Lignocellulose Nanofibers-Induced In-Situ Self-Assembly of Copper Nanoclusters for pH-Adaptive Fluorescent Composite Films Integrating UV Shielding with Humidity-Responsive and Preservation Functions

Lignocellulose nanofibers (LCNFs) possess unique interfacial properties, yet their ability to direct the ordered assembly of metal nanoclusters remains underexplored. Inspired by biological reinforcement, this study proposes an in-situ self-assembly strategy for copper nanoclusters (CuNCs) induced by LCNFs. Through Cu2+ coordination cross-linking, polyvinyl alcohol (PVA)-LCNFs hydrogen bonding, and glutathione ionizable groups, the high-performance composite film was constructed. It exhibits a tensile strength of 15.04 MPa (1.8 times that of the pure LCNFs films) and an approximately six-fold enhancement in fluorescence emission intensity (from 2.1% to 12.4%) relative to the pure LCNFs films. It achieves UV shielding (blocking >99% for UV-B/C) and humidity-responsive conductivity (398 μS/m at 90% RH). Its fluorescence is pH-adaptive, reversibly switching from orange-yellow to deep blue. Strawberry tests confirmed freshness retention after 48 h of UV irradiation. By fusing these multifunctional properties, this work provides design insights for sustainable, durable polymer materials with enhanced resistance to photo-oxidative degradation.