环缩醛类化合物光还原法制备银纳米粒子的研究

发布时间：2018-11-23 07:35

【摘要】：金属纳米粒子,尤其是银纳米粒子,在制备、表征和应用方面有很长的历史。银纳米粒子性能优异,具有与众不同的物理化学性质,包括：较高的导电性、热导率、表面增强拉曼散射,化学稳定性好,催化活性高,具有非线性光学行为等。纳米粒子新颖的性质已经被广泛的应用到药物、化妆品、可再生能源、环境修复和电子设备中。但是传统的制备方法存在许多缺点,如反应条件苛刻、尺寸不均一、可控性差等。近年来,一种新的绿色环保的光化学还原法引起了人们广泛的关注。此方法可在室温条件下反应,适用范围广,制备过程方便,具有时间可控,空间选择性制备等优点,已被用于合成各种结构的单金属、双金属纳米粒子,还有复合材料。本文使用绿色植物提取物环缩醛化合物,用光化学还原的方法制备了银纳米粒子,替代目前光化学合成方法中使用的人工合成光引发剂,使得此方法更加绿色环保。并且对反应体系的影响因素和反应机理进行了研究。主要工作如下：1、设计了环缩醛化合物光化学还原制备银纳米粒子的路线。经过对反应条件的探索,选择硝酸银作为银前驱体,乙醇为溶剂,汞灯作为光源。X射线衍射结果表明产物为银粒子,透射电子显微镜结果表明其为纳米尺寸。2、研究了反应体系的影响因素：环缩醛化合物、溶液浓度、反应温度对体系的影响。溶液浓度对纳米粒子的尺寸有重要影响,溶液浓度增大,纳米尺寸越大,分布变宽。溶液浓度为10-4 mol/L时,生成的银纳米粒子的粒径分布窄。当浓度增大至0.01 mol/L时,形成的银纳米粒子变得不稳定,部分悬浮在溶液中的纳米粒子开始形成沉淀,粒径分布变宽：体系温度对形成的纳米粒子有两方面的影响,方面对纳米粒子的尺寸有影响,另一方面对形成的纳米粒子的数量有影响。随着反应温度的增加,形成的银纳米粒子的粒径增大,纳米粒子附着在玻璃表面的量增多。3、用紫外可见光谱和气相色谱质谱联用仪表征反应的机理。结果表明：BDO在光照下,在较活泼的亚甲基位置产生自由基。BDO自由基、溶液中的Ag+和溶剂醇类分子发生反应,自由基将银离子还原,溶剂中的氢原子参与反应,生成2-甲(乙)氧基-1,3-苯并二氧戊烷,零价态的Ag原子和离子氢。零价态的Ag通过成核生长为银纳米粒子。
[Abstract]:Metal nanoparticles, especially silver nanoparticles, have a long history in preparation, characterization and application. Silver nanoparticles have excellent physical and chemical properties, including high conductivity, thermal conductivity, surface enhanced Raman scattering, good chemical stability, high catalytic activity and nonlinear optical behavior. The novel properties of nanoparticles have been widely used in medicine, cosmetics, renewable energy, environmental repair and electronic equipment. However, the traditional preparation method has many disadvantages, such as harsh reaction conditions, uneven size, poor controllability and so on. In recent years, a new green photochemical reduction method has attracted wide attention. This method can react at room temperature with wide range of application, convenient preparation process, controllable time, selective preparation of space and so on. It has been used to synthesize monometallic, bimetallic nanoparticles and composite materials with various structures. In this paper, silver nanoparticles were prepared by photochemical reduction with cyclic acetal compounds of green plant extracts, which replaced the synthetic photoinitiators used in the present photochemical synthesis methods, which made the method more green and environmentally friendly. The influencing factors and reaction mechanism of the reaction system were also studied. The main work is as follows: 1. The route of photochemical reduction of cyclic acetals to silver nanoparticles was designed. After exploring the reaction conditions, silver nitrate was selected as silver precursor, ethanol as solvent and mercury lamp as light source. The X-ray diffraction results showed that the product was silver particle, and the transmission electron microscope showed that the product was nano-sized. The effects of cyclic acetal compounds, solution concentration and reaction temperature on the reaction system were studied. The solution concentration has an important effect on the size of nanoparticles. The larger the solution concentration, the wider the distribution. The particle size distribution of silver nanoparticles was narrow when the concentration of solution was 10 ~ (- 4) mol/L. When the concentration increased to 0. 01 mol/L, the formed silver nanoparticles became unstable, and some of the nanoparticles suspended in the solution began to form precipitates, and the particle size distribution became wider: the temperature of the system had two effects on the formed nanoparticles. Aspects affect the size of nanoparticles, on the other hand, the number of formed nanoparticles. With the increase of reaction temperature, the particle size of the silver nanoparticles increased and the amount of the nanoparticles adhered to the glass surface increased. 3. The mechanism of the reaction was characterized by UV-Vis spectra and gas chromatography-mass spectrometry (GC-MS). The results show that BDO produces free radicals at active methylene sites under light. BDO radical reacts with solvent alcohols, free radicals deoxidize silver ions, and hydrogen atoms in solvents take part in the reaction. 2-Methyl (ethyloxy) -1-oxy-3-benzodioxopentane, zero-valence Ag atom and ionic hydrogen are formed. Ag with zero valence state grows into silver nanoparticles by nucleation.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O614.122;TB383.1

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