TiO2 is considered as one of the most efficient photocatalysts for the degradation of air and liquid indoor pollutants. However, pristine TiO2 can mainly absorb the UV fraction of solar light [1]. In addition, TiO2 nanoparticles (NPs) were recently classified as a suspected carcinogen [2]. To address these challenges, Creative Nano is currently developing waterborne paints containing sulfur doped TiO2 NPs that are photocatalytically active under visible light irradiation [3]. Moreover, the S-doped TiO2 NPs were combined with silica to produce S-TiO2/SiO2 nanocomposites, following a “safe by design” approach, because the presence of a silica layer surrounding TiO2 NPs has been shown to restrict release of NPs into the environment [4]. In this work, a series of S-doped TiO2/SiO2 samples with different SiO2 content were prepared via sol-gel synthesis. The samples were characterized by InfraRed (IR) and Diffuse Reflectance spectroscopy (DRS) in the solid-state whereby their particle size was measured by Dynamic Light Scattering (DLS) in water. The samples were evaluated versus the photocatalytic degradation of methyl orange (MO) in water under visible-light irradiation. Our results showed that the introduction of a SiO2 layer had a beneficial effect on photocatalytic activity compared to pristine S-TiO2. The highest MO degradation was observed for S-TiO2/SiO2 NPs with ~4 wt % SiO2. The best performing nanopowder was incorporated in a waterborne paint formulation. The photocatalytic properties of the paint were evaluated at lab-scale by monitoring MO degradation in solution . 45±3 % MO removal was observed after 5 h of visible light irradiation over five cycles.

{"references": ["[1] S. Banerjee et al. J. Phys. Chem. Lett. 2014, 5, 2543\u20132554; https://doi.org/10.1021/jz501030x", "[2] Commission Delegated Regulation (EU) 2020/217 of 4 October 2019", "[3] T. Kalampaliki et al., Nanomaterials, 2021, 11, 2543; https://doi.org/10.3390/nano11102543", "[4] R. Bengalli et al. Nanomaterials, 2019, 9, 1041; https://doi.org/10.3390/nano9071041"]}