膠體粒子表面電位量測與粒子之自電泳

Abstract

近幾年，科學家已經能藉由設計膠體粒子表面性質或施加外加場來使控制粒子的移動或是組裝，且現在我們可以利用這些科技來完成如藥物輸送或是自組裝等目的。相較於討論已久的熱泳、電泳等物質輸送現象，具有白金的非對稱粒子在雙氧水溶液中的自泳動現象在最近也有許多相關研究。為了理解這個將化學能轉化為動能的運動現象，許多團隊分別提出了不同的運動模型來解釋它。然而，這些模型的理論與實驗結果皆有些互相衝突之處而無法被完全解釋之處，因此我們對於粒子表面性質與運動的部分設計做了一些實驗，來幫助我們更了解此現象之運動機制。 在本實驗中，我們利用界面活性劑與氨基矽烷改變粒子表面電性，從結果中發現到粒子運動速度的與界達電位呈線性關係，並且粒子的電位正負號也決定了粒子之運動方向。對於此結果，我們提出自電泳的運動模型來嘗試解釋粒子的泳動現象，並推測粒子之表面電位與粒子運動之關係。我們也利用氧化銦錫玻璃建立一個量測單顆粒子表面電位的實驗裝置，來幫助我們得到Janus粒子的界達電位。另外，從電場下粒子的電偶極實驗結果，也顯示與自電泳模型相似的結果。從這些實驗結果中，我們推測非對稱粒子在雙氧水溶液中具有電偶極性質與粒子運動速度與表面性質有關的結論。

Nowadays, scientists are able to control the motion and assembly of colloidal particles by designing their surface properties or applying external fields on them. People now can use these modern technologies to achieve some purposes, such as drug delivery or self-assembly. Comparing with some traditional phenomenon, such as thermophoresis and electrophoresis, self-propelled movement of Janus particles is a relatively new phenomenon of mass transport. Recently, several models are proposed to explain the self-propelled motion of Janus particles in hydrogen peroxide solution powered by chemical reaction. However, some conflictive experimental results obtained by different groups. For this reason we design experiments to study the surface effect of particles. In our study, the surfaces of particles are modified by silanization and adsorption of surfactants for changing the surface potential. The experimental results show that particle velocity is linearly proportional to zeta potential, and the direction of motion is related to sign of zeta potential as well. Therefore, we proposed a self-electrophoresis model to connect the relation between surface potential and the motion of particles. We also design an experimental setup for measuring the zeta potential of single colloidal particle. In addition, we obtain the electric dipole moment of Janus particles in electric field which agrees with our model. From these results, we suggest that Janus particles contain electric dipole and movements of particles are dependent on their surface properties.