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101.
The crystal phase, morphology and facet significantly influence the catalytic and photocatalytic activity of TiO2. In view of optimizing the performance of catalysts, extensive efforts have been devoted to designing new sophisticate TiO2 structures with desired facet exposure, necessitating the understanding of chemical properties of individual surface. In this work, we have examined the photooxidation of methanol on TiO2(011)-(2×1) and TiO2(110)-(1×1) by two-photon photoemission spectroscopy (2PPE). An excited state at 2.5 eV above the Fermi level (EF) on methanol covered (011) and (110) interface has been detected. The excited state is an indicator of reduction of TiO2 interface. Irradiation dependence of the excited resonance signal during the photochemistry of methanol on TiO2(011)-(2×1) and TiO2(110)-(1×1) is ascribed to the interface reduction by producing surface hydroxyls. The reaction rate of photooxidation of methanol on TiO2(110)-(1×1) is about 11.4 times faster than that on TiO2(011)-(2×1), which is tentatively explained by the difference in the surface atomic configuration. This work not only provides a detailed characterization of the electronic structure of methanol/TiO2 interface by 2PPE, but also shows the importance of the surface structure in the photoreactivity on TiO2.  相似文献   
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硫酸钙及硫酸铵气溶胶对二次有机气溶胶生成的影响   总被引:1,自引:0,他引:1  
二次有机气溶胶(SOA)是大气光化学反应的产物, 也是城市和郊区大气中细粒子的主要成分. 本研究致力于考察高浓度无机气溶胶颗粒对SOA生成的影响. 实验系统采用2 m3的温控烟雾箱, 以干燥的CaSO4和(NH4)2SO4为无机种子气溶胶, 研究了间二甲苯/NOx/空气体系光氧化生成SOA的过程. 实验结果显示间二甲苯和NOx在紫外光照下会产生大量SOA, SOA产率可用单产物模型表征. CaSO4气溶胶的存在对SOA产率曲线没有明显的影响, 而(NH4)2SO4气溶胶的存在使气相半挥发性氧化产物的生成量增加36%, 显著地增加了SOA的产率. (NH4)2SO4粒子在含水有机物作用下显现的弱酸性可能是导致这一影响的主要原因. 该实验结果有助于更详尽地阐明中国颗粒物污染严重城市SOA的生成机理, 从而为进一步修正空气质量模型提供依据.  相似文献   
104.
Photosensitized oxidative desulfurization of thiophene in n-octane/water extraction system with riboflavin as photosensitizer and O2 in air as oxidant was studied. A 500 W high pressure Hg lamp was used as the light source for irradiation and air was introduced by a gas pump for supplying O2. The desulfurization yield of thiophene was 85.4% for a 3 h photoirradiation under the conditions with an air flow of 150 mL/min, water/oil ratio of 1:1 and riboflavin concentration of 30 μmol/L. The mechanism of photosensitized oxidation of thiophene is1O2 exited from 3O2 by the addition of riboflavin. Under the above conditions, the photooxidation kinetics of thiophene with O2/riboflavin is first-order with a rate constant of 0.3277 h−1 and half-time of 1.37 h.  相似文献   
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With new photocatalysts of gold nanoparticles supported on zeolite supports (Au/zeolite), oxidation of benzyl alcohol and its derivatives into the corresponding aldehydes can proceed well with a high selectivity (99 %) under visible‐light irradiation at ambient temperature. Au/zeolite photocatalysts were characterised by UV/Vis, X‐ray photoelectron spectroscopy (XPS), TEM, XRD, energy‐dispersive spectroscopy (EDS), Brauner–Emmet–Teller (BET) analyses, IR and Raman techniques. The surface plasmon resonance (SPR) effect of gold nanoparticles, the adsorption capability of zeolite supports and the molecular polarities of aromatic alcohols were demonstrated to have an essential correlation with the photocatalytic performances. In addition, the effects of light intensity, wavelength range and the role of molecular oxygen were investigated in detail. The kinetic study indicated that the visible‐light irradiation required much less apparent activation energy for photooxidation compared with thermal reaction. Based on the characterisation data and the photocatalytic performances, we proposed a possible photooxidation mechanism.  相似文献   
109.
On the surface : Adsorption of O2 at the surface oxygen vacancy (SOV) sites of TiO2 reconstructs the lattice oxygen (healing SOVs), resulting in a decrease of the photocatalytic activity of oxidizing CO over vacuum‐pretreated TiO2 with increasing temperature (see scheme). Adsorption of H2 produces new SOVs at the TiO2 surface and stabilizes the photocatalytic activity.

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110.
Oxidative changes in poly[methyl(phenyl)silanediyl] (PMPSi) films exposed in a Weather-O-Meter ATLAS Ci 3000+ were monitored by Fourier transform infrared spectroscopy. Increases in absorption in the siloxane, carbonyl, and hydroxyl regions, decreases in absorption in the Si Si region, and changes in the aromatic C H bond region were monitored. Experiments in argon and air indicated the key role of oxygen in the process. The photooxidation of PMPSi was retarded by triazine- and oxalanilide-based ultraviolet absorbers [2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-(hexyloxy)phenol and N-(4-tert-butyl-2-ethoxyphenyl)-N′-(2-ethylphenyl)oxalanilide] protecting the polymer by the excited-state intramolecular proton-transfer mechanism. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 714–721, 2004  相似文献   
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