Open AccessArticle
Design of an Affibody-Based Recognition Strategy for Human Epidermal Growth Factor Receptor 2 (HER2) Detection by Electrochemical Biosensors
Chemosensors 2016, 4(4), 23; doi:10.3390/chemosensors4040023 (registering DOI) -
Abstract
In this study, we have designed and realized three simple electrochemical bioassays for the detection of the human epidermal growth factor receptor 2 (HER2) cancer biomarker using magnetic beads coupling screen-printed arrays. The different approaches were based on a sandwich format in which
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In this study, we have designed and realized three simple electrochemical bioassays for the detection of the human epidermal growth factor receptor 2 (HER2) cancer biomarker using magnetic beads coupling screen-printed arrays. The different approaches were based on a sandwich format in which affibody (Af) or antibody (Ab) molecules were coupled respectively to streptavidin or protein A-modified magnetic beads. The bioreceptor-modified beads were used to capture the HER2 protein from the sample and sandwich assay was performed by adding the labeled secondary affibody or the antibody. An enzyme-amplified detection scheme based on the coupling of secondary biotinylated bioreceptor with streptavidin-alkaline phosphatase enzyme conjugate was then applied. The enzyme catalyzed the hydrolysis of the electro-inactive 1-naphthyl-phosphate to the electro-active 1-naphthol, which was detected by means of differential pulse voltammetry (DPV). Each developed assay has been studied and optimized. Furthermore, a thorough comparison of the analytical performances of developed assays was performed. Finally, preliminary experiments using serum samples spiked with HER2 protein were also carried out. Full article
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Open AccessArticle
Development and Application of Electrochemical Sensor Based on Molecularly Imprinted Polymer and Carbon Nanotubes for the Determination of Carvedilol
Chemosensors 2016, 4(4), 22; doi:10.3390/chemosensors4040022 -
Abstract
This work describes the preparation of a glassy carbon electrode (GCE) modified with molecularly imprinted polymer (MIP) and multiwalled carbon nanotubes (MWCNTs) for determination of carvedilol (CAR). Electrochemical behavior of CAR on the modified electrode was evaluated using cyclic voltammetry. The best composition
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This work describes the preparation of a glassy carbon electrode (GCE) modified with molecularly imprinted polymer (MIP) and multiwalled carbon nanotubes (MWCNTs) for determination of carvedilol (CAR). Electrochemical behavior of CAR on the modified electrode was evaluated using cyclic voltammetry. The best composition was found to be 65% (m/m) of MIP. Under optimized conditions (pH 8.5 in 0.25 mol L−1 Britton–Robinson buffer and 0.1 mol L−1 KCl) the voltammetric method showed a linear response for CAR in the range of 50–325 µmol L−1 (R = 0.9755), with detection and quantification limits of 16.14 µmol L−1 and 53.8 µmol L−1, respectively. The developed method was successfully applied for determination of CAR in real samples of pharmaceuticals. The sensor presented good sensitivity, rapid detection of CAR, and quick and easy preparation. Furthermore, the material used as modifier has a simple synthesis and its amount utilized is very small, thus illustrating the economic feasibility of this sensor. Full article
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Open AccessArticle
Molecularly Imprinted Quartz Crystal Microbalance Sensor (QCM) for Bilirubin Detection
Chemosensors 2016, 4(4), 21; doi:10.3390/chemosensors4040021 -
Abstract
This study aims the preparation of a QCM sensor for the detection of bilirubin in human plasma. Bilirubin-imprinted poly-(2-hydroxyethyl methacrylate-N-methacryloyl-l-tryptophan methyl ester) (PHEMATrp) nanofilm (MIP) on the gold surface of a QCM chip was synthesized by the molecular imprinting technique. Meanwhile,
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This study aims the preparation of a QCM sensor for the detection of bilirubin in human plasma. Bilirubin-imprinted poly-(2-hydroxyethyl methacrylate-N-methacryloyl-l-tryptophan methyl ester) (PHEMATrp) nanofilm (MIP) on the gold surface of a QCM chip was synthesized by the molecular imprinting technique. Meanwhile, the non-imprinted PHEMATrp (NIP) nanofilm was synthesized by the same experimental technique to examine the imprinting effect. Characterization of MIP and NIP nanofilms on the QCM chip surface was achieved by atomic force microscopy (AFM), ellipsometry, Fourier transform infrared spectrophotometry-attenuated total reflectance (FTIR-ATR) and contact angle measurements (CA). The observations indicated that the nanofilm was almost in a monolayer. Thereinafter, the imprinted and the non-imprinted QCM chips were connected to the QCM system to investigate kinetic and affinity properties. In order to examine the selectivity of the MIP-PHEMATrp nanofilm, competitive adsorption of bilirubin with cholesterol and estradiol was performed. Limit of detection (LOD) and limit of quantitation (LOQ) values were calculated as 0.45 μg/mL and 0.9 μg/mL, respectively. Full article
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Open AccessReview
