| 1. |
- Mikhaylova, Maria, et al.
(författare)
-
Superparamagnetism of magnetite nanoparticles : Dependence on surface modification
- 2004
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 20:6, s. 2472-2477
-
Tidskriftsartikel (refereegranskat)abstract
- Superparamagnetic iron oxide nanoparticles (SPION) with an average particle diameter of 6 nm are prepared by controlled chemical coprecipitations. Colloidal suspensions of noninteracting SPION, where the surface has been modified with three different types of biocompatible substances, namely, starch, gold (An), and methoxypoly(ethylene glycol) (MPEG) have been fabricated via three different techniques. Starch-coated SPION are prepared by coprecipitation in a polymeric matrix, Au-coated SPION are fabricated by the microemulsion method, and MPEG-coated SPION are prepared using the self-assembly approach. The magnetic nanoparticles form a core-shell structure, and the magnetic dipole-dipole interactions are screened by a layer of coating agents. The amounts of coating agents and SPION are indirectly calculated from the thermogravinietric analysis and superconducting quantum interference device measurements by assuming passive oxidation on the surface of the SPION, and the other conditions do not influence the measurements. The dependency of the spectral characteristics of Mossbauer spectroscopy as a function of an external magnetic field H-ext is measured to investigate the effect of dipole-dipole screening of the different coating layers on the SPION. Uncoated SPION show a stable magnetic moment under H-etx and the superparamagnetic (SPM) fraction transforms to a ferrimagnetic state. Starch and Au-coated SPION retain the SPM fraction according to Mossbauer spectroscopy and magnetization measurements. MPEG-coated SPION show hyperfine magnetic structure without the quadrupole effect with increasing the value of the blocking temperature.
|
|
| 2. |
- Mikhaylova, Maria, et al.
(författare)
-
The effect of biocompatible coating layers on magnetic properties of superparamagnetic iron oxide nanoparticles
- 2004
-
Ingår i: Hyperfine Interactions. - 0304-3843 .- 1572-9540. ; 156:1, s. 257-263:156/157, s. 257-263
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of the surface coating on the magnetic properties of superparamagnetic iron oxide nanoparticles (SPION) with 8 nm in size has been studied. Four different biocompatible coating layers are considered: poly L,L-lactic acid (PLLA), poly epsilon-caprolactone (PCL), bovine serum albumin (BSA) and gold. The presence of coating layer on the surface of SPION is confirmed by FT-IR spectroscopy. Mossbauer spectroscopy and magnetic susceptibility measurements show that for uncoated SPION and Au@SPION the superparamagnetic fraction is retained. The formation of clusters in the case of BSA@SPION and chain-like structure for PCL@SPION and PLLA@SPION increase the inter-particle interactions resulting in hyperfine magnetic structure observed in the Mossbauer spectra at ambient temperature.
|
|
