As-synthesized ZnO Nanorods Research Articles

Highly Oriented 1-D ZnO Nanorod Arrays on Zinc Foil: Direct Growth from Substrate, Optical Properties and Photocatalytic Activities

Highly oriented and large-scale ZnO nanorod arrays have been successfully synthesized on zinc foil by a simple, low-temperature, solution-phase approach. In this approach, zinc foil was used not only as a substrate but also as a zinc-ion source for the direct growth of ZnO nanorod arrays. X-ray diffraction (XRD) analysis, high-resolution TEM (HRTEM) images, and selected-area electron diffraction (SAED) patterns indicated that the structure of the ZnO nanorod arrays on the zinc foil substrate was single-crystalline and grown in the [0001] direction with a wurtzite structure. The optical properties of the ZnO nanorod arrays were characterized by UV−vis diffuse reflectance, Raman, and photoluminescence spectroscopies. The photocatalytic activity of the ZnO nanorod arrays was tested by degradation of 4-chlorophenol (4-CP) under UV light irradiation compared to that of a ZnO nanorod film grown on a Ti substrate, indicating that the as-synthesized ZnO nanorod arrays exhibit excellent photocatalytic activity.

Synthesis and field emission of novel ZnO nanorod chains

Abstract A new aqueous chemical growth method for generation of ZnO nanorod chains, transformed from ZnO micro dumbbell, has been developed. The novel structure and morphology of the as-synthesized ZnO micro dumbbell and ZnO nanorod chains are characterized using X-ray diffraction and scanning electron microscopies. Field emission characterization shows that the turn-on fields for the ZnO nanorod chains and micro dumbbell are 2.7 and 5.0 V/μm, respectively. The field enhancement factor β was estimated to be about 2194 for ZnO nanorod chains. The findings imply that ZnO nanorod chains may be suitable for cold-cathode electron source applications.

Controllable Synthesis and Photoluminescence Properties of ZnO Nanorod and Nanopin Arrays

Well-aligned ZnO nanorods and nanopins are synthesized on a silicon substrate using a one-step simple thermal evaporation of a mixture of zinc and zinc acetate powder under controlled conditions. A self-assembled ZnO buffer layer was first obtained on the Si substrate. The structure and morphology of the as-synthesized ZnO nanorod and nanopin arrays are characterized using X-ray diffraction, and scanning and transmission electron microscopies, energy-dispersive X-ray spectroscopy, and photoluminescence spectroscopy. The influence of the background atmosphere on the two ZnO nanostructures has been studied. Two different growth mechanisms are mentioned to interpret the formation of ZnO nanorod and nanopin arrays in our work. The room-temperature PL features the ZnO nanorods exhibit only sharp and strong ultraviolet (UV) emission emissions, which confirms the better crystalline and optical quality than the ZnO nanopins.

Controllable Synthesis and Photoluminescence Properties of ZnO Nanorod and Nanopin Arrays

Well-aligned ZnO nanorods and nanopins are synthesized on a silicon substrate using a one-step simple thermal evaporation of a mixture of zinc and zinc acetate powder under controlled conditions. A self-assembled ZnO buffer layer was first obtained on the Si substrate. The structure and morphology of the as-synthesized ZnO nanorod and nanopin arrays are characterized using X-ray diffraction, and scanning and transmission electron microscopies, energy-dispersive X-ray spectroscopy, and photoluminescence spectroscopy. The influence of the background atmosphere on the two ZnO nanostructures has been studied. Two different growth mechanisms are mentioned to interpret the formation of ZnO nanorod and nanopin arrays in our work. The room-temperature PL features the ZnO nanorods exhibit only sharp and strong ultraviolet (UV) emission emissions, which confirms the better crystalline and optical quality than the ZnO nanopins.

