基于金纳米棒结构的合成及其等离激元特性研究

发布时间：2018-04-18 04:26

本文选题：金纳米棒 + 局域表面等离激元共振　；参考：《南京航空航天大学》2015年博士论文

【摘要】：贵金属纳米材料(尤其金和银)因其具有良好的物性及其表现出的独特光学特性—局域表面等离激元共振现象(LSPR),成为纳米科学领域中的一个热门课题。在众多贵金属纳米结构中,金纳米棒(GNRs)因其表现出依赖于形貌的各向异性且可调的SPR特性,在生命科学、光电技术等领域受到了广泛关注。本论文围绕金纳米棒的合成、自组装、表面包覆等课题开展实验和理论研究,并借助FDTD数值计算分析影响SPR的诸多因素,为基于金纳米棒的相关理论与应用研究奠定基础。本论文的具体研究内容和研究成果如下:1.基于晶种生长法,合成出纵向等离激元共振峰(SPRL)可在近红外波段可调的不同长径比的金纳米棒。研究入射光波长和环境温度对金纳米棒生长的影响。对比研究了基于Gan理论和时域有限差分法(FDTD)下,金纳米棒的SPRL峰与其长径比和背景介质折射率间的关系。利用FDTD方法研究光源的偏振化方向和金纳米棒的端面形貌对SPRL的影响,结果表明:偏振化方向主要影响SPRL峰的强度,并与偏振化方向成余弦关系,而金纳米棒端面形貌的变化不但会引起SPRL峰强度的变化,还会引起SPRL峰的移动。2.利用HS-PEG-SH、CYS和MPA作为连接分子,诱使金纳米棒自组装成端对端和肩并肩的有序结构,并结合实验结果分析了自组装机理。FDTD数值计算结果表明:自组装体中单体的个数、棒间的间距和夹角都会对SPR耦合产生影响。随着自组装体中单体数目的增多,不同的自组装形式会引起SPRL峰发生红移或蓝移现象,其相对移动量与单体的数目均成指数关系。随着间距的增大,棒间的耦合效应会越来越弱,最终移至单棒的SPRL峰附近。而棒间夹角的变化只是影响了峰的强度,没有影响SPR的位置,并且由于对称性破缺会产生的高能峰与低能峰,二者强度间的比值随夹角的增大成指数关系衰减。3.利用溶胶—凝胶法合成出具有不同Si O2壳层厚度的GNR@Si O2核-壳复合纳米结构,研究了TEOS在碱性条件下的水解机理。利用808nm半导体连续激光器研究了金纳米棒和GNR@Si O2的热稳定性,实验表明:GNR@Si O2的热稳定性明显要高于金纳米棒。对于金纳米棒,随着辐射激光功率的增大,其表面的CTAB开始脱落,裸露的表面发生熔化,最终形成稳定性的球状结构。而对于GNR@Si O2核-壳结构,随着辐照功率的增大,金纳米棒表面的Si O2壳层会先发生断裂,并使得GNR@Si O2结构遭到破坏。4.实验上成功制备出具有良好水溶性和热稳定性的金纳米棒多聚体核-壳复合纳米结构,核是具有端对端和肩并肩结构的金纳米棒组装体系。结合FDTD数值计算结果表明:介孔Si O2很好地保持了核颗粒的光学响应,且SPRL峰的位置与核内金纳米棒的个数也成指数递增或递减关系。此外,多聚体核-壳结构也为进一步定量研究多聚体间的局域场增强效应创造条件。
[Abstract]:Noble metal nanomaterials (especially gold and silver) have become a hot topic in the field of nanoscience because of their good physical properties and their unique optical properties such as local surface isoexciton resonance phenomenon.Among many noble metal nanostructures, gold nanorods have attracted wide attention in life sciences, optoelectronic technology and other fields because of their morphologically dependent anisotropic and adjustable SPR properties.This thesis focuses on the synthesis, self-assembly and surface coating of gold nanorods, and analyzes the factors affecting SPR by FDTD numerical calculation, which lays a foundation for the theoretical and practical research based on gold nanorods.The specific contents and results of this thesis are as follows: 1.Based on the method of seed growth, gold nanorods with different aspect ratios, which can be adjusted in near infrared band, have been synthesized.The effects of incident wavelength and ambient temperature on the growth of gold nanorods were studied.The relationship between the SPRL peak of gold nanorods and the aspect ratio of gold nanorods and the refractive index of background medium under Gan theory and finite-difference time-domain method (FDTD) is studied.The effect of polarization direction of light source and the morphology of gold nanorods on SPRL is studied by FDTD method. The results show that the polarization direction mainly affects the intensity of SPRL peak and has a cosine relationship with the polarization direction.The change of the end morphology of gold nanorods will not only change the intensity of SPRL peak, but also cause the shift of SPRL peak. 2.The self-assembly of gold nanorods was induced by using HS-PEG-SHG CYS and MPA as connecting molecules to form an ordered structure of end-to-end and side-by-side. Combined with the experimental results, the self-assembled mechanism. FDTD numerical calculation results showed that the number of monomers in the self-assembled body was determined.The distance between rods and the angle between rods will affect the SPR coupling.With the increase of the number of monomers in the self-assembly, the red shift or blue shift of the SPRL peak will occur in different self-assembly forms, and the relative mobility is exponentially related to the number of monomers.With the increase of the spacing, the coupling effect between the rods becomes weaker and weaker, and finally moves to the SPRL peak of the single rod.However, the change of the angle between rods only affects the intensity of the peak, but not the position of the SPR, and the ratio of the intensity between the high energy peak and the low energy peak due to symmetry breaking decreases exponentially with the increase of the angle.The GNR@Si O 2 core-shell composite nanostructures with different Sio 2 shell thickness were synthesized by sol-gel method. The hydrolysis mechanism of TEOS under alkaline conditions was studied.The thermal stability of gold nanorods and GNR@Si O 2 have been studied by 808nm semiconductor continuous laser. The experimental results show that the thermal stability of 808nm nanorods is obviously higher than that of gold nanorods.For gold nanorods, with the increase of laser power, the surface CTAB of gold nanorods begins to fall off, the exposed surface melts, and finally a stable spherical structure is formed.However, for the core-shell structure of GNR@Si O 2, with the increase of irradiation power, the Sio 2 shell on the surface of gold nanorods will first break, and the structure of GNR@Si O 2 will be destroyed. 4.The gold nanorods with good water-solubility and thermal stability were successfully prepared. The core is a gold nanorod assembly system with end-to-end and side-by-side structure.The results of FDTD numerical calculation show that mesoporous Sio _ 2 keeps the optical response of nuclear particles very well, and the position of SPRL peak is exponentially increasing or decreasing with the number of gold nanorods in the nucleus.In addition, the core-shell structure of the polymer also creates conditions for further quantitative study of the local field enhancement effect between the polymers.
【学位授予单位】：南京航空航天大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：O614.123;TB383.1

【相似文献】