Tailored Cationic Visible‐Light‐Active Interfaces for Sustainable, Biodegradable Nanofibers With Dual‐Mode Antimicrobial Activity and Robust Electrostatic Particle Capture

The accumulation of microplastics originating from single-use personal protective equipment presents a growing environmental concern. Developing biodegradable fibrous alternatives is essential, but integrating robust antimicrobial efficacy with stable electrostatic capture while maintaining degradability remains a critical challenge. Here, we report a surface co-functionalization strategy addressing these challenges through covalent immobilization of sodium copper chlorophyllin (SCC) and quaternary ammonium compounds (QAC). Beyond simple dual functionalization, this molecular design induces intramolecular charge separation, suppressing electron-hole recombination in SCC and thereby amplifying reactive oxygen species generation under visible light. Simultaneously, QAC introduce permanent cationic surface charges that enable contact-mediated microbial inactivation and humidity-resistant electrostatic particle capture. Demonstrated on biodegradable silk nanofibers as a model substrate, the functionalized fibers exhibit potent antibacterial and antiviral activity under both dark and illuminated conditions, together with high nanoparticle capture efficiency. Importantly, the fibers retain intrinsic biodegradability, undergoing near-complete degradation under enzymatic conditions and substantial decomposition in soil environments. This work establishes a versatile surface functionalization platform applicable to diverse fibrous substrates, offering a sustainable alternative to conventional microplastic-generating protective materials.