Synchrotron Small-Angle X-ray Scattering of Colloids and Photonic Colloidal Crystals

Abstract

Synchrotron small-angle X-ray scattering (SAXS) experiments have been performed at the ESRF on colloidal dispersions. The samples are optically multiply scattering and are aimed at so-called photonic applications. Scattering from dilute suspensions yields the particle form factor, which shows many oscillations. From these results, the radius, size distribution and information about the internal structure of the particles in situ can be determined, in contrast to most studies on colloids. Using the form factor, structure factors can be extracted from the diffraction patterns of the colloidal crystals. The structure factors clearly reveal sharp Bragg peaks. The crystal structure, lattice parameter and average orientations were determined as a function of height in sedimented samples. This provides important information for the interpretation of optical experiments.