Recent Trends in Field-Effect Transistors-Based Immunosensors
Chemosensors 2016, 4(4), 20; doi:10.3390/chemosensors4040020 -
Abstract
Immunosensors are analytical platforms that detect specific antigen-antibody interactions and play an important role in a wide range of applications in biomedical clinical diagnosis, food safety, and monitoring contaminants in the environment. Field-effect transistors (FET) immunosensors have been developed as promising alternatives to
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Immunosensors are analytical platforms that detect specific antigen-antibody interactions and play an important role in a wide range of applications in biomedical clinical diagnosis, food safety, and monitoring contaminants in the environment. Field-effect transistors (FET) immunosensors have been developed as promising alternatives to conventional immunoassays, which require complicated processes and long-time data acquisition. The electrical signal of FET-based immunosensors is generated as a result of the antigen-antibody conjugation. FET biosensors present real-time and rapid response, require small sample volume, and exhibit higher sensitivity and selectivity. This review brings an overview on the recent literature of FET-based immunosensors, highlighting a diversity of nanomaterials modified with specific receptors as immunosensing platforms for the ultrasensitive detection of various biomolecules. Full article
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Open AccessArticle
Fungi Active Microbial Metabolism Detection of Rhizopus sp. and Aspergillus sp. Section Nigri on Strawberry Using a Set of Chemical Sensors Based on Carbon Nanostructures
Chemosensors 2016, 4(3), 19; doi:10.3390/chemosensors4030019 -
Abstract
We use a set of three resistive sensors based on undoped multi-walled carbon nanotubes, B-doped multi-walled carbon nanotubes, and N-doped multi-walled carbon nanotubes to study fungal infection in strawberries inoculated with Rhizopus sp. or with Aspergillus sp. section Nigri. We apply tristimulus
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We use a set of three resistive sensors based on undoped multi-walled carbon nanotubes, B-doped multi-walled carbon nanotubes, and N-doped multi-walled carbon nanotubes to study fungal infection in strawberries inoculated with Rhizopus sp. or with Aspergillus sp. section Nigri. We apply tristimulus analysis using the conductance variation of the sensors when exposed to the infected strawberries to distinguish between uninfected strawberries and strawberries infected with Rhizopus sp. or with Aspergillus sp. section Nigri, and to obtain a graphical representation providing a tool for the simple and fast detection and identification of the fungal infection. Full article
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Open AccessArticle
Miniaturized Aptamer-Based Assays for Protein Detection
Chemosensors 2016, 4(3), 18; doi:10.3390/chemosensors4030018 -
Abstract
The availability of devices for cancer biomarker detection at early stages of the disease is one of the most critical issues in biomedicine. Towards this goal, to increase the assay sensitivity, device miniaturization strategies empowered by the employment of high affinity protein binders
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The availability of devices for cancer biomarker detection at early stages of the disease is one of the most critical issues in biomedicine. Towards this goal, to increase the assay sensitivity, device miniaturization strategies empowered by the employment of high affinity protein binders constitute a valuable approach. In this work we propose two different surface-based miniaturized platforms for biomarker detection in body fluids: the first platform is an atomic force microscopy (AFM)-based nanoarray, where AFM is used to generate functional nanoscale areas and to detect biorecognition through careful topographic measurements; the second platform consists of a miniaturized electrochemical cell to detect biomarkers through electrochemical impedance spectroscopy (EIS) analysis. Both devices rely on robust and highly-specific protein binders as aptamers, and were tested for thrombin detection. An active layer of DNA-aptamer conjugates was immobilized via DNA directed immobilization on complementary single-stranded DNA self-assembled monolayers confined on a nano/micro area of a gold surface. Results obtained with these devices were compared with the output of surface plasmon resonance (SPR) assays used as reference. We succeeded in capturing antigens in concentrations as low as a few nM. We put forward ideas to push the sensitivity further to the pM range, assuring low biosample volume (μL range) assay conditions. Full article
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Open AccessTechnical Note
A Low-Cost Label-Free AFB1 Impedimetric Immunosensor Based on Functionalized CD-Trodes
Chemosensors 2016, 4(3), 17; doi:10.3390/chemosensors4030017 -
Abstract
This work describes the investigation of a label-free immunosensor for the detection of aflatoxin B1 (AFB1). CD-trodes (electrodes obtained from recordable compact disks) were used as low-cost and disposable transducers after modification with a self-assembled monolayer (SAM) of lipoic acid.
