Modification of fluorine-doped tin oxide surface: Optimization of the electrochemical grafting of diazonium salt

Abstract

Fluorine-doped tin oxide (FTO) electrodes were functionalized by electro reduction of in situ generated 4-carboxyphenyl diazonium salt. Several grafting potentials and times were investigated in order to find the optimal grafting conditions. The electrochemical behavior of bare FTO electrodes in the presence of the diazonium, together with Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) characterization of the grafted electrodes in the presence of redox probes ferricyanide and ferrocene allowed us to conclude that 10 min grafting under a controlled potential of −0.50 V lead to the formation of a poorly-packed organic multi-layer on the electrode surface. X-ray Photoelectron Spectroscopy (XPS), together with Fourier-Transform Infrared Spectroscopy (FTIR) analyses, further evidenced the presence of carboxylic groups onto modified FTO electrodes.