    • Authors: Jincheng Li, Zengchao Guo, Tengfei Liu, Fangfang Yu, Jiayu Zeng, Ying Zhang, Lihong Yin, Xiaohui Liu, Hui Jiang, Xuemei Wang
      First page: 219
      Abstract: Carbon dots (CDs) are a new class of carbon-based luminescence materials with fascinating properties. They have been given great expectations on superseding traditional semiconductor quantum dots due to their good dispersity and stability, relatively low toxicity, superior resistance to photobleaching, and excellent biocompatibility. The diversified luminescence properties of CDs are largely due to the synthetic strategies and precursors. In view of those described above, this study has explored the possibility to establish a facile one-step hydrothermal method for the one-pot synthesis of folic acid-modified cerium-doped CDs (Ce-CDs-FA), which could be further utilized as a sensitive fluorescent nanoprobe for biosensing. This investigation demonstrates that the Ce-CDs-FA nanocomposites have nice biocompatibility and bright fluorescent properties, which can be readily utilized to detect cancer cells through recognizing overexpressing folate receptors by virtue of folic acid. Meanwhile, it is noted that the Fe3+ ion can actualize a specific and hypersensitive quenching effect for these Ce-CDs-FA nanocomposites, which can be further explored for special ion recognition, including iron ions. It raises the possibility that the as-prepared Ce-CDs-FA nanocomposites could be extended as a dual fluorescence sensor for targeted cell imaging and Fe3+ ion detection.
      Citation: Chemosensors
      PubDate: 2022-06-09
      DOI: 10.3390/chemosensors10060219
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 220: Classification of Aviation Alloys Using
           Laser-Induced Breakdown Spectroscopy Based on a WT-PSO-LSSVM Model

    • Authors: Haorong Guo, Minchao Cui, Zhongqi Feng, Dacheng Zhang, Dinghua Zhang
      First page: 220
      Abstract: It is well-known that aviation alloys of different grades show large differences in mechanical properties. At present, alloys must be strictly distinguished in the manufacturing plant because their close appearance and density are easily confused In this work, the wavelet transform (WT) method combined with the least squares support vector machine (LSSVM) is applied to the classification and identification of aviation alloys by laser-induced breakdown spectroscopy (LIBS). This experiment employed six different grades of aviation alloy as the classification samples and obtained 100 sets of spectral data for each sample. This research included the steps of preprocessing the obtained spectral data, model training, and parameter optimization. Finally, the accuracy of the training set was 99.98%, and the accuracy of the test set was 99.56%. Therefore, it is concluded that the model has superior generalization capacity and portability. The result of this work illustrates that LIBS technology can be adopted for the rapid identification of aviation alloys, which is of great significance for on-site quality control and efficiency improvement of aerospace parts manufacturing.
      Citation: Chemosensors
      PubDate: 2022-06-10
      DOI: 10.3390/chemosensors10060220
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 221: SARS-CoV-2 Detection Methods

    • Authors: Alexandra Lino, Marita A. Cardoso, Helena M. R. Gonçalves, Paula Martins-Lopes
      First page: 221
      Abstract: A fast and highly specific detection of COVID-19 infections is essential in managing the virus dissemination networks. The most relevant technologies developed for SARS-CoV-2 detection, along with their advantages and limitations, will be presented and fully explored. Additionally, some of the newest and emerging COVID-19 diagnosis tools, such as biosensing platforms, will also be introduced. Considering the extreme relevance that all these technologies assume in pandemic control, it is of the utmost relevance to have an intrinsic knowledge of the parameters that need to be taken into consideration before choosing the most adequate test for a particular situation. Moreover, the new variants of the virus and their potential impact on the detection method’s effectiveness will be discussed. In order to better manage the pandemic, it is essential to maintain continuous research into the SARS-CoV-2 genome and updated genomic surveillance at the global level. This will allow for timely detection of new mutations and viral variants, which may affect the performance of COVID-19 detection tests.
      Citation: Chemosensors
      PubDate: 2022-06-11
      DOI: 10.3390/chemosensors10060221
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 222: Differential Sensing of Antibiotics
           Using Metal Ions and Gold Nanoclusters Based on TMB–H2O2 System

    • Authors: Suqin Liu, Jinjie Wang, Yue Hu, Yunjing Shi, Jingxia Yang, Min Zhang
      First page: 222
      Abstract: In the water system, antibiotic pollution significantly impacts the human body and the environment. Therefore, it is essential to quickly identify the types of antibiotics in the system and detect their concentration. It has been reported that many metal ions interact with antibiotics, and some of them can also change the enzyme-like catalytic properties of gold clusters (AuNCs). In the experiments, we found significant differences in the experimental results when different antibiotics and metal ions were placed in a TMB-H2O2 system with AuNCs as catalysts. Based on this result, we devised a simple and sensitive colorimetric method for the simultaneous detection of multiple antibiotics using AuNCs-metal ions as the sensor, a multifunctional microplate detector as the detection instrument, and LDA as the analytical method. This method was successfully applied for the identification of antibiotics and the detection of their concentrations in river water.
      Citation: Chemosensors
      PubDate: 2022-06-12
      DOI: 10.3390/chemosensors10060222
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 223: Recent Trends in Carbon Nanotube
           Electrodes for Flexible Supercapacitors: A Review of Smart Energy Storage
           Device Assembly and Performance

    • Authors: Himadri Tanaya Das, Swapnamoy Dutta, Tamilarasan Elango Balaji, Nigamananda Das, Payaswini Das, Neelu Dheer, Rajni Kanojia, Preety Ahuja, Sanjeev Kumar Ujjain
      First page: 223
      Abstract: In order to upgrade existing electronic technology, we need simultaneously to advance power supply devices to match emerging requirements. Owing to the rapidly growing wearable and portable electronics markets, the demand to develop flexible energy storage devices is among the top priorities for humankind. Flexible supercapacitors (FSCs) have attracted tremendous attention, owing to their unrivaled electrochemical performances, long cyclability and mechanical flexibility. Carbon nanotubes (CNTs), long recognized for their mechanical toughness, with an elastic strain limit of up to 20%, are regarded as potential candidates for FSC electrodes. Along with excellent mechanical properties, high electrical conductivity, and large surface area, their assemblage adaptability from one-dimensional fibers to two-dimensional films to three-dimensional sponges makes CNTs attractive. In this review, we have summarized various assemblies of CNT structures, and their involvement in various device configurations of FSCs. Furthermore, to present a clear scenario of recent developments, we discuss the electrochemical performance of fabricated flexible devices of different CNT structures and their composites, including additional properties such as compressibility and stretchability. Additionally, the drawbacks and benefits of the study and further potential scopes are distinctly emphasized for future researchers.
      Citation: Chemosensors
      PubDate: 2022-06-13
      DOI: 10.3390/chemosensors10060223
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 224: Noise Spectrum as a Source of
           Information in Gas Sensors Based on Liquid-Phase Exfoliated Graphene

    • Authors: Stevan Andrić, Ivana Jokić, Jelena Stevanović, Marko Spasenović, Miloš Frantlović
      First page: 224
      Abstract: Surfaces of adsorption-based gas sensors are often heterogeneous, with adsorption sites that differ in their affinities for gas particle binding. Knowing adsorption/desorption energies, surface densities and the relative abundance of sites of different types is important, because these parameters impact sensor sensitivity and selectivity, and are relevant for revealing the response-generating mechanisms. We show that the analysis of the noise of adsorption-based sensors can be used to study gas adsorption on heterogeneous sensing surfaces, which is applicable to industrially important liquid-phase exfoliated (LPE) graphene. Our results for CO2 adsorption on an LPE graphene surface, with different types of adsorption sites on graphene flake edges and basal planes, show that the noise spectrum data can be used to characterize such surfaces in terms of parameters that determine the sensing properties of the adsorbing material. Notably, the spectrum characteristic frequencies are an unambiguous indicator of the relative abundance of different types of adsorption sites on the sensing surface and their surface densities. We also demonstrate that spectrum features indicate the fraction of the binding sites that are already occupied by another gas species. The presented study can be applied to the design and production of graphene and other sensing surfaces with an optimal sensing performance.
      Citation: Chemosensors
      PubDate: 2022-06-14
      DOI: 10.3390/chemosensors10060224
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 225: Fabrication and Magneto-Structural
           Properties of Co2-Based Heusler Alloy Glass-Coated Microwires with High
           Curie Temperature

    • Authors: Mohamed Salaheldeen, Alfonso Garcia-Gomez, Mihail Ipatov, Paula Corte-Leon, Valentina Zhukova, Juan Maria Blanco, Arcady Zhukov
      First page: 225
      Abstract: In this work, we were able to produce Co2FeSi Heusler alloy glass-covered microwires with a metallic nucleus diameter of about 4.4 µm and total sample diameter of about 17.6 μm by the Taylor–Ulitovsky Technique. This low cost and single step fabrication process allowed the preparation of up to kilometers long glass-coated microwires starting from a few grams of high purity inexpensive elements (Co, Fe and Si), for a wide range of applications. From the X-ray diffraction, XRD, analysis of the metallic nucleus, it was shown that the structure consists of a mixture of crystalline and amorphous phases. The single and wide crystalline peak was attributed to a L21 crystalline structure (5.640 Å), with a possible B2 disorder. In addition, nanocrystalline structure with an average grain size, Dg = 17.8 nm, and crystalline phase content of about 52% was obtained. The magnetic measurements indicated a well-defined magnetic anisotropy for all ranges of temperature. Moreover, soft magnetic behavior was observed for the temperature measuring range of 5–1000 K. Strong dependence of the magnetic properties on the applied magnetic field and temperature was observed. Zero field cooling and field cooling magnetization curves showed large irreversibility magnetic behavior with a blocking temperature (TB = 205 K). The in-plane magnetization remanence and coercivity showed quite different behavior with temperature, due to the existence of different magnetic phases induced from the internal stress created by the glass-coated layer. Moreover, a high Curie temperature was reported (Tc ≈ 1059 K), which predisposes this material to being a suitable candidate for high temperature spintronic applications.
      Citation: Chemosensors
      PubDate: 2022-06-14
      DOI: 10.3390/chemosensors10060225
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 226: Dynamic Measurement of VOCs with
           Multiple Characteristic Peaks Based on Temperature Modulation of ZnO Gas

    • Authors: Xue Shi, Hua Zhang, Hanyang Ji, Fanli Meng
      First page: 226
      Abstract: Volatile organic compounds (VOC) harm human health seriously in the air. Therefore, it is essential to recognize VOC gases qualitatively and quantitatively. The dynamic measurement method can improve the selectivity of metal oxide semiconductor (MOS) gas sensors to VOC, but there is a problem of the insufficient number of characteristic peaks. From the experimental point of view, the primary judgment basis for the correct qualitative and quantitative recognition of VOC gases by the dynamic measurement method is the characteristic peak of the dynamic response signal. However, the traditional dynamic measurement method generally only has two characteristic peaks. In this experiment, the voltage was changed at the time of the second characteristic peak by controlling the constant dynamic response period. Taking ethyl alcohol as an example, the experimental results show that the characteristic peak of the dynamic response signal does not increase when the voltage is constant. However, a new characteristic peak will appear based on a continuously rising heating voltage. The characteristic peaks of the dynamic response of n-propyl alcohol, isopropyl alcohol, and n-butyl alcohol were also increased based on the rising heating voltage waveform. Based on the K-Nearest-Neighbors algorithm, the qualitative and quantitative recognition rate of the four alcohol homologue gases reached 100%.
      Citation: Chemosensors
      PubDate: 2022-06-15
      DOI: 10.3390/chemosensors10060226
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 227: High-Performance Room-Temperature
           Conductometric Gas Sensors: Materials and Strategies

    • Authors: Antonio Vázquez-López, Javier Bartolomé, Ana Cremades, David Maestre
      First page: 227
      Abstract: Chemiresistive sensors have gained increasing interest in recent years due to the necessity of low-cost, effective, high-performance gas sensors to detect volatile organic compounds (VOC) and other harmful pollutants. While most of the gas sensing technologies rely on the use of high operation temperatures, which increase usage cost and decrease efficiency due to high power consumption, a particular subset of gas sensors can operate at room temperature (RT). Current approaches are aimed at the development of high-sensitivity and multiple-selectivity room-temperature sensors, where substantial research efforts have been conducted. However, fewer studies presents the specific mechanism of action on why those particular materials can work at room temperature and how to both enhance and optimize their RT performance. Herein, we present strategies to achieve RT gas sensing for various materials, such as metals and metal oxides (MOs), as well as some of the most promising candidates, such as polymers and hybrid composites. Finally, the future promising outlook on this technology is discussed.
      Citation: Chemosensors
      PubDate: 2022-06-15
      DOI: 10.3390/chemosensors10060227
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 228: Temperature Sensors Based on Polymer
           Fiber Optic Interferometer

