Halide Ion-Modulated Chiral Synergy in Co-Assembled AIEgen-CNC Composites for Circularly Polarized Luminescence

Abstract

Pursuing innovative modulation strategies and high asymmetry factors (g_lum) remains a cornerstone in developing circularly polarized luminescence (CPL) materials. Conventional approaches employ either bottom-up chiral small molecule self-assembly or top-down co-assembly of achiral luminophores with supramolecular chiral templates (e.g., cellulose nanocrystals (CNCs), liquid crystals). These templates act as pre-engineered “molds” to align achiral emitters within chiral matrices. However, co-assembling chiral small molecules with such templates remains underexplored, challenged by complex protocols and limited assembly control, raising fundamental questions about supramolecular chiral interplay. Herein, we elucidate the co-assembly and interplay between chiral aggregation-induced emission (AIE) molecules (PN-Phe halides) and CNCs. Halide ions (F^–, Cl^–, Br^–, and PF₆^–) profoundly modulate PN-Phe self-assembly, dictating distinct morphologies, packing, chiroptical signals, fluorescent quantum yields (QY), and lifetimes. PN-Phe-Cl^– exhibits the highest g_lum (−4.1 × 10⁻³), versus PN-Phe-Br^– (−2.8 × 10⁻³). Strikingly, co-assembly into CNC-PVA-PN-Phe-X- (CPP-X-) composite films reverse this trend: CPP-Cl^– achieves an exceptional g_lum of −0.43, contrasting sharply with CPP-Cl^– (−3.1 × 10⁻²). The multiple color variations and potential application in anti-counterfeiting demonstrate the advantages of this co-assembly strategy. This work highlights the significant role of assembly patterns in constructing advanced CPL materials, revealing that halide ions could serve as effective modulators for CPL.