Localized adsorption of particles on spherical and cylindrical interfaces

Abstract

Localized, sequential adsorption of spherical particles interacting via the screened Coulomb potential was analyzed theoretically by means of the Monte Carlo (MC) numerical technique. Simulations were performed for planar, spherical, and cylindrical interfaces (collectors) for various dimensionless particle radii (aspect ratio) A = a R and the κa parameter characterizing the range of repulsive double-year forces. All results obtained for hard spheres ( κa = ∞) and various interface shapes can be reduced to the universal relationship πa 2 N p S ∗ = θ ∞ = 0.546 (where N p is the average number of particles adsorbed at a collector and S ∗ = S c (1 ± A) m is the effective surface area available for particles ( m = 0, 1, and 2 for the planar, cylindrical, and spherical collector, respectively, and the minus sign denotes adsorption on the internal collector surface)). The maximum surface concentration of soft spheres found from our MC simulations was always smaller than the above value of θ0 ∞ and can be well approximated by the relationship θ mx = θ ∞ (1 ± A) m (1 + H ∗) 2 (where H ∗ is the effective range of the lateral double-layer interactions). The pair correlation function for hard and soft spheres was also determined and a definite tendency toward a short-range ordering was revealed for particle surface concentrations close to the above θ mx values (analogous to a 2D hard-disk fluid). Our theoretical results were compared with the existing experimental measurements of others and a satisfactory qualitative agreement was found.