Open AccessMagnetic Particle Self-Assembly at Functionalized Interfaces
Author(s) -
Apurve Saini,
Katharina TheisBröhl,
Alexandros Koutsioubas,
Kathryn Krycka,
J. A. Borchers,
Max Wolff
Publication year - 2021
Publication title -
langmuir
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.042
H-Index - 333
eISSN - 1520-5827
pISSN - 0743-7463
DOI - 10.1021/acs.langmuir.0c03235
Subject(s) - octadecyltrichlorosilane , materials science , triethoxysilane , ferrofluid , silicon , monolayer , wetting , magnetic nanoparticles , chemical engineering , contact angle , wafer , layer (electronics) , substrate (aquarium) , nanoparticle , particle (ecology) , nanotechnology , magnetic field , composite material , optoelectronics , oceanography , physics , quantum mechanics , geology , engineering
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.