【作者】 魏慧英；

【导师】 吴佑实；

【作者基本信息】 山东大学 ， 材料学， 2005， 博士

【摘要】 纳米半导体材料在光伏电池、光电传感器、光谱发射和光催化等方面有着重要的潜在应用价值,因此近几年来得到了广泛的研究。TiO₂纳米粒子不仅具有很高的光催化活性,而且具有耐酸碱和光化学腐蚀、成本低、无毒的特点,是目前最有应用潜力的一种光催化剂。锐钛型TiO₂的带隙能Eg=3.2eV,只有小于360nm的紫外光才能激发,因此我们研究的重点是提高纳米TiO₂对可见光的利用率并增加其比表面积。 ZnO纳米晶属宽能隙直接带材料,室温下禁带宽度为3.37ev,其光谱包括一个宽而强的蓝一绿光发射带,一个弱而窄的紫外发射带。为得到强的蓝紫光发射材料,我们研究了金属离子和非金属掺杂的ZnO纳米晶,ZnO纳米棒,以及有机无机复合材料。主要研究内容包括以下几个方面: 1.利用化学共沉淀法制备了La³⁺离子掺杂的TiO₂纳米晶,然后在NH₃气氛中煅烧得到La和N共掺杂的样品。其粒晶为5-15nm,比表面为65-125m²/g。微结构表征和光谱研究表明,非金属元素N可取代少量O原子,通过N2p和Ti3d轨道的相互作用,在半导体中产生新的掺杂能级,N掺杂降低了TiO₂纳米晶的带隙能,0.5%La³⁺离子掺杂增大了样品的比表面积,La³⁺和N共掺杂的TiO₂在可见光（350<λ<450nm）作用下表现出极强的催化活性,可将20mg/l的甲基橙水溶液在一小时内完全降解。 2.在强碱性条件下水热法制备了二氧化钛纳米管,通过400℃空气中煅烧和500℃还原性气氛中纳米管的断裂试验表明:纳米管完全横向断裂为均匀大小的‘空心砖’结构,且由锐钛矿相完全转化为金红石相。,XRD和HRTEM研究发现,纳米管为沿（101）晶面生长的锐钛矿结构,管壁为多层的开口管。其生长机理可解释为纳米晶粒子经过片状钛酸盐结构连接卷积而成。紫外可见吸收光谱显示其对500-800 nm可见光有弱吸收,对260nm附近的紫外光有强吸收。 3.选取了与Zn²⁺半径相近,氢氧化物和碳酸盐的Ksp相近的Mn²⁺、Cu²⁺和Cr³⁺离子分别对ZnO掺杂,采用共沉淀法合成了微量Mn²⁺,Cu²⁺和Cr³⁺离子分别掺杂的ZnO纳米晶体。研究其光致发光性能。研究发现,金属离子掺杂不影响ZnO更多还原

【Abstract】 Nanometer scale semiconductor materials have been studied extensively in recent years because of their important applications in photovoltaic cell, sensing, optical emission and photocatalysis. Titanium dioxide is widely known to be the best photocatalyst due to its chemical stability, low cost and no toxicity. Since it act only by UV irradiation at around 360 nm region （Eg=3.2ev for anatase）, so we have focused on T1O2 nanocrystallites to improved the utilization ration of visible light and increase the surface area.ZnO is a wide direct band gap （3.27eV） semiconductor, it can emit photons of UV light and broad visible spectrum, in order to get strong violet-blue emission, we investigated ZnO nanocrystallites doped with metal and nonmetal ions, and nanocrystallites composite. Here,it mainly contains 6 parts as follows: l.Nanoparticles of TiO₂ powder co-doped with La and N were prepared using a coprecipitation method followed by being two hours calcinated at a temperature ranging from 500 to 600℃ in NH₃/Ar atmosphere. Uniformly co-doped TiO₂nanocrystalline was 5-15 nm with surface area 65-125 m²/g. Optical absorption along with the microstructural investigation for monodoped and co-doped catalyst provided that a part of O vacancy of Ti₅O₉ was occupied by N, which is responsible for the band-gap narrowing of TiO₂, while La³⁺ doping prevents the aggregation of powder in process of nitrification. Superior catalytic activity was observed in the co-doped TiO₂ under visible light （350<λ<450 nm）. 20 mg/l methyl orange solution could be docomposed completely within 1h using the 0.5 at.% La³⁺ doped TiO₂ calcinated in NH₃ for 2h.2.TiO₂ nanotubes were prepared by treatment of TiO₂ nanocrystallites in mild hytrothermal conditions in alkaline solution, then calcined at 400℃ in air and 500℃ in NH₃/Ar atmosphere. TiO₂ nanotubes were characterized by HRTEM,XRD and UV-Vis spructra. It shows that the nanotubes possess a layered structure and the tubeaxis is determined to be along （010） direction of the anatase phase. The formation mechanism of the nanotubes can be explained as folded sheets with a t^TiaC^ structure. The UV-Vis spectra shows a strong absorption in 260 nm.3. ZnO nanocrystallines doped with Cu2+ , Mn2+ and Cr3+ have been obtained by chemical precipitation from homogeneous solution ,respectively.Their emission properties have been researched for the first time.The results indicate that the red light emission are significantly quenched and blue-green light emission are strongly enhanced. The luminescence characteristics and corresponding mechanism for doped ZnO are reviewed.4.ZnO nanoparticles doped with nitrogen on surface were prepared by calcinating pure ZnO nanoparticles at 550°Cand 600°C in NH3 atmosphere. Uniform N-doped ZnO nanocrystal was characterized by TEM, XRD and XPS. A Strong violet photoluminescence at 400nm was observed at room temperature when excited with 300nm light, and the emission peak increases with the increase of nitrogen atoms concentration. The violet PL originated from the electron transition from shallow donor levels of oxygen vacancies and doping nitrogen atoms to the top of valence band level.5.ZnO nanorods were prepared by hydrothermal synthesis using Zn（OH）42" precursor in alcohol solution without and with the assistant of dodecyl benzene sulfonic acid sodium salt DBS or ethylenediamine at 110°C and 180°C. The microstructure of samples was studied by X-ray diffraction （XRD）, high-resolution transmission electron microscope （HRTEM） and selected area electron diffraction （SAED）. The results show that single crystalline ZnO nanorods grow from ZnO nuclei spontaneously, and +c-axis （（001） direction） is the fast growth direction. This landing mode predominant in decreasing the high interfacial free energy caused by high symmetry of the （001） faces. The effect of the surfaces were discussed. Photoluminescence （PL） spectrum at room-temperature shows a UV emission near 400nm, which is likely related to the emission of high concentration excitons; and a yellow-green light emission at 550nm, which is related to defects in the rods.6. A ZnO/PANI composite nanoparticles has been synthesized using a simplechemical method. The TEM,XRD, UV-Vis and fluorescence spectra were used to characterized the composite nanoparticles. It shows that the ZnO/PANI possess "core-shell" structure. A dramatic increase in the luminescence intensity in the emission wavelength have been observed from the composite,company with the strong blue emission, the red emission decreased rapidly.更多还原