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Pure ZnO (pure + zno)

Distribution by Scientific Domains

Physics and Astronomy	80%

Selected Abstracts

Influence of molecular adsorbates on the structure of electrodeposited nanocrystalline ZnO

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2008
T. Loewenstein
Abstract Pure ZnO or ZnOEosinY with adsorbed EosinY molecules was deposited electrochemically from aqueous zinc salt solutions on (0001)GaN and (0001)ZnO. X-ray diffraction revealed the deposition of crystalline ZnO in all cases, with almost perfect orientation in the c -direction. Shifts in the peak positions observed for ZnOEosinY were explained by a lattice expansion by 3.6% in the c -direction caused by the strong influence of the EosinY molecules adsorbed during the growth of ZnO. Scanning electron microscopy (SEM) was used to elucidate the film morphology. Photoluminescence measurements served to determine changes in the electronic structure of these nanocrystalline materials. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Facile and Reproducible Synthesis of Nanostructured Colloidal ZnO Nanoparticles from Zinc Acetylacetonate: Effect of Experimental Parameters and Mechanistic Investigations

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 33 2009
Alessia Famengo
Abstract A facile and reproducible route to nanostructured colloidal ZnO nanoparticles was developed by controlled hydrolysis and condensation of zinc acetylacetonate in alkaline conditions. By reaction of an ethanolic solution of Zn(acac)2 with NaOH in a 1:2 molar ratio, after reflux, ZnO spherical nanoparticles were obtained that displayed a homogeneous size distribution; particle diameters ranged from 6 to 10 nm, as evidenced by transmission electron microscopy (TEM) analysis. The same reaction was carried out also in water, glycerol and 1,2-propanediol, to investigate the effect of the solvent viscosity and dielectric constant on the final features of the obtained material. Irrespective of the nature of the solvent, X-ray diffraction (XRD) analysis shows the formation ofhexagonal ZnO, whereas the presence of residual unreacted Zn(acac)2 could be ruled out. Indeed, different particle sizes and very different morphologies were obtained. Also the reflux step was shown to be a key factor in avoiding the fast precipitation of a floc and achieving a pure compound, which was isolated and thoroughly characterised. The composition of the obtained ZnO was determined by elemental analysis, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), showing the formation of pure ZnO. IR spectroscopy evidenced the presence of adsorbed organic ligands on the colloid surfaces. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) revealed the presence of medium- to high-strength acidic sites on the ZnO surface. To gain a deeper insight into the formation mechanisms of these nanostructures, time-resolved UV/Vis and XAS studies were performed on the ethanol solution used for the synthesis of the oxide and also on the solid specimen, obtained after the refluxing step. No remarkable changes could be evidenced in the solution after the addition of an understoichiometric amount of NaOH, but the growth of the ZnO nanoparticles could be followed by UV/Vis spectra. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Solvothermal fabrication of ZnO nanorods using ethanolic quantum dot precursors

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2009
Yukihiro Hara
Abstract ZnO nanorods were obtained by solvothermal reaction using quantum dot precursors suspended in ethanol. The ZnO suspensions were prepared from ethanolic zinc acetate solutions in the presence of lithium hydroxide, and treated by solvothermal synthesis under different reaction temperatures and duration times. Parameters of processing of these nanorods were investigated, including the concentration of precursors and solvothermal temperature. The ZnO nanorod powders were characterized by XRD, SEM, TEM, FT-IR, thermal analysis, and isothermal N2(g) adsorption analyses. Commercially available ZnO nanopowders were studied for comparison. Resulting ZnO nanorod powders were pure ZnO and showed higher surfaces area than commercial ZnO nanopowders. Length and diameter of ZnO nanorods depended on the concentration of precursors and the annealing temperature employed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Dependence of structural and optical properties of Zn1,xCdxO films on the Cd composition

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 13 2004
D. W. Ma
Abstract Zn1,xCdxO alloy semiconductors have great latent applications in short wavelength optoelectronic devices. By the dc reactive magnetron sputtering technique, ternary single-phased Zn1,xCdxO (0 , x , 0.53) alloy crystalline films were prepared on glass and sapphire substrates. For x = 0, 0.20, 0.36, 0.53, the band-gaps of the Zn1,xCdxO alloy films were estimated as 3.28, 3.21, 3.11 and 2.65 eV, respectively. Photoluminescence spectrum shows that the near-band-edge energy of the Zn0.8Cd0.2O film has a red-shift of 0.14 eV from that of pure ZnO reported previously. The green-yellow emission in the photoluminescence spectrum is assumed to mainly related to electron transitions from the single ionized oxygen vacancies (Vo+) to Zn, Cd vacancies (VZn,, VC,d), or oxygen interstice (Oi,). (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Pressure dependence of the optical properties of wurtzite and rock-salt Zn1,xCoxO thin films

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2007
J. A. Sans
Abstract In this paper we investigate the electronic structure of Zn1,xCoxO by means of optical absorption measurements under pressure. Thin films of Zn1,xCoxO with different Co content (from 1 to 30%) were prepared by pulsed laser deposition on mica substrates. Absorption spectra exhibit three main features that are clearly correlated to the Co content in the films: (i) absorption peaks in the infrared associated to crystal-field-split internal transitions in the Co 3d shell, with very small pressure coefficients due to their atomic character; (ii) a broad absorption band below the fundamental edge associated to charge transfer transitions, that exhibit relatively large pressure coefficients, indicating that the Co 3d final states must be strongly hybridized to the conduction band; and (iii) a blue-shifted fundamental absorption edge associated to band to band transitions with a pressure coefficient close to that of pure ZnO. In the up-stroke the transition pressure from wurtzite to rock-salt phase decrease almost linearly as the Co increases, from 9.5 GPa in pure ZnO to about 6.5 GPa for x = 30%. In the down-stroke pressure we observe a similar behavior, yielding a metastable rock-salt phase at room pressure, after a pressure cycle up to 15 GPa. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]