Strong Attraction Between Like-Charged Metal Nanoparticles Mediated by Multivalent Counterions

In the present work, we develop a method which allows us to use Monte Carlo simulations to study a system with two conducting charged nanoparticles in an electrolyte solution. We show that the electrostatic/entropic interaction between charged nanoparticles depends strongly on the nanoparticle material, particularly in the case of multivalent counterions. The results for monovalent electrolyte and metallic nanoparticles are compared with mean-field theory showing an excellent agreement. The present work shows that metal nanoparticles can form aggregates much more easily than nonpolarizable nanoparticles, specially in the case of surrounding multivalent counterions. They are present in the region between metallic nanoparticles and induce a strong attraction between them. In the case of highly charged nanoparticles, the attraction is comparable to dispersion forces at short separations.