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This work describes the investigation of a label-free immunosensor for the detection of aflatoxin B1 (AFB1). CD-trodes (electrodes obtained from recordable compact disks) were used as low-cost and disposable transducers after modification with a self-assembled monolayer (SAM) of lipoic acid. The anti-aflatoxin B1 antibody was immobilized via EDC/NHS activation, followed by blocking with bovine serum albumin and immunoassays with AFB1. The optimization of analytical parameters and the detection were carried out using electrochemical impedance measurements. Using chemometric tools, the best conditions for the immunosensor development were defined as: anti-AFB1 antibody at 1:2000 dilution and surface blocking with 0.5% bovine serum albumin, both incubated for 1 h, and antibody–antigen immunoreaction for 30 min. The impedimetric immunosensor showed a linear range from 5 × 10−9 to 1 × 10−7 mol·L−1 (1.56–31.2 ng·mL−1), limit of detection and limit of quantification, respectively, 3.6 × 10−10 and 1.1 × 10−9mol·L−1 (0.11 and 0.34 ng·mL−1). The proposed immunosensor was applied to analyze peanut samples. Full article
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Open AccessArticle
Unique Properties of Core Shell Ag@Au Nanoparticles for the Aptasensing of Bacterial Cells
Chemosensors 2016, 4(3), 16; doi:10.3390/chemosensors4030016 -
Abstract
In this article, it is shown that the efficiency of an electrochemical aptasensing device is influenced by the use of different nanoparticles (NPs) such as gold nanoparticles (Au), silver nanoparticles (Ag), hollow gold nanospheres (HGN), hollow silver nanospheres (HSN), silver–gold core shell (Ag@Au),
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In this article, it is shown that the efficiency of an electrochemical aptasensing device is influenced by the use of different nanoparticles (NPs) such as gold nanoparticles (Au), silver nanoparticles (Ag), hollow gold nanospheres (HGN), hollow silver nanospheres (HSN), silver–gold core shell (Ag@Au), gold–silver core shell (Au@Ag), and silver–gold alloy nanoparticles (Ag/Au). Among these nanomaterials, Ag@Au core shell NPs are advantageous for aptasensing applications because the core improves the physical properties and the shell provides chemical stability and biocompatibility for the immobilization of aptamers. Self-assembly of the NPs on a cysteamine film at the surface of a carbon paste electrode is followed by the immobilization of thiolated aptamers at these nanoframes. The nanostructured (Ag@Au) aptadevice for Escherichia coli as a target shows four times better performance in comparison to the response obtained at an aptamer modified planar gold electrode. A comparison with other (core shell) NPs is performed by cyclic voltammetry and differential pulse voltammetry. Also, the selectivity of the aptasensor is investigated using other kinds of bacteria. The synthesized NPs and the morphology of the modified electrode are characterized by UV-Vis absorption spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, and electrochemical impedance spectroscopy. Full article
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Open AccessArticle
Computational Analysis of Enhanced Circulating Tumour Cell (CTC) Separation in a Microfluidic System with an Integrated Dielectrophoretic-Magnetophorectic (DEP-MAP) Technique
Chemosensors 2016, 4(3), 14; doi:10.3390/chemosensors4030014 -
Abstract
Cell based cancer analysis is an important analytic method to monitor cancer progress on stages by detecting the density of circulating tumour cells (CTCs) in the blood. Among the existing microfluidic techniques, dielectrophoresis (DEP), which is a label-free detection method, is favoured by
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Cell based cancer analysis is an important analytic method to monitor cancer progress on stages by detecting the density of circulating tumour cells (CTCs) in the blood. Among the existing microfluidic techniques, dielectrophoresis (DEP), which is a label-free detection method, is favoured by researchers. However, because of the high conductivity of blood as well as the rare presence of CTCs, high separation efficiency is difficult to achieve in most DEP microdevices. Through this study, we have proposed a strategy to improve the isolation performance, as such by integrating a magnetophoretic (MAP) platform into a DEP device. Several important aspects to be taken into MAP