Controlled synthesis and self-assembly of dendrite patterns of Fe3O4 nanoparticles.

A method for the growth and self-assembly of Fe(3)O(4) nanoparticles that is template assisted, as well as gas diffusion and surface tension controlled, has been developed at room temperature. Well-defined dendrite patterns of Fe(3)O(4) nanoparticles were obtained upon ion (Fe(3+)/Fe(2+)) entrapment in a polyethylene glycol solution followed by NH(3) gas exposure on the surface of an aqueous solution on the glass substrate. During the formation of Fe(3)O(4) nanoparticles, the diffusion of volatile NH(3) limits the hydrolysis rate of the molecular precursor and catalyzes slow formation. The template and surface tension also provided significant driving forces to promote the formation of dendrite patterns and influence the nature of the pattern. The Fe(3+)/Fe(2+) concentration was varied in order to see the affects on the template molecular weight. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and SQUID measurements were used to characterize the final product. The derived patterned structure can be tailored by a simple combination of the physical and chemical procedure, which provides a new opportunity for obtaining a controllable pattern of nanoparticles.