Multi-mode tunable luminescence in Bi3+-activated oxyfluoride phosphors for multi-level anti-counterfeiting applications

Abstract

Phosphors exhibiting multi-mode tunable luminescence have attracted significant attention due to their potential application in multi-level anti-counterfeiting. However, most luminescent materials only respond to a single external stimulus, hindering their practical applications. Herein, we report a series of novel oxyfluoride phosphors Sr₃Ga_1−xGe_xO_4+xF_1−x:1%Bi³⁺ (x = 0–0.75) with multiple response modes and tunable emitting colors through chemical unit co-substitution of [Ge⁴⁺ + O²⁻]²⁺ → [Ga³⁺ + F⁻]²⁺. With increasing co-substitution concentration of the [Ge⁴⁺ + O²⁻]²⁺ unit from x = 0 to 0.75, the emission peak position red-shifts from 450 to 525 nm along with the broadened bandwidth from 70 to 170 nm. Under the excitation at 365 nm, the emitting color can be tuned from blue to yellow–green. Specifically, controlling the excitation wavelength and temperature allows the luminescence color to be regulated in a large gamut. Based on the multi-mode tunable luminescence of Sr₃Ga_1−xGe_xO_4+xF_1−x:1%Bi³⁺ phosphors, the potential applications in the multi-level anti-counterfeiting field have been demonstrated. This work enriches the family of multi-mode luminescent materials and allows novel anti-counterfeiting applications.