Vacancy-Induced Electron Redistribution Boosts NO₂ Sensing in CdSe Nanoplatelets via Defect-Mediated Charge Transfer

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.