Van der Waals Colloidal Crystals

Abstract

A general guiding principle for colloidal crystallization is to tame the attractive enthalpy such that it slightly overwhelms the repulsive interaction. As-synthesized colloids are generally designed to retain a strong repulsive potential for the high stability of suspensions, encoding appropriate attractive potentials into colloids has been key to their crystallization. Despite the myriad of interparticle attractions for colloidal crystallization, the van der Waals (vdW) force remains unexplored. Here, it is shown that the implementation of gold cores into silica colloids and the resulting vdW force can reconfigure the pair potential well depth to the optimal range between -1 and -4 k_BT at tens of nanometer-scale colloidal distances. As such, colloidal crystals with a distinct liquid gap can be formed, which is evidenced by photonic bandgap-based diffractive colorization.

Keywords: colloids; gold nanoparticles; pair potentials; photonic crystals; van der Waals forces.