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

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 $80 \mu \text{M}$ , whereas the untreated nanotubes-based sensors had lesser sensitivity of 0.19 mA mM⁻¹ cm⁻² and a higher limit of detection of $200 \mu \text{M}$ . Further, the treated substrates exhibited a higher donor charge density of $8.79\times10$ ²¹ cm⁻³ in comparison to plain T-NTs ( $6.5\times10$ ²¹ 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.