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Query: KEGG:D01170 (ZnO)
 13,684 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This work reports a preliminary study of semiconductor-assisted photochemical degradation of lignin, Remazol Brilliant Blue R and Kraft E1 paper effluent by using ZnO and Ag-doped ZnO photocatalysts. The doped semiconductor was prepared in the reaction media by photoreduction of silver nitrate. With the use of 100 mg of ZnO and 15 mg of Ag-ZnO, almost total decolorization of the dye and lignin samples in reaction times lower than 60 min were observed. Extending the photochemical reaction up to 120 min, the total organic carbon content (TOC) was reduced in 90%. For the paper effluent, a fast decolorization was obtained for relatively short reaction times. However, de TOC reduction was negligible (near of 10%) up to high reaction times (300 min). By using the Ag-ZnO photocatalyst, the toxicity of lignin and Kraft E1 effluent toward E. Coli was completely removed. For the dye, the formation of transient toxic species was observed.
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PMID:Semiconductor-assisted photodegradation of lignin, dye, and kraft effluent by Ag-doped ZnO. 1066 9

Cu/Zn Hydroxycarbonates obtained by co-precipitation of Cu(2+) and Zn(2+) with Na(2)CO(3) have been investigated regarding phase formation and thermal decomposition in two series with varying Cu/Zn ratios prepared according to the decreasing pH and constant pH method. Hydrozincite, aurichalcite and (zincian)-malachite were found to form at differing Cu/Zn ratios for both series. For the constant pH preparation the Cu/Zn ratio in zincian-malachite was close to the nominal values whereas excess values were found for the decreasing pH samples. The degree of crystallinity as well as the thermal decomposition temperatures were lower for the constant pH series. All samples containing aurichalcite revealed an unexpected decomposition step at high temperatures evolving exclusively CO(2). The differences in composition and microstucture were traced back to the different pathways of solid formation for the two preparation methods. Substantial changes were observed during the post-precipitation processes of ageing and washing. The effects were studied in detail on samples with a cation ratio of Cu/Zn 70:30 mol %. Ageing of the precipitates in their own solutions is accompanied by a spontaneous crystallization of the initially amorphous solids. The decreasing pH sample develops from a hydroxy-rich material comprising basic copper nitrate (gerhardtite) as an intermediate. Only small changes in the chemistry of the samples were detected for the constant pH precipitation. The findings are summarised into a scheme of solid formation processes that explains the phenomenon of a "chemical memory" of the precipitates when they are converted into Cu/ZnO model catalysts.
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PMID:Relations between synthesis and microstructural properties of copper/zinc hydroxycarbonates. 1274 Aug 52

We report herein on the oriented growth of ZnO crystals on magnetite nanoparticles. The ZnO crystals were grown by hydrolyzing a supersaturated aqueous solution of zinc nitrate. The seeds for the growth were magnetite nanoparticles with a diameter of 5.7 nm and a narrow size distribution. Hollowed ZnO hexagons of 0.15 microm width and 0.5 microm length filled with Fe(3)O(4) particles were obtained. HR-TEM (high-resolution transmission electron microscopy) and selected-area EDS (energy-dispersive spectroscopy) show that the nanoparticles are homogenously spread in the ZnO tubes. Zeta potential measurements were employed to understand the relationship between the nanoparticles and the oriented growth of the ZnO crystals. The results show that the surfactants induced the directional growth of the ZnO crystals.
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PMID:Growing ZnO crystals on magnetite nanoparticles. 1505 72

The photocatalytic degradation of sulfamethazine (SMT), a sulfonamide drug, has been investigated in aqueous heterogeneous solutions containing n-type oxide semiconductors as photocatalysts. The disappearance of the organic molecule follows approximately a pseudo-first-order kinetics according to the Langmuir-Hinshelwood model. It was observed that, with TiO2 P-25 and ZnO as photocatalysts, quantitative degradation of the organic molecule occurs after 4 h. During this time the desulfurization of the substrate is complete, while only 30% of the nitrogen in the organic compound was recovered in the form of nitrate and ammonium ions, indicating that various other nitrogen-containing organic compounds remain in the solution. The addition of H2O2 leads, in the case of TiO2 P-25, to a twofold increase on the reaction rate, while a negative effect has been observed in the presence of ZnO. The initial apparent photonic efficiency (zeta0) of the photooxidation and the mineralization under various experimental conditions have been calculated.
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PMID:Photocatalytic oxidation of sulfamethazine. 1592 56

ZnO nanoparticles are synthesized using a new bio-friendly method. The experimental conditions are very mild: aqueous solution at near-neutral pH and 37 degrees C. The as-obtained nanoparticles show the stable wurtzite structure without the need of annealing. The two reagents used are aqueous solutions of zinc nitrate and buffer tris(hydroxymethyl)aminomethane. This is a standard nontoxic buffer and inert to a wide variety of chemicals and biomolecules, therefore extremely satisfactory for biochemical reactions. Furthermore, this is a polydentade ligand which adsorbs strongly on one or more surfaces of ZnO inhibiting its crystal growth and yielding nearly spherical ZnO nanoparticles. Our objective is to use the crystallization method described here for further incorporation of biomolecules as additives in the reaction solution, aiming at the formation of ZnO with new physical properties.
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PMID:Bio-friendly synthesis of ZnO nanoparticles in aqueous solution at near-neutral pH and low temperature. 1653 45

