Issue
EPL
Volume 86, Number 6, June 2009
Article Number 66001
Number of page(s) 5
Section Condensed Matter: Structural, Mechanical and Thermal Properties
DOI http://dx.doi.org/10.1209/0295-5075/86/66001
Published online 17 June 2009
EPL, 86 (2009) 66001
DOI: 10.1209/0295-5075/86/66001

Confinement-induced orientational alignment of quasi-2D fluids

K. Nygård1, D. K. Satapathy1, J. Buitenhuis2, E. Perret1, O. Bunk1, C. David1 and J. F. van der Veen1, 3

1   Research Department of Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut CH-5232 Villigen PSI, Switzerland
2   Institute of Solid State Research, Forschungszentrum Jülich - D-52425 Jülich, Germany, EU
3   ETH Zürich - CH-8093 Zürich, Switzerland

kim.nygard@psi.ch

received 8 May 2009; accepted in final form 3 June 2009; published June 2009
published online 17 June 2009

Abstract
We have developed a unique approach for studying the ensemble-averaged nearest-neighbor coordination of confined fluids by combining small-angle X-ray scattering and phase-retrieval–based X-ray diffraction from fluid-filled nanofluidic channel arrays. We apply the method to a charge-stabilized quasi–two-dimensional colloidal fluid (particle diameter 48 nm), focusing on the structural transition from a monolayer to a bilayer with increasing fluid film thickness. In contrast to theoretical work on the paradigmatic hard-sphere fluid, we find unambiguous experimental evidence for orientational alignment of fluids in extreme confinement.

PACS
68.08.-p - Liquid-solid interfaces.
61.05.cf - X-ray scattering (including small-angle scattering).
82.70.-y - Disperse systems; complex fluids.

© EPLA 2009