Suprahydrostable ultrasmall hybrid cuprous halide with pseudo-net protector for wireless light-triggered rewritable transient display and dynamically recoverable encryption

Zero-dimensional (0D) organic-inorganic hybrid metal halides (OIHMHs) are receiving significant attention due to their exceptional photovoltaic properties. However, their applications are restricted by their inferior water stability and undesired particle size. Herein, we synthesized suprahydrostable ultrasmall 0D OIHMHs with an average size of ∼3.4 nm, named (TOA)CuBr2 for the first time. (TOA)CuBr2 nanocrystals exhibit bright fluorescence attributed to self-trapping excitons and demonstrated by density functional theory calculations. It is worth emphasizing that (TOA)CuBr2 displays excellent reversible photoluminescence (PL) response to UV light, temperature, and acid/alkali simultaneously, especially to acid/alkali. The underlying mechanism of the reversibility properties is explained and the reversible PL switch is developed by utilizing the acid/alkali responsive property. Moreover, it is the first demonstration of a real-time rewritable transient display based on 0D OIHMHs with "writing/self-erasing/rewriting" capability under wireless near-infrared light. In addition, encrypted strips prepared by in-situ growth of (TOA)CuBr2 in polydimethylsiloxane show quite stable fluorescence properties in various scenarios. Dynamically recoverable encryption systems are also designed by taking full advantage of the material's multi-response characteristics. Our work provides a strategy for synthesizing suprahydrostable ultrasmall OIHMHs, which will lay a solid foundation for developing their multi-scenario applications in the future.