UV-Absorption and Silica/Titania Colloids Using a Core–Shell Approach

Abstract

Metal-oxo-colloids have been prepared using tetraethoxysilane (TEOS) oligomers with titanium tetra-ipropoxide (TIP) or titanium (di-i-propoxide) bis(acetylacetonate) (TIA) precursors. Transmission electron microscopy (TEM), FTIR, UV-Vis, and photoluminescence spectroscopy were used to investigate the composition, the size, and optical properties of the Si/Ti core-shell colloids. The presence of hetero-bonded silicate structure (Si-O-Ti) was indicated by FTIR spectroscopy. The size of Si/TIP system ranged from 55 to 120 nm and Si/TIA system ranged from 220 to 250 nm. The TEM data indicated that the size of colloids can be controlled by the TIP or TIA content. The Si/ Ti system exhibited strong absorption in the UV-range, yet had excellent optical transmittance in the visible range. The Si/Ti systems exhibited a photoluminescence emission at 329 nm.

Preparation of Porous SiO2-TiO2-NiO Synthesized by the Sol-Gel Process and its Characterization

“…The CH 3 stretching of Si-O-CH 3 was found in the fresh sol at 1273cm -1 and disappeared after thermal treatment at 673K (not shown here), as we expected due to the combustion of the organic groups [16]. The band at 910-960cm -1 is due to the overlapping of vibrations of Si-OH, Si-O-Ti bonds [15] (932cm -1 ) [17] and Si-O-Ni (960cm -1 ) [18], this region widens as a result of heat treatment. The bands in the wave number range up 556cm -1 are attributed to the deformation vibration of Si-O groups containing SiO 4 tetrahedra [19].…”

Isomorphic Ti Substitution into SBA-15 without Ti Loss and with Lower TiO2 Segregation

“…On the other hand, TEOS was more slowly hydrolyzed so that the rate could be studied visually at different pH values (Figure S8 in the SI) and by UV–vis DRS (Figures and S9 in the SI). The intensity of the peak appearing in the range of 250–320 nm of UV–vis DRS is proportional to the concentration of the hydrolyzed TEOS . At pH 0.068, the color of the solution changes suddenly from transparent white to a pale milky color over 10 min from 1 h 30 min to 40 min after the reaction started.…”