Sunlight-activated long persistent luminescence in the ultraviolet-B spectral region from Bi3+-doped garnet phosphors for covert optical tagging

A series of Bi³⁺-doped garnet-based UVB persistent phosphors have been developed, which can be conveniently charged by either a standard 254 nm lamp or natural sunlight, producing persistent UVB light emission peaking at 313 nm.