Site-specific synthesis of ZnO nanocrystalline networks via a hydrothermal method

ZnO nanocrystalline networks (NCNWs) consisting of percolating nanocrystals with irregular shape and size were synthesized using Al seed layers in a hydrothermal process. Various thicknesses of Al films were used to assess the effects of film thickness on the formation of ZnO NCNWs; the coverage and size of the ZnO nanocrystals increased with an increasing Al film thickness. In addition, by exploiting the seed layer-dependent crystal growth behaviors, two distinctly different ZnO nanostructures, nanorods on ZnO seed and NCNWs on Al seed, could be selectively achieved on the same substrate under the same growth conditions. Spectrally- and spatially-resolved investigations of these two ZnO nanostructures were performed using cathodoluminescence, which provided a significant opportunity to study the effect of the nanostructures on the luminescent characteristics. The ZnO NCNWs have an extremely high surface to volume ratio and sufficient inter-space, which enabled the conversion of the surface property from hydrophilic to superhydrophobic.