粒子形狀及其表面帶電情況對其擴散泳行為的影響

Abstract

本論文利用有限元素分析法來探討不同電雙層厚度以及帶電條件對於一不均勻帶電的橢圓形粒子之擴散泳行為的影響。所考慮的系統包含不同的邊界、形狀、以及帶電情況。數值模擬結果顯示在粒子周圍的極化現象亦即粒子沉浸在無限溶液中的主要驅動力，會強烈地受到粒子型狀的影響。另外當粒子不均勻帶電時，在粒子各處的電雙層不僅受極化且被其他處的電雙層影響，使得擴散泳行為更為複雜。而離子的累積伴隨著電雙層的極化是來自於粒子所提供的阻礙以及當離子由高濃度端擴散至低濃度端時粒子與其間的交互作用，代表著邊界在擴散泳中扮演著重要的角色。更甚者，因離子之不同的擴散係數而造成的電泳也成會另一股擴散泳的驅動力。由此可說明邊界的存在甚至是粒子的形狀及帶電狀況對於擴散泳行為都有不可忽視的影響。

The influences of a boundary, shape and charged condition of a particle on its diffusiophoretic velocity are investigated theoretically by considering the diffusiophoresis of an ellipsoidal particle and nonuniformly charged spherical particle under various conditions of double layer thickness and charged conditions. We shows that the polarization of the double layer around the particle, which is the driving force while a particle immersed in an infinite solution, is strongly affected by the shape of the particle. In addition, if a particle is heterogeneously charged, the double layer on each part of the particle is polarized and affected on the its other parts, making the diffusiophoretic behavior complicated. Together with the polarization of double layer, the accumulation of the ions comes from the hindrance of the particle and the interaction between the ions and the particle when they diffuse from the high-concentration side to the low-concentration side coming from the presence of the boundary also play a important role. Moreover, he background electrophoresis generating from the difference in ionic diffusivities also contribute to the diffusiophoretic driving force. In these ends, the presence of a boundary, shape and charged condition of a particle have a profound influence on its diffusiophoretic behavior.