    • Authors: Malgorzata Szczerska
      First page: 228
      Abstract: Temperature measurements are of great importance in many fields of human activities, including industry, technology, and science. For example, obtaining a certain temperature value or a sudden change in it can be the primary control marker of a chemical process. Fiber optic sensors have remarkable properties giving a broad range of applications. They enable continuous real-time temperature control in difficult-to-reach areas, in hazardous working environments (air pollution, chemical or ionizing contamination), and in the presence of electromagnetic disturbances. The use of fiber optic temperature sensors in polymer technology can significantly reduce the cost of their production. Moreover, the installation process and usage would be simplified. As a result, these types of sensors would become increasingly popular in industrial solutions. This review provides a critical overview of the latest development of fiber optic temperature sensors based on Fabry–Pérot interferometer made with polymer technology.
      Citation: Chemosensors
      PubDate: 2022-06-15
      DOI: 10.3390/chemosensors10060228
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 229: Extraction of Reduced Infrared Biomarker
           Signatures for the Stratification of Patients Affected by
           Parkinson’s Disease: An Untargeted Metabolomic Approach

    • Authors: Kateryna Tkachenko, María Espinosa, Isabel Esteban-Díez, José M. González-Sáiz, Consuelo Pizarro
      First page: 229
      Abstract: An untargeted Fourier transform infrared (FTIR) metabolomic approach was employed to study metabolic changes and disarrangements, recorded as infrared signatures, in Parkinson’s disease (PD). Herein, the principal aim was to propose an efficient sequential classification strategy based on SELECT-LDA, which enabled optimal stratification of three main categories: PD patients from subjects with Alzheimer’s disease (AD) and healthy controls (HC). Moreover, sub-categories, such as PD at the early stage (PDI) from PD in the advanced stage (PDD), and PDD vs. AD, were stratified. Every classification step with selected wavenumbers achieved 90.11% to 100% correct assignment rates in classification and internal validation. Therefore, selected metabolic signatures from new patients could be used as input features for screening and diagnostic purposes.
      Citation: Chemosensors
      PubDate: 2022-06-16
      DOI: 10.3390/chemosensors10060229
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 230: Promising Novel Barium Carbonate
           One-Dimensional Nanostructures and Their Gas Sensing Application:
           Preparation and Characterization

    • Authors: Nagih M. Shaalan
      First page: 230
      Abstract: Recently, barium carbonate-based nanomaterials have been used for sensor and catalysis applications. The sensing performance can be improved with a suitable one-dimensional nanostructure. In this regard, novel nanosized BaCO3 materials were fabricated by a one-pot designed thermal evaporation system. Ten milligrams of Ba as raw material were used to deposit BaCO3 nanostructures at a pressure of 0.85 torr and a temperature of 850 °C in a partial oxygen atmosphere of the ambient. This simple method for fabricating novel BaCO3 nanostructures is presented here. X-ray diffraction was indexed on the orthorhombic polycrystalline structure of the prepared BaCO3. The nanostructures deposited here could be described as Datura-like structures linked with nanowires of 20–50 nm in diameter and 5 µm in length. The BaCO3 nanostructure prepared by the current method exhibited a semiconductor-like behavior with an activation energy of 0.68 eV. This behavior was ascribed to the nature of the morphology, which may possess large defective points. Thus, this nanostructure was subjected to gas sensing measurements, showing high activity toward NO2 gas. The proposed sensor also underwent deep investigation toward NO2 at various gas concentrations and working. The response and recovery time constants were recorded in the ranges of 6–20 s and 30–150 s, respectively. The sensor showed its reversibility toward NO2 when the sensor signal was repeated at various cycles of various concentrations. The sensor was exposed to different levels of humidity, showing high performance toward NO2 gas at 250 °C. The sensor exhibited fast response and recovery toward NO2 gas.
      Citation: Chemosensors
      PubDate: 2022-06-17
      DOI: 10.3390/chemosensors10060230
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 231: Metal Oxide Semiconductor Sensors for
           Triethylamine Detection: Sensing Performance and Improvements

    • Authors: Hua Zhang, Yinghao Guo, Fanli Meng
      First page: 231
      Abstract: Triethylamine (TEA) is an organic compound that is commonly used in industries, but its volatile, inflammable, corrosive, and toxic nature leads to explosions and tissue damage. A sensitive, accurate, and in situ monitoring of TEA is of great significance to production safety and human health. Metal oxide semiconductors (MOSs) are widely used as gas sensors for volatile organic compounds due to their high bandgap and unique microstructure. This review aims to provide insights into the further development of MOSs by generalizing existing MOSs for TEA detection and measures to improve their sensing performance. This review starts by proposing the basic gas-sensing characteristics of the sensor and two typical TEA sensing mechanisms. Then, recent developments to improve the sensing performance of TEA sensors are summarized from different aspects, such as the optimization of material morphology, the incorporation of other materials (metal elements, conducting polymers, etc.), the development of new materials (graphene, TMDs, etc.), the application of advanced fabrication devices, and the introduction of external stimulation. Finally, this review concludes with prospects for using the aforementioned methods in the fabrication of high-performance TEA gas sensors, as well as highlighting the significance and research challenges in this emerging field.
      Citation: Chemosensors
      PubDate: 2022-06-17
      DOI: 10.3390/chemosensors10060231
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 232: Optical Chemical Sensor Based on
           Fast-Protein Liquid Chromatography for Regular Peritoneal Protein Loss
           Assessment in End-Stage Renal Disease Patients on Continuous Ambulatory
           Peritoneal Dialysis

    • Authors: Artur Kuznetsov, Aleksandr Frorip, Alar Sünter, Vadim Korsakov, Georgii Konoplev, Oksana Stepanova, Natalia Roschina, Nikolay Ovsyannikov, Daniil Lialin, Roman Gerasimchuk, Alexander Dmitriev, Nikolay Mukhin, Soeren Hirsch
      First page: 232
      Abstract: Point-of-care testing (POCT) devices are becoming increasingly popular in the medical community as an alternative to conventional laboratory testing, especially for home treatments or other forms of outpatient care. Multiple-use chemical sensors with minimal requirements for disposables are among the most practical and cost-effective POC diagnostic instruments, especially in managing chronic conditions. An affordable, simple, and easy-to-use optical sensor based on fast protein liquid chromatography with direct UV absorption detection was developed for the rapid determination of the total protein concentration in effluent peritoneal dialysate and for the assessment of protein losses in end-stage renal disease (ESRD) patients on constant ambulatory peritoneal dialysis (CAPD). The sensor employs non-disposable PD-10 desalting columns for the separation of molecules with different molecular weights and a deep UV LED (maximum at 285 nm) as a light source for optical detection. The analytic procedure is relatively simple, takes 10–15 min, and potentially can be performed by patients themselves or nursing staff without laboratory training. Preliminary clinical trials on a group of 23 patients on CAPD revealed a good concordance between the protein concentrations in dialysate samples measured with the sensor and an automated biochemical analyzer; the mean relative error was about 10%, which is comparable with routine clinical laboratory methods.
      Citation: Chemosensors
      PubDate: 2022-06-17
      DOI: 10.3390/chemosensors10060232
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 233: Recent Advances of Fluorescence Probes
           for Imaging of Ferroptosis Process

    • Authors: Hongyu Li, Yan An, Jie Gao, Mingyan Yang, Junjun Luo, Xinmin Li, Jiajia Lv, Xiaohua Li, Zeli Yuan, Huimin Ma
      First page: 233
      Abstract: Ferroptosis is an iron−dependent form of regulated cell death. It has attracted more and more research interests since it was found because of its potential physiological and pathological roles. In recent years, many efforts have been made for the developments and applications of selective fluorescence probes for real−time and in situ tracking of bioactive species during ferroptosis process, which is necessary and significant to further study the modulation mechanisms and pathological functions of ferroptosis. In this review, we will focus on summarizing the newly developed fluorescence probes that have been applied for ferroptosis imaging in the recent years, and comprehensively discussing their design strategies, including the probes for iron, reactive oxygen species, biothiols and intracellular microenvironmental factors.
      Citation: Chemosensors
      PubDate: 2022-06-20
      DOI: 10.3390/chemosensors10060233
      Issue No: Vol. 10, No. 6 (2022)
  • Chemosensors, Vol. 10, Pages 150: Plasmonic Nanosensors: Design,
           Fabrication, and Applications in Biomedicine

    • Authors: Valeria Nocerino, Bruno Miranda, Chiara Tramontano, Giovanna Chianese, Principia Dardano, Ilaria Rea, Luca De Stefano
      First page: 150
      Abstract: Current advances in the fabrication of smart nanomaterials and nanostructured surfaces find wide usage in the biomedical field. In this context, nanosensors based on localized surface plasmon resonance exhibit unprecedented optical features that can be exploited to reduce the costs, analytic times, and need for expensive lab equipment. Moreover, they are promising for the design of nanoplatforms with multiple functionalities (e.g., multiplexed detection) with large integration within microelectronics and microfluidics. In this review, we summarize the most recent design strategies, fabrication approaches, and bio-applications of plasmonic nanoparticles (NPs) arranged in colloids, nanoarrays, and nanocomposites. After a brief introduction on the physical principles behind plasmonic nanostructures both as inherent optical detection and as nanoantennas for external signal amplification, we classify the proposed examples in colloid-based devices when plasmonic NPs operate in solution, nanoarrays when they are assembled or fabricated on rigid substrates, and nanocomposites when they are assembled within flexible/polymeric substrates. We highlight the main biomedical applications of the proposed devices and offer a general overview of the main strengths and limitations of the currently available plasmonic nanodevices.
      Citation: Chemosensors
      PubDate: 2022-04-20
      DOI: 10.3390/chemosensors10050150
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 151: Chalcone-Based Colorimetric Chemosensor
           for Detecting Ni2+

    • Authors: Sungjin Moon, Cheal Kim
      First page: 151
      Abstract: The first chalcone-based colorimetric chemosensor DPP (sodium (E)-2,4-dichloro-6-(3-oxo-3-(pyridine-2-yl)prop-1-en-1-yl)phenolate) was synthesized for detecting Ni2+ in near-perfect water. The synthesis of DPP was validated by using 1H, 13C NMR and ESI-MS. DPP selectively sensed Ni2+ through the color variation from yellow to purple. Detection limit of DPP for Ni2+ was calculated to be 0.36 μM (3σ/slope), which is below the standard (1.2 μM) set by the United States Environmental Protection Agency (EPA).The binding ratio of DPP to Ni2+ was determined as a 1:1 by using a Job plot and ESI-mass. The association constant of DPP and Ni2+ was calculated as 1.06 × 104 M−1 by the non-linear fitting analysis. In real samples, the sensing application of DPP for Ni2+ was successfully performed. DPP-coated paper-supported strips could also be used for detecting Ni2+. The binding mechanism of DPP to Ni2+ was proposed by ESI-MS, Job plot, UV-vis, FT-IR spectroscopy, and DFT calculations.
      Citation: Chemosensors
      PubDate: 2022-04-20
      DOI: 10.3390/chemosensors10050151
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 152: Neural Network Robustness Analysis Using
           Sensor Simulations for a Graphene-Based Semiconductor Gas Sensor

    • Authors: Sebastian A. Schober, Yosra Bahri, Cecilia Carbonelli, Robert Wille
      First page: 152
      Abstract: Despite their advantages regarding production costs and flexibility, chemiresistive gas sensors often show drawbacks in reproducibility, signal drift and ageing. As pattern recognition algorithms, such as neural networks, are operating on top of raw sensor signals, assessing the impact of these technological drawbacks on the prediction performance is essential for ensuring a suitable measuring accuracy. In this work, we propose a characterization scheme to analyze the robustness of different machine learning models for a chemiresistive gas sensor based on a sensor simulation model. Our investigations are structured into four separate studies: in three studies, the impact of different sensor instabilities on the concentration prediction performance of the algorithms is investigated, including sensor-to-sensor variations, sensor drift and sensor ageing. In a further study, the explainability of the machine learning models is analyzed by applying a state-of-the-art feature ranking method called SHAP. Our results show the feasibility of model-based algorithm testing and substantiate the need for the thorough characterization of chemiresistive sensor algorithms before sensor deployment in order to ensure robust measurement performance.
      Citation: Chemosensors
      PubDate: 2022-04-21
      DOI: 10.3390/chemosensors10050152
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 153: Nanoparticle-Mediated Signaling for
           Aptamer-Based Multiplexed Detection of Cortisol and Neuropeptide Y in

