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  Subjects -> CHEMISTRY (Total: 922 journals)
    - ANALYTICAL CHEMISTRY (56 journals)
    - CHEMISTRY (656 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (28 journals)
    - INORGANIC CHEMISTRY (43 journals)
    - ORGANIC CHEMISTRY (47 journals)
    - PHYSICAL CHEMISTRY (71 journals)

CHEMISTRY (656 journals)            First | 1 2 3 4 | Last

Showing 401 - 600 of 735 Journals sorted alphabetically
Journal of Porphyrins and Phthalocyanines     Hybrid Journal   (Followers: 2)
Journal of Pure and Applied Chemistry Research     Open Access   (Followers: 3)
Journal of Raman Spectroscopy     Hybrid Journal   (Followers: 17)
Journal of Research Updates in Polymer Science     Hybrid Journal   (Followers: 3)
Journal of Saudi Chemical Society     Open Access  
Journal of Solid State Chemistry     Hybrid Journal   (Followers: 14)
Journal of Solution Chemistry     Hybrid Journal   (Followers: 2)
Journal of Structural Chemistry     Hybrid Journal   (Followers: 1)
Journal of Sulfur Chemistry     Hybrid Journal   (Followers: 3)
Journal of Supercritical Fluids     Hybrid Journal   (Followers: 4)
Journal of Superhard Materials     Hybrid Journal   (Followers: 1)
Journal of Surface Science and Technology     Hybrid Journal  
Journal of Surfactants and Detergents     Hybrid Journal   (Followers: 3)
Journal of Taibah University for Science     Open Access   (Followers: 1)
Journal of the American Chemical Society     Hybrid Journal   (Followers: 373)
Journal of the American Society for Mass Spectrometry     Hybrid Journal   (Followers: 32)
Journal of the American Society of Brewing Chemists     Full-text available via subscription   (Followers: 3)
Journal of the Bangladesh Chemical Society     Open Access  
Journal of the Chilean Chemical Society     Open Access   (Followers: 2)
Journal of the Iranian Chemical Society     Hybrid Journal  
Journal of the Korean Society for Applied Biological Chemistry     Hybrid Journal   (Followers: 1)
Journal of the Mexican Chemical Society     Open Access   (Followers: 2)
Journal of the Serbian Chemical Society     Open Access  
Journal of the Turkish Chemical Society, Section A : Chemistry     Open Access  
Journal of Theoretical and Computational Chemistry     Hybrid Journal   (Followers: 10)
JPC - Journal of Planar Chromatography - Modern TLC     Full-text available via subscription   (Followers: 2)
Jurnal Inovasi Pendidikan Kimia     Open Access   (Followers: 5)
Jurnal Katalisator     Open Access  
Jurnal Kimia (Journal of Chemistry)     Open Access  
Jurnal Kimia Riset     Open Access  
Jurnal Penelitian Sains (JPS)     Open Access  
Karadeniz Chemical Science and Technology     Open Access  
Karbala International Journal of Modern Science     Open Access   (Followers: 3)
Kinetics and Catalysis     Hybrid Journal   (Followers: 5)
Konfigurasi : Jurnal Pendidikan Kimia dan Terapan     Open Access  
Korea-Australia Rheology Journal     Hybrid Journal  
Langmuir     Hybrid Journal   (Followers: 63)
Latvian Journal of Chemistry     Open Access   (Followers: 1)
Lebensmittelchemie     Hybrid Journal   (Followers: 1)
Lipid Insights     Open Access  
Luminescence     Hybrid Journal   (Followers: 5)
Macromolecular Materials & Engineering     Hybrid Journal   (Followers: 5)
Macromolecular Rapid Communications     Hybrid Journal   (Followers: 10)
Macromolecular Research     Hybrid Journal   (Followers: 2)
Macromolecular Symposia     Hybrid Journal   (Followers: 3)
Macromolecular Theory and Simulations     Hybrid Journal   (Followers: 2)
Macromolecules     Hybrid Journal   (Followers: 50)
Maghrebian Journal of Pure and Applied Science     Full-text available via subscription  
Magnetic Resonance in Chemistry     Hybrid Journal   (Followers: 10)
Magnetochemistry     Open Access  
Marine Chemistry     Hybrid Journal   (Followers: 7)
Marine Drugs     Open Access   (Followers: 4)
MATEC Web of Conferences     Open Access   (Followers: 5)
Materials Characterization     Hybrid Journal   (Followers: 34)
Materials Chemistry Frontiers     Full-text available via subscription  
Materials Horizons     Full-text available via subscription   (Followers: 3)
Materials Research Bulletin     Hybrid Journal   (Followers: 28)
Materials Science Monographs     Full-text available via subscription   (Followers: 3)
Materials Science-Poland     Open Access   (Followers: 1)
Materials Sciences and Applications     Open Access   (Followers: 3)
MedChemComm     Full-text available via subscription   (Followers: 7)
Medicinal Chemistry Research     Hybrid Journal   (Followers: 13)
Mediterranean Journal of Chemistry     Open Access  
Metallography, Microstructure, and Analysis     Hybrid Journal   (Followers: 2)
Metallomics     Full-text available via subscription  
Micro and Nano Systems Letters     Open Access   (Followers: 6)
Microchimica Acta     Hybrid Journal   (Followers: 2)
Microporous and Mesoporous Materials     Hybrid Journal   (Followers: 10)
Modern Chemistry & Applications     Open Access   (Followers: 1)
Modern Research in Catalysis     Open Access   (Followers: 1)
Molbank     Open Access   (Followers: 1)
Molecular Astrophysics     Full-text available via subscription  
Molecules     Open Access   (Followers: 7)
Molecules and Cells     Hybrid Journal   (Followers: 1)
Monatshefte für Chemie - Chemical Monthly     Hybrid Journal   (Followers: 4)
Mongolian Journal of Chemistry     Open Access  
Moroccan Journal of Chemistry     Open Access  
Moroccan Journal of Heterocyclic Chemistry     Open Access  
Moscow University Chemistry Bulletin     Hybrid Journal   (Followers: 1)
MRS Bulletin     Full-text available via subscription   (Followers: 4)
MRS Online Proceedings     Full-text available via subscription   (Followers: 1)
Nachrichten aus der Chemie     Hybrid Journal   (Followers: 17)
Nano Convergence     Open Access   (Followers: 1)
Nano Reviews & Experiments     Open Access   (Followers: 14)
Nanochemistry Research     Open Access  
Nanocontainers     Open Access   (Followers: 1)
Nanomaterials and the Environment     Open Access   (Followers: 1)
Nanoscale     Full-text available via subscription   (Followers: 20)
Nanoscale Advances     Open Access   (Followers: 1)
Nanoscale Research Letters     Open Access   (Followers: 9)
Nanoscience and Nanotechnology Letters     Full-text available via subscription   (Followers: 22)
Nanospectroscopy     Open Access   (Followers: 2)
Natural Product Reports     Full-text available via subscription   (Followers: 11)
Natural Products Chemistry & Research     Open Access   (Followers: 1)
Natural Products Journal     Hybrid Journal   (Followers: 1)
Natural Science     Open Access   (Followers: 9)
Natural Volatiles & Essential Oils     Open Access  
Nature Chemistry     Full-text available via subscription   (Followers: 95)
Nature Protocols     Full-text available via subscription   (Followers: 70)
Nature Reviews Chemistry     Hybrid Journal   (Followers: 7)
New Journal of Chemistry     Full-text available via subscription   (Followers: 19)
Nitric Oxide     Hybrid Journal  
Nitrogen     Open Access  
Nova Biotechnologica et Chimica     Open Access  
Nukleonika     Open Access   (Followers: 2)
Open Chemistry     Open Access   (Followers: 6)
Open Chemistry Journal     Open Access  
Open Conference Proceedings Journal     Open Access  
Open Journal of Composite Materials     Open Access   (Followers: 18)
Open Journal of Inorganic Non-metallic Materials     Open Access   (Followers: 4)
Open Journal of Medicinal Chemistry     Open Access   (Followers: 5)
Open Journal of Polymer Chemistry     Open Access   (Followers: 12)
Open Journal of Synthesis Theory and Applications     Open Access  
Open Medicinal Chemistry Journal     Open Access  
Orbital - The Electronic Journal of Chemistry     Open Access   (Followers: 3)
Organic & Biomolecular Chemistry     Full-text available via subscription   (Followers: 75)
Organometallics     Hybrid Journal   (Followers: 22)
Organosulfur Chemistry     Full-text available via subscription  
Oxidation of Metals     Hybrid Journal   (Followers: 18)
Peptidomics     Open Access  
Pharmaceuticals     Open Access   (Followers: 6)
Pharmaceutics     Open Access   (Followers: 4)
Phosphorus, Sulfur, and Silicon and the Related Elements     Hybrid Journal   (Followers: 2)
Photochemistry and Photobiology     Hybrid Journal   (Followers: 4)
Physical Sciences Reviews     Hybrid Journal   (Followers: 1)
Physics and Materials Chemistry     Open Access   (Followers: 2)
Phytochemistry     Hybrid Journal   (Followers: 6)
Phytochemistry Letters     Full-text available via subscription   (Followers: 4)
Plasma     Open Access   (Followers: 2)
Plasma Chemistry and Plasma Processing     Hybrid Journal   (Followers: 6)
Polímeros : Ciência e Tecnologia     Open Access  
Polycyclic Aromatic Compounds     Hybrid Journal  
Polyhedron     Hybrid Journal   (Followers: 4)
Polymer Chemistry     Full-text available via subscription   (Followers: 25)
Polymer Degradation and Stability     Hybrid Journal   (Followers: 26)
Polymer Engineering & Science     Hybrid Journal   (Followers: 16)
Polymer Reviews     Hybrid Journal   (Followers: 35)
Polymer Science Series D     Hybrid Journal   (Followers: 4)
Polymer Testing     Hybrid Journal   (Followers: 109)
Polymer-Plastics Technology and Engineering     Hybrid Journal   (Followers: 5)
Polymers     Open Access   (Followers: 18)
Procedia Chemistry     Open Access  
Proceedings in Radiochemistry. A Supplement to Radiochimica Acta     Open Access   (Followers: 1)
Proceedings of the Combustion Institute     Full-text available via subscription   (Followers: 8)
Processes     Open Access  
Progress in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 1)
Progress in Lipid Research     Hybrid Journal   (Followers: 3)
Progress in Organic Coatings     Hybrid Journal   (Followers: 9)
Progress in Polymer Science     Full-text available via subscription   (Followers: 37)
Progress in Reaction Kinetics and Mechanism     Full-text available via subscription   (Followers: 2)
Progress in Solid State Chemistry     Full-text available via subscription   (Followers: 3)
Progress in Surface Science     Full-text available via subscription   (Followers: 4)
Protein Science     Hybrid Journal   (Followers: 46)
Pure and Applied Chemistry     Hybrid Journal   (Followers: 8)
Química Nova     Open Access  
Quimica Viva     Open Access  
Radiochemistry     Hybrid Journal   (Followers: 2)
Rapid Communications in Mass Spectrometry     Hybrid Journal   (Followers: 32)
Reaction Chemistry & Engineering     Hybrid Journal  
Reaction Kinetics, Mechanisms and Catalysis     Hybrid Journal   (Followers: 2)
Recent Advances in Phytochemistry     Full-text available via subscription   (Followers: 3)
Recyclable Catalysis     Open Access   (Followers: 2)
Reports in Theoretical Chemistry     Open Access  
Research and Reports in Medicinal Chemistry     Open Access   (Followers: 3)
Research Journal of Phytochemistry     Open Access   (Followers: 3)
Review Journal of Chemistry     Hybrid Journal  
Reviews in Chemical Engineering     Hybrid Journal   (Followers: 6)
Reviews in Mineralogy and Geochemistry     Hybrid Journal   (Followers: 4)
Reviews of Adhesion and Adhesives     Full-text available via subscription  
Revista CENIC. Ciencias Quimicas     Open Access   (Followers: 2)
Revista Ciências Exatas e Naturais : RECEN     Open Access  
Revista Colombiana de Química     Open Access   (Followers: 1)
Revista Cubana de Química     Open Access  
Revista de Ciencia y Tecnología     Open Access  
Revista de Ciencias     Open Access  
Revista de la Societat Catalana de Química     Open Access  
Revista Debates em Ensino de Química     Open Access  
Revista ION     Open Access  
Revista Química : ciência, tecnologia e sociedade     Open Access  
RHAZES : Green and Applied Chemistry     Open Access  
RSC Advances     Open Access   (Followers: 33)
Rubber Chemistry and Technology     Full-text available via subscription   (Followers: 2)
Russian Chemical Reviews     Full-text available via subscription   (Followers: 4)
Russian Journal of Bioorganic Chemistry     Hybrid Journal   (Followers: 2)
Russian Journal of Coordination Chemistry     Hybrid Journal   (Followers: 1)
Russian Journal of General Chemistry     Hybrid Journal   (Followers: 1)
Russian Journal of Inorganic Chemistry     Hybrid Journal  
Sainstek : Jurnal Sains dan Teknologi     Open Access  
Science China Chemistry     Hybrid Journal   (Followers: 2)
Sciences & Technologie A : sciences exactes     Open Access  
Scientific Journal of Frontier Chemical Development     Open Access   (Followers: 1)
Scientific Reports     Open Access   (Followers: 73)
Sensors and Actuators B: Chemical     Hybrid Journal   (Followers: 17)
Separation & Purification Reviews     Hybrid Journal   (Followers: 8)
Separation Science and Technology     Hybrid Journal   (Followers: 14)
Separations     Open Access   (Followers: 6)
Silicon Chemistry     Hybrid Journal   (Followers: 2)
Smart Materials Research     Open Access   (Followers: 7)
Soft     Open Access  
Soft Nanoscience Letters     Open Access   (Followers: 2)

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Similar Journals
Journal Cover
Sensors and Actuators B: Chemical
Journal Prestige (SJR): 1.406
Citation Impact (citeScore): 6
Number of Followers: 17  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0925-4005
Published by Elsevier Homepage  [3185 journals]
  • Direct growth of NiO films on Al2O3 ceramics by electrochemical deposition
           and its excellent H2S sensing properties
    • Abstract: Publication date: 1 October 2019Source: Sensors and Actuators B: Chemical, Volume 296Author(s): Yueying Liu, Fengmin Liu, Jihao Bai, Tianyu Liu, Ziyang Yu, Meng Dai, Linsheng Zhou, Hongtao Wang, Yiqun Zhang, Hui Suo, Geyu Lu NiO thin films were grown directly on the Al2O3 substrates by electrochemical deposition. The H2S gas sensing properties of the thin films were enhanced by Cu doping. The X-ray diffraction revealed the as-prepared films were NiO crystalline phase. The scanning electron microscope showed the film has 1.87 μm thickness and pores of different sizes, more porous has a higher exposed surface, which can provide more active sites for reaction with the gas. The atomic force microscopy characterization further confirmed the high roughness and porosity of the thin films. Gas sensitivity test displayed that the thin film sensor based on Ni: Cu molar ratio of 9:1 exhibited the highest response and good selectivity to H2S at 140 °C. Furthermore, the NiO doped by Cu thin film gas sensor also possesses good stability and low detection limit of 100 ppb. The extraordinary gas sensing properties can be attributed to the lamellar structures with the porous channel and substitution doping of Cu.
       
  • Electrospun SnO2/PPy nanocomposite for ultra-low ammonia concentration
           detection at room temperature
    • Abstract: Publication date: 1 October 2019Source: Sensors and Actuators B: Chemical, Volume 296Author(s): Ajay Beniwal, Sunny Ultra-sensitive, highly selective, fast responsive and extreme low-ppb ammonia (NH3) sensor working at room temperature (RT) has been developed using SnO2/polypyrrole nanocomposite. Porous SnO2 nanofibers having diameter in range ˜70–150 nm were deposited using electrospinning technique, followed by vapor phase polymerization of pyrrole to develop SnO2/polypyrrole (PPy) composite. The mean crystallite size of the composite was calculated using X-ray diffractometer (XRD) and found to be ˜ 13 nm, which is comparable with the 2LD (Debye length) of SnO2. Fourier transform infrared spectroscopy (FTIR) results were used for structural analysis and to confirm the SnO2/polypyrrole composite formation. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) results were used to analyze the surface morphology and chemical composition. Under exposure to 100 ppb of ammonia at RT, the sensor showed ˜57% response with fast response (18 s) and recovery times (30 s). The response of the sensor was analyzed for ammonia concentration ranging from 100 ppb to 1000 ppm and utterly high % response was observed i.e. 3365% for 1000 ppm at RT, with appreciable response and recovery times. The selectivity of the sensor was analyzed against other competing analytes viz. monoethanolamine (MEA), diethanol amine (DEA), triethanolamine (TEA), ethanol, methanol, 2-propanol and acetone along with target analyte ammonia.
       
  • A multichannel single-well sensor array for rapid and visual
           discrimination of catecholamine neurotransmitters
    • Abstract: Publication date: 1 October 2019Source: Sensors and Actuators B: Chemical, Volume 296Author(s): Samira Abbasi-Moayed, M. Reza Hormozi-Nezhad, Malik Maaza In this study, for rapid identification and discrimination of catecholamine neurotransmitters in the presence of ascorbic acid (AA), a tricolor fluorescence probe has been constructed by integrating three recognition elements including blue carbon dots (bCDs), green CdTe quantum dots (gQDs) and red CdTe quantum dots (rQDs) into a single well. The proposed array exhibited ternary fluorescence emissions at 450, 520 and 630 nm with an overall luminescent pink emission under a single wavelength excitation (365 nm). In order to produce distinct response patterns from a single fluorimetric test, the spectral changes and the corresponding color variations of the multichannel fluorescence probe were monitored. Finally, analyzing the response profiles with pattern recognition methods allowed us to identify and discriminate catecholamine neurotransmitters and to also distinguish them from AA which is known as a serious interference in urine samples. Altogether, the developed sensor array can be considered as a rapid and visual tool for diagnostic and therapeutic applications in the near future.Graphical abstractGraphical abstract for this article
       
  • Highly sensitive biosensor based on graphene–poly (3-aminobenzoic acid)
           modified electrodes and porous-hollowed-silver-gold nanoparticle labelling
           for prostate cancer detection
    • Abstract: Publication date: 1 October 2019Source: Sensors and Actuators B: Chemical, Volume 296Author(s): Chammari Pothipor, Natta Wiriyakun, Thitirat Putnin, Aroonsri Ngamaroonchote, Jaroon Jakmunee, Kontad Ounnunkad, Rawiwan Laocharoensuk, Noppadol Aroonyadet Recent studies show that electrochemical biosensors offer simple, robust and low-cost solution for point-of-care applications. To meet rigorous requirements of early disease diagnosis and other medical applications, nanomaterials have been investigated to increase sensitivity and selectivity of electrochemical sensors. Herein, we successfully developed graphene-poly(3-aminobenzoic acid) (GP-P3ABA) nanomaterial-conductive polymer composite for electrode modification and metal ion loaded porous-hollowed-silver-gold core-shell nanoparticles (PHSGNPs) labelling for signal amplification. With GP-P3ABA modified electrodes, the sensing response is about 16 times higher than ones without nanocomposite due to reduction in electrode impedance and more probe binding sites from P3ABA terminals, respectively. Incubation time and volume of CuCl2 solution were optimized for maximum absorbed Cu ions on the nanoparticles and electrochemical current. It is found that our investigated system has about 3 folds higher electrochemical current from PHSGNPs than from gold nanoparticles (AuNPs) due to larger surface area of PHSGNPs to anchor Cu ions. With combination of GP-P3ABA electrode modification and PHSGNP labelling, sensing performance is improved by 120 folds over AuNP labelling and the limit of detection (LOD) reaches 0.13 pg/mL or 4 orders of magnitude better than the clinically relevant level in human serum. With good sensitivity and specificity, these inexpensive sensor strips could be applied for early diagnosis of prostate cancer and other medical applications in the future.Graphical abstractGraphical abstract for this article
       
  • Determination of lactate levels in biological fluids using a disposable
           ion-selective potentiometric sensor based on polypyrrole films
    • Abstract: Publication date: 1 October 2019Source: Sensors and Actuators B: Chemical, Volume 296Author(s): Priscilla Mengarda, Fernando A.L. Dias, João V.C. Peixoto, Raul Osiecki, Márcio F. Bergamini, Luiz H. Marcolino-Junior In this work, we present a lactate-selective potentiometric sensor as simple, low cost and non-enzymatic alternative for application in three different biological fluids. The selectivity of proposed sensor is based on a polypyrrole matrix doped with lactate ions in its structure which occurs during galvanostatic polymerization step. After optimization, the device showed a wide linear range between 0.1 and 10.0 mmol L−1 with a slope of 23.7 ± 0.2 mV dec−1, a limit of detection (LOD) of 81 μmol L−1, and excellent repeatability (RSD = 2.1%) and reproducibility (RSD = 2.7%). Tests to evaluate the influence of possible interferences were performed, in which the sensor showed good selectivity to lactate ions. The sensor was applied to evaluate lactate levels in human tear samples and a linear correlation with lactate levels in blood samples (R2 = 0.977) was found. In order to assess lactate levels before and after intense physical activity, blood samples from rats and human sweat samples were analyzed. For both fluids the potential variation was obtained, and in comparison to the lactate analysis in blood by portable device, the human sweat response was confirmed by the proposed method. Thus, the developed sensor demonstrated a viable and efficient electroanalytical tool to the current commercial devices, especially to support in physical performance evaluations.
       