Synthesis and field emission of patterned ZnO nanorods

Abstract A simple and self-catalytic method has been developed for synthesizing finely patterned ZnO nanorods on ITO-glass substrates under a low temperature of 500 °C. The patterned ZnO nanorod arrays, a unit area is of ∼400 × 100 μm 2 , are synthesized via vapor phase transport method. The surface morphology and composition of the as-synthesized ZnO nanorods are characterized by means of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The mechanism of formation of ZnO nanorods is also discussed. The measurement of field emission (FE) reveals that the as-synthesized ZnO nanorods arrays have a turn-on field of 3.3 V/μm at the current density of 0.1 μA/cm 2 and a low threshold field of 6.2 V/μm at the current density of 1 mA/cm 2 . So this approach must have a potential application of fabricating micropatterned oxide thin films used in FE-based flat panel displays.

Structural Properties of ZnO Grown on GaN∕Sapphire Templates

ZnO nanorods were synthesized on GaN/sapphire substrates using a modified thermal-evaporation process. The as-synthesized ZnO nanorods and thin films were characterized using scanning electron microscopy, micro-Raman, and X-ray diffraction techniques. The morphology of the ZnO changes from nanorods to continuous thin films when the growth temperature increases to 800°C. Further increase in the growth temperature leads to a lower growth rate of ZnO along the (0001) direction. Micro-photoluminescence measurements show ultraviolet band-edge emission peaks around 378 nm from both nanorods and thin films. Realization of such ZnO structures may be useful for the fabrication of hybrid ZnO/GaN optoelectronic devices.

Conversion of ZnO Nanorod Arrays into ZnO/ZnS Nanocable and ZnS Nanotube Arrays via an in Situ Chemistry Strategy

Vertically aligned ZnO nanorods with uniform diameter and length have been synthesized on a zinc foil substrate with ammonium persulfate as oxidant via a facile, larger scale production and inexpensively synthesized method without any templates or additives. SEM and XRD studies indicate that ZnO nanorods are well-oriented along the c-axis. The PL spectrum indicates that our as-synthesized ZnO nanorods with a stronger and wider green emission are promising candidates as electron nanoconductors in nano-optoelectronic devices. Furthermore, by an effective thioglycolic acid-assisted solution route, well-aligned ZnO/ZnS nanocable and ZnS nanotube arrays have been successfully synthesized. ZnS nanotubes show a perfect hexagonal and obvious tubular shape. Our present strategy shows mild growth conditions and good reproducibility.

Synthesis and optical characteristic of ZnO nanorod

ZnO is a wide band gap semiconductor with an energy gap of 3.37 eV at room temperature. It is a versatile material and has been used considerably for its catalytic, electrical, optoelectronic and photochemical properties [1, 2]. ZnO has large exciton binding energy (60 meV) which allows UV lasing action to occur even at room temperature and ZnO with oxygen vacancies (ZnO:Zn) exhibits an efficient green emission. ZnO semiconductor used as photocatalytic degradation materials of environmental pollutants has been extensively studied because of its advantage in non-toxic nature, low cost and high reactivity. However, such photocatalytic degradation only proceeds under UV irradiation because of its wide band-gap and can only absorb UV light. Therefore, ZnO-based materials capable of visiblelight photocatalysis are required [3]. To change the optical absorption properties and improve the visiblelight photocatalysis, several approaches based on TiO2 photocatalysts have been applied such as implanting transition metal ions into a TiO2 powder or film to produce a red shift of the absorption spectra, treating TiO2 photocatalysts by applying hydrogen plasma technology to create a new absorption band in the visible-light region through the formation of oxygen vacancies, surface sensitization of a semiconductor TiO2 photocatalyst to extend the spectral response into the visible region and so on. Among the above approaches, some are effective to produce visible absorption with special facility; and some are not effective. Recently, one-dimensional ZnO nanomaterials such as nanorods and nanowires have been intensively investigated for its remarkable properties. Among them, most of the literature reported the photoluminescence properties with UV emission and little are dedicated to fabricate nanorods with visible absorption. In literature study, many methods have been used to fabricate 1D ZnO nanorods. In the solution hydrothermal method, always alkali solution of Zn(OH)4 or Zn(NH3)4 2– was used as precursors [4]. In this paper, precipitate of ZnCl2 and ammonia solution was used as precursors to hydrothermally synthesize ZnO nanorod and CTAB was used as surfactant and modifying agent. The absorption spectra of the as-synthesized ZnO nanorod showed red shift comparing with bulk ZnO powders. The reason for visible-light absorption was discussed. An aqueous solution of 0.5 M ZnCl2 was mixed with diluted ammonia solution slowly under stirring until pH = 6.7. After the reaction completed, the precipitate was washed and dried at 60 C to obtain precursor. Appropriate amount of the precursor powder (0.98 g) was dispersed in 20 mL distilled water. Then 20 mL CTAB (0.1 M) was added and the pH value is adjusted by diluted ammonia or NaOH solution. The mixture was transferred into a Teflon-lined autoclave of 60 mL and pretreated by ultrasonic water bath for 30 min. After that, the autoclave was sealed and hydrothermally heated at 180 C for 12–24 h. The obtained product was washed with distilled water and ethanol and dried. Powder X-ray diffraction (XRD) was performed on a Bruker D8-advance X-ray diffractometer with Cu Ka (k = 1.54178 A) radiation. The size and morphology of L. Wu Y. Wu (&) College of Materials Science and Engineering, Shandong University, Jinan, Shandong 250061, China e-mail: wllzjb@eyou.com J Mater Sci (2007) 42:406–408 DOI 10.1007/s10853-006-0727-y

