High Pressure SAXS on Collodial Crystallite Suspensions

Martin Schroer, Fabian Westermeier, Felix Lehmkuehler, Sabrina Conrad, Alexander Schavkan, Alexey Zozulya, Birgit Fischer, Michael Sprung, Christian Gutt, Gerhard Gruebel
2015
Ordered films and crystals made out of nanoparticles are interesting materials as they can exhibit exciting new optical properties and thus can be used e.g. as photonic crystals [1] . Crucial for the application of such systems is the degree of order of the nanoparticle arrays as well as their response to external stimuli, such as high pressure. In particular for colloidal films, special attention has to be paid to the local order within the nanoparticle arrays that depends on the underlying
more » ... ing process. Investigating the structure and orientational order of both thin films and crystals under external perturbations can be perfectly done with the X-ray cross correlation analysis (XCCA) technique [2] [3] [4] . Two studies, a) on thin colloidal films and b) on colloidal crystal suspensions employing this method will be discussed. First, we will present a scanning small angle X-ray scattering (SAXS) study using a nanometer size beam on dried nanoparticle films made out of a binary colloidal mixture of two particle species differing in size. Due to the small beam size only a finite number of particles give rise to the scattering signal. By scanning the sample, structure and composition of the films can be determined spatially resolved in terms of scattering intensity maps. The local type and degree of orientational order is revealed by studying the angular correlations of the scattering patterns via XCCA. Based on this X-ray cross correlation microscopy approach, spatial maps of the local degree of order are obtained that allow to identify specific differences in the local film structures formed by the two nanoparticle species [5] . In addition, we report on a recent SAXS and XCCA study on suspensions of colloidal crystals under high pressure. A complex pressure-dependence of the crystals is revealed, reflecting a delicate balance of water compression and changes of the electrostatic properties.
doi:10.3204/pubdb-2015-03680 fatcat:l5v7s64l2fefrnef2riyqkpvgy