Zinc titanate nanoarrays with superior optoelectrochemical properties for chemical sensing.

In this report, the gas sensing performance of zinc titanate (ZnTiO3) nanoarrays (NAs) synthesized by coating hydrothermally formed zinc oxide (ZnO) NAs with TiO2 using low-temperature chemical vapour deposition (CVD) is presented. By controlling the annealing temperature, diffusion of ZnO into TiO2 forms a mixed oxide of ZnTiO3 NAs. The uniformity and the electrical properties of ZnTiO3 NAs made them ideal for light-activated acetone gas sensing applications for which such materials have not been previously reported. The acetone sensing performance of the ZnTiO3 NAs is tested by applying a different bias potential between 0.1 and 9 V DC was investigated with the sensors operating amperometric mode. An increase in the applied bias was found to increase the sensitivity of the device toward acetone under both photoinduced and non-photo induced (dark) conditions. When illuminated with 365 nm UV light, the sensitivity was observed to increase 3.4 times compared to under dark conditions towards 12.5 ppm acetone at 350 °C with 9 V bias. The ZnTiO3 NA based gas sensors have not only increased sensitivity towards acetone under light but also significantly reduced the adsorption time, desorption time and limit of detection (LoD) when operated under dark conditions. For example, the limit of detection (LoD) of the sensor in the dark and under UV light at 350 °C with a 9 V bias is found to be 80 and 10 ppb, respectively. The described approach also enabled acetone sensing at operating temperature down to 45 °C with repeatability of > 99% and LoD of 90 ppb when operated under light, thus indicating that the ZnTiO3 NAs are a promising material for low concentration acetone gas sensing applications.