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  Subjects -> CHEMISTRY (Total: 922 journals)
    - ANALYTICAL CHEMISTRY (56 journals)
    - CHEMISTRY (656 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (27 journals)
    - INORGANIC CHEMISTRY (43 journals)
    - ORGANIC CHEMISTRY (48 journals)
    - PHYSICAL CHEMISTRY (71 journals)

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

Showing 401 - 600 of 735 Journals sorted alphabetically
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: 377)
Journal of the American Society for Mass Spectrometry     Hybrid Journal   (Followers: 31)
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: 64)
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: 52)
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: 3)
MATEC Web of Conferences     Open Access   (Followers: 5)
Materials Characterization     Hybrid Journal   (Followers: 35)
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: 6)
Medicinal Chemistry Research     Hybrid Journal   (Followers: 12)
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   (Followers: 1)
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: 10)
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: 92)
Nature Protocols     Full-text available via subscription   (Followers: 72)
Nature Reviews Chemistry     Hybrid Journal   (Followers: 8)
New Journal of Chemistry     Full-text available via subscription   (Followers: 20)
Nitric Oxide     Hybrid Journal  
Nitrogen     Open Access   (Followers: 1)
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: 20)
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: 13)
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: 74)
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: 17)
Polymer Reviews     Hybrid Journal   (Followers: 36)
Polymer Science Series D     Hybrid Journal   (Followers: 4)
Polymer Testing     Hybrid Journal   (Followers: 129)
Polymer-Plastics Technology and Engineering     Hybrid Journal   (Followers: 5)
Polymers     Open Access   (Followers: 19)
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: 38)
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: 31)
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 Boliviana de Química     Open Access  
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: 2)
Scientific Reports     Open Access   (Followers: 76)
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]
  • Highly sensitive and low working temperature detection of trace
           triethylamine based on TiO2 nanoparticles decorated CuO nanosheets sensors
           
    • Abstract: Publication date: 12 December 2019Source: Sensors and Actuators B: Chemical, Volume 301Author(s): Xiao Wang, Yang Li, Zhiying Li, Shouwei Zhang, Xiaolong Deng, Gang Zhao, Xijin Xu Considering the poor sensing abilities and high working temperatures for trace triethylamine (TEA) detection, design and fabrication of TEA gas sensors with high sensitivity and low power consumption are still desired. Decorating p-type substrate with n-type semiconductor to form p-n junction is considered to be an effective approach to enhance their sensing abilities. Herein, regular "droplets on salix leaf" like CuO/TiO2 nanocomposites were designed and successfully synthesized using a two-step method including a water bath treatment and a TiF4 solution etching process. Surface characterizations indicated that the CuO substrate exhibited a salix leaf like nanosheets structure with massive TiO2 nanoparticles (about 11 nm) decorated on its surface. Excitingly, gas sensing results showed that the CuO/TiO2 sensors exhibited a high sensing response of 12.7–5 ppm TEA at a low working temperature (160 °C) and possessed a low detection limit (0.5 ppm). The sensing mechanism was also proposed and attributed to the massive highly dispersed p-n junctions between CuO and TiO2 nanoparticles, which could significantly change the electrical conductivity and oxygen adsorption abilities. In addition, X-ray photoelectron spectroscopy and Electron paramagnetic resonance measurements confirmed the existence of large amounts of surface oxygen vacancy regions and chemisorbed and dissociated oxygen species, which were beneficial to their gas sensing abilities. This work provides a new strategy to fabricate highly sensitive trace TEA gas sensing materials with low working temperatures, which will also promote the application of p-type gas sensors.Graphical abstractGraphical abstract for this article
       
  • Investigation of electronic and chemical sensitization effects promoted by
           Pt and Pd nanoparticles on single-crystalline SnO nanobelt-based gas
           sensors
    • Abstract: Publication date: 12 December 2019Source: Sensors and Actuators B: Chemical, Volume 301Author(s): Martin S. Barbosa, Pedro H. Suman, Jae J. Kim, Harry L. Tuller, Marcelo O. Orlandi This work reports on the gas sensor response of undecorated 1D stannous oxide nanobelts and those decorated with Pt and Pd nanoparticles. The sensor device responses to H2, CO and NO2 were measured in dry air baseline atmosphere as functions of the analyte concentration (1–1000 ppm) and temperature (100-350 °C). Noble metal decorated SnO devices exhibited enhanced chemical sensitization, resulting in increased sensitivity upon exposure to reducing gases at different working temperatures. Differences in enhancement levels are attributed to strong electronic sensitization effects that are dependent on the respective Pt and Pd work functions and the unique SnO band structure, characterized by a small band gap. Gas sensing results also showed superior selectivity to H2 for metal-decorated nanobelts. Based on the findings in this work, we propose an array based on SnO structures capable of detecting and distinguishing reducing and oxidizing gases.Graphical abstractGraphical abstract for this article
       
  • Fabrication of flexible and economical plasmonic biosensor using gold
           nanograting imprinted on hot-melt adhesive film for label-free sensing of
           immunoglobulin proteins
    • Abstract: Publication date: 12 December 2019Source: Sensors and Actuators B: Chemical, Volume 301Author(s): Saswat Mohapatra, Rakesh S. Moirangthem We report here, the fabrication of plasmonic nanograting patterned on hot-melt adhesive (HMA) film via thermal nanoimprint lithography. A soft polymer stamp textured with nanograting pattern was used as a mold to imprint nanograting structure on HMA film overlaid on a flexible polyethylene terephthalate substrate. Thereafter, a 50 nm thickness of gold film was evaporated over surface of the nanograting to prepare a plasmonic sensing layer. The surface plasmon resonance excitation on gold coated nanograting was characterized with the reflectance measurement under the normal incidence of light, which was further verified with theoretical calculations. The bulk refractive index sensitivity of our prepared sensor was obtained 886 ± 55 nm/refractive index unit (RIU). Additionally, a label-free detection of specific target analytes was shown by recording the specific interactions between rabbit immunoglobulin (R-IgG) and anti R-IgG proteins. A surface mass detection limit of 162 pg mm−2 was found in the detection of 100 nM anti R-IgG proteins. Thus, our proposed plasmonic sensor based on low-cost HMA represents another promising thermoplastic material for nanostructure fabrications that have potential applications in the development of affordable, flexible, label-free, and highly sensitive optical/biological sensor.
       
  • A multiple signal amplification based on PEI and rGO nanocomposite for
           simultaneous multiple electrochemical immunoassay
    • Abstract: Publication date: 12 December 2019Source: Sensors and Actuators B: Chemical, Volume 301Author(s): Xiaoqing Zhao, Jing Wang, Hou Chen, Hui Xu, Liangjiu Bai, Wenxiang Wang, Huawei Yang, Donglei Wei, Baiqing Yuan A novel electrochemical immunoassay platform for multi-signal amplification has been constructed and applied to the simultaneous detection of three tumor markers (TMs). The platform was successfully developed by polyethyleneimine (PEI)-polydopamine (PDA)/reduced graphene oxide (rGO) nanocomposites. PDA/rGO as the substrates can simultaneously load with detection antibodies (Ab2) and large amounts of PEI, which PEI were further used to immobilize different signal labels. Three TMs of carcinoembryonic antigen (CEA), prostate specific antigen (PSA) and alpha fetoprotein (AFP) were employed as potential factors. Ferrocenecarboxylic acid (Fc), anthraquinone-2-carboxylic acid (Aq) and acetylsalicylic acid (ASA) were employed as distinguishable signal labels. Electrochemical responses of designed sandwich-type immunosensor were successfully investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The multiplexed immunoassay displayed excellent linear response in the range of 0.102 pg/mL–112 ng/mL for CEA and PSA, 0.117 pg/mL–117 ng/mL for AFP. The detection limit of three TMs were 91 fg/mL, 101 fg/mL and 83 fg/mL for CEA, PSA and AFP, respectively. Moreover, this electrochemical immunoassay platform exhibited excellent reproducibility, sensitivity and selectivity for the simultaneous detection of multiple biomarkers.
       
  • A novel impedimetric sensor for detecting LAMP amplicons of pathogenic DNA
           based on magnetic separation
    • Abstract: Publication date: 12 December 2019Source: Sensors and Actuators B: Chemical, Volume 301Author(s): Sumaira Sharif, Yixian Wang, Zunzhong Ye, Zhen Wang, Qimin Qiu, Shengna Ying, Yibin Ying A novel impedimetric sensor was developed for the detection of loop mediated isothermal amplification (LAMP) amplicons of various foodborne pathogens through combining with a microfluidic system and magnetic separation procedure. The amplified nucleic acid products (amplicons) of the LAMP reaction can adsorb on magnetic beads surface via electrostatic adsorption process. The obtained nucleic acid-magnetic bead composites were re-dispersed in deionized water and the impedance response was measured by injecting the nucleic acid-magnetic bead composites into the microfluidic system. On account of the quite low conductivity (1˜2 μS cm―1) of deionized water, the weak change of charge can be detected by impedance. Thus the abundant negative charges of nucleic acids in the composites can produce an obviously reduction of impedance signal. Based on the principle, the developed impedimetric sensing method was used for sensing various foodborne pathogens including Escherichia coli O157:H7 (E. coli O157:H7), Vibrio parahaemolyticus (V. parahaemolyticus), Staphylococcus aureus (S. aureus), and Listeria monocytogenes (L. monocytogenes), which achieved a low detection limit (10 copies). Compared with the conventional gel electrophoresis method, our method is more sensitive and faster, which has a potential for fast and sensitive detection of the LAMP products of various targets.
       
  • QSPR modeling of potentiometric sensitivity towards heavy metal ions for
           polymeric membrane sensors
    • Abstract: Publication date: 12 December 2019Source: Sensors and Actuators B: Chemical, Volume 301Author(s): Vitaly Soloviev, Alexandre Varnek, Vasily Babain, Valery Polukeev, Julia Ashina, Evgeny Legin, Andrey Legin, Dmitry Kirsanov Potentiometric electrodes with plasticized membranes containing various ligands are widely employed as ion-selective sensors and as cross-sensitive sensors in multisensor systems. The design and testing of the appropriate ligands to make the sensors with required properties is a long and tedious process, which is not always successful. The concept of quantitative structure-property relationship (QSPR) seems to be an attractive complement to the ordinary ligand testing and design in potentiometric sensing. In this study we explore the feasibility of QSPR as a tool for in silico prediction of sensor performance of various ligands in PVC-plasticized potentiometric sensor membranes. The data on potentiometric sensitivity towards Cu2+, Zn2+, Cd2+, Pb2+ of membranes based on 35 nitrogen-containing ligands were employed for QSPR modeling. In spite of the limited dataset the derived models relating the chemical structures of the ligands with their electrochemical sensitivities have reasonable precision of sensitivity prediction with root mean squared errors RMSE around 5 mV/dec and squared determination coefficient R2det about 0.8 in external 10-fold cross-validation for zinc, cadmium and lead. This shows a good promise for further research in this area.
       
  • Microfluidic paper-based analytical devices for environmental analysis of
           soil, air, ecology and river water
    • Abstract: Publication date: 12 December 2019Source: Sensors and Actuators B: Chemical, Volume 301Author(s): Chia-Te Kung, Chih-Yao Hou, Yao-Nan Wang, Lung-Ming Fu Microfluidic paper-based analytical devices (μPADs) have experienced rapid growth over the past decade due to their simple design, low cost, minimal sample requirement, and good sensitivity, selectivity and accuracy. While designed originally for point-of-care medical diagnostics, biological, and food safety applications, μPADs are now used increasingly for environmental monitoring purposes. This review provides a detailed overview of the μPADs developed over the past ten years for the environmental analysis of soil, air, ecology (pesticides) and river water. The review commences by introducing the fabrication techniques and detection methods used in μPAD technology. A detailed description of the main μPAD frameworks proposed in the past decade for environmental monitoring is then provided. The review concludes by examining the challenges facing μPADs for environmental monitoring and identifying probable avenues of future research.
       
  • Centrifuge-based Step Emulsification Device for Simple and Fast Generation
           of Monodisperse Picoliter Droplets
    • Abstract: Publication date: Available online 18 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Dong-Chel Shin, Yuya Morimoto, Jun Sawayama, Shigenori Miura, Shoji Takeuchi Monodisperse picoliter droplets have been widely used for biochemical reactors and preparation of functional microbeads for food, cosmetics, and medical industry. Although conventional microfluidic technologies enable the production of monodisperse picoliter droplets, special instruments (e.g. syringe pump) are required, leading to its poor usability and accessibility in other research fields. In this study, we propose centrifuge-based step emulsification device housed in a microtube for simple and fast generation of monodisperse picoliter droplets. Our device consists of a reservoir part for storage of the dispersed phase and a microchannel part for droplet formation. Centrifugation using a commercial centrifuge exerts excessive pressure on the dispersed phase, infusing it into a microchannel. The infused dispersed phase is pinched off, forming droplets due to the channel geometry for step emulsification. The produced droplets at the step then are transported to the bottom of the microtube due to the centrifugal force. Using this device, we achieved formation of monodisperse water-in-oil (W/O) picoliter droplets with diameters ranging from 18 to 90 μm. Moreover, we demonstrated the cell-free protein synthesis reaction in monodisperse picoliter droplets as well as the production of cell-sized glucose-responsive hydrogel microbeads. We believe that our device would be a powerful tool for simple and fast preparation of picoliter samples with high usability.Graphical abstractGraphical abstract for this article
       
  • Embedded SnO2/Diatomaceous earth composites for fast humidity sensing and
           controlling properties
    • Abstract: Publication date: Available online 18 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yuhua Zhen, Jiuyang Zhang, Wenxin Wang, Yingda Li, Xiaoxin Gao, Haoyue Xue, Xing Liu, Zilong Jia, Qingzhong Xue, Jun Zhang, Youguo Yan, Njud S. Alharbi, Tasawar Hayat A tin oxide/diatomaceous earth (DE) composite was synthesized via the hydrothermal method without using a template or surfactant, and its humidity-sensing and controlling properties were investigated. The SnO2/DE composites have a special embedded structure, in which SnO2 nanoparticles are embedded in the DE porous frame. The optimal composites exhibit short response and recovery times (T = 3 and 8 s, respectively), and their response (S = 35.64) is 11.88 times higher than that of DE (S = 3). Furthermore, the optimal composite C-1:3 was tested to determine its humidity-controlling properties, which revealed that it possessed absorption (27 h, 12.04%) and desorption (5 h, 8.56%) characteristics. Regarding the selectivity, the C-1:3 sensor showed better sensing behavior to humidity than to NO2, NH3 and other gases. These beneficial properties of the composites are due to a honeycomb structure that endows the composite with a large specific surface area for adsorption of H2O molecules and allows charge transfer between the embedded SnO2 nanoparticles. The humidity-sensing mechanism is explained in detail by the Grotthuss proton transfer theory and density functional theory (DFT), which were used together with a Nyquist diagram to analyze the conditions of H2O adsorption. This study demonstrates a novel strategy for designing a material that can rapidly sense and control humidity and provides insights into the application of the composite in sensing and controlling environmental humidity at room temperature.
       
  • Non-enzymatic salivary glucose detection using porous CuO nanostructures
    • Abstract: Publication date: Available online 18 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Pinak Chakraborty, Saurab Dhar, Nitumoni Deka, Kamalesh Debnath, Suvra Prakash Mondal Porous CuOelectrodes have been fabricated using a low cost hydrothermal synthesis. Enzyme-less glucosedetection ability of such porous electrodes has been optimized for different growth conditions. The maximum sensitivity ofthe electrode has been found to be ∼3072 µAmM-1 cm-2, in the linear detection range of 5µM to 0.225 mM and detection limit of ∼0.41 µM. Such CuO based porous electrodes showed ultrafast response time (∼0.8 s)and excellent sensitivity towards glucose detection. The glucose sensing experiments in human saliva samples usingporous CuO electrodes have been demonstrated in this study. A high sensitivity of ∼2299 µAmM-1 cm-2 was obtained, for glucose sensing in human saliva samples. This study showsthe potentialapplication of porous CuO as electrode materialsforcosteffective, enzyme-less and non-invasive glucose sensors for bio-medical devices.Graphical abstractGraphical abstract for this article
       
  • Simple, one step and sensitive fluorescent nanoprobe for simultaneous
           detection of Pb2+ and Cu2+ based on pincer enzyme strand and signal
           amplification strategy
    • Abstract: Publication date: Available online 18 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Xiang Li, Wen Yun, Wenlin Guo, Weilu Zhang, Lizhu Yang A simple, one step and sensitive fluorescent nanoprobe was developed for simultaneous detection of Pb2+ and Cu2+ based on pincer enzyme strand (E-DNA) and circular catalytic cleavage reaction. A pincer E-DNA can be formed by two split E-DNA. The formed pincer E-DNA can form Pb2+ and Cu2+ dependent DNAzyme by combining with the substrate strand (S-DNA) on the gold nanoparticles (AuNPs). Then, the fluorophore labeled S-DNA is cleaved and released from the surface of AuNPs with the assistance of Pb2+ and Cu2+. Meanwhile, the pincer E-DNA is also released for circular catalytic cleavage reaction, causing significant recovery of the fluorescent intensities for both Pb2+ and Cu2+. This method offers high sensitivity with detection limit of 80 pM for Pb2+ and 30 pM for Cu2+. It also shows high specificity for simultaneously detection of Pb2+ and Cu2+. This strategy has great potential to be used for simultaneous detection and imaging of metal ions in environmental and living cell samples.Graphical abstractGraphical abstract for this article
       
  • Methylene blue-encapsulated liposomal biosensor for electrochemical
           detection of sphingomyelinase enzyme
    • Abstract: Publication date: Available online 17 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Ankan Dutta Chowdhury, Enoch Y. ParkABSTRACTSphingomyelinase (SMEnzyme) converts sphingomyelin into ceramide, modulating membrane properties and signal transduction which inactivates mutations and causes Niemann–Pick disease. Real‐time monitoring of SMEnzyme is also crucial as an important biomarker for several other diseases like atherosclerosis, multiple sclerosis, and HIV. In this study, we present an electrochemical method to detect SMEnzyme concentration that is more sensitive and much faster than currently available commercial assays. For detection and the amplification of the SMEnzyme signal, methylene blue (MB)-encapsulated sphingomyelin (SM)-based liposome with 50 % cholesterol was synthesized via sonication method. Then the target SMEnzyme causes the free release of the MB from the MB-liposome formulation which can be detected on GCE Au-PAni/N,S-GQDs electrode, prepared via interfacial polymerization and then self-assembly approach. The change of SM to gel state bilayer with increasing concentration of ceramide accounts for the observed increase in membrane permeability and consequent release of encapsulated MB as the redox indicator for electrochemical Differential Pulse Voltammetric (DPV) analysis. To get the optimum capture through π–π stacking interaction of the released MB on the Au-PAni/N,S-GQDs nanocomposites, which has been used as working electrode. Minimal cross-reactivity with similar phospholipase and proteins confirms the stable and non-leaky MB-liposome platform with low background signal and high specificity toward SMEnzyme. Additionally, the applicability of the proposed sensor has successfully verified in three possible sources of human serum, plasma and cell supernatant without compromising its performance. Taken together, the simplicity, rapid response time and high sensitivity of this present method offer huge potential in point-of-care diagnostics of SMEnzyme detection.
       
