Microbial contamination of the surface of building materials and subsequent release of microbial particles into the air can significantly affect indoor air quality. Avoiding the development or, at least, reducing the quantity of microorganisms growing on building materials is a key point to reduce health risks for building occupiers. In that context, the antimicrobial activity of TiO₂, ZnO and Au/ZnO was assessed by measuring log reductions of Escherichia coli and Aspergillus niger populations both in the dark and under a light intensity close to real-life conditions. The bactericidal activities (≥2.3 log reduction) of tested products were stronger than their fungicidal activities (≤1.4 log reduction) after 2 h of contact. Different parameters including concentration of photocatalyst, intensity of light (dark vs. 5 W/m² UV-A), and duration of contact between photocatalyst and microbial cells and spores were investigated. Results of this study confirmed bactericidal activities of TiO₂, ZnO and AuZnO on E. coli and brought new insight on their fungicidal activity on the spores of A. niger. They also confirmed the greatest antimicrobial efficiency of ZnO compared to TiO₂ and its increased photocatalytic activity when decorated with Au, leading to the highest log reductions detected after 2 h of contact for both tested microorganisms (4 and 1.4 for E. coli and A. niger, respectively). The antimicrobial activity was enhanced by the duration of contact between microorganisms and nanoparticles of the different tested photocatalytic products.

The development of advanced photocatalysts for air pollution removal is essential to improve indoor air quality. TiO₂/mesoporous silica SBA-15 nanocomposites were synthesized using an organometallic decoration method, which leverages the high reactivity of Ti precursors to be hydrolyzed on the surface water groups of silica supports. Both lab-made Ti(III) amidinate and commercial Ti(IV) amino precursors were utilized to react with water-rich SBA-15, obtained through a hydration process. The hydrated SBA-15 and the TiO₂/SBA-15 nanocomposites were characterized using TGA, FTIR, ¹H and ²⁹Si NMR, TEM, SEM, N₂ physisorption, XRD, and WAXS. This one-step TiO₂ decoration method achieved a loading of up to 51.5 wt.% of approximately 9 nm anatase particles on the SBA-15 surface. This structuring provided excellent accessibility of TiO₂ particles for photocatalytic applications under pollutant gas and UV-A light exposure. The combination with the high specific surface area of SBA-15 resulted in the efficient degradation of 400 ppb of NO pollutant gas. Due to synergistic effects, the best nanocomposite in this study demonstrated a NO abatement performance of 4.0% per used mg of TiO₂, which is 40% more efficient than the reference photocatalytic material TiO₂ P-25.