Optimization of ZnO-TiO<sub>2</sub> Nanocomposites Sensor for Ultra-Sensitive H<sub>2</sub>S Detection at Low Temperature

In this study, ZnO-TiO 2 nanocomposites with varying molar ratios were synthesized using a hydrothermal method and characterized for H 2 S gas sensing applications. Thick films of the nanocomposites were fabricated using a screen-printing technique, and their gas sensing performance was evaluated at different operating temperatures. The diffraction peaks of ZnO and TiO 2 are hexagonal (rutile), and tetragonal (anatase) phase, respectively. The crystallite sizes were determined to be 37.34 nm for 1M ZnO : 1M TiO 2 composition, and 45.17 nm, 44.03 nm, 41.22 nm, 36.14 nm, and 36.65 nm for the (1M : 9M, 3M : 7M, 7M : 3M, 9M : 1M, and 0.1M CuCl 2 -doped in 1M ZnO : 1M TiO 2 ) compositions, respectively. SEM and EDAX analyses revealed formation of heterogeneous structure with well-distributed nanospheres and nanorods. The I-V characteristics of ZnO-TiO 2 thick films show a proportional but slightly non-linear response to voltage, indicating a mix of ohmic and non-ohmic conduction. The average thickness of the thick film of 1M ZnO : 1M TiO 2 sample is 29 (µM). The gas sensing performance was evaluated at different operating temperatures and among the compositions studied, the 7M ZnO : 3M TiO 2 thick film exhibited superior sensitivity, selectivity, and response to 286 ppm H 2 S gas at 40°C. These findings demonstrate the potential of ZnO-TiO 2 nanocomposites as highly selective and low-temperature H 2 S sensor for industrial and environmental monitoring applications.