title: Light-induced covalent immobilization of monolayers of magnetic nanoparticles on hydrogen-terminated silicon.
abstract: Specifically tailored ω-alkenyl-1-carboxylic acids were synthesized for use as surfactants in the single-step preparation of manganese ferrite (MnFe2O4) nanoparticles (NPs). Monodisperse manganese ferrite NPs terminated with ω-alkenyl moieties were prepared via a one-pot reaction at high temperature without the need of ligand exchange. Using this approach, simple adjustment of the rate of heating allowed precise tuning of the size of the nanoparticles, which were characterized in bulk form by transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD). These surfactant-coated magnetic nanoparticles were then deposited onto hydrogen-terminated silicon(111) wafers and covalently anchored to the surface by UV-initiated covalent bonding. Analysis by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) confirmed that the UV treatment led to covalent immobilization of the NPs on the silicon surface with a consistent packing density across the surface. The magnetic properties of the stable, surface-bound nanoparticle arrays were characterized using a superconducting quantum interference device (SQUID) magnetometer. The materials and methods described here are being developed for use in bit-patterned ultrahigh density magnetic recording media and nanoscale biomagnetic sensing.
authors.affiliation: Department of Chemistry, University of Houston, 4800 Calhoun Road, Houston, Texas 77204, USA.
authors.forename: Gyu
authors.initials: G
authors.lastname: Leem
authors.forename: Shishan
authors.initials: S
authors.lastname: Zhang
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Jamison
authors.forename: Eduard
authors.initials: E
authors.lastname: Galstyan
authors.forename: Irene
authors.initials: I
authors.lastname: Rusakova
authors.forename: Bernd
authors.initials: B
authors.lastname: Lorenz
authors.forename: Dmitri
authors.initials: D
authors.lastname: Litvinov
authors.forename: T Randall
authors.initials: TR
authors.lastname: Lee
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D005290:Ferric Compounds / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D008027:Light; D008345:Manganese / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010777:Photochemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D013501:Surface-Active Agents; D008345:Manganese; D012822:Silicon Dioxide; D006859:Hydrogen