Mechanical-Agitation-Assisted Growth of Large-Scale and Uniform ZnO Nanorod Arrays within 3D Multichannel Monolithic Substrates

The assembly of nanomaterials with accurate morphology, size, and orientation control in 3D space-confined structures is crucial for the practical and widespread application of nanotechnology. Using a green and low-cost hydrothermal method, we successfully synthesized uniformly distributed ZnO nanorod (NR) arrays throughout commercially available 3D multichannel honeycomb cordierite substrates on a large scale. Through mechanical agitation such as ultrasonic vibration during dip-coating and magnetic stirring during hydrothermal processing, the mass transport of precursors was enhanced within 3D confined channels so as to enhance the uniformity of nanostructure seeding and nanoarray growth on the monoliths. Selected mechanical agitation parameters such as the stirring rate and the geometry of the monolithic channels were found to be closely relevant to the controlled growth of nanostructures within different-sized 3D channeled substrates, as suggested by computational fluid dynamics analysis. Furthermore, other growth parameters such as temperature, precursor concentration, and ZnO base growth were also found to be relevant to the control of the size, morphology, and uniformity of as-grown ZnO nanorod arrays in 3D confined spaces. The understanding developed here could be extended to different materials systems and growth substrates (reactors) with 3D confined spaces.