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Adsorption of core-shell nanoparticles at liquid–liquid interfaces

Year: 2011

Journal: Soft Matter, 2011, 7, 7663-7675, 20111207

Authors: Isa L 1 *, Amstad E. 1, Schwenke K 2, Del Gado E. 2, Ilg P. 3, Kröger M 3, Reimhult E. 1 4

Last authors: Erik Reimhult

Organizations: 1 Laboratory for Surface Science and Technology, Department of Materials, ETH Zürich, Wolfgang-Pauli-Strasse 10, 8093, Zürich, Switzerland. E-mail: lucio.isa@mat.ethz.ch; Fax: +41 (0)44 633 10 27; Tel: +41 44 633 63 76 2 Microstructure and Rheology, Institute for Building Materials, Department of Civil, Geomatic and Environmental Engineering, ETH Zürich, Schafmattstrasse 6, 8093, Zürich, Switzerland 3 Polymer Physics, Department of Materials, ETH Zürich, Wolfgang-Pauli-Strasse 10, 8093, Zürich, Switzerland 4 Department of NanoBiotechnology, University of Natural Resources and Life Sciences (BOKU) Vienna, Muthgasse 11, 1190, Vienna, Austria

Country: Switzerland, Austria

The use of nanoparticles as building blocks for the self-assembly of functional materials has been rapidly increasing in recent years. In particular, two-dimensional materials can be effectively self-assembled at liquid interfaces thanks to particle localization and mobility at the interface in combination with tailoring of specific interactions. Many recent advances have been made in the understanding of the adsorption and assembly at liquid interfaces of small hydrophobic nanoparticles stabilized by short-chain rigid dispersants but the corresponding studies on core-shell nanoparticles sterically stabilized by extended hydrophilic polymer brushes are presently missing. Such particles offer significant advantages in terms of fabrication of functional, responsive and bio-compatible materials. We present here a combination of experimental and numerical data together with an intuitive and simple model aimed at elucidating the mechanisms governing the adsorption of iron oxide nanparticles (5–10 nm) stabilized by low molecular weight poly(ethylene glycol) (1.5–10 kDa). We show that the adsorption dynamics and the structure of the final assembly depend on the free energy of the particles at the interface and discuss the thermodynamics of the adsorption in terms of the polymer solubility in each phase.