Controlling the concentration of gold nanorods during their dielectrophoresis-assisted deposition

Gold nanorods (AuNRs) have attracted great interest due to their excellent plasmonic properties which makes them a promising candidate for many applications. However, most of the applications require control over the position and concentration of nanorods (NRs) by processes that are fast, reliable and scalable. The focus of this work is to study the effects of variation of various parameters, such as applied voltage, frequency, solvents and drying time on the concentration of dielectrophoresis (DEP) -assisted deposition of AuNRs. We have seen that the concentration of AuNRs within the electrodes can be considerably increased by increasing the applied voltage and deposition time, and by choosing a more volatile solvent. Furthermore, the applied frequency also strongly influences the deposition of AuNRs. At lower frequencies, the electro-osmotic flows drag AuNRs to the top of electrodes, while at higher frequencies NRs are deposited close to the electrode edge where the electric field and the field gradient are maximum. We have also carried out simulations using the finite element method to generate the electric field patterns for coplanar electrodes. Our results provide insight into ways in which the concentration of AuNRs can be controlled during DEP-assisted deposition. (paper)