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Abstract: ZnO nanorods were fabricated by electrodeposition from solution with and without thulium precursors and characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, photoluminescence and time-resolved photoluminescence. In spite of the low incorporation of thulium into ZnO nanorods, both the morphology and the optical properties of the nanorods were affected by the presence of thulium. The light emitting diodes with ZnO nanorods with and without Tm have been demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: There is a considerable interest in studying organic/inorganic hybrid structures for various applications in optoelectronic devices. We have recently demonstrated fabrication of 3,4,9,10-perylenetetracarboxylicdiimide (PTCDI) nanostructures and hybrid PTCDI/ZnO nanorod structures and studied their optical properties, and we found that PTCDI nanoclusters exhibit significantly different light emission compared to PTCDI films. Since the emission spectrum of PTCDI nanoclusters exhibited dependence on the deposition substrate, we have studied the influence of ZnO nanorod growth method and post-growth annealing in oxygen atmosphere at different temperatures on the energy transfer to PTCDI nanostructures by photoluminescence measurements. Fabricated structures have been investigated using scanning electron microscopy and photoluminescence measurements, and the obtained results are discussed. [ABSTRACT FROM AUTHOR]

Abstract: In recent years, there has been increasing interest in ZnO nanostructures due to their variety of morphologies and availability of simple and low cost processing. While there are still unanswered questions concerning fundamental properties of this material, in particular those related to defects and visible luminescence lines, great progress has been made in synthesis methods and device applications of ZnO nanostructures. In this review, we will provide a brief overview of synthesis methods of ZnO nanostructures, with particular focus on the growth of perpendicular arrays of nanorods/nanowires which are of interest for optoelectronic device applications. Then, we will provide an overview of material properties of ZnO nanostructures, issues related to doping with various elements to achieve either p- or n-type conductivity. Doping to alter optical or magnetic properties will also be discussed. Then, issues related to practical problems in achieving good electrical contacts to nanostructures will be presented. Finally, we will provide an overview of applications of ZnO nanostructures to light-emitting devices, photodetectors and solar cells. [Copyright &y& Elsevier]

Abstract: Green defect emission is commonly observed in ZnO nanostructures. It is frequently attributed to oxygen vacancies and used to evaluate performance and study physical mechanisms in a variety of applications, such as gas sensing and photocatalysis. However, competing hypotheses have been proposed to explain green emission, which raises questions about the role of oxygen vacancies in sensing and photocatalytic processes. The major problem in correct experimental identification of defects in ZnO is the abundance of defects present, while theoretically there are problems with accurate calculation of a defect energy level in the gap. Thus, here we adopted a different approach and studied experimentally and theoretically the interaction of ZnO with different chemical substances (hydrogen and a silane-based molecule). Based on theoretical predictions and experimental results, we can conclude that green emission can likely be assigned to defect complexes, which may contain zinc vacancies. [Copyright &y& Elsevier]

Abstract: We have investigated the use of different cerium precursors for fabrication of Ce doped ZnO nanorods by electrodeposition. ZnO nanorods fabricated with different Ce precursors had similar morphology, but very different optical properties. The influence of annealing in oxygen at different temperatures on the optical properties of Ce doped ZnO nanorods was also studied. The as-grown samples exhibited very different ratios of ultraviolet to visible (defect) emission. The relative contributions of green and orange–red emissions in the emission spectra of annealed samples were also dependent on the precursor used, indicating that the types and concentrations of native defects were dependent on the precursor used. To explore the possibility of applications of these nanorods in ZnO-based devices, nanorods were also grown on p-GaN substrates. Two different Ce precursors in this case resulted in different current–voltage curves, as well as different electroluminescence and photoluminescence spectra of the devices. Obtained results are discussed. [Copyright &y& Elsevier]

Abstract: ZnO nanorods were prepared by electrodeposition, and the effect of different shells (MgO and TiO x ) on their optical properties has been studied. Shells have also been prepared using a simple solution based method. The two types of shells exhibited different effects on the optical properties of ZnO nanorods, mainly due to different annealing temperature required for synthesis process. The improvement in the emission intensity from the samples under optical excitation did not result in changes in the emission spectra or increase in emission intensity under electrical excitation for the same bias voltage. However, improved luminance for the same bias current was observed for most core-shell structures. [ABSTRACT FROM AUTHOR]

Abstract: ZnO nanomaterials exhibit prominent antibacterial activity even without UV illumination. Their antibacterial activity was attributed to different mechanisms, such as production of reactive oxygen species (ROS) and/or release of zinc ions in solution. Here we examined the relationship between the properties of eight different ZnO nanoparticles, their production of ROS, zinc ion release and antibacterial activity. We found that while the particles exhibited differences in antibacterial activity, there was no correlation with ROS production and zinc ion release. However, ROS production was inversely correlated with the concentration of nonradiative defects indicating that the recombination losses of photogenerated carriers can negatively affect ROS production. [Copyright &y& Elsevier]

Abstract: ZnO and TiO2 1D nanostructures (nanorods and nanotubes) were prepared by low-cost, low-temperature, solution-based methods and their properties and photocatalytic performance were studied. ZnO nanorod samples with titania and alumina shells were also prepared by solution-based methods, and their properties and photocatalytic performance were compared to that of bare ZnO nanorods. We found that ZnO and TiO2 exhibited comparable photocatalytic performance. Faster dye degradation under simulated solar illumination was observed for ZnO, while under UV illumination faster degradation was observed for TiO2. ZnO nanorods with titania shells exhibited inferior photocatalytic performance, while for alumina shells the performance was similar to bare ZnO. Reasons for observed differences are discussed, and the effect of the shell on photocatalytic activity is attributed to the changes in native defects at the ZnO surface/shell interface. [ABSTRACT FROM AUTHOR]