Tungsten oxide sol, containing highly crystalline nanoparticles of orthorhombic WO₃ and having good sedimentation stability, was synthesized using a facile, ultrasonic-assisted technique. An additional steric stabilizer, dextran, was proposed to enhance the stability of WO₃ nanoparticles in biological media and to reduce their in vivo toxicity. The cytotoxicity of dextran-stabilized and nonstabilized WO₃ sols was studied in vitro using dental pulp stem (DPS) cell lines and breast cancer (MCF-7) cell lines. Both tungsten oxide sols demonstrated low cytotoxicity and low genotoxicity for both stem cells and malignant cells and only slightly reduced their metabolic activity in the concentration range studied (from 0.2 to 200 μg/ml). The data obtained support possible theranostic applications of tungsten oxide colloidal solutions.

Although water contamination with drug residues is a threat to public health, there are currently barely any effective methods of purifying water from pharmaceutical substances. In this study, continuous-flow sonoplasma treatment was used for the complete degradation of tetracycline and ciprofloxacin in polluted municipal water. The addition of CeO₂ nanoparticles as catalysts significantly increased the degradation rate of the antibiotics, and a degradation degree of 70% was achieved. The presence of reactive oxygen species in the CeO₂-nanoparticle-containing sonoplasma-treated system was experimentally proven for the first time using the chemiluminescence technique.

Tungsten oxide-based bulk and nanocrystalline materials are widely used as photocatalytic and photo- and electrochromic materials, as well as materials for biomedical applications. In our work, we focused our attention on the effect of sodium cations on the structure and photochromic properties of the WO₃@PVP aqueous sols. To establish the effect, the sols were synthesized by either simple pH adjusting of sodium or ammonium tungstates’ solutions, or using an ion exchange technique to remove the cations from the materials to the greatest possible extent. We showed that the presence of sodium cations in WO₃@PVP favors the formation of reduced tungsten species (W⁺⁵) upon UV irradiation of the materials, strongly affecting their photochromic and photocatalytic properties. The pronounced photoreductive properties of WO₃@PVP sols in photocatalytic reactions were demonstrated. Due to photoreductive properties, photochromic sols of tungsten oxide can act as effective photoprotectors in photooxidation processes. We believe that our work provides a considerable contribution to the elucidation of photochromic and redox phenomena in WO₃-based materials.