design consideration, such as permanent magnet orientation, magnetic track configuration, fluid flow parameter and separation efficiency, are discussed. The design was examined and validated by numerical simulation using COMSOL Multiphysics v4.4 software (COMSOL Inc., Burlington, MA, USA), mainly presented in three forms: surface plot, line plot, and arrow plot. From these results, we showed that the use of a single permanent magnet coupled with an inbuilt magnetic track of 250 μm significantly strengthens the magnetic field distribution within the proposed MAP stage. Besides, in order to improve dynamic pressure without compromising the uniformity of fluid flow, a wide channel inlet and a tree-like network were employed. When the cell trajectory within a finalized MAP stage is computed with a particle tracing module, a high separation efficiency of red blood cell (RBC) is obtained for blood samples corresponding up to a dilution ratio of 1:7. Moreover, a substantial enhancement of the CTCs’ recovery rate was also observed in the simulation when the purposed platform was integrated with a planar DEP microdevice. Full article
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Open AccessCommunication
TiO2 Nanotubes Membrane Flexible Sensor for Low-Temperature H2S Detection
Chemosensors 2016, 4(3), 15; doi:10.3390/chemosensors4030015 -
Abstract
This paper presents the fabrication and characterization of a flexible gas sensor based on TiO2 nanotubes membrane, onto which array interdigitated gold electrodes in one side and a common heater in the backside were obtained using conventional microfabrication techniques. This was used
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This paper presents the fabrication and characterization of a flexible gas sensor based on TiO2 nanotubes membrane, onto which array interdigitated gold electrodes in one side and a common heater in the backside were obtained using conventional microfabrication techniques. This was used to detect hydrogen sulphide within a concentration range of 6–38 ppm. The response to low concentrations of H2S at low temperature and good stability make the sensor a promising candidate for practical applications. These results support the proposal that the TiO2 nanotubes membrane flexible sensors are promising in portable on-site detection based on low cost nanomaterials. Full article
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Open AccessReview
Guanine Quadruplex Electrochemical Aptasensors
Chemosensors 2016, 4(3), 13; doi:10.3390/chemosensors4030013 -
Abstract
Guanine-rich nucleic acids are able to self-assemble into G-quadruplex four-stranded secondary structures, which are found at the level of telomeric regions of chromosomes, oncogene promoter sequences and other biologically-relevant regions of the genome. Due to their extraordinary stiffness and biological role, G-quadruples become
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Guanine-rich nucleic acids are able to self-assemble into G-quadruplex four-stranded secondary structures, which are found at the level of telomeric regions of chromosomes, oncogene promoter sequences and other biologically-relevant regions of the genome. Due to their extraordinary stiffness and biological role, G-quadruples become relevant in areas ranging from structural biology to medicinal chemistry, supra-molecular chemistry, nanotechnology and biosensor technology. In addition to classical methodologies, such as circular dichroism, nuclear magnetic resonance or crystallography, electrochemical methods have been successfully used for the rapid detection of the conformational changes from single-strand to G-quadruplex. This review presents recent advances on the G-quadruplex electrochemical characterization and on the design and applications of G-quadruplex electrochemical biosensors, with special emphasis on the G-quadruplex aptasensors and hemin/G-quadruplex peroxidase-mimicking DNAzyme biosensors. Full article
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Open AccessReview
Aptasensors Based on Stripping Voltammetry
Chemosensors 2016, 4(3), 12; doi:10.3390/chemosensors4030012 -
Abstract
Aptasensors based on stripping voltammetry exhibit several advantages, such as high sensitivity and multi-target detection from stripping voltammetric technology, and high selectivity from the specific binding of apamers with targets. This review comprehensively discusses the recent accomplishments in signal amplification strategies based on
