【作者】 陈扬；

【导师】 王春明；

【作者基本信息】 兰州大学 ， 分析化学， 2010， 博士

【摘要】 本论文研究了TiO2／GE、树枝纳米Ag/Cu及Pd／Ag纳米复合薄膜材料的电化学制备方法、形貌分析及其在光催化降解、表面增强拉曼散射效应和超疏水性能等方面的应用,重点研究了半导体纳米TiO2对室内环境污染物甲醛的降解机理。应用阳极响应电流、阴极极化曲线、X-射线粉末衍射(XRD)、扫描电子显微镜(SEM)、原子力显微镜(AFM)、X光电子能谱(XPS)和拉曼光谱等技术研究所制得的纳米薄膜材料的性质与应用。论文主要内容包括：1.采用电泳沉积法分别在石墨电极(GE)和导电玻璃(ITO)表面沉积纳米YiO2,得到TiO2／GE薄膜电极和TiO2／ITO薄膜电极,并用X-射线粉末衍射(XRD)、场发射电镜(FE-SEM)及阳极响应电流试验对两种薄膜电极进行了表征分析。研究表明：和相同条件下制备的纳米TiO2／ITO电极相比,纳米TiO2／GE电极具有更强更稳定的光电流,能更有效地降低TiO2分子内光生电子与空穴的复合几率。通过对光催化降解酸性大红G的实验结果进一步证明,TiO2／GE电极对酸性大红的光催化降解效率更高,并可以重复利用。2.以纳米二氧化钛(TiO2)光催化降解甲醛,使用2-甲基-2-亚硝基丙烷(2-methyl-2-nitroso-propane, MNP)作为自旋捕截剂(spin trap, ST),研究了反应过程中的自由基中间体,得到了一种新的自旋加合物(spin adduct, ST-R)。电子顺磁共振(Electron Paramagnetic Resonance, EPR)的结果表明,甲醛在水溶液中降解的反应中间体为·CH(OH)2,并提出了一种新的降解机理。用Gaussian 98对自旋加合物的分子结构进行了几何优化计算,确定了其最稳定的构象,一些二面角的数据证明了EPR的实验结果。3.枝状分级的Ag纳米晶通过简单的置换反应制备,即AgNO3溶液与电沉积在ITO玻璃上的Cu微球间的化学反应得到。所制备树枝纳米Ag/Cu膜的组成、晶体结构及表面形貌分别由XPS、EDX、XRD及SEM表征。以罗丹明6G(R6G)为探针分子,表面增强拉曼散射光谱证明树枝纳米Ag/Cu膜具有很高的表面拉曼增强效应；经过十二硫醇的化学修饰,树枝纳米Ag/Cu膜表面呈现超疏水特性及低的接触角滞后性能。4.采用无电沉积的方法,分别以Ag和Pd催化晶籽层沉积Pd/Ag薄膜。薄膜的形态和组成分别用原子力显微镜(AFM)和X光电子能谱(XPS)表征。实验表明Ag晶籽不能催化Pd纳米粒子的沉积,得到的只是纯Ag,而非Pd/Ag合金；Pd晶籽却能催化Ag纳米粒子的沉积,得到的是Pd/Ag合金。同时,Ag纳米粒子在Pd晶籽上的沉积速率比在Ag晶籽上的快得多。以所制得的薄膜为工作电极,在暗态条件下测其阴极极化曲线,考察了析氢反应情况。更多还原

【Abstract】 In this thesis, TiO2/GE, dendritic Ag/Cu and Pd/Ag nano composite thin films are prepared by electrochemical or electroless techniques. The morphology and composition of the films are studied comparatively by using XRD, SEM, AFM and XPS. Promising multifunctional applications are obtained including photocatalytic degradation, strong surface-enhanced Raman scattering (SERS) enhancement and superhydrophobic application. The main contents are described as follows:1. Nano-TiO2 particles were immobilized on graphite electrode (GE) and indium-tin oxide coated glass (ITO) using electrophoretic deposition, respectively. The obtained TiO2/GE and TiO2/ITO film electrodes were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and anodic photocurrent response test. It was found that TiO2/GE electrode had much higher photocurrent and more effectively reduced the recombination rate of the photo-induced electron-hole pairs, compared with TiO2/ITO electrode. The photocatalytic activity of TiO2/GE was higher than that of TiO/ITO for the photocatalytic degradation of acid red G.2. Formaldehyde was degradated with photo-catalysis by TiO2 nanoparticles and 2-methyl-2-nitro-propane (MNP) was used as a spin trap (ST). The radical intermediates in the process of reaction were studied and a new spin adducts (ST-R) was obtained. The results of Electron Paramagnetic resonance (EPR) indicated that intermediates of formaldehyde degradation in aqueous solution were·CH(OH)2. And a new degradation mechanism was proposed.3. Hierarchical and well-defined Ag dendrites were obtained by the reaction between copper microspheres electrodeposited on ITO and a solution of AgNO3. The composition, crystal structure and morphology of the deposits were characterized with XPS, EDX, XRD and SEM, respectively. The dendritic Ag/Cu film show significant SERS effect as probed with Rhodamine 6G (R6G). And also the surface of dendritic Ag/Cu film had a remarkable superhydrophobic property and low contact angle hysteresis after treatment with n-dodecanethiol.4. Pd/Ag films were electrolessly deposited onto p-silicon (100)-activated seed layers of Ag and Pd, respectively. The morphology and composition of the films were studied comparatively by using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Cathodic polarization curves for hydrogen evolution were recorded in 0.5mol/L H2SO4 without illumination. The experimental results showed that the film obtained on the Ag seed layer was rather a pure Ag film and not a Pd/Ag film, and also the Ag deposition rate on Pd sites was much faster than that on Ag sites.更多还原