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Showing papers on "Zinc published in 2008"


Journal ArticleDOI
TL;DR: The performance and stability of unencapsulated inverted bulk-heterojunction solar cells with zinc oxide (ZnO) made by different processes as the electron selective contact are compared to conventional bulk-hear junction solar cells as mentioned in this paper.
Abstract: The performance and stability of unencapsulated inverted bulk-heterojunction solar cells with zinc oxide (ZnO) made by different processes as the electron selective contact are compared to conventional bulk-heterojunction solar cells. The low temperature processed inverted devices using ZnO nanoparticles on indium tin oxide plastic substrates showed high power conversion efficiency of ∼3.3%. This inverted device structure possessed much better stability under ambient conditions retaining over 80% of its original conversion efficiency after 40days while the conventional one showed negligible photovoltaic activity after 4days. This is due to the improved stability at the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/Ag interface.

837 citations


Journal ArticleDOI
TL;DR: Results show that hollow spheres can be more readily separated from the slurry system by filtration or sedimentation after photocatalytic reaction and reused than conventional powder photocatalyst, confirming ZnO hollow spheres is stability and not photocorroded.
Abstract: ZnO hollow spheres with porous crystalline shells were one-pot fabricated by hydrothermal treatment of glucose/ZnCl2 mixtures at 180 °C for 24 h, and then calcined at different temperatures for 4 h. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption−desorption isotherms. The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic decolorization of Rhodamine B aqueous solution at ambient temperature. The results indicated that the average crystallite size, shell thickness, specific surface areas, pore structures, and photocatalytic activity of ZnO hollow spheres could be controlled by varying the molar ratio of glucose to zinc ions (R). With increasing R, the photocatalytic activity increases and reaches a maximum value at R = 15, which can be attributed to the combined effects of several factors such as specific surface area, the porous structure and the crystallite size. Further...

765 citations


Journal ArticleDOI
TL;DR: The studies in the cell culture models showed that the activation of many zinc-dependent enzymes and transcription factors were adversely affected due to zinc deficiency, and zinc supplementation decreased oxidative stress markers and generation of inflammatory cytokines.
Abstract: Although the essentiality of zinc for plants and animals has been known for many decades, the essentiality of zinc for humans was recognized only 40 years ago in the Middle East. The zinc-deficient patients had severe immune dysfunctions, inasmuch as they died of intercurrent infections by the time they were 25 years of age. In our studies in an experimental human model of zinc deficiency, we documented decreased serum testosterone level, oligospermia, severe immune dysfunctions mainly affecting T helper cells, hyperammonemia, neurosensory disorders, and decreased lean body mass. It appears that zinc deficiency is prevalent in the developing world and as many as two billion subjects may be growth retarded due to zinc deficiency. Besides growth retardation and immune dysfunctions, cognitive impairment due to zinc deficiency also has been reported recently. Our studies in the cell culture models showed that the activation of many zinc-dependent enzymes and transcription factors were adversely affected due to zinc deficiency. In HUT-78 (T helper 0 (Th0) cell line), we showed that a decrease in gene expression of interleukin-2 (IL-2) and IL-2 receptor α (IL-2Rα) were due to decreased activation of nuclear factor-κB (NF-κB) in zinc deficient cells. Decreased NF-κB activation in HUT-78 due to zinc deficiency was due to decreased binding of NF-κB to DNA, decreased level of NF-κB p105 (the precursor of NF-κB p50) mRNA, decreased κB inhibitory protein (IκB) phosphorylation, and decreased Iκκ. These effects of zinc were cell specific. Zinc also is an antioxidant and has anti-inflammatory actions. The therapeutic roles of zinc in acute infantile diarrhea, acrodermatitis enteropathica, prevention of blindness in patients with age-related macular degeneration, and treatment of common cold with zinc have been reported. In HL-60 cells (promyelocytic leukemia cell line), zinc enhances the up-regulation of A20 mRNA, which, via TRAF pathway, decreases NF-κB activation, leading to decreased gene expression and generation of tumor necrosis factor-α (TNF-α), IL-1β, and IL-8. We have reported recently that in both young adults and elderly subjects, zinc supplementation decreased oxidative stress markers and generation of inflammatory cytokines.

