金纳米粒子的合成与包覆以及催化性能研究

发布时间：2018-05-05 05:15

本文选题：金纳米粒子 + 二氧化硅　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：贵金属纳米粒子以其优异的特性及多方位的应用成为纳米材料领域的研究热点。金纳米粒子作为贵金属纳米粒子的代表,在传感、生物医疗、催化等领域应用十分广泛,在解决资源匮乏,提高资源利用率问题中,贵金属纳米粒子的优异催化性能起到了举足轻重的作用。本文通过使用紫外可见吸收光谱仪、透射电子显微镜、气体吸附等多种方法,对所得金纳米粒子、全包覆金纳米粒子、半包覆纳米粒子及金银Janus双球纳米粒子的结构、催化性能测试及稳定性进行了系统性研究。采用Frens方法及种子一步生长法合成了水溶性金纳米粒子,并对所得金纳米粒子进行了两种不同材料的包覆,包括通过改进的St?ber方法进行二氧化硅包覆及水热合成法实现的碳包覆。研究了包覆物壳层厚度相同、金纳米粒子浓度相等的条件下,两种不同包覆对金纳米粒子催化性能的影响。同时,还研究了不同厚度的碳壳包覆对金纳米粒子催化性能和稳定性的影响。结果表明,二氧化硅包金纳米粒子的催化性能比相同壳层厚度的碳包金纳米粒子的催化性能更优异,前者催化反应时间为后者的三分之一,反应速率常数为后者的二十倍。为了深入理解其催化性能差异,利用SF法对碳和二氧化硅包覆物进行了孔隙分析,结果显示碳的孔径只有二氧化硅的三分之一。合成了两半球分别被不同分子包覆的阴阳型金纳米粒子,并通过二氧化硅在金球单侧的水解,获得了二氧化硅半包覆金纳米粒子,并研究了所得粒子的催化性能,以及紫外灯照射、乙醇清洗等后处理对其催化性能的影响。结果表明,与二氧化硅全包覆的金纳米粒子相比,该种半包覆纳米粒子在催化反应过程中的稳定性没有降低,但催化性能仅小幅提高。而经过后处理之后,在相同条件下,其平均催化性能可大大提高,且催化反应不像全包覆的金纳米粒子那样存在停滞时间。此外,还研究了这种后处理的二氧化硅半包金纳米粒子作为催化剂的可循环利用性和稳定性。结果表明,其催化反应时间基本不变、吸光光谱与反应前相近。此外,合成了强弱配体共包覆的阴阳型金纳米粒子,并以其弱配体包覆的半球为成核位置还原银盐,高产率地获得了均一的金-银Janus双球结构纳米粒子。系统探究了Janus双球结构纳米粒子的光学性能和催化性能。结果表明,其紫外可见吸收光谱中,除了对应于金、银纳米粒子的等离子体共振吸收峰外,还存在明显的单独对应于金银Janus双球结构的第三个吸收峰。同时,研究了金银Janus双球纳米粒子的催化性能,并与金纳米粒子进行了对比。结果表明,Janus双球结构纳米粒子的催化性能可以大幅度提高,但是在催化反应中的稳定性不高。经过表面包覆,有望将其稳定性进一步提升。
[Abstract]:Noble metal nanoparticles have become a hotspot in the field of nanomaterials due to their excellent properties and multi-directional applications. As the representative of noble metal nanoparticles, gold nanoparticles are widely used in sensing, biomedicine, catalysis and other fields. The excellent catalytic performance of noble metal nanoparticles plays an important role. In this paper, the structures of gold nanoparticles, fully coated gold nanoparticles, semi-coated gold nanoparticles and gold and silver Janus double spheres nanoparticles were studied by means of UV-Vis absorption spectrometer, transmission electron microscope and gas adsorption. The catalytic performance and stability were studied systematically. The water-soluble gold nanoparticles were synthesized by Frens method and seed one-step growth method. The gold nanoparticles were coated with two different materials. It includes silica coating by improved St?ber method and carbon coating by hydrothermal synthesis. The effects of two kinds of coating on the catalytic performance of gold nanoparticles were studied under the condition of the same shell thickness and the same concentration of gold nanoparticles. At the same time, the effects of different thickness of carbon shell coating on the catalytic performance and stability of gold nanoparticles were studied. The results show that the catalytic performance of silica coated gold nanoparticles is better than that of carbon coated gold nanoparticles with the same shell thickness. The catalytic time of the former is 1/3 of that of the latter, and the reaction rate constant is 20 times that of the latter. In order to understand the difference of catalytic performance, the pore size of carbon and silica coating was analyzed by SF method. The results showed that the pore size of carbon was only 1/3 of that of silica. The silver nanoparticles coated with different molecules in the two hemispheres were synthesized. The semi-coated gold nanoparticles were obtained by the hydrolysis of silica on one side of the gold sphere. The catalytic properties of the particles were studied. The effect of ultraviolet lamp irradiation, ethanol cleaning and other post-treatment on its catalytic performance. The results showed that the stability of the semi-coated gold nanoparticles was not decreased but the catalytic performance was only slightly improved compared with the fully coated gold nanoparticles. After reprocessing, the average catalytic performance of the catalyst can be greatly improved under the same conditions, and the catalytic reaction does not have the same stagnation time as the fully coated gold nanoparticles. Furthermore, the reusability and stability of the retreated silica semi-clad gold nanoparticles as catalysts were also investigated. The results show that the reaction time is almost unchanged and the absorption spectrum is close to that before the reaction. In addition, the strong and weak ligands cocoated with yin-yang type gold nanoparticles were synthesized, and the silver salts were reduced at the nucleation position of the hemispheres covered by their weak ligands. The uniform gold-silver Janus double sphere structure nanoparticles were obtained in high yield. The optical and catalytic properties of Janus double-sphere nanoparticles were systematically investigated. The results show that in the UV-Vis absorption spectra, there is a third absorption peak corresponding to the structure of gold and silver Janus double spheres, in addition to the plasmon resonance absorption peak of silver nanoparticles and gold nanoparticles. At the same time, the catalytic properties of gold and silver Janus double spheres nanoparticles were studied and compared with gold nanoparticles. The results show that the catalytic performance of Janus double sphere nanoparticles can be greatly improved, but the stability in the catalytic reaction is not high. After surface coating, it is expected to further improve its stability.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;O614.123

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