An excitation wavelength-dependent color-tunable La4GeO8: Bi3+, Er3+ phosphor for multicolor anticounterfeiting

Stimulation-responsive luminescent materials have attractd intense attention due to their excellent optical properties in the anticounterfeiting application. At present, most the anticounterfeiting materials are based on single luminescence and fixed excitation patterns, resulting in a poor anticounterfeiting effect. Therefore, developing multimodal anticounterfeiting materials that change their luminous color under different wavelength stimuli has become a significant challenge. In this work, we reported a multimodal luminescent La4GeO8: Bi3+, Er3+ phosphor, which could emit white, blue-green, baby blue and orange-yellow light at the excitation wavelength of 250–430 nm. Moreover, it also showed green upconversion (UC) luminescence when irradiated with near-infrared (NIR, 980 nm and 808 nm) lasers. Notably, the material exhibited good humidity resistance and stability. Based on these integrated features, we designed an anticounterfeiting device. The results suggested that the anticounterfeiting device could quickly realize multimodal anticounterfeiting using common light source {NIR (808 nm or 980 nm) laser and ultraviolet (UV) lamp}. These combined characteristics will be difficulty to forge and show high security in anticounterfeiting applications.