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Abstract: H2 sensing behaviour of Palladium nanoparticles (PdNP) mixed with nafion has been demonstrated as a function of H2 concentration. PdNP (15 nm diameter) were mixed with nafion (5% solution) in varying concentrations and cast over interdigitated μ-electrodes (IDμE′s). Measurements were carried out at room temperature and change in resistance of the PdNPnafion film upon exposure to hydrogen was recorded. Resistance response studies revealed a unique concentration specific response, exhibiting a pulsed effect (above 1%) and a saturated response (upto 1%), for films cast with solution strength of 2.5 mg PdNPs in 10 μl nafion. The characteristic change in the sensing behaviour can be used to develop a sensor to determine the H2 concentration level with high sensitivity and fast response. [ABSTRACT FROM AUTHOR]

Abstract: The potential of a conductimetric immunosensor to detect residual amounts of atrazine in a complex matrix, such as red wine, is evaluated. The immunosensor presented is based on interdigitated μ-electrodes (IDμEs), immunoreagents specifically developed to detect atrazine, and antibodies labelled with gold nanoparticles. Due to the amplification of the conductive signal, produced by the presence of the gold particles, atrazine can be detected using simple and inexpensive direct current (DC) measurements. Then, sensors response is related to the atrazine concentration in the sample. Likewise, the presence of gold particles generates an increase in the intensity of the electric field between the electrodes. The time for assay completion, for 48 samples, was 5h. Nevertheless, during the first hour (devoted to the incubation assays), the number of samples could be increased without prejudice the assay duration. Sensor responses obtained using red wine samples are compared with results obtained using buffer solutions. As a consequence, the strong matrix effect related to red wine samples has been identified as a non-specific increase of the current intensity through the device. The limits of detection (LODs) obtained are far below the Maximum Residue Level (50μgkg−1) established by EU for residues of atrazine as herbicide in the wine grapes and other foodstuff products. This opens the door to commercial sensors of simple manipulation, transportable and economics. [Copyright &y& Elsevier]

Abstract: A novel conductimetric immunosensor for atrazine detection has been designed and developed. This immunosensor is mainly based on antibodies labelled with gold nanoparticles. Additionally, the immunosensor consists of an array of two coplanar non-passivated interdigitated metallic μ-electrodes (IDμE) and immunoreagents specifically developed to detect this pesticide. The chemical recognition layer was covalent immobilized on the interdigital space. Immunochemical detection of the concentration of atrazine is achieved by a competitive reaction that occurs before the inclusion of the labelled antibodies. It is shown that the gold nanoparticles provide an amplification of the conductive signal and hence makes possible to detect atrazine by means of simple DC measurements. The conductimetric immunosensor and its biofunctionalization steps have been characterized by chemical affinity methods and impedance spectroscopy. This work describes the immunosensor structure, fabrication, physico-chemical and analytical characterization, and the immunosensor response using conductivity measurements. The immunosensor developed detects atrazine with limits of detection in the order of 0.1–1μgL−1, far below the maximum residue level (MRL) (100μgL−1) established by European Union (EU) for residues of this herbicide in the wine. Although in this paper the competitive reaction occurs in buffer, an initial study of the wine matrix effect is also described. [Copyright &y& Elsevier]

Abstract: A novel impedimetric immunosensor for atrazine detection has been developed. The immunosensor is based on an array of interdigitated μ-electrodes (IDμE) and immunoreagents specifically developed to detect this pesticide. Immunochemical determination of atrazine is possible without the use of any label. An atrazine-haptenized protein was covalently immobilized on the surface of the interdigitated μ-electrodes area (interdigits space) previously activated with (3-glycidoxypropyl)trimethoxysilane. Before, the gold electrodes were blocked using N-acetylcysteamine to prevent non-specific adsorptions. All biofunctionalization steps were characterized by chemical affinity methods and impedance spectroscopy. Immunosensors measures are made by exposing the sensor to solutions containing a mixture of the analyte and the specific antibody. With this configuration, the immunosensor detects atrazine with a limit of detection of 0.04μgL−1 without the use of any label. The potential of the immunosensor to analyze pesticide residues in complex sample matrices, such as red wine, has been evaluated. The results shown that after solid-phase extraction atrazine can be determined in this type of sample with a limit of detection of 0.19μgL−1, far below the Maximum Residue Level (MRL) established by EC for residues of this herbicide in wine. [Copyright &y& Elsevier]

Abstract: A novel impedimetric immunosensor for the detection of a wide variety of compounds, based on a two coplanar non-passivated interdigitated metallic μ-electrodes and non-labeled immunoreactives, has been designed and developed. A very useful detection method is the impedance spectroscopy sweeping a wide frequency range. This is a powerful, but cumbersome tool to study the sensor performance providing trustworthy results. In this work, it is shown that the exploitation of the changes observed of the impedance at a single frequency provide very good correlation with antibody concentration and hence greatly reduces the signal acquisition and processing complexity. It has thereby a great potential for low cost, low power, fast response and simple use for the in-field or at-line applications. In this work, the application of the method to atrazine detection is described. The results show that the immunosensor signal is a function of the pesticide concentration following a competitive binding relationship, with limits of detection lower than the maximum residue level required by EC for atrazine in wine grapes and other foodstuff products. [Copyright &y& Elsevier]

Abstract: A novel impedimetric immunosensor for atrazine detection, a widely used pesticide, is described. It is based on a two coplanar non-passivated interdigitated metallic μ-electrodes (IDμE) and the differential measurement of the impedance frequency spectrum. No redox electrodes have been included in the sensor. The chemical recognition layer was deposited on top of the interdigitated μ-electrodes area (fingers and inter-digits space). Immunochemical detection of the atrazine concentration is achieved by a competitive reaction without using any label. Furthermore immunoreagents specifically developed to detect this pesticide have been used. The immunosensor and its functionalization steps have been characterized by means of chemical affinity methods and impedance spectroscopy. This work describes immunosensor development and its physico-chemical and analytical characterization. The immunosensor shows a limit of detection of 8.34±1.37μgL−1, which is lower than the Maximum Residue Level (MRL) (100μgL−1) established by EU (European Union) for residues of atrazine as herbicide in the wine grapes and other foodstuff products. [Copyright &y& Elsevier]