Surface phases of TiO2 nanoparticles (30 ∼ 200 nm) were studied by UV Raman spectroscopy and FT-IR spectroscopy with CO and CO2 as probe molecules. UV Raman spectroscopy can differentiate the surface phase structure of TiO2 calcined at different temperatures. IR spectra of adsorbed CO and CO2 on TiO2 calcined at different temperatures are in good agreement with the results from UV Raman spectra. IR results evidently confirm that UV Raman spectroscopy is a surface-sensitive technique for TiO2. Both UV Raman and IR spectra indicate that the crystalline phase of TiO2 in the surface region is usually different from that in the bulk which is characterized by XRD. CO is weakly adsorbed on Ti4+ ions of anatase phase but is hardly adsorbed on those of rutile phase at room temperature. Adsorbed CO2 on anatase phase produces mainly bidentate carbonate, while on rutile phase produces mainly bicarbonate species. These results suggest that the surface Lewis acidity of anatase phase is stronger than that of rutile phase, and the concentration of cus Ti4+-O2- pairs on the surface of anatase phase is much higher than that on rutile phase; however, the basicity of surface OH groups of rutile phase is stronger than that of anatase phase.

Ti-substituted mesoporous SBA-15 (Ti-SBA-15) materials have been synthesized by using a new approach in which the hydrolysis of the silicon precursor (tetramethoxysilane, TMOS) is accelerated by fluoride. These materials were characterized by powder X-ray diffraction patterns (XRD), X-ray fluorescence spectroscopy (XRF), N 2 sorption isotherms, diffusereflectance UV-visible (UV-vis) and UV-Raman spectroscopy, 29 Si MAS NMR, and the catalytic epoxidation reaction of styrene. Experiments show that Ti-SBA-15 samples of high quality can be obtained under the following conditions: F/Si g 0.03 (molar ratio), pH e 1.0, aging temperature e 80°C, and Ti/Si e 0.01. It was found that the hydrolysis rate of TMOS was remarkably accelerated by fluoride, which was suggested to play the main role in the formation of Ti-SBA-15 materials of high quality. There is no stoichiometric incorporation of Ti, and the Ti contents that are obtained are quite low in the case of the approach that is proposed. The calcined Ti-SBA-15 materials show highly catalytic activity in the epoxidation of styrene.

The phase transformation of zirconia from tetragonal to monoclinic is characterized by UV Raman spectroscopy, visible Raman spectroscopy, and XRD. Electronic absorption of ZrO 2 in the UV region makes UV Raman spectroscopy more sensitive at the surface region than XRD or visible Raman spectroscopy. Zirconia changes from the tetragonal phase to the monoclinic phase with calcination temperatures elevated and monoclinic phase is always detected first by UV Raman spectroscopy for the samples calcined at lower temperatures than that by XRD and visible Raman spectroscopy. When the phase of zirconia changes from tetragonal to monoclinic, the slight changes of the phase at very beginning can be detected by UV Raman spectroscopy. UV Raman spectra clearly indicate that the phase transition takes place initially at the surface regions. It is found that the phase change from tetragonal to monoclinic is significantly retarded when amorphous Zr(OH) 4 was agglomerated to bigger particles and the particle agglomeration of amorphous zirconium hydroxide is beneficial to the stabilization of t-ZrO 2 phase.

The anaerobic photocatalytic reaction of methanol on Pt/TiO 2 catalyst was studied by in situ Fourier transform IR and time-resolved IR spectroscopy. For the Pt/TiO 2 catalysts reduced at high temperature, the capacity of methanol adsorption decreases with the increase of the Pt loading, indicating that Pt particles or atoms occupy some of the active sites on TiO 2 for methanol adsorption. Surface species CH 2 O(a), CH 2 OO(a), and HCOO(a) are derived from the photocatalytic reaction of methanol on Pt/TiO 2 . The increase of gas-phase methanol or water accelerates the photoreaction and improves the activity of H 2 production. When the catalysts are exposed to methanol, the strong electronic absorption on nanosecond to second time scale is observed, indicating that a great amount of long-lived electrons are produced in TiO 2 -based photocatalysts after band gap excitation. The decay rate of the long-lived electrons correlates well with the activity of H 2 production. These results show that the long-lived electrons contribute to the H 2 generation and the decays of the long-lived electrons on millisecond to second time scale in Pt/TiO 2 are ascribed to the reaction for H 2 evolution: e tr -[Pt] + H + fH‚f1/2H 2 . The function of the molecularly adsorbed methanol or water is found to mediate the proton transfer on the TiO 2 surface. The activities of H 2 production under steady-state irradiation conditions were also measured, and it is deduced that the yield of the long-lived electrons could be responsible for the activity of H 2 production.

