Triple-mode fluorescent anti-counterfeiting and temperature sensing properties of lead-free double perovskites Cs2NaErCl6: Yb3+, Bi3+ microcrystals

In this paper, Cs 2 NaErCl 6 double perovskites microcrystals (MCs) co-doped with Yb 3+ and Bi 3+ are successfully synthesized by a simple “dissolving-drying” method. When excited at 379 nm, 808 nm and 980 nm, the MCs show strong red, green and yellow light, respectively, which can be well distinguished by the naked eyes. On this basis, two kinds of systems are designed with doped/undoped MCs for triple-mode fluorescent anti-counterfeiting and information encryption of numbers and characters. The results indicate that our MCs are not only beneficial to the application of fluorescent anti-counterfeiting, but also greatly improve the security of anti-counterfeiting. In addition, we evaluate the temperature sensing performance of these MCs by fluorescence intensity ratio technique. The samples show a high relative sensitivity as 3.8 %/K at 243 K. The results show that the samples have multi-functional applications in the fields of fluorescent anti-counterfeiting and temperature sensing, and this work will broaden the application fields of lead-free double perovskites in fluorescent anti-counterfeiting and temperature sensing.