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Aptasensors based on stripping voltammetry exhibit several advantages, such as high sensitivity and multi-target detection from stripping voltammetric technology, and high selectivity from the specific binding of apamers with targets. This review comprehensively discusses the recent accomplishments in signal amplification strategies based on nanomaterials, such as metal nanoparticles, semiconductor nanoparticles, and nanocomposite materials, which are detected by stripping voltammetry after suitable dissolution. Focus will be put in discussing multiple amplification strategies that are widely applied in aptasensors for small biomolecules, proteins, disease markers, and cancer cells. Full article
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Open AccessArticle
Simultaneous Determination of the Main Peanut Allergens in Foods Using Disposable Amperometric Magnetic Beads-Based Immunosensing Platforms
Chemosensors 2016, 4(3), 11; doi:10.3390/chemosensors4030011 -
Abstract
In this work, a novel magnetic beads (MBs)-based immunosensing approach for the rapid and simultaneous determination of the main peanut allergenic proteins (Ara h 1 and Ara h 2) is reported. It involves the use of sandwich-type immunoassays using selective capture and detector
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In this work, a novel magnetic beads (MBs)-based immunosensing approach for the rapid and simultaneous determination of the main peanut allergenic proteins (Ara h 1 and Ara h 2) is reported. It involves the use of sandwich-type immunoassays using selective capture and detector antibodies and carboxylic acid-modified magnetic beads (HOOC-MBs). Amperometric detection at −0.20 V was performed using dual screen-printed carbon electrodes (SPdCEs) and the H2O2/hydroquinone (HQ) system. This methodology exhibits high sensitivity and selectivity for the target proteins providing detection limits of 18.0 and 0.07 ng/mL for Ara h 1 and Ara h 2, respectively, with an assay time of only 2 h. The usefulness of the approach was evaluated by detecting the endogenous content of both allergenic proteins in different food extracts as well as trace amounts of peanut allergen (0.0001% or 1.0 mg/kg) in wheat flour spiked samples. The developed platform provides better Low detection limits (LODs) in shorter assay times than those claimed for the allergen specific commercial ELISA kits using the same immunoreagents and quantitative information on individual food allergen levels. Moreover, the flexibility of the methodology makes it readily translate to the detection of other food-allergens. Full article
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Open AccessReview
Aptamer-Based Electrochemical Sensing of Lysozyme
Chemosensors 2016, 4(2), 10; doi:10.3390/chemosensors4020010 -
Abstract
Protein analysis and quantification are required daily by thousands of laboratories worldwide for activities ranging from protein characterization to clinical diagnostics. Multiple factors have to be considered when selecting the best detection and quantification assay, including the amount of protein available, its concentration,
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Protein analysis and quantification are required daily by thousands of laboratories worldwide for activities ranging from protein characterization to clinical diagnostics. Multiple factors have to be considered when selecting the best detection and quantification assay, including the amount of protein available, its concentration, the presence of interfering molecules, as well as costs and rapidity. This is also the case for lysozyme, a 14.3-kDa protein ubiquitously present in many organisms, that has been identified with a variety of functions: antibacterial activity, a biomarker of several serious medical conditions, a potential allergen in foods or a model of amyloid-type protein aggregation. Since the design of the first lysozyme aptamer in 2001, lysozyme became one of the most intensively-investigated biological target analytes for the design of novel biosensing concepts, particularly with regards to electrochemical aptasensors. In this review, we discuss the state of the art of aptamer-based electrochemical sensing of lysozyme, with emphasis on sensing in serum and real samples. Full article
Open AccessCommunication
A Quality Control Assay to Access the HCl Molarity of Radionuclide Solutions
Chemosensors 2016, 4(2), 9; doi:10.3390/chemosensors4020009 -
