Hydrothermal synthesis of rutile TiO2 nanorods and their decoration with CeO2 nanoparticles as low-photocatalytic active ingredients in UV filtering applications

Abstract

The use of TiO2 nanoparticles in sunscreen products has raised concern over their oxidative potential and adverse health effects brought about by their propensity to produce free radicals when exposed to UV radiation. In this study, an investigation into industry-scalable methods for synthesizing rutile TiO2 nanorods with controllable morphological characteristics was carried out. The effects of hydrothermal reaction temperature and nitric acid concentration on the crystal phase, composition and morphology were explored to assess the most suitable conditions for reproduction. Optimal reaction conditions for obtaining purely rutile TiO2 nanorods occurred when treating the titania precursor at 150 °C for 24 h with 16 M nitric acid. Here, these rutile nanorods are decorated with CeO2 nanoparticles, as a means of producing a material with high UV attenuation and low photocatalytic activity. The nanocomposite materials are prepared using facile hydrothermal and precipitation methods and showed selective UV absorption whilst also demonstrating a reduction in photocatalytic activity compared to bare rutile TiO2 nanorods of up to 88% and 77% when exposed to UV and solar simulated light. The results suggest CeO2/TiO2 could be safely applied as an ‘active’ inorganic UV absorber in sunscreen products.