Structural Characterization of Titanium-Silica Oxide Using Synchrotron Radiation X-ray Absorption Spectroscopy.

In this study, titania-silica oxides (Ti x Si y oxides) were successfully prepared via the sol-gel technique. The Ti and Si precursors were titanium (IV), isopropoxide (TTIP), and tetraethylorthosilicate (TEOS), respectively. In this work, the effects of pH and the Ti/Si atomic ratio of titanium-silicon binary oxide (Ti x Si y ) on the structural characteristics of Ti x Si y oxide are reported. 29 Si solid-state NMR and FTIR were used to validate the chemical structure of Ti x Si y oxide. The structural characteristics of Ti x Si y oxide were investigated using X-ray diffraction, XRF, Fe-SEM, diffraction particle size analysis, and nitrogen adsorption measurements. By applying X-ray absorption spectroscopy (XAS) obtained from synchrotron light sources, the qualitative characterization of the Ti-O-Si and Ti-O-Ti bonds in Ti-Si oxides was proposed. Some Si atoms in the SiO 2 network were replaced by Ti atoms, suggesting that Si-O-Ti bonds were formed as a result of the synthesis accomplished using the sol-gel technique described in this article. Upon increasing the pH to alkaline conditions (pH 9.0 and 10.0), the nanoparticles acquired a more spherical shape, and their size distribution became more uniform, resulting in an acceptable nanostructure. Ti x Si y oxide nanoparticles were largely spherical in shape, and agglomeration was minimized. However, the Ti 50 Si 50 oxide particles at pH 10.0 become nano-sized and agglomerated. The presence of a significant pre-edge feature in the spectra of Ti 50 Si 50 oxide samples implied that a higher fraction of Ti atoms occupied tetrahedral symmetry locations, as predicted in samples where Ti directly substituted Si. The proportion of Ti atoms in a tetrahedral environment agreed with the value of 1.83 given for the Ti-O bond distance in Ti x Si y oxides produced at pH 9.0 using extended X-ray absorption fine structure (EXAFS) analysis. Photocatalysis was improved by adding 3% wt TiO 2 , SiO 2 , and Ti x Si y oxide to the PLA film matrix. TiO 2 was more effective than Ti 50 Si 50 pH 9.0, Ti 50 Si 50 pH 10.0, Ti 50 Si 50 pH 8.0, and SiO 2 in degrading methylene blue (MB). The most effective method to degrade MB was TiO 2 > Ti 70 Si 30 > Ti 50 Si 50 > Ti 40 Si 60 > SiO 2 . Under these conditions, PLA/Ti 70 Si 30 improved the effectiveness of the photocatalytic activity of PLA.