Titania hollow spheres modified with tungstophosphoric acid with enhanced visible light absorption for the photodegradation of 4-chlorophenol.

Titania hollow spheres were synthesized using silica nanospheres as the template. The core was removed using NaOH solution. They were subsequently impregnated with tungstophosphoric acid (TPA) solutions and annealed at two different temperatures (100 and 500 °C). These materials were characterized by several physicochemical techniques (XRD, BET, SEM, DRS, FT-IR, FT-Raman and 31P MAS-NMR). The 31P MAS-NMR and FT-IR characterization showed that the main species present in the samples was the [PW12O40]3- anion, which was partially transformed into the [P2W21O71]6- anion during the synthesis and drying step. 31P MAS-NMR, and FT-Raman characterization revealed the evidence of a strong interaction between the Keggin anion of TPA and TiO2 surfaces, possibly due to the formation of surface heteropolyacid-TiO2 complexes. The DRS results showed that the absorption threshold onset continuously shifted to the visible region with increased TPA concentration and calcination at 500 °C. The enhanced visible light absorption could be related to the formation of a surface complex TPA Keggin anion-TiO2. The catalytic activity of the materials in the photodegradation of 4-chlorophenol under UV and visible light irradiation increased when the TPA content and the calcination temperature of the samples were raised.

A new synthesis pathway for colloidal silica spheres coated with crystalline titanium oxide and its comparative cyto- and genotoxic study with titanium oxide nanoparticles in rat osteosarcoma (UMR106) cells.

Spherical particles with an amorphous core of silica and a crystalline shell of titanium oxide (SiO(2)@TiO(2)) formed in a three-step procedure, being the last step a mild chemical treatment. SiO(2)@TiO(2) had a shell with pores (micro and mesopores) permeating between TiO(2) nanocrystals (anatase) and a solid core of amorphous silica. The spheres had an outstanding specific surface area (300 m(2) g(-1)). A cyto- and genotoxic study of SiO(2)@TiO(2) and titanium oxide nanoparticles (TiO(2)-NP) on UMR106 cells with 24h exposure showed that SiO(2)@TiO(2) colloidal particles were less toxic than TiO(2)-NP.

Comparative study of the cytotoxic and genotoxic effects of titanium oxide and aluminium oxide nanoparticles in Chinese hamster ovary (CHO-K1) cells.

The aim of this study was to analyze the cytotoxicity and genotoxicity of titanium oxide (TiO(2)) and aluminium oxide (Al(2)O(3)) nanoparticles (NPs) on Chinese hamster ovary (CHO-K1) cells using neutral red (NR), mitochondrial activity (by MTT assay), sister chromatid exchange (SCE), micronucleus (MN) formation, and cell cycle kinetics techniques. Results showed a dose-related cytotoxic effect evidenced after 24h by changes in lysosomal and mitochondrial dehydrogenase activity. Interestingly, transmission electronic microscopy (TEM) showed the formation of perinuclear vesicles in CHO-K1 cells after treatment with both NPs during 24h but no NP was detected in the nuclei. Genotoxic effects were shown by MN frequencies which significantly increased at 0.5 and 1 microg/mL TiO(2) and 0.5-10 microg/mL Al(2)O(3). SCE frequencies were higher for cells treated with 1-5 microg/mL TiO(2). The absence of metaphases evidenced cytotoxicity for higher concentrations of TiO(2). No SCE induction was achieved after treatment with 1-25 microg/mL Al(2)O(3). In conclusion, findings showed cytotoxic and genotoxic effects of TiO(2) and Al(2)O(3) NPs on CHO-K1 cells. Possible causes of controversial reports are discussed further on.