In this work, highly regular TiO₂ nanorod array films were synthesized in situ on FTO by a facile hydrothermal method, and then ZnO shell layers were grown on the surface of the nanorods to form a core-shell structure via an ion-layer adsorption-reaction way. Compared to the TiO₂ nanorods, the prepared TiO₂/ZnO nanocomposites exhibited enhanced ethanol sensing performances, including a low working temperature, higher sensitivity, and faster response capability. The optimum sensor based on 2c-TiO₂/ZnO exhibited the maximum response value of 30.85 toward 50 × 10⁻⁶ C₂H₅OH at 340 ℃, which was almost 4.15 times higher than that of the TiO₂ sensor. The improved ethanol sensing mechanism was discussed in relation to the unique nanorod array structure and the heterojunctions between TiO₂ and ZnO.

The timely and effective detection of CO and CH₄ is critical as the explosion and poisoning of them can bring serious potential risks to coal mining. In this study, combining metal oxide semiconductors with noble metals offers a promising route to achieve this target. Hierarchical porous Pd modified In₂O₃ nanoflowers were prepared via two-step hydrothermal method and exhibited dual detection of CO and CH₄ at different temperatures. The material has been characterized by a number of advanced techniques and the results indicate that Pd modified In₂O₃ are hierarchical porous nanoflowers structure consisting of pores of approximately 1.8 nm in size. The sensing properties results show that the Pd modified In₂O₃ based sensor exhibits temperature-dependent dual selectivity detection of CO at 280 ℃ and CH₄ at 340 ℃. In addition, the Pd modified In₂O₃ sensor display higher sensing response of CO (5.824 for 100 ppm) and CH₄ (1.162 for 1000 ppm), fast response and recovery time, as well as good repeatability, which demonstrating the great potential for practical application. Such good gas-sensing performance are mainly attributed to the unique flower-like structure, the presence of porosity on the sample surface, and the catalytic effect of Pd.