Steady-state and transient conductivity of collodial solutions of gold nanobeads

Steady-state and transient conductance measurements of gold nanobeads solutions deposited on top of interdigitated electrodes have been performed. It is shown that the application of an electric field of moderate value between electrodes during the drying process of the droplet makes the resulting steady-state conductance value to increase significantly. The dynamics of the gold nanobeads in the solution has been studied by means of transient current measurements during the drying process and the effects correlated to the changes in the morphology of the association of the gold nanobeads when they reach the substrate. It is seen that the application of the electric field foster the formation of gold beads monolayers, chains, and dendritic associations which, in combination with the humidity conditions of the sample surface, are believed to be the reasons for the conductance increase.Peer Reviewe

Interdigitated μ-electrodes for development of an impedimetric immunosensor for atrazine detection.

This contribution describes the development of an impedimetric immunosensor for atrazine detection. This immunosensor is based on the use of interdigitated metallic μ-electrodes (IDμEs) The method described in this work does not use any redox mediator and relies on the direct detection of immunochemical competitive reaction between the pesticide and a haptenized-protein immobilized on interdigitated μ-electrodes for the specific antibody. The immunoreagents used were specifically developed to detect atrazine. The immunochemical detection of this pesticide is achieved without using any label. The immunosensor shows a limit of detection of 8.34±1.37 μg L-1, witch is lower than the Maximun Residue Level (MRL) (50μg L-1)established by EU (European Union)for residues of atrazine as herbicide in the wine grapes and other foodstuff products.Peer ReviewedPostprint (published version

Immunosensor impedimetrico para la detección de pesticidas

En este trabajo describimos un immunosensor impedimétrico para la detección de pesticidas. Para demostrar dicho sensor hemos utilizado atrazina, como pesticida de test. Este sensor está basado en el uso de μ-electrodos interdigitados así como en reactivos específicamente desarrollados para la detección de este pesticida. Los anticuerpos utilizados no incluyen ningún tipo de etiqueta. Así mismo, el sensor no incluye ningún tipo de par redox que amplifique la señal. La detección immunoquímica de atrazina se alcanza mediante una reacción competitiva entre el antígeno tapizado y el pesticida por una pequeña cantidad de anticuerpo. Los cambios en la impedancia producidos por la inclusión de los bioreactivos son interpretados utilizando un circuito equivalente, el cual representa el sistema de manera fiable. La detección se monitoriza a partir de medidas impedimétricas diferenciales en un amplio espectro de frecuencia. El immunosensor muestra límites de detección en el rango de pocos ppb's, lo cual está muy por debajo del Maximum Residue Level (MRL) (50 μg L-1) establecido por la Unión Europea para los residuos de atrazina en uvas de vino así como en otros productos alimenticios. Aunque en este trabajo el immunosensor se ha demostrado para la atrazina, otros pesticidas podrían detectarse mediante este método siempre que se utilicen los reactivos adecuados.Peer ReviewedPostprint (author’s final draft

Immunosensors based on interdigitated electrodes for the detection and quantification of pesticides in food

Postprint (published version

Immunosensors based on interdigitated electrodes for the detection and quantification of pesticides in food

Postprint (published version

Exact, asymptotic and numerical solutions to certain steady, axisymmetric, ideal fluid flow problems in IR''3

SIGLEAvailable from British Library Document Supply Centre-DSC:D203938 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Fabrication of flexible interdigitated µ-electrodes (FIDµEs) for the development of a conductimetric immunosensor for atrazine detection based on antibodies labelled with gold nanoparticles

The present paper describes a simple and low-cost method for the fabrication of mechanically flexible interdigitated μ-electrodes (FIDμEs) and its application as immunosensor. FIDμEs consist of two coplanar non-passivated interdigitated metallic μ-electrodes supported on a flexible transparent substrate, polyethylene naphthalate (PEN). Bioreagents deposition on PEN substrates becomes possible by depositing SiO2 on the electrodes surface (fingers and inter-digits space). These FIDμEs were successfully applied for the development of a selective conductimetric immunosensor for the quantification of atrazine residues. The immunosensor has been demonstrated for detection of small amounts of atrazine, thanks to the use of immunoreagents specifically developed to detect this pesticide. The detection method applied is based on the use of antibodies labelled with gold nanoparticles. The presence of these particles amplifies the conductive signal; hence the immunosensor response was quantified using simple and inexpensive DC measurements. Immunochemical detection of the concentrations of atrazine is achieved by a competitive reaction which occurs before the inclusion of the labelled antibodies. The immunosensor shows limits of detection in the order of 2–3 μg L−1, far below the maximum residue level (50 μg kg−1) established by EU for residues of atrazine as herbicide in the wine grapes and other foodstuff products.Peer Reviewe

Steady-state and transient conductivity of collodial solutions of gold nanobeads

Steady-state and transient conductance measurements of gold nanobeads solutions deposited on top of interdigitated electrodes have been performed. It is shown that the application of an electric field of moderate value between electrodes during the drying process of the droplet makes the resulting steady-state conductance value to increase significantly. The dynamics of the gold nanobeads in the solution has been studied by means of transient current measurements during the drying process and the effects correlated to the changes in the morphology of the association of the gold nanobeads when they reach the substrate. It is seen that the application of the electric field foster the formation of gold beads monolayers, chains, and dendritic associations which, in combination with the humidity conditions of the sample surface, are believed to be the reasons for the conductance increase.Peer Reviewe

Immunosensors for atrazine detection in red wine samples

Two novel immunosensors, one impedimetric and other one conductimetric, for atrazine detection in red wine samples have been developed. Impedimetric immunosensor is based on an array of interdigitated μ- electrodes (IDμEs) and bioreagents specifically developed to detect this pesticide. Conductimetric immunosensor incorporates additionally gold nanoparticles. Bioreagents were covalently immobilized on the surface of the electrodes (interdigital space). In both cases the biochemical determination of atrazine is possible without any redox mediator. For the case of the impedimetric immunosensor, the detection method is based on impedimetric measurements (in a wide range of frequencies), whereas in the case of the conductimetric immunosensor the detection method is based on conductimetric measurements (DC measurements).The potential of the impedimetric immunosensor to analyze atrazine in complex sample matrices, such as red wine, have been evaluated. This immunosensor can detect atrazine with limits of detection in the order sub-ppb, far below the maximum residue level (MRL) (50 μg L−1) established by European Union (EU) for residues of this herbicide in the wine grapes.Peer ReviewedPostprint (published version