利用大氣微電漿在固液介面合成奈米金屬之研究

Abstract

大氣噴射電漿(atmospheric-pressure plasma jet)除了應用於處理固體表面，近年來應用在處理液相方面受到極大的關注。過去許多研究指出大氣噴射電漿可以持續提供電子並且還原溶液中的金屬離子，相較於傳統電鍍，金屬被還原並附著在陰極電極上，而大氣噴射電漿的陰極為氣相電極，金屬晶粒直接在溶液中成核。我們發現某些條件改變時(例如:溶液黏度、溶液種類、陽極親疏水性…等)，成核點和晶粒形狀會有所改變，甚至會在陽極表面成核。根據以上特性，我們提出一種新的表面合成奈米金屬技術，能在濕潤的固體表面用大氣噴射微電漿直接寫出奈米金屬。 在過去許多大氣噴射電漿合成奈米金屬的文獻中，大部分都是在溶液中合成奈米金屬及其應用，在固液界面合成奈米金屬和成核點的研究非常少，所以本論文主要分成兩個部分，第一部份為研究溶液及表面特性與成核點的關係；第二部分則是將此技術在應用在製備Janus粒子上。 本論文第一部份，首先我們使用雷射打標機增加氧化銦錫玻璃(Indium tin oxide glass, ITO)親水性，並在上面滴上硝酸銀溶液，在這實驗中我們觀察到在電極邊緣有較多的銀奈米顆粒。接著我們將氧化銦錫玻璃使用氧電漿處理增加其親水性，並比較在相同溶液深度下親疏水成核之差異，相較於未處理之氧化銦錫玻璃，在氧電漿處理後的氧化銦錫玻璃銀奈米顆粒更容易從硝酸銀被還原出來。為了觀察溶液對成核的影響，我們在溶液中分別添加甘油和聚乙二醇改變溶液黏度，以及在溶液中添加聚苯乙烯粒子增加成核點，結果顯示成核點確實會因為溶液成份而有所改變，甚至會影響到晶形。 根據第一部分之結果在本論文第二部分，我們將此技術應用在製備銀奈米顆粒塗層Janus粒子。我們將單層聚苯乙烯粒子鋪在含有硝酸銀溶液瓊脂糖凝膠上，由於瓊脂糖凝膠機械性質以及極薄的水膜，在聚苯乙烯粒子周圍水膜的表面張力會造成瓊脂糖凝膠凹陷，當使用大氣噴射微電漿處理時銀奈米顆粒將被還原出來並附著於聚苯乙烯粒子下半球。根據此實驗結果，我們提出一種新的製備銀奈米顆粒塗層Janus粒子的技術，此技術能夠調整銀奈米顆粒的大小以及覆蓋程度，而且在銀奈米顆粒塗層Janus粒子能夠觀察表面電漿子效應，因此可將此種粒子應用在表面偵測和抗菌等方面。

Atmospheric-pressure plasma jet (APPJ) is not only used to treat the solid surface but also attracts great attention in the liquid phase. In particular, many studies report that the electrons could be provided continuously by APPJ to reduce the metal ions in the solution. Compared with the cathode of traditional electroplating, the cathode of APPJ is gas electrode. Hence, the metal crystals are nucleated in the solution. However, we observe that the nucleation site and the crystal shape would be changed in some condition (e.g. viscosity of the solution, additive, hydrophilicity of anode, etc.). The metal crystals are even nucleated on the anode. Based on these features, we propose a new technology which is directly writing metallic nanoparticles on the moist surface by APPJ. In the previous studies about the synthesis of metal nanoparticles by APPJ, most of them are the synthesis of metal nanoparticles in the solution and its application. It is rare to study the synthesis of metal nanoparticles on the solid surface and the nucleation site of metal nanoparticles, so this thesis is mainly divided into two parts. The first part is to study the effect of solution and surface properties on nucleation sites. In the second part, we prepare Janus particles on the moist surface by microplasma. In the first part of this paper, we use the laser marking machine to increase the hydrophilicity of Indium tin oxide (ITO) glass on which the silver nitrate solution was drop-coated. In this experiment, we observe that there are many Ag nanoparticles on the edge of the electrode. We also use the oxygen plasma to increase the hydrophilicity of the ITO glass and compare the difference between hydrophilic and hydrophobic nucleation at the same liquid level. Compare with the ITO glass without oxygen plasma treatment, the Ag nanoparticles are easily reduced on the hydrophilic ITO glass. In order to observe the influence of solution, we add glycerol and polyethylene glycol respectively to the solution to change the viscosity of the solution, in addition, we add the polystyrene particles to increase the nucleation site. The results show that the nucleation sites do change due to solution composition and even affect the crystal shapes. Based on the results of the first part, we apply this technique in the preparation of Ag nanoparticles coated Janus particles in the second part. The monolayer of PS particles is prepared on the agarose gel which contains the silver nitrate solution. Due to the mechanical properties and the thin water film of agarose gel, the indentation of agarose gel is caused by the surface tension of water film around the PS particles. When the atmospheric microplasma jet applied, the Ag nanoparticles will be reduced and attached to the lower hemisphere of PS particles. Based on the experiment results, we propose a new technology for preparing Ag nanoparticles coated Janus particles. This technology can adjust the particles size of Ag nanoparticles and the coverage of Janus particles. Moreover, the surface plasmon can also be observed, which makes the particles useful for the application of surface sensing and antibacterial function.