  • A 3D printed screw-and-nut based droplet generator with facile and precise
           droplet size controllability
    • Abstract: Publication date: 1 October 2019Source: Sensors and Actuators B: Chemical, Volume 296Author(s): Hau Van Nguyen, Huynh Quoc Nguyen, Van Dan Nguyen, Tae Seok Seo Herein, we present the fabrication of a novel vertical T-junction based droplet generator using a desktop 3D printer and the production of a variety of size of polymer particles by tuning the vertical T-junction gap height (hg) with ease. The droplet generator device consists of two main components: an internal thread nut with a vertical T-junction droplet generator unit, and a screw with an external thread for adjusting hg. The two components were fabricated by a 3D printer and assembled simply by a bolt-and-nut combination. The clockwise or counter-clockwise rotation of the screw is converted into the downward and upward linear motion of the screw, adjusting the hg value. The hg value can be tuned precisely from 0 to 750 μm by designing 75 control teeth on the top of the screw. The size of the produced droplets is proportional to the hg value. The size range of the droplets was 39–1404 μm, when hg changed from 20 to 200 μm. We synthesized poly(ethylene glycol) diacrylate (PEGDA) particles using the droplet as a reactor, and accordingly the PEGDA particle size could be controlled. Our proposed 3D printed droplet generator is rapid, simple and cost-effective to be fabricated without need of lithographic processes.Graphical abstractGraphical abstract for this article
       
  • Developing O/O (oil-in-oil) droplet generators on a chip by using ECF
           (electro-conjugate fluid) micropumps
    • Abstract: Publication date: 1 October 2019Source: Sensors and Actuators B: Chemical, Volume 296Author(s): Zebing Mao, Kazuhiro Yoshida, Joon-wan Kim The previously reported O/O (Oil-in-oil) droplet generators are based on the usage of microfluidics and membrane emulsification techniques powered by external bulky syringe pumps. This configuration brings problems such as dead volume, air contamination, and difficult integration with other microfluidic components. The paper proposes an O/O droplet generator on a chip based on the integration of the MEMS (Micro Electro Mechanical Systems) technique and an electro-hydrodynamic method. In the generator, two ECF micropumps are used to pump the continuous and dispersed phase liquids, separately. By integrating our ECF micropumps, the droplet-generator-on-a-chip is easily fabricated, mainly using photolithography-based molding and electroforming. Among over 50 types of ECFs, we select HFE-7200 as a dispersed fluid and dibutyl decanedioate (DBD) with its surfactant of Span 80 at a concentration of 3% as a continuous fluid. We investigate the independent flow rates of two ECF micropumps, confirm the flow pattern diagrams of two-phase fluids, and examine the generated droplet diameter, the production rate, and the polydispersity index of O/O droplets. The results demonstrate that our device can generate O/O droplets with a low polydispersity index simply by adjusting the voltages applied to the ECF micropumps.
       
  • Mixed potential type acetone sensor based on Ce0.8Gd0.2O1.95 and
           Bi0.5La0.5FeO3 sensing electrode used for the detection of diabetic
           ketosis
    • Abstract: Publication date: 1 October 2019Source: Sensors and Actuators B: Chemical, Volume 296Author(s): Tong Liu, Luyao Li, Xinyu Yang, Xishuang Liang, Fengmin Liu, Fangmeng Liu, Chuan Zhang, Peng Sun, Xu Yan, Geyu Lu Non-invasive monitoring performed by breath analysis to achieve early diagnosis of diabetic ketosis have attracted widespread attention. In this study, mixed potential type acetone sensors based on Ce0.8Gd0.2O1.95 solid electrolyte and Bi1−xLaxFeO3 (x = 0.1, 0.3, 0.5, 0.7, 0.9) sensing electrode (SE) were fabricated successfully and used for the diagnosis of diabetic ketosis through analyzing the concentration of acetone in expiration. The sensor attached with Bi0.5La0.5FeO3-SE presented the highest sensitivity towards acetone among other sensors fabricated in this work, which could detect 1 ppm acetone with the response value of −3 mV. Meanwhile, this sensor showed a relatively high sensitivity of −17.5 mV/decade towards 1–5 ppm acetone at 580 °C. The sensor also displayed excellent repeatability, good selectivity, humidity stability and acceptable long-term stability during 30 days continuously working at 580 °C. Based on the sensing performance of this sensor, the exhalation of diabetics were measured, and results indicated that the sensor used Bi0.5La0.5FeO3-SE exhibited stable and reliable characteristics to the breath tests of diabetics. In addition, a positive correlation relationship between acetone concentration in the exhalation of ketosis patients and the blood ketone level were obtained, and this relationship was consistent with reports from other literatures. Hence, in terms of breath detection, this sensor has the potential to detect diabetic ketosis.
       
  • Detection and determination of harmful gases in confined spaces for the
           Internet of Things based on cataluminescence sensor
    • Abstract: Publication date: 1 October 2019Source: Sensors and Actuators B: Chemical, Volume 296Author(s): Guolong Shi, Yigang He, Yongxing Zhang, Baiqiang Yin, Farhan Ali Gaseous cataluminescence (CTL) sensor instrument was developed for detecting and measuring pernicious gases such as ethyl ether, acetone, n-hexane, chloroform by using aluminum/iron oxides composites. The materials synthesis, apparatus and software, optimal conditions (flow rate, wavelength, temperature and concentration), selectivity and stability were thoroughly studied. The results indicated the CTL sensor instrument could response to ethyl ether under 180 °C, which was lower than most of the reported CTL reaction temperatures. In addition, the results showed that the linear detection range was wide, ranging from 10 ppm to 5800 ppm (R = 0.9978, n = 7), and the detection limit was also low (4.3 ppm). Moreover, for ethyl ether detection, the CTL sensor showed the response time of 4 s and recovery time of 8 s, which was relatively short. The pattern recognition methods included PCA, KPCA were selected for evaluating the recognition performance of this CTL sensor, results showed the analytes could be classified clearly. The low reaction temperature, excellent sensitivity, selectivity, stability and recognition performance indicated this CTL sensor was ideal for gas contaminants detection in confined spaces for the Internet of Things.
       
  • Controllable synthesis of crescent-shaped porous NiO nanoplates for
           conductometric ethanol gas sensors
    • Abstract: Publication date: 1 October 2019Source: Sensors and Actuators B: Chemical, Volume 296Author(s): Chen Su, Lu Zhang, Yutong Han, Cong Ren, Xinwei Chen, Jun Hu, Min Zeng, Nantao Hu, Yanjie Su, Zhihua Zhou, Zhi Yang NiO has been widely used as building blocks for gas sensing because of its excellent physicochemical properties. However, the high working temperature of most NiO-based sensors (
       
  • Classification of hybrid seeds using near-infrared hyperspectral imaging
           technology combined with deep learning
    • Abstract: Publication date: 1 October 2019Source: Sensors and Actuators B: Chemical, Volume 296Author(s): Pengcheng Nie, Jinnuo Zhang, Xuping Feng, Chenliang Yu, Yong He The rapid and efficient selection of eligible hybrid progeny is an important step in cross breeding. However, selecting hybrid offspring that meets specific requirements can be time consuming and expensive. Here, near-infrared hyperspectral imaging technology combined with deep learning was applied to classifying hybrid seeds. The hyperspectral images in the range of 975–1648 nm of a total of 6136 hybrid okra seeds and 4128 hybrid loofah seeds, which both contained six varieties, were collected. A partial least squares discriminant analysis, support vector machine and deep convolutional neural network (DCNN) were used to establish discriminant analysis models, and their performances were compared among the different hybrid seed varieties. The discriminant analysis model based on the DCNN was the most stable and had the highest classification accuracy, greater than 95%. The values of features in the last layer of the DCNN were visualized using t-distribution stochastic neighbor embedding. The discriminant analysis model based on the DCNN had the advantages of reducing the labor burden and time required in cross breeding-based progeny selection, which will accelerate the progress of related research.
       
  • Pd@CeO2-SnO2 nanocomposite, a highly selective and sensitive hydrogen
           peroxide electrochemical sensor
    • Abstract: Publication date: Available online 13 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Ali A. Ensafi, A. Mahmoodi, B. Rezaei In this study, Pd@CeO2-SnO2 nanocomposite was synthesized and various methods such as FE-SEM, TEM, EDS, FT-IR, and XRD were used to characterize the nanocomposite. The electrocatalytic behaviour of the nanocomposite was studied for the reduction of H2O2. After optimization of various experimental parameters including pH, scan rate, rotation rate and potential, the calibration curve was plotted for the reduction reaction of the H2O2 at pHs 7.0 and 8.0. At pH 7.0, the linear range and detection limit were obtained as 0.15-1920 μM and 44 nM, respectively. Also, at pH 8.0, the linear range and detection limit were obtained as 0.12-2170 μM and 36 nM, respectively. In addition, the detection sensitivity of the sensor for the determination of H2O2 at pH 7.0 and 8.0 was 472.40 and 533.07 μA.mM-1. cm-2, respectively. Further, the sensor response to the H2O2 was studied in the presence of various types of potential interference species. The results confirmed the high selectivity of the designed sensor for the reduction of H2O2. Finally, the accuracy and applicability of the H2O2 electrochemical sensor in three different milk samples were evaluated with satisfactory results.Graphical abstractGraphical abstract for this article
       
  • Novel electrochemical genosensor for Zika virus based on a
           poly-(3-amino-4-hydroxybenzoic acid)-modified pencil carbon graphite
           electrode
    • Abstract: Publication date: Available online 12 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Rafael da Fonseca Alves, Diego Leoni Franco, Marli Tenório Cordeiro, Ernesto Marques de Oliveira, Rosa Amalia Fireman Dutra, Maria Del Pilar Taboada Sotomayor The Zika virus has recently emerged as a major worldwide threat because it induces microencephaly and other brain damage in babies born to infected mothers. Epidemiological monitoring of infection has been hampered by the lack of reliable tests capable of distinguishing between Zika and other Flavivirus infections, especially the dengue virus. The present work describes the electrochemical modification of pencil carbon graphite electrodes with a material derived from 3-amino-4-hydroxybenzoic acid. Solutions were prepared in acid medium and the material formed showed insulating behavior. Optical and electrical data suggested that carboxyl groups did not participate in the reaction mechanism. FT-IR spectra indicated that these groups were retained, enabling the proposal of a mechanism based on the data obtained. The material formed was used for immobilization of the ssDNAzv aminated oligonucleotide. Detection of the hybridization was based on the Δip resulting from the higher electrostatic repulsion of [Fe(CN)6]3-, caused by the increase of phosphates by addition of the complementary target sequence. The system showed a good linear correlation coefficient (r² = 0.997), with satisfactory selectivity and reproducibility, a low limit of detection (25.4 pM), and precision (RSD) of 3.1%, using real samples of human serum enriched with total extract of Zika virus RNA. Tests of the system using the total RNA extracted from dengue virus types 2 and 3 cultures showed little difference in the observed current, hence confirming the specificity of the system. These findings demonstrated the potential of the proposed biosensor.Graphical abstractGraphical abstract for this article
       
  • Fabrication of a highly sensitive and selective modified electrode for
           imidacloprid determination based on designed nanocomposite graphene
           quantum dots/ionic liquid/multiwall carbon nanotubes/polyaniline
    • Abstract: Publication date: Available online 11 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Parisa Nasr-Esfahani, Ali A. Ensafi, Behzad Rezaei In this paper, a simple, selective and sensitive electrochemical method was developed for the determination of imidacloprid. To fabricate the modified electrode, at first, a glassy carbon electrode (GCE) was modified with a nanocomposite consist of graphene quantum dots/ionic liquid/multiwall carbon nanotubes (GQDs/IL/MWCNTs). Then, polyaniline (PANI) film was formed on the surface of GQDs/IL/MWCNTs by electropolymerization via cyclic voltammetry at a surface of the modified GCE. Field emission scanning electron microscopy and transmission electron microscopy were used for elucidation the GQDs/IL/MWCNTs/PANI surface characterization. For investigation the electrochemical behavior of imidacloprid at the GCE/GQDs/IL/MWCNTs/PANI, cyclic voltammetry and differential pulse voltammetry techniques were utilized. Also, the effective variables on the modified electrode such as pH, electropolymerization cycles, accumulation potential and accumulation time were studied. The proposed modified electrode showed a linear range from 0.03 to 12.0 µmol L-1 imidacloprid with a detection limit of 9 nmol L-1. This modified electrode exhibited good repeatability and excellent selectivity. The proposed modified electrode was employed for imidacloprid determination in vegetable samples.Graphical abstractGraphical abstract for this article
       
  • Nanocrystalline LaCoO3 modified by Ag nanoparticles with improved
           sensitivity to H2S
    • Abstract: Publication date: Available online 11 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Valentina Chumakova, Artem Marikutsa, Marina Rumyantseva, Didier Fasquelle, Alexander Gaskov Semiconductor mixed-metal oxides with perovskite structure are of increasing interest for the application in chemical sensors. LaCoO3 has been extensively studied for its peculiar electronic and magnetic properties, but less is known of the gas sensing mechanisms of this material and its composites. In this work, nanocrystalline LaCoO3 was synthesized by sol-gel method and functionalized by Ag nanoparticles. An improved sensitivity to H2S was observed for Ag/LaCoO3 sensors, in contrast to pure LaCoO3 sensor. The Ag/LaCoO3 sensors had minimum cross-sensitivity to CO and NH3 interfering gases, which were present at higher concentrations than H2S. The role of Ag nanoparticles in the selective sensitivity of Ag/LaCoO3 nanocomposites to H2S gas were unveiled using in situ infrared (DRIFT) spectroscopy.
       
  • Optical Hygrometer using Light-sheet Skew-ray Probed Multimode Fiber with
           Polyelectrolyte Coating
    • Abstract: Publication date: Available online 11 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): George Y. Chen, Xuan Wu, Christophe A. Codemard, Li Yu, Xiaokong Liu, Haolan Xu, Tanya M. Monro, David G. LancasterABSTRACTThe measurement of humidity provides valuable information to a range of industries. Existing hygrometers lack the combination of high sensitivity/low detection-limit, temperature insensitivity, fast response, high robustness and low cost. We present a new design of humidity sensors based on the combination of a polymer-coated multimode fiber interrogated by a light sheet (i.e. thin plane of light) designed to precision excite the optimum group of skew rays for enhanced sensitivity. The sensing mechanism is water absorption of light via evanescent-wave interaction mediated by a polymer-coated multimode fiber. For a 10.0 bilayer poly(diallyldimethylammonium) (PDDA)/poly(styrenesulfonate) (PSS)-coated sensing fiber, we demonstrated a sensitivity of up to 0.14 dB/%RH/cm, a detection limit of 0.007%RH, a temperature cross-sensitivity of less than ˜0.13%/°C, and response/recovery times of 115 ms and 200 ms. The tested dynamic range is between 10%RH and 94%RH. The dependence on the total optical power rather than the phase of light makes such sensors relatively insensitive to temperature while remaining sensitive to humidity. The PDDA/PSS functional coating inherently offers fast response. The use of multimode fibers and power meters make such fiber-optic sensors highly robust and relatively inexpensive, easing the translation to practical applications.Graphical abstractGraphical abstract for this article
       
  • A colorimetric sensor array for protein discrimination based on carbon
           nanodots-induced reversible aggregation of AuNP with GSH as a regulator
    • Abstract: Publication date: Available online 10 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Jingwei Sun, Yuexiang Lu, Liuying He, Jiawei Pang, Fengyi Yang, Yueying Liu We have proposed a doubled nanoplasmonic colorimetric sensor array for protein recognition based on car-bon nanodots (CDs)-induced reversible aggregation of gold nanoparticle (AuNP) with GSH as a regulator. It is found that different kinds of CDs can induce the aggregation of AuNP with different degrees and cause different color change. Adding reduced glutathione (GSH) into the CDs/AuNP system can make the AuNP disperse again accompanying with a second color change. Based on this phenomenon, three kinds of CDs originated from different amino acids and citric acid are used to fabricate a colorimetric sensor array with three sensing elements. Upon addition of target proteins into CDs/AuNP conjugates, the competitive protein-AuNP affinity disrupts the SPR absorption peak of CDs/AuNP, generating cross-reactive three-unit colorimetric signal. Subsequently, GSH is introduced into each unit containing protein samples in situ. The SPR absorption peak of AuNP is substantially affected due to the stronger affinity between AuNP and GSH, producing an-other three-unit response signal. With this strategy, each sensing element can give two output signals to each target protein, which doubles the number of unit from three to six without changing the three-cell configuration, resulting in greatly improved discrimination ability of proteins and identification accuracy of unknown samples. Twelve proteins at 50 nM can be well discriminated by this novel colorimetric sensor array. Moreover, our sensing system is very stable in the high concen-tration of salt, make it suitable for the real sample analysis. This method effectively identifies twelve proteins at 200 nM spiked in human urine.Graphical Graphical abstract for this articleWe have developed a doubled nanoplasmonic colorimetric sensor array for protein recognition based on carbon nanodots-induced reversible aggregation of gold nanoparticle (AuNP) with GSH as a regulator. Each one well of the array can give two output signals in situ for each target protein by using this strategy, which doubles the sensing unit number of the sensor array from three to six without changing the three-cell configuration, resulting in greatly improved discrimination ability of proteins and identification accuracy of unknown samples. Moreover, our sensing system is very stable in the high concentration of salt, which makes it suitable for real sample analysis.
       
  • Visualization of sulfur mustard in living cells and whole animals with a
           selective and sensitive turn-on fluorescent probe
    • Abstract: Publication date: Available online 10 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Wenqi Meng, Hao Zhang, Liang Xiao, Xintong Chen, Mingxue Sun, Qingqiang Xu, Yongbing Cao, Kai Xiao, Zhengjiang Li Sulfur mustard is a potent blister agent and one of the most harmful chemical warfare agents. To explore the toxicokinetics and biodistribution of SM, a reliable detection method for monitoring sulfur mustard would be indispensable. We describe the design, synthesis and application of a selective and sensitive turn-on fluorescent probe for sulfur mustard detection. A good linear relationship between fluorescence emission intensity and SM concentration was observed. The probe, SM-Flu, was applied to the determination and imaging of sulfur mustard in living cells and Aurelia coerulea polyps. With SM-Flu, concentration and time profiles for SM in mouse brain after exposure to SM were first measured.
       
