Preparation of Gold Cluster Crystals and Their Electronic State

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The main object of this research is 1) To prepare gold nanoparticles in the size range from 1 to 3 nm, which is in the quantum size regime,2) To crystallize these nanoparticles to realize macroscopically quantum size effect and to clarify its magnetic properties. With our technique, it is possible to regulate the core size of a single nanoparticle, the thickness of insulator barrier height, interaction among substituted residues. Hence it is possible to prepare a new type superstructures different from those manufactured by conventional deposition techniques because of a new approach. We can expect a characteristic feature such as a magic number in cluster molecules whose sizes are much smaller than a nanoparticle.. Through this project, we also expect to get detailed solid state properties in these cluster materials.We have applied a vapor diffusion method to prepare a quality particle crystal of mercaptosuccinic acid modified silver particles as an test material to demonstrate the ef … More fectiveness of this method. Even starting wide size distribution with 40% size width, we have succeeded in preparing a good particle crystal without size separation. We are now planning to apply this method to get a gold nanoparticle crystal. We have started measurement of transport properties of deposited film of gold nanoparticle to characterize its electronic properties from room temperature down to 20 K. The deposited film revealed characteristic temperature dependence in the conductivity showing the metallic character with slightly small temperature coefficient. We have also found that the same film was capable to measure optical absorption experiment that means this film is somewhat transparent even though the thickness of the film. A more comprehensive experiment is now under going.A particle crystal that has pentagonal symmetry was obtained with acetyl GTR ligand. The crystal size is in the order of micron meter. This is a unique substance in a group of superlattice of nanoparticles. The next target of our project is to crystallize more small particles in the regime of cluster with a sharp size distribution as if it were molecular materials. To realize this object, we are now developing a new technique which uses less than a milligram sample powders to get crystal and crystallize within a capillary. Less