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 (g) 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-NH 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 |g| 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.