Silica matrix encapsulation as a strategy to control ROS production while preserving photoreactivity in nano-TiO2

Abstract

In this work, the application of a silica coating on TiO₂ nanoparticles (NPs) represented a material design strategy for the purpose of controlling the reactive oxygen species (ROS) production, identified as one of the potentially hazardous effects for this class of materials. The study focused on characterizing redox reactivity as a source of potential adverse cellular oxidative stress and desirable photocatalytic reactivity. The SiO₂-modified TiO₂ systems were produced using a colloidal heterocoagulation method expected to give rise to “matrix encapsulation” and the formation of a mixed structure. To assess the effect of SiO₂ surface engineering on TiO₂ NP redox reactivity, ROS production was measured by electron paramagnetic resonance (EPR) and photocatalytic tests based on NO_x/NO abatement analysis were carried out. The obtained reduction in ROS production associated with an improved photoactivity in the SiO₂-modified samples, in comparison with the TiO₂ pristine ones, encouraged the promotion of silica coating as “safer by molecular design” strategy.