Web Release Date: October 27,
Frequency Dependence of Gold Nanoparticle Superassembly by Dielectrophoresis
and
Department of Electrical and Computer Engineering, and Department of Chemical Engineering and Materials Science, University of California-Davis, Davis, California 95616, and The MicroInstruments and Systems Laboratory (MISL), Laboratory for Surface Science and Technology (LASST), University of Maine, Orono, Maine 04469
Received May 19, 2007
In Final Form: August 6, 2007
Abstract:
Dielectrophoresis is an effective method for capturing nanoparticles and assembling them into nanostructures. The frequency of the dielectrophoretic alternating current (ac) electric field greatly influences the morphology of resultant nanoparticle assemblies. In this study, frequency regimes associated with specific gold nanoparticle assembly morphologies were identified. Gold nanoparticles suspended in water were captured by microelectrodes at different electric field frequencies onto thin silicon nitride membranes. The resultant assemblies were examined by transmission electron microscopy. For this system, the major frequency-dependent influence on morphology appears to arise not from the Clausius-Mossotti factor of the dielectrophoretic force itself, but instead from ac electroosmotic fluid flow and the influence of the electrical double layer at the electrode-solution interface. Frequency regimes of technological interest include those forming one-dimensional nanoparticle chains, microwires, combinations of microwires and nanoparticle chains suitable for nanogap electrode formation, and dense three-dimensional assemblies with very high surface area.
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