Integrated nanophotonic hubs based on ZnO-Tb(OH)3/SiO2 nanocomposites.

Optical integration is essential for practical application, but it remains unexplored for nanoscale devices. A newly designed nanocomposite based on ZnO semiconductor nanowires and Tb(OH)3/SiO2 core/shell nanospheres has been synthesized and studied. The unique sea urchin-type morphology, bright and sharply visible emission bands of lanthanide, and large aspect ratio of ZnO crystalline nanotips make this novel composite an excellent signal receiver, waveguide, and emitter. The multifunctional composite of ZnO nanotips and Tb(OH)3/SiO2 nanoparticles therefore can serve as an integrated nanophotonics hub. Moreover, the composite of ZnO nanotips deposited on a Tb(OH)3/SiO2 photonic crystal can act as a directional light fountain, in which the confined radiation from Tb ions inside the photonic crystal can be well guided and escape through the ZnO nanotips. Therefore, the output emission arising from Tb ions is truly directional, and its intensity can be greatly enhanced. With highly enhanced lasing emissions in ZnO-Tb(OH)3/SiO2 as well as SnO2-Tb(OH)3/SiO2 nanocomposites, we demonstrate that our approach is extremely beneficial for the creation of low threshold and high-power nanolaser.

Selectively enhanced band gap emission in ZnO/Ag2O nanocomposites.

A new composite consisting of ZnO nanorods decorated with Ag(2)O nanoparticles has been synthesized and characterized. It is found that the band gap emission of ZnO nanorods can be greatly enhanced by about 10 times, while the defect emission can be suppressed to the detection limit, simultaneously. The ratio between the band gap and defect emission reaches to an enhanced factor of about 600 times. The underlying mechanism is attributed to the combined effects of surface modification, band alignment, as well as charge transfer. Our approach provided here can be extended to many other semiconductors for creating nanocomposites with novel optical properties.

Enhancement of band-edge emission induced by defect transition in the composite of ZnO nanorods and CdSe/ZnS quantum dots.

A new and general approach to enhance band-edge emission at the expense of defect emission in a semiconductor nanocomposite is proposed. The underlying mechanism is based on the resonance effect between defect transition and band-to-band excitation and transfer of excited electrons between conduction band edges. With our approach, it is possible to convert defect loss into bandgap emission. As an example, we demonstrate that the bandgap emission of ZnO nanorods can be enhanced by as much as 30 times when they are compounded with CdSe/ZnS nanoparticles.

Patterned growth of ZnO nanostructures based on the templation of plant cell walls.

A new and general approach based on vapor-phase transport technique using Au-coated plant cell walls has been developed to synthesize patterned ZnO nanostructures. Nanowires, nanodendrites and nanotowers were fabricated by adsorption of different metallic ions on plant cell walls. It is shown that plant cell wall can serve as a well-defined template to grow patterned nanostructures. Using transmission electron microscope and Raman spectroscopy, the structural characteristic of the nanostructures were investigated, exhibiting good crystallinity and hexagonal symmetry of the nanomaterials. Quite interestingly, the shape of the nanostructures can be controlled by the metallic ions adsorbed on plant cell walls. Without metallic ions, a homogeneous distribution of nanowires was obtained. On the other hand, with Ni+2 or Fe+3 ions, nanodendrites and nanotowers were observed, respectively. Our approach provides a low cost method that opens up new possibilities for the growth of patterned nanomaterials with desired shapes.

Giant white and blue light emission from Al(2)O(3) and ZnO nanocomposites.

A new and general approach enabling us to amplify not only the bandgap emission of ZnO nanorods but also the defect emission of Al(2)O(3) is proposed. The light intensity of the band edge emission of ZnO nanorods can be improved by as much as 19 times after the decoration of Al(2)O(3) layers. Moreover, white light emission arising from Al(2)O(3) defects in ZnO/Al(2)O(3) nanostructures also shows a large enhancement factor of 12 times. Our new strategy offers an alternative possibility to create strong white and blue light-emitting devices.

Giant enhancement of band edge emission in ZnO and SnO nanocomposites.

ZnO/SnO nanocomposites have been designed to enhance the band edge emission and suppress the defect emission of ZnO nanorods simultaneously. It is found that the intensity ratio between the band edge and defect emission can be improved by up to 4 orders of magnitude. The underlying mechanism is interpreted in terms of surface modification as well as carrier transfer from SnO nanoparticles to ZnO nanorods. Our approach is very useful for creating highly efficient optoelectronic devices.