Synthesize of Polymer Colloidal Crystal

Colloidal crystals are highly ordered materials that possess a periodically dielectric constant. Due to their unique optical properties, colloidal crystals have potential applications in photonic crystals, biosensors, templates and tissue engineering. In this study, the “bottom-up” self-assembly method was developed to assemble the PSs nanoparticles into a 3-dimensional (3D) arrays. Monodispersed polystyrene spheres (PSs) suspensions (2.5 wt% in water, surfactant free) with spheres diameters of 250 nm were purchased from Alfa Aesar company (standard deviation of the diameter of PSs is less than 5%). The assembly uses the capillary forces at the meniscus of a colloidal suspensions to draw colloids into face con centered cubic (FCC) close-packed arrays. In this approach, the PS nano particle suspensions were diluted by adding water purified by a Milli-Q system. As substrates we used hydrophilic microscope glass. 90 ml spheres suspensions were displaced into a cell. In order to precisely control the temperature and humidity of film growth, the cell then was put into an incubator. As the solvent evaporates, the water flow convention brings the nano particles into the center of the substrate, coating it with spheres that can be assembled into highly crystalline arrangement. The 3D structures of polystyrene colloidal crystals were examined by using scanning electron microscopy (SEM). We also investigated the humidity and temperature effects on the formation of the polystyrene colloidal crystals