Electrodeposition of Cu onto Pt in presence of egg ovalbumin

Abstract

In the present paper, the effect of egg ovalbumin (OVA) on the electrodeposition of Cu and on the underpotential deposition (UPD) and overpotential deposition (OPD) behaviour of Cu on polycrystalline Pt electrodes is studied. The interfacial behaviour of OVA was studied at a polycrystalline Pt electrode, using cyclic voltammetry (CV) below (25°C) and above (80°C) the OVA denaturation temperature. Ovalbumin was found to adsorb strongly at the Pt surface. As the temperature was increased above the denaturation value, the surface charge density for OVA adsorption also increased, owing to conformational unfolding. Above the denaturation temperature, the surface charge density continued to increase, suggesting multilayer adsorption. Cyclic voltammetry measurements during Cu electroplating from an acidic chloride bath in the presence of OVA at 25°C highlighted a remarkable electrodeposition and stripping inhibition. This effect was not observed at 80°C. Potentiodynamic measurements in the Cu plating bath highlight a strong OVA adsorption in a well defined potential interval. In situ surface enhanced Raman spectra were measured both during electrodeposition and corrosion of Cu in the Cu plating bath. Potential dependent changes of spectral pattern have been found, which can be interpreted in terms of conformational changes of adsorbed OVA. The study was complemented by morphological and optical characterisation of electrodeposited Cu by scanning electron microscopy and spectral reflectivity measurements. Scanning electron microscopy observations reveal notable changes of morphology, possibly related to the assembly of adsorbed protein at the electrode and to the modification of the electrodic charge transfer process. Finally, comparative spectral reflectivity measurements showed that the addition of OVA brings about changes of the electronic structure of the Cu film.