Towards the development of safer by design TiO2-based photocatalytic paint: impacts and performances

Addition of titanium dioxide (TiO2) (nano)particles into photocatalytic paints represents a promising alternative aiming to mineralize gaseous pollutants, such as volatile organic compounds (VOCs) into innocuous species (H2O and CO2). Despite important industrial and economic benefits, some concerns were raised regarding the risks associated with nano-objects and their human and environmental impacts. To mitigate potential risks associated with the use of these nano-objects, we report a safer by design strategy to develop a photocatalytic paint containing TiO2 nanoparticles (NPs) taking into consideration the safety aspects over its life cycle. Specific innovative types of TiO2 NPs were synthesized. These nanoparticles were then incorporated into an organic matrix-based paint. These paints were applied on standard substrates and underwent artificial weathering in an accelerated weathering chamber with controlled parameters. Photocatalytic efficiency towards airborne VOCs was measured for all the paints. Mechanical solicitation through abrasion and incineration tests were performed to assess the potential emission of airborne particles that could lead to human or environmental exposure. In parallel, toxicology studies were conducted to assess the hazards associated with the pristine particles and paint residues. Using this safer by design strategy, we succeeded in decreasing the negative impact of TiO2 on the paint matrix while keeping a good photocatalytic efficiency and reducing the NP release. Taken together, these results show that we succeeded in generating safer by design paints, thanks to the use of these specifically developed TiO2 NPs, which exhibit similar photocatalytic properties and enhanced physical properties as compared to paints containing the reference TiO2 NPs, while reducing their potential hazards.