Monodisperse Magnetizable Composite Silica Spheres with Tunable Dipolar Interactions
- 15 September 2005
- journal article
- research article
- Published by American Chemical Society (ACS) in Langmuir
- Vol. 21 (21), 9412-9419
- https://doi.org/10.1021/la051127a
Abstract
We demonstrate that magnetic particles of maghemite (γ-Fe2O3) and cobalt ferrite (CoFe2O4) can be irreversibly attached to colloidal silica that is grafted with 3-mercaptopropyl(trimethoxy)silane (followed by the controlled growth of a silica layer) to obtain stable dispersions of monodisperse colloidal silica spheres that contain a dense shell of ferrite particles at an adjustable distance from the sphere surface. Magnetization of the ferrite shell induces a large dipole moment, and adjusting the thickness of the outer silica layer enables one to tune the contact attraction. This novel type of magnetizable silica colloid exhibits structure formation in a homogeneous field that varies from isotropic distributions to elongated dipolar chains.Keywords
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