Doped TiO2 and oligoalkylhydrosiloxane-based surface modifiers with self-cleaning and hydrophobic properties

The development of self-cleaning coatings for building materials is a pressing task, addressing both the protection of construction surfaces from atmospheric degradation and the removal of airborne pollutants. Titanium dioxide (TiO₂), a well-known photocatalyst active in the UV and visible regions of the electromagnetic spectrum, is widely used for this purpose. However, the direct application and stable fixation of TiO₂ on finished building materials remains challenging. In this work, film-forming compositions were developed based on aqueous emulsions of oligomethylhydrosiloxane combined with doped TiO₂. Upon application and drying, these formulations simultaneously impart hydrophobic and self-cleaning properties to materials such as wood, red clay brick, aerated concrete blocks, and fireclay bricks. TiO₂ was synthesized via hydrolysis of TiCl₄ in an ultrasonic field, followed by heat treatment. The optimal calcination temperature was determined to be 450 °C. To extend photocatalytic activity into the visible spectrum, the material was doped with Hf(IV), Zr(IV), Ce(III), and Dy(III). The synthesized powders were characterized using IR spectroscopy, laser diffraction, scanning electron microscopy (SEM), adsorption analysis, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and differential thermal–gravimetric analysis (DTGA). Photocatalytic performance was evaluated through the degradation of the organic dye rhodamine 6 G under visible light. The highest activity was achieved within 240–300 min, with a degradation efficiency of 99.9 %. Film-forming compositions containing both the hydrophobic agent (oligomethylhydrosiloxane) and the photocatalyst (TiO₂) were then applied to various substrates. Treated surfaces exhibited superhydrophobicity, with water contact angles of 140–145°. Self-cleaning efficiency was assessed on treated samples exposed to natural sunlight and under controlled laboratory conditions. Maximum color reduction of rhodamine 6 G stains was achieved within 96–120 h. Water absorption tests revealed a significant improvement in moisture resistance: treated samples gained only 4–15 % weight after 1 h of immersion, compared to 56–60 % for untreated controls. This approach provides an efficient and cost-effective method for immobilizing TiO₂ on finished building surfaces, endowing them with durable superhydrophobic and self-cleaning properties. • Titanium dioxide nanoparticles doped with d- and f-elements compounds were obtained. • A film-forming solutions based on doped TiO 2 and oligomethylhydridsiloxane water emulsion were developed. • Self-cleaning and hydrophobic coatings for building materials surface was invented. • Coatings demonstrated high photocatalytic activity for organic pollutants decomposition.