Crystallization of charged colloidal particles: an experimental study

Colloidal crystals are fabricated through a self-assembly process of monodispersed polystyrene particles. Evolution of colloidal crystal structures is analyzed by Kossel diffraction technique and UV-Vis spectrophotometer. According to the changes in the Kossel patterns we find the crystal structures change with passage of time and experience successively the following stages: liquid state-random layer structure-stacking disorder structure-fcc with (111) twin-normal fcc structure. The plane distances of different crystal planes and the lattice constants are also determined in this study. The 111 plane distances and the lattice constants evaluated according to the measurement of transmission spectrum are in accordance with the results by the analysis of Kossel line. In addition, it was found that the peaks of the transmission spectrum become sharper and shift considerably toward shorter wavelength during the crystal evolution, showing the lattice constants become smaller.