Extended and oriented nanostructures are desirable for many applications, but direct fabrication of complex nanostructures with controlled crystalline morphology, orientation and surface architectures remains a significant challenge. Here we report a low-temperature, environmentally benign, solution-based approach for the preparation of complex and oriented ZnO nanostructures, and the systematic modification of their crystal morphology. Using controlled seeded growth and citrate anions that selectively adsorb on ZnO basal planes as the structure-directing agent, we prepared large arrays of oriented ZnO nanorods with controlled aspect ratios, complex film morphologies made of oriented nanocolumns and nanoplates (remarkably similar to biomineral structures in red abalone shells) and complex bilayers showing in situ column-to-rod morphological transitions. The advantages of some of these ZnO structures for photocatalytic decompositions of volatile organic compounds were demonstrated. The novel ZnO nanostructures are expected to have great potential for sensing, catalysis, optical emission, piezoelectric transduction, and actuations.

Complex and oriented ZnO nanostructures

One-dimensional (1D) ZnO nanostructures have been studied intensively and extensively over the last decade not only for their remarkable chemical and physical properties, but also for their current and future diverse technological applications. This article gives a comprehensive overview of the progress that has been made within the context of 1D ZnO nanostructures synthesized via wet chemical methods. We will cover the synthetic methodologies and corresponding growth mechanisms, different structures, doping and alloying, position-controlled growth on substrates, and finally, their functional properties as catalysts, hydrophobic surfaces, sensors, and in nanoelectronic, optical, optoelectronic, and energy harvesting devices.

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One-dimensional ZnO nanostructures: Solution growth and functional properties

Metal oxides are the key ingredients for the development of many advanced functional materials and smart devices. Nanostructuring has emerged as one of the best tools to unlock their full potential. Tungsten oxides (WOx) are unique materials that have been rigorously studied for their chromism, photocatalysis, and sensing capabilities. However, they exhibit further important properties and functionalities that have received relatively little attention in the past. This Feature Article presents a general review of nanostructured WOx, their properties, methods of synthesis, and a description of how they can be used in unique ways for different applications. Tungsten oxides (WOx) are unique functional materials that can be obtained in a vast variety of nanostructured forms. This Feature Article presents a comprehensive review on the properties of WOx that goes beyond chromism and photocatalysis, for which they are usually investigated for. This is followed by a survey of their synthesis methods and implementations for different applications.

Nanostructured Tungsten Oxide – Properties, Synthesis, and Applications

ZnS nanostructures: From synthesis to applications

many existing energy-harvesting and storage devices are stilltoo bulky and heavy for intended applications. For example,high-efficiency dye-sensitized solar cells (DSSCs) employfluorine-doped tin oxide (FTO) glass as the substrate ofworking electrode. However, the use of rigid FTO glass hasrestricted adaptability of DSSCs during transportation,installation, and application,

/pdf/fiber-supercapacitors-made-of-nanowire-fiber-hybrid-2hybsvhq02.pdf

Fiber Supercapacitors Made of Nanowire‐Fiber Hybrid Structures for Wearable/Flexible Energy Storage

Field electron emission from vertically well-aligned zinc oxide (ZnO) nanowires, which were grown by the vapor deposition method at a low temperature of 550 °C, was investigated. The high-purity ZnO nanowires showed a single crystalline wurtzite structure. The turn-on voltage for the ZnO nanowires was found to be about 6.0 V/μm at current density of 0.1 μA/cm2. The emission current density from the ZnO nanowires reached 1 mA/cm2 at a bias field of 11.0 V/μm, which could give sufficient brightness as a field emitter in a flat panel display. Therefore, the well-aligned ZnO nanowires grown at such low temperature can promise the application of a glass-sealed flat panel display in a near future.

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Field emission from well-aligned zinc oxide nanowires grown at low temperature

http://nanotube.korea.ac.kr/wp-content/papers/2002/CPL363(2002)134.pdf

Low temperature growth and photoluminescence of well-aligned zinc oxide nanowires

Well-aligned single-crystalline wurzite zinc oxide (ZnO) nanowire array was successfully fabricated on an Al2O3 substrate by a simple physical vapor-deposition method at a low temperature of 450 °C...

Low-temperature growth of ZnO nanowire array by a simple physical vapor-deposition method

High-density ZnO nanowires (ZnONWs) were aligned onto Au-catalyzed Si substrate through a simple low-temperature physical vapor deposition method. Scanning electron microscope (SEM) observations, x-ray diffraction (XRD) analysis, and photoluminescence spectra showed that the ZnONWs were single-crystalline, with a hexagonal wurzite structure. All of the results inferred from the SEM observations, the XRD rocking curves, and the Raman spectra for the investigated samples confirm that the ZnONWs are well aligned and c-axis oriented. The Raman spectra also indicated that the ZnONWs on Si substrates are under the biaxial compressive stress. Since it takes the advantage of low-cost, easily controlled deposition spot (due to the selective deposition trait of the Au layer), potential for scale-up production, and ability to integrate with Si substrate, this technique has a potential in future for fabricating the ZnONW array-based optoelectronic devices.

http://nanotube.korea.ac.kr/wp-content/papers/2003/APL83(2003)4631.pdf

Low-temperature growth and Raman scattering study of vertically aligned ZnO nanowires on Si substrate

Well-aligned indium oxide pyramids were synthesized on a Ni-coated silicon (100) substrate by a chemical vapor deposition. Scanning electron microscopy and x-ray diffraction investigations show that these pyramids present a tetragonal morphology and single-crystalline cubic bixbyite structure. The size control of the pyramids was achieved by varying the growth temperature. Field-emission characteristics of the as-grown indium oxide pyramids were measured. The field-emission current density of the nanopyramids (average size: ∼180 nm) reached about 1 mA/cm2 at a threshold field of about 6.0 V/μm, which is comparable to that of carbon nanotubes, and can guarantee sufficient luminescence brightness in a flat panel display.

Ye Zhang

Papers

Field emission from well-aligned zinc oxide nanowires grown at low temperature

Low temperature growth and photoluminescence of well-aligned zinc oxide nanowires

Low-temperature growth of ZnO nanowire array by a simple physical vapor-deposition method

Low-temperature growth and Raman scattering study of vertically aligned ZnO nanowires on Si substrate

Efficient field emission from single crystalline indium oxide pyramids