The Polymer Society of Korea

Abstract

Zinc oxide (ZnO) nanoparticles are widely used as inorganic UV filters for their excellent UV-blocking ability. However, their efficacy is limited by narrow spectral coverage and the generation of reactive oxygen species under UV exposure. Here, we present a scalable strategy to fabricate broad-spectrum UV filters via in situ formation and browning of a metal–phenolic network (MPN) on ZnO surface. The spontaneous release of Zn²⁺ from ZnO initiates complexation with tannic acid (TA), forming an MPN coating without external metal ions. The ZnO-mediated oxidation and dimerization of TA further induce a browning reaction, enhancing π–π conjugation and thereby extending the optical absorption range into the high energy visible light region. The proposed strategy enables the development of eco-friendly sunscreen agents with tunable optical and safety profiles. This research was supported by the Korea Health Industry Development Institute (KHIDI) (grant number: RS-2024-00340429) and the Korea Technology and Information Promotion Agency for SMEs (TIPA) (grant number: RS-2025-02306912).