%0 Journal Article
%A Saini, Apurve
%A Theis-Bröhl, Katharina
%A Koutsioumpas, Alexandros
%A Krycka, Kathryn L.
%A Borchers, Julie A.
%A Wolff, Max
%T Magnetic Particle Self-Assembly at Functionalized Interfaces
%J Langmuir
%V 37
%N 14
%@ 0743-7463
%C Washington, DC
%I ACS Publ.
%M FZJ-2021-05476
%P 4064 - 4071
%D 2021
%X 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, 15, and 25 nm, we extract density profiles from neutron reflectivity measurements. 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 a (3-aminopropyl)triethoxysilane functionalized surface. Less dense packing is reported for physisorption 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.
%F PUB:(DE-HGF)16
%9 Journal Article
%$ 33797254
%U <Go to ISI:>//WOS:000640891400003
%R 10.1021/acs.langmuir.0c03235
%U https://juser.fz-juelich.de/record/903843