Enhancement in TiO2 Nanotubes Based Electrochemical Sensors via Synergistic Effect of TiCl4 Surface Engineering

Abstract

The surface properties of nanostructures play a vital role in defining the electrical and optical properties of nanomaterials needed for various applications. In this study, the TiCl4 surface treatment approach was used to enhance the performance of TiO2 nanotubes (T-NTs) based electrochemical sensors. The TiCl4 treated TiO2 nanotubes and pristine TiO2 nanotubes were deposited with a glucose-sensing mediator (Cu2O nanoparticles (NPs)), and a systematic comparison of their performances using cyclic voltammetry (I-V) curves, Nyquist plot, Mott-Schottky plot, chronoamperometry (I-T) curves, and sensitivity curves are presented. The TiCl4 treated sensors demonstrated 2 times higher sensitivity of 0.4 mA mM-1 cm-2 and 2.5 times lower limit of detection of 80 μM, whereas the untreated nanotubes-based sensors had lesser sensitivity of 0.19 mA mM-1 cm-2 and a higher limit of detection of 200 μM. Further, the treated substrates exhibited a higher donor charge density of 8.79 x 1021 cm-3 in comparison to plain T-NTs (6.5 x 1021 cm-3). The enhanced electrocatalytic performance of the surface-treated sensor was due to the formation of an additional TiO2 layer over the surface of nanotubes which reduced the surface defects and introduced Ti3+ ion in the nanotubes. This resulted in improved electronic contacts of T-NTs with the Cu2O NPs, increasing donor charge density, reduced band-gap, and yielded a three-fold enhancement in electrical conductivity, thereby increased the overall electrochemical sensing performance. Thus, the strategy of TiCl4 surface modification on TiO2 nanotube arrays is effective in enhancing the performance of T-NTs based electrochemical sensors.