Preparation and characterization of short length ZnO nanorods and ZnO@ZnS core–shell nanostructures (original) (raw)
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Effect of zinc oxide concentration on the core–shell ZnS/ZnO nanocomposites
Journal of Materials Science: Materials in Electronics, 2013
In this work, synthesis and characterization of core-shell zinc sulphide (ZnS)/zinc oxide (ZnO) nanocomposites has been reported to see the effect of ZnO concentration in core-shell combination. The nascent as well as core-shell nanostructures were prepared by a chemical precipitation method starting with the synthesis of nascent ZnS nanoparticles. The change in morphological and optical properties of core-shell nanoparticles was studied by changing the concentration of ZnO for a fixed amount of ZnS. The nascent ZnS nanoparticles were of 4-6 nm in diameter as seen from TEM, each containing primary crystallites of size 1.8 nm which was estimated from the X-ray diffraction patterns. However, the particle size increases appreciably with the increase in ZnO concentration leading to the well known ZnO wurtzite phase coated with FCC phase of ZnS. Band gap studies were done by UV-visible spectroscopy and it shows that band gap tunability can be achieved appreciably in case of ZnS/ ZnO core-shell nanostructures by varying the concentration of ZnO. Fourier transform infrared analysis also proves the formation of core-shell nanostructures. Photoluminescence studies show that emission wavelength blue shifts with the increase in ZnO concentration. These coreshell ZnS/ZnO nanocomposites will be a very suitable material for any type of optoelectronic application as we can control various parameters in this case in comparison to the nascent nanostructures.
Synthesis, structural, and optical properties of type-II ZnO–ZnS core–shell nanostructure
Journal of Luminescence, 2014
We demonstrate a facile one-step method for the preparation of ZnO-ZnS core-shell type-II nanostructures, pure ZnS quantum dots and pure ZnO nanoparticles with different experimental conditions. Treatment with sodium hydroxide as a capping agent is investigated systematically during the synthesis of ZnS quantum dots (QDs). The thickness of the ZnS shell is controlled by the concentration of the sodium sulphide during the synthesis of ZnO-ZnS core-shell nanostructures. The morphology and structure of samples are verified by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray analysis (EDX). The UV-vis absorption spectra of the pure ZnS QDs exhibit a blue shift in the absorption edge due to the quantum confinement effect. The PL emission spectra of the ZnO-ZnS core-shell nanostructure are compared with the ZnO nanoparticles. The ZnO-ZnS core-shell nanostructures show decrease in the UV and green emissions with the appearance of a blue emission, which are not found in the ZnO nanoparticles.
Optical and structural investigation of ZnO@ZnS core–shell nanostructures
Materials Chemistry and Physics, 2016
h i g h l i g h t s g r a p h i c a l a b s t r a c t Obtation of ZnO@ZnS decorated systens using different solvents by MAS methodology. Growth solvent dependence of hexagonal and cubic phases for ZnS. Potential application of ZnO@ZnS decorated nanostructures as replacement material for solar cells. Control over band alignment between ZnO and ZnS.
Japanese Journal of Applied Physics, 2012
ZnO nanoparticles were synthesized using sol-gel method. The structural and optical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM), Raman spectroscopy, and photoluminescence (PL). XRD analysis demonstrates that the nanoparticles have the hexagonal wurtzite structure and the particle size is increased with annealing temperature. The average size of the nanoparticles was determined by SEM as well as XRD data and found to be 50 nm after annealing at 800 C. A sharp, strong and dominant UV emission with a suppressed green emission has been observed at 300 and 10 K, indicating the good optical properties of ZnO nanoparticles. The 10 K UV band is dominated by a neutral-donor bound exciton, and the surface-related SX emission at 3.31 eV is evidenced. #
2014
Uniformly distributed ZnO nanorods with several micrometers long have been successfully grown at low temperature by using two steps chemical bath deposition (CBD) method. In this mechanism of the ZnO nanorod films growth, the effects of Zn 2+ concentration on samples were prepared with different molarities of zinc acetate dihydrate in the solution. Structural, diameter in size and morphology of ZnO nanorod films were investigated in detail by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The optical properties of ZnO nanorod films were also studied by UV-Vis spectroscopy. From the results, it was observed that Zn 2+
Materials Science-Poland, 2015
In this work, zinc oxide (ZnO) nanorods were obtained by a simple chemical precipitation method in the presence of capping agent: polyvinyl pyrrolidone (PVP) at room temperature. X-ray diffraction (XRD) result indicates that the synthesized undoped ZnO nanorods have hexagonal wurtzite structure without any impurities. It has been observed that the growth direction of the prepared ZnO nanorods is [1 0 1]. XRD analysis revealed that the nanorods have the crystallite size of 49 nm. Crystallite size is calculated by Debye-Scherrer formula and lattice strain is calculated by Williomson-Hall equation. Cell volume, Lorentz factor, Lorentz polarization factor, bond length, texture coefficient, lattice constants and dislocation density have also been studied. We also compared the interplanar spacings and relative peak intensities with their standard values at different angles. The scanning electron microscope (SEM) images confirmed the size and shape of these nanorods. It has been found that...