    • Authors: Naimesh Sardesai, Yi Liu, Regina Shia, Peter Mirau, Jorge L. Chávez, Nathan S. Swami
      First page: 153
      Abstract: Multiplexed profiling of the expression of neurochemical biomarkers of stress, for periodic assessment to enable augmentation of human performance, requires wash-free detection platforms that exhibit reproducible signals from samples in biological matrices. However, alterations in aptamer conformation after binding to targets, such as cortisol, are minimal based on NMR spectra, and the methylene blue signaling is blocked by serum proteins. Hence, in this study, we explore aptamer derivatization with magnetic nanoparticles that are conjugated with multiple methylene blue moieties, to amplify signals and alter the net charge configuration for repulsing serum proteins, so that the aptamer conformation upon target recognition can lead to a signal ON assay in serum media. Based on this, a microchip platform with addressable electrodes that are immobilized with selective aptamer receptors is developed for multiplexed detection of cortisol (1–700 ng/mL) and neuropeptide Y (5–1000 pg/mL) in patient-derived serum samples, which is validated by immunoassays. We envision the application of this sensor for profiling a wider array of human performance biomarkers under stress-related events to develop stress augmentation methodologies.
      Citation: Chemosensors
      PubDate: 2022-04-21
      DOI: 10.3390/chemosensors10050153
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 154: A Simple Ratiometric Electrochemical
           Aptasensor Based on the Thionine–Graphene Nanocomposite for
           Ultrasensitive Detection of Aflatoxin B2 in Peanut and Peanut Oil

    • Authors: Fan Jia, Yuye Li, Qingfa Gong, Dong Liu, Shuyun Meng, Chengxi Zhu, Tianyan You
      First page: 154
      Abstract: The accurate and reliable analysis of aflatoxin B2 (AFB2) is widely required in food and agricultural industries. In the present work, we report the first use of a ratiometric electrochemical aptasensor for AFB2 detection with high selectivity and reliability. The working principle relies on the conformation change of the aptamer induced by its specific recognition of AFB2 to vary the ratiometric signal. Based on this principle, the proposed aptasensor collects currents generated by thionine–graphene composites (ITHI) and ferrocene-labeled aptamers (IFc) to output the ratiometric signal of ITHI/IFc. In analysis, the value of ITHI remained stable while that of IFc increased with higher AFB2 concentration, thus offering a “signal-off” aptasensor by using ITHI/IFc as a yardstick. The fabricated aptasensor showed a linear range of 0.001–10 ng mL−1 with a detection limit of 0.19 pg mL−1 for AFB2 detection. Furthermore, its applicability was validated by using it to detect AFB2 in peanut and peanut oil samples with high rates of recovery. The developed ratiometric aptasensor shows the merits of simple fabrication and high accuracy, and it can be extended to detect other mycotoxins in agricultural products.
      Citation: Chemosensors
      PubDate: 2022-04-21
      DOI: 10.3390/chemosensors10050154
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 155: Wax-Printed Fluidic Controls for
           Delaying and Accelerating Fluid Transport on Paper-Based Analytical

    • Authors: Maria Tarara, Dimosthenis L. Giokas, George Z. Tsogas
      First page: 155
      Abstract: In this work, we explore a new method for controlling fluid transport rate on paper-based analytical devices that enables both the delay and the acceleration of fluid flow. The delays were incorporated by wax printing linear patterns of variable width within the flow channel and melted to penetrate the paper. In this manner, the surface tension of the fluid decreases while its contact angle increases, causing a pressure drop along the fluid path that reduces capillary flow. The acceleration of flow was accomplished by overlaying hydrophobic stripes (prepared by wax printing and melting the wax) on the hydrophilic path (top or top–bottom). In this manner, the fluid was repelled from two dimensions (vertical and applicate), increasing the flow rate. The combination of these methods on the same devices could adjust wicking time in intermediate time internals. The method enabled a wide timing of fluid transport, accomplishing a change in wicking times that extended from −41% to +259% compared to open paper channels. As a proof of concept, an enzymatic assay of glucose was used to demonstrate the utility of these fluid control methods in kinetic methods of analysis.
      Citation: Chemosensors
      PubDate: 2022-04-24
      DOI: 10.3390/chemosensors10050155
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 156: The Light-Addressable Potentiometric
           Sensor and Its Application in Biomedicine towards Chemical and Biological

    • Authors: Yage Liu, Ping Zhu, Shuge Liu, Yating Chen, Dongxin Liang, Miaomiao Wang, Liping Du, Chunsheng Wu
      First page: 156
      Abstract: The light-addressable potential sensor (LAPS) was invented in 1988 and has developed into a multi-functional platform for chemical and biological sensing in recent decades. Its surface can be flexibly divided into multiple regions or pixels through light addressability, and each of them can be sensed independently. By changing sensing materials and optical systems, the LAPS can measure different ions or molecules, and has been applied to the sensing of various chemical and biological molecules and cells. In this review, we firstly describe the basic principle of LAPS and the general configuration of a LAPS measurement system. Then, we outline the most recent applications of LAPS in chemical sensing, biosensing and cell monitoring. Finally, we enumerate and analyze the development trends of LAPS from the aspects of material and optical improvement, hoping to provide a research and application perspective for chemical sensing, biosensing and imaging technology.
      Citation: Chemosensors
      PubDate: 2022-04-24
      DOI: 10.3390/chemosensors10050156
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 157: Coupled Multiphysics Modelling of
           Sensors for Chemical, Biomedical, and Environmental Applications with
           Focus on Smart Materials and Low-Dimensional Nanostructures

    • Authors: Sundeep Singh, Roderick Melnik
      First page: 157
      Abstract: Low-dimensional nanostructures have many advantages when used in sensors compared to the traditional bulk materials, in particular in their sensitivity and specificity. In such nanostructures, the motion of carriers can be confined from one, two, or all three spatial dimensions, leading to their unique properties. New advancements in nanosensors, based on low-dimensional nanostructures, permit their functioning at scales comparable with biological processes and natural systems, allowing their efficient functionalization with chemical and biological molecules. In this article, we provide details of such sensors, focusing on their several important classes, as well as the issues of their designs based on mathematical and computational models covering a range of scales. Such multiscale models require state-of-the-art techniques for their solutions, and we provide an overview of the associated numerical methodologies and approaches in this context. We emphasize the importance of accounting for coupling between different physical fields such as thermal, electromechanical, and magnetic, as well as of additional nonlinear and nonlocal effects which can be salient features of new applications and sensor designs. Our special attention is given to nanowires and nanotubes which are well suited for nanosensor designs and applications, being able to carry a double functionality, as transducers and the media to transmit the signal. One of the key properties of these nanostructures is an enhancement in sensitivity resulting from their high surface-to-volume ratio, which leads to their geometry-dependant properties. This dependency requires careful consideration at the modelling stage, and we provide further details on this issue. Another important class of sensors analyzed here is pertinent to sensor and actuator technologies based on smart materials. The modelling of such materials in their dynamics-enabled applications represents a significant challenge as we have to deal with strongly nonlinear coupled problems, accounting for dynamic interactions between different physical fields and microstructure evolution. Among other classes, important in novel sensor applications, we have given our special attention to heterostructures and nucleic acid based nanostructures. In terms of the application areas, we have focused on chemical and biomedical fields, as well as on green energy and environmentally-friendly technologies where the efficient designs and opportune deployments of sensors are both urgent and compelling.
      Citation: Chemosensors
      PubDate: 2022-04-25
      DOI: 10.3390/chemosensors10050157
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 158: Label-Free ZnIn2S4/UiO-66-NH2 Modified
           Glassy Carbon Electrode for Electrochemically Assessing Fish Freshness by
           Monitoring Xanthine and Hypoxanthine

    • Authors: Debin Song, Qiaowei Chen, Chunyang Zhai, Hengcong Tao, Lina Zhang, Tianbo Jia, Zhiwang Lu, Wuyang Sun, Pengxiang Yuan, Baikang Zhu
      First page: 158
      Abstract: Considering that simultaneous detection of xanthine (XA) and hypoxanthine (HXA) has been proved to be a reliable and feasible method for assessing fish freshness, a novel electrochemical sensing platform based on the ZnIn2S4/UiO-66-NH2 modified glassy carbon electrode (GCE) was constructed in this study for XA and HXA determination. X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR) were performed to exhibit the morphology and structural characteristics of ZnIn2S4/UiO-66-NH2. The Brunauer–Emmett–Teller (BET) displayed that the introduction of UiO-66-NH2 can improve the specific surface area of the hybrid. Besides, the electrochemical sensing performance of ZnIn2S4/UiO-66-NH2 was evaluated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). For simultaneously detecting XA and HXA, the fabricated electrochemical sensor shows wide linear ranges (0.025–40 µM and 0.3–40 µM) with low detection limits (0.0083 µM and 0.1 µM). This sensor also has 96–103% recovery in detecting XA and HXA content in large yellow croaker meat samples, demonstrating a promising application in the marine food industry.
      Citation: Chemosensors
      PubDate: 2022-04-25
      DOI: 10.3390/chemosensors10050158
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 159: Digital Detection of Olive Oil Rancidity
           Levels and Aroma Profiles Using Near-Infrared Spectroscopy, a Low-Cost
           Electronic Nose and Machine Learning Modelling

    • Authors: Claudia Gonzalez Viejo, Sigfredo Fuentes
      First page: 159
      Abstract: The success of the olive oil industry depends on provenance and quality-trait consistency affecting the consumers' acceptability/preference and purchase intention. Companies rely on laboratories to analyze samples to assess consistency within the production chain, which may be time-consuming, cost-restrictive, and untimely obtaining results, making the process more reactive than predictive. This study proposed implementing digital technologies using near-infrared spectroscopy (NIR) and a novel low-cost e-nose to assess the level of rancidity and aromas in commercial extra-virgin olive oil. Four different olive oils were spiked with three rancidity levels (N = 17). These samples were evaluated using gas-chromatography-mass-spectroscopy, NIR, and an e-nose. Four machine learning models were developed to classify olive oil types and rancidity (Model 1: NIR inputs; Model 2: e-nose inputs) and predict the peak area of 16 aromas (Model 3: NIR; Model 4: e-nose inputs). The results showed high accuracies (Models 1–2: 97% and 87%; Models 3–4: R = 0.96 and 0.93). These digital technologies may change companies from a reactive to a more predictive production of food/beverages to secure product quality and acceptability.
      Citation: Chemosensors
      PubDate: 2022-04-26
      DOI: 10.3390/chemosensors10050159
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 160: Ratiometric Fluorescence Probe of
           Vesicle-like Carbon Dots and Gold Clusters for Quantitation of Cholesterol

    • Authors: Shun-Ruei Hu, Chang-Ruei Yang, Yu-Fen Huang, Chih-Ching Huang, Yen-Ling Chen, Huan-Tsung Chang
      First page: 160
      Abstract: We report a facile method for the preparation of vesicle-like carbon dots (VCDs) via dry-heating of surfactant solutions. Like most reported CDs, the VCDs possess interesting fluorescence properties. Entrapment of enzymes and gold nanoclusters (AuNCs) inside the VCDs allows for the development of fluorescent probes for the quantitation of various substrates, with the advantages of high sensitivity and selectivity. The AuNCs act as a probe, and the VCDs as an internal standard confine the AuNCs, enzyme, and analyte to provide high local concentrations to enhance the assay sensitivity. In this study, we employed cholesterol oxidase (ChOX) as a model enzyme for the quantitation of cholesterol. The as-formed hydrogen peroxide through the enzyme reaction inside the VCDs causes fluorescence quenching of AuNCs (excitation/emission wavelengths of 320/670 nm), but not that of the VCDs (excitation/emission wavelengths of 320/400 nm). To improve the sensitivity and linearity, the fluorescence ratios of AuNCs/VCDs are plotted against analyte concentration. The present ratiometric fluorescent method allows for the detection of hydrogen peroxide over the concentration range of 1–100 μM, with a detection limit of 0.673 μM, and cholesterol concentrations ranging from 5 to 100 μM, with a detection limit of 2.8 μM. The practicality of this fluorescent method has been further validated by evaluating cholesterol levels in human serum samples with sufficient accuracy and recovery, revealing its great prospective in diagnosis and biomedical applications.
      Citation: Chemosensors
      PubDate: 2022-04-27
      DOI: 10.3390/chemosensors10050160
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 161: Water Quality Carbon Nanotube-Based
           Sensors Technological Barriers and Late Research Trends: A Bibliometric

    • Authors: Ana-Maria Nasture, Eusebiu Ilarian Ionete, Florin Alexandru Lungu, Stefan Ionut Spiridon, Laurentiu Gabriel Patularu
      First page: 161
      Abstract: Water is the key element that defines and individualizes our planet. Relative to body weight, water represents 70% or more for the majority of all species on Earth. Taking care of water as a whole is equivalent with taking care of the entire biodiversity or the whole of humanity itself. Water quality is becoming an increasingly important component of terrestrial life, hence intensive work is being conducted to develop sensors for detecting contaminants and assessing water quality and characteristics. Our bibliometric analysis is focused on water quality sensors based on carbon nanotubes and highlights the most important objectives and achievements of researchers in recent years. Due to important measurement characteristics such as sensitivity and selectivity, or low detection limit and linearity, up to the ability to measure water properties, including detection of heavy metal content or the presence of persistent organic compounds, carbon nanotube (CNT) sensors, taking advantage of available nanotechnologies, are becoming increasingly attractive. The conducted bibliometric analysis creates a visual, more efficient keystones mapping. CNT sensors can be integrated into an inexpensive real-time monitoring data acquisition system as an alternative for classical expensive and time-consuming offline water quality monitoring. The conducted bibliometric analysis reveals all connections and maps all the results in this water quality CNT sensors research field and gives a perspective on the approached methods on this specific type of sensor. Finally, challenges related to integration of other trends that have been used and proven to be valuable in the field of other sensor types and capable to contribute to the development (and outlook) for future new configurations that will undoubtedly emerge are presented.
      Citation: Chemosensors
      PubDate: 2022-04-27
      DOI: 10.3390/chemosensors10050161
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 162: Comparative Studies of
           Undoped/Al-Doped/In-Doped ZnO Transparent Conducting Oxide Thin Films in
           Optoelectronic Applications

