ZnO nanorods were prepared at relatively low temperatures by homogeneous precipitation from zinc nitrate and urea in a water/ethylene glycol mixture. Crystal size and morphology are controlled by growth time and solvent composition. We observed a strong correlation between nanocrystals’ size/morphology and their optoelectronic defect-related properties. Smaller crystallites exhibited intense deep-defect luminescence and enhanced emission related to near-surface excitonic recombination. Longer growth times lead to formation of well-defined nanorods with hexagonal symmetry exhibiting reduced defect emission.

Homogeneous ZnO/polymethyl methacrylate (PMMA) nanocomposites were prepared by incorporating ZnO nanoparticles synthesized in various diols into a PMMA matrix by the free-radical bulk polymerization. Room temperature photoluminescence spectra of the as-grown and PMMA-embedded ZnO nanoparticles exhibit an excitonic band-gap emission at 3.3 eV, a near band-gap emission at ∼3.1 eV and a broad defect band centered at ∼2.4 eV. Relative intensity of the defect versus band-gap luminescence depends on the parameters of ZnO preparation as well as the average particle size. However, PMMA-embedded particles produce a much stronger excitonic luminescence, whereas the ratio of the 3.1 to 2.4 eV remains approximately constant. There is no indication of random lasing threshold pointing to the ZnO/PMMA interfacial origin of the enhanced band-gap emission.

Er 3þ ions, both with and without a germanium (Ge) sensitizer layer, have been introduced onto the surface of ZnO tetrapod structures. Such structures, characterized by electron microscopy and X-ray diffraction, are found to emit at both the UV/ visible and near-infrared as a consequence of the presence of ZnO/Er 3þ . The presence of selected absorption features in the visible luminescence spectra suggests energy transfer from ZnO to Er 3þ ions in the doped materials. The introduction of Ge onto the tetrapod surface enhances the intensity of Er 3þ photoluminescence significantly with a corresponding blue shift of 11 nm in the emission maxima.