​Guogang Li/Jun Lin's Group Realizes Up-conversion/ Perovskite Core-Shell Dual-Mode Luminescence for Anti-counterfeiting

Traditional physical anti-counterfeiting labels have limited coding ability and are easy to reproduce, so we put forward higher requirements for new anti-counterfeiting technologies. Chemical anti-counterfeiting labels can be used as safer anti-counterfeiting labels due to high technical barriers. Combining materials with different luminescent properties is an idea to achieve dual-mode or multi-mode luminescence anti-counterfeiting.

Li's group from China University of Geosciences (Wuhan) cooperated with Lin's group from Changchun Institute of Applied Chemistry designed an up-conversion/perovskite core-shell structure with dual-mode luminescence. The synthesis of core/shell metal halide perovskite/up-conversion nanocrystal composite structures is challenging due to the lattice mismatch and environmental sensitivity of perovskite. Perovskite nanoparticles in previous literatures are usually randomly embedded on the surface or inside of upconverted nanocrystals or the two are simply mixed together. In this study, the UCNP@CsMnCl₃core-shell nanocomposites were successfully synthesized with the up-conversion nanoparticles (UCNPs; NaYF₄: Er³⁺, Yb³⁺) as the core and lead-free perovskite (CsMnCl₃) as the shell.

The growth process and luminescence mechanism of CsMnCl₃nanocrystals was disscussed in detail, determined the growth direction of CsMnCl₃by TEM and photophysical studies, and assigned the sources of its three luminescence centers at low temperature (confinement effect, surface state and Mn²⁺). The understanding of CsMnCl₃provides the basis for the preparation of UCNP@CsMnCl₃core-shell structure. By means of selected area electron diffraction and XRD, we observed the change of CsMnCl₃lattice after the formation of heterostructure. Due to the quasi-zero-dimensional structure of CsMnCl₃, its lattice has strong tensile properties, and the lattice of CsMnCl₃after stretching can be well matched with the lattice of UCNP. Finally, we designed UCNP@CsMnCl₃as a dual-mode anti-counterfeiting label by using different excitation sources (ultraviolet light and 980 nm laser) to excite two different lights emitted by UCNP@CsMnCl₃.

Figure 1. Dual-mode luminescence of core-shell UCNP@CsMnCl₃.

This work attempts to apply lead-free perovskites in anti-counterfeiting and expands the application scope of metal halide perovskites. The article was published inAngewandte Chemie International Editionunder the title "Core-Shell Structured Upconversion / Lead-Free Perovskite Nanoparticles for Anticounterfeiting Applications".

This research was supported by the National Natural Science Foundation of China. Prof. Guogang Li from China University of Geosciences (Wuhan) and Prof. Jun Lin and Prof. Ziyong Cheng from Changchun Institute of Applied Chemistry are the corresponding authors of this work, and the first author is Dr. Xiao Hui from Changchun Institute of Applied Chemistry.

Article link: https://onlinelibrary.wiley.com/doi/10.1002/anie. 202115136