    • Authors: Panagiota Koralli, Songül Fiat Fiat Varol, George Mousdis, Dionysios E. Mouzakis, Ziya Merdan, Michael Kompitsas
      First page: 162
      Abstract: In this paper, undoped, Al-, and In-doped zinc oxide thin films were deposited. Film growth was performed using the sol–gel technique. The method included (a) preparing homogeneous and stable solutions of zinc acetate 2-hydrate, (b) mixing them with aluminum nitrate and indium acetate in 2-methoxyethanol and 2-aminoethanol solutions with various concentrations, and (c) spin coating them onto transparent glass substrates. After thermal annealing, the films showed a high transparency (80–90%) and good stability. Using typical diagnostic tools, the structural, morphological, optical, and electrical film properties were investigated and linked to the dopant type, and concentrations in view of optoelectronics were investigated.
      Citation: Chemosensors
      PubDate: 2022-04-28
      DOI: 10.3390/chemosensors10050162
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 163: Green Synthesis of ZnO/BC Nanohybrid for
           Fast and Sensitive Detection of Bisphenol A in Water

    • Authors: Jiafeng Hu, Dongpeng Mao, Penghu Duan, Kelan Li, Yuqing Lin, Xinyao Wang, Yunxian Piao
      First page: 163
      Abstract: A nanohybrid of zinc oxide and biochar (ZnO/BC) with high conductivity was green synthesized using a simple hydrothermal method, and utilized for the sensitive detection of bisphenol A (BPA) by coating the nanohybrid film on an electrode of glassy carbon. The ZnO/BC presented greatly improved electrocatalytic performance and electron transfer ability compared to the zinc oxide and biochar. The ZnO/BC film-coated electrode could detect the BPA in aqueous solution within 3 min while neglected interference from higher concentrations of regularly existing ions and similar concentrations of estradiol (E2), phenol, dichlorophenol (DCP), and ethinylestradiol (EE2). Under optimal conditions, the linear range of BPA detection was 5 × 10−7~1 × 10−4 mol/L, with a detection limit of 1 × 10−7 mol/L, and the detection sensitivity was 92 mA/M. In addition, the ZnO/BC electrode could detect BPA in a real water sample with good signal recovery. This electrode, with the advantages of an easy preparation, low cost, and fast response time, could be potentially applicable for environmental monitoring.
      Citation: Chemosensors
      PubDate: 2022-04-28
      DOI: 10.3390/chemosensors10050163
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 164: A Long Short-Term Memory Neural Network
           Based Simultaneous Quantitative Analysis of Multiple Tobacco Chemical
           Components by Near-Infrared Hyperspectroscopy Images

    • Authors: Zhiqin Zhu, Guanqiu Qi, Yangbo Lei, Daiyu Jiang, Neal Mazur, Yang Liu, Di Wang, Wei Zhu
      First page: 164
      Abstract: Near-infrared (NIR) spectroscopy has been widely used in agricultural operations to obtain various crop parameters, such as water content, sugar content, and different indicators of ripeness, as well as other potential information concerning crops that cannot be directly obtained by human observation. The chemical compositions of tobacco play an important role in the quality of cigarettes. The NIR spectroscopy-based chemical composition analysis has recently become one of the most effective methods in tobacco quality analysis. Existing NIR spectroscopy-related solutions either have relatively low analysis accuracy, or are only able to analyze one or two chemical components. Thus, a precise prediction model is needed to improve the analysis accuracy of NIR data. This paper proposes a tobacco chemical component analysis method based on a neural network (TCCANN) to quantitatively analyze the chemical components of tobacco leaves by using NIR spectroscopy, including nicotine, total sugar, reducing sugar, total nitrogen, potassium, chlorine, and pH value. The proposed TCCANN consists of both residual network (ResNet) and long short-term memory (LSTM) neural network. ResNet is applied to the feature extraction of high-dimension NIR spectroscopy, which can effectively avoid the gradient-disappearance issue caused by the increase of network depth. LSTM is used to quantitatively analyze the multiple chemical compositions of tobacco leaves in a simultaneous manner. LSTM selectively allows information to pass through by a gated unit, thereby comprehensively analyzing the correlation between multiple chemical components and corresponding spectroscopy. The experimental results confirm that the proposed TCCANN not only predicts the corresponding values of seven chemical components simultaneously, but also achieves better prediction performance than other existing machine learning methods.
      Citation: Chemosensors
      PubDate: 2022-04-28
      DOI: 10.3390/chemosensors10050164
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 165: Au Functionalized SnS2 Nanosheets Based
           Chemiresistive NO2 Sensors

    • Authors: Ding Gu, Wei Liu, Jing Wang, Jun Yu, Jianwei Zhang, Baoyu Huang, Marina N. Rumyantseva, Xiaogan Li
      First page: 165
      Abstract: Layered Au/SnS2 nanosheet based chemiresistive-type sensors were successfully prepared by using an in situ chemical reduction method followed by the hydrothermal treatment. SEM and XRD were used to study the microscopic morphology and crystal lattice structure of the synthesis of Au/SnS2 nanomaterials. TEM and XPS characterization were further carried out to verify the formation of the Schottky barrier between SnS2 nanosheets and Au nanoparticles. The as-fabricated Au/SnS2 nanosheet based sensor demonstrated excellent sensing properties to low-concentrations of NO2, and the response of the sensor to 4 ppm NO2 at 120 °C was approximately 3.94, which was 65% higher than that of the pristine SnS2 (2.39)-based sensor. Moreover, compared to that (220 s/520 s) of the pristine SnS2-based sensor, the response/recovery time of the Au/SnS2-based one was significantly improved, reducing to 42 s/127 s, respectively. The sensor presents a favorable long-term stability with a deviation in the response of less than 4% for 40 days, and a brilliant selectivity to several possible interferents such as NH3, acetone, toluene, benzene, methanol, ethanol, and formaldehyde. The Schottky barrier that formed at the interface between the SnS2 nanosheets and Au nanoparticles modulated the conducting channel of the nanocomposites. The “catalysis effect” and “spillover effect” of noble metals jointly improved the sensitivity of the sensor and effectively decreased the response/recovery time.
      Citation: Chemosensors
      PubDate: 2022-04-28
      DOI: 10.3390/chemosensors10050165
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 166: Elucidation of Response Mechanism of a
           Potentiometric Sweetness Sensor with a Lipid/Polymer Membrane for
           Uncharged Sweeteners

    • Authors: Zihong Ye, Tianci Ai, Xiao Wu, Takeshi Onodera, Hidekazu Ikezaki, Kiyoshi Toko
      First page: 166
      Abstract: Nowadays, the utilization of a taste sensor with lipid/polymer membranes is one of the most accurate and objective ways to evaluate the tastes of solutions. However, it has been difficult to evaluate uncharged sweet substances, such as sucrose, because the conventional taste sensor uses the potentiometric measurement, which is mainly based on changes in the surface electric charge density of the membrane. Previous studies have reported that a sweetness sensor called GL1 can evaluate the sweetness of sugars and sugar alcohols, and is commercially available for food, beverage, and pharmaceutical industries. However, the response mechanism of GL1 has not been fully elucidated. In this study, we focus on clarifying the effect of concentrations and types of metal ions in the conditioning solution on the response mechanism of the sweetness sensor GL1. Moreover, according to the different concentrations and types of metal ions in conditioning solutions, the complex formation and the hydrated radius were considered to influence the membrane potential measured in a reference solution and the sensor responses. The purpose of this study is to elucidate the response mechanism and improve the selectivity and sensitivity of the sweetness sensor.
      Citation: Chemosensors
      PubDate: 2022-04-28
      DOI: 10.3390/chemosensors10050166
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 167: Breath Biomarkers as Disease Indicators:
           Sensing Techniques Approach for Detecting Breath Gas and COVID-19

    • Authors: Zoltan-Mihály Török, Arthur Frederic Blaser, Kiana Kavianynejad, Carlos Gonzalo Moya Gual de Torrella, Lawrence Nsubuga, Yogendra Kumar Mishra, Horst-Günter Rubahn, Roana de Oliveira Hansen
      First page: 167
      Abstract: Extensive research shows that there is a close correlation between a disease diagnostic and the patient’s exhale breath gas composition. It has been demonstrated, for example, that patients with a diabetes diagnosis have a certain level of acetone fume in their exhale breath. Actually, symptoms from many other diseases could be easily diagnosed if appropriate and reliable gas sensing technologies are available. The COVID-19 pandemic has created demand for a cheap and quick screening tool for the disease, where breath biomarker screening could be a very promising approach. It has been shown that COVID-19 patients potentially present a simultaneous increase in ethanal (acetaldehyde) and acetone in their exhale breath. In this paper, we explore two different sensing approaches to detect ethanal/acetone, namely by colorimetric markers, which could for example be integrated into facemasks, and by a breathalyzer containing a functionalized quartz crystal microbalance. Both approaches can successfully detect the presence of a biomarker gas on a person’s breath and this could potentially revolutionize the future of healthcare in terms of non-invasive and early-stage detection of various diseases.
      Citation: Chemosensors
      PubDate: 2022-04-29
      DOI: 10.3390/chemosensors10050167
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 168: Exploring the Adsorption of Pb on
           Microalgae-Derived Biochar: A Versatile Material for Environmental
           Remediation and Electroanalytical Applications

    • Authors: Gilberto Binda, Davide Faccini, Martina Zava, Andrea Pozzi, Carlo Dossi, Damiano Monticelli, Davide Spanu
      First page: 168
      Abstract: Biochar, a carbon material obtained by pyrolysis of biomasses, is increasingly applied in environmental remediation and sensing thanks to its functional properties, cost-effectiveness and eco-friendliness. The adsorption capacity of biochar, strictly dependent on its specific surface area, heteroatom doping and surface functional groups, is crucial for these applications. Here, biochar produced at low temperature (350 °C) from a marine microalga (Nannochloropsis sp.) is proposed as an efficient adsorbent of lead (II) ions in aqueous solution; this production strategy promotes the natural self-doping of biochar without requiring harsh conditions. The kinetics and thermodynamics of the adsorption process, as well as the effect of pH, ionic strength and dissolved organic matter on the adsorption efficiency were systematically assessed. The microalgae-derived biochar shows superior adsorption performances compared to a nutshell-derived one (used as a reference of lignocellulosic feedstocks) under all the tested conditions. The microalgae-derived biochar was finally used to decorate screen-printed carbon electrodes to improve the electroanalytical performances towards the voltammetric detection of lead (II) ions. A two-fold increase in sensitivity was obtained compared to the unmodified electrode thanks to the enhanced electron transfer and adsorption properties provided by biochar. These results highlight the potentialities of microalgae-derived biochar for environmental and sensing applications.
      Citation: Chemosensors
      PubDate: 2022-04-30
      DOI: 10.3390/chemosensors10050168
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 169: A Laser-Induced Photoelectrochemical
           Sensor for Natural Sweat Cu2+ Detection

    • Authors: Shubo Zhang, Yanwen Liu, Juan Wang, Zhihong Liu
      First page: 169
      Abstract: Tracking fluctuations in the Cu2+ level in sweat is meaningful for non-invasive and real-time assessment of Cu2+-abnormality-related diseases and provides important diagnostic information. However, the user-unfriendly ways to obtain sweat and sweat biofouling have limited the development of this field. Herein, we exploit a highly sensitive photoelectrochemical (PEC) sensor as a detection method, a powerful laser engraving technique for the large-scale fabrication of laser-induced graphene and In-doped CdS (LIG-In-CdS) photoelectrodes, and a hydrophilic porous polyvinyl alcohol (PVA) hydrogel for natural sweat collection for fingertip touch sweat Cu2+ monitoring. The proposed sensor has several very attractive features: (i) the LIG-In-CdS photoelectrode with high photoelectric conversion efficiency can be produced by a cheap 450 nm semiconductor laser system; (ii) the sensor performs Cu2+ detection with a wide linear range of 1.28 ng/mL~5.12 μg/mL and good selectivity; (iii) the PVA hydrogel possesses an excellent antifouling effect ability and a rapid natural sweat collection ability; and (iv) the sensor exhibits feasibility and good reliability for PEC sensing of sweat Cu2+. Thus, these advantages endow the proposed method with a great deal of potential for smart monitoring of heavy metals in sweat in the future.
      Citation: Chemosensors
      PubDate: 2022-05-02
      DOI: 10.3390/chemosensors10050169
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 170: Photoluminescence Sensing of Chloride
           Ions in Sea Sand Using Alcohol-Dispersed CsPbBr3@SiO2 Perovskite
           Nanocrystal Composites

