title: Fast formation of opal-like columnar colloidal crystals.
abstract: We demonstrate that highly polydisperse colloidal gibbsite platelets easily form an opal-like columnar crystal with striking iridescent Bragg reflections. The formation process can be accelerated by orders of magnitude under a centrifugation force of 900 g without arresting the system in a disordered glassy phase. Using transmission electron microscopy and small-angle X-ray scattering techniques, we find that the forced sedimentation is accompanied by particle size fractionation, leading to inversion of the iridescent colors. The relatively easy self-organization of the polydisperse colloidal particles into opal-like crystals may be explained on the basis of the observed particle fractionation and possibly also on hexatic-like ordering.
authors.affiliation: Van't Hoff Laboratory for Physical and Colloid Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands. david.vanderbeek@albemarle.com
authors.forename: David
authors.initials: D
authors.lastname: van der Beek
authors.forename: Paul B
authors.initials: PB
authors.lastname: Radstake
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Petukhov
authors.forename: Henk N W
authors.initials: HN
authors.lastname: Lekkerkerker