Highly Efficient UV Protection of the Biomaterial Wood by A Transparent TiO2/Ce Xerogel

Titanium dioxide is widely used in sunscreens because of its strong ultraviolet (UV) light absorbing capabilities and its resistance to discoloration under UV exposure. However, when deposited as a thin film, the high refractive index of titanium dioxide typically results in whiteness and opacity, which limits the use of titanium dioxide for material surfaces, for which long-term natural appearance is of high relevance. Since the whitish appearance is due to the strong light scattering and reflection on the interface of oxide particles and air, one can increase the transparency of TiO2 coatings by forming a continuous TiO2 layer. The purpose of the present article is 2-fold. First, we show that, in the presence of cerium ammonium nitrate, titanium dioxide can be turned from a white powder into a TiO2/Ce xerogel via a facile bottom-up fabrication process. Second, we demonstrate that the transparent TiO2/Ce xerogel can diminish surface deterioration induced by UV light and preserve the natural appearance of the highly abundant biomaterial wood. Furthermore, EPR spectroscopy revealed that the TiO2/Ce xerogel coating suppresses free radical generation on wood surfaces upon UV irradiation. Our research expands the applicability of the protective effect of titanium dioxide to coatings for natural engineering materials, which will become increasingly important in future bioeconomies.