    • Authors: Henggan Li, Feiming Li, Yipeng Huang, Linchun Zhang, Min Ye, Jingwen Jin, Xi Chen
      First page: 170
      Abstract: In this study, CsPbBr3@SiO2 perovskite nanocrystal composites (CsPbBr3@SiO2 PNCCs) were synthesized by a benzyl bromide nucleophilic substitution strategy. Homogeneous halide exchange between CsPbBr3@SiO2 PNCCs and Cl− solution (aqueous phase) was applied to the determination of Cl− in sea sand samples. Fast halide exchange with Cl− in the aqueous phase without any magnetic stirring or pH regulation resulted in the blue shift of the photoluminescence (PL) wavelength and vivid PL color changes from green to blue. The results show that the PL sensing of Cl− in aqueous samples could be implemented by using the halide exchange of CsPbBr3@SiO2 PNCCs. A linear relationship between the PL wavelength shift and the Cl− concentration in the range of 0 to 3.0% was found, which was applied to the determination of Cl− concentration in sea sand samples. This method greatly simplifies the detection process and provides a new idea for further broadening PL sensing using the CsPbBr3 PNC halide.
      Citation: Chemosensors
      PubDate: 2022-05-02
      DOI: 10.3390/chemosensors10050170
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 171: Origin of Baseline Drift in Metal Oxide
           Gas Sensors: Effects of Bulk Equilibration

    • Authors: Gerhard Müller, Giorgio Sberveglieri
      First page: 171
      Abstract: Metal oxide (MOX) gas sensors and gas sensor arrays are widely used to detect toxic, combustible, and corrosive gases and gas mixtures inside ambient air. Important but poorly researched effects counteracting reliable detection are the phenomena of sensor baseline drift and changes in gas response upon long-term operation of MOX gas sensors. In this paper, it is shown that baseline drift is not limited to materials with poor crystallinity, but that this phenomenon principally also occurs in materials with almost perfect crystalline order. Building on this result, a theoretical framework for the analysis of such phenomena is developed. This analysis indicates that sensor drift is caused by the slow annealing of quenched-in non-equilibrium oxygen-vacancy donors as MOX gas sensors are operated at moderate temperatures for prolonged periods of time. Most interestingly, our analysis predicts that sensor drift in n-type MOX materials can potentially be mitigated or even suppressed by doping with metal impurities with chemical valences higher than those of the core metal constituents of the host crystals.
      Citation: Chemosensors
      PubDate: 2022-05-02
      DOI: 10.3390/chemosensors10050171
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 172: Affinity-Recognition-Based Gravimetric
           Nanosensor for Equilin Detection

    • Authors: Gülgün Aylaz, Müge Andaç
      First page: 172
      Abstract: The estrogenic hormones that are widely used in postmenopausal hormone supplements for women contaminate natural water resources. Equilin (Equ) is one of the estrogenic hormones that have a maximum contaminant level of 0.35 µg/L in the chemical pollutants list. In this study, estrogenic hormones were precisely detected in a short time by affinity-recognition-based interactions in Quartz Crystal Microbalance (QCM) sensors. The QCM sensors were modified with 11-mercaptoundecanoic acid forming a self-assembled monolayer and with amino acids, namely tyrosine, tryptophan and phenylalanine. The affinity interactions between Equ and amino acids were studied using docking tools and confirmed by QCM experiments. The LODs of Equ were obtained as 4.59, 5.05 and 6.30 ng/L for tyrosine-, tryptophan- and phenylalanine-modified QCM nanosensors, respectively, with linear dynamic detection in the range of 25–500 nM. In terms of the LOD, selectivity and sensitivity calculations, the tyrosine-modified QCM nanosensor was found to have the highest performance for Equ detection compared to the tryptophan- and phenylalanine-modified ones.
      Citation: Chemosensors
      PubDate: 2022-05-03
      DOI: 10.3390/chemosensors10050172
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 173: A Cell Co-Culture Taste Sensor Using
           Different Proportions of Caco-2 and SH-SY5Y Cells for Bitterness Detection

    • Authors: Chunlian Qin, Saisai Zhang, Qunchen Yuan, Mengxue Liu, Nan Jiang, Liujing Zhuang, Liquan Huang, Ping Wang
      First page: 173
      Abstract: Bitter taste receptors (T2Rs) are involved in bitter taste perception, which is one of the five basic taste modalities in mammals. In this study, a cell co-culture taste sensor using different proportions of Caco-2 cells and SH-SY5Y cells was proposed. Caco-2 cells, which endogenously expressed the human T2R38 receptor, and SH-SY5Y cells, which endogenously expressed the human T2R16 receptor, were co-cultured. Using Caco-2 cells and SH-SY5Y cells at a constant total concentration of 40 K/mL, we designed seven mixtures with [Caco-2]/([Caco-2] + [SH-SY5Y]) ratios of 0, 20, 40, 50, 60, 80, and 100%. These mixtures were then seeded on the 16 E-plates of the electric cell-substrate impedance sensor (ECIS) for bitterness detection. Theoretically, after T2R38 ligands activation, continuous evolution profiles (CEP), with [Caco-2]/([Caco-2] + [SH-SY5Y]) ratios as the x-axis and ΔCI (Max) as the y-axis, would exhibit positive correlation property. After T2R16 ligands activation, the CEP would show negative correlation property. However, when stimulated with compounds that could activate both T2R16 and T2R38, it would show different response patterns.
      Citation: Chemosensors
      PubDate: 2022-05-05
      DOI: 10.3390/chemosensors10050173
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 174: Development of a Coelenterazine
           Derivative with Enhanced Superoxide Anion-Triggered Chemiluminescence in
           Aqueous Solution

    • Authors: José Pedro Silva, Patricia González-Berdullas, Joaquim C. G. Esteves da Silva, Luís Pinto da Silva
      First page: 174
      Abstract: Superoxide anion is a reactive oxygen species (ROS) of biological interest. More specifically, it plays a role in intra- and intercellular signaling, besides being associated with conditions such as inflammation and cancer. Given this, efforts have been made by the research community to devise new sensing strategies for this ROS species. Among them, the chemiluminescent reaction of marine Coelenterazine has been employed as a sensitive and dynamic probing approach. Nevertheless, chemiluminescent reactions are typically associated with lower emissions in aqueous solutions. Herein, here we report the synthesis of a new Coelenterazine derivative with the potential for superoxide anion sensing. Namely, this novel compound is capable of chemiluminescence in a dose-dependent manner when triggered by this ROS species. More importantly, the light-emission intensities provided by this derivative were relevantly enhanced (intensities 2.13 × 101 to 1.11 × 104 times higher) in aqueous solutions at different pH conditions when compared to native Coelenterazine. The half-life of the chemiluminescent signal is also greatly increased for the derivative. Thus, a new chemiluminescence molecule with significant potential for superoxide anion sensing was discovered and reported for the first time.
      Citation: Chemosensors
      PubDate: 2022-05-05
      DOI: 10.3390/chemosensors10050174
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 175: Microwave-Assisted Synthesis of Schiff
           Base Metal–Ligand Complexes with Copper and Nickel Centres for
           Electrochemical In Vitro Sensing of Nitric Oxide in an Aqueous Solution

    • Authors: Teboho N. Moeketse, Priscilla G. Baker, Al. C. Farao, Emmanuel I. Iwuoha
      First page: 175
      Abstract: Nitric oxide (NO), the smallest signalling molecule known in the human body, keeps blood vessels dilated, controls blood pressure, and has numerous other health regulatory effects. The use of Schiff base complexes incorporated onto electrodes to make electrochemical sensors has been explored as an effective method for the determination and quantification of nitric oxide in aqueous solutions. Schiff base ligands were complexed with Cu and Ni metal centres using the microwave synthesis method to produce metal–ligand complexes with enhanced capabilites for NO detection. The electrical current generated at the anode is directly proportional to NO concentrations in the solution through its oxidation to HNO3. Various characterisation techniques were implemented to verify the integrity of each step of metal–ligand synthesis as well as the final product produced, using FT-IR, UV-VIS, and TGA. The as-synthesised Schiff base complexes were electrodeposited on screen-printed carbon electrodes (SPCE) and electrochemically evaluated in a 0.1 M PBS. Furthermore, metal complexes were screened for their in vitro activity towards NO detection in an aqueous solution (PBS). The results show that the investigated sensors (SPCE/Ni-BPND and SPCE/Cu-BPND) respond positively toward NO detection. It was, therefore, identified that the two sensors also do not differ significantly in terms of precision, sensitivity, and lowest detection limit. The sensor strategies demonstrate the NO limits of detection of 0.22 µM and 0.09 µM, and they also demonstrate sensitivity values of 16.3 µA/µM and 13.1 µA/µM for SPCE/Cu-BPND and SPCE/Ni-BPND sensors, respectively.
      Citation: Chemosensors
      PubDate: 2022-05-06
      DOI: 10.3390/chemosensors10050175
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 176: Luminescent Self-Assembled Monolayer on

    • Authors: Angela Candreva, Giuseppe Di Maio, Francesco Parisi, Francesca Scarpelli, Alessandra Crispini, Nicolas Godbert, Loredana Ricciardi, Antonello Nucera, Carmen Rizzuto, Riccardo C. Barberi, Marco Castriota, Massimo La Deda
      First page: 176
      Abstract: Until now, the ability to form a self-assembled monolayer (SAM) on a surface has been investigated according to deposition techniques, which in turn depend on surface-coater interactions. In this paper, we pursued two goals: to form a SAM on a gold nanosurface and to correlate its formation to the nanosurface curvature. To achieve these objectives, gold nanoparticles of different shapes (spheres, rods, and triangles) were functionalized with a luminescent thiolated bipyridine (Bpy-SH), and the SAM formation was studied by investigating the photo-physics of Bpy-SH. We have shown that emission wavelength and excited-state lifetime of Bpy-SH are strongly correlated to the formation of specific aggregates within SAMs, the nature of these aggregates being in close correlation to the shape of the nanoparticles. Micro-Raman spectroscopy investigation was used to test the SERS effect of gold nanoparticles on thiolated bipyridine forming SAMs.
      Citation: Chemosensors
      PubDate: 2022-05-06
      DOI: 10.3390/chemosensors10050176
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 177: A Microphysiometric System Based on LAPS
           for Real-Time Monitoring of Microbial Metabolism

    • Authors: Nan Jiang, Tao Liang, Chunlian Qin, Qunchen Yuan, Mengxue Liu, Liujing Zhuang, Ping Wang
      First page: 177
      Abstract: Macronutrients (carbohydrates, fat and protein) are the cornerstones of daily diet, among which carbohydrates provide energy for the muscles and central nervous system during movement and exercise. The breakdown of carbohydrates starts in the oral cavity, where they are primarily hydrolyzed to glucose and then metabolized to organic acids. The end products may have an impact on the oral microenvironment, so it is necessary to monitor the process of microbial metabolism and to measure the pH change. Although a pH meter has been widely used, it is limited by its sensitivity. We then introduce a light addressable potentiometric sensor (LAPS), which has been used in extracellular acidification detection of living cells with the advantages of being objective, quantitative and highly sensitive. However, it is difficult to use in monitoring bacterial metabolism because bacteria cannot be immobilization on the LAPS chip as easily as living cells. Therefore, a microphysiometric system integrated with Transwell insert and microfluidic LAPS chip was designed and constructed to solve this problem. The decrease in pH caused by glucose fermentation in Lactobacillus rhamnosus was successfully measured by this device. This proves the feasibility of the system for metabolism detection of non-adhere targets such as microorganisms and even 3D cells and organoids.
      Citation: Chemosensors
      PubDate: 2022-05-06
      DOI: 10.3390/chemosensors10050177
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 178: Theoretical Study on the Electrochemical
           Catalytic Activity of Au-Doped Pt Electrode for Nitrogen Monoxide

    • Authors: Yumei Li, Huijia Hu, Weifeng Zhang, Ziqi Tian, Xiaoqing Jiang, Yuheng Wang, Shaolin Zhang, Qiuju Zhang, Jiawen Jian, Jie Zou
      First page: 178
      Abstract: In order to gradually reduce automobile exhaust pollution and improve fuel quality, the NOx sensor, which can be monitored in real time in an automobile engine’s electronic control system, has become an indispensable part of the automobile lean burn system. In these types of NOx sensors, Au-doped platinum electrodes have received great attention due to their selectivity towards NO. However, the reaction process of NO gas on the Au-doped platinum electrode in the sensor and the possible regulation mechanism is still unclear. In this paper, the density functional theory (DFT) was used to analyze the effect of Au-doped Pt electrodes on the performance of nitrogen oxide sensors in automobiles. Firstly, the adsorption energies of NO molecules on pure Pt and Au/Pt surfaces were compared. The adsorption and dissociation of NO on Pt substrates doped with Au monomers, dimers, and trimers were investigated. These results showed that Au can effectively weaken the adsorption energy of NO molecules on a Pt surface. It was noted that with the increase in the number of Au atoms on the surface of Pt(111), the adsorption capacity of NO molecules on the alloy surface becomes weaker. When observing the transition state of NO decomposition on three different alloy surfaces, the study showed that the activation energy and reaction heat of NO dissociation increased. It further showed that doping with Au increased the activation energy of NO decomposition, thereby effectively inhibiting the decomposition of NO.
      Citation: Chemosensors
      PubDate: 2022-05-07
      DOI: 10.3390/chemosensors10050178
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 179: Wireless Volatile Organic Compound
           Detection for Restricted Internet of Things Environments Based on
           Cataluminescence Sensors

