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 NaErF4‐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. [ABSTRACT FROM AUTHOR]