  • Variation of shell thickness in ZnO-SnO2 core-shell nanowires for
           optimizing sensing behaviors to CO, C6H6, and C7H8 gases
    • Abstract: Publication date: Available online 17 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Jae-Hun Kim, Ali Mirzaei, Hyoun Woo Kim, Sang Sub KimABSTRACTZnO-SnO2 core-shell nanowires (C-S NWs) with different shell thicknesses (0-120 nm) were prepared and their sensing behavior was systematically studied. ZnO-SnO2 C-S NWs were prepared using a two-step synthesis procedure, where core ZnO NWs were synthesized by a vapor-liquid-solid growth technique, and subsequently these cores were coated with SnO2 shell layers by using an advanced atomic layer deposition technique. The sensors were exposed to 10-ppm CO, C6H6, and C7H8 gases at an optimal working temperature. The shell thickness was optimized to be 40 nm, for which the sensor revealed the highest sensitivity and fastest dynamics to the above-mentioned gases. The sensing mechanism was discussed in detail and the dominant mechanism was related to the radial modulation effect as well as the volume fraction of the shell to the total volume of C-S NWs.Graphical abstractGraphical abstract for this article
       
  • Species-specific TM-LAMP and Trident-like lateral flow biosensor for
           on-site authenticity detection of horse and donkey meat
    • Abstract: Publication date: Available online 17 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Chao Zhang, Xiujie Zhang, Guozhou Liao, Ying Shang, Changrong Ge, Rui Chen, Yong Wang, Wentao Xu Global food research is placing increasing emphasis on the on- site authenticity detection of meat since it is vital for this process to be conducted accurately and efficiently. In this study, a trident-like lateral flow biosensor (LFB) for multiple on-site authenticity detection of horse and donkey meat was established for the first time based on species-specific TM-LAMP (tag-labeled multiplex loop-mediated isothermal amplification). Firstly, a novel, accurate model for screening chromosomal endogenous reference genes was constructed using Perl as the bioinformatics language, based on which the single-copy genes LOC106782588 and LOC106825524 were selected as the endogenous reference genes for horses and donkeys, respectively. Secondly, antigen tag-labeled multiplex LAMP based lateral flow biosensor was established. Following optimization, the limit of detection (LOD) reached a level as low as 40 pg, which was equivalent to 15 copies in horses and donkeys. TM-LAMP was proved to be suitable for on-site detection since the process took only 40 min, with no need of any precision instruments. The analysis of various processed foods and mixed meat products indicated that this biosensor displayed high specificity and sensitivity consistently. As a universal platform, this biosensor can be custom-designed for on-site detection of other species by changing specific primers, which might be an excellent prospect for the identification of species authenticity.
       
  • Quantitative Remote and On-Site Hg2+ Detection Using the Handheld
           Smartphone Based Optical Fiber Fluorescence Sensor (SOFFS)
    • Abstract: Publication date: Available online 17 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Ting Liu, Wenqi Wang, Dan Jian, Jiahao Li, He Ding, Dingrong Yi, Fei Liu, Shouyu Wang In order to detect Hg2+ in remote and on-site mode, we design a smartphone based optical fiber fluorescence sensor (SOFFS), which is composed of a semiconductor laser for fluorescence signal excitation, a quantum dot modified fiber probe for Hg2+ sensing, a smartphone with a filter for fluorescence signal collection, and a fiber coupler for connecting probe, laser and smartphone. With the evanescent wave on the optimized combination tapered fiber probe surface, SOFFS has an ultra-low detection limit of 1 nM and a wide detection range between 1 nM to 1000 nM. Besides, it is handheld with a small size of 79×57×154 mm3 and inner power supply, and the combination tapered fiber probe can be easily replaced, supporting the remote and on-site applications. Additionally, a smartphone application is designed for automatically quantifying the fluorescence signals for accurate and rapid Hg2+ detection. Since SOFFS is compact and cost-effective, moreover, it can measure Hg2+ in fast speed, excellent selectivity, high accuracy and sensitivity, it is a potential tool for remote and on-site applications.
       
  • A novel mixed-potential type NH3 sensor based on Ag nanoparticles
           decorated AgNbO3 sensing electrode synthesized by demixing method
    • Abstract: Publication date: Available online 17 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Xu Li, Lei Dai, Wei Meng, Yuehua Li, Ling Wang, Zhangxing He Solid-electrolyte type sensors based on composite sensing electrodes (SE) have attracted extensive attention due to their excellent sensitivity and anti-interference property. Herein, we prepare AgNbO3/Ag (ANO/Ag) composite SE for the solid-electrolyte type NH3 sensor using a facile demixing method. Compared with pristine ANO-SE, the sensor based on ANO/Ag-SE exhibits larger response signal, higher sensitivity and lower detection limits. What’s more, the anti-interference capability of the sensor toward NOx is effectively enhanced. The effect of the molar ratio of Ag to Nb on the performance of the sensor is also investigated. When the molar ratio of Ag: Nb is 1.05: 1, the sensor exhibits largest response signals and sensitivity (−91.2 mV/decade) to NH3. In the meantime, the response signal of the sensor to a fixed NH3 concentration almost keeps constant under different relative humidity (RH) and oxygen concentrations. Thus, the demixing method will provide a new approach for the fabrication of composites SEs with high performance for gas sensors.
       
  • A fluorescent assay for alkaline phosphatase activity based on inner
           filter effect by in-situ formation of fluorescent azamonardine
    • Abstract: Publication date: Available online 16 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Pengjuan Ni, Chuanxia Chen, Yuanyuan Jiang, Chenghui Zhang, Bo Wang, Yizhong Lu, Hua Wang A simple and sensitive fluorescent assay for determination of alkaline phosphatase (ALP) activity has been developed based on the inner filter effect (IFE) of p-nitrophenol (PNP) through the in-situ formation of azamonardine. Herein, p-nitrophenylphosphate (PNPP) was used as ALP substrate, which could be hydrolyzed to PNP with an absorption band centered at 405 nm. Under the alkaline condition, the introduction of resorcinol into the oxygen-containing dopamine solution would trigger the formation of fluorescent azamonardine with an intense emission band centering at 460 nm when excited at 415 nm. As a result, the fluorescence of azamonardine could remarkably decrease in the presence of PNP via IFE due to the absorption spectrum of PNP overlaps with the excitation spectrum of azamoardine. An IFE-based fluorescent assay has been thereby proposed for the ALP activity detection showing a linear range from 0.1 to 6.0 mU mL-1 with the detection limit down to 0.07 mU mL-1. Moreover, the developed fluorescent assay was successfully applied to probe ALP in human serum samples with satisfactory results. This IFE-based detection strategy exhibits several merits such as high sensitivity, good anti-interference ability, time-saving and easy operation simply by mixing the commercial reagents together. Therefore, it may promote the development of simple and sensitive fluorescent assays for the enzyme activity detections.Graphical abstractGraphical abstract for this articleA fluorescent assay for alkaline phosphatase detection is proposed based on inner filter effect by in-situ formation of fluorescent azamonardine
       
  • In situ growth of Co3O4@NiMoO4 composite arrays on alumina substrate with
           improved triethylamine sensing performance
    • Abstract: Publication date: Available online 16 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Keng Xu, Qian Tang, Wei Zhao, Xing Yu, Yong Yang, Ting Yu, Cailei Yuan Array-based sensors are considered as potential candidates for gas detection due to their low cost and great miniaturization potential. However, the fabrication process of array-based sensors is complex and time-consuming since it usually contains the formation and growth processes of seed layers on the surface of alumina substrates. In addition, the gas-sensing materials for the fabrication of array-based sensors are mainly confined to n-type semiconductors such as ZnO, TiO2 and WO3. In this work, a kind of p-type heterostructures arrays composed of NiMoO4 nanosheets and Co3O4 nanowire (Co3O4@NiMoO4) was fabricated in-situ on flat alumina substrates via a simple hydrothermal method without seed layers. SEM and TEM characterizations revealed that the Co3O4 nanowire arrays were fully covered with NiMoO4 nanosheets. The gas-sensing measurements revealed that the Co3O4@NiMoO4 composite arrays showed the highest response (Rg/Ra = 17.12) towards 100 ppm trimethylamine at its optimal operating temperature of 250 °C. This response value was 3.91 times higher than that of Co3O4 arrays (Rg/Ra = 4.39) and 9.25 times higher than that of NiMoO4 nanosheets (Rg/Ra = 1.85) at their optimal operating temperatures of 250 and 350 °C, respectively. Meanwhile, the enhanced sensing mechanism of the Co3O4@NiMoO4 composite arrays was also discussed. It could be explained by the special heterojunction structure of the Co3O4@NiMoO4 composite arrays, which offered a high surface area and an additional modulation in resistance. Our studies shed a new light to design p-type heterostructure arrays in-situ for fabricating sensing device by a facile method. Moreover, the as-designed Co3O4@NiMoO4 composite arrays are potential candidates in the fabricating of high performance trimethylamine sensors.
       
  • One-pot electrosynthesis of silver nanorods/graphene nanocomposite using
           4-sulphocalix[4]arene for selective detection of oxalic acid
    • Abstract: Publication date: Available online 16 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Ramila Devi Nagarajan, Ashok K. Sundramoorthy Oxalic acid (OA) is present in various plants, animals and microorganisms. Abnormal levels of OA could remove Ca2+ from blood and form less soluble salts in the digestive system which can lead to kidney stones. So, it is very important to accurately measure the OA concentration in various samples for medical diagnosis and controlling renal stone formation. In this study, we reported an electrochemical synthesis of graphene (Gr) functionalized with silver nanorods (Ag NRs) using 3D surfactant 4-sulphocalix [4] arene (SCX) and silver nitrate (AgNO3) from an aqueous solution. SCX is acted as a soft template to form Ag NRs along with the Gr sheets. UV-Vis (UV-Vis), Fourier-transform infrared (FT-IR) and Raman spectroscopies have confirmed the formation of Gr with Ag NRs. In order to develop a selective electrochemical sensor for OA, Gr-Ag NRs nanocomposite coated glassy carbon electrode (GCE) was prepared and tested for OA oxidation. This new sensor (Gr-Ag NRs/GCE) exhibited high catalytic activity for OA in 0.1 M phosphate buffer and it showed a linear detection of OA from 3 to 30 mM with a detection limit of 0.04 mM. The effect of scan rate, pH and amount of catalysts were optimized. The interference of metal ions (Mg2+, Ca2+, Zn2+, Ni2+ and Co2+) and biomolecules such as ascorbic acid (AA) and uric acid (UA) were tested. Gr-Ag NRs/GCE is selectively responded to OA in the presences of these interferent ions. Moreover, the Gr-Ag NRs nanocomposite based sensor was successfully applied to detect OA in tap water samples with recoveries of 100 to 102%.Graphical abstractGraphical abstract for this article
       
  • Antibody-responsive signal-off fluorescence of DNA-harbored silver
           nanoclusters for direct, rapid and sensitive immunoassay
    • Abstract: Publication date: Available online 16 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Chong Li, Wenting Yang, Ruo Yuan, Wenju Xu Specific DNA sequence-templated silver nanoclusters (AgNCs) are extremely promising fluorescent emitters in biosensing and bioanalysis. Here, based on the targeted antibody-responsive fluorescent quenching of AgNCs harbored in a unique DNA-based nanoassembly, we propose a specific, sensitive and one-step immunoassay of bivalent anti-digoxigenin (Dig) antibody (antiDA) as a model analyte. For proof-of-concept, this functional nanoassembly (CS1/RS/CS2) consists of a reporter strand tethering Ag-nucleable template (RS) and two capture strands (CS1 and CS2) labeled with hapten Dig, in which two tethered Dig haptens are closely positioned, and brightly emissive AgNCs can be accommodated and stabilized in the unpaired Ag-nucleable scaffold to produce significant fluorescent emission (CS1/RS/CS2-AgNCs). In the presence of antiDA, the specific conjugation of antiDA with two Dig haptens results in the conformation stretch of CS1/RS/CS2, and simultaneously the harbored AgNCs are destabilized to aggregate each other into larger non-fluorescent silver nanoparticles (AgNPs). The remarkable decreasing of AgNCs fluorescence emission is linearly proportional to the antiDA concentration with a high sensitivity down to 4.5 pM. With this regulatory antibody-dependent signal off scheme, the advantageous rapidness and simplification would be attractive and promising for highly specific detection of diverse bivalent antibodies or small molecules.
       
  • Chromium(VI) sensor based on catalytic reduction using the nanoporous
           layer of poly(aminopyrimidyl- terthiophene) and AuNi composite
    • Abstract: Publication date: Available online 16 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Min-Ouk Park, Kyeong-Deok Seo, Yoon-Bo Shim, Jang-Hee Yoon, Deog-Su Park Nanoporous layer of Ni-dealloyed AuNi composited with a functionalized conductive polymer (poly[3′-(2-aminopyrimidyl)-2,2′:5′,2′′-terthiophene] (pPAT)) was electrochemically synthesized, characterized, and applied for a Cr(VI) sensor. At first, we examined the voltammetric response of different kinds of Au alloys (AuCu, AuCo, and AuNi) for the Cr(VI) reduction reaction, where porous AuNi alloy reveals the best performance to the catalytic reduction. Hence, the final sensor was prepared through composition of AuNi and pPAT followed by Ni dealloying, which enhances the catalytic performance through increasing the electrochemical active area by about 10 times. The sensor revealed a well-behavioural catalytic Cr(VI) reduction at around +0.5 V. The surface analysis and electrochemical characterization were performed for each sensor layer to elucidate morphology and surface composition. Experimental parameters affecting the Cr(VI) analysis were optimized and the interference effects were also investigated. The dynamic range of square wave voltammetry was between 1.0 ppb and 10.0 ppm Cr(VI) with the detection limit of 0.25 ± 0.05 ppb (n = 3). The reliability of proposed sensor was evaluated by analysing real water samples and standard reference material.
       
  • Improved Hydrogen Sensing Behaviour in Ion-Irradiated Pd-Au Alloy Thin
           Films
    • Abstract: Publication date: Available online 16 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Deepti, Hardeep Kumar, Ambuj Tripathi, Arka Bikash Dey, Mukul Gupta, Richa Krishna, D.K. Avasthi Present work reports a significant improvement in the hydrogen sensing characteristics of Pd-Au thin film by ion irradiation. The Pd-Au alloy thin film was synthesized by DC magnetron sputtering. The deposited film was irradiated by 500 keV Xe2+ ion at a fluence of 1 × 1016 ions/cm2. The characterizations of the pristine and irradiated samples were performed by XRD, AFM and TEM. The hydrogen sensing characteristics of the pristine and irradiated samples was carried out by electrical resistance measurements using 2% H2 concentration at 250 °C. The alloy film does not delaminate in hydrogen loading/deloading cycles. The improvement in sensing characteristics is attributed to ion irradiation induced defects which facilitate the rate of hydrogen absorption in the films.Graphical abstractGraphical abstract for this article
       
  • Sensing strategy based on Carbon Quantum Dots obtained from riboflavin for
           the identification of pesticides
    • Abstract: Publication date: Available online 16 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): S.V. Carneiro, V.H.R. de Queiroz, A.A.C. Cruz, L.M.U.D. Fechine, J.C. Denardin, R.M. Freire, R.F. do Nascimento, P.B.A. Fechine In this work, a fluorescent sensing strategy was developed for identification of pesticides in food, which was obtained thought the interaction of carbon quantum dots (CQDs) and silver nanoparticles (AgNPs). The CQDs were synthesized from riboflavin according to an experimental design. On this basis, the most appropriate samples were selected and structurally characterized, where AgNPs efficiently quench the fluorescence of CQDs due a fluorescence resonance energy transfer (FRET). The CQDs was titrationed with AgNPs (Ag@PAA and Ag@bPEI), determining the best concentration of quenching (0.228 and 3.030 pmol.L-1, respectively). Furthermore, a strategy of sensing was developed in order to identify the pesticides propanyl, parathion, dimethoate, chlorpyrifos and pyrimicarb, which were also verified in real samples of rice, carrot, orange and pepper. The results were analyzed by linear discriminant analysis (LDA), obtaining different response patterns against pesticide concentrations, with confidence level of 95%. After that, assays were performed using lower concentrations of the analytes. It was verified that in pepper extract, the sensibility of the sensing strategy was 250 ng.mL-1. Therefore, the CQDs synthesized in this work may be considered a powerful tool to identify pesticides in food samples.
       
