Cascaded Photon Confinement-Mediated Orthogonal RGB-Switchable NaErF4-Cored Upconversion Nanoarchitectures for Logicalized Information Encryption and Multimodal Luminescent Anti-Counterfeiting

Orthogonal upconversion nanoparticles (UCNPs) have received increasing research attention due to their unique optical performance. However, the establishment of the orthogonal UCNPs emitting primary red/green/blue (RGB) UCL remains a great challenge. Herein, RGB-switchable NaErF 4 -cored core–multishell UCNPs (RGB-UCNPs) are constructed through the coordinative implementation of outside-in cascaded photon harvesting and interfacial energy-transfer (IET) inhibition. By modulating several constructional factors, the power-density-independent red, green, and blue luminescence in high color purity is readily available in the elaborated RGB-UCNPs under 1550, 808, and 980 nm excitations, respectively. Notably, full-color emissions, involving red, yellow, green, cyan, blue, magenta and white, are dynamically implemented in this single architecture through manipulating the excitation power of the combined 1550/808/980 nm lasers. These emission profiles of RGB-UCNPs make them promising in broad photonic applications. As a proof of concept, the viability of the logicalized information encryption strategy and smartphone APP-assisted multimodal luminescent QR code anti-counterfeiting technique is demonstrated, which are both established based on directly useable RGB-UCNPs with assistance of a self-built combined laser system. This work not only opens up a new avenue to gain RGB-switchable UCL and flexible full-color output in a single nanostructure, but also provides enlightenment for developing the application scenarios of multicolor-tunable UCNPs.