Kinetics and surface behavior of electrostatically adsorbed particles at a solid-liquid interface.

摘要

In this thesis, we have studied and answered two questions pertaining to the process of electrostatically driven particle adsorption at a solid-liquid interface. Electrostatically driven particle adsorption at a solid-liquid interface is a cheap and labor free method of generating layers of particles on a solid surface. The process involves dipping the bare solid surface in a particle suspension with the pH and the ionic strength of the suspension adjusted such that the particles and the solid surface have opposite signs of surface charge. The particles are hence driven towards the solid surface and get adsorbed on the solid surface.;The magnitude and sign of surface charge on a material is quantified in terms of an experimentally measurable quantity known as zeta potential. This zeta potential for any material is a function of the pH and the ionic concentration of the solution the material is in contact with. The first question that we have answered in this thesis is about the influence that the particle/solid surface zeta potentials have on the kinetics of the particle adsorption process. A model that coupled transport equations, thermodynamics and geometry logic was built to predict the adsorption kinetics. The model was validated with experimental results for the system of Polystyrene particle adsorption on a silicon wafer at different suspension pH values. The second question that we have answered is whether the adsorbed particles can move laterally on the solid surface or not. We end the thesis by discussing two open questions for the same system.