硫醇制备金纳米粒子的反应机理及DNA金纳米粒子自组装的分子动力学模拟

发布时间：2018-01-14 18:03

本文关键词：硫醇制备金纳米粒子的反应机理及DNA金纳米粒子自组装的分子动力学模拟　出处：《南京大学》2015年博士论文　论文类型：学位论文

【摘要】：纳米技术和纳米材料,尤其是金属纳米材料,自诞生以来所取得的巨大成就和对科学及社会各个领域的影响和渗透一直引人注目。金纳米粒子因其特殊的化学性能以及极好的生物相容性在纳米材料和生物医学领域具有广泛的应用。因此,金纳米粒子的制备及自组装,尤其是DNA修饰的金纳米粒子的自组装是当前研究的热点。1. Brust-Schiffrin两相合成法是应用很广泛的制备油溶性金纳米粒子的一种方法。对于此反应的过程,虽然已有大量的实验方面的研究,但其反应机理一直没有明确定论。主要原因是此反应过程中的产物种类较多,而且还有聚合物产生,给实验测定带来一定的困难。因此,通过计算机技术研究其微观反应机理是非常有必要的。我们用密度泛函理论(DFT)系统地研究了硫醇与金氯酸反应制备金纳米粒子的反应过程,同时分析了剂极性以及铵盐的存在对反应机理的影响。研究结果显示：两当量的硫醇与[AuCl4-]发生反应时,[AuCl4-]会通过[Au(Cl)3(SR)]-和[Au(Cl)2(SR)2]-两种中间体被还原为Au(I)复合物,并得到副产物RSSR。当加入第三当量的硫醇时,我们得到了反应前躯体[Cl…AuCl(HSR)],其构型会随着溶剂极性的变化而发生改变,从而导致不同的反应路径。当溶剂极性很小时,[Cl…AuCl(HS R)]中的氯和金形成配位共价键,很难解离,因而不能进一步发生反应；在极性较高的溶剂中,[Cl…AuCl(HSR)]中的氯离子会发生解离生成[AuCl(SR)-]进而发生聚合反应生成[Au(Ⅰ)SR]n.。此外,BS两相合成法中铵盐的存在能够降低反应的能垒和总的反应能,从而促进反应的发生。铵盐的存在还会阻碍[Au(Ⅰ)SR]n聚合物的生成,因此BS两相合成法制备金纳米粒子过程中不会有白色聚合物沉淀产生。2.1996年,DNA修饰的金纳米粒子的自组装被首次报道后,DNA修饰的金纳米粒子(DNA-AuNP)就一直受到广泛关注。DNA-AuNP可作为一种“可控的原子当量”(programmable atom equivalent, PAE),用来合成各种具有特殊性质以及高对称性晶格结构的材料。目前,研究者们一方面致力于合成各种类型的晶格结构；另一方面则致力于研究DNA-AuNP自组装结晶过程中的基本规律,从而为以后的DNA-AuNP自组装结晶过程的设计提供依据。例如Mirkin等人通过考查组分、尺寸比例以及晶格对称性等因素总结了一系列规则来预测热力学稳定的晶格结构。但形成晶格结构还依赖于其它一些因素,例如温度以及DNA互补链接链的长度等影响动力学过程的因素。最新研究显示,DNA的成键性质对DNA-AuNP的自组装结晶过程对于起着决定作用。而形成晶格结构需要满足两个条件：一是足够的互补杂化率,即PH值不能太低；二是DNA键随热涨落比较容易断裂,即DNA的成键寿命,fH不能太长。这些细节很难在实验中得到,而理论模拟可以解决这些问题。我们用分子动力学方法(MD)模拟了DNA-AuNP体系的自组装动力学过程并研究了各种因素对DNA成键性质的影响,从而得到影响其结晶过程的因素。模拟结果显示：温度、DNA链数目(DNA链密度)以及互补链长度对DNA的成键性质都有明显的影响,继而影响晶格结构的形成。我们发现DNA的成键百分率随温度的升高而降低,其主要原因是随温度的升高DNA的断键速率加快。因此在一定温度范围内才有利于晶格结构的形成。我们还发现DNA的成键百分率随链数目的增加而增大,但当DNA覆盖度接近饱和时DNA的成键百分率会降低。从整体看,DNA链数目越多越有利于晶格结构的形成。此外,DNA互补链长增加会增加DNA的成键寿命,从而不利于晶格结构的形成。3. 随着DNA-AuNP自组装技术的不断发展以及一系列自组装规律的发现,实验上已经得到了许多不同种类的晶格。理论上也证实了实验中得到的一些晶格结构,而且也预测了一些实验中未得到的晶格结构。目前,分子动力学方法模拟DNA-AuNP自组装过程己有了很大进展,一些不同种类的晶格结构已经通过MD模拟得到,验证了实验结果。但是,大多数的MD方法研究的是A-B互补体系,对A-A自身互补体系的研究很少。本章中,我们对A-A和A-B的自组装结晶过程都进行了模拟研究。对于A-A可自身互补的体系,虽然DNA链数目n大于20时可形成规则结构(类似SC),但只有链数目大于35时才可能形成FCC晶格结构。对于A-B体系,纳米粒子则首先形成先形成D-BCC结构。我们的模拟结果与实验以及其他理论结果都吻合。此外,我们发现,温度退火可以加速晶格结构的形成。
[Abstract]:Nanotechnology and nano materials, especially metal nano materials, effects of great achievements since the birth of various scientific and social fields and has been in the limelight and penetration of gold nanoparticles. Because of its special chemical properties and excellent biocompatibility has been widely used in nano material and biomedicine. Therefore, gold nanoparticles preparation and self assembly, especially the self-assembly of DNA modified gold nanoparticles is the hotspot of.1. Brust-Schiffrin phase synthesis method of the present study is a method for preparing oil soluble gold nanoparticles are widely used. For this reaction, although there are a large number of experimental studies, but the reaction mechanism has been no clear conclusion. The main reason is that the more types of products in the reaction process, and the polymer produced, to bring some difficulties for the experimental determination. And through computer technology, study the micro reaction mechanism is very necessary. We use density functional theory (DFT) system to study the reaction process of mercaptans and gold chlorate reaction preparation of gold nanoparticles, and analyzed the influence of agent in the presence of polarity and ammonium salt on the reaction mechanism. Research results show that the thiol and [AuCl4-] two equivalent reaction, [AuCl4-] through [Au (Cl) 3 (SR) - and [Au (Cl) 2 (SR) 2]- two intermediates was reduced to Au (I) complexes, and by-product RSSR. when mercaptan added third equivalent, we obtained the precursor [Cl... AuCl (HSR)], its configuration changes with the change in the polarity of the solvent, resulting in a different reaction path. When the polarity of the solvent is very small, [Cl... The chloride and gold in AuCl (HS R) form a coordination covalent bond, which is difficult to dissociate and thus can not be further reacted; in a highly highly polar solvent, [Cl... AuCl (HSR)] in the chloride ion dissociation happens to generate [AuCl (SR) - then the polymerization reaction of [Au (I) SR]n.. Addition, BS ammonium synthesis in two phase can reduce the reaction barrier and total reaction can occur, so as to promote the reaction. The presence of