Improving the Sunscreen Properties of TiO(2) through an Understanding of Its Catalytic Properties

[Image: see text] The use of particulate titanium dioxide (TiO(2)) as an active sunscreen ingredient has raised concerns about potential risks from TiO(2)-mediated free radical formation. To date, remediation attempts have concentrated on reducing the yield of free radical generation by TiO(2) upon sunlight exposure. The problem with this approach is that given the band gap in TiO(2), production of radical and the ensuing reactive oxygen species (ROS) is completely normal. Our strategy is based on a nontoxic, biocompatible shell that neutralizes the free radicals by scavenging them with natural antioxidants before they exit the particle. The new lignin@TiO(2) composites preserve the scattering and absorption properties of TiO(2) because the particles retain their nanoscale dimensions as preferred by the cosmetic industry. Although the target properties for photocatalysis and sun-protection applications are opposite, we argue that exactly the same knowledge is required to optimize either one.