Reversible transformation of all-inorganic copper halide perovskite nanocrystals for anti-counterfeiting

This work reports a CsI stripping/insertion process that enables the reversible transformation between blue-emissive Cs₃Cu₂I₅ and yellow-emissive CsCu₂I₃ upon moisture/evaporation treatment. The successful transformation can be ascribed to the unique space confinement of the SiO₂ matrix and ligand-free feature of perovskite nanocrystals, which can be a good candidate for anti-counterfeiting.