  • A RAPID AND SENSITIVE BIOSENSOR FOR MEASURING PLASMIN ACTIVITY IN MILK
    • Abstract: Publication date: Available online 13 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Helen Dacres, Jian Wang, Alisha Anderson, Stephen. C. Trowell Plasmin play an important role in milk spoilage and can cause quality issues in UHT milk and other dairy products. Current methods for measuring plasmin activity in milk have low sensitivity and are too slow to be used in routine testing. We report a bioluminescence resonance energy transfer (BRET)-based biosensor that can measure naturally occurring low levels of plasmin activity in milk within a few minutes. The biosensor incorporates a plasmin-specific peptide target sequence flanked by the resonance energy BRET transduction elements: green fluorescent protein (GFP2) at the N-terminus and a variant Renilla luciferase (RLuc2) at the C-terminus. Complete cleavage of the peptide linker sequence by human plasmin led to an approximately 87 % decrease in the starting BRET ratio. Using a 10 minute incubation time, the detection limit for human plasmin was 0.25 nM and 0.86 nM for bovine plasmin in 50 % (v/v) full fat milk with EC50s of 5.89 ± 0.12 nM and 5.97 ± 0.59 nM, respectively. These detection limits are below the naturally occurring levels of plasmin reported to occur in raw or processed cow’s milk. The plasmin biosensor therefore has the potential to measure naturally occurring plasmin levels directly in raw and UHT-processed milk samples. The protease biosensor described herein is selective and sensitive and retains its function in the complex colloidal matrix of milk. It therefore meets many of the requirements for routine use in production settings. We propose its use for managing plasmin-related quality issues in UHT milk and other dairy products.
       
  • Amine-responsive bilayer films with improved illumination stability and
           electrochemical writing property for visual monitoring of meat spoilage
    • Abstract: Publication date: Available online 13 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Xiaodong Zhai, Xiaobo Zou, Jiyong Shi, Xiaowei Huang, Zongbao Sun, Zhihua Li, Yue Sun, Yanxiao Li, Xin Wang, Melvin Holmes, Yunyun Gong, Megan Povey, Jianbo Xiao Amine-responsive bilayer films were developed by using agar (AG), anthocyanins (AN), gellan gum (GG) and TiO2 nanoparticles for visual monitoring of meat spoilage. The AG-AN layer worked as the sensing layer to volatile amines, while GG-TiO2 layer served as the light barrier layer and simultaneously the conducting layer to improve the illumination stability and electrochemical writing ability of the AG-AN layer, respectively. The Scanning electron microscopy (SEM) images and X-ray diffraction (XRD) spectra indicated the successful fabrication of bilayer films. Illumination experiments showed that the incorporation of TiO2 in the GG-TiO2 layer significantly improved the illumination stability of AN in the AG-AN layer. Meanwhile, electrochemical writing process could be easily conducted on the AG-AN layer in the presence of GG-TiO2 layer, indicating the feasibility of ink-free printing on bilayer biopolymer films. The AG-AN/GG-2%TiO2 film presented a limit of detection of 0.018 mM to trimethylamine (TMA), a typical basic gas generated during meat spoilage. Based on its good illumination stability and sensing ability to basic gases, the AG-AN/GG-2%TiO2 film exhibited rose red-to-green color changes along with the spoilage of pork and silver carp, indicating its great potential for monitoring meat spoilage in intelligent food packaging.Graphical abstractGraphical abstract for this article
       
  • A multifunctional quinoxalin-based AIEgen used for fluorescent
           thermo-sensing and image-guided photodynamic therapy
    • Abstract: Publication date: Available online 13 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yuanyuan Li, Qiuchen Peng, Shijun Li, Yuchen Cai, Bin Zhang, Kai Sun, Junbao Ma, Cuiping Yang, Hongwei Hou, Huifang Su, Kai Li Luminogens with aggregation-induced emission (AIE) characteristic drew extraordinary attention owing to their excellent luminescence properties in aggregated state or solid state, which showed wide application prospect in chemical sensing, bioimaging, lighting material and display material. In this work, a novel AIE molecule of (2,3-bis(4-(dimethylamino)phenyl)quinoxalin-6-yl)(phenyl)methanone (designated as LD-red) was facilely synthesized through a single-step reaction with commercially available materials. Based on its intrinsic twisted intramolecular charge transfer (TICT) characteristic, LD-red was successfully utilized as a reversible fluorescent thermometer. More importantly, LD-red exhibited good biocompatibility, which not only can be used as a probe for lipid droplets-specific imaging, but also can work as a promising photosensitizer to kill cancer cells through generation of reactive oxygen species (ROS) upon white light irradiation. LD-red enriches the kinds of AIEgens and, more importantly, this work provides a new strategy for constructing multifunctional AIEgen with TICT characteristic.Graphical abstractGraphical abstract for this article
       
  • Lab-on-Tip: Protruding-shaped All-Fiber Plasmonic Microtip Probe Toward
           In-situ Chem-Bio Detection
    • Abstract: Publication date: Available online 11 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Ling-Xin Kong, Yan-Xin Zhang, Wei-Gang Zhang, Yun-Shan Zhang, Tie-Yi Yan, Peng-Cheng Geng, Biao Wang Lab-on-tip technology opens a new door for optical fiber surface plasmon resonance (SPR) sensors. In this paper, we first demonstrate an ultra-compact reflective SPR microtip probe on the flat fiber end in experiment, which has a length of tens of microns and a diameter of several microns. Simulations and experiments show that this new fiber SPR microtip probe coated with a nano-goldfilm has excellent refractive index (RI) sensing characteristic and great potential for biochemical detection at single cell level. Based on the high RI sensitivity, a bio-probe assembled with Chitosan/Polysodium Styrene Sulfonate (Cs/PSS) nano-polyelectrolyte film and the sheep anti-human IgG-HRP is prepared to recognize human IgG specifically. Due to the high surface sensitivity, the SPR microtip probe exhibits an ultra-low detection limit for human IgG. Due to the high bulk sensitivity and high thermo-optical coefficient (TOC) of polydimethylsiloxane (PDMS), a reference temperature probe based on SPR microtip is proposed, which is used to compensate for the temperature cross-sensitivity of the bio-probe. This new SPR microtip probe can be used not only in optical fiber sensor, but also in Tip-Enhanced Near-Field Raman Microscopy and Scanning Near-Field Optical Microscope.
       
  • Highly selective and sensitive streptomycin chemiluminescence sensor based
           on aptamer and G-quadruplex DNAzyme modified three-dimensional graphene
           composite
    • Abstract: Publication date: Available online 11 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yuanling Sun, Rui Han, Yuxue Dai, Xiaodong Zhu, Hao Liu, Dandan Gao, Chuannan Luo, Xueying Wang, Qin Wei In our work, a highly selective and sensitive streptomycin (STR) chemiluminescence (CL) sensor was successfully prepared based on aptamer and G-quadruplex DNAzyme (G-DNAzyme) modified three-dimensional graphene composite. Initially, β-cyclodextrins and ionic liquids functionalized graphene oxide aerogel (β-CD/IL@GOGA) was successfully prepared and characterized, in which graphene oxide aerogel (GOGA) was used as a skeleton material and provided large specific surface area, β-CD rich in hydroxyl groups and IL containing lots of stable ions increased the biocompatibility and stability of the composite, respectively. Then, tetracycline aptamer (S-Apt) and G-DNAzyme was immobilized on the surface of β-CD/IL@GOGA, consecutively. Finally, G-DNAzyme/S-Apt/β-CD/IL@GOGA was used to construct the CL sensor for STR detection. S-Apt with specific recognition ability to its target and G-DNAzyme as a catalyst of luminol-H2O2 CL system improved the selectivity and sensitivity of the sensor, respectively. When STR existed, G-DNAzyme was released from the surface of S-Apt/β-CD/IL@GOGA due to the specific recognition and binding ability between STR and S-Apt, catalyzing the CL reaction. The CL sensor showed the linear range of 1.4 × 10-12 to 2.8 × 10-9 mol/L and detection limit of 9.2 × 10-14 mol/L (3δ). It was successfully used for STR detection in cucumber and milk samples.Graphical abstractGraphical abstract for this article
       
  • One Bead Three Targets: An Enzyme-Free Platform Enabling Simultaneous
           Detection of Multiplex MicroRNAs on a Single Microbead
    • Abstract: Publication date: Available online 11 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Qinya Feng, Yan Qi, Desheng Chen, Chenghui Liu Multiplexed microRNA analysis is of great significance in early diagnosis and prognosis of cancers. Based on the thermal cycling-assisted click nucleic acid ligation reaction, we wish to report an enzyme-free and mix-and-read fluorescence sensing strategy for the simultaneous detection of several species of miRNA on a single microbead (MB). In this study, the target miRNAs act as the templates to initiate the copper-free click DNA ligation between the bi-functional linker DNA probes (5′-biotin/3′-Aza-DBCO) and reporter DNA probe (3′-N3 and 5′-fluorophore coded for a specific target). Assisted with thermal cycling, each miRNA molecule can be recycled for many rounds to generate a large number of ligation products. Consequently, all of the fluorophore-encoded ligation products are accumulated on only one MB, leading to the highly concentrated fluorescence gathering. Through multi-channel fluorescence imaging of the fluorophore-anchored single MB, simultaneous detection of multiplex miRNAs can be realized with the limit of detection (LOD) lowered down to 16 fM. Benefiting from high sensitivity, excellent specificity, and multiplexed detection capability, the simple and enzyme-free method is promising in miRNA-related biomedical applications.
       
  • Laser and Thermal Dewetting of Gold Layer onto Graphene Paper for
           non-Enzymatic Electrochemical Detection of Glucose and Fructose
    • Abstract: Publication date: Available online 10 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Antonino Scandurra, Francesco Ruffino, Salvatore Sanzaro, Maria Grazia Grimaldi Electrochemical non-enzymatic detections of glucose and fructose were based on gold nanoparticles (AuNPs) onto graphene paper. Electrodes based on AuNPs have been obtained inducing dewetting, by thermal (furnace) or by laser, of sputter deposited 8 nm-thick Au layer onto graphene paper. The electrodes were characterized by Scanning Electron Microscopy, Micro Raman Spectroscopy, X-ray Diffraction, Rutherford back-scattering Spectroscopy and Cyclic Voltammetry. The main difference exhibited by thermal and laser dewetting processes lies in the size and shape of the resulting gold nanoparticles. Laser dewetting originates smaller particles than that obtained by thermal dewetting. The particles are almost spherical and mainly localized onto graphene nanoplatelets. The size of AuNPs is in the ranges 10-150 nm. Electrodes obtained by thermal process present gold nanostructures characterized by faceted AuNPs. Typical sizes are in the range of 20-40 and 200-400 nm. The electrocatalytic activity toward glucose and fructose oxidation in alkaline phosphate buffer solution are presented and discussed. Glucose was detected at a potential of 0.17 V (laser dewetting) or 0.19 V (thermal dewetting) vs SCE, which corresponds to the intense peak of two electrons oxidation. Fructose was detected at potential of 0.4 V vs SCE. Sensitivity up to 1240 µA mM-1 cm-2 for glucose detection was obtained. The resulting analytical performances for glucose and fructose detection are very promising since comparable to the actual state of art for nanostructured gold electrodes which are, however, produced by complex multi-steps wet processes and/or enzymes.
       
  • Efficiently mitochondrial targeting fluorescent imaging of H2S in vivo
           based on a conjugate-lengthened cyanine NIR fluorescent probe
    • Abstract: Publication date: Available online 10 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Tingting Zhou, Yutao Yang, Keyan Zhou, Ming Jin, Mengnan Han, Wei Li, Caixia Yin As an important biological messenger and effector molecule, hydrogen sulfide (H2S) not only is involved in maintaining the physiological function in cardiovascular, immune and nervous systems but also controls the activity of mitochondrial atpase and antioxidant stress in living cells. Herein, a new PET-based mitochondria-targeted NIR probe Mito-N3 with good selectivity and high sensitivity for H2S was presented in this work. The free probe has no fluorescence, however, once reacts with H2S, Mito-N3 goes through an analyte-prompted immolation, resulting in the releasing of the fluorophore (Mito-OH) and the concomitant restoring of remarkable fluorescence in the NIR emission at 736 nm. The detection limit was calculated as low as 20 nM. Most importantly, fluorescence imaging experiments showed that the probe can monitor the intracellular H2S level in mitochondria of MCF-7 cells, the probe Mito-N3 also had the potential application in sensing and tracking H2S in living nude mice.
       
  • A simple fluorescent probe for fast and sensitive detection of inorganic
           phosphate based on uranine@ZIF-8 composite
    • Abstract: Publication date: Available online 9 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Huihui Li, Fangxin Fu, Weiting Yang, Lu Ding, Jiaxuan Dong, Yang Yang, Fuxiang Wang, Qinhe Pan A fluorescent probe for inorganic phosphate (Pi) was rationally designed. The probe was constructed by loading uranine in zeolitic imidazolate framework-8 (ZIF-8), during which aggregation-caused quenching occurred. In the presence of Pi, uranine was released owing to the decomposition of ZIF-8, thus leading to fluorescence enhancement. The probe was facilely prepared by a one-step method at room temperature, and possessed a fast response of 3 min and a low detection limit of 0.2 μM. It was further applied to the detection of Pi in urine, and satisfactory recoveries were obtained (93.5-96.0%). This work not only develops an effective tool for Pi detection but also proposes a new strategy to design fluorescent probes for Pi.Graphical abstractGraphical abstract for this article
       
  • Dioxetane-based Chemiluminescent Probe for Fluoride Ion-sensing in Aqueous
           Solution and Living Imaging
    • Abstract: Publication date: Available online 9 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Bowen Gu, Chao Dong, Ruwei Shen, Jian Qiang, Tingwen Wei, Fang Wang, Sheng Lu, Xiaoqiang ChenABSTRACTFluoride plays an important role in our daily life as it associates with a variety of biological and pathological processes. Hence, an analytic method that can detect fluoride ions under physiological conditions with high sensitivity and specificity, and fast response, is needed. Herein, we introduced a dioxetane-based chemiluminescent probe, CL-F, specifically designed for the detection of fluoride ions in physiological environment. The probe CL-F emitted strong green chemiluminescent light within 1 min when incubating with fluoride ions specifically. The linear range for sensing fluoride ions and limit of detection were determined to be 0-30 μM and 0.91 μM, respectively. The probe CL-F was then successfully applied in quantifying fluoride ions in toothpaste and in vivo imaging in living mice, demonstrating CL-F as a promising tool for sensing fluoride ion in vitro and in vivo.Graphical abstractGraphical abstract for this article
       
  • Ionic liquid-based reference electrodes for miniaturized ion sensors: What
           can go wrong'
    • Abstract: Publication date: Available online 8 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Maral P.S. Mousavi, Mohamed K. Abd El-Rahman, Edward K.W. Tan, Haakon H. Sigurslid, Nooralhuda Arkan, John S. Lane, George M. Whitesides, Philippe Bühlmann Ionic liquid-based reference electrodes, especially those containing 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (MeOctIm TFSI), are increasingly used in potentiometric measurements. They replace the conventional salt bridges and establish the reference potential through local partitioning of the ions of the ionic liquid between the reference membrane and the sample solution. Unless the electrochemical cell and the measurement protocol are designed appropriately, these ions can interfere with the response of ion-selective electrodes (ISEs) with polymeric membranes. This work characterizes the effect of MeOctIm TFSI on the response of K+, Na+, and Cl- ISEs with polymeric membranes. The leaching of MeOctIm TFSI from the reference membrane to the sample solution was monitored with UV-Vis spectroscopy. The concentration of MeOctIm TFSI in the aqueous phase increased gradually and plateaued at approximately 1.0 mM. Concentrations as low as 100 μM of MeOctIm TFSI caused large changes to the emf (50–150 mV) of K+, Na+, and Cl- ISEs. The presence of 10 μM of TFSI- was enough to cause Donnan failure of K+ ISEs with valinomycin as ionophore (that is, co-extraction of K+ and TFSI- into the sensing membrane). Use of less lipophilic anions such as tetrafluoroborate (BF4-) or triflate (OTf-) postponed the onset of Donnan failure of cation-selective ISEs to higher concentrations of the anion, but decreased the stability in the reference potential and lifetime of the reference electrode. These results imply that although MeOctIm TFSI-based reference electrodes provide sample-independent and stable electrical potentials, they should be used with caution for measurements with polymeric-membrane ISEs, due to strong interference of both MeOctIm+ and TFSI- with measured values of emf.
       
  • Smart phone-powered capillary electrophoresis on a chip for foodborne
           bacteria detection
    • Abstract: Publication date: Available online 7 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Van Dan Nguyen, Hau Van Nguyen, Khang Hoang Bui, Tae Seok Seo Due to the requirement of high-voltage power supply, on-chip micro-capillary electrophoresis (μCE) suffers from practical on-site bioapplications. In this paper, we introduced a smart phone based electric power system for μCE on a chip with simple electrical operations and improved portability of a μCE device.Since the power of the smart phone is limited to 5 V, we utilized a boost converter circuit to increase up to 250 V, which enables μCE on a chip. The typical µCE channel with a cross design was patterned on the PMMA substrate, and the sample, the waste, the anode and the cathode reservoirs were fabricated. Two steps of μCE consisting of the injection and the separation were performed to separate two amplicons (121 bp FliC gene of Escherichia coli and 161 bp InvA gene of Salmonella serovar Typhimurium). During the injection step, the voltages applied in the sample and waste reservoirs were 0 V and 250 V, respectively, and the amplicons were filled in the injection channel (6.8 mm length) in 50 sec. We switched the power supply to the anode reservoir with 250 V and the cathode reservoir with 0 V. Two amplicons were successfully separated in the separation channel (17 mm length) in 4 min. In order to assign the peak in the electropherogram, we added two bracket ladders with the amplicon sample, so that we could accurately identify the target peak based on a relative migration time.
       
