Self-assembly of spherical Janus particles in electrolytes

Experimental studies on nano- and micrometer sized Janus particles (JPs) have demonstrated a plethora of simple and complex self-assembled structures. In this study, molecular dynamics simulations that include long range Coulombic interaction have been utilized to elucidate the underlying physics of self-assembly of nano-scale spherical bipolar JPs as a function of surface charge density, salt concentration and particle size. Specifically, two distinct sub-structures at low JP concentration, namely, strings and rings have been identified. As the concentration of JPs is increased these sub-structures join and/or hierarchically assemble into larger porous clusters. Moreover, it has been demonstrated that surface charge defects lead to precipitous loss of directional self-assembly. Finally, a direct connection between the ionic cloud around a single JP and the self-assembled structure morphology has been demonstrated. Overall, the results of this study should pave the way for future coordinated experimental/computational studies towards development of a mechanistic understanding of morphology development in this class of material.