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 TiCl
₄
surface treatment approach was used to enhance the performance of TiO
₂
nanotubes (T-NTs) based electrochemical sensors. The TiCl
₄
treated TiO
₂
nanotubes and pristine TiO
₂
nanotubes were deposited with a glucose-sensing mediator (Cu
₂
O 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 TiCl
₄
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 TiO
₂
layer over the surface of nanotubes which reduced the surface defects and introduced Ti
³⁺
ion in the nanotubes. This resulted in improved electronic contacts of T-NTs with the Cu
₂
O 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 TiCl
₄
surface modification on TiO
₂
nanotube arrays is effective in enhancing the performance of T-NTs based electrochemical sensors.