Coordination-induced electronic reconstruction of natural polyphenols enables catalytic photodynamic antimicrobial amplification

Coordination with Cu 2+ induces electronic reconstruction in natural polyphenols, enabling bandgap narrowing and visible-light responsiveness. • Electronic reconstruction promotes intersystem crossing and dual-pathway ROS generation via Type I/Type II photodynamic processes. • The CuL NPs exhibit enhanced photodynamic antibacterial activity and efficient biofilm eradication under visible-light irradiation. • CuL NPs embedded in gelatin/κ-carrageenan films provide interfacial photodynamic antimicrobial protection for fruit preservation. Electronic reconstruction provides an effective route for regulating excited-state dynamics in photodynamic systems but remains difficult to achieve in bio-derived photosensitizers. Here, we reveal an electronic reconstruction effect in natural polyphenols via copper-ion-mediated coordination assembly, enabling catalytically amplified photodynamic antimicrobial activity. Electronic reconstruction enhances spin-orbit coupling and facilitates intersystem crossing (ISC) by lowering the singlet-triplet transition barrier, thereby boosting ROS generation. Spectroscopic characterization and density functional theory (DFT) calculations verify pronounced electronic modulation after coordination, including bandgap narrowing from 2.64 to 1.08 eV and reduction of the HOMO-LUMO gap from 6.22 to 5.09 eV. Coupled with a Cu(I)/Cu(II) photoredox cycle enabling catalytic ROS amplification through synergistic Type I and Type II pathways, the system achieves 99% bacterial inactivation within 20 min and eradicates mature biofilms. When incorporated into a biodegradable gelatin/κ-carrageenan matrix, these nanocomplexes form light-triggered antimicrobial films for fruit preservation. These results highlight coordination-induced electronic reconstruction as a strategy to enhance photodynamic activity in polyphenol-based materials with potential for sustainable bio-derived phototherapeutic and food-preservation platforms. Scheme 1. Conceptual illustration of coordination-driven electronic reconstruction in CuL NPs, their catalytic dual-pathway photodynamic antibacterial/antibiofilm mechanism, and translation into multifunctional GC-CuL composite films for light-responsive fruit preservation. Download: Download high-res image (158KB) Download: Download full-size image