The synthesis of nanoparticles, characterized by a low size distribution, is a new challenge in solid-state chemistry. Due to their small size, nanoparticles exhibit novel materials properties that differ considerably from those of the bulk solid state. In this emerging field, finely divided magnetic nanoparticles are desirable owing to their broad range of applications, especially in data storage devices and sensors. A great deal of work on large magnetic nanoparticles has been carried out, [2] but, although the magnetic properties of isolated atoms are well understood, there are still questions about the development of magnetic order on a macroscopic scale. The creation of perfect nanometer-scale magnetic crystallites identically replicated with long-range order in a state that can be manipulated and understood in terms of a pure macromolecular substance is an ultimate challenge in present materials research and could help us to understand the formation of ferromagnetism. To develop this application, it is crucial to be able to control the spatial arrangement of these nanoparticles in 2D or 3D arrays.
Recently, in our laboratory spontaneous arrangement of particles either into monolayer organized hexagonal networks or into 3D face-centered cubic (fcc) arrangements was observed with silver sulfide and silver nanosized clusters. [5Β±8] Similar arrangements with metal particles such as gold or silver [9Β±11] and CdSe semiconductors have been reported elsewhere.
Here, we report, for the first time, self-organization of magnetic cobalt nanoparticles into 2D superlattices. The magnetic properties of isolated and organized particles are compared.
Reverse micelles are water in oil droplets stabilized by a monolayer of surfactant (e.g., sodium bis(2-ethylhexyl)sulfosuccinate, usually called Na(AOT)). The diameter of the