【作者】 申素芬；

【导师】 赵华文； 黄承志；

【作者基本信息】 西南大学 ， 分析化学， 2010， 硕士

【摘要】 近年,金属纳米材料由于其独特的光电性质而倍受关注。一方面它们广泛应用于如DNA、氨基酸、蛋白质、金属离子等各种检测；另一方面金属纳米材料可以组装成一维、二维或三维结构,组装后的纳米材料表现出特有的集体性质。本文探讨了高离子强度下卡托普利与金纳米棒的分子组装；利用球形金纳米颗粒的网状组装体实现对三聚氰胺的检测；卤素单质对银纳米颗粒形态的影响及壳核结构的银纳米颗粒形成等四方面问题。主要内容如下：1.利用药物卡托普利（Cap）实现了棒状金纳米颗粒在高离子强度溶液中的组装。Cap分子一端为巯基,另一端为羧基。由于Au-S键很容易形成,所以Cap很容易修饰到金纳米棒的表面,同时由于羧基之间的氢键作用使得Cap分子两两结合在一起。正是Cap分子这种结构特殊性为金纳米棒组装奠定了基础。研究发现,通过调节溶液的离子强度,可以使金纳水棒形成不同形态的组装体。低离子强度时,NaCl能减弱CTAB包被的金棒之间的静电斥力,导致金棒肩并肩组装；高离子强度时,大量的Cl-在金棒表面形成静电双分子层,使金棒逐渐分散,从而实现了金棒头碰头与肩并肩结构共存的组装体。这种高离子强度下金棒与卡托普利的分子组装也为其在化学及生物传感器方面的应用奠定了基础。2.三聚氰胺诱导金纳米颗粒的网状组装。在碱性条件下制备了巯基乙酸包被的球形金纳米颗粒,所制备的金纳米颗粒表面存在-COO-,同时调节三聚氰胺溶液的酸度,使得其分子中的-NH2以-NH3+的形式存在,因而两者混合时-COO^-与-NH₃⁺之间发生静电作用,金纳米颗粒组装成网状结构,溶液颜色逐渐由红色变为蓝色。据此,本文建立了一种三聚氰胺的色度分析方法。该方法操作简单、快速,直观,成本低,用于检测合成样与实际样,结果均与权威机构报道数据一致。3.探讨了卤素对柠檬酸根包被的银纳米颗粒的形态影响。以紫外可见吸收光谱、SEM电镜等作为表征手段,证实在室温条件下,碘单质能够使银纳米颗粒发生强烈的融合作用,破坏其原有球形结构,同时生成碘化银。相比之下,溴单质无此现象,它只能引起银纳米颗粒聚集,但不改变其原有形态。进一步发现,向柠檬酸根包被的银纳米颗粒溶液中同时加入Cu2+与Br-,银纳米颗粒的粒径会明显增大,并仍然呈现良好的分散性。随着Cu2+与Br-量的增加,银纳米颗粒的吸收强度逐渐降低,且吸收峰的位置先红移后蓝移,最后在长波长处（约620nm）出现一个新峰,并在360nm形成一个等色点。通过紫外可见吸收光谱、SEM电镜、能谱分析等表征手段,证明溶液中的Cu2+与Br可能形成了某种络合物。该络合物覆盖在原有银纳米颗粒表面形成了一种新壳核结构。更多还原

【Abstract】 Recently, metal nanoparticles have attracted great attention due to the unique optical and electric properties, and thus they can be widely exploited to detect some analytes such as DNA, amino acid, protein, metal ion and so on on one hand, and can assemble into one-, two-, or three-dimensional structures on the other, which can offer the unique collective properties of assembly structures.In this thesis, investigations on the assembly of gold nanorods in high ionic strength solutions, colorimetric assay of melamine have been made on the basis of the network structrue of gold nanoparticles, the morphological change of Ag nanoparticles induced by halogen and the formation of core-shell structure of Ag nanoparticles. The main contents are as follow:1.Assemblies of gold nanorods (Au-NRs) induced by captopril (Cap) in high ionic strength solutions. Captopril molecule has is a thiol group and a carboxylic group on the each side, and thus can bond to the surface of Au-NRs on one hand because of the easily formed Au-S covalent bond, and are preferable to combine with each other through cooperative hydrogen bond with its carboxylic groups on the other, which offer the foundation for introducing the assembly of Au-NRs. Furthermore, it was found that the assembly structures could be formed only in the presence of both Cap and NaCl.In the medium of low concentration of NaCl, Au-NRs can form side-by-side structures because NaCl can neutralize the electrostatic repulsion among CTAB-capped gold nanoparticles.In high concentration of NaCl, on the other hand, abundant Cl- is present around the surface of Au-NRs forming an electronic double layer, which keeps Au-NRs well dispersed. In such case, Au-NRs can realize the end-to-end assembly. At the same time, several Au-NRs can form the side-by-side assembly because Cl" can neutralize the electrostatic repulsion among Au-NRs to some extent, so the assembly of Au-NRs containing both end-to-end and side-by-side structures is formed. This assembly method will be of importance in chemical and biological sensing.2. Network assembly of gold nanoparticles coused by melamine. Thioglycolic-acid-modified gold nanoparticles (Au-NPs) were synthesized under alkaline condition, so most carboxyl groups are negatively charged.Before the interaction, HCl was used to modulate the acidity of melamine, making sure that amino groups are mainly positively charged.When mixed, electrostatic interaction occured between modified Au-NPs and melamine,resulting in the network assembly of Au-NPs. At the same time, the color of mixed solution changed from red to blue.Upon this,a colorimetric method of detecting melamine is developed.This method is simple,fast, intuitionistic and low-cost.Employing it to detect melamine in milk powder, the analytical result is satisfying, so this colorimetric assay of melamine will be promising and worth being developed.3.We investigated the morphological change of citrate-capped Ag nanoparticles (Ag-NPs) induced by halogen. From the results of UV-vis absorption spectra and SEM images, it is concluded that at room temperature, iodine could fuse Ag nanoparticles, and produce AgI.At the same condition, bromine can not fuse Ag nanoparticles, but only induce the aggregation of Ag nanoparticles.Besides, we also found that the diameter of citrate-capped Ag nanoparticles (Ag-NPs) enlarges obviously after adding Cu2+ and Br", and the whole Ag-NPs still keep well dispersed. Increasing the concentration of Cu2+ and Br-, the absorption intensity gradually decreases, and the absorption peak red shifts firstly, then blue shifts.Finally a new characteristic absorption appears at longer wavelengths(～620 nm).What is more interesting is that all the absorption spectra intersect at an isosbestic point (λ.≈360 nm, A≈0.270) perfectively. UV-vis absorption spectra, SEM images and energy dispersive spectrdmeter were employed in this study, and we speculate that Cu2+ and Br- may form some complex compound, covering the surface of Ag-NPs to form a new core-shell structure nanoparticles.更多还原