Dilution effects on combined magnetic and electric dipole interactions: A study of ferromagnetic cobalt nanoparticles with tuneable interactions

Autor(en)

M. Hod, A. B. Dobroserdova, S. Samin, C. Dobbrow, A. M. Schmidt, M. Gottlieb, S. Kantorovich

Abstrakt

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.

Organisation(en)

Computergestützte Physik und Physik der Weichen Materie

Externe Organisation(en)

Ben Gurion University of the Negev, Ural Federal University, Utrecht University, Universität zu Köln, Daimler AG

Journal

Journal of Chemical Physics

Band

147

Anzahl der Seiten

9

ISSN

0021-9606

DOI

https://doi.org/10.1063/1.4995428

Publikationsdatum

08-2017

Peer-reviewed

Ja

ÖFOS 2012

104017 Physikalische Chemie, 103006 Chemische Physik

Schlagwörter

ASJC Scopus Sachgebiete

Allgemeine Physik und Astronomie, Physical and Theoretical Chemistry

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/5c674d7c-0d34-4b0f-8a0b-63b45fbec55e