    • Authors: Xinyi Shen, Guolong Shi, Yongxing Zhang, Shizhuang Weng
      First page: 179
      Abstract: Cataluminescence-based sensors do not require external light sources and complex circuitry, which enables them to avoid light scattering with high sensitivity, selectivity, and widely linear range. In this study, a wireless sensor system based on hierarchical CuO microspheres assembled from nano-sheets was constructed for Volatile Organic Compound (VOC) online detection. Through sensor characteristics and data process analysis, the results showed that the luminous sensor system has good luminous characteristics, including the intensity of visible light, high signal/noise (S/N) values, and very short response and recovery times. Different VOC concentration values can be detected on multiple wavelength channels and different Cataluminescence signal spectra separations can process multiple sets of Cataluminescence data combinations concurrently. This study also briefly studied the mechanism action of the Cataluminescence sensor, which can specifically be used for VOC detecting.
      Citation: Chemosensors
      PubDate: 2022-05-09
      DOI: 10.3390/chemosensors10050179
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 180: Determination of Ascorbic Acid in
           Pharmaceuticals and Food Supplements with the New Potassium
           Ferrocyanide-Doped Polypyrrole-Modified Platinum Electrode Sensor

    • Authors: Ancuța Dinu, Constantin Apetrei
      First page: 180
      Abstract: This paper reports the results obtained from the determination of ascorbic acid with platinum-based voltammetric sensors modified with potassium hexacyanoferrate-doped polypyrrole. The preparation of the modified electrodes was carried out by electrochemical polymerization of pyrrole from aqueous solutions, using chronoamperometry. Polypyrrole films were deposited on the surface of the platinum electrode, by applying a constant potential of 0.8 V for 30 s. The thickness of the polymer film was calculated from the chronoamperometric data, and the value was 0.163 μm. Cyclic voltammetry was the method used for the Pt/PPy-FeCN electrode electrochemical characterization in several types of solution, including KCl, potassium ferrocyanide, and ascorbic acid. The thin doped polymer layer showed excellent sensitivity for ascorbic acid detection. From the voltammetric studies carried out in solutions of different concentrations of ascorbic acid, ranging from 1 to 100 × 10−6 M, a detection limit of 2.5 × 10−7 M was obtained. Validation of the analyses was performed using pharmaceutical products with different concentrations of ascorbic acid, from different manufacturers and presented in various pharmaceutical forms, i.e., intravascular administration ampoules, chewable tablets, and powder for oral suspension.
      Citation: Chemosensors
      PubDate: 2022-05-09
      DOI: 10.3390/chemosensors10050180
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 181: Couplants in Acoustic Biosensing Systems

    • Authors: Rayyan Manwar, Loїc Saint-Martin, Kamran Avanaki
      First page: 181
      Abstract: Acoustic biosensors are widely used in physical, chemical, and biosensing applications. One of the major concerns in acoustic biosensing is the delicacy of the medium through which acoustic waves propagate and reach acoustic sensors. Even a small airgap diminishes acoustic signal strengths due to high acoustic impedance mismatch. Therefore, the presence of a coupling medium to create a pathway for an efficient propagation of acoustic waves is essential. Here, we have reviewed the chemical, physical, and acoustic characteristics of various coupling material (liquid, gel-based, semi-dry, and dry) and present a guide to determine a suitable application-specific coupling medium.
      Citation: Chemosensors
      PubDate: 2022-05-09
      DOI: 10.3390/chemosensors10050181
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 182: Fabrication of Functional
           Super-Hydrophilic TiO2 Thin Film for pH Detection

    • Authors: Cheng Chen, Yalei Zhang, Han Gao, Kun Xu, Xiliang Zhang
      First page: 182
      Abstract: A super-hydrophilic pH-sensitive electrode with a porous TiO2 thin film is proposed in this work and fabricated using the chemical etching method. In total, 30 groups of porous TiO2 thin film were obtained by immersing a Ti sheet in NaOH, with the solution concentration ranging from 0.5–4 M and the reaction time ranging from 15–240 min. SEM, XRD, XPS, and a contact angle meter were used to investigate the influence of the chemical etching parameters on the morphology, composition, and wettability of the fabricated electrodes. The chemical etching parameters were found to have a significant influence on the specific surface area and the component of the films, which strongly affected the wettability and pH sensing characteristics of the electrodes. The electrode obtained with a solution concentration of 1 M and reaction time of 120 min is the ideal product because of its excellent wettability, with a contact angle of 5.46°, and good pH sensing characteristics in pH buffer solutions. The electrode also showed good stability regarding its wettability and pH sensing properties during storage and utilization.
      Citation: Chemosensors
      PubDate: 2022-05-11
      DOI: 10.3390/chemosensors10050182
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 183: Spectroscopic Recognition of Metal Ions
           and Non-Linear Optical (NLO) Properties of Some Fluorinated

    • Authors: Mihaela Homocianu, Anton Airinei, Alina Mirela Ipate, Corneliu Hamciuc
      First page: 183
      Abstract: In this paper, we examined the sensing ability of some fluorinated 1,3,4-oxadiazole-containing assemblies toward various metal ions and their nonlinear optical (NLO) properties. The changes in the spectral characteristics of these compounds in the existence of Mg2+, Mn2+, Ni2+, Cd2+, Zn2+, Co2+, Cu2+, Hg2+, Sn2+, and Ag+ metal ions were performed, and they were found to be selective and more sensitive toward the addition of Ag+, Co2+, and Cu2+ ions (new bands appeared). Instead, spectral changes in the presence of Mg2+, Mn2+, Ni2+, Cd2+, Zn2+, Hg2+, and Sn2+ were not significant, so we did not evaluate the corresponding binding parameters. Therefore, all of these compounds were found to be selective and sensitive to Ag+, Co2+, and Cu2+ ions. Furthermore, the first-order polarizability (αCT), the first-order hyperpolarizability (βCT), and the second-order hyperpolarizability (γCT) were evaluated using the solvatochromic approach, and the intramolecular charge transfer (ICT) characteristics were investigated using a generalized Mulliken–Hush (GMH) analysis.
      Citation: Chemosensors
      PubDate: 2022-05-11
      DOI: 10.3390/chemosensors10050183
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 184: Phage Display Affibodies Combined with
           AuNPs@Ru(bpy)32+ for Ultra-Sensitive Electrochemiluminescence Detection of

    • Authors: Shuai Liu, Zhaoyang Tong, Chunying Jiang, Chuan Gao, Jianjie Xu, Xihui Mu, Bing Liu, Bin Du, Zhiwei Liu, Pengjie Zhang
      First page: 184
      Abstract: Abrin is a cytotoxin with strong lethality, which is a serious threat to human health and public safety, and thus, highly sensitive detection methods are urgently needed. The phage display affibody has two major modules, among which, the affibody fragment, with small molecular weight, high affinity and easy preparation, can be used for the specific recognition of the target, and the phage shell, with numerous protein copies, can be used as a carrier for the massive enrichment of signal molecules, and thus is particularly suitable as a sensitive probe for signal amplification in high-sensitivity biosensors. In this study, with antibody-coated magnetic microspheres as capture probes, Ru(bpy)32+ and biotin dual-labeled phage display affibodies as the specific signal probes and AuNPs@Ru(bpy)32+ (Ru(bpy)32+-coated gold nanoparticles) as the signal amplification nanomaterials, a new electrochemiluminescence (ECL) biosensor with a four-level sandwich structure of “magnetic capture probe-abrin-phage display affibody-AuNPs@Ru(bpy)32+” was constructed for abrin detection. In this detection mode, AuNPs@Ru(bpy)32+, a gold nanocomposite prepared rapidly via electrical interaction, contained an extremely high density of signal molecules, and the phage display affibodies with powerful loading capacity were not only labeled with Ru(bpy)32+, but also enriched with AuNPs@Ru(bpy)32+ in large amounts. These designs greatly improved the detection capability of the sensor, ultimately achieving the ultra-sensitive detection of abrin. The limit of detection (LOD) was 4.1 fg/mL (3δ/S), and the quantification range was from 5 fg/mL to 5 pg/mL. The sensor had good reproducibility and specificity and performed well in the test of simulated samples. This study expanded the application of affibodies in the field of biosensing and also deeply explored the signal amplification potential of phage display technology, which is of high value for the construction of simple and efficient sensors with high sensitivity.
      Citation: Chemosensors
      PubDate: 2022-05-13
      DOI: 10.3390/chemosensors10050184
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 185: Cyanide Anion Determination Based on
           Nucleophilic Addition to

    • Authors: Miglė Dagilienė, Giedrė Markuckaitė, Sonata Krikštolaitytė, Algirdas Šačkus, Vytas Martynaitis
      First page: 185
      Abstract: This work provides a novel approach for the instant detection of CN− anions based on chromogenic 6-[(E)-(4-nitrophenyl)diazenyl]-1′,3,3′,4-tetrahydrospiro[chromene-2,2′-indole] derivatives. New colorimetric detectors were synthesized and characterized. These compounds exhibited a substantial color change from orange to magenta and blue when treated with cyanide ions in a CH3CN solution buffered with sodium phosphate and demonstrated high selectivity to CN− anions. Common anions were tested, and they did not interfere with cyanide detection, except for carbonates and hydrosulfites. The simple preparation of a molecular sensor and the easily noticeable color change makes this a practical system for the monitoring of CN− ions. This color change is explained by nucleophilic substitution of the pyrane ring oxygen atom at the indoline C-2 atom by the cyanide anion. This generates the appearance of intensively colored 4-(4-nitrophenylazo)phenolate chromophore and allows for determining very low levels of CN− anion.
      Citation: Chemosensors
      PubDate: 2022-05-14
      DOI: 10.3390/chemosensors10050185
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 186: A New Kind of Chemical Nanosensors for
           Discrimination of Espresso Coffee

    • Authors: Giuseppe Greco, Estefanía Núñez Carmona, Giorgio Sberveglieri, Dario Genzardi, Veronica Sberveglieri
      First page: 186
      Abstract: There are different methods to extract and brew coffee, therefore, coffee processing is an important factor and should be studied in detail. Herein, coffee was brewed by means of a new espresso professional coffee machine, using coffee powder or portioned coffee (capsule). Four different kinds of coffees (Biologico, Dolce, Deciso, Guatemala) were investigated with and without capsules and the goal was to classify the volatiloma of each one by Small Sensor System (S3). The response of the semiconductor metal oxide sensors (MOX) of S3 where recorded, for all 288 replicates and after normalization ∆R/R0 was extracted as a feature. PCA analysis was used to compare and differentiate the same kind of coffee sample with and without a capsule. It could be concluded that the coffee capsules affect the quality, changing on the flavor profile of espresso coffee when extracted different methods confirming the use of s3 device as a rapid and user-friendly tool in the food quality control chain.
      Citation: Chemosensors
      PubDate: 2022-05-16
      DOI: 10.3390/chemosensors10050186
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 187: Measurement of Pulsating Flow Using a
           Self-Attachable Flexible Strain Sensor Based on Adhesive PDMS and CNT

    • Authors: Chaehyun Ryu, Jeonhyeong Park, Soon In Jung, Il Ryu Jang, Hoe Joon Kim
      First page: 187
      Abstract: Accurate monitoring is needed for pulsating flow in many healthcare and bio applications. Specifically, real-time monitoring of pulsating blood flow provides rich information regarding a patient’s health conditions. This paper proposes a flexible strain sensor capable of detecting the pulsating fluid flow by directly measuring the circumferential strain induced by a rapid change in the flow rate. The thin and flexible strain sensor consists of a polydimethylsiloxane (PDMS) with a Triton-X treatment to enhance the adhesive property and multi-walled carbon nanotubes (MWCNT) as the piezoresistive sensing layer. MWCNT integration implements a simple spray-coating method. The adhesive PDMS/CNT strain sensor exhibits a highly adhesive nature and can be attached to a silicone tube’s curved surface. By analyzing the theoretical modeling based on fluid energy equation and solid mechanics, strains induced on the soft tube by the change in flow rate, viscosity, and fluid density can be predicted. We performed the flow rate measurement at varying fluid-flow rates and liquid viscosities, and the results match our prediction. The sensitivity and limit of detection of the presented strain sensor are about 0.55 %min/L and 0.4 L/min, respectively. Both the calculation and experiment confirm that the sensor resistance is most sensitive to the fluid-flow rate, thus, enabling the accurate tracking of pulsating fluids’ flow rate, regardless of the viscosity or density.
      Citation: Chemosensors
      PubDate: 2022-05-16
      DOI: 10.3390/chemosensors10050187
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 188: A New Benzoxazole-Based Fluorescent
           Macrocyclic Chemosensor for Optical Detection of Zn2+ and Cd2+

