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Magnetic Particle Self-Assembly at Functionalized Interfaces

Published

Author(s)

Apurve Saini, Katharina Theis-Brohl, Alexandros Koutsioubas, Kathryn L. Krycka, Julie Borchers, Max Wolff

Abstract

We study the assembly of magnetite nanoparticles in water-based ferrofluids in wetting layers close to silicon substrates with different functionalization without and with an out-of-plane magnetic field. For particles of nominal sizes 5 nm, 15 nm and 25 nm, we extract density profiles form neutron reflectivity measurement. We show that self-assembly is only promoted by a magnetic field if a seed layer is formed at the silicon substrate. Such a layer can be formed by chemisorption of activated N-hydroxysuccinimide ester-coated nanoparticles at an (3-aminopropyl)triethoxy silane functionalized surface. Less dense packing is reported for physisorbtion of the same particles at a piranha treated (strongly hydrophilic) silicon wafer and no wetting layer is found for a self-assembled monolayer of octadecyltrichlorosilane (strongly hydrophobic) at the interface. We show that once the seed layer is formed and under an out-of-plane magnetic field further wetting layers assemble. These layers become denser with time, larger magnetic fields, higher particle concentrations and larger moment of the nanoparticles.
Citation
Langmuir
Volume
37
Issue
14

Keywords

Magnetic nanoparticles, Self-assembly, Dipole interactions, Polarized neutron reflectivity, SANS

Citation

Saini, A. , Theis-Brohl, K. , Koutsioubas, A. , Krycka, K. , Borchers, J. and Wolff, M. (2021), Magnetic Particle Self-Assembly at Functionalized Interfaces, Langmuir (Accessed December 8, 2021)
Created April 12, 2021, Updated September 29, 2021