668 citations


BookDOI
01 Jan 2008

582 citations


Journal ArticleDOI
06 Mar 2008-Nature
TL;DR: Despite lack of sequence homology, CDCA is a structural mimic of a functional β-carbonic anhydrase dimer, with striking similarity in the spatial organization of the active site residues.
Abstract: Carbonic anhydrase, a zinc enzyme found in organisms from all kingdoms, catalyses the reversible hydration of carbon dioxide and is used for inorganic carbon acquisition by phytoplankton. In the oceans, where zinc is nearly depleted, diatoms use cadmium as a catalytic metal atom in cadmium carbonic anhydrase (CDCA). Here we report the crystal structures of CDCA in four distinct forms: cadmium-bound, zinc-bound, metal-free and acetate-bound. Despite lack of sequence homology, CDCA is a structural mimic of a functional beta-carbonic anhydrase dimer, with striking similarity in the spatial organization of the active site residues. CDCA readily exchanges cadmium and zinc at its active site--an apparently unique adaptation to oceanic life that is explained by a stable opening of the metal coordinating site in the absence of metal. Given the central role of diatoms in exporting carbon to the deep sea, their use of cadmium in an enzyme critical for carbon acquisition establishes a remarkable link between the global cycles of cadmium and carbon.

491 citations


Journal ArticleDOI
TL;DR: In this paper, activated carbon was prepared from hazelnut husks with zinc chloride activation at 973 K in nitrogen atmosphere and the activation surface area was found 1092 m2g−1.

456 citations


Journal ArticleDOI
TL;DR: Zinc deficiency was suspected to occur in Iranian patients with growth retardation, hypogonadism in males, hepato-splenomegaly, rough and dry skin, geophagia and severe iron deficiency anemia, and zinc deficiency in similar patients in Egypt, which were documented.

397 citations


Journal ArticleDOI
TL;DR: Al-doped zinc oxide (ZnO) thin films were prepared by chemical spray pyrolysis technique and structural analysis of the films revealed that all the films are of polycrystalline zinc oxide in nature, possessing hexagonal wurtzite structure with (0,0,2) preferred orientation.
Abstract: Al-doped zinc oxide (ZnO) thin films were prepared by chemical spray pyrolysis technique. The dopant concentration (Al/Zn at%) varied from 0 to 1.5 at%. Structural analysis of the films reveals that all the films are of polycrystalline zinc oxide in nature, possessing hexagonal wurtzite structure with (0 0 2) preferred orientation. The lattice constants calculated from the most prominent peaks are found to be in good agreement with the ICDD reference pattern: zinc oxide, 01-080-0074 (a = 3.2535 A and c = 5.2151 A). The sensing properties of the films towards methanol vapour are investigated for various concentrations of methanol in air at different operating temperatures in the range 200–350 °C. It is observed that compared to the undoped ZnO film, Al-doped films show higher sensitivity to methanol vapour. Among all the Al-doped films studied, the 0.5 at% Al-doped ZnO film shows the maximum response (∼44%) at 275 °C to 500 ppm of methanol vapour in air. Further, the films show fast response and recovery to methanol vapour at higher operating temperatures. The methanol-sensing mechanism of the film has been explained.

358 citations


Journal ArticleDOI
TL;DR: In this paper, the powder X-ray diffraction (XRD) patterns confirm the single phase spinel structure for the synthesized materials and the crystallite size was calculated from the most intense peak (3-1-1) using the Scherrer formula.

339 citations


Journal ArticleDOI
15 Jul 2008-Talanta
TL;DR: The bismuth-modified carbon nanotube electrode was successfully applicable to analysis of trace metals in real environments and presented well-defined, reproducible and sharp stripping signals.

297 citations


Journal ArticleDOI
TL;DR: A novel "naked-eye" and ratiometric fluorescent zinc sensor (AQZ) of carboxamidoquinoline with an alkoxyethylamino chain as receptor was designed and synthesized and shows good water solubility and high selectivity for sensing.