  • A new ratiometric and colorimetric fluorescent Th4+ probe under extreme
           acidity and cell imaging
    • Abstract: Publication date: Available online 10 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Bo Liu, Yanhong Tan, Qinghua Hu, Yuyuan Wang, Yu Mao, Peng Tao, Hongqing Wang It is always a significant challenge to develop a probe for Th4+ in the environment and in vivo under extreme acidity conditions, especially on real-time in the field. Herein, a new Th4+ fluorescent probe N1',N2'-bis((3-hydroxytetrastyrene-2 yl)methylene malonohydrazide (BH-TPE) was designed and studied. It could realize to detect Th4+ in a ratiometric way, which showed relative strong blue fluorescence at 450 nm and yellow-green fluorescence at 522 nm in the absence or present of Th4+, respectively, with good selectivity and sensitivity under extreme acidity environment. And the value of I522 /I450 of the probe had good linear relationship with Th4+ ion concentration in the range of 0 to 10 μM and the low detection limit 2 × 10-8 M. Meanwhile, it could monitor Th4+ ion by “naked eye” in the field on real-time due to the BH-TPE solution changed from colorless to light green with the increase of Th4+. Moreover, the possible fluorescent mechanism was proposed. Most importantly, the viability of BH-TPE to Th4+ ion was successfully applied to live cell imaging and environmental sample.Graphical abstractGraphical abstract for this article
       
  • Realization of Au-Decorated WS2 nanosheets as low power-consumption and
           selective gas sensors
    • Abstract: Publication date: Available online 8 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Jae-Hun Kim, Ali Mirzaei, Hyoun Woo Kim, Sang Sub Kim We introduced a selective and self-heated CO gas sensor based on Au-decorated WS2 nanosheets. Au nanoparticles (NPs) were decorated on WS2 NSs using UV irradiation technique at different irradiation times (1, 15 and 30 s). SiO2 grown on Si was used as substrates and the gas sensors with top electrode configuration were fabricated. Gas sensors were able to work under self-heating mode with an applied voltage of 2 V for selective CO sensing. The results of CO gas sensing demonstrated the promising effects of Au for the enhanced response and selectivity towards CO gas. Also, the low-voltage operation at room temperature resulted in low-power consumption. This study demonstrates realization of selective CO gas sensor using a facile approach along with low power consumption.
       
  • Novel potential and current type chiral amino acids biosensor based on
           L/D-handed double helix carbon nanotubes@polypyrrole@Au
           nanoparticles@L/D-cysteine
    • Abstract: Publication date: Available online 7 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Qi Zhang, Mingxuan Fu, Haijun Lu, Xinyu Fan, Haiyang Wang, Yufan Zhang, Huan Wang Novel chiral amino acids biosensor based on both potential difference and current ratio simultaneously was first established by employing left/right-handed double helix carbon nanotubes (L/D-DHCNT) with chiral structure as substrate material, and by self-assembly anchoring L/D-cysteine (L/D-Cys) on the surface of the left/right-handed double helix carbon nanotubes@Polypyrrole@Au nanoparticles nanocomposites (L/D-DHCNT@PPy@AuNPs). In this work, L/D-DHCNT@PPy@AuNPs@L/D-Cys was successfully constructed via a facile and environment-friendly process. Interestingly, in order to obtain highly dispersed AuNPs deposited on L/D-DHCNT, polypyrrole polymerized from pyrrole acts as a locating agent. Owing to the combination of unique performance of the L/D-Cys and L/D-DHCNT with chiral structure, and PPy and AuNPs with outstanding conductivity, an extremely efficient electrochemical chiral biosensing system was constructed that exhibited enhanced conductivity, sensitivity and chiral recognition capacity for tyrosine (Tyr), tryptophan (Trp) and glutamic acids (Glu) enantiomers. Utilizing both the potential difference and current ratio signal to commendably realize the electrochemical recognition and quantitative determination of amino acid enantiomers in their racemic solution. In addition, achieving the detection of Tyr in tablet samples by fabricated ultra-efficient electrochemical chiral biosensing system. Therefore, L/D-DHCNT@PPy@AuNPs@L/D-Cys as novel and ultrasensitive chiral biosensing system possesses the capability of chiral recognition of amino acid enantiomers, and it opens up the potential application of L/D-DHCNT@PPy@AuNPs@L/D-Cys in the field of chiral biosensors.Graphical abstractGraphical abstract for this article
       
  • Ultrasensitive detection of norovirus using a magnetofluoroimmunoassay
           based on synergic properties of gold/magnetic nanoparticle hybrid
           nanocomposites and quantum dots
    • Abstract: Publication date: Available online 7 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Kenshin Takemura, Jaewook Lee, Tetsuro Suzuki, Thoshimi Hara, Fuyuki Abe, Enoch Y. ParkABSTRACTNorovirus is the cause of the contagious disease gastroenteritis, and the infection is easy to spread because of the high infectivity of this virus. When the virus infects elderly people and young children, it may progress to severe disease. To prevent this hygienic threat, the development of highly sensitive and rapid detection methods is urgently needed. In this study, we developed a localized surface plasmon resonance (LSPR)-amplified magnetofluoroimmunoassay that can be used to detect norovirus even in biocomplex media without decreasing the fluorescence response. A multi-functional gold nanoparticle (AuNP) and magnetic nanoparticle (MNP) hybrid nanocomposite was synthesized. The AuNP/MNP hybrid nanocomposites and CdSeS quantum dots (QDs) were conjugated by the anti-norovirus genogroup II antibody (Ab). This hybrid nanocomposite made it possible to separate the target virus from impurities by a magnetic field and induced a high LSPR effect. Target virus was added to the Ab-conjugated AuNP/MNP composite and Ab-CdSeS QDs, and then Au/MNPs-Ab-virus-Ab-CdSeS QDs were separated by using an external magnetic field. The target norovirus-like particles can be detected in the range of 1 pg/ml to 5 ng/ml with a limit of detection (LOD) of 0.48 pg/ml in feces. This detection method was applied to clinical samples of feces containing norovirus from patients, and the LOD was 84 copies of RNA/ml without being affected by the impurities contained in the feces solution. This novel sensing system is suitable for norovirus detection in feces samples and for on-site detection.
       
  • Anion-Exchangeable Modulated Fluorescence Strategy for Sensitive Ascorbic
           Acid Detection with Luminescent Eu Hydroxy Double Salts Nanosunflowers
           Derived from MOFs
    • Abstract: Publication date: Available online 7 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Ali Li, Jie Zhang, Shihao Sun, Erli Ding, Fengjuan Chen, Suisui He, Tianrong Li, Sha Liu, Baodui Wang To improve the sensitivity and avoid the interference of other substances to the detection of ascorbic acid (AA), luminescent Eu hydroxy double salts (Eu HDSs) sunflowers were developed for fluorescence turn-off detection of AA based on anion-exchangeable strategy. Such Eu HDSs nanoprobe was synthesized by using a leaf-like metal–organic-framework-5 (MOF-5-L) as both precursor and template and europium (III) trifluoroacetate trihydrateas a second precursor. The mechanism of the luminescence inhibition of the Eu HDSs nanosunflowers was studied, and the intercalation of anionic AA- species into an interlayer of Eu HDSs helped to enhance luminescence inhibition, which was quite different from the reported redox-based fluorescent sensing system. Because of the existence of space effect and hydrogen bond between the AA and the OH group on the Eu HDSs surface, such nanoprobe showed excellent sensitivity and selectivity for AA detection, with the detection limit of 1.46 nM. Moreover, the nanoprobe was successfully used for sensitive and selective AA assays in human body fluids, proving that the proposed sensing platform has great potential in the clinical diagnosis and drug screening.
       
  • Dual sites fluorescence probe for H2S and Hg2+ with “AIE Transformers”
           function
    • Abstract: Publication date: Available online 7 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Jianting Yang, Binsheng Yang, Guangming Wen, Bin Liu Dual sites fluorescence compound 1 based on 5-bromosalicylaldehyde and 2-benzothiazoleacetonitrile was synthesized. 1 exhibited different aggregation-induced emission (AIE) state in different solution boosting different emission. Different aggregated states gave different chance for H2S and Hg2+ to respond with the formation of new aggregated states. Especially, 1 responded to H2S selectively with an ultrafast rate within 20 s. Intramolecular and intermolecular hydrogen bonding play an important role on the aggregated state conversion. Herein, the notion of “AIE Transformers” was put forward for the first time. It permits us to study their aggregation state with their photophysical and functional changes.Graphical abstractGraphical abstract for this article
       
  • Highly sensitive dual-wavelength fiber ring laser sensor for the low
           concentration gas detection
    • Abstract: Publication date: Available online 7 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Xianchao Yang, Liangcheng Duan, Haiwei Zhang, Ying Lu, Guangyao Wang, Jianquan Yao A highly sensitive low concentration gas sensor based on dual-wavelength Erbium-doped fiber ring laser (EDFRL) is designed and demonstrated. The dual-wavelength lasing output is introduced by a tunable Fabry-Perot (F-P) filter and a fiber Bragg grating (FBG) due to the mode competition as they both share a same EDF gain medium. One wavelength at 1530.37 nm serving as the sensing element is inserted by a hollow core photonic crystal fiber (HCPCF) gas cell which can bring in much more power change when the cavity loss slightly varies while the other wavelength at 1532.38 nm acting as a reference. Experimental results show that the sensor can achieve a good linear response (R2 = 0.9864) to acetylene concentration variation and a minimum detection limit (MDL) of 10.42 ppmV at 20 s response time, which is the lowest to our best knowledge and improving 6.44 times than that of single-wavelength EDFRL based. Moreover, the absolute detected error induced by the power fluctuation (< 0.1 dB) is less than 1.78% over more than 300 s of observation.
       
  • Electrochemical aptasensing strategy for kanamycin detection based on
           target-triggered single-strand DNA adsorption on MoS2 nanosheets and
           enzymatic signal amplification
    • Abstract: Publication date: Available online 6 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yunlei Zhou, Fei Li, Hanwen Wu, Yan Chen, Huanshun Yin, Shiyun Ai, Jun Wang A selective and sensitive electrochemical aptasensing strategy was developed for kanamycin detection based on target-triggered single-strand DNA adsorption on MoS2 nanosheets and enzymatic signal amplification. Firstly, a Y-shape double-stranded DNA (dsDNA) was designed containing probe DNA, assist DNA (labeled with biotin at its 3′-terminal) and aptamer DNA. Then, in the presence of kanamycin, aptamer DNA can be released from the Y-shape dsDNA structure due to its interaction with kanamycin to form stable conjugate, which will destroy the Y-shape dsDNA structure and lead to the presence of two-fragment of single-stranded DNA (ssDNA) on the remained half-hybrid DNA structure (containing probe DNA and assist DNA). Based on the strong interaction between ssDNA and MoS2 nanosheets, the half-hybrid DNA structure can be captured on MoS2 nanosheets modified electrode surface, which triggers the subsequent immobilization of streptavidin-alkaline phosphatase (SA-ALP) compound. Under the catalysis of ALP, p-nitrophenol phosphate (PNPP) is hydrolyzed to produce p-nitrophenol (PNP). Based on the linear relationship between the electrochemical oxidation signal of PNP and kanamycin concentration, kanamycin can be detected with the detection limit of 0.029 nM (S/N = 3). The aptamer-MoS2 nanosheets based electrochemical biosensor shows good selectivity, reproducibility for kanamycin detection.Graphical abstractGraphical abstract for this article
       
  • Interface engineered WS2/ZnS heterostructures for sensitive and reversible
           NO2 room temperature sensing
    • Abstract: Publication date: Available online 6 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yutong Han, Yang Liu, Chen Su, Shutang Wang, Hong Li, Min Zeng, Nantao Hu, Yanjie Su, Zhihua Zhou, Hao Wei, Zhi Yang The inherent high surface areas and unique semiconducting properties of two-dimensional (2D) transition metal dichalcogenides (TMDs) make them attractive for the sensing applications. However, the challenges of sensitivity, recoverability and stability still need to be overcome for the rapidly developing fields of TMD based gas sensors. With the general advantages of 2D nanomaterials, construction of 2D TMD based heterostructure is an effective approach for improving their sensing performance by the synergistic effects of hybridization. Herein, we design a novel tungsten disulfide (WS2)/zinc sulfide (ZnS) based TMD heterostructure to realize quick and reversible nitrogen dioxide (NO2) detection at room temperature (25 °C). Specifically, the engineered 2D/0D WS2/ZnS p–n heterostructure gives a desired sensitivity of 32.5 to 5 ppm NO2 with a fast response speed of 4 s, which is dramatically enhanced compared with that of pure WS2 nanosheets. More importantly, WS2/ZnS heterostructure based gas sensor can achieve full recovery state after each sensing cycle without using external energies, showing an excellent recyclability at room temperature. The optimal sensor also exhibits low detection concentration of 10 ppb, high selectivity as well as outstanding long-term stability. Such impressive features originating from the synergistic effects of WS2/ZnS heterostructure have been discussed in detail from the geometrical, electronic and chemical effects. These outstanding sensing properties of WS2/ZnS heterostructure sensor imply the possibility of using this novel nanostructure in highly efficient NO2 room temperature sensing applications.
       
  • An integrated self-driven microfluidic device for rapid detection of the
           influenza A (H1N1) virus by reverse transcription loop-mediated isothermal
           amplification
    • Abstract: Publication date: 1 October 2019Source: Sensors and Actuators B: Chemical, Volume 296Author(s): Yu-Dong Ma, Yi-Sin Chen, Gwo-Bin Lee Influenza A is amongst the most infectious diseases of the past decade. Although rapid and accurate detection can efficiently prevent its spread, the sensitivity and specificity of current rapid influenza diagnostic tests (RIDTs) are relatively low. In this study, a self-driven microfluidic device was developed to rapidly detect the H1N1 influenza virus via a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay. The device was capable of 1) virus isolation via H1N1-specific aptamers conjugated magnetic beads, 2) virus lysis, 3) isothermal nucleic acid amplification, and 4) colorimetric detection of the virus. The limit of detection was measured to be only 3 × 10−4 hemagglutinating units (HAU)/reaction, which is sensitive enough for clinical applications. The entire procedure could be performed in only 40 min by capillary forces through a novel polydimethylsiloxane surface treatment in cooperation with hydrophobic soft valves. This is the first time that a simple, self-driven passive microfluidic chip has been demonstrated to be capable of performing sample pretreatment, RT-LAMP, and H1N1 virus detection on a single chip. This microfluidic chip may therefore serve a promising RIDT with high sensitivity and high specificity for point-of-care diagnostics in the near future.Graphical abstractA self-driven microfluidic device was developed to rapidly detect the H1N1 influenza virus via a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay.Graphical abstract for this article
       
  • Homogeneous fluorescent biosensing method for DNA methyltransferase
           activity analysis and inhibitor screening based on highly efficient
           isothermal amplification
    • Abstract: Publication date: Available online 5 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Tong Wang, Haiying Que, Wenbin Cheng, Xiaoyu Yan, Hongmin Ma, Ping Liu, Xiufeng Gan, Yurong Yan DNA methyltransferase (MTase) activity assay and its inhibitor screening are important for the diagnosis and treatment of methylation-related diseases. Herein, a label-free and highly sensitive biosensing method based on entropy-driven reaction and toehold-initiated rolling circle amplification (TIRCA) was developed for DNA MTase activity detection and inhibitor screening. Briefly, in the presence of MTase, the triple-stranded complex (TSC) could be methylated to avoid cleaving by MboI endonuclease. The complete TSC was able to initiate downstream entropy-driven reaction and TIRCA to produce G-quadruplex that can bind with Thioflavin T (ThT) to output fluorescent signal. Under the optimal experimental conditions, the established biosensing strategy could detect Dam MTase down to 0.06 U/mL with a linear range from 0.1 U/mL to 40 U/mL. Importantly, the signal-to-noise (S/N) of this biosensing strategy was extremely high. This strategy could discriminate target Dam MTase from another two MTases efficiently. Moreover, this developed biosensing method was applied to screen DNA MTase inhibitors. Therefore, we anticipate this unique strategy will serve as an alternative tool to detect DNA MTase activity and screen its inhibitors in clinical diagnosis and therapeutics.
       
  • Improvement of sensing properties for SnO2 gas sensor by tuning
           of exposed crystal face
    • Abstract: Publication date: Available online 4 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Pil Gyu Choi, Noriya Izu, Naoto Shirahata, Yoshitake Masuda In this study, a SnO2 nanosheet was successfully synthesized under moderate conditions without using any additive. The crystal growth direction and the mainly exposed crystal face of the SnO2 nanosheet were investigated. The relationship between the exposed crystal face and the gas sensing properties was also investigated. It was confirmed that the SnO2 nanosheet has a plain size of ˜100 nm and a mainly exposed (101) plane. The SnO2 nanosheet exhibited selectively higher sensor signal response for H2 than CH4 gas, while the SnO2 nanoparticle with a mainly exposed the most stable (110) plane, which was prepared for comparison purposes, exhibited a selectively lower sensor signal response for H2 than CH4 gas. The 90% response and recovery times for the SnO2 nanosheet were faster than those for the SnO2 nanoparticle for both H2 and CH4 gases. Different chemical states were observed on the SnO2 surfaces. Therefore, it was considered that the reaction with the target gas on the SnO2 nanoparticle was dominantly induced by oxygen adsorbed on the SnO2 surface. However, the reaction was dominantly induced by oxygen bound to Sn on the SnO2 nanosheet, due to the ease of conversion of the Sn valency state according to adsorption and desorption of oxygen on the (101) surface as compared to the (110) surface.
       
  • A smartphone-based colorimetric PET sensor platform with molecular
           recognition via thermally initiated RAFT-mediated graft copolymerization
    • Abstract: Publication date: Available online 4 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Ceren Kaymaz Kuşçuoğlu, Hasan Güner, Meshude Akbulut Söylemez, Olgun Güven, Murat Barsbay In this work, we report a low-cost and easy-to-use molecularly-imprinted colorimetric sensor platform that can sense target analyte with high sensitivity and good selectivity. The platform has been examined for colorimetric detection and quantitation of a model textile dye, basic red 9 (BR9), by employing methacrylic acid (MAA), ethylene glycol dimethacrylate (EGDMA) and cumyl dithiobenzoate (CDB) as functional monomer, crosslinker and RAFT agent, respectively. Benzophenone (BP), a photoinitiator, was covalently immobilized on the surface of poly(ethylene terephthalate) (PET) and then thermally activated by homolytic cleavage to form radicals on the surface that initiate RAFT-mediated grafting of a thin recognition layer. The molecularly imprinted polymer (MIP) layer of about 100 nm showed excellent removal of 76.7 % target dye in 10 minutes and high selectivity compared to other similar dyes with an imprinting factor of 10.31 in the competitive environment. The resulting MIP grafted PET substrate was efficiently used as recognition unit in a smartphone-based colorimetric detection method using a color adaptation algorithm for point-of-care applications. Based on the obtained performance, it is promising to use the method for the detection and quantification of various analytes with chromophores.
       
