Preparation of self-assembled cobalt nanocrystal arrays

Processing of self-assembled magnetic nanocrystals has vitally scientific and technological interests. In this paper, three different kinds of self-assemblies of cobalt nanocrystals were processed using particles processed by thermal decomposition of cobalt carbonyl in toluene. In case 1, two-dimensional self-assembly of cobalt nanocrystals with an average particle size of 9.2 nm and polydispersity of 9% has been formed. In case 2, macroscopic whisker structures composed of self assembled cobalt nanocrystals (with an average size of 8 nm) were formed during the thermal decomposition under an externally applied magnetic field. The whiskers can be aligned in the longitudinal axis direction during drying using an external magnetic field. In case 3, one-dimensionally ordered, densely packed self-assemblies have also been prepared using cobalt nanocrystals with irregular shape and larger particle sizes (10-20 nm). The formation of these different structures is attributed to the magnetic properties of cobalt particles with different sizes. (C) 1999 Acta Metallurgica Inc.