Claesson E M, Philipse A P
Van't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
Langmuir. 2005 Oct 11;21(21):9412-9. doi: 10.1021/la051127a.
We demonstrate that magnetic particles of maghemite (gamma-Fe(2)O(3)) and cobalt ferrite (CoFe(2)O(4)) 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.
我们证明，磁赤铁矿（γ-Fe₂O₃）和钴铁氧体（CoFe₂O₄）的磁性颗粒可以不可逆地附着在接枝了3-巯基丙基（三甲氧基）硅烷的胶体二氧化硅上（随后可控生长二氧化硅层），从而获得单分散胶体二氧化硅球的稳定分散体，这些球体含有一层铁氧体颗粒致密壳层，与球体表面保持可调节的距离。铁氧体壳层的磁化会诱导出一个大的偶极矩，通过调节外部二氧化硅层的厚度，可以调节接触吸引力。这种新型的可磁化二氧化硅胶体在均匀场中会形成结构，从各向同性分布到拉长的偶极链不等。
