Cobalt ferrite–silica core–shell colloids: a magnetic Yukawa system

Abstract

Colloidal core-shell particles consisting of a magnetic cobalt ferrite core surrounded by a silica shell are prepared via precipitation and a subsequent modified Stöber synthesis. The resulting particles with narrow size distribution interact due to weakly acidic surface groups at the silica shell via a screened Coulomb or Yukawa potential in addition to the magnetic dipole-dipole interaction of the magnetic cores.The structural characterization of the particles is done by transmission electron microscopy and small-angle X-ray scattering (SAXS), and the potential parameters of the electrostatic monopole and magnetic dipole-dipole interactions are determined by laser Doppler electrophoresis and magnetogranulometry, respectively.Owing to the interaction potential, the particles self-organize to a liquid-like ordered structure as determined by SAXS. The magnetic dipole-dipole interaction becomes evident from the anisotropic scattering pattern in the presence of an external magnetic field.

SDS-PAGE as a Tool for Hydrodynamic Diameter-Dependent Separation of Quantum Dots

“…Several analytical techniques, namely laser dynamic light scattering (DLS), laser Doppler electrophoresis, capillary electrophoresis and gel electrophoresis are suitable to characterize the nanocolloids [13][14][15][16][17]. Optical characterization of QDs is usually provided by UV-VIS and photoluminescence spectroscopy, which offers fast, nondestructive and contactless option.…”

Surface engineering of Co and FeCo nanoparticles for biomedical application

“…of research groups to coat single iron oxide and cobalt ferrite nanoparticles [69][70][71][72][73] and was extended recently to form silica shells on nanoparticles of noble metals such as silver and gold [74][75][76][77]. However, compared to these noble metals, Co is more easily oxidized under the reaction conditions (free heat of formation, e.g., Ag 2 O −31.1 kJ mol −1 , CoO −237.9 kJ mol −1 , Co 3 O 4 −891.0 kJ mol −1 ).…”

Coherent X-rays as a new probe for the investigation of the dynamics of opaque colloidal suspensions

“…We used spherical core-shell particles consisting of a cobalt ferrite magnetic core and a silica shell dispersed in water. The synthesis of the sample is described elsewhere [5,6]. An XPCS investigation was performed in the small angle regime in combination with a small angle X-ray scattering (SAXS) study to elucidate the static behavior of the sample.…”