Background: The interest in ultraviolet (UV) radiation from the sun and artificial sources has been recently increasing due to its toxic effects, including sunburn, erythema, photodamage, and photocarcinogenesis. In this study, we aimed to develop a valuable nanomaterial that can block total UV rays using an undervalued, yet profitable marine organism. We successfully developed carbon nanodots (CNDs) and a CNDs-polyvinyl alcohol (PVA) composite film that effectively protect against UV-A, UV-B, and UV-C radiation based on a common brown algae, sea cauliflower (Leathesia difformis), through simple hydrothermal synthesis in aqueous solution.

Results: CNDs-PVA film protected rhodamine B from photobleaching and polydiacetylene vesicles with 10,12-tricosadiynoic acid from polymerization. As-fabricated CNDs in aqueous solution blocked >99% of UV-A light, which causes photoaging and skin cancer. The CNDs-PVA film showed excellent transparency, with >84% transmittance of visible light, and effectively blocked >60% of UV-A/B and >30% of UV-C rays under direct and strong irradiation.

Conclusions: This preliminary work indicates that CNDs based on underutilized marine brown algae have strong potential for application in technologies for wide UV protection.