Depletion interaction in a quasi-two-dimensional binary colloid mixture: Monte Carlo simulations.

We report the results of extensive calculations of the depletion interaction between the large hard spheres in a quasi-two-dimensional (q2D) binary mixture of large and small hard spheres. Two definitions of the depletion interaction have been examined, and the dependencies of both on the large and small sphere densities, and the confining wall separation have been explored. The results of the simulations show that the depletion interaction is enhanced relative to its magnitude in a three-dimensional binary mixture with the same density, composition and sphere diameter ratio and that it has a complex dependence on the large sphere-large sphere separation. There are qualitative differences between the properties of q2D and mathematical 2D systems that are relevant to the interpretation of experimental data.