5:15 PM - 5:30 PM
▲ [14p-B5-10] In-situ observation of two dimensional nucleation in colloidal crystals with depletion attraction
Keywords:Two dimensional nucleation, colloidal crystals, depletion attraction
Understanding nucleation process is critically important in fields including metallurgy, physics, biology and so on. However, Nucleation kinetics remains unclear due to the limitations of existing experimental evidence. Colloidal crystals have been used as a good model for studying phase transition such as crystallization, glass transition, nucleation process. In this study, we focus on two-dimensional nucleation of colloidal crystals with depletion attraction, which is observed at single particle level.Nucleation process was monitored by optical microscopy. colloidal particles crystallize when the number of particles in an embryo is larger than the critical number , while the embryos disappear if the particle number is less than the critical number. However, embryos with two layers grow even if the particle number is smaller than the critical value of single layer. The critical numbers at various area fractions were obtained. The second layer of the embryos promote nucleation.We explain this phenomenon by evaluating Gibbs free energy change. To calculate Gibbs free energy change, surface free energy and line tension are obtained based on CNT equation (which are in good agreement with the value in hard sphere model). The calculation results suggest that Gibbs free energy change of two layers is smaller than that in critical single nucleus.