  • Gold nanocluster-based fluorescence turn-off probe for sensing of
           doxorubicin by photoinduced electron transfer
    • Abstract: Publication date: Available online 4 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Kai-Yuan Huang, Hong-Xing He, Shao-Bin He, Xiang-Ping Zhang, Hua-Ping Peng, Zhen Lin, Hao-Hua Deng, Xing-Hua Xia, Wei Chen Doxorubicin (DOX), an anthraquinone-based anticancer drug, is effective for the treatment of a variety of human tumors. However, due to its narrow therapeutic window, serum levels need to be closely monitored. Herein, we report the development of a novel fluorescence probe based on gold nanoclusters co-modified with dithiothreitol (DTT) and carboxylated chitosan (CC) (CC/DTT-AuNCs) for the determination of DOX. The emission from the CC/DTT-AuNCs is significantly suppressed by DOX. The fluorescence-quenching mechanism involving DOX was systematically explored, and photoinduced electron transfer was identified to play a dominant role. DOX readily binds to the CC/DTT-AuNC surface through electrostatic attraction, after which it accepts the electron from the photoexcited CC/DTT-AuNC and quenches its fluorescence. We found that other anthraquinone structures (e.g., alizarin and emodin) devoid of –NH2 groups exhibited almost no CC/DTT-AuNCs fluorescence-quenching effect due to weak electrostatic interactions between these anthraquinones and the NCs. A linear relationship between photoluminescence suppression and the concentration of DOX was observed in the 0.05–2 μM range under the optimal experimental conditions, with a detection limit as low as 5 nM. This new sensing approach was also used to successfully measure DOX in human serum samples with satisfactory results obtained.Graphical abstractGraphical abstract for this article
       
  • A three-dimensional cloth-based microfluidic label-free proximity
           hybridization-electrochemiluminescence biosensor for ultrasensitive
           detection of K-ras gene
    • Abstract: Publication date: Available online 4 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yan Su, Yi Liang, Hongyang Wu, Jun Jiang, Wei Lai, Chunsun Zhang In this work, we firstly propose a cloth-based microfluidic DNA biosensor capable of label-free proximty hybridization-electrochemiluminescence (PH-ECL) detection of target DNA (T-DNA). Carbon ink screen-printing is applied to make the cloth-based electrodes that are patterned with wax-screen-printed cloth-based chambers to fabricate a foldable three-dimensional (3-D) cloth-based device for facile fabrication of MWCNTs-modified PH-ECL sensing interface. When the PH complexes (PC) formed by the T-DNA and help DNA sequences (H-DNA1 and H-DNA2), together with Ru(bpy)32+ (TBR) molecules, are applied onto such a sensing interface, the TBR/tripropylamine (TPA)-based PH-ECL can be well triggered. Under optimized conditions, the biosensor has successfully fulfilled the label-free detection of K-ras gene in the linear range of 0.001-2500 pM, with a detection limit of 0.13 fM. The emission of PH-ECL on the cloth-based device exhibits a relatively high sensitivity, specificity, reproducibility and stability, possibly due to the good formation of "H"-shaped complexes on the electrode. Especially, the biosensor has the ability for K-ras gene detection in complex human serum samples, identification of single-base-mismatched and even two-base-mismatched K-ras gene targets, and universal determination of different T-DNA samples. Thus, it may become a promising avenue for gene diagnostics with wide applications.Graphical abstractGraphical abstract for this article
       
  • Ratiometric fluorescent detection of azodicarbonamide based on silicon
           nanoparticles and quantum dots
    • Abstract: Publication date: Available online 3 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Junyang Chen, Mengke Wang, Xingguang Su Herein, a novel ratiometric fluorescent probe (SiNPs@QDs) was constructed for quantitative detection of ADA in flour for the first time. The ratiometric fluorescent probe (SiNPs@QDs) based on silicon nanoparticles (SiNPs) and CdTe quantum dots (QDs) showed two well-resolved emission peaks at 445 nm and 632 nm, respectively. The fluorescence peak at 632 nm was quenched by mercury ions (Hg2+) through ion-binding and electron transfer processes. However, with the presence of glutathione (GSH), the fluorescence peak at 632 nm was recovered due to the strong affinity between the sulfydryl of GSH and Hg2+. Further, after adding ADA, the sulfydryl (−SH) was oxidized into disulfide bond (S − S), and Hg2+ was released from the sulfydryl of GSH and quenched the fluorescence at 632 nm again, whereas the fluorescence intensity of SiNPs@QDs at 445 nm was unchanged all the time. It exhibited an excellent linear relationship between the fluorescence intensity ratio (F632/F445) and the concentration of ADA in the range of 0.05–4 μM with a detection limit of 0.016 μM. Furthermore, the established method was successfully utilized to the detection of ADA in flour with satisfactory results.Graphical abstractSchematic illustration of ratio fluorescence probe for ADA detection based on silicon nanoparticles@quantum dots assembly.Graphical abstract for this article
       
  • A novel versatile animal-free 3D tool for rapid low-cost assessment of
           immunodiagnostic microneedles
    • Abstract: Publication date: Available online 3 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Stella Totti, Keng Wooi Ng, Lorraine Dale, Guoping Lian, Tao Chen, Eirini G. Velliou Microneedle devices offer minimally invasive and rapid biomarker extraction from the skin. However, the lack of effective assessment tools for such microneedle devices can delay their development into useful clinical applications. Traditionally, the microneedle performance is evaluated i) in vivo, using animal models, ii) ex vivo, on excised human or animal skin or iii) in vitro, using homogenised solutions with the target antigen to model the interstitial fluid. In vivo and ex vivo models are considered the gold-standard approach for the evaluation of microneedle devices because of their structural composition, however they do exhibit limitations. More specifically, they have limited availability and they present batch-to-batch variations depending on the skin origin. Furthermore, their use rises ethical concerns regarding compliance with the globally accepted 3Rs principle of reducing the use of animals for research purposes. At the same time, in vitro models fail to accurately mimic the structure and the mechanical integrity of the skin tissue that surrounds the interstitial fluid. In this study, we introduce for the first time an animal-free, mechanically robust, 3D scaffold that has great potential as an accurate in vitro evaluation tool for immunodiagnostic microneedle devices. More specifically, we demonstrate, for the first time, successful extraction and detection of a melanoma biomarker (S100B) using immunodiagnostic microneedles in the 3D culture system. Melanoma cells (A375) were cultured and expanded for 35 days in the highly porous polymeric scaffold followed by in situ capture of S100B with the microneedle device. Scanning electron microscopy showed a close resemblance between the 3D scaffold and human skin in terms of internal structure and porosity. The microneedle device detected S100B in the scaffold (with a detection pattern similar to the positive controls), while the biomarker was not detected in the surrounding liquid supernatants. Our findings demonstrate the great potential of this animal-free 3D tool for rapid and low-cost evaluation of microneedle devices.
       
  • Solid state electrolyte type gas sensor using stabilized zirconia and
           MTiO3 (M: Zn, Co and Ni)-SE for detection of low concentration of SO2
    • Abstract: Publication date: Available online 3 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Jing Wang, Ao Liu, Caileng Wang, Rui You, Fangmeng Liu, Siqi Li, Zijie Yang, Junming He, Xu Yan, Peng Sun, Geyu Lu This paper deals with solid state electrolyte type gas sensors based on mixed potential mechanism using yttria-stabilized zirconia (YSZ) as solid electrolyte and MTiO3 (M: Zn, Co and Ni) as sensing electrodes (SEs) for monitoring very low concentrations of SO2 in atmospheric environments. Among all the devices attached with different SEs, ZnTiO3-SE brought about the highest response value of -22.5 mV to 1 ppm SO2 at 600 ℃ and even down to 100 ppb SO2 with the response value of -2.5 mV. Meanwhile, the measured ΔV of the sensor was found to vary linearly as a function of the logarithm of SO2 concentration in the range of 100 ppb – 2 ppm at 600 ℃ and the sensitivity (slop) was −23 mV/decade. In addition, the sensor coupled with ZnTiO3-SE gave negligible responses to other interfering gases such as C2H2, CH4, CO, NO2, NO, NH3. Furthermore, the present sensor possessed good repeatability, slightly affected by the change of oxygen concentration and relatively stability during 20 days of continuous high-temperature operation. Moreover, the polarization-curve measurements demonstrated that the good agreement between the observed sensitivity and the estimated value, confirming that the sensing mechanism was based on mixed-potential model.
       
  • High-performance carbon black/molybdenum disulfide nanohybrid sensor for
           cocoa catechins determination using an extraction-free approach
    • Abstract: Publication date: Available online 3 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Flavio Della Pelle, Daniel Rojas, Annalisa Scroccarello, Michele Del Carlo, Giovanni Ferraro, Carla Di Mattia, Maria Martuscelli, Alberto Escarpa, Dario Compagnone In this work, for the first time, the ability to detect catechins on an effective and regenerable carbon black/molybdenum disulfide nanohybrid screen-printed electrode (SPE-CB/MoS2) is demonstrated. The proposed SPE-CB/MoS2 merges the ability of CB to improve the electrochemical response with the proprieties of MoS2 to totally prevent catechins irreversible polymerization and adsorption onto the electrode surface occurring at both bare and CB-modified SPEs. The MoS2 anti-fouling ability has been demonstrated using both flavanols standards and complex samples thus proved to be an unexpected and useful characteristic. The SPE-CB/MoS2 allowed an improvement of sensitivity (LOD ≤ 0.17 µmol L-1) of 100-folds compared to the bare SPE electrode, showing linear range between 0.12 and 25 µmol L−1 with good determination coefficients (R2 ≥ 0.998). Cocoa powder samples have been analyzed employing the developed hybrid sensor and compared with classical methods for polyphenols evaluation as Folin- Ciocalteu (F.C.), ABTS and an AuNPs based assay. The SPE-CB/MoS2 allow to obtain repeatable and reproducible results which also were significantly correlated with classical methods (r = 0.95–0.97). Noteworthy, after the measurements of 59 cocoa samples the electrode was still active (recovery signal 99 %). Using the extraction-free approach with the SPE-CB/MoS2 sensor the whole analysis of cocoa powder catechins required only 15 minutes.Graphical abstractGraphical abstract for this article
       
  • A turn-on fluorescent chemosensor based on aggregation-induced emission
           for cyanide detection and its bioimaging applications
    • Abstract: Publication date: Available online 3 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Kailun Deng, Lei Wang, Qi Xia, Ruiyuan Liu, Qu Jinqing Numerous efforts are contributed to develop fluorescent sensors for qualitative and quantitative detection of cyanide anion (CN−) as it is inevitably utilized in various fields and detrimental to human health and ecosystem. Herein, a new fluorescent probe TCNT with the feature of aggregation-induced emission was designed and synthesized. Owning a large Stokes shift (˜148 nm) and red fluorescent emission (596 nm), TCNT showed high specific and sensitivity (detection limit equals to 0.35 μmol L-1) to CN− with a 2.53-fold enhancement of quantum yield in aqueous solutions. The recognition mechanism of TCNT sensing cyanide was ascribed to nucleophilic attack of CN− toward vinyl group, which was confirmed by 1H NMR titration and DFT calculations. Test strips loaded with TCNT demonstrated its convenient detection for cyanide ion in real environment. In addition, because of good biocompatibility and low cytotoxicity, TCNT was applied for monitoring the levels of CN− in HeG-2 cells by confocal laser scanning microscopy. Moreover, fluorescence imaging of isolated organs of mice proved that TCNT is capable of achieving bioimaging in live organisms.Graphical Graphical abstract for this article
       
  • Plasmonic Colorimetric Biosensor for Visual Detection of Telomerase
           Activity Based on Horseradish Peroxidase-Encapsulated Liposomes and
           Etching of Au Nanobipyramids
    • Abstract: Publication date: Available online 3 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Danni Wang, Yingzhi Zhang, Xiayu Zhao, Zhangrun Xu Telomerase aberrant activation is a critical feature in the vast majority of cancers. To visualize telomerase expression level in tumor cells, we developed a plasmonic colorimetric sensor for highly sensitive detection of telomerase activity by integrating an excellent etching substrate Au nanobipyramids (Au NBPs) with a liposome-based signal amplification strategy. Upon telomerase-triggered extension, the telomerase activity was converted into the amount of the attached horseradish peroxidase-encapsulated liposomes (HRP-Ls) on the surfaces of magnetic beads. Afterwards, HRP was liberated from the liposomes following the addition of H2O2-3,3′,5,5′-tetramethylbenzidine sulfate (TMB) substrate, and then the oxidation reaction between H2O2 and TMB was initiated to form TMB2+. The morphological evolution of Au NBPs relied on the TMB2+-mediated etching reaction, which gave rise to tremendous localized surface plasmon resonance (LSPR) responses and concomitant tonality transitions. Benefiting from cascaded signal amplification capacity of HRP-Ls and the intriguing optical properties of Au NBPs, an impressive sensitivity toward telomerase was obtained with detection limits equivalent to 1 HeLa cell for LSPR peak measurement and a visual detection limit of 20 HeLa cells. Furthermore, a facile and portable kit was fabricated for visual evaluation of telomerase activity in different cell lines.Graphical abstractGraphical abstract for this article
       
  • On-site monitoring of thiram via aggregation-induced emission enhancement
           of gold nanoclusters based on electronic-eye platform
    • Abstract: Publication date: Available online 1 June 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Xu Zhao, Deshuai Kong, Rui Jin, Hongxia Li, Xu Yan, Fangmeng Liu, Peng Sun, Yuan Gao, Geyu Lu The rapid and on-site monitoring of thiram is of great significance because the residue of thiram in agriculture has caused great contamination in environment and food, as well as threaten to the human health. Herein, we constructed a fluorometric strategy for on-site monitoring thiram via the aggregation-induced emission enhancement (AIEE) effect of glutathione-capped gold nanoclusters (GSH-AuNCs). The dissociated Ag+ ions can effectively enhance the fluorescent emission intensity of GSH-AuNCs at 570 nm owing to the AIEE phenomenon. Upon the addition of thiram, the fluorescence enhancement effect was weakened due to the strong coordinative interaction between Ag+ and thiram. By monitoring the signal change, the thiram residues were quantitatively analyzed with the detection limit of 0.05 μg mL-1. Notably, a home-made electronic-eye (E-eye) system, containing of a test-strip and a smartphone, was constructed as a portable platform to recognize and quantitatively analyze thiram in 10 min on the basis of captured fluorescence signals from a test strip with immobilized probe by direct photographing, which provides a direct quantitative tool to identify pesticide. Taking advantage of user-friendliness, portability and simplicity, the E-eye system are expected to fulfill the demand for quantitative on-site testing of pesticide especially in resource-limited areas.Graphical Graphical abstract for this article
       
  • The optical properties of 9-amino-9H-xanthene derivatives in different pH
           and their application for biomarkers in lysosome and mitochondria
    • Abstract: Publication date: Available online 31 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Xiao Guo, Xue-Rui Wei, Ru Sun, Yu-Jie Xu, Yuan Chen, Jian-Feng Ge Two xanthene compounds attached with 4-pyridinylimino (2a) and 2-quinolinylimino (2b) were prepared. Their deprotonated-protonated equilibrium between pyridine/quinoline/ xanthene units and the corresponding pyridinum/quinolinium/xanthylium units were evaluated in different pH by absorption and emission spectra. Probes 2a-b gave the colorimetric changes and emission responses at 550-750 nm, and their pKas (2a: pKa1 = 4.53, pKa2 = 5.95; 2b: pKa1 = 2.33, pKa2 = 6.18) were calculated by emission spectra. To verify the protonation process of probes 2a-b, the other two xanthylene derivatives attached with pyridinium (3a) and quinolinium (3b) were designed and synthesized; they exhibited only the equilibrium between xanthene and xanthylium as expected. Probe 3a showed a ratiometric change at 525 − 750 nm, and probe 3b displayed an OFF − ON emission at 500 − 700 nm with the decrease of the solution acidity. The calculated pKas were 6.18 and 1.49, respectively. Moreover, the fluorescent imaging experiments indicated that probes 2a − b were lysosome biomarkers while probes 3a − b were mitochondrial biomarkers for HeLa cells.Graphical abstractGraphical abstract for this article
       
  • Polypyyrole Based Core-Shell Structured Composite Based Humidity Sensor
           Operable at Room Temperature
    • Abstract: Publication date: Available online 31 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): B. Chethan, H.G. Raj Prakash, Y.T. Ravikiran, S.C. Vijayakumari, S. Thomas The present work explores the humidity sensing performance of core-shell structured Polypyrrole/Tantalum pentoxide (PTO) composite. For the study, Polypyrrole (PPy) prepared by chemical oxidative polymerization was mixed mechanically with different mass ratios of Tantalum pentoxide (Ta2O5) to form four PTO composites. The compositional properties of PTO composites were studied by FTIR and XRD techniques. The SEM and TEM morphological studies revealed core-shell structures of the composites. For the sensing studies, the film of PPy and each of PTO composites were prepared by implanting each sample on a glass plate using simple spin coating technique. Of all the samples prepared, the PTO-4 composite, as an epitome of near perfect sensing, has shown humidity sensing response of 99.99% and has recorded a good response and recovery times of 6 s and of 7 s respectively. It has also recorded a good real sensitivity, limit of detection (LOD), linearity, hystereses and has shown good sensing stability over a period of two months. As compared to PPy, the porosity, water content and degree of swelling of PTO-4 composite has remarkably enhanced. The humidity sensing mechanism of the composite has been discussed as due to the formation of chemisorption and physisorption layers followed by capillary condensation process.Graphical abstractGraphical abstract for this article
       
  • One pot synthesis of nanospheres-like trimetallic FeNiCo nanoalloy: A
           superior electrocatalyst for electrochemical sensing of hydrazine in water
           bodies
    • Abstract: Publication date: Available online 31 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Muthaiah Annalakshmi, Paramasivam Balasubramanian, Shen-Ming Chen, Tse-Wei Chen Present study reports a simple, low-cost, rapid electrochemical sensor for the detection of hydrazine (HY) using trimetallic NiFeCo (NFC) nanospheres as an excellent electrocatalyst. The electrode modifier NFC nanospheres were synthesized through one-pot, facile hydrothermal method. Transmission electron microscopic (TEM) results reveal that the nanoparticles are arranged in a well-defined homogeneous spherical in shape, without any agglomeration. It is undoubtfully found that NFC fabricated electrode demonstrated an admirable electrochemical sensing performance towards HY, which might be arise from its low impedance behavior, nanospheres-like architecture and synergic effect among the metallic nanoparticles. The developed electrochemical sensor presented the worthy analytical performance for HY sensing in terms of low detection limit (6.4 nM), wide dynamic range (0.020-3080 µM) and rapid response time (2 s). In addition, the proposed sensor can selectively detect the HY and easily discriminated HY from the possible interfering species. The practical applicability of the proposed novel HY sensor was successfully evaluated in real water samples such as river, lake, tap, and sewage water, achieved satisfactory recoveries with good precision and accuracy.Graphical abstractGraphical abstract for this article
       
  • Multimodal temperature sensing using Zn2GeO4:Mn2+ phosphor as highly
           sensitive luminescent thermometer
    • Abstract: Publication date: Available online 31 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Fengfeng Chi, Bin Jiang, Zhangmei Zhao, Yonghu Chen, Xiantao Wei, Changkui Duan, Min Yin, Wu Xu Motivated from increasing demands of non-contact temperature sensing, here Mn2+ doped Zn2GeO4 (ZGO) phosphor is produced to explore the temperature dependencies of its optical characteristics. Temperature dependencies of emission intensity and luminescence decay lifetime of Mn2+ in the range from 250 K to 420 K are investigated. The maximum relative sensitivities achieved are 4.5% K-1 and 4.6% K-1 for temperature sensing modes of emission intensity and decay lifetime, respectively. In order to realize temperature imaging, a temperature sensing scheme is employed based on time-resolved technique with the help of an intensified charge coupled device (ICCD) and a fluorescent microscope, where the luminescence integral intensities ratio of obtained images for two time segments is calibrated to measure the temperature. A maximum relative sensitivity of 12.2% K-1 is achieved and the best temperature resolution is about 0.68 K. Employing the temperature imaging system we built, the temperature distribution of micro circuit on a printed circuit board (PCB) has been monitored with high temperature and spatial resolution. The results may offer a significant advance in the development of temperature visualization for precise distributions and change of temperature field.
       