  • Electrochemical performance of indium-tin-oxide-coated lossy-mode
           resonance optical fiber sensor
    • Abstract: Publication date: 12 December 2019Source: Sensors and Actuators B: Chemical, Volume 301Author(s): Paweł Niedziałkowski, Wioleta Białobrzeska, Dariusz Burnat, Petr Sezemsky, Vitezslav Stranak, Harm Wulff, Tadeusz Ossowski, Robert Bogdanowicz, Marcin Koba, Mateusz Śmietana Analysis of liquids performed in multiple domain, e.g., optical and electrochemical (EC), has recently focus significant attention. Our previous works have shown that a simple device based on indium-tin-oxide (ITO) coated optical fiber core may be used for optical monitoring of EC processes. At satisfying optical properties and thickness of ITO a lossy-mode resonance (LMR) effect can be obtained and used for monitoring of optical properties of an analyte in proximity of the ITO surface. However, EC response of the ITO-LMR device to a redox probe has not been achieved for ITO-LMR sensor whereas it is generally observed for commercially available ITO electrodes. The changes in the response to a redox probe are typically used as a sensing parameter when EC label-free sensing is considered, so it is crucial for further development of combined LMR-EC sensing concept. In this work, we focus on enhancing the EC activity of the device by tuning ITO magnetron sputtering deposition parameters. Influence of the deposition pressure on the ITO properties has been the main consideration. Both optical and EC readouts in 0.1 M KCl containing such redox probes as 1 mM of K3[Fe(CN)6] or 1 mM 1,1′-Ferrocenedimethanol were discussed at different scan rate. The performed studies confirm that for optimized ITO properties the ITO-LMR sensor used as the EC electrode may also show excellent EC performance. The observed EC processes are quasi-reversible and diffusion-controlled. Moreover, for the devices, which offer improved EC response, an optical monitoring of the EC process is also possible. According to our best knowledge, fully functional combined optical and EC sensor, where optical effect is resonance-based and other than well-known surface plasmon resonance, is presented for the first time.
       
  • Measurement of As(III) with in situ subtraction of background and
           interferent signals by double potential step-anodic stripping coulometry
    • Abstract: Publication date: 12 December 2019Source: Sensors and Actuators B: Chemical, Volume 301Author(s): M.M. Marei, K.L. Kaht, T.J. Roussel, R.S. Keynton, R.P. Baldwin Water quality monitoring for heavy metal contaminants is currently performed using instrumental techniques that rely on random “grab sampling” where samples are collected on-site and then transported to a central laboratory for analysis. Alternatively, there are some portable instruments which are suitable for monitoring heavy metals in the field. However, both approaches require a trained technician and provide only a snapshot of the water quality at a particular time and place. Far preferable would be a measurement approach that might enable 24/7, on-demand monitoring in real time, and in this work we describe progress on a novel electrochemical sensor system that might make such applications feasible. Specifically, we report advances in a new technique termed anodic stripping coulometry (ASC) in which the charge associated with the deposition and stripping of the contents of a fixed-volume, thin-layer sample cell is used to provide, viaFaraday’s law, an absolute determination of metal content. As(III) was chosen as the target analyte, and a double potential step (DPS) procedure for in situ background correction has been developed, which does not require the use of a separate blank solution. With the DPS-ASC approach, response for As(III) is linear between 10 0–1,000 ppb with a detection limit at the 75 ppb level. Accurate results were obtained both for lab samples containing high levels of other metals, such as Cu(II), Cd(II), Pb(II), and Zn(II), and for river water samples spiked with As(III). While further work remains to be done, this represents important progress in the development of ASC-based sensors suitable for calibration-free, on-site heavy metal monitoring networks.
       
  • A rhodamine-nitronaphthalimide Hg(II) complex for the simultaneous
           detection of oxidised and reduced glutathione
    • Abstract: Publication date: 1 December 2019Source: Sensors and Actuators B: Chemical, Volume 300Author(s): Hemant Sharma, Jonathan M. White, Jiarun Lin, Elizabeth J. New, Frederick M. Pfeffer Dual-fluorophore systems have attracted attention as they offer versatile photophysical properties and multiple mechanisms for sensing. Here we report that the Hg2+ complex of rhodamine-nitronaphthalimide conjugate 1 functions as a switch-on sensor for the simultaneous detection of reduced (GSH) and oxidised (GSSG) glutathione via a resonance Rayleigh scattering process, with detection limits of 4.3 μM and 11.9 μM, respectively. Hydroxide anion regenerates nitronanphthalimide 1 causing the fluorescence to “switch-off”, and the system is recyclable. This photophysical behaviour towards Hg2+, GSH and HO‾ forms the basis of a molecular level INHIBIT and AND logic gate.Graphical abstractThe Hg(II) complex of rhodamine-nitronaphthalimide 1 can sense and discriminate both the oxidised and reduced forms of glutathione (GSSG and GSH).Graphical abstract for this article
       
  • Understanding microfluidic-based gas detectors: A numerical model to
           investigate fundamental sensor operation, influencing phenomena and
           optimum geometries
    • Abstract: Publication date: 1 December 2019Source: Sensors and Actuators B: Chemical, Volume 300Author(s): Mahyar Mohaghegh Montazeri, Allen O’Brien, Mina Hoorfar Microfluidic-based gas detectors have been developed as an alternative method to GC/MS systems (which are bulky, expensive, and require trained professionals), and electronics noses (which require extensive calibration due to sensor drift). However, the performance of microfluidic-based gas detectors requires improvements before being commercially-viable in the gas monitoring market. Similar to other approaches, this novel technology requires a multitude of tests to calibrate against different compounds, concentrations, and environmental conditions. This paper presents a 3D numerical simulation to study the response of microfluidic-based gas detectors across various geometries using Multiphysics modeling of diffusion, surface adsorption/desorption, chemical reactions, and heat and momentum transfer phenomena. By using this model, response curves of different analyte concentrations are generated thereby reducing the need for manual calibration tests and associated costs. In this model, diffusion was demonstrated as the main parameter affecting the response, followed by surface adsorption/desorption and heat and momentum transfer, which had a minimal effect on the response. The model was also used to investigate the effect of the detector’s dimensions (including microchannel length, microchannel height, and sensor housing volume) on sensitivity, selectivity and response/recovery time. Due to an observed trade-off between selectivity and sensitivity, a sum indicator was defined to investigate the best overall performance across various conditions. Results obtained from different geometrical dimensions and gas concentrations demonstrated that a change in channel length has the most pronounced impact on the sum indicator, especially for low gas concentrations.Graphical abstractGraphical abstract for this article
       
  • Gold nanoclusters-based dual-channel assay for colorimetric and turn-on
           fluorescent sensing of alkaline phosphatase
    • Abstract: Publication date: Available online 6 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Pengjuan Ni, Chuanxia Chen, Yuanyuan Jiang, Chenghui Zhang, Bo Wang, Bingqiang Cao, Cuncheng Li, Yizhong Lu Here, based on their bifunctional peroxidase-mimicking activity and fluorescence of bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs), we develop a colorimetric and fluorescent dual-channel assay for alkaline phosphatase activity determination. The peroxidase-like activity of BSA-AuNCs makes it possible to catalyze the oxidation of colorless 3,3’,5,5’-tetramethylbenzidine (TMB) into its blue product (oxTMB) in the presence of H2O2, and result in the fluorescence quench of BSA-AuNCs simultaneously due to the inner filter effect between oxTMB and BSA-AuNCs. While the ascorbic acid generating form alkaline phosphatase (ALP)-catalyzed hydrolysis of L-ascorbic acid-2-phosphate can inhibit the oxidation of TMB, thereby inducing decolorization of oxTMB and fluorescence recovery of BSA-AuNCs. Based on these findings, a dual-readout assay for ALP activity sensing using BSA-AuNCs has been reported for the first time. The detection limitation can reach as low as 0.26 and 0.16 mU/mL by colorimetric and fluorescent method, respectively. Moreover, the developed assay has been successfully applied to detect ALP in human serum samples with satisfactory results. This method may not only offer new idea for simple, sensitive and accurate detection of ALP activity, but also broaden the applications of BSA-AuNCs in bioanalysis.Graphical abstractGraphical abstract for this articleA colorimetric and fluorescent dual-channel method for ALP activity detection is proposed.
       
  • Colorimetric Chemosensor for Detection of a Volatile Organic Compound,
           Ethylamine, Under Versatile Conditions: Solution, Thin-Film, and Dyed
           Fabric
    • Abstract: Publication date: Available online 6 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Ha Lim Noh, Young Ki Park, Byeong M. Oh, Jian Zheng, Sung-Hoon Kim, Woosung Lee, Jong H. Kim In this this study, we present a new colorimetric chemosensor based on the isoindoline structure (ID1) for the detection of volatile organic compounds (VOCs), ethylamines. Spectral changes in the UV-Vis absorption spectrum of ID1 were observed upon exposure to mono-ethylamine, resulting in significant and fast (
       
  • Ozone gas sensing properties of metal-organic frameworks-derived In2O3
           hollow microtubes decorated with ZnO nanoparticles
    • Abstract: Publication date: Available online 6 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Dongzhi Zhang, Zhimin Yang, Peng Li, Xiaoyan Zhou This paper demonstrated a high-performance ozone gas sensor based on metal-organic frameworks (MOFs)-derived In2O3 hollow microtubes decorated with ZnO nanoparticles. The microstructural and morphological features of as-synthesized In2O3/ZnO samples were characterized by various characterization methods, such as XRD, TG, SEM, TEM and XPS. The sensing properties of In2O3 hollow microtubes before and after modified by ZnO nanoparticles were investigated. The In2O3/ZnO composite shows an obvious enhancement in ozone gas sensing performance at the optimum working temperature of 150 °C. The In2O3/ZnO composite sensor shows much higher response (Rg/Ra = 26.12 @ 1 ppm ozone) in contrast with pure In2O3 (Rg/Ra = 14.08 @ 1 ppm ozone). In particular, the detection limit of the In2O3/ZnO sensor is as low as 25 ppb. The enhanced sensing performance of the In2O3/ZnO composite could be explained by the Zn2+ doping and heterojunction created at the In2O3/ZnO interface.
       
  • Rapid detection of CO in vitro and in vivo with a ratiometric probe
           showing near-infrared turn-on fluorescence, large Stokes shift, and high
           signal-to-noise ratio
    • Abstract: Publication date: Available online 5 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Enbo Zhou, Shengyi Gong, Guoqiang Feng A new near-infrared (NIR) fluorescent probe was developed for the detection of CO in living systems. This probe is based on a unique cyanine fluorophore and uses an allyl ether moiety as the reaction site. Optical studies in solution show that this probe has good water solubility and possesses desirable sensing properties for CO including rapid response, high selectivity and sensitivity, large Stokes shift (123 nm), distinct colorimetric changes, and significant turn-on NIR fluorescence changes at 715 nm with high signal-to-noise ratio. Ratiometric fluorescent detection of CO with this probe at 715 and 570 nm is also applicable. The sensing mechanism was proven to be a process of recovery of the fluorophore by removing the allyl group via Tsuji-Trost reaction. Furthermore, this probe was applied for detecting CO in living cells and animals with good bioimaging performance. Moreover, indicated by this probe, more CO could be produced under oxidative stress conditions. All the results indicate that this probe can be applied as a promising new tool for in vitro and in vivo detection of CO.Graphical abstractGraphical abstract for this article
       
  • Improving humidity sensing properties of copolymer-based polyelectrolytes
           by modifying the chemical structure and content of the comonomers
    • Abstract: Publication date: Available online 5 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yang Li, Lufan Zhang, Mujie Yang, Wen He Three kinds of copolymer based polyelectrolytes, including hydrolyzed and sulfonated poly(styrene-alt-maleic anhydride) (HSPSMA), hydrolyzed poly(sodium p-styrenesulfonate-co-maleic anhydride) (HPSSMA), and poly(sodium p-styrenesulfonate-co-itaconic acid) (PSSIA), have been synthesized by the radical copolymerization and functionalized via sulfonation and hydrolyzation. The polyelectrolytes were characterized by FT-IR, 1H-NMR and 13C-NMR, scanning electron microscopy and static water contact angle measurements, and their humidity sensing properties have been investigated at room temperature. The chemical structure and content of the comonomers have great effect on the humidity sensing behaviors of corresponding polyelectrolytes, such as response time, hysteresis and response magnitude, which is ascribed to the distinct interactions of the sensing materials with water molecules. Under optimal conditions, the composite of crosslinked PSSIA (molar feed ratio of SS/IA = 1/4) with polyaniline displayed good response magnitude (impedance variation of two orders of magnitude between 10%RH and 90%RH), small hysteresis (∼4.5%RH) and fast response (t90% of 9 s and 17 s for adsorption and desorption process). The work provides a new approach for the construction of high performance polyelectrolyte based humidity sensors.
       
  • Abundant cross reactivity in DNA circuits: an efficient and universal
           strategy to develop sensor arrays
    • Abstract: Publication date: Available online 5 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Mengmeng Li, Jun Du, Ye Li, Xijiao Wei, Bin Yang, Yin Zhang, Zhu Su Artificial sensor arrays are useful in various applications of biomolecules recognition, but their abilities for pattern recognition are often limited by the insufficient cross reactivity in sensors elements. Herein, the abundant cross reactivity in DNA circuits has been successfully demonstrated and employed in sensor arrays to discriminate various biomolecules including DNA analogues, RNA analogues, gene expression profiles and SNP (Single Nucleotide Polymorphism) targets. In these DNA circuits, a hybridization chain reaction was employed for target recognition, while an entropy-driven amplification process acted as a universal fluorescence output. The fluorescence response patterns were further processed by linear discriminant analysis (LDA) or principal component analysis (PCA), and all the targets were discriminated from each other without any overlap (95% confidence). The sensor elements have been enriched by introduction of mismatches (Sensor Array 1), combination of sensor units (Sensor Array 2), application of orthogonal reactivity (Sensor Array 3) and addition of a new module (Sensor Array 4). Due to the great diversity and limitless opportunity, the powerful cross-reactive DNA circuits have a number of advantages over the classical approaches to construct sensor arrays for biomolecules pattern recognition.Graphical Graphical abstract for this article
       
  • A novel photoelectrochemical singal amplification assay for procalcitonin
           detection based on ZnxBi2S3+x sensitized NiTiO3 matrix
    • Abstract: Publication date: Available online 5 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Rui Xu, Rui Feng, Dong Wei, Tao Yan, Yong Zhang, Wei Cao, Dawei Fan, Qin Wei, Huangxian Ju An original signal amplification photoelectrochemical (PEC) immunosensor for procalcitonin detection was fabricated based on ZnxBi2S3+x sensitized NiTiO3 nanorods. Using ethylene glycol as medium, the NiTiO3 nanorods were successfully manufactured after calcination in air atmosphere, the rod-like structure have rough surface that produced benefit to capture lots of functional ZnxBi2S3+x, the sensitizer sensitized NiTiO3 on ITO substrate by means of a sequential ionic layer adsorption reaction, and the obtained ZnxBi2S3+x/NiTiO3 composites showed an excellent absorption of visible light owing to the matched band gap. By the way, ZnxBi2S3+x/NiTiO3 composites as mimic enzyme of glucose oxidase, high sensitivity was achieved due to the generated H2O2 as holes scavenger when glucose added, that promote the photo electrons transfer quickly, further increased the PEC signal. The as prepared sensor showed a large linear range of 0.0001-50 ng·mL-1 with 0.04 pg·mL-1 detection limit. Simultaneously, the signal amplification strategy of this sensor provides applicable to other PEC immunosensors for detection of other targets.
       
  • Electrochemical sensing based MWCNT-Cobalt tetra substituted sorbaamide
           phthalocyanine onto the glassy carbon electrode towards the determination
           of 2-Amino Phenol: A voltammetric Study
    • Abstract: Publication date: Available online 5 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Bhvimane Sanna Jilani, C.D. Mruthyunjayachari, P. Malathesh, Mounesh, T.M. Sharankumar, K.R.Venugopala Reddy This work describes the synthesis of novel cobalt tetra substituted sorbaamide phthalocyanine (CoTSAPc) and their characterization by FT-IR, UV, Mass, PXRD, SEM and electrochemical analysis. The electrochemical oxidation of 2-amino phenol (2-AP) was studied on MWCNT-CoTSAPc/GCE due to its better electron transferring ability than bare GCE and CoTSAPc/GCE since there is acceleration in surface area of glassy carbon electrode by multiwalled carbon nano tubes. Therefore electrochemical sensing of 2-AP has done on MWCNT-CoTSAPc/GCE in linear range of (CV 0.1-30, DPV 0.1-38, CA 0.05-20 µmolL-1), lower detection limit of (CV 0.03, DPV 0.03, CA 0.016 µmol L-1) and sensitivity of (CV 56.03, DPV 114.09, CA 177.14µAµM-1 cm-2). The fabricated sensor shows good electrocatalytic activity than modified electrode with Pc alone towards oxidation of 2-AP. The MWCNT-CoTSAPc/GCE shows good repeatability, stability and high selectivity even in the presence of excess O-nitrophenol, P-nitrophenol, bisphenol A, aniline and hydroquinone.Graphical abstractGraphical abstract for this article
       
  • Plasma Assisted Formation of 3D Highly Porous Nanostructured Metal Oxide
           Network on Microheater Platform for Low Power Gas Sensing
    • Abstract: Publication date: Available online 5 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Hu Long, Sally Turner, Aiming Yan, Hongmei Xu, Moonsuk Jang, Carlo Carraro, Roya Maboudian, Alex Zettl A facile and versatile approach that integrates highly porous metal oxide nanostructured network with a low power microheater platform is presented for the creation of low-power, miniaturized gas sensors. Highly porous nanostructured metal oxide network is formed by oxygen plasma treatment of a metal containing polymer film followed by a heat treatment. A generalized aqueous metal precursor solution allows a large variety of metal salts to be incorporated into cast polymer films, thus forming nanostructured metal oxide network with various compositions. Gas sensing behavior is demonstrated for Co3O4 -based devices, exhibiting high sensitivity, low detection limit, and fast response and recovery towards formaldehyde gas. The overall fabrication process is flexible and highly scalable. This facile and flexible fabrication method can be used to reproducibly fabricate a variety of low power gas sensors with tunable performances for many applications and has great potential for mass production.Graphical Graphical abstract for this article
       
  • A photonic pH sensor based on photothermal spectroscopy
    • Abstract: Publication date: Available online 5 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Matthew R. Hartings, Nathan J. Castro, Kathryn Gill, Zeeshan Ahmed Although the determination of pH is a standard laboratory measurement, new techniques capable of measuring pH are being developed to facilitate modern technological advances. Bio-industrial processing, tissue engineering, and intracellular environments impose unique measurement requirements on probes of pH. We describe a fiber optic-based platform, which measures the heat released by chromophores upon absorption of light. The optical fibers feature fiber Bragg gratings (FBG) whose Bragg peak redshifts with increasing temperature. Using anthocyanins (pH-sensitive chromophores found in many plants), we are able to correlate visible light absorption by a solution of anthocyanins to heat released and changes in FBG signal over a pH range of 2.5 to 10. We tested the ability of this platform to act as a sensor coating the fiber within a layer of crosslinked polyethylene glycol diacrylate (PEG-DA). Incorporating the anthocyanins into the PEG, we find that the signal magnitude increases over the observed signal at the same pH in solution. Our results indicate that this platform is viable for assessing pH in biological samples and point at ways to optimize performance.
       
