Anticounterfeiting application of Bi4TaO8Cl: Yb3+/Er3+ nano-phosphor designed by molten salt method for dual-mode upconversion luminescence

In recent years, upconversion luminescent materials doped with rare-earth ions have been widely used in anti-counterfeiting applications. However, in practical applications, single-mode photoluminescence is difficult to meet the increasingly complex anti-counterfeiting requirements of today's society. In this article, dual-mode-excited, dual-color emitting Yb3+/Er3+ co-doped Bi4TaO8Cl nano-phosphor has been successfully synthesized via the one-step molten salt method. Bi4TaO8Cl: Yb3+/Er3+ nano-phosphor can emit green and red luminescence under 980 nm excitation, and the emission color changes from green to red by controlling the dopant concentration; whereas under 1550 nm excitation, it is mainly a single band red emission. The multicolor emission improves the security of multimode anticounterfeiting. The possible UC mechanisms were investigated under different excitation light sources at 980 and 1550 nm. Meanwhile, the anti-counterfeiting properties of the prepared nano-phosphor were evaluated according to the luminous intensity ratio of red and green light. The results demonstrate that Bi4TaO8Cl: Yb3+/Er3+ nano-phosphor will be expected to have excellent applications in the field of multimode anticounterfeiting.