P JOHN THOMAS, P SARAVANAN, G U KULKARNI   and C N R RAO*

Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560 064, India

* for correspondence: cnrrao@jncasr.ac.in

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, Pd₅₆₁ Ni₃₀₀₀, (diameter ~3.3 nm) are superparamagnetic at 5 K and organize themselves into two-dimensional crystalline arrays. Similar arrays are obtained with Pd₅₆₁Ni₃₀₀₀Pd₁₅₀₀ nanoparticles containing an additional Pd shell. Magnetic spinel particles of g-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 (~8.6 nm diameter) while well-ordered hexagonal arrays were obtained with octylamine-covered Co₃O₄ nanoparticles (~4.2 nm diameter). 

Keywords:  Self-assembly; magnetic nanoparticles..

Pacs Nos.  81.16.D; 81.07.Bc; 81.16.B