Assembly of Gold Nanowires on Gold Nanostripe Arrays: Simulation and Experiment

Nanowires (NWs) have a large aspect ratio and large available surface area, which have made them a potential platform for applications in biosensors as well as electronic/optic and power storage devices. However, the realization of many of these applications requires the wires to be positioned and oriented through an assembly process. Hence, it is essential to develop assembly strategies and techniques to achieve a variety of desired structures. In this work, we explored NW assembly using a patterned NW-substrate interaction. Experimentally, silica-coated Au nanowires (diameter of 340 nm, lengths of 2.4 and 4.4 μm, 30 nm SiO₂ shell) are allowed to self-assemble onto microfabricated Au features that create a series of "stripes" on a glass substrate (feature height of 50-200 nm; widths of 2.4, 4.5, and 4.8 μm). We observe a rich variety of patterns, with NWs concentrated atop the Au features and oriented perpendicular and diagonal to the stripe axes. We develop a model of this system by considering the relevant van der Waals and electrostatic interactions among NWs and between the NWs and stripes. Monte Carlo simulations of the assembly were performed based on this model, and good agreement with the experiment was achieved. An interesting finding from this work is that extra repulsion at the NW ends plays an important role in determining whether NWs order with their long axes parallel or perpendicular to the Au stripe axis. The simplicity of our approach makes this platform a promising way to achieve more elaborate nanoparticle assemblies in the future.