ammonium will hinder the [Au (I) to generate SR]n polymer, therefore BS two-phase synthesis with white polymer.2.1996 years will not precipitate gold nanoparticles in the process of DNA modified gold nanoparticles self-assembly was reported for the first time, DNA modified gold nanoparticles (DNA-AuNP) have been widely concerned by.DNA-AuNP can be used as a "controllable atomic equivalent" (programmable atom equivalent, PAE), is used to synthesize a variety of special properties and materials of high symmetry lattice structure. At present, the researchers on the one hand is dedicated to the synthesis of various types of lattice structure; on the other hand, Dedicated to the study of self assembled DNA-AuNP basic rules in the process of crystallization, provide the basis for the future design of self assembling DNA-AuNP crystallization process. For example, Mirkin et al. By examining the components, the size of the lattice symmetry and other factors summarized a series of rules to predict the lattice structure of thermodynamic stability. But also depends on the formation of lattice structure some other factors, such as temperature and DNA affect the length of the chain link complementary factors such as dynamic process. The latest research shows that the DNA bonding properties of DNA-AuNP self-assembled crystallization process plays a decisive role in the formation of lattice structure. And the need to meet two conditions: one is the hybrid complementary enough rate, pH not too low; the two is the DNA key with the thermal fluctuation is easy to break down, the key of life DNA, fH can not be too long. These details are difficult to obtain in the experiment, and the simulation can be solved These problems. We use molecular dynamics method (MD) simulation system DNA-AuNP self-assembly dynamics process and studied the various factors which affect the bond properties of DNA, so as to get the factors affecting the crystallization process. The simulation results show that the temperature of DNA, the number of chain (DNA chain density) and complementary chain length of DNA into have the obvious influence of key properties, and then influence the formation of lattice structure. We found that the DNA bonding percentage decreases with the increase of temperature, the main reason is that with the increase of the temperature of the DNA bond breaking rate. Therefore it is conducive to the formation of lattice structure in a certain temperature range. We also found that the increase of DNA the percentage of the number of bonding with the chain increases, but when the DNA coverage is close to saturation DNA bonding percentage will be reduced. On the whole, DNA chain number more conducive to the formation of lattice structure. In addition, DNA complementary chain length The key to increase the life of DNA will increase, which is not conducive to the formation of.3. lattice structure with the continuous development of DNA-AuNP self assembly technology and a series of self assembly found the law of experiment has been many different kinds of lattice theory. Also confirmed the experiment obtained in a lattice structure, but also predict the lattice the structure has not been some experiments. At present, the molecular dynamics simulation of DNA-AuNP self-assembly process have made great progress, some different kinds of lattice structure has been simulated by MD, to verify the experimental results. However, most of the research of MD method is A-B complementary system, little research on A-A self complementary system. In this chapter, we have for A-A and A-B self-assembled crystallization kinetics was studied. The A-A self complementary system, although the DNA chain number n is greater than 20 can form a regular structure (class Like SC), but only the chain number is greater than the formation of FCC lattice structure may be 35. The A-B system is first formed nanoparticles to form a D-BCC structure. Our simulation results with the experimental and other theoretical results. In addition, we found that the annealing temperature can accelerate the formation of the lattice structure.

【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1;O614.123

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