Defect engineering is crucial for enhancing gas sensors, however, the mechanism by which vacancies amplify sensing signals remains unclear. This study synthesizes hexagonal CdSe nanoplatelets with tunable vacancy density through a NaOH-regulated hydrothermal and calcination process. The optimized sensor demonstrates an outstanding response (R_g/R_a=9.03) to 10 ppm of NO₂ at 120°C, showcasing remarkably quick response-recovery times of 12 and 13 s, respectively, along with an exceptionally low theoretical detection limit of 82.5 ppb. The DFT calculation results indicate that vacancies induce electron redistribution in CdSe, which helps promote charge transfer and enhance surface reactivity. In addition, NaOH regulation simultaneously optimized the material particle size and vacancy density, ensuring the dominant position of active sites in electron capture. This work highlights vacancy-induced electron redistribution as a key mechanism for boosting sensing performance and provides a viable defect-mediation strategy for advanced gas sensors.

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.