RESUMO
The physicochemical properties of crystalline titanium dioxide nanoparticles (TiO2 NPs) were investigated by comparing amorphous (amTiO2 ), anatase (aTiO2 ), metaphase of anatase-rutile (arTiO2 ), and rutile (rTiO2 ) NPs, which were prepared at various calcination temperatures (100℃, 400℃, 600℃, and 900℃). X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed that the phase-transformed TiO2 had the characteristic features of crystallinity and average size. The surface chemical properties of the crystalline phases were different in the spectral analysis. As anatase transformed to the rutile phase, the band of the hydroxyl group at 3,600–3,100 cm –1decreased gradually, as assessed using Fourier transform infrared spectroscopy (FT-IR). For ultraviolet-visible (UVVis) spectra, the maximum absorbance of anatase TiO2 NPs at 309 nm was blue-shifted to 290 nm at the rutile phase with reduced absorbance. Under the electric field of capillary electrophoresis (CE), TiO2 NPs in anatase migrated and detected as a broaden peak, whereas the rutile NPs did not. In addition, anatase showed the highest photocatalytic activity in an UV-irradiated dye degradation assay in the following order: aTiO2 > arTiO2 > rTiO2 . Overall, the phases of TiO2 NPs showed characteristic physicochemical properties regarding size, surface chemical properties, UV absorbance, CE migration, and photocatalytic activity.
RESUMO
The physicochemical properties of crystalline titanium dioxide nanoparticles (TiO2 NPs) were investigated by comparing amorphous (amTiO2 ), anatase (aTiO2 ), metaphase of anatase-rutile (arTiO2 ), and rutile (rTiO2 ) NPs, which were prepared at various calcination temperatures (100℃, 400℃, 600℃, and 900℃). X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed that the phase-transformed TiO2 had the characteristic features of crystallinity and average size. The surface chemical properties of the crystalline phases were different in the spectral analysis. As anatase transformed to the rutile phase, the band of the hydroxyl group at 3,600–3,100 cm –1decreased gradually, as assessed using Fourier transform infrared spectroscopy (FT-IR). For ultraviolet-visible (UVVis) spectra, the maximum absorbance of anatase TiO2 NPs at 309 nm was blue-shifted to 290 nm at the rutile phase with reduced absorbance. Under the electric field of capillary electrophoresis (CE), TiO2 NPs in anatase migrated and detected as a broaden peak, whereas the rutile NPs did not. In addition, anatase showed the highest photocatalytic activity in an UV-irradiated dye degradation assay in the following order: aTiO2 > arTiO2 > rTiO2 . Overall, the phases of TiO2 NPs showed characteristic physicochemical properties regarding size, surface chemical properties, UV absorbance, CE migration, and photocatalytic activity.
RESUMO
In the present study, rutile phase titanium dioxide nanoparticles (R-TiO₂ NPs) were prepared by hydrolysis of titanium tetrachloride in an aqueous solution followed by calcination at 900℃. The composition of R-TiO₂ NPs was determined by the analysis of X-ray diffraction data, and the characteristic features of R-TiO₂ NPs such as the surface functional group, particle size, shape, surface topography, and morphological behavior were analyzed by Fourier-transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, transmission electron microscopy, dynamic light scattering, and zeta potential measurements. The average size of the prepared R-TiO₂ NPs was 76 nm, the surface area was 19 m²/g, zeta potential was −20.8 mV, and average hydrodynamic diameter in dimethyl sulfoxide (DMSO)–H₂O solution was 550 nm. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and morphological observations revealed that R-TiO₂ NPs were cytocompatible with oral cancer cells, with no inhibition of cell growth and proliferation. This suggests the efficacy of R-TiO₂ NPs for the aesthetic white pigmentation of teeth.