Zinc Oxide Nanopowders Research Articles

Photoluminescence of zinc oxide nanopowder synthesized by a combustion method

Zinc oxide (ZnO) nanopowder was synthesized by a simple and quick combustion method using zinc nitrate as a precursor and glycine as a fuel material. The starting materials were mixed at room temperature and spontaneous ignition of which resulted into the ZnO nanopowder. The synthesized nanopowder was characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), Infrared (IR) spectrophotometer and spectroflurometer in order to study the structural, morphological, compositional and photoluminescence (PL) properties. The ZnO powder shows polycrystalline nature with preferential peak (101) having crystallite size 25 nm. A significant band at 532 cm −1 in the IR spectrum corroborates the presence of characteristic band of ZnO. Room temperature photoluminescence spectrum of the synthesized nanopowder exhibits a dominant, sharp and strong ultraviolet (UV) emission with a suppressed deep-level emission indicating good crystal quality and optical properties.

Synthesis of ZnO nanoparticles through the impregnated layer combustion synthesis process

Zinc oxide nanopowders were synthesized by a solution combustion technique named impregnated layer combustion synthesis (ILCS), involving the impregnation of an active layer with the reactant solution and subsequently the combustion of the impregnated system. In this work three different organic fuels and two different ignition modes were tested in order to optimize the final microstructure and specific surface area (SSA) of the ZnO nanopowders. In particular, the ignition mode was found to significantly affect the final products, discriminating between an explosion procedure (flame combustion) and a self-propagating mode (smoldering combustion). The nitrate–glycine mixture and the smoldering combustion way were found to be the most suitable conditions, giving rise to softly agglomerated nanopowders with an average size of 20 nm and a very high SSA, without the need of any further crystallization treatment.

Optical and electrical properties of aluminum-doped zinc oxide nanoparticles

Aluminum-doped zinc oxide nanopowders were prepared using a surfactant assisted complex sol–gel method, and were characterized using inductively coupled plasma, X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and UV–Vis spectroscopy. Al was effectively doped into the ZnO matrix with concentrations up to 6.00 atomic ratio percents (at.%). X-ray diffraction results revealed that all of the nanoparticles had a pure hexagonal wurtzite structure free of any impurities when annealing temperature was below 1273 K. The optical band gap of the nanopowders, which was affected by the Al-doping concentration, reached a maximum of 3.43 eV when ZnO was doped with 4.00 at.% Al. The effect of post-annealing temperature and vacuum conditions on the resistivities of the Al-doped ZnO nanoparticles was also investigated. And the lowest volume resistivity (1.2 Ω cm) was achieved by annealing the Al-doped ZnO nanoparticles in a vacuum at 1173 K for 2 h.

Structural and optical properties of zinc oxide nanopowders doped with Mn

AbstractPure ZnO and Zn1‐xMnxO (x = 0, 0.02, 0.06, 0.10, 0.15) nanopowders have been synthesized by sol gel technique at low temperatures. XRD results indicate that the powder has a hexagonal polycrystalline structure without secondary phases. The nanopowders were characterized using the X‐ray diffraction (XRD) and transmission electron microscopy (TEM) observation. Kramers‐Kronig's analysis of mid‐IR reflectance spectra were employed to determine the doping effect on the optical constants and optical phonon modes frequencies. The optical band gap energy decreases from 3.22 eV to 3.12 eV for pure ZnO and Zn0.9Mn0.1O dispersed powders, respectively (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Structural and optical properties of ZnO nanopowder prepared by microwave-assisted synthesis

We report the characterization of nano-size zinc oxide (ZnO) powder synthesized via microwave-assisted heating of Zn(CH 3COO) 2·2H 2O and NaHCO 3 solution with deionized water (DI water) as the solvent. The as-synthesized ZnO powder was calcined at temperatures from 400 to 800 °C for 8 h. The X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) spectra revealed pure wurtzite structure for the ZnO nanopowder (NP) calcined at 800 °C. Scanning electron microscopy (SEM) images showed increasing size ZnO NP with uniform size distribution with increase in calcination temperature. Significant UV emission at about 373 nm has been observed in the photoluminescence (PL) spectra of the as-synthesized and calcined ZnO NP. Our results showed enhanced PL intensity with a reduced full-width at half-maximum (FWHM) for ZnO NP synthesized at higher calcination temperature.