A [(C(18)H(37))(2)N(+)(CH(3))(2)](3)[PW(12)O(40)] catalyst, assembled in an emulsion in diesel, can selectively oxidize the sulfur-containing molecules present in diesel into their corresponding sulfones by using H(2)O(2) as the oxidant under mild conditions. The sulfones can be readily separated from the diesel using an extractant, and the sulfur level of the desulfurized diesel can be lowered from about 500 ppm to 0.1 ppm without changing the properties of the diesel. The catalyst demonstrates high performance (>/=96 % efficiency of H(2)O(2), is easily recycled, and approximately 100 % selectivity to sulfones). Metastable emulsion droplets (water in oil) act like a homogeneous catalyst and are formed when the catalyst (as the surfactant) and H(2)O(2) (30 %) are mixed in the diesel. However, the catalyst can be separated from the diesel after demulsification.

Framework titanium in Ti-silicalite-1 (TS-1) zeolite was selectively identified by its resonance Raman bands using ultraviolet (UV) Raman spectroscopy. Raman spectra of the TS-1 and silicalite-1 zeolites were obtained and compared using continuous wave laser lines at 244, 325, and 488 nm as the excitation sources. It was only with the excitation at 244 nm that resonance enhanced Raman bands at 490, 530, and 1125 cm -1 appeared exclusively for the TS-1 zeolite. Furthermore, these bands increased in intensity with the crystallization time of the TS-1 zeolite. The Raman bands at 490, 530, and 1125 cm -1 are identified as the framework titanium species because they only appeared when the laser excites the charge-transfer transition of the framework titanium species in the TS-1. No resonance Raman enhancement was detected for the bands of silicalite-1 zeolite and for the band at 960 cm -1 of TS-1 with any of the excitation sources ranging from the visible to UV regions. This approach can be applicable for the identification of other transition metal ions substituted in the framework of a zeolite or any other molecular sieve.

Using microporous zeolites as host, sub-nanometric ZnO clusters were prepared in the micropores of the host by the incipient wetness impregnation method. A small amount of sub-nanometric ZnO clusters were introduced into the channels of HZSM-5 zeolite, whereas a large quantity of sub-nanometric ZnO clusters can be accommodated in the supercages of HY zeolite and no macrocrystalline ZnO exists on the extra surface of the HY material. The vibrations of the zeolite framework and ZnO were characterized by UV Raman spectroscopy. The optical properties of these ZnO clusters were studied by UV-visible absorption spectroscopy and laser-induced luminescence spectroscopy. It is found that there are strong host-guest interactions between the framework oxygen atoms of zeolite and ZnO clusters influencing the motions of the framework oxygen atoms. The interaction may be the reason why ZnO clusters are stabilized in the pores of zeolites. Different from bulk ZnO materials, these sub-nanometric ZnO clusters exhibit their absorption onset below 265 nm and show a purple luminescence band (centered at 410-445 nm) that possesses high quantum efficiency and quantum size effect. This purple luminescence band most likely originates from the coordinatively unsaturated Zn sites in sub-nanometric ZnO clusters. On the other hand, the differences in the pore structure between HZSM-5 and HY zeolites cause the absorption edge and the purple luminescence band of ZnO clusters in ZnO/HZSM-5 show a red shift in comparison with those of ZnO clusters in ZnO/HY.

Nanostructured β-Mo 2 C on an ultrahigh surface area carbon material (>3000 m 2 /g), a kind of novel carbon material with uniform pore distribution, was prepared by the carbothermal hydrogen reduction method. The Mo precursor and Mo 2 C have been characterized by X-ray diffraction, nitrogen adsorption, high-resolution transmission electron microscope, and temperature-programmed reduction mass spectroscopy. The data show that nanostructured β-Mo 2 C can be formed on the ultrahigh surface area carbon materials by carbothermal hydrogen reduction at ∼700 °C. The particle sizes of β-Mo 2 C increase with the increase of reaction temperatures. The carbothermal hydrogen reduction includes two successive steps: reduction of the MoO 3 precursor by hydrogen and reaction between partially reduced molybdenum oxides and surface carbon atoms of carbon materials under the hydrogen atmosphere.