Construction of energy transfer channels from [SbCl6]3− to Ln3+ (Ln3+ = Ho3+, Er3+) in Cs2NaGdCl6 for advanced anti-counterfeiting materials

Abstract

The existence of energy transfer channels from the self-trapped exciton (STE) emission to lanthanide (Ln³⁺) ions in double perovskites (DPs) opens up new possibilities for high security anti-counterfeiting applications. In the present investigation, we synthesized Sb³⁺/Ho³⁺/Er³⁺ doped Cs₂NaGdCl₆ rare-earth-based DPs using a simple solvothermal method, whose luminescence could be quenched by water and restored after drying. The efficient down-shifting (DS) red emission from the 4f–4f transition of Ho³⁺ was enhanced 8-fold due to the energy transfer of STEs → Ho³⁺ ions via Sb³⁺ sensitization. The DS and up-conversion (UC) dual-mode multicolor emissions were obtained by further introducing Er³⁺. Specifically, the DS luminescence of the tri-doped sample under the UV region and that under 448 nm irradiation were white and red, respectively; and the UC luminescence under 980 nm irradiation was green. In view of their stimulus response to water and dual-mode multicolor luminescence properties, advanced anti-counterfeiting materials based on the obtained samples were designed.