Titanium dioxide incorporated in cellulose nanofibers with enhanced UV blocking performance by eliminating ROS generation

Abstract

The preparation of sunblocks with dispersion stability, ultraviolet blocking, and photocompatibility remains a considerable challenge. Plant-derived natural polymers, such as cellulose nanofibers (CNF), show versatile traits, including long aspect ratio, hydrophilic nature, resource abundance, and low material cost. In the present study, a facile and cost-effective strategy is reported for the fabrication of nanostructured inorganic materials by incorporating natural polymers as interspersed, systematically nanosized titanium dioxide (TiO₂) particles onto CNF. Among all experiments, the optimized TiO₂@CNF3 showed higher ultraviolet blocking performance and less whitening effect. The outstanding performance is attributed to the engineering of equally dispersed nano-sized TiO₂ particles on the CNF surface and stable dispersion. Significantly, TiO₂@CNF3 exhibited excellent compatibility with avobenzone (80%), an oil-soluble ingredient used in sunblock products, illustrating the photoprotection enhancement under ultraviolet A (UVA) and ultraviolet B (UVB). Moreover, only 14.8% rhodamine B (Rho-B) dye degraded through photocatalytic oxidation process with the TiO₂@CNF3, which is negligible photocatalytic activity compared to that of TiO₂ (95% dye degraded). Furthermore, commercial inorganic and organic sunblock products with SPF lifetimes of 35⁺ and 50⁺ were modified using CNF, significantly enhancing the transmittance performance compared to that of the pure sunblock. However, it was also observed that hydrophilic CNF tended to demulsify the creams due to electrostatic disequilibrium. This CNF-based modified TiO₂ system is a new window to replace effective sunblock products in high-value-added applications, such as cosmetics.