A novel sensing platform based on self-doped TiO2 nanotubes for methylene blue dye electrochemical monitoring during its electro-Fenton degradation

Abstract

The synthesis of a self-doped TiO2 nanotubes (SD-TNT) electrode and its potential applicability as a sensing platform electrode for voltammetric determination of methylene blue (MB) dye is reported. Highly ordered TiO2 nanotubes vertically oriented to the titanium surface were grown and the electrochemical doping did not change the morphology of the TNT. Raman spectroscopy demonstrated that the electrochemical doping of TNT promoted a blue shift of the Eg1 mode (from 152 to 158 cm−1) which results in an increased conductivity due to the phonon confinement resultant from the formation of non-stoichiometry Ti3+ donor states. The structural changes allowed the application of SD-TNT as a voltammetric sensor of MB without any UV irradiation. The SD-TNT electrode allowed an efficient quantification of MB, with a limit of detection of 0.48 and 0.90 μmol L−1 when considered the oxidation and reduction peak, respectively. Then, SD-TNT electrode was applied to the monitoring of MB concentration during electro-Fenton oxidation. MB removal fitted well with pseudo-first-order kinetics, suggesting a constant formation of •OH radicals and oxidation of MB. These results revealed that the SD-TNT is a versatile, simple, and promising material for the voltammetric determination of synthetic dyes.