TY  - JOUR
AU  - Saini, Apurve
AU  - Theis-Bröhl, Katharina
AU  - Koutsioumpas, Alexandros
AU  - Krycka, Kathryn L.
AU  - Borchers, Julie A.
AU  - Wolff, Max
TI  - Magnetic Particle Self-Assembly at Functionalized Interfaces
JO  - Langmuir
VL  - 37
IS  - 14
SN  - 0743-7463
CY  - Washington, DC
PB  - ACS Publ.
M1  - FZJ-2021-05476
SP  - 4064 - 4071
PY  - 2021
AB  - 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.
LB  - PUB:(DE-HGF)16
C6  - 33797254
UR  - <Go to ISI:>//WOS:000640891400003
DO  - DOI:10.1021/acs.langmuir.0c03235
UR  - https://juser.fz-juelich.de/record/903843
ER  -