Time-dependent multicolor evolution of photoluminescence and afterglow in lanthanide-doped gallate

The general stimulus-responsive color modulation method requires both strict control of microstructures and continuous adjustment of specific stimuli conditions to externally manipulate emission color for scientific research and applications. Herein, by hierarchically utilizing the energy transfer processes from traps to luminescent centers, a possible mechanism for the dynamic multicolor evolution in a single material is proposed. This mechanism explains the fundamental principle of the dynamic photochromic behavior and afterglow color variation. A series of Sr3Ga4O9:Ln3+ (SGO, Ln = Dy, Tb, Pr, Sm) phosphors with dynamic photoluminescence (PL) and afterglow color that change over time under a fixed stimulus were developed using the mechanism as a basis for experimental design. The PL dynamically transformed from orange, green or red to blue under 254 nm irradiation in seconds and reversed from blue to orange, green or red after the excitation source was removed. Finally, based on distinctive luminescence properties, their potential application in optical encryption and optical anticounterfeiting was also methodically investigated.