Solution‐Processable Cross‐Linked Liquid Crystal Nanoparticles Enable Security Inks for Programmable Luminescence Lifetime and Color Coding

Room‐temperature phosphorescence (RTP) has attracted significant attention in anti‐counterfeiting, information encryption, and bioimaging. Rigid confinement is the general approach for achieving purely organic RTP, but it encounters the inherent challenge of balancing effective triplet‐state confinement with the required material flexibility and processability for advanced device integration, as well as the lack of on‐demand regulation of phosphorescence. Herein, solution‐processable, cross‐linked liquid crystal nanoparticles (LCNPs) featuring programmable phosphorescent lifetime are developed as a universal strategy for RTP activation. TPB‐doped LCNPs achieve efficient green RTP with a lifetime of up to 642.51 ms, and their afterglow duration can be precisely controlled by adjusting the LC network crosslinking density. In addition, the order and anisotropy of the LC network endow the fluorescent dye ND‐PTCDI with different aggregate behaviors, enabling a switchable emission color from green to red. Such LCNPs featuring excellent aqueous dispersibility and lifetime‐ and color‐resolved optical outputs can serve as security inks for multi‐level information encryption.