A “Turn-on” fluorescence perovskite sensor based on MAPbBr₃/mesoporous TiO₂ for NH₃ and amine vapor detections

Recently, lead halide perovskites have attracted great interest in toxic gas detection, but as gas sensor, it is still a challenge to achieve their high-performance. Here, we propose a novel “turn-on” fluorescence NH₃/amine vapor sensor by depositing the CH₃NH₃PbBr₃ (MAPbBr₃) on the mesoporous TiO₂ (mp-TiO₂) layer. The fluorescence intensity of the sensor increases rapidly within seconds upon exposure to NH₃ gas (72 % at 5 ppm and 988 % at 100 ppm, respectively) with excellent reversibility, high gas selectivity, humidity insensitivity, and regeneration. Moreover, the sensor can be further used for detecting various amine vapors, including methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, and decylamine. We presumed the “turn-on” fluorescence sensing mechanism is that the trace NH₃ or amine molecules could decrease the surface trap defects and facilitate the formation of passivation layer. It will impede the electron-injection into mp-TiO₂, which induces the radiative electron-hole recombination and fluorescence enhancement. This research demonstrates that it is feasible to design a “turn-on” fluorescence gas sensor based on the mp-TiO₂-based perovskite.