Journal ArticleDOI
TL;DR: This initial investigation suggests that chemicals emerging from nanotechnology may pose a risk to aquatic life in water column and sediment compartments and that further studies on their adverse effects are to be encouraged.
Abstract: Present knowledge concerning the ecotoxic effects of nano-materials is very limited and merits to be documented more fully. For this purpose, we appraised the toxicity of nine metallic nano-powders (copper zinc iron oxide, nickel zinc iron oxide, yttrium iron oxide, titanium dioxide, strontium ferrite, indium tin oxide, samarium oxide, erbium oxide, and holmium oxide) and of two organic nano- powders (fullerene-C60 and single-walled carbon nanotube or SWCNT). After a simple process where nano-powders (NPs) were prepared in aqueous solution and filtered, they were then bioassayed across several taxonomic groups including decomposers (bacteria), primary producers (micro-algae), as well as primary and secondary consumers (micro-invertebrates and fish). Toxicity data generated on the 11 NPs reflected a wide spectrum of sensitivity that was biological level-, test-, and endpoint-specific. With all acute and chronic tests confounded for these 11 NPs, toxicity responses spanned over three orders of magnitude: >463 mg/L (24 h LC50 of the invertebrate Thamnoplatyurus platyurus for fullerene-C60) / 0.3 mg/L (96 h EC50 of the invertebrate Hydra attenuata for indium tin oxide), that is a ratio of 1543. On the basis of the MARA (Microbial Array for Risk Assessment) assay toxic fingerprint concept, it is intimated that NPs may have different modes of toxic action. When mixed in a 1:1 ratio with a certified reference material (CRM) sediment, two solid phase assays and an elutriate assay, respectively, showed that five NPs (copper zinc iron oxide, samarium oxide, erbium oxide, holmium oxide, and SWCNT) were able to increase both CRM sediment toxicity and its elutriate toxicity. This initial investigation suggests that chemicals emerging from nanotechnology may pose a risk to aquatic life in water column and sediment compartments and that further studies on their adverse effects are to be encouraged.

Journal ArticleDOI
TL;DR: This review outlines steps to estimate the prevalence of inadequate intakes, and confirm their validity based on the EARs set by International Zinc Nutrition Collaborative Group, and the appropriateness of serum zinc as a biochemical marker for population zinc status.
Abstract: The role of zinc deficiency as an important cause of morbidity and impaired linear growth has prompted the need to identify indicators of population zinc status. Three indicators have been recommended - prevalence of zinc intakes below the estimated average requirement (EAR), percentage with low serum zinc concentrations, and percentage of children aged < 5 years who are stunted. This review outlines steps to estimate the prevalence of inadequate intakes, and confirm their validity based on the EARs set by International Zinc Nutrition Collaborative Group. Next, the appropriateness of serum zinc as a biochemical marker for population zinc status is confirmed by a summary of: (a) the response of serum zinc concentrations to zinc intakes; (b) usefulness of serum zinc concentrations to predict functional responses to zinc interventions; (c) relationship between initial serum zinc and change in serum zinc in response to interventions. Height- or length-for-age was chosen as the best functional outcome after considering the responses of growth, infectious diseases (diarrhoea, pneumonia), and developmental outcomes in zinc supplementation trials and correlation studies. The potential of other zinc biomarkers such as zinc concentrations in hair, cells, zinc-metalloenzymes, and zinc-binding proteins, such as metallothionein, is also discussed. Molecular techniques employing reverse transcriptase (RT)-polymerase chain reaction to measure mRNA in metallothionein and ZIP1 transporter hold promise, as do kinetic markers such as exchangeable zinc pools (EZP) and plasma zinc turnover rates. More research is needed to establish the validity, specificity, sensitivity, and feasibility of these new biomarkers, especially in community-settings.

Journal ArticleDOI
TL;DR: In this article, the performance of model zinc-magnesium alloys was studied to understand better the protective mechanism of magnesium in zinc, and the improved corrosion stability of ZnMg alloys were connected to the presence of an Mg-based film adjacent to the metal surface.

Journal ArticleDOI
TL;DR: In this article, the effect of various parameters like concentration of substrate, amount of photocatalyst, pH and irradiation time on the efficiency of degradation of phenol was studied.

