Synthesis of a quantum dot superlattice using molecularly linked metal clusters

摘要

We report on a synthesis strategy for fabrication of close-packed planar arrays of nanometer-diameter metal clusters that are covalently linked by organic molecular wires. The clusters are gold single crystals, each encapsulated by a monolayer of dodecanethiol molecules. A colloidal suspension of these clusters in mesitylene is spread onto a substrate. On evaporation of the solvent the clusters self-assemble to form a close-packed monolayer. This cluster network is then crosslinked by immersing the substrate in an acetonitrile solution containing a conjugated di-isonitrile molecule (1,4-di(4-isocyanophenylethynyl)2-ethylbenzene). Transmission electron micrographs of the cluster arrays before and after immersion indicate that the diisonitrile molecules partially substitute for the dodecanethiol molecules to produce a crosslinked network of clusters joined by the di-isonitrile. The interesting feature of this network is that it represents a 2D superlattice of metal quantum dots coupled by well defined tunnel junctions. When the gold clusters used to synthesize the network have diameters less than approximately 2 nm, it is predicted that this superlattice will exhibit Coulomb blockade effects at room temperature.