A solution-phase approach has been developed for the large-scale synthesis of metal nanostructures with well-defined shapes in the presence of a polymeric surfactant, i.e., poly(vinyl pyrrolidone) (PVP). As a demonstration, nanowires and nanocubes of silver have been synthesized through a modified polyol process that involved the reduction of silver nitrate with ethylene glycol heated at 160°C. Both reactant concentrations and the molar ratio between PVP and silver nitrate played critical roles in determining the shape and dimension of the final products. Relatively high concentrations of silver nitrate were favorable for the formation of silver nanocubes, while nanowires or nanorods became the dominated products if the concentration of silver nitrate was below 0.1 mM. The edge lengths of nanocubes and the lateral dimensions of nanowires synthesized with this method could be varied in the ranges of 50-180 nm and 30-60 nm, respectively. Nanocubes were single crystals mainly bounded by {100} facets. Each nanowire/nanorod, however, was characterized with a pentagonal cross-section, five straight side edges, and five flat side surfaces. It is believed that these silver nanostructures with well-defined shapes should find uses in a number of areas such as electronics, photonics, and catalysis.
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