Self-assembly of polystyrene sphere colloidal crystals by in situ solvent evaporation method

The three-dimensional (3D) ordered colloidal crystals were fabricated on the surface of polystyrene (PS) emulsion through an in situ solvent evaporation, which was controlled by altering both emulsion temperature and environmental pressure. The evaporation rate serves as an important role in intensifying the sphere transfer through solution flux and the capillary force between spheres for assembly, as well as supporting a stable close packing of colloidal crystals. The self-assembly process behaves a multi-nucleus site evolution, and the plane packing undergoes a transformation from square to hexagonal arrangement. The colloidal crystal array achieves an ordered close packing with multi-layer structure at evaporation temperature of 50 °C at normal pressure or proper pressure range of 160–500 mmHg at room temperature. The in situ solvent evaporation by decreasing the environmental pressure at room temperature could reduce disturbing effect of Brownian diffusion for an ordered PS colloidal crystal arrangement. The relationship between layer thickness and in situ evaporation time is a linear trend in time range of 20–75 min.