Excitation-dependent afterglow evolution based on constructing dual crystal field glass ceramics

Distinctive luminescent properties and excellent stability of long persistent luminescent (LPL) glass-ceramic hold promise for anti-counterfeiting and encryption applications. However, rational synthesis and a deep understanding of the precipitation of dual-phase microcrystals in glass substrate to improve the encryption level remain challenging. Here, we carefully designed the components based on the phase diagram and combined them with the glass-forming region. By utilizing the different crystallization behaviors of SrAl2O4 and CaAl2O4 in the glass matrix to realize dual crystals coexistence in a borate glass matrix, which provides different crystal field environments for Eu2+ luminescence, thus obtaining excitation-dependent tunable LPL characteristics in a single sample. Mechanism studies unveiled that this excitation-dependent behavior arises from the differential capture of charge carriers by defect oxygen vacancies in the sample when charged with different laser sources, providing a channel for multimode anti-counterfeiting encryption. This strategy of constructing a double crystal field in a glass matrix overcomes the stringent requirements of a single heat treatment method for the crystallization temperature of biphasic crystals, which could become a stable and promising advanced anti-counterfeiting encryption material and provide new insights into the multi-band luminescence regulation of rare earth ions.