  • Composite metal oxide thin film based impedometric humidity sensors
    • Abstract: Publication date: Available online 4 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): M. Velumani, S.R. Meher, Z.C. Alex Composite metal oxide based thin film based sensors are proposed to eradicate the problems faced by the single phase materials. The composite thin films of ZnO and SnO2 are expected to have significantly enhanced humidity sensing properties. In the present work, pure and composite thin films of ZnO and SnO2 are prepared by sol-gel based spin coating. The structural, optical and morphological properties of the films were studied by X-ray diffraction, Ultraviolet-Visible absorption spectroscopy and the scanning electron microscopy. The composite films with different compositions of ZnO and SnO2 phase were studied for their impedometric humidity sensing characteristics. Among the proposed sensors, the zinc rich composite sensors exhibit the maximum sensor response of 95% and sensitivity of 8.6 ± 0.5 kΩ/RH%. Further, the composite metal oxide based humidity sensors exhibit better transient characteristics and significantly lower hysteresis compared to their pure counterparts.Graphical Graphical abstract for this article
       
  • Self-Circulating Electrochemiluminescence Chip for Sensitive Detection of
           Circulating Tumour Nucleic Acids in Blood
    • Abstract: Publication date: Available online 4 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Ying Liu, Zhijin Fan, Yuan Zhou, Jingyan Lin, Yang Yang, Li Yan, Yulin Li, Ling Jiang, Fan Yang, Qiuyu Hu, Jun Yu, Liuyuan Chen, Yuhui Liao Circulating tumour nucleic acids (CTNAs), cell-free nucleic acids released from tumour cells, have been employed as potential markers for the diagnosis and prognosis management of tumours. It is important to develop highly sensitive and reliable methods for the detection of CTNAs. Herein, a self-circulating electrochemiluminescence (ECL) chip was constructed for recognizing the point mutations of CTNAs in serum. This strategy relies on a magnet-controlled self-circulating chip for enrichment of CTNAs in blood samples, and autologous blood transfusion was performed for feedback. Meanwhile, the strategy of base stacking was employed as an effective indicator for the point mutation detection of CTNAs. Furthermore, an amplified ECL assay was employed as a highly efficient signal generation mode, and a low detection limit of 100 amol and desirable specificity were achieved. The performance evaluations for the analysis of clinical CTNA samples indicated that the self-circulating ECL chip reliably responded to CTNAs from the blood. Hence, this platform satisfied the strict clinical requirements for CTNA detection and thus has the potential to serve as a new paradigm for liquid tumour biopsy.
       
  • Ratiometric ATP Detection on Gliding Microtubules Based on Bioorthogonal
           Fluorescence Conjugation
    • Abstract: Publication date: Available online 4 September 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Gang Feng, Boyu Zhang, Shichao Wang, Zhaoyang Ding, Gang Li, Xuanjun Zhang An ingenious microtubule functionalization strategy based on the novel bioorthogonal conjugation is developed to construct fluorescent ratiometric probes for ATP sensing. By single excitation, newly synthesized probe RT-1 exhibited green emission (485 nm) from the bioorthogonal fluorescence conjugation part and orange emission (584 nm) from the ATP sensing part. The fluorescence intensity ratio (I584/I485) displayed good linear response in ATP ranges of 0 - 2.5 mM (y = 0.9282x+0.2398, R2 = 0.9705, LOD =0.0354 mM) and 2.0 - 10.0 mM (y = 2.7153x-3.6234, R2 = 0.9911, LOD =0.0121 mM). Moreover, a paclitaxel derivate probe RT-2 was developed to functionalize in vitro polymerized microtubule for in situ ATP detection. This simple and convenient strategy is anticipated to stimulate more microtubule related applications in both in vitro and intracellular studies.
       
  • A sulfydryl-based near-infrared ratiometic fluorescent probe for
           assessment of acute/chronic mercury exposure via associated determination
           of superoxide anion and mercury ion in cells and in vivo
    • Abstract: Publication date: Available online 26 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yue Wang, Min Gao, Chunyang Liao, Fabiao Yu, Lingxin Chen Mercury exposure is associated with severe oxidative stress especially superoxide anion radicals (O2•-). Mercury exposure is common in the clinic, but it is difficult to track. Although many researchers have tried to reveal the mechanism of mercury exposure, it is still remain vague that the differences between acute mercury exposure and chronic mercury exposure as well as the fluctuations in O2•- during mercury ion (Hg2+) stress. Thus effective tool for O2•- and Hg2+ associated-detection is needed urgently. Herein we have developed a stable near-infrared ratiometric fluorescent probe, HCy-SH, for O2•- and Hg2+ associated-detection. Probe HCy-SH was designed and synthesized based on a heptamethine cyanine fluorophore and a thiol-responsive group. The probe HCy-SH can be used for mercury poisoning detection in HEK 293 cells and mice models with low detection limits of 65 nM for O2•- and 72 nM for Hg2+. Relying on the probe HCy-SH, we found that O2•- burst was much severer in acute mercury exposure than chronic mercury exposure, especially in heart, and Hg2+ mainly accumulated in kidney no matter acute mercury exposure or chronic mercury exposure. The experimental results indicated that the probe HCy-SH was a potential candidate for accurate diagnosis and efficacy evaluation of mercury exposure.Graphical abstractGraphical abstract for this article
       
  • Hierarchical SnO2–Sn3O4 heterostructural gas sensor with high
           sensitivity and selectivity to NO2
    • Abstract: Publication date: Available online 23 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Wenwen Zeng, Yingzhi Liu, Jun Mei, Changyu Tang, Kun Luo, Shaomin Li, Haoran Zhan, Zhoukun He Considering the high harmfulness of NO2 to the environment and human healthy, it is pressing to develop NO2 sensors with high sensitivity and selectivity. In this work, we successfully fabricated a novel hierarchical SnO2–Sn3O4 n–n heterostructure through the solvothermal method and subsequent annealing. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM) characterization of the material confirmed the hierarchical microsphere structure and the formation of SnO2–Sn3O4 n–n heterojunction. The gas sensing experiment demonstrated that the sample annealed at 600°C exhibited excellent NO2 sensing performances at 150°C. Its sensitivities to 5 and 10 ppm NO2 were as high as 48 and 43.6 ppm-1 respectively, and its limit of detection was lower than 20 ppb. Additionally, it possessed excellent selectivity to NO2 as well as good repeatability and stability. With further exploration of the sensing mechanism of hierarchical SnO2–Sn3O4 n–n heterostructure, we proposed that the unique microstructure with a large specific surface area and the formation of n–n-type heterojunctions contribute to the excellent NO2 sensing performance.
       
  • Nano-textured polyimide cantilever for enhancing the contractile behavior
           of cardiomyocytes and its application to cardiac toxicity screening
    • Abstract: Publication date: Available online 23 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Sun-Young Lee, Dong-Su Kim, Eung-Sam Kim, Dong-Weon Lee Polydimethylsiloxane (PDMS) cantilevers with hydrophobic nature have been extensively utilized in biosensors for their relatively good mechanical properties and biocompatibility. However, when nanostructures are formed on the surface of PDMS, it is difficult to observe the long-term behavior of cardiomyocytes because of the inherent hydrophobicity of the material. In this paper, we propose the use of nanotextured polyimide (PI) cantilevers to measure cardiac contractility. The proposed PI material not only has very high biocompatibility, but also has high thermal resistance which is useful for metal deposition and sterilization processes. Additionally, an oxygen-plasma-treated PI cantilever surface provides more suitable environment for cardiomyocytes that have a sarcomere length greater than 2.0 μm, which is close to the size of mature adult cardiomyocytes. Immunofluorescence experiments were conducted to analyze the biological characteristics of cardiomyocytes grown on the nanotextured PI cantilevers. Following these preliminary experiments, the fabricated PI cantilevers were utilized to measure the contractile behavior of drug-treated cardiomyocytes. The different contractile behaviors of cardiomyocytes grown on PDMS and PI cantilevers were also compared using a laser-based displacement sensor. We believe that the nanotextured PI cantilever has significant potential for basic studies on the contraction of matured cardiomyocytes and their interaction with drugs.Graphical abstractGraphical abstract for this articleThe present manuscript describes our efforts in the development of Nano-textured polyimide cantilever for enhancing the contractile behavior of cardiomyocytes and its application to cardiac toxicity screening. We believe that the nanotextured PI cantilever has significant potential for basic studies on the contraction of matured cardiomyocytes and their interaction with drugs.
       
  • Effects of π-Electron in Humidity Sensing of Artificially Stacked
           Graphene Bilayers Modified with Carboxyl and Hydroxyl Groups
    • Abstract: Publication date: Available online 23 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Chun-Hsuan Lin, Wei-Tong Chen, Chi-Hsien Huang, Wei-Yen Woon, Chih-Ting LinABSTRACTIn this study, we investigate humidity sensing performance of an artificially stacked graphene bilayers (ASGBs). Compared with non-modified ASGBs, the humidity sensing response of the ASGBs modified by a low-damage plasma (LD-plasma) can be improved by 40% and sensing selectivity to ethanol can be enhanced by 35% in our experimental results. Under examinations of Raman and XPS, these improvements can be attributed to carboxyl and hydroxyl groups bonding on the ASGBs surface after LD-plasma treatments. As a consequence, the ASGBs π-electron characteristic, which offers the main sensing mechanism, are also modified by the bonding groups. Therefore, these modifications not only help adsorptions of water molecules but also improve humidity selectivity to ethanol and IPA. Based on these developments and characterizations, this work developed a LD-plasma modified ASGBs sensing material for humidity sensing applications.
       
  • Microfluidic Chip System Integrated with Light Addressable Potentiometric
           Sensor (LAPS) for Real-time Extracellular Acidification Detection
    • Abstract: Publication date: Available online 19 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Tao Liang, Chenlei Gu, Ying Gan, Qian Wu, Chuanjiang He, Jiawei Tu, Yuxiang Pan, Yong Qiu, LiuBing Kong, Hao Wan, Ping Wang Metabolism is a common biological mechanism in living cells. Acidification plays an important role in cell metabolism, in which the extracellular pH change is used to indicate the vitality of cells. For extracellular detection of cell metabolic substances, light addressable potentiometric sensor (LAPS) has many advantages, such as high sensitivity, easy encapsulation, and convenient integration with microfluidic system for cell experiments. LAPS is a spatially resolved biochemical sensor based on field-effect. In this work, we present a microfluidic system integrated with LAPS for real-time extracellular acidification rate (ECAR) detection. The functions of traditional microphysiometer are achieved with simpler structure devices. Polydimethylsiloxane (PDMS) chamber was manufactured for cell culture, and microfluidic flow paths were used for medium and drug delivery. A bubble trap device was applied to eliminate air bubbles generated in microfluidics. Characteristic tests and cell metabolism experiments were carried out to determine the performance of LAPS by monitoring the pH change of hepatoma HepG2 cells. Glucose and doxorubicin were delivered to the cell chamber to verify the effects of the drug. The pH sensitivity of LAPS is 335.5 nA/pH at the working point in constant voltage mode. The ECAR of HepG2 cells was -48.53 mpH/min in normal glucose medium (25 mM), and it changed to -114.42 mpH/min in high glucose medium (125 mM) and -17.88 mpH/min under the effect of doxorubicin (10 μM). The results show that the microfluidic LAPS presents good performance in real-time detection of cell acidification and provides a convenient means of assessing cellular specificity of drugs. The modular structure and high expandability make the microfluidic LAPS has good potential in the application of organ-on-chip.
       
  • Synergistic effect of fluorescence recovery and enhancement on
           ultrasensitive visual assay of cyanide anions based on
           N-Acetyl-L-Cysteine-Capped CdTe quantum dots and carbon dots
    • Abstract: Publication date: Available online 15 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Jing Wang, Daquan Li, Yu Qiu, Xinyue Liu, Xin Zhang, Liang Huang, Huimin Wen, Jun Hu Developing a reliable fluorescent nanosensor for cyanide anions (CN−), with the potential to enable visual discrimination by naked eye, is highly sought after yet is limited by low sensitivity and selectivity. Herein based on the synergistic effect of fluorescence recovery and enhancement, a specific dual-emission nano-system was designed for ultrasensitive detection of CN−, by employing carbon dots (peaking at 443 nm) as a reference and N-acetyl-L-cysteine (NALC)-capped CdTe quantum dots (QDs, peaking at 611 nm) as a reporter. The red fluorescence of CdTe QDs is first quenched by Cu2+ primarily with electron transfer. Upon addition of CN−, CN− coordinates with Cu2+ to form [Cu(CN)n](n−1)− complex, causing the Cu2+ to detach from the QDs, and consequently fluorescence recovery. More importantly, the CN− can undergo a nucleophilic addition reaction with the carbonyl group of NALC ligands, inducing 1.3-fold fluorescence enhancement towards the original QDs while the blue fluorescence of carbon dots remains constant. This results the fluorescence intensity ratios (I611/I443) are proportional to the concentrations of CN− in the ranges of 0.02―10 and 15―80 µM, and an ultra-low detection limit down to 10.35 nM is achieved. By using both Cu2+-promoted complexation and addition reaction as recognition units, the present method also showed excellent selectivity for CN− over other coexisting anions. Especially, we have already demonstrated, by spiked tests, the practicability of monitoring the concentration changes of CN− in both environmental water and cassava samples, and further realized visual monitoring of CN− changes in aqueous solution and test paper.Graphical abstractGraphical abstract for this article
       
  • pH-responsive materials for optical monitoring of wound status
    • Abstract: Publication date: Available online 9 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Clemens Gamerith, Daniel Luschnig, Andreas Ortner, Nikolas Pietrzik, Jan-Hinrich Guse, Michael Burnet, Marieke Haalboom, Job van der Palen, Andrea Heinzle, Eva Sigl, Georg M. Gübitz The monitoring of infection status of wounds is an emerging field and the pH of wound exudate is considered one potential indicator of infection. pH indicators intended for use in medical devices, such as swabs or dressings, need to be fixed in place, however, visual pH indicators are usually soluble molecules so are not inherently suitable for use in devices. To address this, we developed a rapid and simple immobilisation method for coupling pH-responsive dyes onto solid phases. The use of a silane based coupling agent for immobilisation of bromocresol purple led to a shift in the pH dependent spectral properties of the resulting material. The pH responsive material changes from yellow to green to blue with rising pH providing an ideal contrast to the reddish colour of most wound exudates. This is a key advantage over currently available alternatives when considering the suitability of this material for incorporation into various medical devices. In addition, we analysed clinical study samples to verify the association between wound infection and elevated pH-values. A device with an embedded indicator that changes to a contrast colour could represents a simple and easy-to-use system for detecting wounds at risk of infection.
       
  • High temperature CO2 sensing and its cross-sensitivity towards H2 and CO
           gas using calcium doped ZnO thin film coated langasite SAW sensor
    • Abstract: Publication date: Available online 7 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Abhishek Ghosh, Chen Zhang, Sheldon Shi, Haifeng Zhang Development of indigenous CO2 sensing element operating at high temperature (≥ 350 °C) is highly desirable. Use of langasite (LGS) based surface acoustic wave (SAW) gas sensors is extremely beneficial compared with other commercially available sensors as it can operate at a higher temperature (> 800 °C). In the present work, we have shown CO2 sensing and its cross-sensitivity performance using LGS based SAW sensor. Compared with LGS with other sensing electrodes, calcium doped ZnO thin film (Ca_ZnO) coated LGS substrate shows enhanced CO2 sensing performance. The interdigitated electrodes (IDT) made of Pt was plated and Ca_ZnO thin film was synthesized and deposited on the LGS substrate. Additionally, we have compared the chemo-resistive gas sensing characteristics of Ca_ZnO thin film with the Ca_ZnO coated SAW sensors. Furthermore, temperature effect on CO2 sensing was studied where optimum response (change in resonant frequency ˜2.469 KHz) was observed at 400 °C. Also, the gas adsorption effect which leads to the change of the resonant frequency of the sensors has been deliberated. Besides, we have discussed the predominant effect of sensor conductivity than mass loading which enhances the reduction of the resonant frequency for thin film coated SAW sensors has been deliberated. Additionally, we have demonstrated the cross-sensitivity of H2 and CO gas in CO2 sensing and their mixed gas sensing behavior operating at 400 °C.Graphical abstractGraphical abstract for this article
       
  • Robust and Sensitive Frost and Ice Detection via Planar Microwave
           Resonator Sensor
    • Abstract: Publication date: Available online 2 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Benjamin Wiltshire, Kiana Mirshahidi, Kevin Golovin, Mohammad H. Zarifi Build up of ice and snow can cause major issues in many industrial and academic endeavors if it is not properly detected and addressed. Ice detection systems are commonly based on visual detection and therefore susceptible to human error and environmental conditions. We introduce a microwave resonator sensor fabricated on a planar substrate operating between 3.5 to 5 GHz with resonant amplitude -14.5 dB and quality factor of 250. The resonator detects water, frost, and ice based on the measured resonant frequency, amplitude, and quality factor variation in scattering parameter, S21, of the sensor. Three situations are investigated to test the effectiveness of the sensor: first, continuous frost formation on the sensor is tracked and the phenomena of water condensation, frost formation, and subsequent frost growth are characterized. Second, a water droplet is placed on the resonator and frozen, enabling faster and more sensitive detection and representing an initial liquid impact or aggregation on a surface followed by freezing. Lastly, controlled frost formation and removal was performed to better understand the effect of substrate temperature on the sensing parameters so that it could be compensated for via calibration.
       
