The light modulation of the interaction of l-cysteine with porphyrins coated ZnO nanorods

The photoenhancement properties of metalloporphyrins coated ZnO nanostructures have been demonstrated for both gas and liquid sensing. In gas sensing the light favours the electron transfer from the adsorbed analyte and the porphyrin, while in solution the increased catalytic effects of metalloporphyrins should also be considered. In this paper we report the sensing properties of copper and manganese porphyrins coated ZnO nanorods with respect to a thiolated biomolecule such as the l-cysteine. A one-pot hydrothermal growth method has been used to prepare the functionalized nanostructures onto an ITO substrate. The ensemble ITO-ZnO-porphyrin has been used as the working electrode in a three-electrodes amperometric setup. I/V curves have been measured at different concentrations of l-cysteine and interfering compounds. The I/V curves have been analyzed by principal component analysis, and the first principal component has been used as the sensor feature. The results show that illumination enhances the sensitivity to l-cysteine and the selectivity towards a set of non-thiolated aminoacids and organic acids. ? 2014 Elsevier B.V. All rights reserved.