Highly oriented zinc oxide-surfactant hybrid multilayers were electrochemically self-assembled on silicon substrates from Zn(NO3)2 solutions containing extremely low concentration of sodium dodecyl sulfate (SDS). The X-ray diffraction results showed that the structure of the hybrid film is sensitive to the concentration of SDS. When the concentration of SDS is below a critical value, 0.002 wt %, a surfactant bilayer is adsorbed on the silicon surface, together with electrodeposited crystalline ZnO particles. Above this concentration, lamellar ZnO-surfactant hybrid films are formed, the period of which decreases from 31.7 +/- 0.2 A at 0.003 wt % to 27.5 +/- 0.2 A at 0.005 wt %, another critical concentration. It then increases monotonically and reaches its maximum of 33.0 +/- 0.2 A above 0.05 wt %. The results implied that the kinetics of the electrochemical self-assembly depends on the relative speed of the reduction of the zinc ions and the aggregation of the surfactant. The two processes occur cooperatively at the electrolyte-electrode interface to form the hybrid films.
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PMID:Electrochemical self-assembly of highly oriented ZnO-surfactant hybrid multilayers. 1685

A simple method of synthesizing nanomaterials and the ability to control the size and position of them are crucial for fabricating nanodevices. In this work, we developed a novel ammonia aqueous solution method for growing well-aligned ZnO nanorod arrays on a silicon substrate. For ZnO nanorod growth, a thin zinc metal seed layer was deposited on a silicon substrate by thermal evaporation. Uniform ZnO nanorods were grown on the zinc-coated silicon substrate in aqueous solution containing zinc nitrate and ammonia water. The growth temperature was as low as 60-90 degrees C and a 4-in. wafer size scale up was possible. The morphology of a zinc metal seed layer, pH, growth temperature, and concentration of zinc salt in aqueous solution were important parameters to determine growth characteristics such as average diameters and lengths of ZnO nanorods. We could demonstrate the discrete controlled growth of ZnO nanorods using sequential, tailored growth steps. By combining our novel solution method and general photolithography, we selectively grew ZnO nanorod arrays on a patterned silicon substrate. Our concepts on controlled ZnO nanorod growth using a simple solution method would be applicable for various nanodevice fabrications.
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PMID:Controlled growth of well-aligned ZnO nanorod array using a novel solution method. 1685 88

A simple chemical route for ZnS-coated ZnO nanowires with preferential (002) orientation is reported. Sodium sulfide and zinc nitrate were employed to supply S and Zn atoms at 60 degrees C to form ZnS-coated ZnO nanowires structures. Electron diffraction measurement shows that the ZnO/ZnS core-shell nanostructure is single crystalline. Interesting features are found in the photoluminescence (PL) spectra of ZnS-coated ZnO nanostructures. After coating, the UV emission of nanorods is dramatically enhanced at the expense of the green emission. The core/shell structure with higher band gap shell material and reduced surface states should be responsible for this PL enhancement.
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PMID:Enhanced ultraviolet emission from ZnS-coated ZnO nanowires fabricated by self-assembling method. 1686 73

We review two strategies for growing ZnO nanowires from zinc salts in aqueous and organic solvents. Wire arrays with diameters in the nanoscale regime can be grown in an aqueous solution of zinc nitrate and hexamethylenetetramine. With the addition of poly(ethylenimine), the lengths of the wires have been increased to 25 mum with aspect ratios over 125. Additionally, these arrays were made vertical by nucleating the wires from oriented ZnO nanocrystals. ZnO nanowire bundles have been produced by decomposing zinc acetate in trioctylamine. By the addition of a metal salt to the solution, the ZnO wires can be doped with a range of transition metals. Specifically, ZnO nanowires were homogeneously doped with cobalt and showed a marked deviation from paramagnetic behavior. We conclude by highlighting the use of these solution-grown nanowire arrays in dye-sensitized solar cells. The nanowire cells showed an improvement in the charge collection efficiency over traditional nanoparticle cells.
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PMID:Solution-grown zinc oxide nanowires. 1696 38

By kinetically controlled vapor-diffusion catalysis, nanostructured ZnO and Zn5(OH)8(NO3)3*2H2O thin films have been grown on substrates with different chemical compositions and varying degrees of crystallinity. The materials resulting from heterogeneous nucleation under mild conditions (starting from aqueous metal salt precursor solutions at room temperature) were characterized by X-ray diffraction and scanning electron microscopy to determine the influence of the substrates on the overall chemical composition, crystallinity, and morphology of the films.
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PMID:Substrate-induced growth of nanostructured zinc oxide films at room temperature using concepts of biomimetic catalysis. 1710 69


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