Stelian Lupu

Electrochemical preparation and characterisation of bilayer films composed by Prussian Blue and conducting polymer

Abstract Preparation and electrochemical behaviour of bilayer films consisting of iron(III) hexacyanoferrate, well known as Prussian Blue, and of poly[4,4 ′ -bis(butylsulphanyl)-2,2 ′ -bithiophene], on a platinum electrode, are reported. The electrochemical features of the Prussian Blue/conducting polymer bilayer system are examined in aqueous and acetonitrile solutions. Cyclic voltammetric studies show that, in acetonitrile solvent, the inner layer Prussian Blue is electroactive to some extent, though the electrochemical response of the system is mainly accounted for by poly[4,4 ′ -bis(butylsulphanyl)-2,2 ′ -bithiophene] outer layer. On the other hand, in aqueous solution Prussian Blue exhibits good electroactivity. Under specific experimental conditions, the individual redox behaviour of each constituent of the bilayer is evidenced in the two solvents separately, i.e., that of PB and that of poly[4,4 ′ -bis(butylsulphanyl)-2,2 ′ -bithiophene] in aqueous and in organic solvent, respectively. However, interesting reciprocal influences are evident in the current/potential curves recorded under conditions which are discussed.

Polythiophene Derivative Conducting Polymer Modified Electrodes and Microelectrodes for Determination of Ascorbic Acid. Effect of Possible Interferents

Conventional-size electrodes and microelectrodes coated by electrogenerated poly[4,4′-bis(butylsulfanyl)-2,2′-bithiophene] have been tested with respect to the electrocatalytic oxidation of a particularly interesting analyte, i.e., ascorbic acid, in different concentrations of phosphate buffer, aqueous solution. Linear sweep and cyclic voltammetry have been used and the quantities related to the analyte concentration were the peak current and the diffusion (t−1/2) deconvoluted peak current in the case of conventional-size and of microelectrode, respectively. Fairly good linear correlation could be found; a particularly wide linearity range was obtained by working with the microelectrode. It showed to give good results also at a very low (10−4 M) phosphate buffer-supporting electrolyte concentration. The actual interference on the analysis of compounds often coupled with ascorbic acid in natural or pharmaceutical products has been studied.

Development of Amperometric Biosensors Based on Nanostructured Tyrosinase-Conducting Polymer Composite Electrodes

Bio-composite coatings consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and tyrosinase (Ty) were successfully electrodeposited on conventional size gold (Au) disk electrodes and microelectrode arrays using sinusoidal voltages. Electrochemical polymerization of the corresponding monomer was carried out in the presence of various Ty amounts in aqueous buffered solutions. The bio-composite coatings prepared using sinusoidal voltages and potentiostatic electrodeposition methods were compared in terms of morphology, electrochemical properties, and biocatalytic activity towards various analytes. The amperometric biosensors were tested in dopamine (DA) and catechol (CT) electroanalysis in aqueous buffered solutions. The analytical performance of the developed biosensors was investigated in terms of linear response range, detection limit, sensitivity, and repeatability. A semi-quantitative multi-analyte procedure for simultaneous determination of DA and CT was developed. The amperometric biosensor prepared using sinusoidal voltages showed much better analytical performance. The Au disk biosensor obtained by 50 mV alternating voltage amplitude displayed a linear response for DA concentrations ranging from 10 to 300 μM, with a detection limit of 4.18 μM.