Template assisted electrostatic Au nanoparticle assembly

Abstract

Recently, template-assisted convection driven assembly has shown that with the right combination of template structure and size, individual nanoparticles can be assembled into pre-patterned templates. Here, we present a method to enhance convection driven nanoparticle assembly on structural templates by the application of an electrostatic field between the substrate and the electrode. Various trenches and square well arrays were patterned in 150 nm thick PMMA using electron beam lithography. Solution containing high density of 20nm diameter Au nanoparticles was placed on the patterned surface and 1~3 V was applied between the electrode and the substrate to initiate electrophoresis. For 80 x 80 nm2 square well array, the average density of Au nanoparticle per well was 4.5 (50% surface coverage). However, for 40 x 40 nm2 square well array, the majority (70%) of wells were filed by a single Au nanoparticle which we attribute to electrostatic repulsion.