Uniform ZnO-TiO2 based nano-arrays for enhanced acetone monitoring performance: A light assisted amperometric sensing approach

Well-aligned ZnO-TiO2 core–shell nano-arrays (NAs) were synthesized by uniformly coating a thin layer of TiO2 (either ∼ 30 or ∼ 50 nm) on the ZnO NAs. The TiO2-coated ZnO NAs were annealed carefully to preserve the ZnO-TiO2 core–shell NA structure and to limit the formation of any mixed metal oxides (i.e., zinc titanate: ZnxTiOy). The ZnO-TiO2 core–shell NAs acetone gas sensing response was investigated by measuring the current when applying bias voltages ranging between 0.1 and 9 V DC, with and without ultraviolet (UV) illumination. The sensitivity, selectivity, and repeatability at operating temperatures ranging from 45 to 350 °C are analyzed and discussed in detail. The ZnO-TiO2 core–shell NAs sensors under UV light illumination significantly improved sensing performance compared to dark conditions. At 45 °C, the 50 nm TiO2-coated ZnO NAs sensor showed a limit of detection (LoD) of 16 ppb under UV illumination, highlighting its utility in applications requiring fast, accurate detection of acetone vapor.