ZnS:Er3+/Yb3+ phosphor for optical temperature sensing and dual-mode anti-counterfeiting

Optical temperature sensors have become a research hotspot in recent years due to their non-contact feature. In this study, Er3+/Yb3+ co-doped ZnS phosphors (1:3, 1:6, 1:9, 1:12, 1:15, 1:19) were prepared by co-precipitation method. The up-conversion and down-conversion luminescence performance of the phosphors was studied. It was found that the luminescence performance is optimized when the doping molar ratio is 1:9. Based on the fluorescence intensity ratio technology of non-thermal coupling energy level, the temperature sensing characteristics of ZnS:Er3+/Yb3+ (1:9) phosphors were studied in the temperature range of 313–533 K. The results show a maximum absolute sensitivity of 1.9 % K−1 and a maximum relative sensitivity of 2.7 % K−1. In terms of multifunctionality, this work also designed a flexible film based on thermoplastic polyurethane (TPU) to explore its anti-counterfeiting properties. The results of this work demonstrate the great potential of ZnS:Er3+/Yb3+ phosphors for optical temperature measurements and anti-counterfeiting.