Mild Synthetic Routes to High‐Surface Zinc Oxide Nanopowders

High-surface wurtzite ZnO nanopowders were obtained by thermal decomposition of two different precursors at 90 °C for 150 h: (i) commercial zinc acetate dihydrate and (ii) a solid mixture obtained after evaporation of a solution of zinc acetate in aqueous ammonia. The proposed methods are mild and involve very simple equipment.

Ultra fast synthesis of zinc oxide nanostructures by microwaves

We describe a novel route for the synthesis of nanostructured zinc oxide powder using a modified kitchen microwave. A SiC-based composite showing a very strong absorption of microwaves was used as a microwave heater. Tests showed that high temperatures exceeding 1700 ∘C can be reached in less than hundred second exposure of the composite material of microwaves. Zinc oxide nanopowder was obtained by evaporation and oxidation of metallic zinc in the ambient atmosphere of the microwave oven. Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) techniques revealed the prepared powder includes a wide variety of nanostructures including nanoparticles, nanosheets and tetrapods.

Preparation of ZnO nanopowders by thermal plasma and characterization of photo-catalytic property

Nano-sized zinc oxide (ZnO) powders were prepared via a thermal plasma process from micro-sized zinc powder while oxygen was employed as a reaction gas. Two different carrier gases, oxygen and argon, were evaluated and the flow rate of the reaction gas was controlled. The photo-catalytic activities of ZnO powders were evaluated by measuring the degradation of methylene blue (MB) in water under the UV and visible region. The prevailing goal of this study is to improve the photo-catalytic activity of nano-sized ZnO powders for the removal of environmental pollutants. The ZnO nanopowders were characterized by XRD, SEM, BET, and UV–vis spectrometry. Their mean crystallites sizes ranged from 26.5 nm to 48.6 nm. It was confirmed by a XRD analysis that the ZnO nanopowders had a high quality wurtzite structure. SEM and XRD results show that the size of the particles synthesized increased with an increase of the flow rate of the oxygen reaction gas. The powder obtained using the argon carrier gas with higher oxygen reaction gas flow rate was more rod-shape. The MB decomposition rates of the obtained ZnO nanopowders were studied under the UV and visible region. In the UV region, synthesized ZnO could decompose MB as well as commercial ZnO. However, in the visible region, the MB decomposition rate obtained using ZnO was much higher than that by commercial ZnO.

Photocatalytic Removal of Cu Ions from Aqueous Cu-EDTA Solution Using Solution Combusted Zinc Oxide Nanopowder

Nano-sized ZnO powder was prepared by "solution-combustion method (SCM)." The ZnO powder using Zn(OH)2 and glycine as an oxidant and a fuel (F/O = 0.8), showed good powder characteristics, such as average grain size of 30 nm and the specific surface area of 120 m2/g. and it was used as a semiconductor photocatalyst to remove Cu ions from aqueous Cu-EDTA solution. The result was then compared with other semiconductor photocatalyst powders such as titanium dioxide (TiO2) powder (P25, Degussa) and TiO2 powder prepared by homogeneous precipitation process at low temperature (HPPLT). The SCM ZnO nanopowder showed excellent photocatalytic properties. The Cu++ ions were completely removed from the solution within 90 min. However, for the other two powders, no complete removal of the ions was observed within the reaction time of 180 min. The ZnO powder synthesized at the fuel/oxidant ratio of 0.8, showed higher PL intensity at UV region than the other photocatalytic powders. The superior photoreduction ability of SCM ZnO nanopowder might be due to its excellent UV absorption capacity.

Synthesis of zinc oxide nanopowder and nanolayer via chemical processing

In the present research work, the newest economic method for synthesis of ZnO nanopowder has been carried out via solochemical processing from an aqueous solution of a zinc-containing complex. The results obtained from XRD and TEM show that the nanoparticles are single crystals and have elongated particulate shape with a narrow size distribution. Solochemical processing can thus be an attractive method for industrial production of the nanopowders. The highly textured ZnO thin film with a preferred (002) orientation was also prepared by Two-Stage Chemical Deposition (TSCD), using an aqueous solution containing zinc complex on a soda-lime glass substrate. The films were characterised by XRD, SEM, EDAX, optical spectrophotometer and FTIR to justify the suitability for commercial device quality.