  • Optofluidic label-free SERS platform for rapid bacteria detection in serum
    • Abstract: Publication date: Available online 31 July 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Robert Hunter, Ali Najafi Sohi, Zohra Khatoon, Vincent R. Berthiaume, Emilio I. Alarcon, Michel Godin, Hanan Anis The prevalence of hospital acquired infections and antibiotic resistant pathogens necessitates the development of bacteria sensing systems that do not require sample amplification via conventional cell culturing, which can be prohibitively time-consuming. To meet this need, we designed an optofluidic Raman detection platform which utilized a microfluidic driven hollow-core photonic crystal fiber, which in combination with silver nanoparticles, provides a large enhancement to the Raman signal. By confining both light and cells within this fiber, spectral events generated by the flowing cells facilitates a novel method of cell counting to simultaneously quantify and qualify infections. Counting is performed automatically by a genetically optimized support vector machine learning algorithm that was previously developed by our group. The microfluidic system can be regenerated multiple times, and allows for online detection of planktonic bacteria to levels as low as 4 CFU/mL in 15 minutes. This compares favourably to other methods currently under development such as qPCR and biosensing techniques. Furthermore, Raman spectral differences between bacteria allow for inherent multiplexed detection in serum, by adding another layer to the learning algorithm. Further development of this device has promising potential as a rapid point-of-care system for infection management in the clinic.Graphical abstractGraphical abstract for this article
       
  • Ultrasensitive room temperature NO2 sensors based on liquid phase
           exfoliated WSe2 nanosheets
    • Abstract: Publication date: 1 December 2019Source: Sensors and Actuators B: Chemical, Volume 300Author(s): Rensong Guo, Yutong Han, Chen Su, Xinwei Chen, Min Zeng, Nantao Hu, Yanjie Su, Zhihua Zhou, Hao Wei, Zhi Yang Semiconducting two-dimensional (2D) transition metal dichalcogenides (TMDs) are promising gas-sensing materials due to their large surface-to-volume ratio, layered structures, susceptible surfaces, and excellent conductivities. Herein, a simple and effective method has been developed to exfoliate tungsten diselenide (WSe2) into few-layered nanosheets with N-methyl-2-pyrrolidone (NMP) as a dispersant. The gas sensor based on the as-synthesized WSe2 nanosheets shows an extremely high response (50 ppb, 5.06) under a low detection concentration of nitrogen dioxide (NO2) at room temperature (25 °C), which is much higher than many other reports for 2D TMDs-based gas sensors. Additionally, our sensor also exhibits a response of 11.01 to 10 ppm NO2, an excellent selectivity, and a reliable long-term stability within 8 weeks. It is expected that the outstanding performances of the gas sensors based on WSe2 nanosheets reported in the present work will make WSe2 a promising candidate for ultrasensitive NO2 sensing applications.
       
  • Effect of receptor attachment on sensitivity of label free microcantilever
           based biosensor using malachite green aptamer
    • Abstract: Publication date: 1 December 2019Source: Sensors and Actuators B: Chemical, Volume 300Author(s): Yue Zhao, Agnivo Gosai, Pranav Shrotriya Biosensors are often limited by lesser signal/noise ratio in the detection of low concentration target analyte which may be improved by modifying receptor configuration on the transducer. In this study, we report the improvement in sensitivity, through an increment in surface stress signal, due to the attachment/functionalization of malachite green aptamers with double thiolated ends on microcantilever based sensors, compared to the conventional single thiolated aptamers. Malachite green is deemed to be carcinogenic to humans and its detection using biosensors has been studied by many researchers. Our approach resulted in one order of magnitude improvement in the detection limit for malachite green, on the same sensor. The improvement is attributed to configurational changes of the aptamer on the cantilever surface, induced by the double thiolated attachment, which results in better propagation of mechanical response upon binding with the target malachite green, resulting in higher signal.Graphical abstractGraphical abstract for this article
       
  • Selective H2S sensing without external heat by a synergy effect in
           self-heated CuO-functionalized SnO2-ZnO core-shell nanowires
    • Abstract: Publication date: 1 December 2019Source: Sensors and Actuators B: Chemical, Volume 300Author(s): Jae-Hun Kim, Ali Mirzaei, Jae Hoon Bang, Hyoun Woo Kim, Sang Sub Kim Future gas sensors require minimal power consumption to enable their integration into portable electronics such as smart mobile phones. We developed H2S gas sensors based on a self-heating effect using metal oxide nanowires (NWs). We fabricated bare SnO2 NWs, CuO functionalized SnO2 NWs, and a CuO functionalized SnO2-ZnO core-shell (C–S) NW sensor, and tested their sensor response towards H2S gas by applying different external voltages at room temperature. It was found that the CuO functionalized SnO2-ZnO C-S NW gas sensor had higher response to H2S gas relative to other tested sensors due to higher self-heating effect, formation of heterojunctions, phase transformation, and spillover effects of CuO nanoparticles. Without external heat, the selective H2S detection obtained in this work demonstrates the possibility of embedding low power consumption gas sensors in portable devices for detection of H2S as a biomarker for early diagnosis of diseases.Graphical abstractGraphical abstract for this article
       
  • Ordered gold nanoparticle arrays on the tip of silver wrinkled structures
           for single molecule detection
    • Abstract: Publication date: 1 December 2019Source: Sensors and Actuators B: Chemical, Volume 300Author(s): Hao Guo, Kun Qian, Anjiang Cai, Jun Tang, Jun Liu We demonstrate a method for fabricating nanoparticles in a line at the top of silver wrinkled structures by tilting the substrate. The center of gravity of the colloidal droplets was moved backward, resulting in a small volume of droplets at the front of the colloidal droplet. The droplet rapidly evaporated, and the nanoparticles that remained formed lines of highly ordered nanoparticles. The distance between the nanoparticles changed after stretching the PDMS substrate due to the Poisson effect. An optimal plasma effect was achieved by controlling the distance between the nanoparticles. Finally, the Surface-Enhanced Raman Scattering (SERS) effects of CV and R6G molecules in water were determined, and the detection limit was 10−20 M. This method provides an extremely high sensitivity SERS substrate for the detection of biomolecules.
       
  • Electrochemical-Photoelectrochemical Dual-Mode Sensing Platform Based on
           Advanced Cu9S8/polypyrrole/ZIF-67 Heterojunction Nanohybrid for the Robust
           and Selective Detection of Hydrogen Sulfide
    • Abstract: Publication date: Available online 31 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Hongyuan Shang, Hui Xu, Liujun Jin, Chunyan Chen, Tongxin Song, Cheng Wang, Yukou Du The detection of hydrogen sulfide by sensing platform is desirable but highly challenged in a single-response mode due to the obstacle of low precision. In this work, a novel dual-mode electrochemical - photoelectrochemical (PEC) sensor based on Cu9S8/polypyrrole/ZIF-67 (Cu9S8/PPy/ZIF-67) nanohybrid as a double signal probe was designed for highly selective detection of hydrogen sulfide. Interestingly, the as-prepared nanohybrid with excellent peroxidase - mimicking activities show remarkable electrocatalytical activity for hydrogen sulfide oxidation by using amperometric i-t. Importantly, another mode of PEC sensing platform was also constructed based on the increase of photocurrent of the modified photoactive electrodes in response to the in-situ generation of cobalt sulfide and oxidation of hydrogen sulfide. This nanohybrid-based dual-signal transduction mode hydrogen sulfide sensor provides a highly selective and relatively wide linear range for real-time tracking hydrogen sulfide levels, which will open a new pathway in bio-sensing system, clinical disease prevention and diagnosis.
       
  • A lysosome-targetable near infrared fluorescent probe for glutathione
           sensing and live-cell imaging
    • Abstract: Publication date: Available online 31 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Ziming Zheng, Yuchen Huyan, Hongjuan Li, Shiguo Sun, Yongqian Xu A novel near-infrared self-quenching dye SQSS consisting of two SQ fluorophores and a cystamine linker was constructed for the selective detection of GSH. Owing to the enhanced aggregation-caused quenching (ACQ) and FRET-mediated self-quenching effects, the background fluorescence intensity of SQSS is very weak, providing relatively high signal-to-noise ratio. The disulfide linker of SQSS can be selectively cleaved by glutathione (GSH) rather than other biothiols to produce two SQ derivatives through cooperative intermolecular hydrogen bonds and specific electrostatic interactions. The exclusive interaction of GSH with SQSS interrupt the FRET self-quenching effects between two SQ fluorophores, thereby generating a significant turn on spectral response for detection of GSH in near infrared region. Cell imaging experiments showed that SQSS can monitor endogenous and exogenous GSH in tumor or normal cells. More importantly, colocalization experiments indicated that SQSS mainly located in the lysosome, an organelle tightly associated with GSH functions. With the excellent membrane permeability and lysosome-specificity, it is convinced that SQSS will be a powerful tool in the future research on the function of GSH in lysosomes.Graphical abstractGraphical abstract for this articleA bis-squaraine dye SQSS was developed for detecting GSH with high sensitivity and selectivity and imaging of the endogenous and exogenous GSH in live cells.
       
  • Speed and Sensitivity – Integration of Electrokinetic Preconcentration
           with a Leaky Waveguide Biosensor
    • Abstract: Publication date: Available online 30 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Nicholas J. Goddard, Ruchi Gupta Improving the limit of detection by preconcentration and reducing the response time of optical biosensors are key requirements to enable their use in point of care (PoC) applications. To address these requirements, we have shown that integration of isoelectric focusing (IEF) at a pH step with a leaky waveguide (LW) sensor containing a non-specific affinity ligand (reactive blue 4 dye (RB4)) can reduce the limit of detection of an exemplar protein (bovine serum albumin (BSA)) by a factor of 600 - 930 and reduce the response time to < 60 s. This is 6 - 9 times better preconcentration and up to 16 times faster response time than previous reports. IEF was performed with standard ampholytes and with simple acids and bases forming a pH step. Using ampholytes gave good preconcentration, but was much slower than using a pH step. The LW sensor used a thin agarose hydrogel layer into which RB4 was immobilized. The dye acted both as a non-specific affinity ligand and to visualize the waveguide resonances. This allowed the refractive index of the waveguide to be monitored in real time at any point along the 10 mm separation channel length.Graphical abstractGraphical abstract for this article
       
  • Theoretical Design and Experimental Study on the Gold Nanoparticles Based
           Colorimetric Aptasensors for Detection of Neomycin B
    • Abstract: Publication date: Available online 29 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Mohammad Khavani, Mohammad Izadyar, Mohammad Reza Housaindokht Different sensors composed of aptasensor have been largely designed for detection of many analytes recently due to the ease of detection, high sensitivity, and potential for high-throughput analysis. In this article, a joint theoretical and experimental study was performed to design new gold nanoparticle based colorimetric aptasensor. At the first step, by employing molecular dynamic (MD) simulations, twenty new RNA aptamers for detection of neomycin B (NB) were theoretically designed. The sensing ability and their binding affinity of these aptamers toward NB were investigated from the theoretical viewpoint and the predicted behaviors were compared with that of the wild type aptamer (AP-W). Theoretical results indicated that two aptamers of AP-M18 and AP-M20 have a greater affinity toward NB in comparison with AP-W. At the next step, AP-M18, AP-M20 and AP-W were synthesized and their affinity and selectivity toward NB were investigated by gold nanoparticles (AuNPs) based colorimetric method. On the basis of experimental results, the calculated limit of detection (LOD) values of AP-M18 and AP-M20 are 27 and 360 nM, respectively, which are lower than that of AP-W (470 nM). Moreover, quantum chemistry calculations indicated that van der Waals and electrostatic interactions may be the driving force of the NB complexation. A greater affinity of AP-M18 against NB can be explained by the possible stronger donor-acceptor interactions. A good agreement between different predicted properties with the experimental results suggests the ability of the theoretical methods to design new aptamers for detection of various targets.Graphical Graphical abstract for this articleExperimental investigation indicates that the theoretical methods have an interesting ability for designing new aptasensors for detection of different targets.
       
  • Quality Level Identification of West Lake Longjing Green Tea using
           Electronic Nose
    • Abstract: Publication date: Available online 29 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Xiaohui Lu, Jin Wang, Guodong Lu, Bo Lin, Meizhuo Chang, Wei He China grows and consumes numerous types of tea, which have diverse processing techniques. West Lake Longjing Tea is one of the most famous and popular varieties of tea in China. It is difficult for consumers to assess the quality of Longjing green tea, as it usually requires well-trained experts to make the judgement based on colour, aroma, and taste. To this end, we propose a quality identification system consisting of a self-developed electronic nose and a data analysis algorithm to assess the quality of West Lake Longjing Tea based on its aroma. The equipment was tested extensively in experiments conducted on real-world data. The results show that the proposed system is capable of distinguishing the tea grades accurately. Furthermore, we studied the quality specifications of Longjing tea sold by different brands and found that standard certified brands have more accurate quality identification criteria than non-standard certified brands. Our findings will assist customers and tea factories in evaluating the quality of Longjing Tea and guide the optimisation of quality standards.
       
  • Multi-metal functionalized tungsten oxide nanowires enabling
           ultra-sensitive detection of triethylamine
    • Abstract: Publication date: 1 December 2019Source: Sensors and Actuators B: Chemical, Volume 300Author(s): Yongshan Xu, Tiantian Ma, Yingqiang Zhao, Lingli Zheng, Xianghong Liu, Jun Zhang Sensitization of metal oxide semiconductors is crucial for developing high performance electronic gas sensors. Herein, a unique dual sensitization protocol is proposed to boost the sensing performances of metal oxide nanowires. As a proof-of-concept, W18O49 nanowires are selected as the host materials, and Ag, Pt nanoparticles are loaded on W18O49 by an in-situ redox reaction to fabricate the novel Ag/Pt/W18O49 hybrid nanowires. Gas sensing tests demonstrate the superiority of the ternary nanowires in detecting triethylamine vapor against the binary Ag/W18O49 and Pt/W18O49 nanowires. The sensor based on Ag/Pt/W18O49 nanowires manifests fast response and recovery features and very high response over a wide concentration of 0.1–50 ppm, as well as good selectivity and stability. An ultrahigh sensitivity of 1.13 ppm−1 is registered by the Ag/Pt/W18O49 nanowires and a low detection limit of 71 ppb is obtained. The excellent performances are attributed to the dual sensitization mechanism, i.e., a synergy of both electronic and chemical interactions derived from the Ag and Pt functionalization. This work establishes a new strategy for constructing multi-metal functionalized nanowires and their utilization in functional nanodevices with enhanced performances.
       
  • Preparation and enhanced acetone sensing properties of flower-like
           α-Fe2O3/multi-walled carbon nanotube nanocomposites
    • Abstract: Publication date: 1 December 2019Source: Sensors and Actuators B: Chemical, Volume 300Author(s): Xiaohua Jia, Chuande Cheng, Shouwen Yu, Jin Yang, Yong Li, Haojie Song Hybridizing hierarchically structured α-Fe2O3 with multi-walled carbon nanotube (MWCNTs) is highly desirable for improving the performance of α-Fe2O3 based gas sensors. In this work, we developed a simple solvothermal method combined with heat treatment for the preparation of flower-like α-Fe2O3/MWCNTs nanocomposites with a flexible three-dimensional nanostructure. The characterization results showed that 4–8 μm α-Fe2O3 flower-like structures, formed by α-Fe2O3 nanosheets, were attached to the MWCNTs surface. Gas sensors based on the α-Fe2O3/MWCNTs nanocomposites exhibited a greater response, better selectivity, lower operating temperature, and good recovery towards acetone compared with pure α-Fe2O3. The response of the composites towards 50 ppm of acetone reached 20.32 at 220 °C, which was 3.49 times that of the pure α-Fe2O3 at its optimal operating temperature (260 °C). The response time of the composites towards 50 ppm acetone was 2.3 s, which was quicker than that of the pure α-Fe2O3. Overall, the gas-sensing performance of the α-Fe2O3/MWCNTs nanocomposites was enhanced. This can be assigned to the increased surface area with more active sites, improved gas transmission due to the open-frame structure, and better electrical transmission capacity due to the bridging role of the MWCNTs and the intimate α-Fe2O3-MWCNTs heterojunction.
       