Abstract
Strontium-82 is produced by proton activation of a rubidium chloride target in an accelerator or cyclotron and purified by ion exchange chromatography. The Strontrium-82 is used in Cardigen generators to produce Rubidium-82 for cardiac imaging. Quality control testing of the purified Strontium-82 is
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Strontium-82 is produced by proton activation of a rubidium chloride target in an accelerator or cyclotron and purified by ion exchange chromatography. The Strontrium-82 is used in Cardigen generators to produce Rubidium-82 for cardiac imaging. Quality control testing of the purified Strontium-82 is performed with Inductively Coupled Plasma-Optical Emission spectroscopy (ICP-OES) and gamma spectroscopy. To meet Department of Energy specifications for HCl molarity the purified Strontium-82 solution needs to be tested to determine if the isotope is in the 0.05–0.5 M HCl range. This manuscript reports a simple HCl molarity test to determine if the purified Strontium-82 solution meets specifications. Validation of the assay was performed by evaluating all solutions associate with Strontium-82 processing. Full article
Open AccessArticle
A Double Layer Sensing Electrode “BaTi(1-X)RhxO3/Al-Doped TiO2” for NO2 Detection above 600 °C
Chemosensors 2016, 4(2), 8; doi:10.3390/chemosensors4020008 -
Abstract
NO2 emission is mostly related to combustion processes, where gas temperatures exceed far beyond 500 °C. The detection of NO2 in combustion and exhaust gases at elevated temperatures requires sensors with high NO2 selectivity. The thermodynamic equilibrium for NO2
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NO2 emission is mostly related to combustion processes, where gas temperatures exceed far beyond 500 °C. The detection of NO2 in combustion and exhaust gases at elevated temperatures requires sensors with high NO2 selectivity. The thermodynamic equilibrium for NO2/NO ≥ 500 °C lies on the NO side. High temperature stability of TiO2 makes it a promising material for elevated temperature towards CO, H2, and NO2. The doping of TiO2 with Al3+ (Al:TiO2) increases the sensitivity and selectivity of sensors to NO2 and results in a relatively low cross-sensitivity towards CO. The results indicate that NO2 exposure results in a resistance decrease of the sensors with the single Al:TiO2 layers at 600 °C, with a resistance increase at 800 °C. This alteration in the sensor response in the temperature range of 600 °C and 800 °C may be due to the mentioned thermodynamic equilibrium changes between NO and NO2. This work investigates the NO2-sensing behavior of duplex layers consisting of Al:TiO2 and BaTi(1-x)RhxO3 catalysts in the temperature range of 600 °C and 900 °C. Al:TiO2 layers were deposited by reactive magnetron sputtering on interdigitated sensor platforms, while a catalytic layer, which was synthesized by wet chemistry in the form of BaTi(1-x)RhxO3 powders, were screen-printed as thick layers on the Al:TiO2-layers. The use of Rh-incorporated BaTiO3 perovskite (BaTi(1-x)RhxO3) as a catalytic filter stabilizes the sensor response of Al-doped TiO2 layers yielding more reliable sensor signal throughout the temperature range. Full article
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Open AccessArticle
Development of a Novel Cu(II) Complex Modified Electrode and a Portable Electrochemical Analyzer for the Determination of Dissolved Oxygen (DO) in Water
Chemosensors 2016, 4(2), 7; doi:10.3390/chemosensors4020007 -
Abstract
The development of an electrochemical dissolved oxygen (DO) sensor based on a novel Cu(II) complex-modified screen printed carbon electrode is reported. The voltammetric behavior of the modified electrode was investigated at different scan rates and oxygen concentrations in PBS (pH = 7). An
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The development of an electrochemical dissolved oxygen (DO) sensor based on a novel Cu(II) complex-modified screen printed carbon electrode is reported. The voltammetric behavior of the modified electrode was investigated at different scan rates and oxygen concentrations in PBS (pH = 7). An increase of cathodic current (at about −0.4 vs. Ag/AgCl) with the addition of oxygen was observed. The modified Cu(II) complex electrode was demonstrated for the determination of DO in water using chronoamperometry. A small size and low power consumption home-made portable electrochemical analyzer based on custom electronics for sensor interfacing and operating in voltammetry and amperometry modes has been also designed and fabricated. Its performances in the monitoring of DO in water were compared with a commercial one. Full article