Journal ArticleDOI
TL;DR: It is demonstrated that an increase of the intracellular zinc ion concentration occurs upon stimulation of human leukocytes with Escherichia coli, LPS, Pam3CSK4, TNF-α, or insulin, predominantly in monocytes, and this function of Zn2+ is not limited to monocytes or even the immune system, but seems to be another generalized signaling system based on intrACEllular fluctuations of metal ion concentrations, acting parallel to Ca2+.
Abstract: Cytosolic alterations of calcium ion concentrations are an integral part of signal transduction. Similar functions have been hypothesized for other metal ions, in particular zinc (Zn(2+)), but this still awaits experimental verification. Zn(2+) is important for multiple cellular functions, especially in the immune system. Among other effects, it influences formation and secretion of pro-inflammatory cytokines, including TNF-alpha. Here we demonstrate that these effects are due to a physiological signaling system involving intracellular Zn(2+) signals. An increase of the intracellular zinc ion concentration occurs upon stimulation of human leukocytes with Escherichia coli, LPS, Pam(3)CSK(4), TNF-alpha, or insulin, predominantly in monocytes. Chelating this zinc signal with the membrane permeable zinc-specific chelator TPEN (N,N,N',N'-tetrakis-(2-pyridyl-methyl)ethylenediamine) completely blocks activation of LPS-induced signaling pathways involving p38 MAPK, ERK1/2, and NF-kappaB, and abrogates the release of proinflammatory cytokines, including TNF-alpha. This function of Zn(2+) is not limited to monocytes or even the immune system, but seems to be another generalized signaling system based on intracellular fluctuations of metal ion concentrations, acting parallel to Ca(2+).

Journal ArticleDOI
TL;DR: Comparisons of X-ray crystal structures of free and fatty-acid bound human serum albumin suggest that zinc binding to this site and fatty acid binding to one of the five major sites may be interdependent, and interactive binding of zinc and long-chain fatty acids to albumin may have physiological implications.
Abstract: Although details of the molecular mechanisms for the uptake of the essential nutrient zinc into the bloodstream and its subsequent delivery to zinc-requiring organs and cells are poorly understood, it is clear that in vertebrates the majority of plasma zinc (9–14 μM; approx. 75–85%) is bound to serum albumin, constituting part of the so-called exchangeable pool. The binding of metal ions to serum albumins has been the subject of decades of studies, employing a multitude of techniques, but only recently has the identity and putative structure of the major zinc site on albumin been reported. Intriguingly, this site is located at the interface between two domains, and involves two residues from each of domains I and II. Comparisons of X-ray crystal structures of free and fatty-acid bound human serum albumin suggest that zinc binding to this site and fatty acid binding to one of the five major sites may be interdependent. Interactive binding of zinc and long-chain fatty acids to albumin may therefore have physiological implications.

Journal ArticleDOI
TL;DR: In this paper, the competitive adsorptive removal of cadmium (Cd(II)) and zinc (Zn(II) ions from binary systems using rice husk ash (RHA), a waste obtained from the Rice husk-fired furnaces, as an adsorbent was reported.

Journal ArticleDOI
TL;DR: In this article, the zinc oxide (ZnO) thin films obtained by the atomic layer deposition (ALD) method using diethyl zinc and water precursors, which allowed them to lower deposition temperature to below 200°C.
Abstract: We report on the zinc oxide (ZnO) thin films obtained by the atomic layer deposition (ALD) method using diethyl zinc and water precursors, which allowed us to lower deposition temperature to below 200 °C. The so-obtained “as grown” ZnO layers are polycrystalline and show excitonic photoluminescence (PL) at room temperature, even if the deposition temperature was lowered down to 100 °C. Defect-related PL bands are of low intensity and are absent for layers grown at 140−200 °C. This is evidence that extremely low temperature growth by ALD can result in high quality ZnO thin films with inefficient nonradiative decay channels and with thermodynamically blocked self-compensation processes.

