Emese Kriván

EQCM and in situ conductance studies on the polymerisation and redox features of thiophene co-polymers

3-Thiophene-acetic acid and 3-methylthiophene co-polymers have been prepared with the consideration that the solvation behaviour of the film could be modified. The modification is coupled with the observed splitting of the oxidation peak on the cyclic voltammograms. The redox transformation of the films was studied by electrochemical quartz crystal microbalance (EQCM) and in situ conductance (ISC) techniques. Mass changes during the electrochemical processes showed that the cation is not involved into the charge balancing of the film. Manifestation of self-doping was excluded by analogous measurements with an aprotic co-polymer of methylthiophene. Results completed with in situ conductance and spectroelectrochemical observations confirmed the assumption of a chemical step taking place after the first oxidation. In this process desolvation of the oxidised intermediate occurs, which is a necessary step for the achievement of the quasi-metallic state.

MRA combined spectroelectrochemical studies on the redox stability of PPy/DS films

Abstract Pyrrole was electropolymerized in aqueous sodium dodecyl sulfate (SDS) solutions and a correlation between the absorbance maximum (λmax) and the effect of micelle formation was found. The redox stability of the film was studied in 0.05 M SDS solution by cyclic spectrovoltammetry. The spectral changes acquired in different potential regions were analyzed by matrix rank analysis (MRA) to determine the number of independent absorbing species necessary for the description of the observations. With the extension of the potential to the more positive region a new oxidation step was obtained, which was connected to structural changes in the film owing to swelling. Spectral changes proved that no degradation processes occur in the potential range covered. In the more extended potential region neutral polymeric segments are required to reach the quasi-metallic state, and the MRA indicated the necessity to assume the presence of extra species which are connected to partially hydrated parts of the film.

Optimization of the photoactivity of conducting polymer covered ZnO nanorod composite electrodes

AbstractA simple, reproducible, one-step electrochemical synthesis of vertically aligned ZnO nanorod electrode has been worked out. The gradual decrease in the photoelectrochemical performance of the hexagonal ZnO nanorod electrode indicated rapid photodegradation. In order to prevent the n-type semiconductor from photocorrosion, different conducting polymers were deposited on it. Composition and morphology of the hybrids were controlled by carefully changing the electropolymerization parameter (e.g., deposition charge) for the various N or S containing heterocycles. Electrochemical measurements proved that the redox activity of these covering polymer layers was preserved in the hybrid configuration. Photoelectrochemical activity of the polymer-covered ZnO nanorods was masked by thicker layers. Thin films however, successfully inhibited the photocorrosion of ZnO while preserving their photoactivity. Effective protection was evidenced using poly(3,4-ethylenedioxypyrrole) (PEDOP) in comparison with polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT). Graphical Abstractᅟ