High-yield preparation of vertically aligned gold nanorod arrays via a controlled evaporation-induced self-assembly method

Vertically aligned gold nanorod arrays have attracted much attention recently due to their fascinating optical properties. In this study, a simple two-step method was developed to create standing gold nanorod arrays. In the first step, the nanorod droplets were incubated with 200 mu L of water in a sealed Petri dish for 24 h, resulting in contracted droplets without forming a coffee-ring structure. After removing the water, the contracted droplets were allowed to dry for another 36-48 h at 25 degrees C. The standing gold nanorod arrays were successfully synthesized by the two-step method using gold nanorods with an aspect ratio of 2.0 as building blocks. Results show that nearly all the nanorods (similar to 95%) were vertically aligned on the silicon surface except a very small amount of nanorods near the pinned edge. Standing gold nanorod arrays were also created by the two-step method using gold nanorods with a higher aspect ratio (similar to 3.4). This novel method does not need to modify gold nanorods with thiolated ligands, synthesize strictly monodispersed gold nanorods, or use highly concentrated gold nanorod solutions for the assembly. The new approach could be used as a reproducible, high-yield, and simple route to fabricate vertically aligned gold nanorod arrays.