Universität zu Köln

Hod, M., Dobroserdova, A., Samin, S., Dobbrow, C., Schmidt, A. M., Gottlieb, M. and Kantorovich, S. (2017). Dilution effects on combined magnetic and electric dipole interactions: A study of ferromagnetic cobalt nanoparticles with tuneable interactions. J. Chem. Phys., 147 (8). MELVILLE: AMER INST PHYSICS. ISSN 1089-7690

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Abstract

Improved understanding of complex interactions between nanoparticles will facilitate the control over the ensuing self-assembled structures. In this work, we consider the dynamic changes occurring upon dilution in the self-assembly of a system of ferromagnetic cobalt nanoparticles that combine magnetic, electric, and steric interactions. The systems examined here vary in the strength of the magnetic dipole interactions and the amount of point charges per particle. Scattering techniques are employed for the characterization of the self-assembly aggregates, and zeta-potential measurements are employed for the estimation of surface charges. Our experiments show that for particles with relatively small initial number of surface electric dipoles, an increase in particle concentration results in an increase in diffusion coefficients; whereas for particles with relatively high number of surface dipoles, no effect is observed upon concentration changes. We attribute these changes to a shift in the adsorption/desorption equilibrium of the tri-n-octylphosphine oxide (TOPO) molecules on the particle surface. We put forward an explanation, based on the combination of two theoretical models. One predicts that the growing concentration of electric dipoles, stemming from the addition of tri-n-octylphosphine oxide (TOPO) as co-surfactant during particle synthesis, on the surface of the particles results in the overall repulsive interaction. Secondly, using density functional theory, we explain that the observed behaviour of the diffusion coefficient can be treated as a result of the concentration dependent nanoparticle self-assembly: additional repulsion leads to the reduction in self-assembled aggregate size despite the shorter average interparticle distances, and as such provides the growth of the diffusion coefficient. Published by AIP Publishing.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Hod, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Dobroserdova, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Samin, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Dobbrow, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schmidt, A. M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Gottlieb, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kantorovich, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-221421
DOI:	10.1063/1.4995428
Journal or Publication Title:	J. Chem. Phys.
Volume:	147
Number:	8
Date:	2017
Publisher:	AMER INST PHYSICS
Place of Publication:	MELVILLE
ISSN:	1089-7690
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SYMMETRIC TOP MACROMOLECULES; FLUX-CLOSURE; TRIOCTYLPHOSPHINE OXIDE; FERROFLUIDS; PARTICLES Multiple languages Chemistry, Physical; Physics, Atomic, Molecular & Chemical Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/22142