Self assembly of magnetic nanoparticles at silicon surfaces

• Autorzy: Theis-Bröhl K. , Gutfreund P. , Vorobiev A. , Wolff M. , Toperverg B. P. , Dura J. A. , Borchers J. A.
• Języki publikacji: EN

Abstrakty

EN

Neutron reflectometry was used to study the assembly of magnetic nanoparticles in a water-based ferrofluid close to a silicon surface. Under three conditions, static, under shear and with a magnetic field, the depth profile is extracted. The particles have an average diameter of 11 nm and a volume density of 5% in a D2O–H2O mixture. They are surrounded by a 4 nm thick bilayer of carboxylic acid for steric repulsion. The reflectivity data were fitted to a model using a least square routine based on the Parratt formalism. From the scattering length density depth profiles the following behavior is concluded: the fits indicate that excess carboxylic acid covers the silicon surface and almost eliminates the water in the densely packed wetting layer that forms close to the silicon surface. Under constant shear the wetting layer persists but a depletion layer forms between the wetting layer and the moving ferrofluid. Once the flow is stopped, the wetting layer becomes more pronounced with dense packing and is accompanied by a looser packed second layer. In the case of an applied magnetic field the prolate particles experience a torque and align with their long axes along the silicon surface which leads to a higher particle density.

• Wydawca: Wydawnictwo Uniwersytetu Morskiego w Gdyni
• Czasopismo: Zeszyty Naukowe Akademii Morskiej w Gdyni
• Rocznik: 2016
• Tom: nr 94
• Strony: 34--52
• Opis fizyczny: Bibliogr. 34 poz., rys., tab.

Twórcy

autor

Theis-Bröhl K.

• University of Applied Sciences Bremerhaven, Germany

autor

Gutfreund P.

• Institut Laue-Langevin, Grenoble, France

autor

Vorobiev A.

• Division for Materials Physics, Uppsala University, Sweden

autor

Wolff M.

• Division for Materials Physics, Uppsala University, Sweden

autor

Toperverg B. P.

• Institute for Solid State Physics, Ruhr-University Bochum, Germany
• Petersburg Nuclear Physics Institute, Gatchina, Russia

autor

Dura J. A.

• NIST Center for Neutron Research, Gaithersburg, USA

autor

Borchers J. A.

• NIST Center for Neutron Research, Gaithersburg, USA

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