Measurement of Surface Potential and Self-electrophoresis of Colloidal Particles
Date Issued
2015
Date
2015
Author(s)
Lin, Yen-Wei
Abstract
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.
Subjects
self-electrophoresis
zeta potential
Janus particle
Type
thesis