【作者】 潘海波；

【导师】 黄金陵； 陈耐生；

【作者基本信息】 福州大学 ， 物理化学， 2006， 博士

【摘要】 TiO₂的晶型结构是影响其材料应用性能的关键因素,其中金红石相TiO₂具有氧气敏感特性,而锐钛矿相TiO₂则具有较高的光催化活性。迄今为止,金红石相TiO₂的制备由于采用四价钛源,需经高温烧结（≥700℃）,所制得氧敏元件存在工作温度较高（≥250℃）、选择性、稳定性较差等缺点。此外,酞菁与卟啉配合物敏化TiO₂的方法是提高锐钛矿相TiO₂光催化效率的有效手段之一,也是目前研究的热点。这两类敏化剂在可见光区具有强吸收、理化性能稳定等优点,但其制备方法主要是利用已合成的TiO₂纳米颗粒浸渍敏化剂而成,该制备方法由于敏化剂与基质（TiO₂）之间耦合效果较差,导致敏化效果不理想。本文在氧敏材料方面,尝试以TiCl3为源物质,采用溶胶-凝胶法,经低温（400℃）烧结制成金红石相纳米掺杂氧敏材料,并测试其厚膜型元件的气敏性能,以期获得性能良好、接近于实用的半导体型氧敏传感材料。在有机敏化TiO₂复合材料方面,分别利用两种合成方法,即一般溶胶-凝胶法与原位自组装一步合成法,合成三类有机敏化TiO₂复合纳米材料,并采用多种物理、化学测试方法对其进行表征,在此基础上,选择有机染料为待降解物,以探讨其可见光光催化机理。主要结果如下: 一、以TiCl3为源物质,利用溶胶-凝胶法,经n型掺杂(V⁵⁺, Nb⁵⁺,Ta⁵⁺,Cr⁶⁺, Mo⁶⁺, W⁶⁺)、低温（400℃,1h）烧结即可获得金红石结构; 并筛选出掺杂量为18mol%的V5+/TiO₂气敏材料,该材料制成的元件具有氧敏（100ppm）灵敏度（S=16）、工作温度（80℃）、响应特性、选择性、稳定性均较好; 探讨了掺杂过程相变机理。二、首次利用Zeta电位与变温磁化率等测试手段来表征表面带电特性,分析其与结构、气敏特性之间的关系,提出掺杂增敏与影响选择性机理。三、利用一般溶胶-凝胶法,制备轴向取代酞菁（TiOPc）/ TiO₂纳米复合材料,当TiOPc:TiO₂=1mol%时,TiOPc以单分子形式存在于TiO₂表面,在可见光（15W,2h）照射下,罗丹明B染料光催化降解率达60%。四、首次采用原位自组装方法,制备了两类（CoPc/TiO₂, ZnTPP/TiO₂）纳米复合材料。发现配合物以单分子形式原位自组装于TiO₂颗粒表面,通过轴向与基质TiO₂之间存在较强化学耦合,能促使光生载流子快速分离与能量有效转移,使配合物与TiO₂形成更有效协同光催化作用。在可见光（15W,2h）照射下,ZnTPP/TiO₂催化剂对罗丹明B染料降解率达90%。更多还原

【Abstract】 The properties of TiO₂ materials are dependent on it’s crystal phase. In this respect, the conductivity of TiO₂ with rutile phase is sensitized to oxygen gas, while TiO₂ with anatase phase has high photocatalytic activity. Up to now, only tetravalent titanium （Ti4+） has been used as the source materials prepared for rutile phase applied as oxygen sensor. In the case that tetravalent titanium was used, the rutile phase was obtained through a higher sintering temperature （≥700℃）. This leads to that the properties of oxygen sensor made by the materials would attenuated due to it’s higher operating temperature （≥250℃）, and with bad stability and selectivity. On another application, it is known that the method of the metallophthylocyanine （or metalloporphyrin） sensitized TiO₂ is an efficiency process for advancing photocatalytic activity. And now, dye sensitization of wide-band gap nanocrystalline semiconductors is attracting owing to the two dyes show strong absorption at visible light section and stability of physical and chemical properties. The synthesis processes for TiO₂ sensitized by the dyes were all chosen by dip-coating with TiO₂ nanoparticles or spin-coating on TiO₂ film. However, the interaction between the dyes and TiO₂ is infirmness and the efficiency of these sensitized TiO₂ is limited In this thesis, the source materials with trivalent titanium （Ti3+） is firstly used at the synthetic procedures for rutile TiO₂. The rutile doped with pentavalent or hexavalent impurity ions was obtained at lower sintering temperature （400℃） during sol-gel process. It is hoped that by using this process the substantial increases in oxygen sensing properties by doping with the impurity will be obtained. On the other hand, three photocatalysts were obtained by using the general sol-gel process and an in-situ, self-assemblying process, respectively. The catalytic activities of modified TiO₂ were examined by using rhodamine B and methylene orange solutions as organic substrates under visible– light excitation. The characterization of structure and spectra for modified TiO₂ was made. And a new mechanism of enhanced activity was elucidated. 1. Nanoscale TiO₂ powders doping with V⁵⁺, Nb⁵⁺,Ta⁵⁺, Cr⁶⁺, Mo⁶⁺, W⁶⁺ ions were prepared using TiCl3 as a source matter. The ruitle with doped TiO₂ was obtained at lower sintering temperature （400℃,1h）. It has been found that the 18mol% V5+ incorporated TiO₂ shows the maximum sensitivity （S=16）, lowest operating temperature （80℃）, shorter response time, good selectivity and stability. A mechanism of the anatase-rutile transformation in doped TiO₂ is suggested. 2. The Zeta potential and susceptibility with temperature were first carried out in the gas sensing materials, and used to analyze the relationship among the charge behavior on the surface, structure and gas properties. The mechanism, i.e., enhancement in sensitivity and selectivity for TiO₂ doped by pentavalent and hexavalent impurity ions, has been proposed. 3. Using TiOPc with an axial ligation as sensitizer, TiOPc/TiO₂ compound was obtained by a general sol-gel process. The non-aggregated TiOPc molecules are self-organized on the TiO₂ particle surface only at TiOPc: TiO₂=1mol%. The 54% of rhodamine B was degraded by this photocatalyst under visible light （15W, 2h）. 4. Cobalt phthalocyanine （CoPc）/TiO₂ and Zinc tetraphenylporphyrin （ZnTPP） / TiO₂ were synthesized by using a novel method, i.e., in-situ process. The monolayer of dye molecules is self-organized on the TiO₂ particle surface only at suitable molar ratio of dye and TiO₂. The IR and fluorescence spectra showed distinctive interaction between sensitizer molecule and TiO₂ at the axial direction of dyes. The charges excited by visible light are rapidly separated, and at the same time the energy is transfer efficiently from dye to semiconductor. The enhanced activity originates from the cooperative functions of the two components of the photocatalyst, sensitizer and TiO₂. The degradation of rhodamine B by ZnTPP/TiO₂ photocatalyst is up to 90% under same visible light （15W, 2h）.更多还原