多形貌纳米银的制备及其可控性研究

【作者】 阳素玉；

【导师】 尹荔松；

【作者基本信息】 中南大学 ， 物理学， 2010， 硕士

【摘要】 纳米银材料由于其特殊的物理和化学性质,在催化、光学、电子、表面拉曼增强,生物医药和生物传感器以及许多领域都具有广泛的应用前景。纳米材料这些独特性能与其尺寸、形状密切相关,因而形貌可控地制备纳米材料非常重要。虽然纳米材料的制备方法有很多种,但对于纳米材料的可控制备方面所取得的成果仍然非常有限,因此寻找新的合成方法制备尺寸和形貌可调的银纳米结构具有十分重要的意义和广泛的应用前景。根据目前金属Ag纳米粒子的国内外研究现状,本文通过水热法合成了零维球形纳米银,一维银纳米线,二维花状纳米银自组装结构,表征和分析了合成产物的成分、形貌、结构,提出了上述银纳米结构的生长机理,得到简易的银纳米粒子形貌可控的合成方法。采用水热法,不添加任何还原剂,在表面活性剂聚乙烯吡咯烷酮(PVP)保护下,热分解碳酸银制得纳米银溶胶。通过改变反应温度、反应时间、表面活性剂浓度、种类及反应物浓度等反应条件,利用X射线衍射仪(XRD),扫描电子显微镜(SEM)和电子能谱仪(EDS)分析表明,在反应温度为180℃,反应时间为5小时,AgNO3浓度0.1mol/L, NaHCO3浓度0.05mol/L,PVP为1.7 g的最佳制备工艺条件下,纳米银粒子为球形,粒径大小分布范围窄,单一分散,粒径40 nm左右。采用水热法,在180℃,以葡萄糖为还原剂,聚乙烯吡咯烷酮(PVP)为表面活性剂,Fe3+的刻蚀作用下,反应时间为3小时,合成高产率的长度达几百微米的银纳米线。讨论了反应温度、反应时间、反应物浓度等反应条件对于形成银纳米线的影响,随着Fe3+的增加,银纳米线直径也由90nm增加到300nm。结果表明Fe3+和PVP浓度对于银纳米线尺寸和形貌的调控具有关键作用。由简单的水热法组制备出高产率的花状纳米银自组装结构,这种新颖的纳米结构是在聚乙烯吡咯烷酮(PVP)存在下通过抗坏血酸在150℃,10小时还原生成的。平均粒径大小在1-2微米,由许多纳米棒束自组装而成,显示为面心立方结构并讨论了各反应物浓度因素对于形貌的影响。结果表明,在相对低浓度的PVP有利于合成花状自组装结构,且PVP的浓度改变对于形成组成自组装结构的纳米棒束形貌具有关键作用。与此同时,AgNO3与AsA的浓度和摩尔比对于花状银纳米自组装结构的形成也具有重要影响。这种新颖的纳米结构,可能具有特殊的物理,化学与光电性能。更多还原

【Abstract】 Nanoscaled silver have received considerable attention due to their unique chemical and physical properties, and have widely potential applications in catalyst, optics, electronics, surface-enhanced Raman scattering (SERS), biomedicine, and biological sensing. These peculiar and fascinating properties of nanomaterials strongly depend on the size and the shape of the nanoparticles. Thereby morphology-controlled preparation of nanomaterials is very important and significative. Nowadays a great variety of methods have been used to obtain metal nanostructures, the shape-controllable synthesis is still a challenge for materials researchers, and finding a new synthesis method for the preparation of adjustable size and morphology of the silver nanostruetures has very important significance and broad application prospects. Based on the development of metallic silver nanoparticles in the world, in this paper, we sucsessfuly synthesized zero-dimensional spheric silver nanoparticles, one-dimensional silver nanowires and two-dimensional flower-like silver nanoplate micro-assemblies by hydrothermal route. The obtained silver products were characterized and tested, and the growth mechanism of former silver naostructures was dicussed. this dissertation presents a facile chemical solution-method to prepare silver nanoparticles with various morphologies and obtain novel silver nanostructures.Colloidal silver nanoparticles were prepared by decomposing silver carbonate with hydrothermal method in the presence of polyvinyl pyrrolidone as protecting agents and without any reducing agent. By changing the reaction temperature, time, surfactants concentration, category and the reagents concentration, silver nanoparticles were obtained and investigated by the XRD (X-ray diffraction), SEM (scanning electron microscope) and EDS (energy-dispersive spectroscopy). The optimum preparation conditions was 180℃,5 h, 0.1mol/L AgNO3,0.05mol/L NaHCO3 and 1.7 g PVP(polyvinyl pyrrolidone), and under this condition, the results show that the nanometer silver powder were spherical shape, single dispersion and about 40 nm in particle size with a narrow size distribution.We have prepared large scale silver nanowires with lengths of several hundred micrometers by using glucose as reducing agent, PVP as crystal growth control agent at 180℃for 3 h, and Fe3+ as etching agents under hydrothermal process. The influential factors such as reaction temperature, reaction time, and concentration of the reagents were studied. The diameter of synthesized silver nanowires changed from 90 nm to 300 nm with the increase of Fe3+. The results showed that the concentration of Fe3+ and PVP is the key role for controllable size and morphology for silver nanowires.We demonstrated the fabrication of the novel flower-like silver nanoplate micro-assemblies in high yields by a facile hydrothermal method. This nanostructure was synthesized in the presence of poly (vinyl pyrrolidone) and ascorbic acid at 150℃for 10h. The micro-assemblies with average size of 1-2μm are consisted of several uniform nanorods and show face centered cubic structure. The effects of the concentration of reactants, molar ratio of silver nitrate to ascorbic acid on the formation of the flower-like silver micro-assemblies were also presented. The results suggest that PVP with relative low concentration is favorable to synthesize the flower-like nanoplate micro-assemblies, and the shapes of the consisted particles in the micro-assemblies are largely modified by altering the concentration of PVP. Additionally, the concentrations and the molar ratio of AgNO3 to AsA are significant parameters for the formation of the flower-like silver nanoplate micro-assemblies. This novel silver structure is expected to behave fascinating properties of chemistry, physics and electronics.更多还原