Reactive sputtering deposition of Co3O4 films and an evaluation of its use as an electrochemical sensor for ascorbic acid

Co3O4 films have been deposited using reactive DC magnetron sputtering onto fluorine-doped tin oxide (FTO) and fused silica (SiO2). X-ray diffraction measurements confirmed the spinel Co3O4 phase. The surface roughness of the films were 4 nm and 20 nm for SiO2 and FTO substrates, respectively, as measured by atomic force microscopy. Optical transmission spectra of Co3O4 films show strong absorption in the near-infrared and visible regions. The photoconductivity response of SiO2/Co3O4, using 405 nm excitation, measured at room temperature is much smaller than the observed at 10 K. The electrochemical activity of the FTO/Co3O4 for the oxidation reaction of the ascorbic acid (AA) was investigated by differential pulse voltammetry and chronoamperometric. A model for the oxidation, based on density functional theory calculations for the electronic structure of the AA, is proposed. The set of results show that the assembled FTO/Co3O4 electrode can be used as an alternative and remarkable-performance non-enzymatic device to ascorbic acid electrooxidation.