  • Co-MOF-74 derived Co3O4/graphene heterojunction nanoscrolls for ppb-level
           acetone detection
    • Abstract: Publication date: 1 December 2019Source: Sensors and Actuators B: Chemical, Volume 300Author(s): Ya Xiong, Xiao Chang, Xurong Qiao, Kun Li, Lei Zhu, Fujun Xia, Xiaofang Li, Qingbin Zheng, Wei Xing, Qingzhong Xue For the first time, Co-MOF-74 derived Co3O4/graphene heterojunction nanoscrolls (Co3O4/GNS) structure is synthesized by a simple one-step hydrothermal strategy and subsequent calcination process. Theoretically, the growth mechanism of Co3O4/GNS is revealed by molecular dynamic simulation, demonstrating that a high loading of Co-MOF-74 nanoparticles is needed for effective rolling of GO. The sensor based on Co3O4/GNS exhibits high response of 58.1 (34-fold enhancement compared with that of Co3O4), short response/recovery time of 12 s/66 s (157 s/200 s for Co3O4) toward 1 ppm acetone at 190 °C and superior selectivity, which are much better than those of most reported acetone sensors. Moreover, the Co3O4/GNS can even detect as low as 50 ppb acetone with a notable response (1.24). The appreciable response together with rapid response/recovery of Co3O4/GNS is attributed to the large heterojunction interface between Co3O4 and graphene nanoscroll and high-speed gas transfer pathways provided by nanoscroll. This unique structure design is believed to offer guidance for generalizable synthesis of metal oxide/GNS that can be effectively applied in the fields of ppb-level gas detection.Graphical abstractCo-MOF-74 derived Co3O4/graphene heterojunction nanoscrolls is synthesized by hydrothermal strategy and subsequent calcination process, which can effectively detect ppb-level acetone.Graphical abstract for this article
       
  • 3D flower-like NiZnAl multimetal oxide constructed by ultra-thin porous
           nanosheets: A long-term and stable sensing material for NOx at room
           temperature
    • Abstract: Publication date: 1 December 2019Source: Sensors and Actuators B: Chemical, Volume 300Author(s): Xueying Zhang, Lei Teng, Yang Liu, Zhi Liu, Jialing Xue, Muhammad Ikram, Mohib ullah, Li Li, Keying Shi In this study, three-dimension (3D) flower-like NiZnAl ternary multimetal oxide (labeled as NZAO) with ultra-thin porous nanosheets was synthesized using a self-sacrificial template NiZnAl-LDH (marked as NZA). A series of structural and morphological characterizations confirmed that the NZAO-fabricated nanocomposites exhibited high dispersibility of metal elements, which showed microstructures of ultra-thin nanosheets (5.2–7.5 nm) and porosity (3–10 nm). Attributed by above advantages, the NZAO 1–2 sensor (Ni:Zn:Al molar ratio of 2:4:3) exhibited excellent NOx gas sensing performance at room temperature (RT, 24 °C). Its maximum response reached 9.16 for 100 ppm NOx, which was 2.74 folds of NZA 1–2 LDH. The detection limit was measured to be as low as 50 ppb. More significantly, the NZAO 1–2 sensor showed long-term stability, which could be operated over 350 days for 100 ppm NOx. These outstanding gas sensing activities could be ascribed to the unique structure constituted by ultra-thin porous nanosheets, which not only retained the original structure of the self-sacrificial template, but also formed the heterostructures in NZAO nanocomposites. Moreover, the oxygen vacancies on the ZnO (101) plane provided more active sites for gas surface adsorption.Graphical abstractThe 3D flower-like NiZnAl ternary multimetal oxide constructed by ultra-thin porous nanosheets was obtained using NiZnAl-LDH as a self-sacrificial template. The NiZnAl multimetal oxide exhibited excellent gas sensitivity to NOx due to its unique structure, especially in long-term stability (up to 350 days). This can be attributed to two points: (i) The synergistic effect of a unique 3D flower-like structure constructed by ultra-thin (5.2–7.5 nm) porous (3–10 nm) nanosheets which provide more gas passages for surface contact reactions; (ii) The heterostructure in well-dispersible NiZnAl nanocomposites, defects of ZnO (101) plane, high carrier density, chemically adsorbed oxygen (O2−) etc.. which beneficial for gas molecular diffusion and gas adsorption/desorption.Graphical abstract for this article
       
  • Tb post-functionalized La (III) metal organic framework hybrid probe for
           simple and highly sensitive detection of acetaldehyde
    • Abstract: Publication date: 1 December 2019Source: Sensors and Actuators B: Chemical, Volume 300Author(s): Jie Min, Xiang-Long Qu, Bing Yan A novel highly fluorescent hybrid system called Tb@La-MOF (Tb@{[La(hisp)(Hhisp)(H2O)2]·2H2O}n) has been synthesized via post-synthetic modification of metal-organic framework centered on inert lanthanum ion. With excellent luminescent properties, Tb@La-MOF is developed as a fluorescent probe for acetaldehyde detection, notably, it can distinguish acetaldehyde specifically from a series of other organic molecules. More importantly, water-stable Tb@La-MOF exhibits advantages like low detection limit (0.00058% for water with acetaldehyde, volume fraction), rapid response, and resistance to decompose over a wide range of pH values (3.35–11.75). Therefore, it is expected to be a promising candidate for both practical sensing on liquid acetaldehyde and simple detection of acetaldehyde vapor. Besides, the possible sensing mechanism is discussed.
       
  • High precision wide range online chemical oxygen demand measurement method
           based on ultraviolet absorption spectroscopy and full-spectrum data
           analysis
    • Abstract: Publication date: 1 December 2019Source: Sensors and Actuators B: Chemical, Volume 300Author(s): Chenxi Wang, Wanxiang Li, Meizhen Huang In this paper, a new method for high precision and wide range measurement of chemical oxygen demand (COD) based on ultraviolet absorption spectroscopy without reagent is proposed. The reasons for limiting measurement range and the main factors affecting the measurement accuracy are analyzed. A novel method of selecting different calibration wavelengths according to COD value to expand the measurement range and the turbidity compensation strategy based on full-spectrum data analysis to improve accuracy in wide measurement range are proposed and realized by an automatic wavelength selection calibration algorithm. Experiments were conducted to verify our idea with the self-developed micro UV–vis spectrophotometer (with a spectral range of 200–750 nm and a resolution of 5 nm) with a 10mm-path-length sample cell. By comparing various algorithms, the Savitzky-Golay (SG) convolution smoothing algorithm and the orthogonal signal correction (OSC) algorithm were chosen to compensate the additional absorption owing to turbidity. The experimental results show that the algorithm can automatically select the optimal characteristic wavelengths according to the spectral data and the measurement range of COD is enormously expanded from 10–150 mg/L to 1–1000 mg/L. The linear correlation coefficient (R2) of model is above 0.9995 and the relative error of measurement is less than 5%. This method can be used for in-situ and online COD measurement.
       
  • Fully-functional semi-automated microfluidic immunoassay platform for
           quantitation of multiple samples
    • Abstract: Publication date: 1 December 2019Source: Sensors and Actuators B: Chemical, Volume 300Author(s): Bo Dai, Shujing Chen, Wei Li, Lulu Zheng, Xiaodian Han, Yongfeng Fu, Jiandong Wu, Francis Lin, Dawei Zhang, Songlin Zhuang Microfluidic based enzyme-linked immunosorbent assay (ELISA) has been recognized as an advanced diagnosis tool due to the reduced sample consumption and fast reaction; but it often suffers from limited throughput and requires specialized operation skills. In this paper, we developed a microfluidic chip for multi-sample ELISA and an associated instrument for fluidic delivery and colorimetric detection. Eleven different samples can be assayed simultaneously using the developed platform in a straightforward, user-friendly, and low manual workload manner. Human interleukin-6 (IL-6) was used as the model protein biomarker to validate the platform and the estimated limit of detection (LOD) is 1.262 pg/ml. The entire assay took about 35 min, which is about six-fold shorter than the assay conducted in the traditional 96-well plate. Furthermore, we validated this platform using serum samples from 89 patients with ovarian cancer. The IL-6 concentrations in the clinical samples measured by the microfluidic platform were in good agreement with the traditional well-plate measurements. High accuracy, sensitivity and specificity of 95.5%, 96.2% and 90.9% are achieved in the testing of early-stage ovarian cancer. The semi-automated microfluidic immunoassay provides a convenient, rapid and reliable method for biomedical diagnosis.Graphical abstractGraphical abstract for this article
       
  • MOF-derived indium oxide hollow microtubes/MoS2 nanoparticles for NO2 gas
           sensing
    • Abstract: Publication date: 1 December 2019Source: Sensors and Actuators B: Chemical, Volume 300Author(s): Zhimin Yang, Dongzhi Zhang, Haonan Chen In this paper, we fabricated a metal-organic frameworks-derived indium oxide hollow microtubes/molybdenum disulfide nanoparticles (In2O3/MoS2) nanocomposite film sensor using a layer-by-layer self-assembly method. Various characterization methods such as TG, XRD, SEM, TEM, BET and XPS were applied to inspect and verify its preparation and nanostructures. The NO2-sensing characteristics of the sensors based on In2O3/MoS2 composite were systematically examined. The results showed that the response of the In2O3/MoS2 film sensor has significantly improved compared with the In2O3 sensor. More importantly, the In2O3/MoS2 sensor exhibited excellent NO2 sensing performance with a good linearity, excellent reversibility and outstanding selectivity. Finally, based on the above experimental results, we discovered that the possible sensing mechanism was ascribed to the unique structure and the synergistic effects of In2O3 hollow microtubes and MoS2 nanoparticles.
       
  • Vertically Aligned Multi-Walled Carbon Nanotubes based Flexible
           Immunosensor for extreme low level detection of Multidrug Resistant
           Leukemia Cells
    • Abstract: Publication date: Available online 28 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Payal Gulati, Prabhjot Kaur, M.V. Rajam, Tapasya Srivastava, Prabhash Mishra, S.S. Islam We report an advanced flexible immunosensor for extreme low level detection of multidrug resistant myeloid leukemia cells. The detection mechanism is analyzed in terms of novel nanoscale interactions of target molecules with vertically aligned multi-walled carbon nanotubes (VA-MWNT). The immunosensor is fabricated by transferring VA-MWNTs on a polyethylene terephthalate substrate by hot press technique without losing CNTs’ pristine character. Sensing is performed using doxorubicin treated leukemia K562 cells in varying concentrations from 1.5 × 102 cells mL–1 to 1.5 × 107 cells mL–1 and sensor showed detection limit of 10 cells mL–1. The calibration plot of peak current versus logarithmic concentration of K562 cells exhibited good linearity with a regression coefficient of ∼0.98. Sensing mechanism is explained in terms of charge transfer induced Fermi level shift of sub µeV order, causing band bending at the interface of CNT-molecular species; and it is reflected in lowering detection limit of the fabricated sensor. Theoretical analysis is done to correlate Fermi energy shift with sensitivity of the device on cancer cell immobilization. Additionally, the developed immunosensor shows good stability, reproducibility and fast detection vis-à-vis the devices reported so far. The notable advantages of proposed flexible sensor are its durability, chemical and moisture resistance, making it a potentially competitive device for point-of-care diagnostics.Graphical Graphical abstract for this article
       
  • Carbon Nanotubes Immobilized on Gold Electrode as an Electrochemical
           Humidity Sensor
    • Abstract: Publication date: Available online 28 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Han-Sem Kim, Ju Hyeon Kim, Sang-Yu Park, Ji-Hye Kang, Sung-Jin Kim, Young-Bong Choi, Ueon Sang Shin Multi-walled carbon nanotubes (MWCNTs) were fabricated on a gold electrode to develop a resistance-sensing humidity sensor with low resistance. Core-shell-structured nanohybrids were prepared using Chitosan-MWCNT to obtain good hydrophilicity, resulting in a highly responsive humidity sensor. We also measured resistance, which changes due to hydrogen bonding between the amine group of chitosan and H2O. The structure of the fabricated chitosan-MWCNT core–shell-structured nanohybrid was measured. Furthermore, we determined the highest response and linearity of the CS-MWCNT25 nanohybrids based on the number of coats on the electrode and the composition ratio of chitosan and MWCNTs. The fabricated CS-MWCNT25 nanohybrid humidity sensor exhibited good electrical efficiency without voltage or frequency dependence and a low-temperature dependency with a temperature coefficient (RH/°C) of 0.187%. Finally, a fast recovery time of 40 s between 30% and 100% RH, a maximum humidity hysteresis of less than 0.300 ± 0.001%, and long-term stability for 2 months indicated that this is an excellent humidity sensor.Graphical abstractGraphical abstract for this article
       
  • Ultrasensitive amperometric cytosensor for drug evaluation with monitoring
           early cell apoptosis based on Cu2O@PtPd nanocomposite as signal amplified
           label
    • Abstract: Publication date: Available online 28 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Jin-Xia Liu, Xiu-Li Liang, Feihong Chen, Shou-Nian Ding It is significant to monitor the early stage of apoptosis and evaluate the therapeutic effect of anticancer drugs in the diagnostic of cancer. Here, an electrochemical cytosensor with signal amplified strategy was constructed to quantitatively detect the concentration of early apoptotic cells and respond to therapy of anticancer drugs. To fabricate the platform, cuprous oxide (Cu2O) cube was utilized as a large platform for loading platinum-palladium nanoparticles (PtPd NPs) to prepare the Cu2O@PtPd nanocomposites. The formed nanocomposite was not only acted as signal amplified molecules towards the reduction of H2O2 by synergistic effect but also possessed large specific area to conjugate concanavalin A (Con A), which specifically interacted with the cell-surface carbohydrate. What’s more, the porous graphene oxide-Au (PGO-Au) nanocomposites were modified onto working electrode to improve the efficiency of electron transfer. Meanwhile, the PGO-Au nanocomposite was served as effective matrix to couple annexin V through Au-N bond to capture apoptotic cells owing to the specific interaction between phosphatidylserine (PS) on the cell surface and annexin V. In this system, A549 cell was chosen as model cells and cisplatin acted as apoptotic inducer. The proposed amperometric cytosensor exhibited a wide range detection of early apoptotic cells from 50 to 5 × 107 cells mL-1. Meanwhile, the detection limit was down to 20 cells mL-1. It also showed high specificity, acceptable sensitivity and good reproducibility, which had promising potential for the early evaluation of therapeutic effect.
       
  • Fabrication of 3D ordered mesoporous ball-flower structures ZnO material
           with the excellent gas sensitive property
    • Abstract: Publication date: Available online 28 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yuan-yuan Li, Hui Yu, Ying Yang, Xiang-ting Dong In this study, a kind of unfamiliar 3D ball-flower morphology ZnO was prepared through a facile and low cost hydrothermal reaction method which was assembled with 50 nm thickness ZnO nanosheets. A kind of ordered mesoporous ZnO material must be used as precursor in hydrothermal reaction which was prepared by soft template method. The surfaces of the ball-flower morphology ZnO were distributed with 5.2 nm wide ordered mesoporous, which led to the bigger specific surface area in the material, it reached to 108.69 m2 g-1. The morphology, structure and gas sensing performance toward NOx of the prepared material were tested, and the optimum synthesis conditions were determined. At room temperature (25℃), the ball-flower ZnO nanomaterial showed the excellent gas response to NOx, whose response to 100 ppm NOx gas reached 68.9 %, the response time was only 6 s, and the detection limit was 1 ppm. It broke the tradition that the pure ZnO showed gas response to NOx only in relatively high temperatures.Graphical abstractGraphical abstract for this article
       
  • Gas sensitive ZnO structures with reduced humidity-interference
    • Abstract: Publication date: Available online 28 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): S. Vallejos, I. Gràcia, N. Pizúrová, E. Figueras, J. Čechal, J. Hubálek, C. Cané Gas microsensors based on zinc oxide structures with rod- and needle-like morphology, both integrated via a non-catalyzed vapor-solid mechanism enabled using aerosol-assisted chemical vapor deposition, are developed. Analysis of the films via SEM, TEM, XPS, and water contact angle indicate a higher concentration of oxygen vacancies, higher aspect ratio and higher roughness factor for the needles respect to the rods. Gas sensing tests towards hydrogen and carbon monoxide demonstrate reduced humidity-interference, and higher responses to the analytes for the needle-based systems compared to the rods. These results are attributed to the morphology of the sensitive materials, which not only affects the surface-area-to-volume-ratio of the films but also their surface chemistry. These findings indicate that a thorough optimization of morphology, structure and surface properties of gas sensitive metal oxides could allow for more reliable sensor operation in humid conditions.
       
  • Colorimetric probe for Ni2+ based on shape transformation of triangular
           silver nanoprisms upon H2O2 etching
    • Abstract: Publication date: Available online 28 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Su-Jin Yoon, Yun-Sik Nam, Ho-Jin Lee, Yeonhee Lee, Kang-Bong Lee In this article, a highly sensitive and selective colorimetric method for the detection of Ni2+ ions is presented on the basis of hydrogen peroxide etching of triangular silver nanoprisms (AgNPrs). Triangular AgNPrs were synthesized by a modified seed-mediated growth method, and upon addition of Ni2+ ions these triangular AgNPrs showed a significant colorimetric change from blue to reddish brown, and eventually yellow to as a function of the Ni2+ ion concentration. Ni2+ ion do not act as a selective etchant to triangular AgNPrs, but instead serve as a catalyst for the generation of H2O2 in a citrate-capped triangular AgNPr colloidal solution. The oxidative etching with H2O2 formed in the colloidal solution sculptured the sharp corners/edges of the triangular AgNPrs to produce circular Ag nanodisk. Selectivity tests for Ni2+ ions by the triangular AgNPr probe were performed in the presence of other various cations and anions at the optimized conditions (pH 8, 15 °C, and 30 min of reaction time). The probe showed a high linearity between absorption ratio (A475/A750) and concentration in the range of 0 to 30 μM of Ni2+, with a limit of detection of 21.6 nM in aqueous solution. The color and UV-vis absorption spectrum of the triangular AgNPr probe indicated that it is quite stable for two weeks in ambient temperature and pH ranges of 4.0∼10.0. This triangular AgNPr probe was successfully employed for the detection of Ni2+ ions in spiked tap and pond water samples.Graphical Graphical abstract for this article
       
  • A novel fluorescent recombinant cell-based biosensor for screening NLRP3
           inflammasome inhibitors
    • Abstract: Publication date: Available online 28 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yongli Ye, Kaiqin Liu, Shuxiang Geng, Jian Ji, Jiadi Sun, Yinzhi Zhang, Fuwei Pi, Xiulan Sun Nucleotide-binding oligomerization domain-like receptor pyrin-domain-containing protein 3 (NLRP3) inflammasomes trigger a defense mechanism in response to physiological or pathological reactions caused by various injuries, and they have critical roles in the development of many major diseases. The development of plant source anti-inflammatory agents and the assessment of their anti-inflammatory properties still face many challenges, such as high costs and long testing periods. Exogenous anti-inflammatory factors can be evaluated at the protein level using the NLRP3-green fluorescent protein (GFP) THP-1 cell-based biosensor. To achieve this, THP-1 cells were stably transfected with a plasmid encoding the GFP reporter gene that is under the transcriptional regulation of the NLRP3 promoter. Because the NLRP3 promoter controls the green fluorescent signal, the fluorescence is an indicator of NLRP3 activity. Our results show the fluorescence intensity was dependent on both the degree of inflammation and the effect of the anti-inflammatory agent. Here, we successfully used the biosensor to screen an NLRP3 inhibitor in the presence of polyphenols. Our results demonstrate the potential of this cell-based biosensor in monitoring the development of inflammation and in screening inflammatory inhibitors.
       
