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 × 10−5 to 5 × 10−3 mol L−1 with a detection limit at 7.23 × 10−6 mol L−1 and 0.500 to 98.6 × 10−6 mol L−1 with a detection limit at 0.558 × 10−7 mol L−1 using linear sweep voltammetry and linear sweep adsorptive stripping voltammetry techniques, respectively. Lastly, the figures of merit for P-TiO2NT 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.