Interfacial Modulation of Cu(I) Cluster‐CNC Photonic Films for Efficient Circularly Polarized Luminescence and Multilevel Anticounterfeiting

ABSTRACT Circularly polarized luminescent (CPL) materials based on cellulose nanocrystal (CNC) show great potential for asymmetric synthesis and information security. However, they are often brittle, while their luminescence dissymmetry factor (| g lum |) and quantum yield (Φ) are difficult to enhance simultaneously. These limitations reduce both their chiroptical performance and multidimensional information encoding capability. Herein, this work presents an interfacial modulation strategy in which poly(vinylpyrrolidone) (PVP) and Cu(I) clusters are introduced into a left‐handed cholesteric CNC matrix through vacuum‐assisted co‐assembly. This approach stabilizes the chiral photonic structure, improves the dispersion of the luminescent units, and effectively reduces film brittleness, yielding a flexible CNC/PVP/Cu(I) composite. The coupling between the photonic bandgap and Cu(I) cluster emission allows tunable right‐handed CPL with |g lum | value up to 0.93 and Φ of 42.79%. The films show reversible responses to humidity, polar solvents, and NH 3 . Moreover, a 10 × 10 pixelated design enables over 2 600 distinguishable encoding states. This material therefore provides a feasible design strategy for high‐security anti‐counterfeiting and information encryption applications.