  • Surface Modification of Carbon Quantum Dots by Fluorescein Derivative for
           Dual-Emission Ratiometric Fluorescent Hypochlorite Biosensing and in Vivo
           Bioimaging
    • Abstract: Publication date: Available online 31 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Fanyong Yan, Zhangjun Bai, Tengchuang Ma, Xiaodong Sun, Fanlin Zu, Yunmei Luo, Liang Chen Surface modification of carbon quantum dots by fluorescein (FH-GA-CQDs) were synthesized for dual-emission ratiometric fluorescent ClO− biosensing and in vivo bioimaging. In the presence of ClO−, FH-GA-CQDs solution shows gradually decrease in the emission intensity at 413 nm and rapidly increase in the emission at 508 nm, corresponding to the blue-to-green emission color change. The detection mechanism is that the ClO− induces the ring-opening of FH units to form an oxadiazole structure, resulting in energy transferring from CQDs moiety to FH units. The energy transfer efficiency and energy transfer rate were estimated as 0.34 and 4.00 × 10-7 s-1, respectively. The results reveal that the FH-GA-CQDs have high sensitivity and selectivity for ClO− in the linear range extending from 0 to 70 μM with a detection limit as low as 93 nM. Meanwhile, the potency of the FH-GA-CQDs detecting ClO− in real water examples were validated by recoveries from 94% to 106% and semi-quantification determination of ClO− on fluorescent test strips. Most importantly, FH-GA-CQDs display low cytotoxicity and were successfully applied for sensing of ClO− in living cells and imaging of ClO− in nude mice.Graphical abstractGraphical abstract for this articleSurface Modification of Carbon Quantum Dots by Fluorescein Derivative for Dual-Emission Ratiometric Fluorescent Hypochlorite Biosensing and in Vivo Bioimaging.
       
  • Synthesis and characterization of different dopant (Ge, Nd, W)-doped ZnO
           nanorods and their CO2 gas sensing applications
    • Abstract: Publication date: Available online 31 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Hakan Çolak, Ercan Karaköse Undoped and Germanium (Ge), Neodymium (Nd) and Tungsten (W)-doped zinc oxide (ZnO) nanorods in powder form, which are needed for many technological applications, were synthesized. The synthesis procedure was performed through the mechanochemical combustion method using oxalic acid (H2C2O4) as a fuel at 600 °C. The XRD patterns of the ZnO samples were indexed in a hexagonal crystal structure. The solubility limits of Ge, Nd and W dopants in a ZnO lattice were found to be 3, 6 and 2 mol %, respectively. The morphological properties and existence of the dopants were investigated by SEM/EDS analysis. It was determined from the SEM analysis that the lengths of the nanorods were between 1-3 µm and their diameters were in the 50-100 nm range. The electrical conductivity measurements were determined under various temperatures and an air atmosphere via the four probe method. The conductivity values were found to slightly increase with increasing concentrations of the dopants. The sensing studies of the I-phase samples to CO2 gas under air and nitrogen atmospheres were performed in a sealed test chamber and the properties were examined as conductometric. The ZnO samples with different dopants were found to be more sensitive than the undoped ZnO under an air atmosphere. The CO2 gas response of the I-phase ZnO samples was low enough to be negligible under the nitrogen atmosphere when compared to the air atmosphere.
       
  • A novel peroxidase mimetic Co-MOF enhanced luminol chemiluminescence and
           its application in glucose sensing
    • Abstract: Publication date: Available online 31 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Dejian Li, Sisi Zhang, Xuan Feng, Hongjing Yang, Fei Nie, Wenyan Zhang In this work, a metal organic framework material ([Co(L)(H2O)2]n, Co-MOF) was synthesized by a facile hydrothermal method, and it was found that Co-MOF have a peroxidase-like activity. They can efficiently catalyze the chemiluminescence (CL) reaction between luminol and H2O2 and enhance the CL signal significantly. The possible enhancement mechanism suggested that Co-MOF catalyzed the decomposition of H2O2 into O2 and increased the generation of •O2−. Based on these findings, a new highly sensitive glucose sensor was constructed combined with the luminol-H2O2-Co-MOF CL system and glucose oxidase. Under the optimal conditions, the method exhibited a good linear response to glucose in the range of 0.04˜8 μM with a detection limit of 1 × 10-8 M. The method has been further applied in the quantitative determination of glucose in human serum and urine successfully.
       
  • Electrochemical Sensing of Lead in Drinking Water Using
           β-Cyclodextrin-Modified MWCNTs
    • Abstract: Publication date: Available online 30 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Arif Ul Alam, Matiar M.R. Howlader, Nan-Xing Hu, M. Jamal Deen A simple, facile and low-cost modification of multiwalled carbon nanotubes (MWCNT) with β-cyclodextrin (βCD) through a physical (Phys) and a covalent approach via Steglich esterification (SE) is demonstrated for the detection of lead (Pb). The Pb sensing performance is governed by the amount of βCD present in the MWCNT-βCD matrix and the physical/chemical attachment of βCD with MWCNT. The physically modified MWCNT-βCD based electrode showed high sensitivity of 98 nA/ppb with a limit of detection of 0.9 ppb but poorer reliability, whereas the chemically modified MWCNT-βCD electrode results in moderate sensitivity of 38.6 nA/ppb and a limit of detection of 2.3 ppb. The modified sensors showed reproducibility of more than 90% and reusability of at least six times. The proposed sensors offer a promising technology in developing a highly affordable and sensitive electrochemical sensing system for monitoring the Pb level in drinking water.Graphical Graphical abstract for this article
       
  • A glycine spacer improved peptidyl-nuclear-localized efficiency for
           fluorescent imaging nuclear H2O2
    • Abstract: Publication date: Available online 30 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Ying Wen, Fangjun Huo, Caixia Yin H2O2 generated aberrantly can attack DNA in nuclei and result in oxidative DNA damage, which has been associated with many serious diseases. Therefore, it is crucial to monitor nuclear H2O2 levels. However, the vast majority of fluorescence sensors can not localize in the nucleus. In the present study, we empolyed glycine (the simplest amino acids) as a spacer to lengthen distance between N50 and NP1. Cu2+-free click reaction (through inserting dibenzocyclooctyne-maleimide) was used to connect the two parts in situ. Three spacer sequences were tested: C, CGGGGG, and CGGGGGGGGGG, and three new NLS peptides (connection spacer sequence to N50) were generated: pep5, pep6 and pep7. The fluorescence imaging results showed the nucleus-targeting efficancy of the three peptides, especially pep6, were imporved. The calculated binding energies by molecular docking simulations with importin α5 (a member of importin) were pep6 < pep5 < pep7, consistent with the fluorescence imaging results. Importantly, the probe system consisting of pep6 and NP1 was used for imaging the increase of nuclear H2O2 level upon stimulation.Graphical abstractGraphical abstract for this articleThe statement: H2O2 generated aberrantly can attack DNA in nuclei and result in oxidative DNA damage, which has been associated with many serious diseases. Therefore, it is crucial to monitor nuclear H2O2 levels. However, the vast majority of fluorescence sensors can not localize in the nucleus. In the present study, we empolyed glycine (the simplest amino acids) as a spacer to lengthen distance between N50 and NP1. Cu2+-free click reaction (through inserting dibenzocyclooctyne-maleimide) was used to connect the two parts in situ. Three spacer sequences were tested: C, CGGGGG, and CGGGGGGGGGG, and three new NLS peptides (connection spacer sequence to N50) were generated: pep5, pep6 and pep7. The fluorescence imaging results showed the nucleus-targeting efficancy of the three peptides, especially pep6, were imporved. The calculated binding energies by molecular docking simulations with importin α5 (a member of importin) were pep6 < pep5 < pep7, consistent with the fluorescence imaging results. Importantly, the probe system consisting of pep6 and NP1 was used for imaging the increase of nuclear H2O2 level upon stimulation.
       
  • DNA-programming multicolor silver nanoclusters for sensitively
           simultaneous detection of two HIV DNAs
    • Abstract: Publication date: Available online 30 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Rong Zou, Feng Zhang, Chunyan Chen, Changqun Cai A novel DNA-stabilized silver nanoclusters (AgNCs)-based label-free fluorescent platform for simultaneously detecting two human immunodeficiency virus oligonucleotides (HIV DNAs) was developed. The sensing platform was established based on fluorescence enhancement of guanine (G)-rich and the phenomenon in the process of two silver nanoclusters (AgNCs) forming a nanoclusters dimer. The probe (AgNCs/G) utilized for HIV-1 detection adopted an effective conformation based on enhancement effect of G-rich sequence (at 500 nm ex / 565 nm em) while the probe (AgNCs/AgNCs) for HIV-2 generated fluorescence signals (at 580 nm ex / 630 nm em) with bright fluorescence only in nanoclusters dimer. The nanoprobe shows high selectivity for multiplexed analysis of target DNA with a detection limit of 11 pM, respectively. Moreover, this is the first time to use the affectivity of fluorescent AgNCs and two HIV DNAs simultaneous detection integrated into a novel method, which shows a great promise in biomedical research and early clinical diagnosis.Graphical abstractGraphical abstract for this articleSingle silver nanoclusters (AgNCs) had weaker fluorescence intensity. The green-emitting AgNCs (λex 500 nm / λem 565 nm) for HIV-1 detection produced strong fluorescence based on the enhanced effect of the G-rich sequence, while the orange-emitting AgNCs (λex 580 nm/λem 630 nm) for HIV-2 detection generated bright fluorescent signals only in the nanoclusters dimer. In the presence of HIV-1 and HIV-2, the structure of the high fluorescence effect is opened and the fluorescence intensity of both color AgNCs is lowered.
       
  • Highly Sensitive and Selective Gas-Phase Ethanolamine Sensor by Doping
           Sulfur into Nanostructured ZnO
    • Abstract: Publication date: Available online 30 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): He Zhang, Wenqiong Shi, Na Gao, Ruihua Zhao, Md. Maruf Ahmed, Tao Zhang, Jinping Li, Jianping Du, Tewodros Asefa The chronic and prolonged exposure to ethanolamine (EA), which is widely used in various commercial and industrial applications, can compromise human health and cause even death. Thus, sensors that can rapidly and efficiently detect EA in air, especially where EA is widely produced or used, is of paramount importance. Herein, we report the synthesis of sulfur-doped, flower-shaped ZnO (SFZO) microparticles that can serve as highly sensitive sensors for the detection of gas-phase EA. The materials are synthesized by a facile synthetic route, involving hydrolysis, precipitation and calcination. The composition, morphology and structure of the materials are characterized by various analytical techniques. The results show that, while the sulfur atoms introduced by substituting some of the oxygen atoms of ZnO do not change the morphology of the ZnO particles, they slightly affect the crystal structure, such as lattice parameters and cell volume, of ZnO, as also confirmed by DFT calculation. More importantly, the sulfur dopant atoms in ZnO create interstitial lattice defects and vacancies that can absorb O2 and form reactive oxygen species on the material better, thereby facilitating the reaction between oxygen and EA. As a result, SFZO-based sensor exhibits a very high sensitivity to EA, with a detection limit of up to 89 ppb and about four times higher sensitivity than its undoped counterpart (FZO-based sensor). SFZO-based sensor also shows a high selectivity to EA, a fast response time (1 s) and a fast recovery time (40 s) to various concentrations of gas phase EA at various temperatures. Additionally, the sensor exhibits a linear detection response with respect to the concentration of EA vapor in a wide concentration range, a property that is highly desirable in gas sensors.Graphical abstractGraphical abstract for this article
       
  • Turning toxic cigarette butt waste into the sensor material for the
           sensitive determination of antihypertensive drug trandolapril from its
           dosage form and biological samples
    • Abstract: Publication date: Available online 30 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Selva Bilge, Nurgul K. Bakirhan, Yusuf Osman Donar, Ali Sınağ, Sibel A Ozkan The findings of this study revealed that hydrothermal carbonization (HTC) of filter parts of smoked cigarette butts generates carbonaceous materials that have porosity and high surface area (1012 m2 g−1). This method is relatively eco-friendly because it performed in closed system and under mild conditions. In this study, porous carbon obtained from HTC of smoked cigarette filters was applied in an electroanalytical drug analysis. The surface morphology and chemical structure of the as-prepared materials were illuminated using with different techniques. The voltammetric behavior of antihypertensive drug trandolapril (TRD) was investigated on glassy carbon electrode (GCE) that modified by cigarette filter derived char/Nitrogen doped carbon spheres (c-char/NCS). The electrooxidation of TRD was demonstrated a diffusion-controlled fashion at pH 3.0 phosphate buffer (PB) solution. The calibration curve was linear between 8 × 10-8 and 8 × 10-5 M. The detection limit (LOD) was obtained as 1.09 × 10-10 M in pH 3.0 PB solution and 2.57 × 10-8 M in human serum samples by DPV. We try to show that the novel electrochemical sensor was easily applied for the determination of TRD using various carbon structures produced from urea and filter parts of cigarette butts.
       
  • Rapid visual identification of nitroaromatics compounds by
           aggregation-induced enhanced emission fluorescent assays with a
           Cd(II)-H3BTT complex
    • Abstract: Publication date: Available online 29 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yi Liu, Qi Zhang, Dong Jing, Xuan He, Sheng Cui, Yu Liu A new type of aggregation induced enhance emission (AIEE) active Cd(II) complex based on novel nitrogen-rich polycyclic ligand 4,5-bis(tetrazol-5-yl)-2H-1,2,3-triazole (H3BTT) and its metal organic gel (MOG) had been synthesized for the first time. The colloid of Cd(II)-H3BTT complex showed obvious AIEE characteristics in binary solvent system of DMF and ethanol, and displayed high sensitivity and selectivity for PA sensing over other nitroaromatics like DNB, TNB and TNT, where the limit of detection had been found as low as 9.3 × 10-7 M. Further, visual colorimetric recognition in colloidal state sensor and coated filter paper were all accomplished by spiking PA in tap water and river water. Interestingly, after being ripened, this colloid could be converted into stable MOG with the AIEE performance inherited, which also shown good fluorescence recognition ability and excellent reusability for the visual colorimetric PA detection. Surprisingly, we found that this gel could be reverse to colloidal state by simple ultrasound operation. And this regenerated colloid from the MOG storage for a period of time kept the same detection ability for PA as fresh colloid. Finally, the recognition mechanism of PA was confirmed as the counterion-displacement assays by FTIR and UV experiments. This novel Cd(II)-H3BTT complex provided a new insight into the design and synthesis of AIEE naked eyes recognized sensor for nitroaromatics with a simple and cheap preparation process, high sensitivity and stable storage.Graphical abstractGraphical abstract for this articleA new type of AIEE fluorescent colloid sensor based on Cd(II) complex with novel nitrogen-rich polycyclic ligand 4,5-bis(tetrazol-5-yl)-2H-1,2,3-triazole had been designed and synthesized successfully for the first time. Systematic study found that this novel long-time stable sensor have practical detection value for picric acid in fast and convenient naked eye recognition and high sensitive detection of natural samples.
       
  • Hydrogen sensing performance of a GaN-based Schottky diode with an H2O2
           treatment and electroless plating approach
    • Abstract: Publication date: Available online 29 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): I-Ping Liu, Ching-Hong Chang, Hsin-Hau Lu, Kun-Wei Lin   A new electroless plating (EP)-Pd/GaOx/GaN Schottky diode-type hydrogen sensor is fabricated and comprehensively studied herein. The GaOx dielectric is formed as a result of a proper H2O2 treatment on the GaN surface. In addition, a 20-period sensitization/activation process and an appropriate EP approach of the Pd catalytic layer are employed to facilitate a high-performance metal-semiconductor (M-S) Schottky contact. Experimentally, an extremely high hydrogen sensing response of 5.5 × 106 (under 1% H2/air gas) and a relatively low detection limit of 5 ppm H2/air are obtained at 300 K. The corresponding response and recovery times are 22 sec and 21 sec at 300 K, respectively. A new data transmission algorithm based on the Kalman algorithm is also proposed in this work. According to the simulation results, the data transmission volume can be reduced by 90%. The average recovery error rate is less than 0.38%. Furthermore, our developed reduced redundancy method can pre-warn the user of sensor failure. Based on the advantages mentioned above, therefore, the studied device is promising for high-performance hydrogen sensing and Internet of Things (IoT) applications.Graphical Graphical abstract for this article
       
  • Microfluidic multiple cross-correlated Coulter counter for improved
           particle size analysis
    • Abstract: Publication date: Available online 29 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Wenchang Zhang, Yuan Hu, Gihoon Choi, Shengfa Liang, Ming Liu, Weihua Guan Coulter counters (a.k.a. resistive pulse sensors) were widely used to measure the size of biological cells and colloidal particles. One of the important parameters of Coulter counters is its size discriminative capability. This work reports a multiple pore-based microfluidic Coulter counter for improved size differentiation in a mixed sample. When a single particle translocated across an array of sensing pores, multiple time-related resistive pulse signals were generated. Due to the time correlation of these resistive pulse signals, we found a multiple cross-correlation analysis (MCCA) could enhance the sizing signal-to-noise (SNR) ratio by a factor of n1/2, where n is the pore numbers in series. This proof-of-concept is experimentally validated with polystyrene beads as well as human red blood cells. We anticipate this method would be highly beneficial for applications where improved size differentiation is required.
       
  • Multi-barrel electrodes containing an internal micro-reference for the
           improved visualization of galvanic corrosion processes in magnesium-based
           materials using potentiometric scanning electrochemical microscopy
    • Abstract: Publication date: Available online 29 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Dániel Filotás, Bibiana María Fernández-Pérez, Lívia Nagy, Géza Nagy, Ricardo M. Souto Simultaneous monitoring of pH and Mg2+ distributions above AZ63 magnesium alloy, either spontaneously corroding or galvanically coupled with iron, was achieved using SECM in the potentiometric operation. By introducing an internal micro-reference electrode in a multi-barrel arrangement of the ion-selective microelectrode used as scanning probe, superior performance was achieved compared to conventional single-barrel and double-barrel assemblies. In this way, the impact of the overestimated acidification accompanying metal dissolution using conventional tips was established from model experiments using non ion-sensitive open micropipettes and pH antimony microelectrodes. It is shown that the simultaneously acquired pH and pMg maps provide complementary information on the spontaneous and galvanic corrosion of AZ63 magnesium alloy.Graphical abstractGraphical abstract for this article
       
  • An LTCC monolithic microreactor for the synthesis of carbon dots with
           photoluminescence imaging of the reaction progress
    • Abstract: Publication date: Available online 28 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): M. Berenguel-Alonso, I. Ortiz-Gómez, B. Fernández, P. Couceiro, J. Alonso-Chamarro, L.F. Capitán-Vallvey, A. Salinas-Castillo, M. Puyol This work describes the development of a fully integrated Low Temperature Co-fired Ceramic (LTCC) microreactor for the synthesis of carbon dots (CDots). The microreactor integrates fluidics, a heating resistor and an optical window for fluorescence imaging of the reaction progress in a monolithic, all ceramic device, ensuring homogeneous surface chemistry and physical properties. A pool of different CDots was synthesized at high temperature and pressure using a hydrothermal method, demonstrating the robustness of the microreactor. The synthesis was monitored by following the photoluminescence of the produced CDots, and the reaction conditions were optimized according to their Quantum Yield (QY) and the flow pattern inside the microchannel. The obtained CDots exhibited blue photoluminescence upon irradiation with UV light with QYs of up to 0.77. The CDots were screened as metal nanoprobes and bioimaging contrast agents.
       
