No abstract

The samples with nano-titanium dioxide (X-ray amorphous, η-modification, Degussa P25 mixture of rutile and anatase, Hombifine N, and Hombikat UV100 with anatase) and hexagonal nano-ZnO both in pure form and as a part of polystyrene (PS) nanocomposites were studied for antibacterial activity in the dark against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Bacillus antracoides, and Candida albicans microorganisms by the Kirby-Bauer disk diffusion method. Among the starting samples, ZnO exhibits ABA against all bacterial cultures in use; the sample with the η-phase exhibits ABA against Staphylococcus aureus, Staphylococcus epidermidis, and Bacillus antracoides; the X-ray amorphous TiO 2 exhibits ABA against Staphylococcus aureus and Candida albicans; and the remaining samples have no ABA. The diameters of the microbial growth retardation zone for the η-phase/PS, X-ray amorphous TiO 2 /PS, and ZnO/PS nanocomposites were found to be less than those for the starting oxides; the range of microbes inhibited by ZnO/PS was smaller since it exhibited no ABA against Candida albicans, while such activity remained in the X-ray amorphous TiO 2 /PS nanocomposite.

Nanocomposites TiO 2 /SiO 2 with photocatalytic and adsorptive properties were prepared by codispersing of η-modification and anatase (commercial Hombifine N) and SiO 2 (opal, granules, ultrafine) in ethanol (or ethanol-water mixture in the presence of chlorophylls or porphyrins) with ultrasonic treatments of the mixture (method 1) and an aqueous solution of KOH with a microwave treatment (method 2), as well as the introduction of SiO 2 in the reaction mixture during the synthesis of TiO 2 by brief hydrolysis of sulfate titanyl (method 3). It was found that the state of titania in the sample (X-ray amorphous or nanocrystalline) and its deposition on SiO 2 nanocomposites depend on the method and the conditions of obtaining. It was established that the photocatalytic activity of nanocomposite TiO 2 /SiO 2 (granules) (method 1) photosensitized by coproporphyrin I in the visible range and the photocatalytic activity of nanocomposite TiO 2 /SiO 2 (opal) (method 3) in the near UV range exceed activity of the commercial sample of TiSiO 4 by more than 20-fold and ~7-fold, respectively. It was shown that the nanocomposite TiO 2 /SiO 2 (opal) significantly reduces the concentration of cations (in particular, Be, Ni, Bi) in the model water systems.