Diffusiophoresis of Polystyrene Spheres in Electrolyte Solutions

• Main Authors: Chia-wei Yang, 楊家瑋
• Other Authors: Peilong Chen
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/7c4avb

碩士 === 國立中央大學 === 物理研究所 === 97 === In this thesis we investigate dynamical properties of 1 micrometer colloids placed in a narrow channel which is filled with a sodium chlorine solution and a glucose solution with a concentration gradient. Our device contains two reservoirs: one contains a NaCl solution, and the other is pure water. They are connected by a narrow channel of 60 micrometer depth and 0.5 mm in width. Because of the different NaCl/glucose concentration in the reservoirs, the ions of NaCl and molecules of glucose would diffuse from the high concentration reservoir to the low-concentration one, and a concentration gradient set up. By recording the motion of colloids under a microscopic, we study the colloids random motion and average flux induced by concentration of the NaCl. However, we find the the direction of the migration of the colloids in the NaCl solution are very different to be compared in the glucose solution. The colloids in the NaCl solution move from the higher concentration to the lower one, and the opposite direction occur in the glucose solution. We find that the velocity of colloid is proportional to square root of concentration in dilute region which is consistent with the derivation of the relation between the concentrations and the velocities in dilute concentration based on Debye-Huckel theory. Furthermore, we compare the experimental result with the theory proposed by Deryagin and co-workers, the surface charges increase with the concentration of the electrolyte solutes increasing.