Frequency Dependence of Gold Nanoparticle Superassembly by Dielectrophoresis

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.

Electro-orientation and electrorotation of metal nanowires

“…However, despite the growing interest in the use of metal nanowires in nanotechnology the fundamental electrokinetic properties of metallic particles are poorly understood. The ac electrokinetic behavior of metal particles in electrolytes is commonly mistakenly modeled by considering the metal particle to be an isotropic lossy dielectric characterized by a finite conductivity and permittivity suspended in an electrolyte [4][5][6][7]. When a metal particle suspended in an electrolyte is subjected to an electric field, an electrical double layer is induced around the particle and this dominates both the dielectric properties and the electrokinetic behavior of the particle at low frequencies.…”

Nanopore with transverse nanoelectrodes for electrical characterization and sequencing of DNA

“…Upon closer investigation, the shifts are "quantized" at roughly regular admittance intervals. Based on previously reported studies of the dielectrophoretic attraction of gold nanoparticles [29][30][31], a model was developed that explains these shifts. During AC excitation of the nanoelectrodes, nanoparticles are attracted to the high field edge of the electrodes and form a weak association that effectively extends the nanoelectrodes, decreases the gap between electrodes, and increases the admittance (Fig.…”

Low-frequency dielectrophoretic response of a single particle in aqueous suspensions

“…4,[15][16][17] Although some success has been achieved to account for the effect of the particle sizes, a significant discrepancy lies between the measured DEP crossover frequency and the relaxation frequency predicted by Schwarz theory. 4,10,18,19 To investigate the diffusion theory by Schwarz and its applicability in explaining experimental data, we apply the technique of optical tweezers-based DEP force spectroscopy on a single colloidal particle. In contrast to particle image velocimetry, where the macroscopic behavior of a particle ensemble is studied, 18,20 single-particle force detection in conjunction with amplitude modulation and lock-in detection techniques allows us to avoid the complication effects due to electrokinetic mechanisms, such as electrophoresis and AC electroosmosis, 19,[21][22][23] so that only the effects due to DEP are measured.…”