Multicolor Persistent Luminescence for High-Sensitivity Optical Temperature Sensing, Human Motion Detection, and Multimodal Anticounterfeiting Materials

Abstract

Multimodal luminescent materials are widely used in noncontact temperature sensors and fluorescent dynamic anticounterfeiting due to their visible dynamic persistent luminescence and fast optical signal response. To this end, CaY_0.99GaO₄: 0.01 Bi³⁺; CaY_0.92GaO₄: 0.01 Bi³⁺, 0.07Eu³⁺; and CaY_0.96GaO₄: 0.01 Bi³⁺, 0.03Er³⁺ phosphors were prepared using the high-temperature solid-state method. The down-conversion luminescence, up-conversion luminescence, long persistent luminescence, and mechanical luminescence of the materials were studied, achieving multicolor luminescence. It was found that the CaY_0.92GaO₄: 0.01 Bi³⁺, 0.07Eu³⁺ phosphor achieves the maximum relative sensitivity of 1.49% K^–1. These materials show great potential for applications in anticounterfeiting and optical detection. Through density functional theory and electron localization function analysis, multimodal luminescent materials CaYGaO₄: Bi³⁺, Eu³⁺/Er³⁺ were studied. It was found that ion doping leads to a decrease in the band gap and induces the Jahn–Teller effect, creating lower energy channels that accelerate carrier release and enhance optical performance. This is the fundamental reason for the realization of multimodal anticounterfeiting and human motion detection. Subsequently, a novel signal sensing device for human motion detection was developed using the high mechanical luminescence performance of the CaY_0.92GaO₄: 0.01 Bi³⁺, 0.07Eu³⁺ phosphor. The down-conversion luminescence, up-conversion luminescence, long persistent luminescence, and mechanical luminescence properties of CaYGaO₄: Bi³⁺, Eu³⁺/Er³⁺ phosphors were demonstrated for multimodal static–dynamic anticounterfeiting applications. Finally, it was demonstrated that the high stability of the wide defect states in CaYGaO₄: Bi³⁺, Eu³⁺/Er³⁺ multimodal luminescent materials provide a new approach for temperature sensors, human motion detection, information storage, and anticounterfeiting.