Structural Characterizations of Charged Colloidal Crystals

We examined influences of the particle volume fraction  and effective charge number Zeff on the crystal structures of charged colloids, by means of the reflection spectroscopy and Kikuchi-Kossel diffraction measurements. We employed dilute salt-free aqueous dispersions of charged polystyrene (PS) particles (the diameter d = 110 to 120 nm; Zeff = about 1300) and colloidal silica (d = 120 nm, Zeff = about 550). The PS colloids had the BCC structure at  ≤ 0.01 and exhibited the structural phase transition into the FCC lattice on increasing . The silica colloids, which had lower Zeff, took the BCC structures at all s examined (≤ 0.04). Keyword(s): charged colloidal crystal, BCC-FCC phase transition, reflection spectroscopy. Received 31 Dec. 2014, accepted 10 Mar. 2015, published 31 Apr. 2015