  • Low-cost pencil graphite-based electrochemical detector for HPLC with
           near-coulometric efficiency
    • Abstract: Publication date: Available online 28 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Daniel Riman, Mamas I. Prodromidis, David Jirovsky, Jan Hrbac A concentric thin layer cell accommodating a non-standard 0.2 mm diameter pencil graphite disposable working electrode is described. The cell was installed into HPLC manifold as an electrochemical detector. Trouble-free operation in mobile phases containing both low and high content of organic solvents is demonstrated by HPLC analyses of phenolic acids and tocopherol isomers. The data obtained from HPLC separation of model mixtures of gentisic, caffeic and dihydrocaffeic acids show a remarkable electrolytic efficiency exceeding 80% at 200, and 50% at 500 μL min−1, while for gentisic acid the limit of detection (LOD) was 0.4 nmol L−1 at 20 microliter sample loading (8 fmol on-column). Similar performances were found in non-aqueous mobile phase, where a LOD of 0.8 nmol L−1 was achieved for delta-tocopherol. The developed flow-through detector is designed to allow easy replacement of pencil graphite working electrode in a highly reproducible manner. The relative standard deviation for the HPLC analysis of tocopherol isomers was of 5.3% (n = 3, C = 500 nmol L−1). The combination of simple construction, excellent electrochemical performance and hydrodynamics identical to that of commercial UV-VIS HPLC detector suggests that the proposed device is a viable low-cost alternative to commercially available electrochemical detectors.
       
  • The effect of operating conditions on the optically induced electrokinetic
           (OEK)-based manipulation of magnetic microbeads in a microfluidic system
    • Abstract: Publication date: Available online 27 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Jia-Long Hong, Chia-Ming Yang, Po-Yu Chu, Wen-Pin Chou, Chia-Jung Liao, Chia-Hsun Hsieh, Min-Hsien Wu, Ping-Hei Chen Magnetic microbeads are widely utilized in microfluidic systems for various applications. For these tasks, the effective and efficient manipulation of magnetic microbeads is important. Among the techniques for microparticle manipulation, the optically induced electrokinetic (OEK) [e.g., optically induced dielectrophoresis (ODEP) or light-actuated AC electroosmosis (LACE)]-based technique is promising. However, its utilization for magnetic microbead manipulation in a microfluidic system has not yet been fundamentally studied. To address this issue, the effect of operating conditions on the OEK-based magnetic microbead manipulation investigated. The results showed that the maximum terminal velocity (Vterminal) of a light image that can manipulate microbeads decreased significantly with increasing AC frequency. In addition, the results revealed that the Vterminal increased with increasing intrinsic a-Si:H layer thickness (Ta-Si) when the AC frequency was higher than 30 kHz, whereas the results completely reversed when the frequency was lower than 30 kHz. Additionally, the Vterminal of larger magnetic microbeads was higher than that of smaller microbeads when the AC frequency was higher than 50 kHz; conversely, the results significantly reversed when the frequency was lower than 30 kHz. Moreover, microbead manipulation under high conductivity conditions could significantly affect the magnitude of the Vterminal. Based on the fast manipulation velocity in LACE-based microbead manipulation, its application for basic unit operations in a microfluidic system was demonstrated. Overall, this study has provided some fundamental information for the selection of optimum operating conditions for OEK-based magnetic microbead manipulation in a microfluidic system.
       
  • Enhanced mass sensitivity in novel magnetoelastic resonator geometries for
           advanced detection systems
    • Abstract: Publication date: Available online 27 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Paula G. Saiz, David Gandia, Andoni Lasheras, Ariane Sagasti, Iban Quintana, María Luisa Fdez-Gubieda, Jon Gutiérrez, María Isabel Arriortua, Ana Catarina Lopes Acoustic wave based sensors have a major impact in the detection of low concentration of biological and chemical agents. Magnetoelastic resonator platforms are particularly interesting due to their low cost and wireless detection process. However, efforts in improving their performance are still focused only in the reduction of the size. In the present study, a new way to increase the sensitivity of magnetoelastic sensor platforms is proposed. This work demonstrates, both theoretically and experimentally, that the mass load sensitivity can be improved by tailoring sensor geometry and mass load position. Triangular and arched triangular shapes have been tested and compared with the traditional rectangular ones. It has been observed an increase in the mass sensitivity of more than 400% in Metglas 2826MB magnetoelastic sensor by using new sensor platform geometries. Even higher sensitivities have been obtained by doing partial coatings on the sensor edge/tip instead of the traditional complete uniform coating. New geometries present an increase up to 6400 % in partial coatings. The obtained results clearly show the key role of magnetoelastic resonator platforms geometries in the increase of mass load sensitivity and their importance in the draw of future labor-free and wireless sensors for low mass detection systems.Graphical abstractGraphical abstract for this article
       
  • Microscopic Model for pH Sensing Mechanism in Zinc-based Nanowalls
    • Abstract: Publication date: Available online 27 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): A. Scandurra, E. Bruno, G.G. Condorelli, M.G. Grimaldi, S. Mirabella Zinc based nanostructures are very promising material for pH sensing since they allow the realization of low-cost, sustainable, and high sensitivity electrodes. The pH sensitivity reported in literature for different ZnO nanostructures spreads from sub- to super-Nernstian, with the microscopic mechanism behind the H+ detection often unrevealed. In this work we synthesize by hydrothermal process and thermal annealing two zinc based nanowalls (NWLs) consisting of layered hydroxide zinc nitrate Zn5(OH)8(NO3)2·2H2O (as grown) and zinc oxide ZnO (annealed) phases, respectively. Scanning electron microscopy, micro Raman spectroscopy, X-ray photoemission spectroscopy were used to characterize the morphology and structure of NWLs. Electrochemical chronopotentiometric analysis in standard buffer solutions (pH 4 to 9) was used to study the response towards pH. Despite the two zinc based NWLs have the same morphology (interconnected sheets 10-20 nm thin, 1.4-1.7 μm wide), truly different behavior as pH sensitive electrodes are evidenced. As grown NWLs show a super-Nernstian response (+83.7 mV/decade), whereas annealed NWLs show a sub-Nernstian response (+27.1 mV/decade). The data are satisfactorily modeled by considering the crystallographic structures and assuming that layered hydroxide zinc nitrate NWLs is sensitive to only H+ (with two simultaneous and independent mechanisms), while zinc oxide NWLs is simultaneously and independently sensitive to both H+ and OH-. These data and the proposed modeling are useful to further develop the pH sensitivity of electrodes based on ZnO nanostructures.
       
  • In situ fabrication of CuO nanowire film for high-sensitive
           ascorbic acid recognition
    • Abstract: Publication date: Available online 26 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Qiannan You, Tao Liu, Jun Pang, Danfeng Jiang, Zhenyu Chu, Wanqin Jin One-dimensional metal oxides have been attracting interest as advanced materials for trace target recognition in chemical sensors due to their ultra-high surface area and electrochemical activity. However, the development of a large-scale and controllable fabrication strategy remains a great challenge and has hindered their practical application. In this work, we design a novel thermal oxidation route for obtaining a large area of CuO nanowires by the use of a film precursor of the nanocubic Cu-Fe Prussian blue analogue (PBA). The nanostructure and distribution of the PBA film was precisely controlled using an electrostatic self-assembly approach. The CuO nanowire shape was formed in-situ via the growth confinement effect through the air-heating collapse and oxidation of PBA crystals. At a very low working potential of 0.1 V, the as-prepared CuO nanowire sensor exhibited excellent sensing performance on ascorbic acid over a wide linear range (20–400 μM) and a low detection limit (0.5 μM), as well as high selectivity despite various interferences.
       
  • Enhancing the sensitivity of ion mobility spectrometry using the ion
           enrichment effect of non-uniform electrostatic field
    • Abstract: Publication date: Available online 25 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Chuang Chen, Hong Chen, Dandan Jiang, Mei Li, Wei Huang, Haiyang Li The diversified applications of ion mobility spectrometry (IMS) frequently pose challenges to the sensitivity of IMS measurements. In this work, the ion density evolution profiles of a continuous flow of ions travelling in non-uniform electrostatic fields were studied. Based on that, an ion enrichment method was proposed for enhancing the sensitivity of IMS. It employed a gradually weakening electrostatic field in the ionization region of IMS and achieved ion density enhancement for the ion flow migrating from the ion source to the ion shutter. Using that method, the ion density of the ion flow produced by the ion source was increased by 180% when approaching the ion shutter. With the increased ion density, the limit of detection (LOD) for DMMP dimer peak was lowered from 425 pptv to 200 pptv. Meanwhile, there was a slight reduction in the resolving power, which was tentatively assigned to the enhanced coulomb repulsion along with the increased ion density. The resolving power of the IMS with a drift length of 60 mm was still maintained around 80 at 100 degrees Celsius. The ion enrichment method needs no radial-confining radio frequency voltage. Also, it does not affect the response speed of IMS.
       
  • Trace detection of impurity phase in preparation of ye'elimite by Eu3+
           fluorescence prober
    • Abstract: Publication date: Available online 25 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Shuxian Wang, Shuxin Liu, Jinpu Zhang, Zhengmao Ye, Xin Cheng Ye'elimite (Ca4Al6SO16) is an important component in calcium sulfoaluminate cement. The formation of Ca4Al6SO16 belongs to a complex multiphase reaction, and many aluminate impurity phases might be generated in the reaction process. Trace impurity phase (below 1 wt. %) would seriously influence the hydration mechanism of Ca4Al6SO16, and the overlap of diffraction data between Ca4Al6SO16 and associated impurity phases is not conductive to the identification of contained impurity phases. In this study, based on the phase transition of Ca4Al6SO16 from the low-temperature orthorhombic phase (o-Ca4Al6SO16) to high-temperature cubic phase (c-Ca4Al6SO16), the existent impurity phase in o-Ca4Al6SO16 with excess addition of CaSO4 is verified as Ca3Al2O6 rather than Ca12Al14O33 with the closest Ca/Al ratio to the main phase. Meanwhile, the Eu3+ fluorescence prober shows a more sensitive detection capability than x-ray powder diffraction, especially when the content of Ca3Al2O6 below 2 wt. %. By virtue of the different crystal-field splittings of Eu3+ ions in o-Ca4Al6SO16 and Ca3Al2O6, the near-pure o-Ca4Al6SO16 phase with not more than 0.03 wt. % of Ca3Al2O6 is also obtained. In addition, combining the spectral analysis and structural refinement, the relationship between the content of Ca3Al2O6 and spectral change of Eu3+ ions are determined, and the obtained results show good linear change rules. As a result, what discussed in this research not only facilitates the verification and content determination of impurity phases in the preparation of Ca4Al6SO16, but also provides a promising strategy of phase identification through a combination of the phase-change structural analysis and lanthanide-doped fluorescence prober.
       
  • Surfactant modulation effect on the fluorescence emission of a
           dual-fluorophore: Realizing a single discriminative sensor for identifying
           different proteins in aqueous solutions
    • Abstract: Publication date: Available online 24 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yu Bo, Junmei Fan, Sisi Yan, Min Ding, Jing Liu, Junxia Peng, Liping Ding A bispyrene-modified perylene derivative (PEPBI), in which the pyrene and the perylenebisimide were connected by a hydrophilic oligoethoxy linker, was designed and synthesized. The absorption spectra and emission spectra revealed that PEPBI has the characteristics of both pyrene and perylene units. The cationic surfactant cetyltrimethylammonium bromide (CTAB) can efficiently regulate the fluorescence emission of PEPBI from pyrene monomer to pyrene monomer-perylene co-emission in aqueous solution. The selected fluorescent ensemble based on PEPBI/CTAB assembly showed ratiometric responses to nonmetalloproteins and turn-off responses to metalloproteins. Collecting the data of fluorescence variation of both pyrene and perylene units at six wavelengths can form specific recognition fingerprints for both nonmetalloproteins and metalloproteins. Using linear discriminant analysis, the sensor ensemble can discriminate four nonmetalloproteins and four metalloproteins. In this work, the combination of surfactant assemblies’ modulation effect and a dual-fluorophore with multiple emission bands realizes the discrimination of same type of proteins by a single sensor system.Graphical abstractGraphical abstract for this articleA dual-fluorophore modulated by surfactant assemblies to realize single system with pattern recognition ability for recognizing proteins
       
  • Highly Transparent, Stretchable, and Rapid Self-Healing Polyvinyl
           Alcohol/Cellulose Nanofibril Hydrogel Sensors for Sensitive Pressure
           Sensing and Human Motion Detection
    • Abstract: Publication date: Available online 24 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Xin Jing, Heng Li, Hao-Yang Mi, Yue-Jun Liu, Pei-Yong Feng, Yi-Min Tan, Lih-Sheng Turng Wearable sensors have emerged as favored novel devices for human healthcare. Current sensors, however, suffer from low sensitivity, non-transparency, and lack of self-healing ability. In this study, we synthesized a polyvinyl alcohol/cellulose nanofibril (PVA/CNF) hydrogel with dual-crosslinked networks for highly transparent, stretchable, and self-healing pressure and strain sensors. The hydrogel contains dynamic borate bonds, metal–carboxylate coordination bonds, and hydrogen bonds, all of which contribute to the hydrogel’s superior dimensional stability, mechanical strength and flexibility, and spontaneous self-healing ability as compared to traditional PVA hydrogels. The developed hydrogel has a moderate modulus of 11.2 kPa, and a high elongation rate of 1900%. It spontaneously self-heals within 15 s upon contact without any external stimuli, has a high transmittance of over 90%, and has excellent compatibility with human fibroblasts. The capacitive sensor developed based on the PVA/CNF hydrogel has high sensitivity to very subtle pressure changes, such as small water droplets. When used as a strain sensor, it was capable of detecting and monitoring various human motions such as finger, knee, elbow, and head movements, breathing, and gentle tapping. The developed hydrogel and sensors not only show great potential in electronic skin, personal healthcare, and wearable devices, but may also inspire the development of transparent, intelligent skin-like sensors.Graphical abstractGraphical abstract for this article
       
  • Conduction Mechanisms in One Dimensional Core-Shell Nanostructures for Gas
           Sensing: A Review
    • Abstract: Publication date: Available online 24 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Priyanka Karnati, Sheikh Akbar, Patricia A. Morris Metal oxide based core-shell (C-S) nanostructures have been studied for gas sensing applications to mitigate poor selectivity. When designing core-shell nanostructures with n-n, p-n and n-p junctions, an equalization of the Fermi level induces the formation of accumulation and depletion layers at the interface through charge, modifying the conduction channel. Mechanisms such as potential barrier carrier transport and surface depletion layer formation play important roles in enhancing the gas sensing performance of C-S nanostructures. Synthesis of C-S nanostructures is a multi-step process involving fabrication of core and shell layers. Selection of the core and the shell material is important as it would affect the properties of the heterojunction interface. Parameters such as the thickness of the shell layer, type of sensing material and working temperature have been studied for C-S nanostructure based gas sensors. However, less attention has been given to factors affecting the conduction mechanisms in C-S nanostructures. This review deals with understanding conduction mechanisms in one dimensional C-S nanostructures used for gas sensing applications, studying them based on synthesis methods used for fabrication and selection of materials used for core and shell layers.
       
  • Ultrasensitive electrochemical biosensor of interferon-gamma based on gold
           nanoclusters-graphene@zeolitic imidazolate framework-8 and
           layered-branched hybridization chain reaction
    • Abstract: Publication date: Available online 24 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Ting Bao, Meiqi Wen, Wei Wen, Xiuhua Zhang, Shengfu Wang In this work, a novel electrochemical biosensor was constructed for ultrasensitive interferon-gamma (IFN-γ) detection based on graphene@zeolitic imidazolate framework-8 hybrids anchored gold nanoclusters (AuNCs-GR@ZIF-8) and hemin/G-quadruplex DNAzyme decorated layered-branched hybridization chain reaction (LB-HCR). The two-dimensional GR@ZIF-8 hybrids were utilized as template to anchor AuNCs through a sequential deposition method. On the AuNCs-GR@ZIF-8 platform, an improved and efficient LB-HCR pattern was designed on the strength of traditional HCR with the cascade-like assembly of four hairpins. In which, HP1 and HP2 participated in traditional HCR process to form long double-helix DNA, AD1 and AD2 assembled alternately to facilitate the layerly chain-branching growth of DNA nanostructures. The target-triggered LB-HCR resulted in the generation of dendritic DNA nanostructures integrated with numerous in-situ formed hemin/G quadruplex DNAzyme as amplifying labels, which catalyzed the reduction of H2O2 with thionine acted as the electron mediator to realize amplified signal output. This multiple-amplified strategy exhibited good analytical performance towards IFN-γ with a wide linear range form 1 fM to 50 pM and a low detection limit of 0.6 fM, holding promising application in disease diagnosis and monitoring.Graphical abstractGraphical abstract for this article
       
  • Liquid crystal-enabled protease inhibition assays developed in a
           millifluidic device
    • Abstract: Publication date: Available online 23 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Mahbuba Jannat, Kun-Lin Yang Protease inhibitors are essential drug molecules which can be used for treatments of protease-related diseases. Herein, we report an LC-based protease inhibition assay built inside a millifluidic device. This assay can be used to study the inhibition efficiency and reversibility of pefabloc (a serine protease inhibitor) against proteases. LC is employed for the detection of peptide fragments produced from protease activity inside the millifluidic device. LC gives a bright spot when the amount of peptide fragment exceeds a minimum value. By using this assay, we find that IC50 value of pefabloc for the immobilized protease is 0.45 mg/mL, which is lower than the IC50 value of pefabloc (0.90 mg/mL) obtained in a homogeneous assay. Moreover, proteases can be immobilized on the millifluidic device to build a heterogeneous protease assay. In this assay, pefabloc blocks the immobilized protease irreversibly after 60 min, which is longer than that in a homogenous protease assay. This reversibility study provides useful information about the transition period of pefabloc from reversible to irreversible inhibition. This protease inhibition assay is potentially useful for high throughput screening of unknown proteases and their inhibitor in a small sample volume. Moreover, this method can be used for dosage test of novel drug molecules which are protease inhibitors.
       
  • A cyanine dye-based fluorescent probe as indicator of copper clock
           reaction for tracing Cu2+-catalyzed oxidation of cysteine
    • Abstract: Publication date: Available online 23 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Jing Li, Junjie Ge, Zhijie Zhang, Jian Qiang, Tingwen Wei, Yahui Chen, Zhuoan Li, Fang Wang, Xiaoqiang Chen Using cyanine dye-coupling 2-pyridylmethyl chelating unit as fluorescent probe, we successfully developed an indicator of copper clock reaction to monitor the process of cysteine (Cys) oxidation. During the monitoring assay, the fluorescent changes reflected three sequential reaction and binding behaviors including oxidation of Cys, oxidation of Cu(I) and binding between Cu(II) and the oxidation product cystine (Cys-Cys). Because the different kinetic trajectories were obtained when used Cys, GSH and Hcy as the substrates, respectively, a new strategy for distinguishing Cys from GSH and Hcy was further developed using the cyanine dye-coupling Cu(II) complex.Graphical abstractGraphical abstract for this article
       
  • Gold nanoparticle-based plasmonic probe for selective recognition of
           adenosine
    • Abstract: Publication date: Available online 23 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Jianjun Du, Haoying Ge, Saran Long, Wen Sun, Jiangli Fan, Xiaojun Peng Adenosine, as an endogenous molecule in organisms, plays an essential role in biological processes. Here, a plasmonic probe, creatinine-Ag+/gold nanoparticle (AuNPs), is assembled for adenosine detection based on synergistic coordination on AuNPs. The A650 nm/520 nm values of AuNPs system change linearly with adenosine concentration over a range of 1.0–5.0 μM and the detection limits reached 45 nM. The adenosine detection is realized within 4 min. Furthermore, the quantitative detection of adenosine is realized by eyedropper (a function in Microsoft’s PowerPoint) for analyzing RGB value changes of colorimetric assay. Therefore, this sensor can provide accurate and rapid assay of adenosine in patients’ serum sample without complicated instrumentations.
       
