Ratiometric Light Conversion of Transition Metal Doped Zinc Gallate Phosphors for Dynamic Anti-counterfeiting Application

Energy transfer (ET)-based ZnGa₂O₄:Mn²⁺, Cr³⁺ phosphors with the capacity for ratiometric light conversion have been designed. The Mn²⁺ and Cr³⁺ ions in the ZnGa₂O₄:Mn²⁺, Cr³⁺ act as ET donors and receptors, respectively, by changing the doping amount of energy receptor Cr³⁺ ions, phosphor materials show different emission colors (green to deep red). The relationship between red and green phosphorescence is ratiometric and linear and, when 254 nm excitation is stopped, the phosphor shows a dark green afterglow. This ET-based ratiometric green-to-red light conversion provides a facile, sensitive and selective method for dynamic anti-counterfeiting.