Site occupation and upconversion process enabled multicolor emission in a Gd3GaO6:Bi3+,Er3+ phosphor for quad-mode anti-counterfeiting

The development of multicolor emissions in a single phosphor poses a significant challenge with practical implications for high-security-level multi-mode anti-counterfeiting. Herein, a novel Gd3GaO6:Bi3+,Er3+ phosphor with multicolor emissions was successfully prepared and its structural and luminescence properties were investigated. In Bi3+-doped phosphors, the Bi3+ ions occupy two different Gd3+ sites and exhibit blue-violet light at 409 nm and orange emission at 594 nm, respectively. Besides, Er3+-doped phosphors show green downshifting luminescence under the excitation of 378 nm, green upconversion luminescence under the excitation of 980 nm, and yellow upconversion luminescence under the excitation of 1530 nm. The Gd3GaO6:Bi3+,Er3+ phosphor displays the emissions of both Bi3+ and Er3+ under the specific excitation wavelengths. On this basis, a quad-mode anti-counterfeiting material with high security levels has been designed and manufactured, and different luminescence patterns can be obtained under the excitations of 302, 365, 980 and 1530 nm. This work not only presents a well-performing phosphor for advanced anti-counterfeiting, but also paves the way for designing multicolor emission in one phosphor.