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Open AccessReview
ZnO Quasi-1D Nanostructures: Synthesis, Modeling, and Properties for Applications in Conductometric Chemical Sensors
Chemosensors 2016, 4(2), 6; doi:10.3390/chemosensors4020006 -
Abstract
One-dimensional metal oxide nanostructures such as nanowires, nanorods, nanotubes, and nanobelts gained great attention for applications in sensing devices. ZnO is one of the most studied oxides for sensing applications due to its unique physical and chemical properties. In this paper, we provide
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One-dimensional metal oxide nanostructures such as nanowires, nanorods, nanotubes, and nanobelts gained great attention for applications in sensing devices. ZnO is one of the most studied oxides for sensing applications due to its unique physical and chemical properties. In this paper, we provide a review of the recent research activities focused on the synthesis and sensing properties of pure, doped, and functionalized ZnO quasi-one dimensional nanostructures. We describe the development prospects in the preparation methods and modifications of the surface structure of ZnO, and discuss its sensing mechanism. Next, we analyze the sensing properties of ZnO quasi-one dimensional nanostructures, and summarize perspectives concerning future research on their synthesis and applications in conductometric sensing devices. Full article
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Open AccessArticle
Turn on Fluorescent Probes for Selective Targeting of Aldehydes
Chemosensors 2016, 4(1), 5; doi:10.3390/chemosensors4010005 -
Abstract
Two different classes of fluorescent dyes were prepared as a turn off/on sensor system for aldehydes. Amino derivatives of a boron dipyrromethene (BDP) fluorophore and a xanthene-derived fluorophore (rosamine) were prepared. Model compounds of their product with an aldehyde were prepared using salicylaldehyde.
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Two different classes of fluorescent dyes were prepared as a turn off/on sensor system for aldehydes. Amino derivatives of a boron dipyrromethene (BDP) fluorophore and a xanthene-derived fluorophore (rosamine) were prepared. Model compounds of their product with an aldehyde were prepared using salicylaldehyde. Both amino boron dipyrromethene and rosamine derivatives are almost non-fluorescent in polar and apolar solvent. However, imine formation with salicylaldehyde on each fluorophore increases the fluorescence quantum yield by almost a factor of 10 (from 0.05 to 0.4). These fluorophores are therefore suitable candidates for development of fluorescence-based sensors for aldehydes. Full article
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Open AccessReview
Chemical Vapour Deposition of Gas Sensitive Metal Oxides
Chemosensors 2016, 4(1), 4; doi:10.3390/chemosensors4010004 -
Abstract
This article presents a review of recent research efforts and developments for the fabrication of metal-oxide gas sensors using chemical vapour deposition (CVD), presenting its potential advantages as a materials synthesis technique for gas sensors along with a discussion of their sensing performance.
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This article presents a review of recent research efforts and developments for the fabrication of metal-oxide gas sensors using chemical vapour deposition (CVD), presenting its potential advantages as a materials synthesis technique for gas sensors along with a discussion of their sensing performance. Thin films typically have poorer gas sensing performance compared to traditional screen printed equivalents, attributed to reduced porosity, but the ability to integrate materials directly with the sensor platform provides important process benefits compared to competing synthetic techniques. We conclude that these advantages are likely to drive increased interest in the use of CVD for gas sensor materials over the next decade, whilst the ability to manipulate deposition conditions to alter microstructure can help mitigate the potentially reduced performance in thin films, hence the current prospects for use of CVD in this field look excellent. Full article
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