Fabrication of gold nano- and microstructures in ionic liquids - A remarkable anion effect

Au nano- and microstructures such as polyhedral crystals, large single-cryst. nanoplates, hollow trapeziform crystals, holey polyhedra, and dendrites were produced via microwave heating of HAuCl4·4H2O in a variety of ionic liqs. (ILs) in the absence of capping agents (polymers or surfactants) or addnl. reducing agents. The influence of the IL anions and cations on the topol. (size, shape, etc.) of Au materials was studied. The anions of the ILs control the topol. of materials, whereas the cations used in the expts. exert less influence. Also the HAuCl4 concn., reaction temp., and heating method are key parameters that help to control the topol. structures of the Au materials. For example, the thickness of the large single-cryst. nanoplates could be adjusted from 16 to 320 nm by varying the HAuCl4 concn. and reaction temp. This easy synthetic approach to Au nano- and microstructures is a seedless, 1-step, fast, template-free route that shows good reproducibility and may be further developed to produce other types of metal nanostructures that satisfy specific applications.