Solvent-controlled crystallization of zinc oxide nano(micro)disks

The effect of solvent composition on the growth of ZnO crystals has been investigated in water–ethanol solution system. Ethanol is found to effectively inhibit the crystal growth along the 〈0 0 0 1〉 direction, leading to the formation of thin disks. Hexagonal nanodisks and near-rounded microdisks have been grown in 1:1 (volume ratio) and 1:9 water–ethanol solutions, respectively. Transmission electron microscopy and selected area electron diffraction results show that the prepared hexagonal nanodisks have a single-crystal structure. In contrast, the near-rounded microdisks have a layer-by-layer structure, suggesting that crystals are grown by outward attachment. A strong sharp UV luminescence and a weak broad green-yellow emission in photoluminescence spectra indicate a high crystal quality of the prepared ZnO nano(micro)disks.