| Research in the past decade has shown that the unique electrical, optical and magnetic properties of nanocrystals are largely caused by the quantum confinement effect and the surface/interface effect.; Application of these unique properties, however, are still hindered by our ability to create bulk quantities of nanomaterials with well defined size, morphology and spatial arrangement. Compared with lithographic techniques, syntheses of nanocrystals by wet chemistry has the advantage of making large quantities in a much simpler manner with a lower cost, both of which are crucial to industrial applications.; Nevertheless, control of size distribution and morphology of nanocrystals and their superlattice arrangement remains a challenge. In this work, we studied cobalt nanocrystals and gold nanocrystals prepared by an inverse micelle technique. In the cobalt system, we discovered a germ-growth process to control the particle size and a process to form nanocrystal clusters by varying the reduction temperature. Magnetic properties of different sizes of single crystals and different sizes of clusters were characterized by a Superconducting Quantum Interference Device (SQUID) magnetometer. In the gold work, we found that by using a novel digestive ripening process and a temperature induced size segregation process, we can narrow the size distribution of the as prepared colloid significantly. Three dimensional superlattice structures of the uniform size nanocrystals were then formed directly in the super-satured colloid by nucleating the colloid below the phase boundary. Optical and thermal properties of both single nanocrystals and nanocrystal superlattice (NCS) structures were studied. |
