Laser-Splashed Plasmonic Nanocrater for Ratiometric Upconversion Regulation and Encryption

Upconversion nanoparticles (UCNPs) with exceptional optical properties have emerged as a new paradigm for data encryption through multicolor coding, lifetime tuning, and excitation light phasing. However, in addition to low internal quantum efficiency, the utility of UCNPs for data encryption is largely hampered by the requirement of multiple sets of UCNPs of complex compositions with specifically tailored optical properties. Herein, it is found that metal-insulator-metal (MIM) configurations are capable of regulating upconversion emission of UCNPs through programmable geometry-dependent plasmonic features of laser-splashed submicron cavities. Furthermore, a ratiometric encryption strategy by regulating the ratio of dual-band emission of a single set of UCNPs of fixed composition placed within the plasmonic MIM configuration is demonstrated. High-throughput encryption and decryption through the luminescence ratiometric strategy can be achieved in a facile laser writing fashion with upscalability and sub-micrometer-scale precision. This demonstration opens a new route to luminescence modulation with large encoding capacity and underpins potential applications of UCNPs in multiplexed data storage and information encryption.