The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform

Gustavo A. Rivas - One of the best experts on this subject based on the ideXlab platform.

  • adsorptive stripping voltammetric determination of amitrole at a multi wall carbon nanotubes Paste electdrode
    Electroanalysis, 2005
    Co-Authors: Manuel Chicharro, Esperanza Bermejo, Mónica Moreno, Alberto Sanchez, A. Zapardiel, Gustavo A. Rivas
    Abstract:

    This work reports the excellent electrocatalytic activity of carbon nanotubes Paste electrodes (CNTPE) prepared by dispersion of multi-wall carbon nanotubes (MWNT) within mineral oil toward the oxidation of 3-amino-1H-1,2,4triazole (amitrole). The quantification is performed by adsorptive stripping voltammetry (AdSV). The influence of the Paste Composition and surface pretreatments as well as the amitrole accumulation conditions on the adsorption and further electrooxidation of this herbicide is described. After potentiodynamic pretreatment in 0.050 M phosphate buffer pH 7.4 the amitrole oxidation signal shifts 250 mV toward more negative potential and the sensitivity increases 29 fold, demonstrating that pretreated CNTPEs are extremely useful for a highly sensitive determination of amitrole down to the sub-mM levels. The oxidation peak current is proportional to the amitrole concentration over the range from 0.8 to 7.0 mM (5 min accumulation), with a detection limit of 0.6 mM (48 mgL � 1 ) and a precision of 4.3%, n ¼ 20. The proposed method was used for the determination of amitrole in spiked river water (Alberche River (Madrid, Spain)) and tap water samples (Madrid, Spain) at levels higher than 0.6 mM.

  • Adsorptive Stripping Voltammetric Determination of Amitrole at a Multi‐Wall Carbon Nanotubes Paste Electdrode
    Electroanalysis, 2005
    Co-Authors: Manuel Chicharro, Esperanza Bermejo, Mónica Moreno, Alberto Sanchez, A. Zapardiel, Gustavo A. Rivas
    Abstract:

    This work reports the excellent electrocatalytic activity of carbon nanotubes Paste electrodes (CNTPE) prepared by dispersion of multi-wall carbon nanotubes (MWNT) within mineral oil toward the oxidation of 3-amino-1H-1,2,4triazole (amitrole). The quantification is performed by adsorptive stripping voltammetry (AdSV). The influence of the Paste Composition and surface pretreatments as well as the amitrole accumulation conditions on the adsorption and further electrooxidation of this herbicide is described. After potentiodynamic pretreatment in 0.050 M phosphate buffer pH 7.4 the amitrole oxidation signal shifts 250 mV toward more negative potential and the sensitivity increases 29 fold, demonstrating that pretreated CNTPEs are extremely useful for a highly sensitive determination of amitrole down to the sub-mM levels. The oxidation peak current is proportional to the amitrole concentration over the range from 0.8 to 7.0 mM (5 min accumulation), with a detection limit of 0.6 mM (48 mgL � 1 ) and a precision of 4.3%, n ¼ 20. The proposed method was used for the determination of amitrole in spiked river water (Alberche River (Madrid, Spain)) and tap water samples (Madrid, Spain) at levels higher than 0.6 mM.

Alain Walcarius - One of the best experts on this subject based on the ideXlab platform.

  • Voltammetric detection of copper(II) at a carbon Paste electrode containing an organically modified silica
    Sensors and Actuators B: Chemical, 2001
    Co-Authors: M. Etienne, J. Bessiere, Alain Walcarius
    Abstract:

    A carbon Paste electrode modified with aminopropyl-grafted silica gel (APS) was evaluated as an electrochemical sensor for copper species in aqueous medium. The overall analysis involved a two-step procedure: an accumulation step at open circuit, followed by medium exchange to a pure electrolyte solution for the voltammetric quantification. During the preconcentration step, copper(II) was accumulated on the APS surface by complexation with the amine groups. In the detection step, copper(II) was desorbed in acidic medium, then cathodically electrolyzed at −0.5 V for 60 s, and detected by anodic stripping square wave voltammetry. The influence of various experimental parameters on the sensor response was investigated (i.e. pH of the detection and accumulation media, electrolysis time, carbon Paste Composition, silica gel porosity, accumulation time). Reproducible results were obtained, giving after optimization a linear calibration in the 5×10−8–2×10−7 M concentration range, with a detection limit of 3×10−9 M. This new sensor was applied to copper analysis in laboratory tap water.