  • New Three-component Conjugated Polymers and Their Application as Super
           Rapid-response Fluorescent Probe to DNT Vapor
    • Abstract: Publication date: Available online 23 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Guangjuan Liu, Alim Abdurahman, Zhaoxia Zhang, Yuting Feng, Feng Li, Ming Zhang Two novel three-component conjugated polymers, P1 and P2, composed of fluorene, carbazole and anthracene / pyrene units, were designed and synthesized. After optimizing the ratio of these three components, their spin-coating films were prepared and used to detect nitro explosives in vapor phase, which present almost instantaneous fluorescence quenching (
       
  • Characterization and Optimization of the H2 Sensing Performance
           of Pd Hollow Shells
    • Abstract: Publication date: Available online 23 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Xuefei Li, Tianlong Cao, Xuemin Zhang, Yanhua Sang, Liuqian Yang, Tieqiang Wang, Yunong Li, Liying Zhang, Lei Guo, Yu Fu In this paper, Pd hollow shells (HSs) are chemically prepared by depositing Pd on the surface of silica cores followed by a silica core etching process. The as-prepared Pd HSs are assembled on the interdigital electrode and used as hydrogen sensors. Upon exposure to H2, the gap size between HSs repeatedly decreases or increases in accordance with the volume expansion or shrink of the Pd HSs, resulting in a detectable resistance variation of the sensor. The sensing performances of Pd HSs are characterized and optimized. It is found the presence of polyvinylpyrrolidone during the Pd deposition process helps to generate robust and smooth Pd HSs, which is crucial to stable and repeatable hydrogen detection. In the meanwhile, in contrast to previous reports that focus on decreasing the feature size of Pd structures to achieve a faster and more sensitive response, we show herein increasing the particle size can improve the sensing performance of Pd HSs. In our experiment, Pd HSs with the largest particle size show the lowest limit of detection. We conclude that Pd HSs with larger particle size can generate more considerable volume expansion, which leads to more efficient tuning of the sensor’s electrical property at low H2 concentration.Graphical abstractGraphical abstract for this articlePd hollow shells show highly sensitive and reliable sensing performance when being used as HILE based H2 sensors.
       
  • A rational design of hollow nanocages Ag@CuO-TiO2 for enhanced acetone
           sensing performance
    • Abstract: Publication date: Available online 23 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Guangxia Wang, Ziyu Fu, Tianshuang Wang, Weiwei Lei, Peng Sun, Yongming Sui, Bo Zou Hollow nanostructured Ag@CuO-TiO2 was prepared by a facile hydrothermal method with high surface area and uniform catalyst functionalization. The obtaining of Ag@CuO-TiO2 multicomponent hollow nanocages was ascribed to the addition of TiF4, which serves as both the precursor of TiO2 and etching agent by releasing HF. In this process, Cu2O works as the self-template and the scaffold to induce and maintain the shape of hollow nanocages. Therefore, the formation of hollow structure and multicomponent heterostructures were accomplished without tedious processes and additional template. The deposition of TiO2 layer, anchored to the Ag@Cu2O surface, avoids the aggregation of p-type or n-type nanoparticles and ultimately formation of p–p junctions or n–n junctions, which would be valuable in terms of reproducibility and scalable production. The numerous heterojunctions of CuO-TiO2, well-dispersed nanoscale Ag catalysts and hollow nanocage structures are favorable for the development of high-performance gas sensors. The desired Ag@CuO-TiO2 hollow nanocages were investigated for response to various target gases, which showed a superior sensing performance towards acetone. The improved sensing properties might be ascribed to the synergistic effects of both hollow structure and different nanocomponents.Graphical abstractGraphical abstract for this articleRational designed Ag@CuO-TiO2 multi-components hollow nanocages exhibited improved sensor performances for acetone.
       
  • Two-photon fluorescence probes for mitochondria imaging and detection of
           sulfite/bisulfite in living cells
    • Abstract: Publication date: Available online 23 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Kang-Nan Wang, Yilin Zhu, Miaomiao Xing, Duxia Cao, Ruifang Guan, Songfang Zhao, Zhiqiang Liu, Zong-Wan Mao Sulfur dioxide derivatives, i.e., sulfite (SO32-) and bisulfite (HSO3-) play important roles in numerous physiologically essential processes of living systems. SO32- and HSO3- with abnormal levels have close relation with many diseases including acute symptoms of respiratory disease, cardiovascular disease, cancer and neurological disorder. Herein, we presented two new two-photon fluorescence probes based on diethylaminecoumarin skeleton with pyridinum (1-[2-(7-Diethylamino-2-oxo-2H-chromen-3-yl)-2-oxo-ethyl]-pyridinium; bromide, C-Py) and imidazole (1-[2-(7-Diethylamino-2-oxo-2H-chromen-3-yl)-2-oxo-ethyl]-3-methyl-3H-imidazol-1-ium; bromide, C-Im) as terminal group. The probes showed highly sensitive and selective response to sulfite/bisulfite on the basis of intermolecular hydrogen bonding action between methylene and sulfite/bisulfite. The probes have excellent cell permeability, and a series of uptake inhibition experiments suggested that the probes possibly enter cells through an energy-dependent pathway and endocytosis is impossible to be responsible for cell-membrane penetration process. The probes could specifically target mitochondria by two-photon imaging in living cells, and exhibit nearly no mitochondrial membrane potential damage. Moreover, the probes could be successfully applied for two-photon imaging of mitochondial SO32- and HSO3- in living cells. Negligible cytotoxicity, high mitochondrion selectivity, good recognition properties to sulfite/bisulfite, good cellular uptake and cell membrane penetration will allow them to find valuable application in biomedical research field for sulfite/bisulfite detection.Graphical abstractGraphical abstract for this article
       
  • Oxygen vacancies dominated CuO@ZnFe2O4 yolk-shell microspheres for robust
           and selective detection of xylene
    • Abstract: Publication date: Available online 22 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Nan Zhang, Shengping Ruan, Jing Han, Yanyang Yin, Xin Li, Caixia Liu, Samira Adimi, Shanpeng Wen, Yang Xu Hierarchical ZnFe2O4 yolk-shell microspheres (ZFO YSMSs) with the large specific surface area are synthesized using a facile self-template strategy followed by a thermal treatment method. Subsequently, different amounts of CuO are decorated on ZnFe2O4 YSMSs (CZFO YSMSs) via a simple solvothermal method. Various techniques are employed to study the microstructure, morphology, chemical composition, oxidation states and surface area of ZFO and CZFO YSMSs, including XRD, SEM, TEM, XPS and BET analysis. The crystallite sizes, pore diameters and grain diameters of the ZFO and CZFO3 YSMSs are calculated statistically, and their sensing performances are investigated systematically, including optimum operating temperature, selectivity, response/recovery time, detection limit and long-term stability. The experimental results indicate the CZFO YSMSs-based sensor shows remarkable selectivity (e.g., Sxylene/Stoluene =3.21) as well as good sensitivity to xylene. The improved sensing properties could be ascribed to the catalytic action of CuO for the oxidation of xylene and the increase of absorbed oxygen species caused by oxygen vacancies (Ov).
       
  • Effective design and fabrication of low-power-consumption self-heated SnO2
           nanowire sensors for reducing gases
    • Abstract: Publication date: Available online 22 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Trinh Minh Ngoc, Nguyen Van Duy, Nguyen Duc Hoa, Chu Manh Hung, Hugo Nguyen, Nguyen Van Hieu Developing metal oxide gas sensors for internet-of-things (IoT) and portable applications require low-power consumption because of the limited battery in devices. This requirement is challenging because metal oxide sensors generally need high working temperatures, especially for reducing gases. Herein, we present an effective design and fabrication method of a SnO2 nanowire (NW) sensor for reducing gases by using the Joule heating effect at NW nanojunctions without needing an external or integrated heater. The sensor’s low-power consumption at around 4 mW was controlled by the size and nanojunction density of the device. The sensor has a simple design and is easy to fabricate. A proof-of-concept of a portable gas sensor module can be realised for monitoring highly toxic reducing gases, such as H2S, NH3 and C2H5OH, by using the developed self-heated NWs.
       
  • Belousov-Zhabotinsky liquid marbles in robot control
    • Abstract: Publication date: Available online 22 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Michail-Antisthenis Tsompanas, Claire Fullarton, Andrew Adamatzky We show how to control the movement of a wheeled robot using on-board liquid marbles made of Belousov-Zhabotinsky solution droplets coated with polyethylene powder. Two stainless steel, iridium coated electrodes were inserted in a marble and the electrical potential recorded was used to control the robot's motor. We stimulated the marble with a laser beam. It responded to the stimulation by pronounced changes in the electrical potential output. The electrical output was detected by the robot. The robot changed its trajectory in response to the stimulation. The results open new horizons for applications using oscillatory chemical reactions in robotics.Graphical abstractGraphical abstract for this article
       
  • An accurate and versatile density measurement device: Magnetic Levitation
    • Abstract: Publication date: Available online 22 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Jun Xie, Chengqian Zhang, Fu Gu, Yunming Wang, Jianzhong Fu, Peng Zhao This study presents a magnetic levitation device for measuring density with high accuracy and versatility, and of low cost. Samples that are immersed in paramagnetic medium can be levitated at some equilibrium positions between two identical NdFeB magnets with like-poles facing each other. The method measures density without acquiring the sample’s volume, therefore it can be used to deal with tiny particles (
       
  • Molecularly imprinted conducting polymer for determination of a condensed
           lignin marker
    • Abstract: Publication date: Available online 21 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Alvaro Gonzalez-Vogel, Anna Fogde, Claudia Crestini, Thomas Sandberg, Tan-Phat Huynh, Johan Bobacka Condensed lignin is an undesired byproduct that has detrimental effects in cellulose pulping processes, increasing the consumption of bleaching chemicals and altering the properties of main products. A simple method for quantification of condensed lignin could greatly improve the performance and economy of pulping mills. In this work, a chemical sensing material based on a molecularly imprinted conducting polymer was synthesized by using a marker of condensed lignin as template molecule. Molecular modeling was used as an essential tool to understand and optimize the complexation of the functional monomers with the template in order to improve the synthesis strategy compared to previous imprinting methods. The imprinted polymer was synthesized by co-electropolymerization of 3,4-ethylenedioxythiophene (EDOT) and 3-acetic acid thiophene (AAT) in presence of 2,2’-methylenebis(2-methoxy-4-methylphenol) as template, and studied by cyclic voltammetry and electrochemical impedance spectroscopy. The anodic peak current at +0.88 V (vs. Ag/AgCl/KCl 3 M) in the cyclic voltammograms of the imprinted polymer sensor was used to detect the lignin marker dissolved in pure solvents at concentrations ranging from 1 × 10-6 to 1 × 10-2 M.Graphical abstractGraphical abstract for this article
       
  • Transistor-based immunosensing in human serum samples without on-site
           calibration
    • Abstract: Publication date: Available online 21 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Óscar Gutiérrez-Sanz, Natalie Haustein, Michele Schroeter, Tobias Oelschlaegel, Marcin S. Filipiak, Alexey Tarasov Health monitoring and disease diagnostics are increasingly moving away from central laboratories towards the point of need. Despite tremendous progress in transducer research, the general need for sample preparation and calibration has impeded wide-spread adoption of new biosensor technologies. In this work, we realize an on-site calibration-free biosensor by using “differential” readout of pairs of differently functionalized field-effect transistors (FET). Specifically, biosensor 1 carries capture antibodies for the target of interest while biosensor 2 is passivated with a blocking agent. We found that their real-time signal difference is largely unaffected by non-specific binding, drift or device-to-device variations. Using this system, highly sensitive detection of a clinically relevant model antigen, thyroid-stimulating hormone, is demonstrated. The sensors are validated in human serum samples vs. a state-of-the-art central laboratory analyzer. The FET-based platform reaches over 4 orders of magnitude dynamic range with a sub-picomolar lower detection limit and an upper detection limit superior to the state-of-the-art system (>10 nM vs. ˜0.1 nM). In contrast to existing technology, the FET sensors do not require any expensive optical components, labelled detection antibodies, sample pre-treatment or washing steps, and remove the need for sensor calibration. These results represent a critical step towards clinical testing outside the centralized lab.
       
  • The construction of electrochemical aptasensor based on coral-like
           poly-aniline and Au nano-particles for the sensitive detection of Prostate
           Specific Antigen
    • Abstract: Publication date: Available online 21 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Zhenjiang Li, Jifang Yin, Chenghai Gao, Guanhao Qiu, Alan Meng, Qingdang Li Prostate specific antigen (PSA), as the significant biomarker of prostate cancer, has aroused widespread concern. However, constructing the PSA aptasensor with high sensitivity and low detection limit is still facing huge challenges. In this study, a sensitive electrochemical aptasensor for detecting PSA based on coral-like poly-aniline (PANI)/gold nano-particles (AuNPs) and the peptides was constructed. Coral-like PANI and AuNPs with the diameter of 50-80 nm, as the substrate materials, were directly deposited on glass carbon electrode (GCE) by electrodeposited method. Then, the peptides, as the antifouling materials, were anchored on the modified-electrode, which not only can form antifouling surface to reduce nonspecific adsorption, but also can be as a medium between the modified-electrode and PSA aptamer. Finally, the PSA aptamer was immobilized on the electrode. Based on the synergistic effect of excellent conductivity and special morphology of the substrate materials, and the antifouling ability of peptides, the aptasensor exhibited a high sensitivity of 462.7 μA·(ng mL-1)-1 cm−2, wide linear range from 0.1 pg mL-1 to 100 ng mL-1, low limit of detection (LOD) of 0.085 pg mL-1 and good antifouling performance. The aptasensor also possessed outstanding selectivity, reproducibility and stability. Moreover, the aptasensor can directly detect PSA in 10% human serum solutions.
       
  • Low-cost quartz tuning fork based methane sensor for coal mine safety
           applications
    • Abstract: Publication date: Available online 19 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Xiaoyu Chen, Xiaoce Feng, Xiaojun Liu, Xiangqun Zeng, Yong Xu This paper reports a simple but effective methane sensor based on off-the-shelf quartz tuning forks (QTFs). The operation of the sensor is based on the fact that the presence of methane will increase QTF’s resonant frequency since methane is lighter and less viscous than air. Unlike other resonant gas sensors based on the gravimetric principle, this new QTF sensor is not coated with any sensitive layer to absorb methane molecules, thus minimizing the hysteresis, reducing response and recovery time, and potentially improving long-term stability. It has been experimentally demonstrated that the presence of methane increases the resonant frequency of QTF with a sensitivity of 0.0063 Hz/1% or 0.19 ppm/1% and a detection limit of 0.025% at 0.5 Hz sampling rate. An excellent selectivity to carbon dioxide, which causes a decrease of the resonant frequency, has been illustrated. Temperature, pressure and humidity responses have been characterized. This new methane sensor is expected to meet the requirements of cost, power, size, reliability and explosion permissibility for coal mine safety applications.
       
  • A flexible NO2 gas sensor based on polypyrrole/nitrogen-doped multiwall
           carbon nanotube operating at room temperature
    • Abstract: Publication date: Available online 19 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Bohao Liu, Xueyan Liu, Zhen Yuan, Yadong Jiang, Yuanjie Su, Jinyi Ma, Huiling Tai A flexible NO2 gas sensor based on a polypyrrole/nitrogen-doped multi-walled carbon nanotube (PPy/N-MWCNT) composite film was successfully prepared on PI substrates using a combined in situ self-assembly and annealing treatment method. After annealing at 350 °C, the gas sensor exhibited a high response of 24.82% ((Rg−Ra)/Ra×100%) under 5 ppm of NO2, which is 44.12 times greater than that of the unannealed sensor. The PPy/N-MWCNT gas sensor exhibited excellent repeatability, remarkable selectivity, good long-term stability, and acceptable flexibility. Furthermore, the effect of the relative humidity on the gas sensing properties was examined. The excellent gas sensing performances of the sensor were attributed to the enriched adsorption sites due to degradation of the amount of stacked PPy structures on the surface of the N-MWCNTs after the annealing treatment. The results demonstrated that PPy/N-MWCNT composite films are highly promising for potential applications in the field of NO2 gas sensing.
       
  • Turn-on fluorescence detection of β-glucuronidase using RhB@MOF-5 as an
           ultrasensitive nanoprobe
    • Abstract: Publication date: Available online 19 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Lan Guo, Yuan Liu, Rongmei Kong, Guang Chen, Hao Wang, Xiuli Wang, Lian Xia, Fengli Qu β-Glucuronidase (β-GCU) is closely related to the occurrence of multiple diseases, and it has been applied as a biomarker and therapeutic target in clinical diagnosis. However, reliable methods with high selectivity and sensitivity for monitoring β-GCU are still lacked. Herein, we designed a novel fluorescent nanoprobe, rhodamine B encapsulated MOF-5 (RhB@MOF-5) for the first time, to detect β-GCU through the synergistic effect of inner filter effect (IFE) and static quenching effect (SQE) by employing 4-nitrophenyl-β-D-glucuronide (PNPG) as the substrate. After encapsulating into MOF-5, the fluorescence emission of RhB at 550 nm excited by 320 nm was greatly enhanced. The major overlap between the fluorescence excitation spectrum of RhB@MOF-5 (about 320 nm) and the ultraviolet absorption spectrum of PNPG (about 310 nm) lead to PNPG being a good IFE absorber in this sensing system. Under the optimized conditions, the excitation spectrum of the RhB@MOF-5 could be absorbed by PNPG, resulting in the dramatically decrease of fluorescence emission. After adding β-GCU into the system, the substrate of PNPG would be enzymatic hydrolyzed to p-nitrophenol (PNP) and glucose, then the IFE disappearance and the fluorescence recovered. The current sensing platform was interference-free and exhibited a broad linearity relationship for β-GCU range of 0.1-10 U L-1 (R2 = 0.9957) with a limit of detection as low as 0.03 U L-1, which was reduced by more than one orders compared with the reported methods. Moreover, the encapsulation of dyes using porous nanoparticles to achieve some tailor-made characteristics will enrich experimental design inspiration.Graphical abstractGraphical abstract for this article
       
  • NASICON-based gas sensor utilizing MMnO3 (M: Gd, Sm, La) sensing electrode
           for triethylamine detection
    • Abstract: Publication date: Available online 18 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yueying Zhang, Ce Ma, Xinyu Yang, Yang Song, Xishuang Liang, Xu Zhao, Yilin Wang, Yuan Gao, Fengmin Liu, Fangmeng Liu, Peng Sun, Geyu Lu In this work, the mixed-potential-type gas sensor based on NASICON solid electrolyte and MMnO3 (M: Gd, Sm, La) sensing electrode (SE) was developed and fabricated aiming at the low-concentration triethylamine (TEA) detection. The research point of the fabricated sensors mainly concentrated on the effect of different A-site elements in MMnO3-SE (M: Gd, Sm, La) on TEA sensing characteristics. The result reveals that the highest response value (-217.5 mV) towards 50 ppm TEA was observed for the device utilizing SmMnO3-SE. The highest electrochemical catalytic activity of the fabricated sensors attached with SmMnO3-SE was further authenticated by the polarization curve measurement. Moreover, the response value displays a segmentally linear relationship with TEA concentrations and the logarithm of TEA concentrations, and the slopes are −49 mV/ppm and -105 mV/decade at the ranges of 0.05-0.5 ppm and 1-50 ppm TEA, respectively. The device could also produce an acceptable response value (-5.6 mV) towards 50 ppb TEA. Moreover, it also displays good repeatability and selectivity, along with steady response signals towards 5 ppm and 50 ppm TEA for 15 days and 1 ppm TEA at different humidity levels.
       