Journal ArticleDOI
TL;DR: In this article, the effects of an embedded silver layer on the electrical and optical properties of zinc oxide (ZnO)/silver (Ag)/zinc oxide (znO) layered composite structures on polymer substrates have been investigated.
Abstract: The effects of an embedded silver layer on the electrical and optical properties of zinc oxide (ZnO)/silver (Ag)/zinc oxide (ZnO) layered composite structures on polymer substrates have been investigated. We have engineered transparent conducting oxide structures with greatly improved conductivity. Optical and electrical properties are correlated with Ag thickness. Film thicknesses were determined using Rutherford backscattering spectrometry. Hall effect, four-point probe, and UV-Vis spectrophotometer analyses were used to characterize electrical and optical properties. The results show that carrier concentration, mobility, and conductivity increase with Ag thickness. Increasing Ag thickness from 8to14nm enhances sheet resistance and resistivity by six orders of magnitude. The optical transmittance of the composite structure decreases when compared to a single ZnO layer of comparable thickness. However, a composite with 12nm of Ag provides conductivity and transmittance values that are acceptable for opto...

Journal ArticleDOI
TL;DR: The ability of low-cost activated carbon prepared from Ceiba pentandra hulls for the removal of lead and zinc from aqueous solutions has been investigated, including solution pH, contact time, adsorbent dose and initial metal ions concentration.

Journal ArticleDOI
TL;DR: In this article, the effects of heavy metals on soil microbial processes were investigated over a period of six weeks and the results showed the effect of metals on the measured parameters were significant (P<0.05).
Abstract: The effects of heavy metals on soil microbial processes were investigated over a period of six weeks. Analytical grade (Sigma) sulphate salts of copper, zinc and nickel were added individually and in combinations to soil samples and incubated in different plastic pots. Samples were taken from the pots forthnightly and the rates of microbial carbon and nitrogen mineralization, microbial biomass carbon and respiration were measured. The results showed the effect of metals on the measured parameters were significant (P<0.05.). By the 6th week postreatment, the rates of carbon accumulated were high in the copper (6.03 %) and copper:Zinc (5.80 %) treatments but low in the nickel and zinc (4.93 % and 5.02 % respectively). The rates of Nitrogen mineralization were 0.41 and 0.44 % in samples treated with copper and copper:zinc compared to 0.22 %–0.24 % obtained at the beginning of the experiments. Soil microbial biomass carbon declined from average value of 183.7–185.6 μg/g before treatment to as low as 100.8 and 124.6 μg/g in samples treated with copper:zinc and copper respectively.The rate of respiration of the soil microbial populations was equally inhibited by the metals. From an average rate of 2.51–2.56 μg of C/g respiration of the soil microbes declined to 0.98, 1.08 and 1.61 μg of C/g in the copper:zinc, copper and zinc treated soils by the end of the experiment. The results suggest additive or synergistic effects of the metals.

Journal ArticleDOI
TL;DR: In this paper, structural and optical properties of ZnO thin films were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and optical transmittance spectra.

Journal ArticleDOI
TL;DR: In this article, the formation of protective layers on copper, zinc and copper-zinc (Cu-10Zn and Cu-40Zn) alloys at open circuit potential in aerated, near neutral 0.5 M NaCl solution containing benzotriazole was studied using electrochemical impedance spectroscopy (EIS).

Journal ArticleDOI
TL;DR: In vitro solubility, as a percentage of total zinc in soaked rice, was significantly higher than in untreated brown rice while, in steeped brown rice, it was lower (p<0.05).

Journal ArticleDOI
TL;DR: In this paper, two carbon nanomaterials (CNMs) were synthesized using turpentine oil in a chemical vapour deposition (CVD) setup by varying the process parameters.

