Ion-mediated interactions between charged and neutral nanoparticles

Monte-Carlo simulations are used to study the ion-mediated effective interaction between weakly charged and highly charged nanoparticles in an implicit solvent. Three models of nanoparticles are successively studied, from crude charged hard spheres to dipolar and non-spherical nanoparticles. The analysis of the effective potential revealed that in an electrolyte solution, even a neutral nanoparticle feels an important repulsive force in the presence of a charged nanoparticle, with a typical range similar to the Debye length. When the two nanoparticles carry charges of opposite sign, we have shown that this repulsion can reverse the effect of the direct attractive electrostatic potential at short distances. This also yields the change of sign of the effective potential as a function of the relative orientations of two anisotropic nanoparticles. Moreover, we found that the 3-body terms of the effective potentials can overcome the 2-body terms, which is not observed in the case of symmetrically charged nanoparticles.