Titanium-silicon binary oxides

With the titanium-siheon binary oxides, a unique photoluminescence spectrum can be observed at about 500 nm (for Ti Si 1 1 binary oxide), and the Ai ax position of the corresponding spectra shifts steadily toward shorter wavelength regions with decreasing titanium content, as shown in Fig. 36. Such behavior shows good agreement with the blueshift observed in the reflectance spectra of these oxides (200). As can also be seen in Fig. 36, the addition of O2 leads to an efficient quenching of the photolumincs-cencc. A steady increase was observed in the extent of the emission parts quenched by O2 at the same pressure when the silicon content of the oxides... 

I lG- 36. Photoluminescencc spectra of titanium-silicon binary oxide catalysts with different Ti/Si ratios at 77 K and the effect of the addition of O,. Excitation wavelength, 300 nm slit width for emission, 7.0 nm pressure of added O2, 13,3 Pa (a -e ) photoluminescence spectra in the absence of (a-e) [reproduced with pei mission from Anpo el al. (200)]. 

All these results indicate that, with titanium-silicon binary oxides having low titanium contents the Ti ions are enriched near the surface regions, separated from each other, and present as tetrahedral species in the Si02 carrier matrices. In such species, the radiationless transfer of photon energy absorbed by Ti02 is suppressed because of the low coordination of the ions. As a result, the formation of the (electron-hole) ion pairs, i.e., the excited state of (Ti +- 0 ) complexes, is facihtated (200, 201). 

Binding Energies o f Ti(2p n2), Si(2pi/- ), and Si(2s) and the Ratio of the Signal Intensity of Ti(2p3i2) versus Si 2pn2) in Titanium-Silicon Binary Oxide Catalyst ... 

As shown in Fig. 65, titanium-silicon binary oxides prepared by the sol-gel method exhibit a characteristic photoluminescence spectrum near 480 nm upon excitation at 280 nm. The absorption and photoluminescence spectra are attributed to the charge-transfer processes on the highly dispersed tetrahedral titanium oxide species embedded in the Si02 matrices (168, 200, 201). When the titanium content of the oxides was decreased, the intensity of the photoluminescence spectrum increased, and its peak wavelength shifted to shorter wavelengths. 

Takeuchi M., Dohshi S., Eura T. and Anpo M. (2003b), Preparation of titanium-silicon binary oxide thin film photocatalysts by an ionised clnster beam deposition method. Their photocatalytic activity and photoindnced snperhydrophUicity , J. Phys. Chem. B 107, 14278-14282. 

Anpo, M., Nakaya, H., Kodama, S., Kubokawa, Y., Domen, K., and Onishi, T. Photocatalysis over binary metal-oxides Enhancement of the photocatalytic activity of Ti02 in titanium-silicon oxides. J. Phys. Chem. 1986, 90,1633. 

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