Stabilized Titanium Dioxide Nanoparticles: Preparation and Physicochemical, Photocatalytic, and Antimicrobial Properties

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The anatase nanoparticles are stabilized with titanium tetraisopropoxide Ti[OCH(CH₃)₂]₄ and isopropyl alcohol without surfactants suitable for biological studies. We showed that the hydrodynamic radii in suspensions depend on temperature and the duration of hydrolysis, whereas the composition (a mixture of anatase with brookite, anatase, brookite, and rutile) and the sizes of crystallites (X-ray), nanoparticles, and aggregates (SEM) in the dried state are mainly dependent on the pH of the environment. The nonphase of the samples stems from coherent intergrowth of unit cells of anatase and brookite via geometric and structural complementarity. We found that photocatalytic activity (PCA; Rhodamine 6G model dye under UV radiation) depends on OH/H₂O ratio (adsorbed), whereas antimicrobial activity (AMA) in the dark depends on an amount of free water on the surface of nanoparticles according to X-ray photoelectron spectroscopy (XPS). We revealed that samples with the smallest sizes of nanoparticles of all levels possess the highest PCA and AMA relative to Staphylococcus aureus and Escherichia coli.