Growth Of One-dimensional ZnO Nanostructures Research Articles

Effect of zinc-hydroxo species on the growth of one-dimensional ZnO nanostructures

One-dimensional ZnO nanostructures were grown on ZnO seed layer by hydrothermal method using zinc nitrate (Zn(NO3)2) and sodium hydroxide (NaOH) as precursors. The concentrations of NaOH and Zn(NO3)2 were varied from 40 mM to 680 mM and kept constant, respectively. Effects of increasing the hydroxide ions on the concentration of zinc-hydroxo species in the solution were studied using thermodynamic simulation software. The simulated results showed that Zn(OH)2 and Zn(OH)3- concentrations tended to decrease but Zn(OH)42- was non-linearly increased when the concentration of NaOH at room temperature was increased. After the growth of ZnO, the samples were characterized by FESEM and UV-vis to investigate the morphology and transmittance spectra, respectively. The results showed that the rod density of ZnO nanostructures was decreased due to lower concentrations of Zn(OH)2 and Zn(OH)3- species affecting ZnO nucleation mode. On the other hand, Zn(OH)42- was competitively higher and involved in growing 1-D ZnO nanostructures on the nucleation layer resulting in larger diameter and longer length of nanostructures. For the UV-vis results, the % transmittance spectra in visible region of grown ZnO nanostructures with NaOH concentrations from 40 to 360 mM were more than 70% but too low transmittance for 520 mM.

Field-assisted growth of one-dimensional ZnO nanostructures with high defect density

One-dimensional ZnO nanostructures have shown great potential in electronics, optoelectronics and electromechanical devices owing to their unique physical and chemical properties. Most of these nanostructures were grown by equilibrium processes where the defects density is controlled by thermodynamic equilibrium. In this work, flash sintering, a non-equilibrium field-assisted processing method, has been used to synthesize ZnO nanostructures. By applying a high electric field and limiting a low current flow, ZnO nanorods grew uniformly by a vapor–liquid–solid mechanism due to the extreme temperatures achieved near the hot spot. High density basal stacking faults in the nanorods along with ultraviolet excitonic emission and a red emission under room temperature demonstrate the potential of defect engineering in nanostructures via the field-assisted growth method.

Facile solvothermal synthesis of abnormal growth of one-dimensional ZnO nanostructures by ring-opening reaction of polyvinylpyrrolidone

Abnormal growth of one-dimensional (1-D) ZnO nanostructures (NSs) have been accomplished with the assistance of polyvinylpyrrolidone (PVP) under a super high alkaline alcoholic solvothermal condition. The products were characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (1H NMR) spectroscopy. The effect of synthetic conditions, such as reaction temperature and the addition of PVP, on the morphologies of ZnO products were investigated. The results show that PVP molecules had the significant role in the transformation of morphologies of ZnO NSs ranging from nanorods, nanoparticles to pyramids, as well as flower-like assembly features. The possible growth mechanism of ZnO pyramids was proposed based on ring-opening reaction of PVP.

Catalyst-free growth of one-dimensional ZnO nanostructures on SiO2 substrate and in situ investigation of their H2 sensing properties

One-dimensional (1D) ZnO nanostructures were synthesized on SiO2 substrate by a catalyst-free thermal evaporation method using metallic Zn powders as a raw material. The crystal structure and morphology of the ZnO nanostructures were investigated by SEM, XRD and BET. The results showed that the 1D nanostructures obtained on the SiO2 substrate were hexagonal ZnO. Source temperature and Ar flow rate were an important parameter for the growth of the 1D nanostructures and particular type of ZnO nanostructures could be grown in a specific temperature and Ar flow rate. The H2 sensing properties of prepared 1D ZnO nanostructures were in situ investigated. The sensor exhibited high sensitivity and fast response to H2 gas. The highest sensitivity observed upon exposure to H2 at 1000ppm was 5.3 at 200°C, which demonstrates the potential application of the 1D ZnO nanostructures for fabricating gas sensors compatible with semiconductor technology.

Growth of vertically aligned one-dimensional ZnO nanowire arrays on sol–gel derived ZnO thin films

Vertically aligned one-dimensional ZnO nanowire arrays have been synthesized by a hydrothermal method on sol–gel derived ZnO films. Sol–gel derived ZnO films and corresponding ZnO nanowire arrays have been characterized by X-ray diffraction and field-emission scanning electron microscopy. The effect of sol–gel derived ZnO film surface on the morphology of ZnO nanowire arrays has been investigated. The authors suggest from our investigation that sol–gel derived ZnO films affect the growth of one-dimensional ZnO nanostructures. Not only crystalline ZnO films but also amorphous ones can act as a scaffold for ZnO nucleus. Tilted ZnO micro-rods are grown on ZnO gel films, whereas vertically aligned ZnO nanowire arrays are grown on nanometer-sized ZnO grains. The average diameter of ZnO nanowire arrays are correlated strongly with the grain size of sol–gel derived ZnO films.

Synthesis of One-Dimensional ZnO Nanostructures from Zn Powder/Granule

We report the growth of one-dimensional ZnO nanostructures with different morphologies such as nanoneedles, nanorods, nanobelts from Zn powder/granule. The growth process is different from the conventional vapor-solid mechanism. The advantage of this method is that neither a catalyst nor any gas flow is required for the synthesis of nanostructures. Depending upon the Zn powder or Zn granules as the starting material different nanostructures have been synthesized which demonstrates the versatility of the technique.

Direct and Large-Area Growth of One-Dimensional ZnO Nanostructures from and on a Brass Substrate

A convenient method for the direct and large-area growth of one-dimensional (1-D) ZnO nanostructures on a conductive brass substrate has been developed, consisting of thermal oxidation of a Cu0.66Zn0.34 alloy foil in the presence of oxygen. Various 1-D nanostructures such as nanowires, nanobelts, nanocombs, and nanosheets have been in situ grown on the brass substrate under different reaction temperatures and characterized by means of X-ray diffraction, electron microscopy, and X-ray photoelectron spectroscopy. In this preparation, the Cu0.66Zn0.34 alloy foil functions as both Zn source and substrate for the growth of 1-D ZnO nanostructures; thus, the synthesis and assembly of ZnO nanostructures on a metallic substrate is accomplished in one step, and the naturally good adhesion or electrical connection between the ZnO nanostructures and the conductive substrate has been realized. This approach could prepare ZnO nanostructures on a brass substrate without size limitations. Such a configuration of product ...