Time-dependent Phosphorescence Color of Carbon Dots in Binary Salt Matrices through Activations by Structural Confinement and Defects for Dynamic Information Encryption

The emergence of time-dependent phosphorescence color (TDPC) materials has taken information encryption to high-security levels. However, due to the only path of exciton transfer, it is almost impossible to obtain TDPC for chromophores with a single emission center. Theoretically, in inorganic-organic composites, the exciton transfer of organic chromophores depends on the inorganic structure. Here, we assign two structural effects to inorganic NaCl by metal (Mg²⁺ or Ca²⁺ or Ba²⁺) doping, which triggers the TDPC performance of carbon dots (CDs) with a single emission center. The resulting material is used for multi-level dynamic phosphorescence color 3D coding to achieve information encryption. The structural confinement activates the green phosphorescence of CDs; while the structural defect activates tunneling-related yellow phosphorescence. Such simply doped inorganic matrices can be synthesized using the periodic table of metal cations, endowing chromophores with tremendous control over TDPC properties. This demonstration extends the design view of dynamic luminescent materials.