Optical thermometry and multi-mode anti-counterfeiting based on Bi3+/Ln3+ and Ln3+ doped Ca2ScSbO6 phosphors

A series of novel Bi3+/Ln3+-activated Ca2ScSbO6 (CSSO) phosphors were synthesized by solid-state method and their luminescent behaviors were investigated in detail. Under the 302 nm excitation, the CSSO:Bi3+ shows remarkable near-ultraviolet photoluminescence with a peak emission at 365 nm. Eu3+-activated CSSO phosphor possesses high efficiency and no obvious reduction of emission intensity even after replacing Sc with Eu completely, which indicates a low-concentration quenching effect. In addition, its emission intensity at 423 K (I423K) still maintains 88 % compared with that of at room temperature (I298K), indicating good thermostability. In contrast, the CSSO:Bi3+ phosphor exhibits a significant reduction in emission intensity, maintaining only 49 % of its luminescence at 423 K (I423K/I298K). By codoping Bi3+ and Ln3+ (Ln = Eu, Tb, Dy, Sm), the energy transfer was observed from the Bi3+ to Ln3+ ions, endowing the CSSO:Bi3+, Ln3+ phosphors with tunable multicolor emissions. Leveraging the differing thermostabilities of the emission spectra for Bi3+ and Ln3+ ions, we designed and assessed a range of sensitive optical thermometers. Among these, the CSSO:Bi3+, Eu3+ phosphors exhibited the best performance, boasting maximum absolute and relative sensitivities of 9.96 % K−1 and 2.002 % K−1, respectively. Additionally, we displayed the multi-mode anti-counterfeiting function of synthesized phosphors, and a multi-color switching system was designed with the advantages of direct visualization and easy identification of encrypted information. These results indicate that Bi3+ and Ln3+ coactivated CSSO phosphor has the potential application for non-contact temperature measurement and anti-counterfeiting.