Colloidal Model for the Study of Nucleation and Crystallization from Solution

Crystallization is a ubiquitous phenomenon that is important for materials in our daily life. Despite development of microscopic techniques, it is still challenging to observe crystallization processes at single molecule level due to temporal or spatial limitations. Thus, there remain fundamental open questions on how the interactions between monomers affect nucleation and growth from solution. Here, we study a model colloidal system as an alternative to atomic systems. The interactions between charged particles are tuned by screening the electrostatic repulsion and inducing depletion attractions with salt and non-adsorbing polyacrylamide, respectively. Analysis of the particle positions allow us to monitor the crystallization events. In quasi-2D experiments, clusters at a particular combined well-depth of ~2 kT are constantly rearranging during growth, and the fraction of crystal-like bonds increases non-monotonically. Solubility of the monomers at various conditions is determined and the thermodynamically-derived bond strength is in good agreement with our interparticle potential curve. Thus, we demonstrate a tunable colloidal system that is expected to provide insight into the mechanism of crystallization from solution.