Effects of valences of salt ions at various concentrations on charged dendrimers

Abstract

The static properties of charged dendrimers in salt solutions with explicit salt ions are investigated by coarse-grained molecular dynamics simulations. The emphasis is placed on the effects of valences of ions with different salt concentrations. We find that the conformations of dendrimers are of weak dependence on ionic strength in monovalent salt solution, while dendrimers in multivalent salt solution display structural transitions with increasing the salt concentration. At each salt concentration, the higher the valence of salt ions is, the more compact the dendrimers become. We also witness that dendrimers show the dense-core conformation accompanied by a back-folding terminal shell under all the conditions studied and that their shapes are also not sensitive to valences and concentrations of salt ions. Furthermore, charge layering shows no clear difference among different salt concentrations in a monovalent salt solution, whereas it undergoes multi-state transitions in multivalent salt solution with the addition of multivalent salt ions and with the change of valences at a given salt concentration, implying that multivalent salt ions have a significant influence on the interior conformations of charged dendrimers in comparison with univalent salt ions. Moreover, overcharging of dendrimers is observed in multivalent salt solution at high salt concentrations but not in a monovalent salt solution.