Correlation between microstructure and optical properties of ZnO nanoparticles synthesized by ball milling

Zinc oxide (ZnO) nanoparticles (NPs) in the size range ∼7–35 nm are synthesized by ball-milling technique, and microstructural and optical properties of the NPs are studied using varieties of techniques. Results from ball-milled NPs are compared with those of the commercially available ZnO nanopowder. X-ray diffraction pattern of the milled NPs indicates lattice strain in the NPs. High-resolution transmission electron microscopy analysis reveal severe lattice distortion and reduction in lattice spacing in some of the NPs. Optical absorption spectra of milled NPs show enhanced absorption peaked at 368 nm, which is blueshifted with reference to starting ZnO powder. Room-temperature photoluminescence spectra show five peaks consisting of ultraviolet and visible bands, and relative intensity of these peaks drastically changes with increasing milling time. Raman spectra of milled powders show redshift and broadening of the Raman modes of ZnO, and a new Raman mode evolve in the milled NPs. A correlation between the microstructure and optical properties of ZnO NPs is made on the basis of these results. Our results clearly demonstrate that commercially available ZnO nanopowders do not exhibit nanosize effects due to relatively large size of the ZnO NPs. Implications of these results are discussed.

Morphology and luminescence properties of zinc oxide nanopowders doped with aluminum ions obtained by hydrothermal and vapor condensation methods

In this paper, we analyze the influence of Al doping on microstructure and light emission efficiency of ZnO nanoparticles obtained by the hydrothermal method and after vapor condensation method, where vaporization of the precursor powders was caused by high solar energy and subsequent deposition. We report an increase of lattice parameters with increasing level of doping as well as large emission enhancement, which we relate to surface passivation of recombination mechanisms and/or plasmon mechanism of photoluminescence stimulation.

Preparation and Characterization of Gallium-Doped Zinc Oxide Nanopowders with High Electrical Conductivity

Gallium-doped zinc oxide nanopowders with high electrical conductivity were prepared by calcining the precursor synthesized from ZnSO4·7H2O, GaCl3 and NH4HCO3 by co-precipitation method. The obtained samples were characterized by FE-SEM, TEM, XRD, XPS and BET techniques. The precursor particles were in the shape of sheet-like with size about several hundred nanometers. The electrically conductive zinc oxide particles, in the shape of sphere-like, were about 10~40 nm with low agglomeration, and the specific surface area was 28.7 m2/g. XRD and XPS results showed that all the doped Ga exists as the substitution form of Ga• Zn in the ZnO system. The volume resistivity of the product was as lower as 4.5 :·cm.

Polystyrene nanocomposite materials—Preparation, mechanical, electrical and thermal properties, and morphology

AbstractThis work prepared polystyrene resin nanocomposites with antistatic properties, by melt‐blending polystyrene with nanoscale zinc oxide. The effect of nanoscale zinc oxide on the electrical and physical characteristics of polystyrene nanocomposites was investigated. Two kinds of nanoscale powders, spherical zinc oxide (s‐ZnO) and zinc oxide whisker (w‐ZnO), were selected. The coupling agents, vinyltriethoxysilane and phenyltriethoxysilane, were utilized to improve the compatibility between nanopowders and polystyrene resin. Adding spherical zinc oxide and zinc oxide whisker improved the antistatic characteristic of materials. The surface resistivities of s‐ZnO and w‐ZnO nanocomposite were significantly reduced, by modification with vinyltriethoxysilane and phenyltriethoxysilane. Adding zinc oxide nanopowder increased the flexural modulus and reduces flexural strength. Silane coupling agent improved the flexural properties of nanocomposite. The glass transition temperature and thermal degradation temperature of zinc oxide/polystyrene nanocomposite increased with ZnO content. Treatment with silane increased the glass transition temperature and thermal degradation temperature of composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 508–515, 2006

Polystyrene nanocomposite materials: Preparation, morphology, and mechanical, electrical, and thermal properties

