【作者】 刘恒权；

【导师】 姚素薇；

【作者基本信息】 天津大学 ， 应用化学， 2003， 博士

【摘要】 纳米金属颗粒和纳米薄膜材料在非线性光学、力学、磁学、电学、表面催化和传感等领域表现出优异的物理和化学特性，可作为介电材料、电极材料、仿生材料、磁存储材料及敏感材料等，有着广泛的应用前景。本论文采用光化学、化学和电化学技术，制备贵金属Au、Ag 纳米颗粒和Ag 纳米薄膜，借助于TEM、SEM、XPS、XRD、UV-vis、IR、SERS等现代测试技术对材料的纳米尺度、形状、结构特点、晶型转变、化学物理特性及其生长机制进行了较为系统的研究。以聚乙烯吡咯烷酮(PVP)和柠檬酸三钠(TSC)为软模板，采用化学还原法制备球形Ag 纳米粒子。PVP在控制Ag 颗粒尺度方面明显优于TSC。实验结果表明PVP能够阻止Ag 粒子长大，经研究，这是由于PVP与Ag+ 首先发生配位络合反应，化学还原后的Ag 粒子表面吸附有PVP，产生较大的高分子链空间位阻作用，阻止了Ag 粒子之间的团聚和长大。首次将TSC和PVP作为稳定剂制备的球形Ag 纳米粒子置于500 W卤钨灯下，进行光诱导转化实验，球形Ag 颗粒转化为三角形和正方形Ag 单晶体。探讨了光照下球形Ag 粒子转化为三角形和正方形Ag 单晶体的原因。利用紫外线辐射PVP-AgNO3水溶液，光还原获得球形Ag 纳米粒子。经理论推导Ag+ 光还原反应属于准一级反应。此外，还提出了Ag+ 光还原反应机理及PVP 稳定Ag 粒子的机理。采用柠檬酸钠还原法制备球形Au 纳米粒子。增大柠檬酸钠用量，制得的Au 粒子直径变小，单分散性提高。在制备Au 溶胶的同时加入光照作用，所制备的Au 粒子较相同条件下无光照时的粒子直径大；但在PVP或PVA存在条件下，光照对粒子的直径不产生影响。使用柠檬酸钠－单宁酸还原法制备的Au 粒子的直径最小，约为1~3 nm，单分散性最好。首次采用光还原方法在线性壳聚糖膜内成功地制备了三角形、六边形Ag 单晶体，晶体结构由多晶转变为单晶结构的主要原因是配位稳定状态改变和光能的共同作用。首次采用电化学方法，在线性壳聚糖膜内获得粒径为5~8 nm的球形Ag 粒子，还原过程中无Ag 晶型转变现象。在气/液界面单分子膜上及气/固界面单层LB膜上自组装Ag 纳米材料。在单分子膜/单层LB膜的诱导下，通过化学沉积和电沉积方法得到光亮、细致及不同形貌(网状、树枝状)的纳米Ag薄膜。实验发现，镀液的pH值对Ag 膜产生显著影响，对此进行了理论分析与计算，提出了单分子膜及单层LB膜诱导沉积Ag 膜的生长机制。首次将硬脂酸单分子膜上化学/电化学沉积的Ag 膜作为表面增强拉曼效应的活性基底，测得了硬脂酸单分子膜的Raman光谱；以吡啶为探针分子测试了吡啶的表面增强拉曼光谱，结果表明该Ag 膜具有较强的表面增强拉曼散射(SERS)效应。通过对硬脂酸单分子膜Raman光谱分析，确定硬脂酸单分子膜垂直吸附在Ag 膜的表面。更多还原

【Abstract】 Interest in metal nanoparticles and nano-films stems mainly from their size-dependent physicochemical properties, making them potential candidates for a wide variety of applications in nonlinear optics, mechanics, magnetics, electrics, catalyzer and sensor.The purposes of this dissertation are to study the preparation of Ag nanoparticles, Au nanoparticles and Ag nano-films by photochemical, chemical and electrochemical techniques. By means of characterization methods with TEM, SEM, XPS, XRD, UV-vis, IR and SERS, the influencing factors, growth mechanism and related properties of these metal nano-materials have been investigated.PVP and TSC used as soft-templates, spherical Ag nanoparticles were prepared by chemical reduction. PVP is superior in controlling the particle diameter of Ag nanoparticles to TSC. The results show that PVP firstly coordinates Ag+, then PVP adsorbs in the surface of Ag particles so that prevents Ag particles from growing and reuniting.For the first time, preparation of Ag nanoparticles with non-spherical shape has been conducted from spherical Ag nanoparticles by photoinduced conversion. Triangular and foursquare Ag nanoparticles were respectively obtained in the presence of TSC or PVP. These non-spherical Ag nanoparticles are single-crystals. The fundamental analysis and discussion about the changing causes of nanoparticles shape from spherical to non-spherical have been carried out in photoinduced process. The Ag nanoparticles were prepared by illuminated PVP-AgNO3 aqueous solution. The process of the Ag+ photo reduction follows guise first order reaction. Both the reduction mechanism of Ag+ and the stabilization mechanism of Ag nanoparticles have been presented.Au nanoparticles were prepared by sodium citrate reduction method. The results show that the increase of TSC results in the decrease of the particle diameter of Au nanoparticles and the improvement of monodispersity of Au nanoparticles. The particle diameter of these nanoparticles will become bigger when them are irradiated by photo, but their diameter does not change in the presence of PVA or PVP. The particle diameter of Au nanoparticles becomes smaller when sodium citrate-tannin are used as reducing agent.In-situ preparation of spherical silver nanoparticles(10~30 nm), triangular and <WP=5>hexangular single silver crystal(200~2000 nm) have been conducted in linear Chitosan films by photochemical reduction. The monodispersed spherical silver nanoparticles(5~8 nm) were also electrochemically obtained in the film. By means of characterization with TEM, SEM, IR Spectra and XRD, the fundamental analysis and discussion about the changing causes of silver crystal structure from multi crystal to single crystal have been carried out in photochemical reduction process. The cause lies in the function of both the change of coordinating stability and the photo irradiation.Ag nano-films were obtained by electroless deposition method through induction of stearic acid mono-Langmuir-Blodgett film at air/solid interface or stearic acid monolayer at air/solution interface. The results showed that the pH of sub-phase had an important effect on the microscopic structure of the Ag film, then the cause of which was theoretically analyzed and computed. The possible growing mechanism of silver deposition on monolayer was preliminarily discussed. A novel method fabricating Ag nano-film has been presented, by which we may control the surface microstructure of silver film easily.These Ag films prepared on stearic acid monolayer were used as SRES-active substrate, on which the surface-enhanced Raman scattering spectrum of stearic acid monolayer was obtained for the first time. Moreover, the SERS activity of the Ag film fabricated on mono-Langmuir-Blodgett films was investigated by pyridine as the probe, which strongly indicated their potential application in SERS substrate materials. It was found that stearic acid monolayer vertically adsorbed in the surface of Ag films by analyzing the SERS spectrum of stearic acid monolayer.更多还原