Mechanism of Floating Self-assembly of Binary Colloidal Particles at Water-Air Interface of Suspension

The floating self-assembly of submicron monodisperse polystyrene (PS) spheres and SiO2 nanoparticles at water-air interface of suspension (floating assembly method) was presented in this article. The mechanism of this method was extensively studied. It was shown that the assembly of PS microspheres was dominant in the floating assembly of binary colloidal particles. At definite phase concentration, the formation of ordered structure of PS microspheres had nothing to do with the initial volume ratio of PS microspheres and SiO2 nanoparticles in suspension. When the diameter of PS microspheres was in the range of 150-500 nm, the ordered structure could be obtained easily, otherwise it was difficult. The self-assembly of SiO2 nanoparticles was a depositing process at the surface of PS microspheres as substrate. The volume fraction of SiO2 particles in binary colloidal crystal was determined by the phase concentration of SiO2 in suspension.