微波法快速合成纳米银及影响因素研究

发布时间：2019-02-24 15:35

【摘要】：纳米银材料由于显示出独特的性能,如小尺寸效应、表面效应和量子隧道效应等,成为现阶段科学研究的热点,并且在催化、消费电子、医学等领域有着广泛的应用。银纳米材料的性能主要取决于银粒子的大小和形貌,因此制备高性能纳米银的关键是精确控制颗粒尺寸和形貌。作为一种合成纳米材料的新方法,微波辅助法与传统方法相比,具有巨大的优点,如微波的穿透能力比较强,加热更均匀,清洁高效、污染小。本课题主要采用微波辅助合成法,在微波辅助加热条件下,以硝酸银(AgNO3)为银源,乙二醇(EG)作为溶剂和还原剂,聚乙烯吡咯烷酮(PVP)作为表面活性剂,氯化钠(NaCl)或者硫化钠(Na2S)作为形貌控制剂,通过调整反应条件及反应物配比,并运用紫外-可见吸收光谱仪(UV-Vis)、X射线衍射仪(XRD)、透射电镜(TEM)和场发射扫描电镜(SEM)等仪器观察分析产物的形状与尺寸,探讨影响纳米银形貌和粒径大小的因素。全文主要内容包括以下三部分:(1)纳米银线的制备:采用微波辅助加热,以NaC l为形貌控制剂,探讨反应时间、温度、反应物配比、微波功率和氯化钠浓度等因素对纳米银线形貌和尺寸的影响。最终取得最佳的制备工艺:微波功率为300 W,AgNO3与PVP质量比为1:2.5,NaCl浓度为2.5 mM,反应时间4 min,温度控制为190oC。在此基础上合成了直径约40 nm、长度约15μm、形貌均一的高纯纳米银线,并进一步探讨纳米银线的生长机制。(2)纳米银立方块的制备:利用微波法,以Na2S作为形貌控制剂,通过改变Na2S浓度、PVP与硝酸银的质量比、反应温度和时间等条件得出银立方块的最佳生成条件:微波功率为300 W,PVP质量为0.68 g,AgNO3质量为0.17 g,Na2S浓度为375mM,反应时间4 min,反应温度180oC。并且成功制备出完整形貌的纳米银立方块,并进一步探讨了纳米银立方块的生长机理。(3)高浓度球形纳米银颗粒的制备:利用多元醇的弱还原性和微波辅助法的高反应效率,将多元醇法和微波辅助法结合制备纳米银颗粒,详细分析了反应时间、温度、反应物配比和硫化钠浓度等条件对产物的影响并在10 min内制备出了高浓度(0.5M)、小粒径(10 nm)、窄粒径分布(2-6 nm)的纳米银颗粒。
[Abstract]:Due to their unique properties, such as small size effect, surface effect and quantum tunneling effect, silver nanocrystalline materials have been widely used in the fields of catalysis, consumer electronics, medicine and so on. The properties of silver nanoparticles mainly depend on the size and morphology of silver particles, so the key to the preparation of high performance silver nanoparticles is to accurately control the size and morphology of silver nanoparticles. As a new method of synthesizing nanomaterials, microwave assisted method has great advantages compared with traditional methods, such as strong penetrating ability of microwave, more uniform heating, clean and efficient, and less pollution. In this paper, microwave-assisted synthesis was carried out under the condition of microwave-assisted heating, silver nitrate (AgNO3) as silver source, ethylene glycol (EG) as solvent and reductant, polyvinylpyrrolidone (PVP) as surfactant, and polyvinylpyrrolidone (PVP) as surfactant. Sodium chloride (NaCl) or sodium sulfide (Na2S) were used as morphology control agents. By adjusting reaction conditions and reactants ratio, UV-Vis absorption spectrometer (XRD),) was used. The shape and size of the products were observed by transmission electron microscope (TEM) and field emission scanning electron microscopy (SEM), and the factors affecting the morphology and particle size of silver nanoparticles were discussed. The main contents of this paper are as follows: (1) preparation of nanocrystalline silver wire: microwave assisted heating, NaC l as morphology control agent, reaction time, temperature, reactant ratio, etc. Effects of microwave power and concentration of sodium chloride on the morphology and size of silver nanowires. The optimal preparation process was obtained as follows: microwave power of 300W Agno _ 3 to PVP was 1: 2.5 mM, reaction time was 2.5 mM, reaction time was 4 min, and the temperature was 190oC. On this basis, high purity silver nanowires with a diameter of about 40 nm, about 15 渭 m in length and uniform morphology were synthesized, and the growth mechanism of nanocrystalline silver nanowires was further discussed. (2) preparation of silver nanocrystalline cubes: Na2S was used as the morphology control agent by microwave method. By changing the concentration of Na2S, the mass ratio of PVP to silver nitrate, the reaction temperature and time, the optimum conditions for the formation of silver cubic block were obtained: microwave power of 300WN PVP, mass of 0.68g / Agno _ 3, mass of 0.17 g / na _ 2S, concentration of 375mM, etc. The reaction temperature was 180oC at 4 min,. And successfully prepared nano-silver square with complete morphology, The growth mechanism of nanocrystalline silver cube was also discussed. (3) preparation of high concentration spherical silver nanoparticles: the weak reduction of polyols and the high reaction efficiency of microwave-assisted method. The effects of reaction time, temperature, ratio of reactants and concentration of sodium sulfide on the preparation of silver nanoparticles were analyzed in detail, and a high concentration (0.5 M) of silver nanoparticles was prepared in 10 min. Silver nanoparticles with small particle size (10 nm), narrow particle size distribution (2-6 nm).
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;O614.122

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