Ultrasensitive turn-on luminescence humidity sensor based on a perovskite/zeolite composite

Recently, the detection and quantification of humidity has attracted great interest, but for fluorescence sensing of humidity, it is still a challenge to achieve high-performance. Here, we report an ultrasensitive and high-performing luminescence humidity sensor based on perovskite/zeolite composite, Cs4PbBr6/FAU-Y. The zeolite FAU-Y acts as a support for dispersing amorphous Cs4PbBr6 nanoparticles (11 +/- 2 nm), which rapidly undergo a moisture-mediated transformation into a highly luminescent CsPbBr3 perovskite, due to the hydrophilic nature of the zeolite substrate. The composite exhibits strong fluorescence response ((I-I-0)/I-0) (992 for 98% RH, 91.7 for 7% RH), good linearity, low detection limit (0.56% RH), while producing highly reproducible and stable optical signals. Test paper embedded with the moisture sensitive composite yields a simple and reliable naked-eye method for detecting moisture exposure within anhydrous products and dry storage environments. This work showcases a unique concept to develop turn-on humidity sensors based on the bright metal halide perovskite luminescence, thus promoting innovative practical applications outside their typical scope of applications such as solar cells, photodetectors, or light emitting diodes (LEDs).