Synthesis of ZnO nanorods from aqueous solution

In the present work, crystalline one-dimensional ZnO nanorods were synthesized by a PVP (polyvinylpyrrolidone)-assisted hydrothermal process with zinc acetate as the precursor. The major advantage of this technique is the use of water as the solvent: cheaper and more environmentally friendly than alcohol. The as-synthesized ZnO nanorods have diameters of 50–200 nm and lengths up to 5 μm. X-ray powder diffractometry (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED), Fourier transmission infrared spectroscopy (FTIR) were used to characterize the structural and the chemical features of the ZnO nanorods.

Solvothermal synthesis of hexagonal ZnO nanorods and their photoluminescence properties

Pure hexagonal ZnO nanorods were synthesized by low-temperature (90 °C) solvothermal treatment of zinc acetate in 40–80 wt.% hydrazine hydrate aqueous solutions. The products were characterized by means of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electronic microscopy (TEM), selected area electron diffraction (SAED), and room temperature photoluminescence (RTPL) spectra. They show a strong UV emission at around 380 nm upon excitation at 360 nm using a Xe lamp at room temperature. The influence on the quality of the nanorods was investigated while the content of the solvent changed. The as-synthesized ZnO nanorods are promising materials for nanoscale optoelectronic devices due to their excellent UV emission properties.

Direct synthesis of well dispersed ZnO nanorods without using additional surfactant

Without using additional surfactant as structure-directing agent, well dispersed ZnO nanorods were directly synthesized in the dimethyl sulfoxide (DMSO) and alcohol mixture solution by a one-step wet chemical method. The experiment results demonstrated that alcohol molecular with longer chain is helpful for the growth of ZnO nanorods. The absorption and emission spectra of as-synthesized ZnO nanorods were also presented in this paper.

Fabrication of Optically Enhanced ZnO Nanorods and Microrods Using Novel Biocatalysts

We developed a straightforward method to produce hexagonal ZnO nanorods and microrods using a novel biocatalyst, Magnetospirillum magnetotacticum. ZnO nanorods were synthesized homogeneously on growth substrates when the bacterial catalysts were deposited uniformly on substrates whereas ZnO microrods were formed when the catalysts were introduced to selective areas of growth substrates using microcontact printing. X-ray diffraction measurements reveal that these ZnO structures exhibit Wurtzite structures with preferential growth along [0001] direction. Room-temperature photoluminescence spectra of the as-synthesized ZnO nanorods and microrods show extremely strong and sharp UV emission at 390 nm and negligible green emission at 510 nm. Our results demonstrate that Magnetospirillum magnetotacticum is an effective catalyst for the growth of nanometer- and micrometer-sized ZnO structures with exceptionally high-quality optical properties. These defect-free ZnO nano-and micro-materials, when combined with microcontact printing techniques to achieve patterned growth over large areas of substrates, can facilitate their photonic-based applications as optoelectronic devices and chemical/biological sensors.