眾多的奈米金合成法中，以還原法最具代表性，利用四氯金酸為前驅體，檸檬酸三鈉為還原體，還原氯金酸離子並合成奈米金粒子，一個奈米金粒子約有五十萬金原子所組成，其中檸檬酸離子包覆在奈米金粒子的表面上，並施以靜電排斥力穩定金奈米粒子，大幅降低粒子之間的團聚現象。
本實驗利用還原法合成9.2nm的奈米金粒子，其水溶液顏色為紅紫色並呈現負電性。為測試其穩定性，分別在奈米金溶液中添加氯化鉀溶液、蔗糖水、乙醇與異丙醇，其中，加入氯化鉀溶液的金溶液，由於鉀離子與檸檬酸離子的化學結合，溶液呈現了深藍色，隨著時間轉為淡藍，最後變為透明，且溶液中產生了團聚物；加入蔗糖水的金溶液則無顏色改變，由於蔗糖與水的水合作用中沒有伴隨電子的轉移，所以蔗糖分子與檸檬酸離子之間沒有發生化學反應；加入乙醇的金溶液緩慢地呈現深藍色，由於乙醇分子強烈的吸附性，替換了溶液中的氯金酸與檸檬酸離子，並降低了檸檬酸離子的負電性之後，使得些微的團聚發生，奈米金粒子的粒徑變為9.71nm；加入異丙醇的金溶液立即呈現深紫色，除了粒徑轉變為18.7nm外，其不均勻性大幅增加，可能是由於異丙醇分子的巨大吸附性，替換了溶液中的氯金酸與檸檬酸離子，並降低了檸檬酸離子的負電性之後，使得大規模的粒子團聚發生。
自組裝實驗採用添加異丙醇的奈米金溶液，在正己烷中加入定量的十六烷硫醇之後，將正己烷溶液倒入金溶液表面上，得到水/正己烷的液體界面，同時在此界面發生奈米金粒子自組裝現象，界面上的金自組裝膜隨著時間大面積地生成，由於所需的金粒子來自金溶液，所以金溶液的顏色將隨之淡化直到透明。
利用磁能攪拌棒來加快自組裝膜的生成，在穿透式電子顯微鏡下, 自然所得的自組裝金薄膜於大面積的組裝相當集中，明顯優於以攪拌所得後分布稀疏的金薄膜；在小面積下，自然所得的金薄膜會有重疊的現象，而經由攪拌所得的金薄膜則形成較好的單層薄膜，同時出現了有趣的分布圖案。

Reduction is the most popular method to synthesize gold nanoparticles by using interaction between precursor hydrogen tetrachloroaurate (HAuCl4) and reducer sodium citrate (Na3C6H5O7). Gold nanoparticles with diameter of 9.2 nm are nucleated under the citrate layer capping around their surfaces. The whole gold nanoparticles are stabilized and display in well-synthesized gold colloid solution since the capping citrate layers prevent gold nanoparticles from aggregation or precipitation by electrostatic repulsion. The stability of gold colloids solution is test by adding aqueous solution of potassium chloride (KCl), sucrose (C12H22O11), ethanol, or Isopropyl alcohol (IPA), in respectively. The color of gold nanoparticle solution changes into deep blue initially and becomes transparent finally if KCl solution is added. This is due to the chemical reaction between potassium and citrate ions. Some precipitations of potassium and citrate compound will appear in solution phase. However, no effective color change of gold colloid solution will happen if sucrose solution is added. The reason behind it is the molecules in sucrose solution are hydrated by water phase without any electron transfer occurring. Therefore, no chemical interaction affects the electronegative charge gold colloid solution. The ethanol-added gold solution is slowly changed to deep blue color. After TEM image measurement, the gold nanoparticles are approximate 9.71nm in diameter. The ethanol-added gold solution gradually becomes deep blue since ethanol molecules decrease the surface charge of gold nanoparticles by competitive adsorption among ethanol molecules, citrate and AuCl3- anions. The IPA-added gold solution shows deep purple color immediately. By using TEM images, the gold naoparticles in IPA-added solution are proved to be non-uniform in size and shape with average diameter around 18.7nm. The larger diameter of gold nanoparticles in IPA-added solution is due to the competitive adsorption among IPA molecules, citrates and AuCl3- anions is stronger than ethanol molecules. In this thesis, the IPA-added gold solution is selected in self-assembly experiment. In the self-assembly experiments, 1-dodecanethiol is first mixed with hexane solvent. When hexane solution is added into gold solution, a water/hexane interface is formed. The gold nanoparticles will be self-assembled at the interface. As growing with time, the color of gold solution becomes lighter and lighter. Because of the strong attraction between gold nanoparticles and 1-dodecanethiol in hexane solution, a gold film occurs at the interface. The gold film is consist of enormous amount of gold nanoparticles. Most of gold nanoparticles will finally self assembly at the interface. The color of gold solution becomes transparent after 3 hours. In the experiments, the magnetic stirrer is used to speed up the formation of self-assembly film. Under TEM inspection, long-range self assembly gold film is achieved in the case without stirring, but the relatively sparse distribution of gold nanoparticles appears in the case with stirring. Multi-layer films are also found if they grow without stirring, but the cases with stirring have monolayer films. For monolayer cases, nanoparticles form some patterns and the interstices among particles are clear.

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