Rapid fabrication of ZnO nanorod arrays with controlled spacing by micelle-templated solvothermal growth

We present a facile method for the synthesis of nanorod arrays over large areas with fine control over the average rod-rod spacing. Block copolymer micelles are used to template solvothermal synthesis of ZnO nanorods by preferentially enabling reactant diffusion through the micelle cores to an underlying seed layer. The distance between nanorod centers is defined by the micelle number density which is in turn controlled by the molecular weight of the block copolymer, and the block copolymer concentration in a templating film. We demonstrate the ability to control the resulting nanorod number density from ∼100 μm(-2) down to ∼10 μm(-2) with high fidelity. Correspondingly, the distance between nanorod surfaces was varied from ∼60 nm to 230 nm. The method developed here provides a viable approach for rapidly fabricating large-area nanostructured electrodes comprised of nanorod arrays with controlled geometries. The ability to tailor nanorod spacing over a broad range suggests applications in photovoltaics and sensors based on optical resonances can be readily addressed.