Molecular dynamics simulation of the forces between colloidal nanoparticles in Lennard-Jones and n-decane solvent

Molecular-dynamics is utilized to simulate solvation forces between two nanoparticles immersed in two different solvents: Lennard-Jones spheres and and n-decane. Three different sizes and shapes of solvophilic nanoparticles are investigated. Nanoparticles in the Lennard-Jones liquid exhibit solvation forces that oscillate between attraction and repulsion as the nanoparticle separation increases. The magnitude of these solvation forces increases with particle size and depends on particle shape, consistent with the Derjaguin approximation. When n-decane is the solvent, the solvation forces are negligible for small nanoparticles, with sizes comparable to the end-to-end distance of all-trans decane. The solvation forces oscillate between attraction and repulsion for sufficiently large nanoparticles in decane-however the Derjaguin approximation does not appear to be effective at describing the dependence of nanoparticles forces on nanoparticle size and shape when decane is the solvent. For both the Lennard-Jones and n-decane solvents, it is apparent that the force profiles are influenced by the surface roughness of the nanoparticles. These factors should be taken into account in efforts to engineer colloidal suspensions.