Journal ArticleDOI
TL;DR: In this article, the authors described the use of UV-light emitting diodes (LEDs) to enhance the room temperature gas sensitivity of zinc oxide sensors and found that the optimal sensitivity of the sensor was dependent on the applied light intensity.
Abstract: This study describes novel work on the use of UV-light emitting diodes (LEDs) to enhance the room temperature gas sensitivity of thick film zinc oxide sensors. Sensors based on nanoparticulates of zinc oxide activated with a UV-LED of peak wavelength 400 nm and incident light intensity 2.2 mW/cm2 were capable of detecting acetone and acetaldehyde at extremely low concentrations (1 vppb). The same sensors operated under identical conditions were also capable of detecting a range of other volatiles in the low ppm range, including hydrocarbons such as hexane, butane, propane and methane. The sensors were also sensitive to low ppm levels of volatiles when operated under high humidity conditions (100% relative humidity). We found that the optimal sensitivity of the sensor was dependent on the applied light intensity. The optimal light intensity giving maximum response was found to be analyte dependent, indicating that it is possible to tune the selectivity of the sensors by changing the applied light intensity. A GC–MS study found that the UV irradiated zinc oxide sensor was capable of catalysing the breakdown of a range of volatiles at room temperature. The general type of catalytic decomposition is in agreement with mechanistic studies carried out on heated metal oxide sensors.

Journal ArticleDOI
TL;DR: In this article, the pyrolysis and fire behavior of glass-fiber reinforced poly(butylene terephthalate) (PBT/GF) with two different metal phosphinates as flame retardants in combination with and without melamine cyanurate (MC) were analyzed by means of thermogravimetry, thermograimetry coupled with infrared spectroscopy, flammability, and cone calorimeter tests as well as scanning electron microscopy/energy dispersive X-ray spectrographs.
Abstract: The pyrolysis and fire behavior of glass-fiber reinforced poly(butylene terephthalate) (PBT/GF) with two different metal phosphinates as flame retardants in combination with and without melamine cyanurate (MC) were analyzed by means of thermogravimetry, thermogravimetry coupled with infrared spectroscopy, flammability, and cone calorimeter tests as well as scanning electron microscopy/energy dispersive X-ray spectroscopy and X-ray fluorescence spectroscopy. In PBT/GF, dosages of 13–20% of the halogen-free flame retardant aluminum phosphinate or aluminum phosphinate in combination with MC fulfill the requirements for electrical engineering and electronics applications (UL 94 = V-0; LOI > 42%), whereas the use of the same amount of zinc phosphinate or zinc phosphinate in combination with MC does not improve the fire behavior satisfactorily (UL 94 = HB; LOI = 27–28%). The performance under forced flaming conditions (cone calorimeter) is quite similar for both of the metal phosphinates. The use of aluminum and zinc salts results in similar flame inhibition predominantly due to the release of the phosphinate compounds in the gas phase. Both metal phosphinates and MC interact with the polymer changing the decomposition characteristics. However, part of the zinc phosphinate vaporizes as a complete molecule. Because of the different decomposition behavior of the metal salts, only the aluminum phosphinate results in a small amount of thermally stable carbonaceous char. In particular, the aluminum phosphinate-terephthalate formed is more stable than the zinc phosphinate-terephthalate. The small amount of char has a crucial effect on the thermal properties and mechanical stability of the residue and thus the flammability. Copyright © 2008 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, an alkali precipitation method was used to synthesize zinc oxide (ZnO) and aluminium doped ZnO nanoparticles with grain size in the nanometer range.

Journal ArticleDOI
TL;DR: In this paper, a visible light sensitive and highly active Cu-doped ZnS hollow photocatalyst particles "Cu-ZnS-shell" were successfully developed.
Abstract: Visible light sensitive and highly active Cu-doped ZnS hollow photocatalyst particles “Cu-ZnS-shell” were successfully developed. These particles could generate H2 through photocatalytic decomposition of HS− ion in Na2S solution. The photoactivity under xenon lamp irradiation was 6 and 130 times higher than that of copper-free “ZnS-shell” and coprecipitated ZnS particles, respectively. “Cu-ZnS-shell” particles were prepared by doping the “ZnS-shell” particles synthesized using zinc oxide as precursor with Cu, utilizing the difference in ionization tendency between zinc and copper. Though the photoactivity of “ZnS-shell” was higher than that of coprecipitated ZnS, their photoactivity under visible light conditions was low. However, the “Cu-ZnS-shell” was active to light of wavelengths higher than 440 nm and is preferred over CdS, which requires an expensive support metal catalyst such as platinum to decompose HS− ion.