【作者】 李钱陶；

【导师】 张兆艳； 何峰；

【作者基本信息】 武汉理工大学 ， 材料学， 2003， 硕士

【摘要】 Ag-无机纳米复合材料由于具有高的三阶光学非线性、光致发光、光致变色等性质而受到人们的关注。本文采用溶胶-凝胶法在浮法玻璃基片上制备了Ag-SiO₂纳米复合薄膜，研究了复合膜的光吸收性能和光致发光性能，分析了掺杂浓度为Ag／Si=0.10（原子比）复合膜的微结构及银纳米粒子的形成过程。 以TEOS和AgNO₃作为主要原料，用有机硅烷（APS）作为Ag⁺的络合剂，通过优化工艺参数，制备出了掺杂浓度为0.01～0.10、Ag⁺稳定存在的Ag-SiO₂复合溶胶，采用浸镀法以8～32cm／min的提拉速度在浮法玻璃基片上镀制了Ag-SiO₂复合薄膜。采用DSC-TG和SEM分析了复合膜的凝胶过程。结果表明，450℃处理后，复合体系内的有机残留物氧化完毕，形成的薄膜表面致密。 以Mie和Maxwell-Grarnett（M-G）有效介质理论为基础，分析了工艺因素对样品光吸收性能的影响。结果表明，复合膜的处理温度、银的掺杂浓度和薄膜制备时的提拉速度都可使样品的银粒子的大小、数量和分布产生变化，从而影响样品的光吸收性能。 采用荧光光度计测定了Ag-SiO₂纳米复合薄膜的光致发光性能。发现样品中存在三个激发中心，分别位于228、266和325nm。研究了样品在228和325nm光激发下的发光性能及发光机理。研究结果表明，复合膜的发光主要与处在不同化学状态的Ag有关。在228nm光激发下，复合膜中Ag⁺的电子的¹D₂→¹S₀跃迁和³D→¹S₀跃迁分别在365和460nm附近发光，聚集在复合膜表面的纳米银粒子的表面等离激元共振导致了400nm附近的发光。在325nm光激发下，复合膜在350～500nm和640～690nm之间发出荧光，这些发光主要由银簇和银纳米粒子所引起。 采用XRD、FTIR、XPS、TEM等手段研究了复合薄膜的微结构。结果表明，基质SiO₂以非晶态形式存在，银纳米粒子均匀地分布在基质中；在热处理过程中，基片中的Na⁺进入了复合膜中，导致基质Si-O网络结构的变化。 将OA和PL谱相结合，作为一种研究手段以区别复合膜中银粒子、银簇和Ag⁺，并在一定程度上反映Ag与基质的耦合情况。这一方法在分析银纳米粒子的形成过程中得到了初步的运用。结果表明，在样品的热处理过程中，浮法玻璃下表面的Sn²⁺将Ag⁺还原成Ag⁰，这是银粒子形成的关键；基片中的Na⁺与复合膜中的Ag⁺互扩散促进了银纳米子的形成。更多还原

【Abstract】 Ag-inorganic nano-composite systems have attracted special attention during the past decade, due to their interesting properties such as high third-order nonlinear optical susceptibility, photoluminescence and photochromism, etc. In this paper, Ag-SiO2 nano-composite films on commercial float glasses have been prepared by sol-gel method. The optical absorption (OA) and photoluminescence (PL) properties of the films have been studied. The microstructure of the films with Ag/Si=0.10 (atom ratio), and the formation of the silver nanoparticles during theheat-treatment, have been analyzed.The Ag-SiO2 composite sols, with Ag/Si=0.01-0.10 and stable Ag+ availability, have been prepared after optimizing the technical parameters, by using TEOS and AgNO3 as the main predecessors and functional silane (APS) as the completion of Ag+. The composite films on float glasses have been prepared, by using dip-coating method with drawing speed 8-32cm/min. The gelification process of the composite has been investigated by using DSC-TG and SEM measurements. The results show that the organic residual has been decomposed completely and the crack-free films can be obtained after heat-treated higher 450℃.Based on Mie and Maxwell-Grarnett (M-G) effective medium theory, the effects of technical factors on the optical absorption properties of the samples have been analyzed. The heat-treatment temperature, the doping concentration of Ag (Ag/Si) and drawing speed of the substrates can regulate the size, amount and distribution of silver nanaparticles in the matrix, and then influence the optical absorption of the samples.The PL spectra of the Ag-SiO2 composite films have been obtained from the fluorophotometer. There are three excitation centers in the samples located at 228nm, 266nm and 325nm. The photoluminescence properties and mechanisms of samples, " excited with 228nm and 325nm, have been studied. The results indicate that the photoluminescence mostly associate with Ag, which are in different chemical states. Excited with 228nm, the emission bands centered at about 365nm and 460nm originate from the electron transitions of 1D2-1S0 and 3D-1S0 in Ag+ respectively, and the emission band at 400nm results from the surface plasma resonance of the silver nanoparticles, which aggregated near the surface of the films. Excited with 325nm, theemissions bands of 350~500nm and 640-690nm due to the silver clusters and silver nanoparticles respectively.The microstructure of the films has been investigated by XRD, FT1T, XPS and TEM. The results indicate that the SiO2 matrix exists in form of noncrystalline state, and the silver nanoparticles distribute in the matrix homogenously. The entrance of Na+, which comes from the substrates, can change the structure of Si-O network of the film during the heat-treatment.The combination of OA and PL spectra can be used as a tool to distinguish silver nanoparticles, silver clusters, silver atoms and silver ions in the sol-gel films, and can reflect the coupling of Ag and matrix in some degree. This analytical method has been put into practice to analyze the formation of silver nanoparticles during the heat-treatment. The results show that the chemical composition of substrate surface and the heat-treatment regime are the major influencing factors on the formation of silver nanoparticles. During the heat-treatment, Sn2+ in the bottom face of the float glasses reduce Ag+ to Ag? which is the key to form silver nanoparticles. And the interdiffusion between Na+ and Ag+ promotes the formation of silver nanoparticles.更多还原