本文關鍵詞：硫醇制備金納米粒子的反應機理及DNA金納米粒子自組裝的分子動力學模擬　出處：《南京大學》2015年博士論文　論文類型：學位論文

  更多相關文章： 分子動力學(MD) 金納米粒子 DNA修飾 硫醇修飾 自組裝 結晶 Brust-Schiffrin兩相合成 密度泛函(DFT)

【摘要】：納米技術和納米材料,尤其是金屬納米材料,自誕生以來所取得的巨大成就和對科學及社會各個領域的影響和滲透一直引人注目。金納米粒子因其特殊的化學性能以及極好的生物相容性在納米材料和生物醫(yī)學領域具有廣泛的應用。因此,金納米粒子的制備及自組裝,尤其是DNA修飾的金納米粒子的自組裝是當前研究的熱點。1. Brust-Schiffrin兩相合成法是應用很廣泛的制備油溶性金納米粒子的一種方法。對于此反應的過程,雖然已有大量的實驗方面的研究,但其反應機理一直沒有明確定論。主要原因是此反應過程中的產物種類較多,而且還有聚合物產生,給實驗測定帶來一定的困難。因此,通過計算機技術研究其微觀反應機理是非常有必要的。我們用密度泛函理論(DFT)系統(tǒng)地研究了硫醇與金氯酸反應制備金納米粒子的反應過程,同時分析了劑極性以及銨鹽的存在對反應機理的影響。研究結果顯示：兩當量的硫醇與[AuCl4-]發(fā)生反應時,[AuCl4-]會通過[Au(Cl)3(SR)]-和[Au(Cl)2(SR)2]-兩種中間體被還原為Au(I)復合物,并得到副產物RSSR。當加入第三當量的硫醇時,我們得到了反應前軀體[Cl…AuCl(HSR)],其構型會隨著溶劑極性的變化而發(fā)生改變,從而導致不同的反應路徑。當溶劑極性很小時,[Cl…AuCl(HS R)]中的氯和金形成配位共價鍵,很難解離,因而不能進一步發(fā)生反應；在極性較高的溶劑中,[Cl…AuCl(HSR)]中的氯離子會發(fā)生解離生成[AuCl(SR)-]進而發(fā)生聚合反應生成[Au(Ⅰ)SR]n.。此外,BS兩相合成法中銨鹽的存在能夠降低反應的能壘和總的反應能,從而促進反應的發(fā)生。銨鹽的存在還會阻礙[Au(Ⅰ)SR]n聚合物的生成,因此BS兩相合成法制備金納米粒子過程中不會有白色聚合物沉淀產生。2.1996年,DNA修飾的金納米粒子的自組裝被首次報道后,DNA修飾的金納米粒子(DNA-AuNP)就一直受到廣泛關注。DNA-AuNP可作為一種“可控的原子當量”(programmable atom equivalent, PAE),用來合成各種具有特殊性質以及高對稱性晶格結構的材料。目前,研究者們一方面致力于合成各種類型的晶格結構；另一方面則致力于研究DNA-AuNP自組裝結晶過程中的基本規(guī)律,從而為以后的DNA-AuNP自組裝結晶過程的設計提供依據。例如Mirkin等人通過考查組分、尺寸比例以及晶格對稱性等因素總結了一系列規(guī)則來預測熱力學穩(wěn)定的晶格結構。但形成晶格結構還依賴于其它一些因素,例如溫度以及DNA互補鏈接鏈的長度等影響動力學過程的因素。最新研究顯示,DNA的成鍵性質對DNA-AuNP的自組裝結晶過程對于起著決定作用。而形成晶格結構需要滿足兩個條件：一是足夠的互補雜化率,即PH值不能太低；二是DNA鍵隨熱漲落比較容易斷裂,即DNA的成鍵壽命,fH不能太長。這些細節(jié)很難在實驗中得到,而理論模擬可以解決這些問題。我們用分子動力學方法(MD)模擬了DNA-AuNP體系的自組裝動力學過程并研究了各種因素對DNA成鍵性質的影響,從而得到影響其結晶過程的因素。模擬結果顯示：溫度、DNA鏈數目(DNA鏈密度)以及互補鏈長度對DNA的成鍵性質都有明顯的影響,繼而影響晶格結構的形成。我們發(fā)現(xiàn)DNA的成鍵百分率隨溫度的升高而降低,其主要原因是隨溫度的升高DNA的斷鍵速率加快。因此在一定溫度范圍內才有利于晶格結構的形成。我們還發(fā)現(xiàn)DNA的成鍵百分率隨鏈數目的增加而增大,但當DNA覆蓋度接近飽和時DNA的成鍵百分率會降低。從整體看,DNA鏈數目越多越有利于晶格結構的形成。此外,DNA互補鏈長增加會增加DNA的成鍵壽命,從而不利于晶格結構的形成。3. 隨著DNA-AuNP自組裝技術的不斷發(fā)展以及一系列自組裝規(guī)律的發(fā)現(xiàn),實驗上已經得到了許多不同種類的晶格。理論上也證實了實驗中得到的一些晶格結構,而且也預測了一些實驗中未得到的晶格結構。目前,分子動力學方法模擬DNA-AuNP自組裝過程己有了很大進展,一些不同種類的晶格結構已經通過MD模擬得到,驗證了實驗結果。但是,大多數的MD方法研究的是A-B互補體系,對A-A自身互補體系的研究很少。本章中,我們對A-A和A-B的自組裝結晶過程都進行了模擬研究。對于A-A可自身互補的體系,雖然DNA鏈數目n大于20時可形成規(guī)則結構(類似SC),但只有鏈數目大于35時才可能形成FCC晶格結構。對于A-B體系,納米粒子則首先形成先形成D-BCC結構。我們的模擬結果與實驗以及其他理論結果都吻合。此外,我們發(fā)現(xiàn),溫度退火可以加速晶格結構的形成。
[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.

【學位授予單位】：南京大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TB383.1;O614.123

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