Heterogeneous local order in self-assembled nanoparticle films revealed by X-ray cross-correlations

Felix Lehmkühler; Florian Schulz; Martin A Schroer; Lara Frenzel; Holger Lange; Gerhard Grübel

doi:10.1107/S2052252518005407

Heterogeneous local order in self-assembled nanoparticle films revealed by X-ray cross-correlations

IUCrJ. 2018 Apr 28;5(Pt 3):354-360. doi: 10.1107/S2052252518005407. eCollection 2018 May 1.

Authors

Felix Lehmkühler^{1

2}, Florian Schulz^{2

3}, Martin A Schroer⁴, Lara Frenzel^{1

2}, Holger Lange^{2

3}, Gerhard Grübel^{1

2}

Affiliations

¹ Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, 22607 Hamburg, Germany.
² The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany.
³ Institute of Physical Chemistry, University of Hamburg, Grindelallee 117, 20146 Hamburg, Germany.
⁴ European Molecular Biology Laboratory EMBL c/o DESY, Notkestrasse 85, 22607 Hamburg, Germany.

Abstract

We report on the self-assembly of gold nanoparticles coated with a soft poly(ethylene glycol) shell studied by X-ray cross-correlation analysis. Depending on the initial concentration of gold nanoparticles used, structurally heterogeneous films were formed. The films feature hot spots of dominating four- and sixfold local order with patch sizes of a few micrometres, containing 10⁴-10⁵ particles. The amplitude of the order parameters suggested that a minimum sample amount was necessary to form well ordered local structures. Furthermore, the increasing variation in order parameters with sample thickness demonstrated a high degree of structural heterogeneity. This wealth of information cannot be obtained by the conventional microscopy techniques that are commonly used to study nanocrystal superstructures, as illustrated by complementary scanning electron microscopy measurements.

Keywords: X-ray cross-correlations; XCCA; gold nanoparticles; self-assembled nanoparticle films.

Grants and funding

This work was funded by Deutsche Forschungsgemeinschaft grants EXC1074, SCHU 3019/2-1, and LA 2901/2-0. Bundesministerium für Bildung und Forschung grant 05K16YEA to Martin A. Schroer.