【作者】 石建英；

【导师】 李灿；

【作者基本信息】 中国科学院研究生院（大连化学物理研究所） ， 物理化学， 2007， 博士

【摘要】 光致发光光谱是一种研究半导体材料电子结构、光学及光化学性质的有力技术。半导体光致发光过程与光催化过程的电荷转移、复合有着本质的联系,通过对半导体光催化剂光致发光光谱的研究,可以得到半导体表面缺陷态的信息,可以了解半导体表面或近表面光生载流子的捕获、转移、分离过程及其对光催化活性的影响。这些信息将有助于我们认识复杂的光催化过程。利用光致发光光谱技术,对人们所关注的TiO2、NaTaO3及ZnxCd1-xS光催化材料进行了深入研究。对于TiO2催化剂,研究了其光致发光性质与晶相结构间的关系,发现可见及近红外区的两个发光带分别与锐钛矿中的氧缺陷及金红石中的本征缺陷相关;TiO2表面金属Pt担载前后光致发光光谱及光催化水分解反应活性的变化表明,锐钛矿氧缺陷捕获的电子可以转移到金属Pt上参与光催化反应,而金红石本征缺陷则主要作为光生载流子的复合中心。对于在紫外光照下产氢及产氧的良好的NaTaO3光催化剂,利用光致发光光谱灵敏地检测到其它表征手段难以观察到的缺陷态并考察了制备条件对缺陷态的影响。采用简单、廉价的方法制备了ZnxCd1-xS纳米晶,这些纳米晶具有高结晶质量、高发光效率,并且呈现出组成依赖的光学性质。结合稳态及时间分辨光致发光光谱技术,对组装于分子筛孔道内的ZnO、ZnS及TiO2半导体材料由量子尺寸效应引起的特殊的光学性质进行了研究。分子筛孔道内的ZnO簇在室温下呈现出微秒量级的光致发光寿命。随着担载量的增加,ZnO簇与分子筛主体间的电子-声子相互作用减弱,而ZnO簇间的相互作用增强,相应地由分子筛主体及界面的声子所决定的无辐射弛豫过程被抑制,从而在室温下观察到微秒量级的发光寿命。这些研究结果对于认识半导体氧化簇与分子筛孔道间相互作用的本质有重要意义。更多还原

【Abstract】 Photoluminescence spectroscopy is a very powerful technique for the characterization of the electronic states, optical and photochemical properties of semiconductors, etc. The study of semiconductor photocatalysts by the photoluminescence spectroscopy can not only give the information of defect states in semiconductors, but also the information of transfer, trapping and separating of the photogenerated charge carriers. These information is extremely important for us to understand the complicated mechanism of photocatalytic reactions.In this dissertation, the semiconductor photocatalysts of TiO2, NaTaO3 and ZnxCd1-xS are studied by the photoluminescence spectroscopy. The relations of the photoluminescence properties of TiO2 with its crystal structures are clarified f. Anatase TiO2 displays a visible luminescence band centered at 505 nm and rutile TiO2 mainly shows a near-infrared luminescence band centered at 835 nm, which are respectively ascribed to the oxygen vacancies in anatase TiO2 and the intrinsic defects in rutile TiO2. The excited electrons trapped in the oxygen vacancies of anatase are facilely transferred to Pt deposited on the surface of TiO2 to contribute to the photo-assisted reaction, but the electrons transfer from the intrinsic defects of rutile to Pt deposited on the surface of TiO2 are not observed. The photoluminescence properties of NaTaO3 are sensitive to its defect states, and its photocatalytic activities are also influenced by these defect states. The luminescence features of NaTaO3 synthesized under different conditions are studied and the origins of these emissions are discussed. The high-quality andhigh-quantum-yield ZnxCd1-xS nanocrystals are synthesized by a facile and mild approach involved in precipitable-hydrothermal processes. With the increase of Zn molar fraction, the absorption band onsets, near band edge luminescence and deep level luminescence systematically shift from the longer wavelength for CdS to the shorter wavelength for ZnS.As the semiconductor particle size decreases, its optical properties of the particle, such as bandgap and photoluminescence lifetime, are usually changed due to the quantum effect. The special optical properties of semiconductor clusters confined in pores of micro-zeolites are also investigated by the steady-state and time-resolved photoluminescence spectroscopy. The ZnO, ZnS and TiO2 semiconductor clusters confined in micropore zeolites (HZSM-5, HBeta, etc.) show the significantly different optical behaviors from their bulk material, for example, the blue-shifts of the absorption onset and the luminescence bands. The microsecond luminescence lifetime of ZnO clusters is observed at room temperature, which is significantly affected by the electron-phonon interaction between ZnO clusters and zeolite host. The long-lived luminescence of ZnO clusters can be obtained by controlling ZnO loadings and reducing the coupling of electronic transition from ZnO to host phonons of zeolites.更多还原