Self-doped TiO2 nanotube electrodes: A powerful tool as a sensor platform for electroanalytical applications

The use of TiO2 nanotube (TiO2NTs) electrodes as anodes without UV irradiation has been described herein for electroanalytical purposes. Although semiconductors of n-type, such as TiO2NTs, do not offer any potential electrochemical response at the anodic region, they can be activated once they are a priori subjected to a simple cathodic polarization (P-TiO2NTs) and used to follow the oxidation reaction without any other modification. The best polarization conditions were obtained at 0.1 mol L-1 KH2PO4 pH 10 at -2.5 V for 5 min, and the polarized TiO2 electrode was applied in the Fe(CN)(6)(4) redox probe oxidation and also p-phenylenediamine (PPD) determination as models of species which undergo oxidation. Following the optimization of the parameters, analytical curves for Fe(CN)(6)(4) and PPD were constructed in the range of 2.5 x 10(-5) to 5 x 10(-3) mol L-1 with a detection limit at 7.23 x 10(-6) mol L-1 and 0.500 to 98.6 x 10(-6) mol L-1 with a detection limit at 0.558 x 10(-7) mol L-1 using linear sweep voltammetry and linear sweep adsorptive stripping voltammetry techniques, respectively. Lastly, the figures of merit for PTiO2NT and conventional glassy carbon electrodes are compared. Our results show that P-TiO2NT electrodes can be used as an excellent platform for the development of electrochemical sensors. (C) 2017 Published by Elsevier Ltd.