The Journal of Physical Chemistry C, 2015
We have used pulsed-laser deposition, following a specific sequence of heating and cooling phases, to grow ZnO nanorods on ZnO buffer/Si(100) substrates, in a 600 mT oxygen ambient, without catalyst. In these conditions, the nanorods preferentially self-organize in the form of vertically aligned, core/shell structures. X-ray diffraction analyses, obtained from 2θ−ω and pole figure scans, shows a crystalline (wurtzite) ZnO deposit with uniform c-axis orientation normal to the substrate. Field emission scanning electron microscopy, transmission electron microscopy (TEM), high resolution TEM, and selected area electron diffraction studies revealed that the nanorods have a crystalline core and an amorphous shell. The low-temperature (13 K) photoluminescence featured a strong I 6 (3.36 eV) line emission, structured green band emission, and a hitherto unreported broad emission at 3.331 eV. Further studies on the 3.331 eV band showed the involvement of deeply bound excitonic constituents in a single electron−hole recombination. The body of structural data suggests that the 3.331 eV emission can be linked to the range of defects associated with the unique crystalline ZnO/amorphous ZnO core/shell structure of the nanorods. The relevance of the work is discussed in the context of the current production methods of core/shell nanorods and their domains of application. Figure 3. (a, b, d) Field emission SEM and (c) SEM images of ZnO/ZnO core/shell nanorods grown by PLD at (a) 0°tilt (plane view), (b) 20°tilt, (c) 30°tilt, and (d) 85°tilt angles.
Effect of zinc oxide concentration in fluorescent ZnS:Mn/ZnO core–shell nanostructures
Journal of Materials Science: Materials in Electronics, 2014
In the present work, we have prepared zinc sulphide (ZnS:Mn)/zinc oxide (ZnO) core-shell nanostructures by a chemical precipitation method and observed the effect of ZnO concentration on the fluorescent nanoparticles. Change in the morphological and optical properties of core-shell nanoparticles have been observed by changing the concentration of ZnO in a core-shell combination with optimum value of Mn to be 1 % in ZnS. The morphological studies have been carried out using X-ray diffraction (XRD) and transmission electron microscopy. It was found that diameter of ZnS:Mn nanoparticles was around 4-7 nm, each containing primary crystallites of size 2.4 nm which was estimated from the XRD patterns. The particle size increases with the increase in ZnO concentration leading to the well-known ZnO wurtzite phase which was coated on the FCC phase of ZnS:Mn. Band gap studies were performed by UV-visible spectroscopy and a red shift in absorption spectra have been observed with the addition of Mn as well as with the capping of ZnO on ZnS:Mn. The formation of core-shell nanostructures have been also confirmed by FTIR analysis. Photoluminescence studies show that emission wavelength is red shifted with the addition of ZnO layer on ZnS:Mn(1 %). These core-shell ZnS:Mn/ZnO nano-composites will be a very suitable material for specific kind of tunable optoelectronic devices.
Structural and Optical Properties of Zno Nano Particles
IOSR Journal of Applied Physics, 2014
In the present report preliminary studies on synthesis and growth of ZnO nanocrystals have been reported. ZnO precursors were prepared by precipitation method from Zinc nitrate and Ammonia in aqueous solutions at a pH value9.0 .ZnO nanocrystals were then synthesized by heating the precursor in a muffle furnace at temp 350°C for 3 hours and allowed to cool to room temperature. The precursors and synthesized nanoparticles were characterized by X-Ray diffraction (XRD) and the results showed a single phase wurtzite structure for ZnO nanoparticles. It was found that the synthesized ZnO nanocrystals have wurtzite structures with a=b=3.214 Å and c=5.154 Å. Crystallite size was calculated using Debye_Scherrer's equation and the average crystallite size from first three peaks was found to be 55.18 nm. The morphology of prepared ZnO nanopowders was characterized by scanning electron microscope (SEM). From the compositional analysis by Energy dispersive analysis of X-ray (EDX) it was confirmed that Zinc and oxygen are present in the sample. Optical characterization was done to study other characters. Diffuse reflectance spectroscopy (DRS) results shows that the band gap of ZnO nanoparticles is 3.20eV.