Enhanced persistent luminescence afterglow in Ca₂Ga₂GeO₇: Tb3+ phosphor via Gd3+ or Y3+ co-doping for latent fingerprint detection and anti-counterfeiting applications

In this study, the persistent luminescence emission from Tb³⁺-doped Ca₂Ga₂GeO₇ phosphors was significantly enhanced by co-doping with Gd³⁺ and Y³⁺ ions, and their potential for latent fingerprint detection and anti-counterfeiting applications was thoroughly investigated. The phosphors were synthesized using a high-temperature solid-state reaction method. The afterglow intensity and persistence improved after co-doping with Gd³⁺ and Y³⁺ ions, with optimal samples exhibiting a persistence of over 6000 seconds. Thermoluminescence (TL) investigations confirmed deeper trap states presence, facilitating extended energy storage and improved afterglow performance. Photoluminescence (PL) and cathodoluminescence (CL) analyses elucidated specific energy transfer mechanisms among the dopants. At the same time, TL deconvolution highlighted the role of dopant-induced defect states in enhancing trapping and recombination processes. Furthermore, the co-doped samples exhibited bright green emissions with very high intensity. The practical utility of the prepared phosphors was demonstrated in two key applications: latent fingerprint (LFP) detection on non-porous surfaces under UV light and as security ink for anti-counterfeiting purposes. The phosphors provided excellent contrast, clarity, and minutiae details, capturing all three levels (1, 2, and 3) of LFP features essential for forensic identification. Based on these findings, Gd³⁺ and Y³⁺ co-doped Ca₂Ga₂GeO₇: Tb³⁺ phosphor is promising for persistent luminescence-based applications in forensic science and anti-counterfeiting.