Upconversion Luminescence via Anion Exchange in Perovskite Quantum Dots for Anticounterfeiting Inkjet Printing

Lanthanide-doped upconversion nanoparticles (UCNPs) and cesium lead halide perovskite quantum dots (PeQDs) are highly compatible with each other: UCNPs produce anti-Stokes upconversion luminescence (UCL) under near-infrared (NIR) excitation and the emissive profiles of PeQDs can be conveniently tuned by varying the halide composition ratio. Therefore, in this study, UCNPs and PeQDs are mixed together, producing colorful UCL under 980 nm laser excitation. In addition, ZnI2 is used to vary the halide composition ratio of PeQDs and manipulate UCL in situ, thus adding more flexibility in UCL regulation. Finally, based on the above-mentioned discussion, a double-encrypted anticounterfeiting pattern is generated via sequentially printing ZnI2 solution and UCNP suspension on an A4 paper. Using PeQDs as the decrypting reagent, under the NIR excitation and decryption channel, the hidden information can be fully decrypted. The combination of UCNPs and PeQDs greatly expands the upconversion possibility, offers more feasibility in UCL regulation, and further promotes the practical applications.

Automated summary

This study demonstrates the compatibility and interaction between UCNPs and PeQDs, leading to the generation of colorful UCL by mixing them. The emission profiles of PeQDs can be conveniently tuned using ZnI2. A double-encrypted anticounterfeiting pattern is achieved by printing specific solutions on paper, and the hidden information can be decrypted using a specific decrypting reagent.