In order to obtain the aggregation free energy (Δ ag G) for a pair of NPs in ILs and also to characterize free energy barriers for the aggregation, the potential of mean force (pmf) was computed (Figure top) for the dissociation of both hydrophilic and hydrophobic particles (red and green curves, respectively) in both 1-butyl-3-methyl-imidazolium tetrafluoroborate ([BMIM]