Plamen Malchev

Voltammetric Detection of Urea on an Ag-Modified Zeolite- Expanded Graphite-Epoxy Composite Electrode

In this paper, a modified expanded graphite composite electrode based on natural zeolitic volcanic tuff modified with silver (EG-Ag-Z-Epoxy) was developed. Cyclic voltammetry measurements revealed a reasonably fast electron transfer and a good stability of the electrode in 0.1 M NaOH supporting electrolyte. This modified electrode exhibited moderate electrocatalytic effect towards urea oxidation, allowing its determination in aqueous solution. The linear dependence of the current versus urea concentration was reached using square-wave voltammetry in the concentrations range of urea between 0.2 to 1.4 mM, with a relatively low limit of detection of 0.05 mM. A moderate enhancement of electroanalytical sensitivity for the determination of urea at EG-Ag-Z-Epoxy electrode was reached by applying a chemical preconcentration step prior to voltammetric/amperometric quantification.

Carbon-based Composite Electrodes : Preparation, Characterization and Application in Electroanalysis

Electrodes based on carbon, i.e., expanded graphite (20%, wt.)-epoxy composite (20EG-Epoxy) and expanded graphite (20%, wt.)-polystyrene composite (20EG-PS) have been prepared, characterized using scanning electron microscopy (SEM) and cyclic voltammetry (CV), and tested as anodic sensors. The electrodes exhibited good mechanical resistance and low electrical resistances. Scan rate dependent cyclic voltammetry responses at 20EG-Epoxy and 20EG-PS composite electrodes, which were exemplified for thiourea (TU), a toxic sulphur organic compound selected as testing target analyte in 0.1 M Na2SO4 supporting electrolyte, were investigated. The obtained voltammetric data were in accordance with those for a random array of microelectrodes. The voltammetric and chronoamperometric detection results of TU in tap water samples, without a supplementary addition of supporting electrolyte, at 20EG-Epoxy electrode proved its use for direct analysis of environmental samples.

Conductive Carbon Loaded Polymer Film Electrodes for Pulsed-Power Applications. Part I: Determination of the Film Properties

Abstract Electrically conductive polymer composites consisting of a nonconductive polymer matrix and conductive fillers, such as carbon black, are widely used. This contribution describes the specific electrical properties of polymer composite films for pulsed conditions in the microsecond (10−6 s) range. Investigation of an industrially available volume conductive polymer film (Carbostat) showed that the electrical properties of this material, which can be considered for electrodes in pulsed power applications, are quite different from the properties for DC conditions.

Conductive Carbon Loaded Polymer Film Electrodes for Pulsed Power Applications. Part II: Determination and Minimization of the Contact Resistance

Abstract Electrically conductive polymer composites consisting of a nonconductive polymer matrix and conductive fillers, such as carbon black, are widely used. This contribution describes a newly developed measurement setup that has been built to investigate the specific electrical properties of polymer composite films for pulsed conditions in the microsecond (10−6 s) range. For an industrially available volume conductive polymer film (Carbostat) the contact resistivity to copper has been investigated. Also, three methods for minimizing the contact resistivity, namely pressing, gluing, and wetting, have been compared for a wide range of applied current densities.

Carbon Composite Electrodes Applied for Electrochemical Sensors

Electrodes based on particulate carbon-epoxy or polystyrene composites, have been formed and characterized using electrochemical methods. The working electrodes made of various forms of graphite or carbon and using different polymers, a type of expanded and exfoliated graphite-epoxy (EEG-Epoxy), carbon nanofiber-expanded graphite-epoxy (CNF-EG-Epoxy), expanded graphite-polystyrene (EG-PS), expanded graphite-epoxy (EG-Epoxy) were tested for electrochemical sensing of various organic pollutants in aqueous solution. The prepared carbon composite electrodes showed good mechanical strength, low electrical resistance, and easy new surface by simple polishing, all useful characteristics for electroanalytical purposes. The electrochemical performance of these electrodes was studied by cyclic voltammetry (CV), linear-scan voltammetry (LSV), chronoamperometry (CA), differential pulsed voltammetry (DPV), and square-wave voltammetry (SWV).