AbstractIn this study, we prepared polystyrene (PS) resin nanocomposites with antistatic properties by melt‐blending PS with nanoscale zinc oxide (ZnO). The effects of nanoscale ZnO on the electrical and physical characteristics of the PS nanocomposites were investigated. Two kinds of nanoscale powders, spherical zinc oxide (s‐ZnO) and zinc oxide whisker (w‐ZnO), were selected. The coupling agents vinyltriethoxysilane (VTES) and phenyltriethoxysilane (PTES) were used to improve the compatibility between the nanopowders and PS resin. The addition of s‐ZnO and w‐ZnO improved the antistatic characteristics of the materials. The surface resistivities of the s‐ZnO and w‐ZnO nanocomposites were significantly reduced by modification with VTES and PTES. The addition of ZnO nanopowder increased the flexural modulus and reduced the flexural strength. The silane coupling agents improved the flexural properties of the nanocomposites. The glass‐transition temperatures and thermal degradation temperatures of the ZnO/PS nanocomposites increased with ZnO content. Treatment with silane increased the glass‐transition temperatures and thermal degradation temperatures of the composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2266–2273, 2005

Removal of Cu<sup>++</sup> Ions from Aqueous Cu-EDTA Solution Using ZnO Nanopowder

Nanometer size zinc oxide (ZnO) powder was prepared by a novel “solution-combustion method (SCM)”, and it was used as a semiconductor photocatalyst to evaluate its photoreduction properties. Aqueous solution of heavy metal ions (Cu-EDTA) was used for the photocatalysis reaction under UV illumination. The result was then compared with other semiconductor photocatalyst powders such as titanium dioxide (TiO2) powder (P25; Degussa) and TiO2 powder prepared by a homogeneous precipitation process at low temperature (HPPLT). The zinc oxide nanopowder showed the highest removal rate of the Cu++ ions from the solution among the photocatalyst powders compared. The superior photoreduction ability of the ZnO nanopowder appears to be due to its excellent UV absorption capacity.

Photocatalytic Silver Recovery Using ZnO Nanopowders Synthesized by Modified Glycine‐Nitrate Process

Zinc oxide (ZnO) powders were synthesized by the modified glycine‐nitrate process (MGNP) with various oxidants and fuels. Single‐phase ZnO powders were easily obtained regardless of oxidants and fuels. The particle size and shape of ZnO powders were dependent on the types of fuels. The ZnO powder synthesized using Zn(OH)2 and glycine as an oxidant and a fuel, at a fuel/oxidant ratio of 0.8, showed the best powder characteristics, such as an average grain size of 30 nm and the specific surface area of 120 m2/g. The removal of silver ions from the waste‐development solution was tried to confirm photocatalytic activities of the synthesized ZnO powder. The silver ions were completely removed within 15 min. This silver recovery rate is three times higher than that of commercial state‐of‐the‐art TiO2. The photoluminescence (PL) measurement also showed the PL intensity at ultraviolet (UV) of the synthesized ZnO powder is almost three times higher than that of commercial state‐of‐the‐art TiO2. The synthesized ZnO nanopowder absorbed more UV than any other powders, including commercial state‐of‐the‐art TiO2 and ZnO powders. This means the high UV absorption efficiency leads to the generation of more electrons that are involved in the reduction of silver ions.

In Situ Synthesis of Polymer Nanocomposite Electrolytes Emitting a High Luminescence with a Tunable Wavelength

Zinc oxide (ZnO) nanoparticle-based nanocomposite polymer electrolytes with a very high luminescence intensity were prepared by an in situ method, in which ZnO nanoparticle fillers were grown in the polymer matrix and ion carriers were inserted during the growth of the nanoparticles (contributed by a precursor). By using a high concentration of lithium hydroxide (LiOH) as the precursor, the remaining unreacted LiOH was distributed in the form of an amorphous complex around the produced ZnO nanoparticles, thus preventing the agglomeration of the nanoparticles. This resulted in a high number concentration of ZnO nanoparticles that serve as luminescent centers for inducing a high luminescence intensity. Compared to samples prepared using the usual concentration of LiOH (about 0.14 M), the luminescence intensity was enhanced by about 22 times for the ZnO nanopowder and 6 times for the nanocomposite polymer electrolytes (poly(ethylene glycol)/ZnO/Li+) when a LiOH concentration of 0.35 M was used.

Preparation of Zinc Oxide Nanopowder by Freeze-Drying

Preparation of Zinc Oxide Nanopowder by Freeze-Drying

Preparation of Zinc Oxide Nanopowder by Freeze-Drying

Preparation of Zinc Oxide Nanopowder by Freeze-Drying