  • Improved CO gas detection of Si MOSFET gas sensor with catalytic Pt
           decoration and pre-bias effect
    • Abstract: Publication date: Available online 27 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Seongbin Hong, Yoonki Hong, Yujeong Jeong, Gyuweon Jung, Wonjun Shin, Jinwoo Park, Jung-Kyu Lee, Dongkyu Jang, Jong-Ho Bae, Jong-Ho Lee This paper investigates carbon monoxide (CO) gas sensing performance in a silicon metal-oxide semiconductor field effect transistor (Si MOSFET)-based gas sensor having a structure in which a floating-gate (FG) and a control-gate (CG) are interdigitated in a horizontal direction. The sensing material, indium oxide (In2O3) nanoparticles, is formed by an inkjet printing process between the FG covered with an insulator stack and exposed CG. Decorating the sensing layer with catalytic Pt and applying pulsed pre-bias are introduced as a method to improve CO gas sensing characteristics of the MOSFET sensor. First, CO gas sensing performance with Pt concentration and operating temperature is studied. The sensing performance is measured at 200 °C mainly by applying pulses to the CG. The response, response and recovery times of the MOSFET sensor are significantly enhanced with catalytic Pt decoration. In this work, 5% Pt decoration shows the best sensing characteristics. Response and recovery times are improved by 65% and 70%, by applying a pre-bias of 2 V and −2 V to the CG during response and recovery, respectively.
       
  • Effects of Pt loading onto SnO2 electrodes on CO-sensing properties and
           mechanism of potentiometric gas sensors utilizing an anion-conducting
           polymer electrolyte
    • Abstract: Publication date: Available online 27 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Takeo Hyodo, Toshiyuki Goto, Mari Takamori, Taro Ueda, Yasuhiro Shimizu Gas-sensing properties of electrochemical CO sensors utilizing Pt-loaded SnO2 electrodes and an anion-conducting polymer electrolyte have been investigated mainly at 30 °C in wet synthetic air (57%RH), and the effects of the Pt loading onto SnO2 on the CO-sensing properties and their CO-sensing mechanism have been discussed in this paper. The amount of Pt loaded onto SnO2 (0.5–5.0 wt%) and the subsequent heat-treatment at 500 °C in air were effective in enhancing the CO responses and the CO selectivity against H2. The sensing-electrode potential was governed by mixed potential resulting from electrochemical CO (or H2) oxidation and O2 reduction, and all the results obtained indicated that the oxidation rate of CO molecules was electrochemically quite faster than that of H2 molecules on the mono-dispersive and oxidized Pt species as an active site, which were doped at the surface SnO2 lattice. On the other hand, the heat treatment at 250 °C in H2 after the Pt loading reduced the surface of Pt-loaded SnO2 and drastically enhanced both CO and H2 responses and thus decreased the CO selectivity against H2. This effect arose probably from the reduced Pt species with metallic surface, which were quite active against both CO and H2 anodic reactions.
       
  • An automatic smart measurement system with signal decomposition to
           partition dual-source CO2 flux from maize silage
    • Abstract: Publication date: Available online 27 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Guilin Shan, Wolfgang Buescher, Christian Maack, Haiyang Zhou, David A. Grantz, André Lipski, Ismail-Hakki Acir, Yurui SunABSTRACTCarbon dioxide (CO2) is a principal byproduct of various chemical, biological and biochemical processes. CO2 has been measured using various advanced sensors, but a limiting technical challenge has been resolving independent streams of CO2 produced by processes occurring simultaneously. The magnitude and kinetics of each stream may be chemically, biologically or/and physically informative, but such partitioning has received little attention and successful case studies remain rare. In silage production, CO2 flux, an important indicator of aerobic deterioration, microbial activity or oxidative rate of silage, derives from two different pools: gas accumulated in the pores during the early anaerobic phase, and current real-time production of CO2 as oxygenated air enters the silage across the exposed face after opening for feed-out. The former is regarded as a noise confounding the signal and the latter reflects current degradation of the silage. Using a self-developed automatic sensor system with novel signal decomposition, we successfully partitioned CO2 flux into two independent streams derived from the two distinct pools in maize silage, following two independent processes: a physical venting of stored gas through a tortuous diffusive pathway, and a biochemical process generating gas in real time. Three silage samples, treated with a chemical or a biological additive, or left untreated, were tested. The signal decomposition found two best-fit functions (0.8034 ≤ R2 ≤ 0.9036), a quadratic CO2 discharge function and an exponential CO2 production function, for characterizing these distinct processes. These results demonstrate chemical sensor with powerful data-processing capability to resolve the complexity of dual-pool CO2 emission.
       
  • Highly Selective Electroanalysis for Chloride Ions by Conductance Signal
           Outputs of Solid-State AgCl Electrochemistry Using Silver-Melamine
           Nanowires
    • Abstract: Publication date: Available online 27 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yuqi Wan, Yue Hua, Min Liu, Shuai Li, Mengyuan Yin, Xiaoxia Lv, Hua Wang Silver (Ag)-melamine (MA) nanowires were fabricated by the controlled supramolecular self-assembly with conductive hollow Q-graphene (QG) scaffolds to be modified onto the electrodes for sensing chloride ions. Once adding Cl- ions, the QG@MA-Ag modified electrodes, which might otherwise display an Ag oxidization peak at about 0.29 V, could exhibit stable and sharp peaks of solid-state Ag/AgCl electrochemistry at lowering potentials approaching to zero. Moreover, both of the Cl- responses of currents (I) and voltages (V) could vary rationally depending on Cl- concentrations. The responses in conductance (I/V) were thereby conversed alternatively as the signal outputs to ensure the highly selective detection of Cl- ions, with no significant interference from other kinds of halogen ions. The as-developed electroanalysis strategy can facilitate the evaluation of Cl- ions over a broad linear concentration range of 0.25 μM - 250 mM, with the detection limit down to 0.16 μM. The feasibility of the chloride sensor was subsequently demonstrated in probing Cl- ions separately in sweat and hela cells. Such a detection method with the signal outputs of conductance may feature a new electroanalysis format tailored for highly selective and ultrasensitive analysis of trace-level Cl- ions for the early diagnosis of chloride-indicative diseases.
       
  • A Fluoroimmunodiagnostic Nanoplatform for Thyroglobulin Detection Based on
           Fluorescence Quenching Signal
    • Abstract: Publication date: Available online 27 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Eylem Turan, Ferat Şahin, Zekiye Suludere, Hayrettin Tümtürk This study describes the design of a novel fluoroimmunodiagnostic nanoplatform by using tannylated ferritin nanocages (TA-Fn). The tannylation process ensured the tannic acid was modified onto the ferritin nanocages without EDC, NHS or any reagents. The bare ferritin nanocages (Fn) had about 5.6 ± 0.14 nm average diameter, while tannylated ferritin nanocages had an estimated layer thickness of about 24 ± 2.2 nm. The FITC labelled thyroglobulin antibodies (FITC-TgAb) were conjugated to TA-Fn via multiple hydrogen bonds and hydrophobic interactions. The FITC labelled TgAb modified tannylated ferritin nanocages (FITC-TgAb-TA-Fn) had an estimated layer thickness of about 32 ± 3.1 nm. The FITC-TgAb-TA-Fn had good selectivity and specificity to rapidly capture and detect specific antigens via fluorescence quenching with relatively low-cost engineering. The Stern-Volmer plot was used to obtain limit of detection (LOD) and limit of quantification (LOQ). The LOD was 4.3 pg mL-1 and LOQ was 14.2 pg mL-1 in artificial human serum medium. These values were lower than the thyroglobulin detection limit with modern assays.
       
  • Development of a hydrophilic molecularly imprinted polymer for the
           detection of hydrophilic targets using quartz crystal microbalance
    • Abstract: Publication date: Available online 27 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Hiranya Dayal, Wan Yi Ng, Xuan Hao Lin, Sam Fong Yau Li In this study, we describe the development and applicability of a molecularly imprinted polymer (MIP) based on the facile modification of a hydrophobic polymer, poly(vinylidene difluoride) (PVDF), in a sensor for the detection of trichlorfon (TCF) as a representative hydrophilic organophosphate pesticide. This sensor was developed from its polymer as opposed to conventional in-situ polymerization methods. The performance of the TCF MIP sensor was evaluated using a quartz crystal microbalance (QCM) achieving a good linear response between 0 – 250 ppb and a limit of detection (LOD) of 4.63 ppb and a limit of quantitation (LOQ) of 15.77 ppb. The sensor demonstrated high selectivity in the presence of structural analogues including dimethoate, acephate, dichlorvos, malathion as well as carbaryl and carbosulfan. The sensor was also found to have satisfactory stability when monitored over a 20-day period. The developed method was successfully applied to detect TCF in spiked lettuce samples. The novelty of the proposed method lies in the assimilation of concepts from membrane modification into MIP sensor fabrication and demonstrates the possibility of utilizing polymers directly for a simple yet effective sensor development.Graphical abstractGraphical abstract for this article
       
  • Pt-Cr2O3-WO3 composite nanofibers as gas sensors for ultra-high sensitive
           and selective xylene detection
    • Abstract: Publication date: Available online 23 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Changhao Feng, Zhongwei Jiang, Wu Jingxuan, Bin Chen, Lu Geyu, Chengzhi Huang In this work, Pt-Cr2O3-WO3 composite nanofibers have been designed by using Pt@MIL-101(Cr) and electrospinning. The morphological and microstructural properties of these nanofibers were analyzed by various kinds of techniques. The FESEM and TEM results demonstrate that the size of Pt nanoparticles is ˜ 3 nm, which greatly improved the gas sensing properties of metal oxides. The gas-sensing properties of WO3, Cr2O3-WO3 and Pt-Cr2O3-WO3 composite nanofibers were tested. Compared with pristine WO3 nanofibers, Pt-Cr2O3-WO3 composite nanofibers exhibit superior response toward xylene. At the optimal operating temperature of 325 °C, the response of Pt-Cr2O3-WO3 composite nanofibers to 10 ppm xylene is 74.3, the response time is 5 s and the detection limit is 5 ppm. The sensing mechanism of the ultrahigh gas sensing properties attributes to the Cr2O3-WO3 heterojunction, the catalytic activity of Cr2O3, porous structure, the electronic and chemical sensitization of Pt nanoparticles.
       
  • Beyond common analytical limits of radicals detection using the functional
           SERS substrates
    • Abstract: Publication date: Available online 22 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): O. Guselnikova, P. Postnikov, S.R.A. Marque, V. Švorčík, O. Lyutakov In this work, we present the novel analytical procedure for the detection of the radicals in the analytical solutions with an unprecedented detection limit and versatility. The proposed procedure is based on the grafting of stable 2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO) radical to the surface of the SERS-active gold grating. The presence of radicals in the analytical solution induces the conversion of grafted TEMPO to N-oxoammonium salt accompanied by the appropriate peak shifts in SERS spectra. Observed changes of SERS spectra makes possible to detect the presence of radicals down to 10-10 M concentration, far exceeding the sensitivity of common analytical methods. Proposed highly regular plasmonic background providing homogeneous distribution of electric field enhancement together with used surface decoration procedure ensuring uniform distribution of grafted TEMPO molecules, result in perfect SERS results reproducibility. Finally, the regeneration of SERS substrate was also demonstrated which is essential for repeated use of created SERS chips in radical’s detection.
       
  • Facile tilted sputtering process (TSP) for enhanced H2S gas response over
           selectively loading Pt nanoparticles on SnO2 thin Films
    • Abstract: Publication date: Available online 20 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Nu Si A Eom, Hong-Baek Cho, Hyo-Ryoung Lim, Bum Sum Kim, Yong-Ho Choa In this paper, we present an enhanced H2S gas sensor based on selectively loading Pt nanocatalyst on the lateral surface of vertically aligned SnO2 thin film with nano-protrusion at a low temperature of 150℃. For this purpose, a facile tilted sputtering process (TSP) to form a new, high surface area hierarchical nanostructure is proposed and envisaged in H2S gas sensor materials at different sensing temperatures. The vertically well aligned semiconductor tin dioxide (SnO2) nanostructured films with average nanorods with diameters ranging from 70˜150 nm has been synthesized in which the diameter of the nanorods can be controlled by adjusting the spray pyrolysis deposition time and temperature. The inherent difficulty of detecting H2S gas at temperature lower than 200℃ with pure SnO2, were overcome by utilizing Pt/ SnO2 thin films, which was synthesized via TSP. The Pt-SnO2 thin films with hierarchical nanostructure enhanced H2S gas response by a factor of 2 and the detection limit as low as 10 ppm compared to the thorough Pt loaded metal oxide at 150℃. The adsorption sites of dissolved oxygen and analyte gas in relation to a TSP induced-Pt layers are elucidated for the enhanced H2S gas response. This work provides a simple, controllable approach that can be extended to the synthesis of other catalyst metal-loaded nanostructures based on metal oxides as gas sensor materials.
       
  • Sandwich-type signal-off photoelectrochemical immunosensor based on dual
           suppression effect of PbS quantum dots/Co3O4 polyhedron as signal
           amplification for procalcitonin detection
    • Abstract: Publication date: Available online 19 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yanrong Qian, Jinhui Feng, Huan Wang, Dawei Fan, Na Jiang, Qin Wei, Huangxian Ju A novel signal-off photoelectrochemical (PEC) immunosensor was proposed for procalcitonin (PCT) sensitive detection based on the Au nanoparticles/BiOI nanosheets/Black TiO2 nanoparticles (Au NPs/BiOI NSs/B-TiO2 NPs) as photoactive matrix and PbS quantum dots/Co3O4 polyhedron (PbS/Co3O4) as a quenching signal label for signal amplification. Concretely, BiOI NSs was fabricated by successive ionic layer absorption and reaction (SILAR) and formed the interlaced flake-like structure. Then Au NPs dropped on the BiOI NSs/B-TiO2 NPs electrode forming Au NPs/BiOI NSs/B-TiO2 NPs sensitization structure, which increased the utilization of visible light and accelerated electron transfer rate, resulting in a desirable PEC signal. PbS/Co3O4, an effective dual suppression signal quencher, was proposed for signal-off PEC immunosensor to weaken the photocurrent response because of the steric impedance, competitive absorption of light and competing consumption of electron donor. In this proposal, PCT was chosen to measure the performance of the suggested PEC immunosensor. Consequently, the fabricated PEC immunosensor showed a widely detection ranged from 0.1 pg/mL to 50 ng/mL and a low detection limit of 0.02 pg/mL (S/N = 3). What is more, the proposed PEC immunosensor possessed satisfactory selectivity, stability and reproducibility.
       
  • A selective molecularly imprinted electrochemical sensor with GO@COF
           signal amplification for the simultaneous determination of sulfadiazine
           and acetaminophen
    • Abstract: Publication date: Available online 17 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): Yufeng Sun, Jingbo He, Geoffrey I.N. Waterhouse, Longhua Xu, Hongyan Zhang, Xuguang Qiao, Zhixiang Xu In this work, the development of a simple and sensitive electrochemical sensor for the simultaneous determination of sulfadiazine (SDZ) and acetaminophen (AP) is described. The sensor harnessed a molecularly imprinted polymer (MIP) for selective recognition of SDZ and AP, and a graphene oxide@covalent organic framework (GO@COF) nanocomposite for signal amplification. The GO@COF nanocomposite was first immobilized on a glassy carbon electrode (GCE), after which a polypyrrole MIP was electrodeposited on the modified electrode. The resulting electrochemical sensor (denoted as MIP/GO@COF/GCE) showed a strong current response to both SDZ and AP in phosphate buffer at pH 7.0. Under optimal testing conditions, linear calibration curves were obtained over the concentration range 0.5-200 μM for SDZ and 0.05-20 μM for AP, with limits of detection being 0.16 μM and 0.032 μM, respectively. Beef and fodder samples spiked with SDZ and AP were extracted in ethyl acetate, then the SDZ and AP in the extracts quantified using the MIP/GO@COF/GCE sensor. Recoveries were excellent, ranging from 82.0-108.0 %. The same method was also employed to determine SDZ and AP residues in pork and chicken samples, with the results correlating well with those obtained using high-performance liquid chromatography.Graphical Graphical abstract for this article
       
  • C2H5OH sensing properties of solid-state mediated
           BiOBr nanoplates
    • Abstract: Publication date: Available online 17 August 2019Source: Sensors and Actuators B: ChemicalAuthor(s): S.T. Navale, Q. Huang, P. Cao, V.B. Patil, F.J. Stadler In present work, hierarchical bismuth oxybromide nanoplates (BiOBr NPs) have been synthesized rapidly through a simple solid-state reaction method without any template/surfactant/additives at room temperature and utilized it as gas sensing materials. Various techniques were used to characterize the structure, composition, and morphology of as-synthesized BiOBr products. Structural and compositional analysis supports to crystalline tetragonal configuration of BiOBr NPs. A compact arrangement of BiOBr NPs, with ˜600 nm length and width of ˜300 nm, was confirmed through morphological study. Gas sensing measurements on as-fabricated BiOBr NPs sensors were performed towards different target gases thoroughly and discussed. The sensors based on solid-state processed BiOBr NPs are responsive (Ra/Rg = 11.40, 1000 ppm) towards C2H5OH at 300 °C together with excellent response reversibility kinetics. Nanoplate-type BiOBr structure offers a specific surface area of 18.29 m2/g to enhance the exposed surface sites for the chemisorption of C2H5OH gas molecules and contributed in higher response. This work provides a rapid, easy, and efficient mode to fabricate BiOBr NPs, which can be applied to synthesize other oxide structures too, for the application of sensitive C2H5OH gas sensors.Graphical abstractGraphical abstract for this article
       
 
 
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