    • Authors: Daniele Paderni, Luca Giorgi, Maria Voccia, Mauro Formica, Lucia Caporaso, Eleonora Macedi, Vieri Fusi
      First page: 188
      Abstract: Background: Benzoxazole-containing ligands find many applications both in medicinal chemistry, catalysis and fluorescence chemosensing. Benzoxazole-containing macrocycles could be therefore a good strategy to achieve stable and selective fluorescent complexes with suitable metal ions. In this work, the synthesis, binding, and photochemical properties of a new fluorescent ligand (L) are reported. L is a cyclophane macrocycle containing the 1,3-bis(benzo[d]oxazol-2-yl)phenyl (BBzB) fluorophore and an aliphatic tetra-amine chain to form the macrocyclic skeleton. Methods: Spectrophotometric and spectrofluorimetric measurements, 1H NMR analysis, and DFT calculations were performed. Results: L behaves as a PET-mediated chemosensor, being emissive at 390 nm at acidic pH and non-emissive at basic pH. The chemosensor is able to detect Zn2+ and Cd2+ in an aqueous medium (acetonitrile–water, 4:1 v/v) at neutral pH through a CHEF effect upon metal ion coordination. Paramagnetic metal ions (Cu2+) and heavy atoms (Pb2+, Hg2+) resulted in a quenching of fluorescence or very low emission. Conclusions: The new cyclophane macrocycle L was revealed to be a selective PET-regulated chemosensor for Zn2+ and Cd2+ in an aqueous medium, being able to bind up to two and one metal cations, respectively. The molecule showed a shifted emission towards the visible region compared to similar systems, suggesting a co-planar conformation of the aromatic fragment upon metal coordination. All these data are supported by both experimental measurements and theoretical calculations.
      Citation: Chemosensors
      PubDate: 2022-05-17
      DOI: 10.3390/chemosensors10050188
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 189: Carbon Electrodes with Gold
           Nanoparticles for the Electrochemical Detection of miRNA 21-5p

    • Authors: Verónica Morgado Serrano, Inês Simões Patrício Silva, Ana Rita Cardoso, Maria Goreti Ferreira Sales
      First page: 189
      Abstract: Extracellular vesicles are involved in many physiological and pathological activities. They transport miRNAs to recipient cells during their role in intercellular communication, making them emerging biomarkers of many diseases. Interest in exosomal miRNAs has grown after they have shown numerous advantages as biomarkers for diagnosis, prognosis, and evaluation of cancer treatment. This work describes the development of a biosensor for the detection of 21-5p miRNA in human serum using screen-printed carbon electrodes modified with gold nanoparticles fabricated in situ, an innovative approach to avoid the use of more expensive gold substrates that provide better analytical outputs. The several variables involved in the assembly of the biosensor were optimized by univariant mode. Under the best conditions, the biosensor showed a linear response from 0.010 fM to 10 pM, with a limit of detection (LOD) of 4.31 aM. The sensitivity was 0.3718 relative Ω per decade concentration in buffered saline solutions, and the standard deviation of the blank is 2.94 Ω. A linear response was also obtained when human serum samples were tested with miRNA 21-5p. Interference from similar miRNA and miss-match miRNA sequences was evaluated and good selectivity for miRNA 21-5p was observed. Overall, the device proposed is an alternative approach to gold substrates, which typically result in more sensitive systems and lower LODs, which compares favorably to current gold-based biosensors for the targeted miRNA. This design may be further extended to other nucleic acids.
      Citation: Chemosensors
      PubDate: 2022-05-19
      DOI: 10.3390/chemosensors10050189
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 190: How Surface-Enhanced Raman Spectroscopy
           Could Contribute to Medical Diagnoses

    • Authors: Aleksandra Szaniawska, Kinga Mazur, Dominika Kwarta, Edyta Pyrak, Andrzej Kudelski
      First page: 190
      Abstract: In the last decade, there has been a rapid increase in the number of surface-enhanced Raman scattering (SERS) spectroscopy applications in medical research. In this article we review some recent, and in our opinion, most interesting and promising applications of SERS spectroscopy in medical diagnostics, including those that permit multiplexing within the range important for clinical samples. We focus on the SERS-based detection of markers of various diseases (or those whose presence significantly increases the chance of developing a given disease), and on drug monitoring. We present selected examples of the SERS detection of particular fragments of DNA or RNA, or of bacteria, viruses, and disease-related proteins. We also describe a very promising and elegant ‘lab-on-chip’ approach used to carry out practical SERS measurements via a pad whose action is similar to that of a pregnancy test. The fundamental theoretical background of SERS spectroscopy, which should allow a better understanding of the operation of the sensors described, is also briefly outlined. We hope that this review article will be useful for researchers planning to enter this fascinating field.
      Citation: Chemosensors
      PubDate: 2022-05-19
      DOI: 10.3390/chemosensors10050190
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 191: Effects of Calcination Temperature on
           CO-Sensing Mechanism for NiO-Based Gas Sensors

    • Authors: Adelina Stanoiu, Corneliu Ghica, Catalina G. Mihalcea, Daniela Ghica, Simona Somacescu, Ovidiu G. Florea, Cristian E. Simion
      First page: 191
      Abstract: NiO-sensitive materials have been synthesized via the hydrothermal synthesis route and calcined in air at 400 °C and, alternatively, at 500 °C. Structural, morphological, and spectroscopic investigations were involved. As such, the XRD patterns showed a higher crystallinity degree for the NiO calcined at 500 °C. Such an aspect is in line with the XPS data indicating a lower surface hydroxylation relative to NiO calcined at 400 °C. An HRTEM microstructural investigation revealed that the two samples differ essentially at the morphological level, having different sizes of the crystalline nanoparticles, different density of the surface defects, and preferential faceting according to the main crystallographic planes. In order to identify their specific gas-sensing mechanism towards CO exposure under the in-field atmosphere, the simultaneous evaluation of the electrical resistance and contact potential difference was carried out. The results allowed the decoupling of the water physisorption from the chemisorption of the ambient oxygen species. Thus, the specific CO interaction mechanism induced by the calcination temperature of NiO has been highlighted.
      Citation: Chemosensors
      PubDate: 2022-05-19
      DOI: 10.3390/chemosensors10050191
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 192: Ultrafast and Multiplexed Bacteriophage
           Susceptibility Testing by Surface Plasmon Resonance and Phase Imaging of
           Immobilized Phage Microarrays

    • Authors: Larry O'Connell, Ondrej Mandula, Loïc Leroy, Axelle Aubert, Pierre R. Marcoux, Yoann Roupioz
      First page: 192
      Abstract: In the context of bacteriophage (phage) therapy, there is an urgent need for a method permitting multiplexed, parallel phage susceptibility testing (PST) prior to the formulation of personalized phage cocktails for administration to patients suffering from antimicrobial-resistant bacterial infections. Methods based on surface plasmon resonance imaging (SPRi) and phase imaging were demonstrated as candidates for very rapid (<2 h) PST in the broth phase. Biosensing layers composed of arrays of phages 44AHJD, P68, and gh-1 were covalently immobilized on the surface of an SPRi prism and exposed to liquid culture of either Pseudomonas putida or methicillin-resistant Staphylococcus aureus (i.e., either the phages’ host or non-host bacteria). Monitoring of reflectivity reveals susceptibility of the challenge bacteria to the immobilized phage strains. Investigation of phase imaging of lytic replication of gh-1 demonstrates PST at the single-cell scale, without requiring phage immobilization. SPRi sensorgrams show that on-target regions increase in reflectivity more slowly, stabilizing later and to a lower level compared to off-target regions. Phage susceptibility can be revealed in as little as 30 min in both the SPRi and phase imaging methods.
      Citation: Chemosensors
      PubDate: 2022-05-19
      DOI: 10.3390/chemosensors10050192
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 193: Acoustic Vibration Modes of
           Gold–Silver Core–Shell Nanoparticles

    • Authors: Tadele Orbula Otomalo, Lorenzo Di Mario, Cyrille Hamon, Doru Constantin, Francesco Toschi, Khanh-Van Do, Vincent Juvé, Pascal Ruello, Patrick O’Keeffe, Daniele Catone, Alessandra Paladini, Bruno Palpant
      First page: 193
      Abstract: Bimetallic Au/Ag core–shell cuboid nanoparticles (NPs) exhibit a complex plasmonic response dominated by a dipolar longitudinal mode and higher-order transverse modes in the near-UV, which may be exploited for a range of applications. In this paper, we take advantage of the strong signature of these modes in the NP ultrafast transient optical response, measured by pump-probe transient absorption (TA) spectroscopy, to explore the NP vibrational landscape. The fast Fourier transform analysis of the TA dynamics reveals specific vibration modes in the frequency range 15–150 GHz, further studied by numerical simulations based on the finite element method. While bare Au nanorods exhibit extensional and breathing modes, the bimetallic NPs undergo more complex motions, involving the displacement of facets, edges and corners. The amplitude and frequency of these modes are shown to depend on the Ag shell thickness, as the silver load modifies the NP aspect ratio and mass. Moreover, the contributions of the vibrational modes to the experimental TA spectra are shown to vary with the probe laser wavelength at which the signal is monitored. Using the combined simulations of the NP elastic and optical properties, we elucidate this influence by analyzing the effect of the mechanisms involved in the acousto-plasmonic coupling.
      Citation: Chemosensors
      PubDate: 2022-05-20
      DOI: 10.3390/chemosensors10050193
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 194: Advances in Electrochemical Techniques
           for the Detection and Analysis of Genetically Modified Organisms: An
           Analysis Based on Bibliometrics

    • Authors: Yuhong Zheng, Hassan Karimi-Maleh, Li Fu
      First page: 194
      Abstract: Since the first successful transgenic plants obtained in 1983, dozens of plants have been tested. On the one hand, genetically modified plants solve the problems of agricultural production. However, due to exogenous genes of transgenic plants, such as its seeds or pollen drift, diffusion between populations will likely lead to superweeds or affect the original traits. The detection technology of transgenic plants and their products have received considerable attention. Electrochemical sensing technology is a fast, low-cost, and portable analysis technology. This review interprets the application of electrochemical technology in the analysis and detection of transgenic products through bibliometrics. A total of 83 research articles were analyzed, spanning 2001 to 2021. We described the different stages in the development history of the subject and the contributions of countries and institutions to the topic. Although there were more annual publications in some years, there was no explosive growth in any period. The lack of breakthroughs in this technology is a significant factor in the lack of experts from other fields cross-examining the subject. Through keyword co-occurrence analysis, different research directions on this topic were discussed. The use of nanomaterials with excellent electrical conductivity allows for more sensitive detection of GM crops by electrochemical sensors. Furthermore, co-citation analysis was used to interpret the most popular reports on the topic. In the end, we predict the future development of this topic according to the analysis results.
      Citation: Chemosensors
      PubDate: 2022-05-21
      DOI: 10.3390/chemosensors10050194
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 195: Peptide-Conjugated Aggregation-Induced
           Emission Fluorogenic Probe for Glypican-3 Protein Detection and
           Hepatocellular Carcinoma Cells Imaging

    • Authors: Song Zhang, Jiangbo Jing, Lingchen Meng, Bin Xu, Xibo Ma, Wenjing Tian
      First page: 195
      Abstract: Hepatocellular carcinoma (HCC) is a malignant tumor with high morbidity and mortality on a global scale, and the development of accurate detection and imaging methods for HCC cells is urgently needed. Herein, by connecting peptide L5, which can specifically bind to the overexpressed Glypican-3 (GPC-3) protein of HCC cells with aggregation-induced emission (AIE) moiety ammonium cation-functionalized 9,10-distyrylanthracene (NDSA) via the “click” reaction, we synthesized a fluorescent probe NDSA-L5. In an aqueous solution, the probe shows weak emission, whereas, in the presence of the GPC-3 protein, bright fluorescence can be obtained since NDSA-L5 binds to the GPC-3 protein, leading to the restricted intramolecular movement of AIE-active NDSA-L5. The imaging and flow cytometry experiments demonstrate that the NDSA-L5 probe can rapidly accumulate in the subcutaneous HCC cells and liver tumor tissue and shows a potential application in early detection and surgical navigation for HCC cancer.
      Citation: Chemosensors
      PubDate: 2022-05-23
      DOI: 10.3390/chemosensors10050195
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 196: Adsorption of Aqueous Iodide on
           Hexadecyl Pyridinium-Modified Bentonite Investigated Using an
           Iodine–Starch Complex

