Synergistic photocatalytic stabilization: Biohybrid lignin-ZnO nanocomposites for enhanced UV protection of octocrylene and avobenzone systems

In sustainable materials engineering, designing rational and ecologically compatible ultraviolet (UV) protective materials to improve the efficiency of light protection is a major challenge. Sodium lignosulfonate (SL), a renewable biomass derivative possessing inherent UV-blocking and antioxidant properties, has been utilized as a foundational component in this research. Through one-pot synthesis approach, a light-colored sodium lignosulfonate zinc oxide composite (ZnO@SL) was successfully fabricated. The effective incorporation of ZnO within the SL matrix through systematic experimental characterization, while the preservation of the hexagonal wurtzite crystalline structure was concurrently preserved. Superior broadband UV attenuation is observed in the nanocomposite compared to pristine ZnO and SL through UV–visible spectroscopy and in vitro SPF evaluation. Through the complementary mechanisms combining physical scattering and chemical absorption, the excellent photoprotection enhancement is achieved, particularly when integrated with chemical sunscreens octocrylene (Oct) and avobenzone (Avo). The SPF value increases from 8.9 to 98.41 at a 2 wt% composite loading. The preserved π-conjugated system and oxygen-rich functional groups in SL are identified to facilitates charge transfer interactions with organic UV filters. This innovative engineering strategy establishes ZnO@SL as a dual-functional additive for the development of high-performance bio-based photoprotective formulations, offering enhanced light protection while reduced environmental impact.