Arrays of magnetic nanoparticles capped with alkylamines

Abstract

Magnetic metal and metal oxide nanoparticles capped with alkylamines have been synthesized and characterized by transmission electron microscopy, X-ray diffraction, energy dispersive X-ray analysis and magnetization measurements, Core-shell Pd-Ni particles with composition, Pd561Ni3000, (diameter similar to3.3 nm) are superparamagnetic at 5 K and organize themselves into two-dimensional crystalline arrays. Similar arrays are obtained with Pd561M3000H1500 nanoparticles containing an additional Pd shell. Magnetic spinel particles of gamma-Fe2O3, Fe3O4 and CoFe2O4 of average diameters in the 4-6 nm range coated with octylamine are all supermagnetic at room temperature and yield close-packed disordered arrays. Relatively regular arrays are formed by dodecylamine-capped Fe3O4 nanoparticles (similar to8.6 nm diameter) while well-ordered hexagonal arrays were obtained with octylamine-covered Co3O4 nanoparticles (similar to4.2 nm diameter).