光辐照制备各向同性和各向异性银纳米颗粒及机理分析

发布时间：2019-03-20 08:39

【摘要】：以金、银为代表的贵金属纳米颗粒是现代材料科学、微纳光学、生物光子学等前沿科技领域的研究热点,制备具有不同形貌的贵金属纳米颗粒则是实现纳米颗粒性能调控的一个重要方法。而相对于较稳定的金纳米材料而言,银纳米材料表面形貌控制一直是此领域的难点。在传统化学制备方法中,一方面,难以通过控制晶面生长得到规则球形的银纳米颗粒,另一方面,制备具有良好性能的各向异性银纳米材料条件复杂且苛刻。本文就光辐照法制备各向同性和各向异性银纳米颗粒进行研究,发展出新型光辐照制备与表征方法,探讨并分析了产物形成机制及其表面等离子体特性。首先,利用简单的柠檬酸钠还原法制备了形貌不规则、尺寸分布于80-90 nm的银纳米颗粒,随后使用248 nm准分子激光辐照该纳米颗粒溶胶,制备得到规则球形各向同性颗粒。在使用TEM、SEM、吸收光谱等方式对产物进行表征之后,得到了可靠的制备条件。在形貌的表征中,提出“圆度”来定量描述纳米颗粒接近于规则球形程度。在机理的分析中,采用了改进的“光热-相变”理论对实验的物理过程进行了详细阐述。作为对比,采用汞灯和氙灯两种连续光源分别对不规则形貌银纳米颗粒进行紫外和可见光波段辐照。在不同的实验条件下制备出棒状、三角板状等各向异性银纳米颗粒。在对产物进行性能表征之后,得到了不同形貌纳米颗粒的制备参数。对于纳米颗粒由不规则向各向异性的转变过程,结合实验结果分析其物理机制,提出了“碎裂-连接-生长”的演化模型。此外,分析了脉冲激光和连续光源对银纳米颗粒表面形貌改变的异同,并对以上两部分工作的中的纳米颗粒产物进行表面增强拉曼散射(SERS)性能表征。实验结果表明,规则球形和各向异性银纳米颗粒均有优异的SERS活性,对探针分子的不同基团有选择性吸附和增强效应,在痕量物质检测领域具有广阔的应用前景。
[Abstract]:Precious metal nanoparticles, represented by gold and silver, are the focus of research in modern material science, micro / nano optics, biophotonics and other cutting-edge science and technology fields. The preparation of precious metal nanoparticles with different morphologies is an important method to control the properties of nano-particles. Compared with the stable gold nanomaterials, the surface morphology control of silver nanomaterials has always been a difficulty in this field. In traditional chemical preparation methods, on the one hand, it is difficult to obtain regular spherical silver nanoparticles by controlling the growth of crystal faces. On the other hand, the conditions for preparing anisotropic silver nanoparticles with good properties are complex and demanding. In this paper, the preparation of isotropic and anisotropic silver nanoparticles by light irradiation has been studied. A new method of preparation and characterization of silver nanoparticles by light irradiation has been developed. The formation mechanism and surface plasma characteristics of the products have been discussed and analyzed. Firstly, silver nanoparticles with irregular morphology and size distribution of 80 ~ 90 nm were prepared by a simple sodium citrate reduction method. Then regular spherical isotropic particles were prepared by irradiation of the nanoparticles with 248nm excimer laser. After the product was characterized by TEM,SEM, absorption spectrum and other methods, reliable preparation conditions were obtained. In the characterization of morphology, "roundness" is proposed to quantitatively describe the degree of sphericity of nanoparticles close to that of regular sphericity. In the analysis of the mechanism, the physical process of the experiment is described in detail by using the improved "photothermal-phase transition" theory. As a contrast, mercury lamp and xenon lamp were used to irradiate irregularly shaped silver nanoparticles in ultraviolet and visible wavelengths, respectively. Anisotropic silver nanoparticles, such as rod and triangular plate, were prepared under different experimental conditions. After characterization of the products, the preparation parameters of the nanoparticles with different morphologies were obtained. For the transition process from irregular to anisotropic, the physical mechanism of nano-particles is analyzed, and the evolution model of "fragmentation-connection-growth" is put forward. In addition, the similarities and differences between pulsed laser and continuous light source on the surface morphology of silver nanoparticles were analyzed, and the surface enhanced Raman scattering (SERS) properties of the nanoparticles produced in the above two parts of work were characterized by surface enhanced Raman scattering (SERS). The experimental results show that both regular spherical and anisotropic silver nanoparticles have excellent SERS activity, and have selective adsorption and enhancement effects on different groups of probe molecules. Therefore, they have broad application prospects in the field of trace substances detection.
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O614.122;TB383.1

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