Energy transfer engineering for programmable fluorescence dynamics in CsPbBr3 perovskite: Toward multimode anti-counterfeiting

Smart fluorescent materials with tunable fluorescence in response to external stimuli are of great interest for anti-counterfeiting applications. Herein, we develop a photoresponsive fluorescent material (PRFM) SPD-CsPbBr 3 @PMMA that integrates perovskite CsPbBr 3 with photochromic spiropyran (SPD) in poly(methyl methacrylate) (PMMA), exhibiting multimode fluorescence outputs for advanced anti-counterfeiting applications. The blue-excitable CsPbBr 3 nanocrystals enable SPD-CsPbBr 3 @PMMA a stable green fluorescence at 450 nm excitation wavelength. Ultraviolet light irradiation of SPD-CsPbBr 3 @PMMA induces the isomerization of SPD from closed-ring to open-ring form and subsequently gives a stable red fluorescence. Fluorescence decay spectra and theoretical calculations indicate that an efficient energy transfer occurs from CsPbBr 3 to the open-ring SPD, thereby leading to significant changes in fluorescence. Upon irradiation with visible light (400–750 nm), SPD is reverted to closed-ring form, accompanied by the restoration of green fluorescence. SPD-CsPbBr 3 @PMMA can exhibit complex and tunable fluorescence changes under room light, blue light, and ultraviolet light modes, making it exceptionally suited for anti-counterfeiting applications. A novel strategy for information anti-counterfeiting by combining SPD-CsPbBr 3 @PMMA with Morse code and other innovative anti-counterfeiting platforms have been successfully developed. Overall, this study introduces an innovative approach to constructing multimode PRFMs, elucidates the design principles underlying fluorescence-tunable perovskite, and inspires further development in advanced anti-counterfeiting materials.