Electron Trap Induced Multimodal Luminescence and Photochromism for Optical Thermometry and Information Encryption

Achieving multimodal response to various stimuli in a single luminescent material is crucial for advanced anti-counterfeiting and encryption. However, the simultaneous realization of multimodal luminescence and photochromism (PC) properties in one matrix remains a significant challenge. Here, a multimodal luminescent ceramic phosphor was developed via Bi 3+ doping into inverse spinel structure MgGa 2 O 4 lattice, which exhibits response upon ultraviolet (UV), near-infrared (NIR), X-ray, and thermal stimuli, specifically showing temperature-dependent multicolor luminescence (blue-white-red), high thermal stability of 397 nm emission (90%@473 K), and rapid PC properties (within 1 s). Through experimental analysis and density functional theory (DFT) calculations reveals that the multi-color luminescence is mainly associated with interstitial oxygen and antisite defects, whereas PC is related to color centers formed by oxygen vacancies; anti-thermal quenching originates from the compensation of non-radiative luminescence by electrons in trap levels at high temperatures. Based on these findings, precise control over the optical properties of the MgGa 2 O 4 :Bi 3+ ceramic phosphors are achieved for applications such as temperature monitoring and information encryption. This work provides valuable insights for the design of multimodal stimuli-responsive systems.