Electro-optics of colloidal crystals studied by the electric potential and reflection spectroscopy

Electric and photometric properties of colloidal crystals deformed in an external electric field have been studied. The colloidal crystals show the electric potential storage ability as an electric energy capacitor. Two components of decay times—slow and fast—are obtained from the decay curves of the internal electric potential voltage and the reflection intensity. The decay times range from 4 to 60 s and from 0.05 to 0.6 s for the slow and fast decays, respectively. The former is attributed to the visco-elastic fluctuation of the constituent particles in the colloidal lattices and the latter to their synchronous elastic fluctuation. The slow decay times obtained from the electric potential measurements are larger than those obtained from the reflection measurements, whereas the fast decay times obtained by the former are smaller than those obtained by the latter. The electric measurements observe the change in the crystal lattices in the total area between electrodes, whereas the reflection method observes mainly those in the surface area of the cell.