    • Authors: Jun-Gyu Kim, Jun-Yeop Lee
      First page: 196
      Abstract: The sorption affinity of iodide on organo-bentonite, modified with hexadecyl pyridinium (HDPy), was investigated with the iodine–starch method coupled with UV/Vis absorption spectroscopy. The iodine–starch complex method was optimized in terms of the reaction time and sample compositions, based on the UV/Vis absorbance. The batch sorption experiment for iodide on organo-bentonites, modified using two different loading amounts of HDPy, was conducted to analyze the influence of equilibrium time, liquid-to-solid ratio, and temperature, on the iodide sorption affinity. The experimental results regarding the removal capacity were further employed to derive the distribution coefficients of iodide on the organo-bentonites. The novelty of this work lies in the first application of the iodine–starch method coupled with UV/Vis absorption spectroscopy for analyzing the sorption behavior of iodide on modified bentonites. It is expected that the iodide-starch method can be complementarily employed for future research, with respect to the quantification of iodide.
      Citation: Chemosensors
      PubDate: 2022-05-23
      DOI: 10.3390/chemosensors10050196
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 197: Optofluidic Micromachined Platform for
           Refractive Index Measurement

    • Authors: Zoran Djinović, Miloš Tomić, Agnes Kocsis
      First page: 197
      Abstract: We present a combination of micromachined optofluidic platforms equipped with a fiber-optic sensing configuration based on a three-path Mach–Zehnder interferometer (MZI) for simultaneous measurement of the refractive index of liquids and the autocalibration in dynamic regime. The sensing principle is based on the low-coherence interferometry, characterized by a generation of Gaussian enveloped interferograms, for which the position of its maximum depends on the optical path difference (OPD) between the sensing and reference arm of the MZI. When liquid flows through the central microchannel of the optofluidic platform it crosses the light beam between the two optical fibers in the sensing arm causing the OPD change. An algorithm has been applied for the calculation of the refractive index of liquids out of the raw interference signals. We obtained a very good agreement between the experimental results and literature data of refractive indices of subjected fluids. The accuracy of refractive index measurement is approximately 1%, predominantly determined by the accuracy of reading the position of the mechanical scanner. The proposed sensor is attractive for the label-free biological, biochemical, and chemical sensing owing autocalibration and high sensitivity yet consuming a very small sample volume of 1 µL. It is capable to measure the refractive index of various liquids and/or gases simultaneously in the process.
      Citation: Chemosensors
      PubDate: 2022-05-23
      DOI: 10.3390/chemosensors10050197
      Issue No: Vol. 10, No. 5 (2022)
  • Chemosensors, Vol. 10, Pages 143: Application of Multiharmonic QCM-D for
           Detection of Plasmin at Hydrophobic Surfaces Modified by β-Casein

    • Authors: Sandro Spagnolo, Eric S. Muckley, Ilia N. Ivanov, Tibor Hianik
      First page: 143
      Abstract: Plasmin protease plays an important role in many processes in living systems, including milk. Monitoring plasmin activity is important for control of the nutritional quality of milk and other dairy products. We designed a biosensor to detect the proteolytic activity of plasmin, using multiharmonic quartz crystal microbalance with dissipation (QCM-D). The β-casein immobilized on the hydrophobic surface of 1-dodecanethiol on the AT-cut quartz crystal was used to monitor plasmin activity. We demonstrated detection of plasmin in a concentration range of 0.1–20 nM, with the limit of detection about 0.13 ± 0.01 nM. The analysis of viscoelastic properties of the β-casein layer showed rapid changes of shear elasticity modulus, μ, and coefficient of viscosity, η, at plasmin sub-nanomolar concentrations, followed by modest changes at nanomolar concentrations, indicating multilayer architecture β-casein. A comparative analysis of viscoelastic properties of β-casein layers following plasmin and trypsin cleavage showed that the higher effect of trypsin was due to larger potential cleavage sites of β-casein.
      Citation: Chemosensors
      PubDate: 2022-04-11
      DOI: 10.3390/chemosensors10040143
      Issue No: Vol. 10, No. 4 (2022)
  • Chemosensors, Vol. 10, Pages 144: Estimation of Grain Size in Randomly
           Packed Granular Material Using Laser-Induced Breakdown Spectroscopy

    • Authors: Songting Li, Yaju Li, Xiaolong Li, Liangwen Chen, Dongbin Qian, Shaofeng Zhang, Xinwen Ma
      First page: 144
      Abstract: Grain size is one of the most important physical parameters for randomly packed granular (RPG) materials. Its estimation, especially in situ, plays a key role in many natural and industrial processes. Here, the application of laser-induced breakdown spectroscopy (LIBS) was investigated experimentally to estimate the grain size in RPG materials. The experiment was performed by taking sieved copper microspheres with discrete median diameters ranging from 53 to 357 μm as examples and by measuring the plasma emissions induced by 1064 nm laser pulses with a duration of 7 ns in an air environment. It was found that the plasma emission measurements were successful in estimating the grain median diameter via monitoring the variations in plasma temperature (electron density) at the range of median diameter below (above) a critical value. In addition, it was demonstrated that, when plasma temperature serves as an indicator of grain size, the intensity ratio between two spectral lines from different upper energy levels of the same emitting species can be used as an alternative indicator with higher sensitivity. The results show the potential of using LIBS for in situ estimation of grain size in RPG materials for the first time.
      Citation: Chemosensors
      PubDate: 2022-04-13
      DOI: 10.3390/chemosensors10040144
      Issue No: Vol. 10, No. 4 (2022)
  • Chemosensors, Vol. 10, Pages 145: Electrochemical Oxidation of Sodium
           Metabisulfite for Sensing Zinc Oxide Nanoparticles Deposited on Graphite

    • Authors: Kailai Wang, Edward P. C. Lai
      First page: 145
      Abstract: A novel concept was successfully evaluated for the electrochemical quantitative analysis of zinc oxide nanoparticles originally in aqueous suspension. An aliquot of the suspension was first placed on the working area of a graphite screen-printed electrode and the water was evaporated to form a dry deposit of ZnO nanoparticles. Deposition of ZnO nanoparticles on the electrode was confirmed by energy-dispersive X-ray spectroscopy. A probe solution containing KCl and sodium metabisulfite was added on top of the deposit for electrochemical analysis by cyclic voltammetry. The anodic peak current (Ipa) for metabisulfite, measured at +1.2 V vs. Ag/AgCl, afforded a lower detection limit of 3 µg and exhibited a linear dependence on the mass of deposited ZnO nanoparticles up to 15 μg. Further, the current increased nonlinearly until it reached a saturation level beyond 60 μg of ZnO nanoparticles. The diffusion coefficient of metabisulfite anions through the electrical double layer was determined to be 4.16 × 10−5 cm2/s. Apparently the surface reactivity of ZnO originated from the oxide anion rather than the superoxide anion or the hydroxyl radical. Enhancement of the metabisulfite oxidation peak current can be developed into a sensitive method for the quantitation of ZnO nanoparticles.
      Citation: Chemosensors
      PubDate: 2022-04-13
      DOI: 10.3390/chemosensors10040145
      Issue No: Vol. 10, No. 4 (2022)
  • Chemosensors, Vol. 10, Pages 146: Potentiometric Determination of
           Moxifloxacin by Solid-Contact ISEs in Wastewater Effluents

    • Authors: Sherif A. Abdel-Gawad, Hany H. Arab, Ahmed A. Albassam
      First page: 146
      Abstract: In recent years, the use of ion-selective membranes in the sensing and assessment of environmental contaminants has become a critical goal. Using sodium tetraphenylborate (TPB) and phosphotungstic acid (PTA) as ion-pairing agents, two sensitive and selective sensors were manufactured to evaluate the electrochemical response of moxifloxacin hydrochloride (MOX). The optimal electrochemical behavior was attained by fine-tuning all assay parameters. The manufactured membranes’ performance was optimal in a pH range from 1.0 to 5.0 with a linearity between 1 × 10−6 M and 1 × 10−2 M. The MOX–TPB and MOX–PTA membrane electrodes have Nernstian slopes of 59.2 ± 0.60 mV/decade and 58.4 ± 0.50 mV/decade, respectively. The proposed method was used to determine MOX in its pure form as well as real pharmaceutical wastewater effluents. The fabricated electrodes were effectively applied for the sensitive and selective determination of MOX in actual wastewater effluents without the need for any pre-treatment processes.
      Citation: Chemosensors
      PubDate: 2022-04-14
      DOI: 10.3390/chemosensors10040146
      Issue No: Vol. 10, No. 4 (2022)
  • Chemosensors, Vol. 10, Pages 147: UV-Activated NO2 Gas Sensing by
           Nanocrystalline ZnO: Mechanistic Insights from Mass Spectrometry

    • Authors: Artem Chizhov, Pavel Kutukov, Alexander Gulin, Artyom Astafiev, Marina Rumyantseva
      First page: 147
      Abstract: In this work, the photostimulated processes of O2 and NO2 molecules with the surface of ZnO under UV radiation were studied by in situ mass spectrometry in the temperature range of 30–100 ∘C. Nanocrystalline needle-like ZnO was synthesized by decomposition of basic zinc carbonate at 300 ∘C, and the surface concentration of oxygen vacancies in it were controlled by reductive post-annealing in an inert gas at 170 ∘C. The synthesized materials were characterized by XRD, SEM, low-temperature nitrogen adsorption (BET), XPS, Raman spectroscopy, and PL spectroscopy. Irradiation of samples with UV light causes the photoabsorption of both O2 and NO2. The photoadsorption properties of ZnO are compared with its defective structure and gas-sensitive properties to NO2. A model of the sensor response of ZnO to NO2 under UV photoactivation is proposed.
      Citation: Chemosensors
      PubDate: 2022-04-15
      DOI: 10.3390/chemosensors10040147
      Issue No: Vol. 10, No. 4 (2022)
  • Chemosensors, Vol. 10, Pages 148: Composite Electrodes Based on Carbon
           Materials Decorated with Hg Nanoparticles for the Simultaneous Detection
           of Cd(II), Pb(II) and Cu(II)

    • Authors: Laia L. Fernández, Julio Bastos-Arrieta, Cristina Palet, Mireia Baeza
      First page: 148
      Abstract: Monitoring water quality has become a goal to prevent issues related to human health and environmental conditions. In this sense, the concentration of metal ions in water sources is screened, as these are considered persistent contaminants. In this work, we describe the implementation of customized graphite electrodes decorated with two types of Hg nanoparticles (Hg-NPs), optimized toward the electrochemical detection of Cd, Pb and Cu. Here, we combine Hg, a well-known property to form alloys with other metals, with the nanoscale features of Hg-NPs, resulting in improved electrochemical sensors towards these analytes with a substantial reduction in the used Hg amount. Hg-NPs were synthesized using poly(diallyldimethylammonium) chloride (PDDA) in a combined role as a reducing and stabilizing agent, and then appropriately characterized by means of Transmission Electron Microscopy (TEM) and Zeta Potential. The surface of composite electrodes with optimized graphite content was modified by the drop-casting of the prepared Hg-NPs. The obtained nanocomposite electrodes were morphologically characterized by Scanning Electron Microscopy (SEM), and electrochemically by Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The results show that the Hg-NP-modified electrodes present better responses towards Cd(II), Pb(II) and Cu(II) detection in comparison with the bare graphite electrode. Analytical performance of sensors was evaluated by square-wave anodic stripping voltammetry (SWASV), obtaining a linear range of 0.005–0.5 mg·L−1 for Cd2+, of 0.028–0.37 mg·L−1 for Pb2+ and of 0.057–1.1 mg·L−1 for Cu2+. Real samples were analyzed using SWASV, showing good agreement with the recovery values of inductively coupled plasma–mass spectrometry (ICP-MS) measurements.
      Citation: Chemosensors
      PubDate: 2022-04-15
      DOI: 10.3390/chemosensors10040148
      Issue No: Vol. 10, No. 4 (2022)
  • Chemosensors, Vol. 10, Pages 149: Real-Time Fluorescence Imaging of
           His-Tag-Driven Conjugation of mCherry Proteins to Silver Nanowires

    • Authors: Martyna Jankowska, Karolina Sulowska, Kamil Wiwatowski, Joanna Niedziółka-Jönsson, Sebastian Mackowski
      First page: 149
      Abstract: In this work, we aimed to apply fluorescence microscopy to image protein conjugation to Ni-NTA modified silver nanowires in real time via the His-tag attachment. First, a set of experiments was designed and performed for the mixtures of proteins and silver nanowires in order to demonstrate plasmon enhancement of mCherry protein fluorescence as well as the ability to image fluorescence of single molecules. The results indicated strong enhancement of single-protein fluorescence emission upon coupling with silver nanowires. This conclusion was supported by a decrease in the fluorescence decay time of mCherry proteins. Real-time imaging was carried out for a structure created by dropping protein solution onto a glass substrate with functionalized silver nanowires. We observed specific attachment of mCherry proteins to the nanowires, with the recognition time being much longer than in the case of streptavidin–biotin conjugation. This result indicated that it is possible to design a universal and efficient real-time sensing platform with plasmonically active functionalized silver nanowires.
      Citation: Chemosensors
      PubDate: 2022-04-18
      DOI: 10.3390/chemosensors10040149
      Issue No: Vol. 10, No. 4 (2022)
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