11 research outputs found

    Dual-mode mechanical resonance of individual ZnO nanobelts

    Get PDF
    ©2003 American Institute of Physics. The electronic version of this article is the complete one and can be found online at: http://link.aip.org/link/?APPLAB/82/4806/1DOI:10.1063/1.1587878The mechanical resonance of a single ZnO nanobelt, induced by an alternative electric field, was studied by in situ transmission electron microscopy. Due to the rectangular cross section of the nanobelt, two fundamental resonance modes have been observed corresponding to two orthogonal transverse vibration directions, showing the versatile applications of nanobelts as nanocantilevers and nanoresonators. The bending modulus of the ZnO nanobelts was measured to be ~52 GPa and the damping time constant of the resonance in a vacuum of 5×10–8 Torr was ~1.2 ms and quality factor Q = 500

    Nanopropeller arrays of zinc oxide

    Get PDF
    ©2004 American Institute of Physics. The electronic version of this article is the complete one and can be found online at: http://link.aip.org/link/?APPLAB/84/2883/1DOI:10.1063/1.1702137Polar surface dominated ZnO nanopropeller arrays were synthesized by a two-step high temperature solid-vapor deposition process. The axis of the nanopropellers is a straight nanowire along the c axis and enclosed by {20} surfaces, which grew first; the sixfold symmetric nanoblades are later formed along the crystallographic equivalent a axes (20) perpendicular to the nanowire; and the array is formed by epitaxial growth of nanoblades on the nanowire. The top surface of the nanoblade is the Zn terminated +c plane, showing surface steps and possible secondary growth of nanowires due to higher self-catalytic activity, while the back surface is the oxygen-terminated –c plane, which is smooth and inert

    Nanoarchitectures of semiconducting and piezoelectric zinc oxide

    Get PDF
    ©2005 American Institute of Physics. The electronic version of this article is the complete one and can be found online at: http://link.aip.org/link/?JAPIAU/97/044304/1DOI:10.1063/1.1847701Semiconducting and piezoelectric zinc oxide has two important structure characteristics: the multiple and switchable growth directions: 010, 20, and 0001; and the {0001} polar surfaces. The fast growth directions create nanobelts of different crystallographic facets, and the polar surfaces result in bending of the nanobelt for minimizing the spontaneous polarization energy. A combination of these distinct growth characteristics results in a group of unique nanostructures, including several types of nanorings, nanobows, platelet circular structures, Y-shape split ribbons, and crossed ribbons. We present here the as-grown nanoarchitectures naturally created by combining some of the fundamental structure configurations of ZnO, which could be unique for many applications in nanotechnology

    Piezoelectric Nanostructures of Zinc Oxide: Synthesis, Characterization and Devices

    Get PDF
    In this thesis, a systematic study has been carried out on the synthesis, characterization and device fabrication of piezoelectric ZnO nanstructures. The achieved results are composed of the following four parts. Firstly, through a systematic investigation on the Sn-catalyzed ZnO nanostructure, an improved understanding of the chemical and physical process occurring during the growth of hierarchical nanostructures has been achieved. Decomposed Sn from SnO2 has been successfully demonstrated and proved to be an effective catalyst guiding the growth of not only aligned ZnO nanowires, but also the hierarchical nanowire-nanoribbon junction arrays and nanopropeller arrays. During the vapor-liquid-solid (VLS) catalyzing growth process at high temperature, Sn in the liquid state has been proved to be able to guide the growth of nanowires and nanoribbons in terms of growth directions, side facets, and crystallographic interfaces between Sn and ZnO nanostructures. Secondly, using pure ZnO as the only source material, by precisely tuning and controlling the growth kinetics, a variety of hierarchical polar surface dominated nanostructures have been achieved, such as single crystal nanorings, nanobows, nanosprings and superlattice nanohelices. High yield synthesis of ZnO nanosprings over 50% has been successfully obtained by mainly controlling the pre-pumping level associated with the partial pressure of residual oxygen during the vapor-solid growth process. The rigid superlattice nanohelices of ZnO have been discovered, which is a result of minimization of the electrostatic energy induced by polar surfaces. The formation process of the nanohelix has been systematically characterized. Thirdly, two new strategies have been successfully developed for fabricating ZnO quantum dots and synthesis of ZnO nanodiskettes and nanotubes. The formation process is based on a common concept of self-assembly. Finally, a series of devices and applications studies based on several piezoelectric ZnO nanostructures, such as nanobelts, nanopropellers and nanohelices, have been carried out utilizing the electro-mechanical resonance, bio-surface functionalization, devices fabrication and electrical characterization. Individual nanobelt and nanohelix based nanodevices have been successfully fabricated for applications in chemical and biological sensing. The study opens a few new areas in oxide nanostructures and applications.Ph.D.Committee Chair: Zhong L. Wang; Committee Member: C.J. Summers; Committee Member: C.P. Wong; Committee Member: David N. Ku; Committee Member: W.Jack Lacke

    Manganese-doped ZnO nanobelts for spintronics

    Get PDF
    ©2004 American Institute of Physics. The electronic version of this article is the complete one and can be found online at: http://link.aip.org/link/?APPLAB/84/783/1DOI:10.1063/1.1645319Zinc oxide (ZnO) nanobelts synthesized by thermal evaporation have been ion implanted with 30 keV Mn+ ions. Both transmission electron microscopy and photoluminescence investigations show highly defective material directly after the implantation process. Upon annealing to 800 °C, the implanted Mn remains in the ZnO nanobelts and the matrix recovers both in structure and luminescence. The produced high-quality ZnO:Mn nanobelts are potentially useful for spintronics

    Semiconducting Nanobelts of ZnO and ZnS

    No full text

    Single-Atom Cobalt Catalysts Coupled with Peroxidase Biocatalysis for C–H Bond Oxidation

    No full text
    This paper reports a robust strategy to catalyze in situ C–H oxidation by combining cobalt (Co) single-atom catalysts (SACs) and horseradish peroxidase (HRP). Co SACs were synthesized using the complex of Co phthalocyanine with 3-propanol pyridine at the two axial positions as the Co source to tune the coordination environment of Co by the stepwise removal of axial pyridine moieties under thermal annealing. These structural features of Co sites, as confirmed by infrared and X-ray absorption spectroscopy, were strongly correlated to their reactivity. All Co catalysts synthesized below 300 °C were inactive due to the full coordination of Co sites in octahedral geometry. Increasing the calcination temperature led to an improvement in catalytic activity for reducing O2, although molecular Co species with square planar coordination obtained below 600 °C were less selective to reduce O2 to H2O2 through the two-electron pathway. Co SACs obtained at 800 °C showed superior activity in producing H2O2 with a selectivity of 82–85% in a broad potential range. In situ production of H2O2 was further coupled with HRP to drive the selective C–H bond oxidation in 2-naphthol. Our strategy provides new insights into the design of highly effective, stable SACs for selective C–H bond activation when coupled with natural enzymes
    corecore