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Dual-mode of Fluorescence Turn-on and Wavelength-shift for Methylamine Gas Sensing Based on Space-confined Growth of MAPbBr3 Perovskite Nanocrystals.

The defect-tolerant nature of lead halide perovskites renders outstanding luminescence by simply space-confined growth in nanopores. The fluorescence turn-on and wavelength-shift phenomena could be found in the formation of MAPbBr3 nano-crystals in hollow SiO2 nanospheres triggered by the reaction between methylamine (MA) gas and HPbBr3/PbBr2@SiO2 nan-ospheres. The enhanced fluorescence intensity is linearly with the MA concentration in the range of 1.0-95 ppm with a LOD of 70 ppb (S/N = 3). In addition, the maximum emission wavelength is consistently red-shift from 478.7 nm to 510.6 nm as the MA concentration increases from 1.0 ppm to 95 ppm, imparting the potential for colorimetric sensing. By combining the fluorescence turn-on and colorimetric sensing modes, the flexible method meets the demands for visual discrimination and point-of-care determination with portable devices.