  • Response modeling of single SnO2 nanowire gas sensors
    • Abstract: Publication date: Available online 18 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Mohammad Zhian Asadzadeh, Anton Köck, Maxim Popov, Stephan Steinhauer, Jürgen Spitaler, Lorenz Romaner The response of single SnO2 nanowire gas sensors with different diameters between 20 and 140 nm are evaluated by calculating the nanowire conductivity as a function of the surface charge density. The procedure involves the numerical solution of the Poisson-Boltzmann equation for the electrostatic potential in cylindrical geometry in order to model the depletion region and band bending at the SnO2 nanowire surface. In the model we take into account varying surface charge densities σ and bulk electron concentrations n0 to calculate the electrical conductivity. Considering the fact that the surface charge density depends on the nanowire surface interactions with ambient gas, the model allows us to simulate the sensor response when the nanowire is employed as gas sensing component. We report a saturation in depletion length λ versus surface charge density σ which is the principal reason for limiting the sensor responses. The results also show that the conductivity is decreasing by increasing surface charge density, the smaller the nanowire diameter the steeper the decrease. As a result the nanowire response is proportional to 1/d where d is the nanowire diameter. Furthermore, we argue about the validity of the modeling results and their relevance to experimental findings on SnO2 nanowire based gas sensors reported in literature.
       
  • Humidity effects on the initial stabilization behavior of a solid
           electrochemical CO2 sensor
    • Abstract: Publication date: Available online 18 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Tae-Wan Kim, Jun-Woong Kim, Sang-Min Lee, Chong-Ook Park An electrochemical-type CO2 sensor using alkali carbonate as a sensing material was studied, along with its humidity disturbance effect during the initial stabilization stage. A sensor made of Na2CO3 (Cell A) and NaHCO3 (Cell B) sensing materials were tested from room temperature to 500 °C, step-by-step, at CO2 concentration of 500 ppm. The test was designed to investigate the difference in the initial stabilizing step between dry and humid conditions. After measuring the sensitivity of both Cell A and B, the NaHCO3 sensing material showed a sensitivity value similar to that of the Na2CO3 sensing material during operation at 500 °C. The thermodynamic calculation implied that the NaHCO3 that might be produced in humid air was considered the main source of sluggish behavior due to the decomposition of NaHCO3 to Na2CO3 at 250 °C. In addition, the electric potential calculation based on the chemical reaction of Cell A and Cell B was performed to compare the simulated model with the real behavior of the sensor.
       
  • Differentiation of heavy metal ions by fluorescent quantum dot sensor
           array in complicated samples
    • Abstract: Publication date: Available online 17 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Zhe Jiao, Pengfei Zhang, Hongwei Chen, Cong Li, Lina Chen, Hongbo Fan, Faliang Cheng The interference of co-existing substances often causes trouble in the analysis of trace metal ions in complex samples, even for highly selective sensors. For this reason, an instant and inexpensive fluorescence sensor array for discrimination of heavy metal ions in complex samples was developed. The sensor array was constructed using four kinds of Mn doped ZnS quantum dots (Mn: ZnS QDs), which were facilely modified with N-Acetyl-cysteine, citric acid, mercaptopropionic acid and triammonium-N-dithiocarboxyiminodiacetate, respectively. For each metal ion, quantitative calibration curves were obtained with the concentration level ranging from 10-100 pg/mL (R2> 0.96). Due to the different quenching effect for Cu, Hg, Ag and Cd on various QDs, the sensor array exhibited a unique pattern of fluorescence variations at a low concentration of 30 pg/mL and can be discriminated successfully by principal component analysis (PCA). The contribution of individual sensors within the array was demonstrated and the obtained information was used to design sensor arrays with two and three sensor elements. The sensor array was also applied to identify the metal ions in unknown mixtures, containing single, binary, ternary and quaternary constitutions. Linear discriminant analysis (LDA) showed that the samples could be well recognized and distinguished. The sensor array was finally applied in water samples with three different concentrations, indicating the co-existing substances rarely influenced discriminatory capacity of the sensor array. Compared to instrumental analysis, this fluorescence sensor array-based method has proven to be more convenient since the nanoparticles can be prepared flexibly according to the property of the target.Graphical Graphical abstract for this article
       
  • Precipitate-enhanced SAW immunosensor for sensitive monitoring of mite
           allergens
    • Abstract: Publication date: Available online 16 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Koji Toma, Koki Oishi, Misato Kato, Kanako Kurata, Naoyuki Yoshimura, Takahiro Arakawa, Hiromi Yatsuda, Kiyoko Kanamori, Kohji Mitsubayashi •Precipitates produced via horseradish peroxidase (HRP-) catalyzed reaction was exploited to enhance the sensitivity of a surface acoustic wave (SAW) immunosensor for monitoring airborne house dust mite (HDM) allergens. Three candidate substrates, 4-chloro-1-naphthol (4CN), 3,3′-diaminobenzidine (DAB) and 3,3',5,5'-tetramethylbenzidine (TMB), were systematically compared in terms of signal amplification and suitability to rapid and repeated measurement. Each substrate solution was applied to the sensor surface where group 2 HDM allergens of Dermatophagoides farinae (Der f 2) were sandwiched by capture and HRP-conjugated detection antibodies. The signal amplification and sensor regeneration rate were evaluated from the sensor output induced by precipitated product of HRP-catalyzed reaction and the sensor signal recovery after the regeneration via various pH reagents, respectively. As a result, it was revealed that 4CN showed the highest surface regeneration rate among the three substrates with use of NaOH adjusted to pH 13 as well as the second largest enhancement of the sensor output. Use of 4CN enabled to enhance the sensor output by a factor of 13 for 1 ng/mL Der f 2 with respect to that without the HRP-catalyzed reaction. The limit of detection of the precipitate-enhanced SAW immunosensor was 35 pg/mL (equivalent to 2.3 pM), which was 1.4-fold and 206-fold better than those of ELISA and the SAW immunosensor without a precipitate, respectively. These indicate that exploiting 4CN under the optimal conditions in the SAW immunosensor realizes ultra-sensitive monitoring of HDM allergens.Graphical Graphical abstract for this article
       
  • N-doped carbon dots with tunable emission for multifaceted application:
           solvatochromism, moisture sensing, pH sensing, and solid state multicolor
           lighting
    • Abstract: Publication date: Available online 13 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Md Moniruzzaman, Jongsung Kim Novel N-doped green-emitting carbon dots (N-GCDs) that were responsive to various external stimuli and had high quantum yields (QYs) for multifaceted applications were synthesized from β-resorcylic acid and ethylenediamine using a hydrothermal process followed by a reflux method. The QYs of the N-GCDs were in the range of 17.36%–48.4% and were associated with different photoluminescent color emission in different solvents. Interestingly, the as-synthesized N-GCDs exhibited strict solvent polarity-dependent switchability (solvatochromism) and multicolor excitation-wavelength-independent emission in different solvents. Sensing of an analyte based on the switching of the photoluminescence (PL) emission maxima (λmax) is always preferred over that based on fluorescence quenching to avoid complexity and confusion regarding the initial fluorescence intensity (I0) and thus make the sensing process simple, rapid, ordered, and reliable. The N-GCDs exhibited blue emission in low-polarity organic solvents, but with the increase of the trace water content in the system, the PL emission peak gradually shifted to a higher wavelength (bathochromic shift) at a single-wavelength excitation. Thus, the N-GCDs are sensitive visual probes for the fluorescence detection of the trace water content in organic solvents without sophisticated processes. They also indicate the pH-response behavior. When the pH decreased from 7.6 to 2.4, the fluorescence emission intensity decreased, with a particularly good linear relationship (R2 = 0.990) in the range of 3.8–6.2. Moreover, the polarity-dependent-emission property was observed in the solid state polymer matrices. Multicolor-emissive N-GCD/polymer films were prepared by integrating N-GCDs with the polymer matrices of different polarity, demonstrating the application of carbon dots for solid-state lighting.Graphical abstractGraphical abstract for this article
       
  • Superbright organosilica nanodots as a universal sensor for fast
           discrimination and accurate quantification of live/dead cells
    • Abstract: Publication date: Available online 13 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Xiaokai Chen, Xiaodong Zhang, Chengcheng Li, Sayed Mir Sayed, Wei Sun, Fengming Lin, Fu-Gen WuABSTRACTRapid and quantitative discrimination between live and dead cells is highly desirable yet remains a challenging task. Here, we report the use of the ultrabright green-emitting organosilica nanodots (OSiNDs, photoluminescence quantum yield: ˜100%) for fast (1 min in vitro and 5 min in vivo), wash-free, and universal labeling of the dead bacterial, fungal, and mammalian cells, which meet the demand of the green fluorescent probes that can specifically image the dead cells. The photostability of OSiNDs surpasses that of the commercial dyes, such as propidium iodide (PI) and SYTOX green nucleic acid stain (SYTOX), making OSiNDs more suitable for long-term and stable monitoring of the cell viability. With the assistance of a commercial red fluorescent dye SYTO 60, we have developed an in situ method for rapid and accurate quantification of live/dead cells. Motivated by the unique optical advantages and high sensitivity of OSiNDs to the cell viability, the OSiNDs were used to observe the in vivo cellular changes induced by a model drug doxorubicin, demonstrating their great potential for evaluating the toxicity/efficacy of the therapeutic agents in real time. Owing to the excellent biocompatibility and low cost, the OSiNDs can be a universal probe for efficient and accurate differentiation and quantification of the live and dead cells, which may find wide applications in the biomedical field.Graphical abstractGraphical abstract for this article
       
  • A fluorescent probe for the dicriminatory detecion of Cys/Hcy, GSH and H2S
           in living cells and zebrafish
    • Abstract: Publication date: Available online 7 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Fengpei Qi, Yun Zhang, Benhua Wang, Wenqiang Chen, Lei Yang, Zhaoguang Yang, Xiangzhi Song Biothiols such as Cys, Hcy, GSH, and H2S are a critical branch of reactive sulfur species (RSS) and play indispensable roles in human physiological processes. To better understand the intricate and symbiotic networks between these biothiols in physiological processes, single-molecule fluorescent probes to simultaneously distinguish them are highly desirable. Herein, we judiciously conjugated an azide-functionalized tetrahydroquinoxaline coumarin precursor with a NBD-masked 7-hydroxycoumarin through an ester bond to develop a robust fluorescent probe, TCAN, for the differentiation of Cys/Hcy, GSH, and H2S. TCAN displayed three distinct fluorescence signals in response to biothiols: blue-green for Cys/Hcy, blue for GSH, and blue-red for H2S. Significantly, the first discriminatory detection of Cys/Hcy, GSH and H2S in living organisms (zebrafish) was realized using probe TCAN.Graphical Graphical abstract for this articleThe discriminatory detection of Cys/Hcy, GSH and H2S in living cells and organism (zebrafish) was realized by a triple-emission fluorescent probe TCAN through the combination of three distinct fluorescence signals (blue-green-red).
       
  • Green tide biomass templated synthesis of molybdenum oxide nanorods
           supported on carbon as efficient nanozyme for sensitive glucose
           colorimetric assay
    • Abstract: Publication date: Available online 1 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Han Ren, Lu Yan, Mingjun Liu, Yanbo Wang, Xuan Liu, Chongyang Liu, Qing Liu, Lingxing Zeng, Aihua Liu The nanozymes, alternative for natural enzymes, have become popular in many research fields because they exhibit relatively high activity and stability. Herein, we utilize abundant, renewable ocean green tide (Enteromorpha prolifera, EP) waste as a biotemplate to facilely prepare MoO3 nanorods supported on EP derived carbon (MoO3/C). The as-prepared MoO3/C exhibited excellent peroxidase-like activity with Km of 0.13 mM and Vmax of 0.292 µM s-1 (H2O2 as the substrate), superior to most mimetic peroxidases reported so far. The catalytic mechanism of the as-synthesized MoO3/C is proven to be a Ping-pong BiBi electron transfer mechanism. Further, the MoO3/C was used for non-enzymatic measurement of H2O2 sensitively, with the linear H2O2 concentration range of 1–100 μM and a low limit of detection (LOD) of 0.181 μM (S/N = 3). Based on its excellent catalytic activity and stability, the MoO3/C was coupled with glucose oxidase to apply for the colorimetrically sensing glucose sensitively and selectively, with two linear parts, 0.02–0.5 mM as well as 0.5–6.0 mM glucose and a LOD of 10 μM glucose (S/N = 3). Moreover, the detection of blood glucose in real human serums was realized successfully. Thus, the green tide biomass waste templated strategy opens up an avenue to develop nanozymes for many applications, which is simple, cost-effective and environmentally friendly.Graphic abstractGraphical abstract for this article
       
  • Chip modularity enables molecular information access from organ-on-chip
           devices with quality control
    • Abstract: Publication date: Available online 15 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Wu Shang, Chen-Yu Chen, Kimberly Lo, Gregory F. Payne, William E. Bentley Organ-on-chip (OOC) devices are envisioned to replace animal models in preclinical toxicity and efficacy testing. Although significant progress has been made towards ensuring the biofidelity of these devices, analyzing samples from within these miniaturized structures remains a challenge. Based on the concept of modularity, we developed accessorial modular functional units that facilitate molecular information access to and from OOCs. Specifically, we developed three mutually independent microfluidic modules: a mixer, a “molecular-electronic” sensor, and a quality control unit. Each module can be interconnected/disconnected, replicated or replaced as needed. As a proof of concept, we developed a cytotoxicity assay comprised of two modules and linked these to a model OOC providing near real time molecular information on OOC function. Additionally, we developed sensor design criteria for generic use, particularly for on-chip measurements that require substrates and enzymes. We monitored sensor function during long-term experiments and, by design, maintained assay consistency by switching out fouled sensors. Importantly, using electrobiofabrication, our sensor assembly with biological components and its connection to the OOC requires only minutes and no bulky instrumentation. We believe a modular strategy wherein various chips are assembled in situ and subsequently interrogated in real time could provide an alternative and promising path to enhance functionality, reproducibility, and utility. They will enrich our abilities to access biological information in a variety of contexts.
       
  • A novel ESIPT-ICT-based near-infrared fluorescent probe with large
           Stokes-shift for the highly sensitive, specific, and non-invasive in vivo
           detection of cysteine
    • Abstract: Publication date: Available online 15 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Lihe Zhao, Xu He, Yibing Huang, Jialiang Li, Yiling Li, Shuo Tao, Ying Sun, Xinghua Wang, Pinyi Ma, Daqian Song Water solubility, large Stokes-shift, and near-infrared emission are essential properties required for a fluorescent probe used for intracellular detection of the analytes. Herein, we report a new fluorescent probe, BMQA, obtained from the reaction of 2-(2-hydroxyphenyl) benzothiazole, methylquinoline, and acryloyl chloride. By using this probe, it is possible to quantitatively detect cysteine (Cys) in 1% acetonitrile-containing PBS buffer solution (pH 7.2). The experimental results showed that the probe exhibited an excellent spectral performance with an emission wavelength at 740 nm, Stokes shift of 310 nm, and detection limit of 0.062 μM for Cys. Theoretical calculations were also conducted to clarify the luminescence mechanism of the system. In addition, the experiments performed on A549 living cells showed that BMQA is suitable for the in detection of Cys in human serum by fluorescence imaging.Graphical abstractGraphical abstract for this article
       
  • A novel FRET biosensor based on Four-way Branch Migration HCR for Vibrio
           parahaemolyticus detection
    • Abstract: Publication date: Available online 15 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Dongxia Ren, Chengjun Sun, Zhijun Huang, Zewei Luo, Chen Zhou, Yongxin Li A versatile and powerful fluorescence resonance energy transfer (FRET) biosensor based on four-way branch migration hybridization chain reaction (HCR) was proposed for the detection of Vibrio parahaemolyticus (V. parahaemolyticus). In the system, two partly complementary hairpin structures of H1 and H2, and an assistant DNA strand (R) were designed. H1 was labeled with carboxyfluorescein (FAM) as fluorophore donor, and H2 was labeled with tetramethylrhodamine (TAMRA) as fluorophore acceptor. When target DNA was presented in the system, it would firstly bind with the assistant DNA to form a short double-strand DNA (dsDNA), and subsequently trigger the four-way branch migration HCR, which would produce long nicked dsDNA concatamer and bring a good deal of FAM and TAMRA in close proximity, so that dramatic FRET signals could be achieved. With the assistance of well-designed four-way branch migration HCR circuits, this FRET biosensor exhibited a superior detection capability, which could detect 0.067 nM target DNA and as low as 10 CFU mL-1 of V. parahaemolyticus. To our knowledge, it is the first time that a four-way branch migration HCR strategy for signal amplification has been adapted to the FRET biosensor, which might show great potential in food safety and clinical diagnosis.
       
  • Construction of a ratiometric probe with dual quenching mechanisms for
           selectively imaging intracellular sulfur dioxide overcoming the
           interference from cysteine
    • Abstract: Publication date: Available online 15 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Qilong Zhang, Zhongqian Cui, Qiufen Wang, Gengxiu Zheng Endogenous sulfur dioxide (SO2) plays central roles in various biological and pathological events, and abnormal levels of SO2 can induce arterial hypertension, atherosclerosis, stenocardia, pulmonary arterial hypertension, and other diseases. In this work, a fluorescent probe with dual quenching mechanisms has been designed and synthesized, which selectively detected SO2 overcoming the interferences of Cys. The fluorescence of the probe was quenched by the intramolecular charge transfer (ICT) and internal rotation of vinyl group. Reaction with Cys only inhibited the internal rotation, and thus the probe-Cys displayed weak fluorescence. By contrast, addition of SO2 blocked the dual quenching processes and brought intense blue-shifted emission. The probe showed high selectivity, high sensitivity, fast response, and low cytotoxicity, and therefore the ratiometric imaging of intracellular SO2 has been achieved with the probe.Graphical abstractGraphical abstract for this articleA fluorescent probe has been rationally designed and synthesized based on dual quenching pathways, for the selective detection of intracellular SO2 overcoming the interferences from long-term exposure to cysteine.
       
  • Ultrasensitive aptamer fluorometric detection of IFN-γ by dual atom
           transfer radical polymerization amplification
    • Abstract: Publication date: Available online 13 May 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Dongxiao Wen, Qianrui Liu, Lianzhi Li, Huaixia Yang, Jinming Kong Exploiting biological detection methods with high selectivity and sensitivity has been an urgent demand for low abundance biomolecules. Herein, an ultrasensitive aptamer fluorometric method of protein detection was fabricated via a sequential dual atom transfer radical polymerization (ATRP). For the first time, surface-initiated dual ATRP was utilized to make the fluorometric signal amplification for gamma-interferon (IFN-γ) protein assay. Two aptamers are used as protein probes, which can form a high stable and selective “aptamer/protein/aptamer” sandwich structure. One aptamer probe is attached on superparamagnetic nanoparticle via surface self-assembled, the other one is linked with initiators of dual ATRP amplification by click chemistry formed triazole group. With large numbers of fluorescein-o-acrylate grown directly on a nanoparticle surface, a convenient “aptamer/protein/aptamer-polymer” supersandwich sensor was fabricated. Under optimal conditions, IFN-γ can be assayed with detection limit down to 0.178 fM in PBS buffer (equals to 1.072 ˣ103 IFN-γ molecules). Even in complex human serum, IFN-γ can also be detected with the limit of 1.54 fM, equals to 9.275 ˣ103 IFN-γ molecules. Results show a great potential in real ultrasensitive protein detection for its high selectivity, efficiency and stability. Besides, this proposed sensing method, which combines the advantages of superparamagnetic nanomaterial and chemically catalyzed surface-initiated dual ATRP polymerization, compared to the traditional signal amplify methods, is novel, more convenient, simpler and enzyme-free cascade amplification.Graphical sGraphical abstract for this articleUltrasensitive aptamer fluorometric detection of gamma-interferon by dual ATRP amplification.
       
 
 
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