Surface effect on the depletion potential between two spheres in a suspension of rods

National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University 210093 Nanjing, China

Corresponding author: gjin@nju.edu.cn

Received: 2 June 2007
Accepted: 19 September 2007

Abstract

We study the influence of a surface on the depletion potential between two spheres in a suspension of rods through Monte Carlo simulations under some simple approximate treatment on the statistical expression of free energy. If the length of the rods is larger than the radius of the spheres, the depletion potential between the two spheres when they are on a flat surface is remarkably weaker than that when they are in the bulk solution. If the surface is concave, as the curvature increases, the depletion potential will increase between a sphere and the surface but decrease between the two spheres. Contrarily, for a convex surface, as the curvature increases, the depletion potential will decrease between a sphere and the surface but increase between the two spheres. It is found that surface curvature brings about a much stronger effect to the depletion interaction between a sphere and the surface than that between the two spheres.