Generating Strong Circularly Polarized Luminescence from Self‐assembled Films of Chiral Selenium Nanoparticles and Upconversion Nanoparticles

Circularly polarized luminescence (CPL) has garnered significant research attention. Achieving a high luminescence dissymmetry factor (glum) is a key challenge in this field. Herein, we reported, for the first time, the fabrication of a chiral assembled film consisting of chiral D‐/L‐Selenium nanoparticles (D‐/L‐Se NPs) and DSPE‐PEG‐NH2 modified upconversion nanoparticles (DPNUCNPs) with remarkable CPL properties that were generated by the interfacial self‐assembly technique. The chiral Se/DPNUCNPs films, consisting of three layers (3L) of D‐/L‐Se films and 3L DPNUCNPs films, exhibited the highest circular dichroism (CD) response and the strongest CPL signals. Under laser excitation at 980 nm, the 3L D‐/L‐Se/3L DPNUCNPs assembled films displayed symmetric CPL signals between 400 and 600 nm, with a maximum |glum| value of 0.68. The interaction between DPNUCNPs and Se NPs involves energy transfer and chirality transfer, along with the formation of spin‐polarized excitons, thereby resulting in CPL activity. Furthermore, the chiral Se/DPNUCNPs films were patterned for anti‐counterfeit and encryption applications. Our study provides a novel guide for fabricating chiral nanomaterials with strong CPL response.