Abstract

In this work, TiO2 and ZnO nanoparticles of different sizes and crystallographic configuration were used to protect wood surfaces against UV radiation. The sizes and levels of photoactivity of the nanoparticles were measured in vitro by transmittance electron microscopy and electron paramagnetic resonance spectroscopy, and then they were impregnated into radiata pine samples. The production of aromatic radicals, absorbance of UV and visible light, and chemical and color changes of treated and untreated wood surfaces were assessed after UV irradiation. Results show that nanoparticles that were less photoactive were better at reducing the production of organic radicals and the chemical and color changes on wood surfaces subjected to UV. Similarly, smaller nanoparticles (40 nm) were better at reducing photochemical reactions than larger (100 nm) nanoparticles. In terms of the crystallographic configuration of nanoparticles, differences in the production of phenoxy radicals were verified only for short-term exposure. Previous research revealed that certain levels of photoactivity in TiO2 nanoparticles may contribute to decreases in the photodegradation of wood surfaces possibly by an electron sink mechanism. Our observations indicate that this is unlikely to occur in the presence of highly photoactive nanoparticles.