Effect of counterion size in spherical electric double layer of concave shape

The steric effect of counterions on the electrical properties of spherical electric double layer of concave shape is discussed. In the theory, the electrostatic interaction is described by the mean field approximation, while the finite size of particles in the solution is considered by the excluded volume effect. We showed that near the spherical charged surface of concave shape, the number density of counterions decreases for large counterions compared to the dimensionless counterions while the electrostatic potential near the charged surface increases size of the counterions.