  • Voltammetric Detection of Iodide after Accumulationby Friedel's Salt
    Electroanalysis, 2001
    Co-Authors: Alain Walcarius, Grégory Lefèvre, Jean-philippe Rapin, Guillaume Renaudin, Michel François
    Abstract:

    Friedel's salt, a mineral anion exchanger belonging to the family of the layered double hydroxides (LDHs), was synthesized and used as a novel electrode modifier for the accumulation of iodide species and their subsequent voltammetric determination at carbon Paste. Beside the preconcentration features of Friedel's salt towards iodide species, its presence at the electrode surface allowed to evidence the oxidation of molecular iodine into iodate (with transient IO−), contrary to most carbon‐based electrodes, as demonstrated by cyclic voltammetry. Preconcentration was achieved at open circuit and iodide was then detected by differential pulse voltammetry in unbuffered chloride medium. The sensing process was further improved by optimization of the carbon Paste Composition, the detection medium, and the accumulation time. The detection limit was 0.06 µM (3σ), with linear calibration ranges extending from 0.1 to 1 µM, 1 to 10 µM, and 10 to 50 µM, giving a dynamic range of over several orders of magnitude. The effect of anionic interferences was evaluated and the sensor was applied to iodide analysis in synthetic ground‐ and seawaters.

Manuel Chicharro - One of the best experts on this subject based on the ideXlab platform.

  • adsorptive stripping voltammetric determination of amitrole at a multi wall carbon nanotubes Paste electdrode
    Electroanalysis, 2005
    Co-Authors: Manuel Chicharro, Esperanza Bermejo, Mónica Moreno, Alberto Sanchez, A. Zapardiel, Gustavo A. Rivas
    Abstract:

    This work reports the excellent electrocatalytic activity of carbon nanotubes Paste electrodes (CNTPE) prepared by dispersion of multi-wall carbon nanotubes (MWNT) within mineral oil toward the oxidation of 3-amino-1H-1,2,4triazole (amitrole). The quantification is performed by adsorptive stripping voltammetry (AdSV). The influence of the Paste Composition and surface pretreatments as well as the amitrole accumulation conditions on the adsorption and further electrooxidation of this herbicide is described. After potentiodynamic pretreatment in 0.050 M phosphate buffer pH 7.4 the amitrole oxidation signal shifts 250 mV toward more negative potential and the sensitivity increases 29 fold, demonstrating that pretreated CNTPEs are extremely useful for a highly sensitive determination of amitrole down to the sub-mM levels. The oxidation peak current is proportional to the amitrole concentration over the range from 0.8 to 7.0 mM (5 min accumulation), with a detection limit of 0.6 mM (48 mgL � 1 ) and a precision of 4.3%, n ¼ 20. The proposed method was used for the determination of amitrole in spiked river water (Alberche River (Madrid, Spain)) and tap water samples (Madrid, Spain) at levels higher than 0.6 mM.

  • Adsorptive Stripping Voltammetric Determination of Amitrole at a Multi‐Wall Carbon Nanotubes Paste Electdrode
    Electroanalysis, 2005
    Co-Authors: Manuel Chicharro, Esperanza Bermejo, Mónica Moreno, Alberto Sanchez, A. Zapardiel, Gustavo A. Rivas
    Abstract:

    This work reports the excellent electrocatalytic activity of carbon nanotubes Paste electrodes (CNTPE) prepared by dispersion of multi-wall carbon nanotubes (MWNT) within mineral oil toward the oxidation of 3-amino-1H-1,2,4triazole (amitrole). The quantification is performed by adsorptive stripping voltammetry (AdSV). The influence of the Paste Composition and surface pretreatments as well as the amitrole accumulation conditions on the adsorption and further electrooxidation of this herbicide is described. After potentiodynamic pretreatment in 0.050 M phosphate buffer pH 7.4 the amitrole oxidation signal shifts 250 mV toward more negative potential and the sensitivity increases 29 fold, demonstrating that pretreated CNTPEs are extremely useful for a highly sensitive determination of amitrole down to the sub-mM levels. The oxidation peak current is proportional to the amitrole concentration over the range from 0.8 to 7.0 mM (5 min accumulation), with a detection limit of 0.6 mM (48 mgL � 1 ) and a precision of 4.3%, n ¼ 20. The proposed method was used for the determination of amitrole in spiked river water (Alberche River (Madrid, Spain)) and tap water samples (Madrid, Spain) at levels higher than 0.6 mM.

M. Forsyth - One of the best experts on this subject based on the ideXlab platform.

  • Characterization of a proton conductor based on silicotungstic acid
    Electrochimica Acta, 2001
    Co-Authors: Jiazeng Sun, D.r. Macfarlane, M. Forsyth
    Abstract:

    It was found in this work that silicotungstic acid hydrate could be mixed with phosphoric acid (H3PO4, 85%) to make a viscous Paste material with high conductivity (10−2 S/cm at room temperature). The STA/H3PO4 Paste samples were stable at 80°C in the atmosphere, and at 100°C under constant humidity over 10 days. The conductivity behavior of the Paste samples has been investigated under various conditions, and it was found to be dependent on temperature, Paste Composition, and environment humidity.

  • Characterization of a proton conductor based on silicotungstic acid
    Electrochimica Acta, 2001
    Co-Authors: Jiazeng Sun, D.r. Macfarlane, M. Forsyth
    Abstract:

    It was found in this work that silicotungstic acid hydrate could be mixed with phosphoric acid (H3PO4, 85%) to make a viscous Paste material with high conductivity (10−2 S/cm at room temperature). The STA/H3PO4 Paste samples were stable at 80°C in the atmosphere, and at 100°C under constant humidity over 10 days. The conductivity behavior of the Paste samples has been investigated under various conditions, and it was found to be dependent on temperature, Paste Composition, and environment humidity.

Tai Man Yue - One of the best experts on this subject based on the ideXlab platform.

  • Laser fabrication of Mo-TiC MMC on AA6061 aluminum alloy surface
    Surface & Coatings Technology, 2002
    Co-Authors: Peter Han Joo Chong, Hau Chung Man, Tai Man Yue
    Abstract:

    Abstract A Nd-YAG laser was used to clad Mo/TiC onto the surface of Aluminum Alloy AA6061. Experimental results indicated that the Mo/TiC clad layer has good metallurgical bonding with the substrate. TiC particulates are uniformly dispersed in the clad surface. The optimised clad layer with a pre-mixed Paste Composition of 30%Mo70%TiC exhibited the best wear resistance during a pin-on-disc abrasive wear test. The microhardness of the clad layer is 5–10 times higher than the as-received Al alloy. The microstructures, chemical Compositions and the worn surface of the clad layers were analysed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffractometry (XRD).

  • Laser fabrication of Mo-TiC MMC on AA6061 aluminum alloy surface
    Surface and Coatings Technology, 2002
    Co-Authors: Peter Han Joo Chong, Hau Chung Man, Tai Man Yue
    Abstract:

    A Nd-YAG laser was used to clad Mo/TiC onto the surface of Aluminum Alloy AA6061. Experimental results indicated that the Mo/TiC clad layer has good metallurgical bonding with the substrate. TiC particulates are uniformly dispersed in the clad surface. The optimised clad layer with a pre-mixed Paste Composition of 30%Mo70%TiC exhibited the best wear resistance during a pin-on-disc abrasive wear test. The microhardness of the clad layer is 5-10 times higher than the as-received Al alloy. The microstructures, chemical Compositions and the worn surface of the clad layers were analysed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffractometry (XRD).Department of Industrial and Systems Engineerin