Fabrication of ordered films of polystyrene–gold composites by a new flow-controlled method

A new method to form millimeter-sized colloidal crystals of polystyrene microsphere-gold composites has been developed. The experimental setup––a surface-treated microslide placed onto an inclined short burette that contains the mixture of microspheres and gold colloids––allows a controlled array growth at a steady, low rate. The velocity of the receding suspension can be controlled by both the angle of inclination of the burette and the degree of the opening of the stopcock. The dependence of the structure and the optical properties of the composite on the array growth rate, the volume fraction of microspheres, and the presence of a surfactant have been studied. Atomic force microscopy (AFM) measurements have shown that well-ordered hexagonal arrays are formed at low angles when suspensions with high volume fractions and gold nanoparticles are deposited at a very low rate. Micro-Raman spectroscopy measurements showed an enhancement effect brought about by the gold aggregates present in the sample. The high quality of the composite film obtained by this simple and yet efficient method makes it interesting for photonic applications.