Mixed Zn Research Articles

BaAuxZn13–x: Electron-Poor Cubic NaZn13-Type Intermetallic and Its Ordered Tetragonal Variant

Cubic NaZn(13)-type (Fm-3c, Z = 8) BaAu(x)Zn(13-x) compounds in the regions 1 ≤ x ≤ 5.4 (a = 12.418(1)-12.590(1) Å) and 6.4 ≤ x ≤ 8 (a = 12.630(1)-12.660(1) Å) plus an ordered tetragonal variant near x = 6 (P4/nbm; a = 8.8945(4) Å, c = 12.646(1) Å; Z = 4) have been synthesized and characterized by means of X-ray diffraction. Although the cubic structure contains Zn-centered, mixed (Zn, Au) icosahedra connected in alternate orientations via mixed tetrahedral stars (TS), the icosahedron vertices are ordered in the tetragonal structure. Both the inner and the outer tetrahedra in the TS in the cubic phase consist of mixed Au and Zn atoms, whereas the tetragonal phase features three different coloring schemes: inner Zn and outer Au tetrahedra, vice versa, or mixed Au and Zn sites on both inner and outer tetrahedra. Barium atoms center 24-atom snub cuboctahedra. Ordering of Au and Zn in the tetragonal phase achieves the largest number of heteroatomic Au-Zn contacts and yields relatively larger Hamilton populations (-ICOHPs) compared with homoatomic counterparts according to LMTO-based electronic structure calculations and analysis. Larger overlap populations are also observed for inter- versus intraicosahedral interactions. The densities-of-states data suggest the phase is metallic with highly dispersed Au d bands and nearly free-electron-like s and p bands for both Au and Zn.

Comparison of single and joint effects of Zn and Cu in continuous flow and batch reactors

BACKGROUND: Microbial behavior in batch reactors may be different from that in continuous flow reactors, which is expected to affect microbial response to heavy metal exposure. Four parallel continuous flow reactors and batch growth tests were used to investigate the single and joint toxicity of Zn and Cu to Artrobacter sp. JM018. RESULTS: The results indicated that Cu is more toxic than Zn under all conditions. In the batch reactors, all Zn concentrations showed a stimulatory effect on microbial growth. However in the continuous system, 125 µmol L−1 Zn exposure produced inhibition. In the case of mixed Zn and Cu exposures in the batch system, the presence of Zn reduced the severity of Cu inhibition, with a net impact of reduced growth in all cases, whereas in the continuous system microbial growth and substrate utilization rates sharply decreased and ceased. CONCLUSION: The results clearly showed that growth in batch reactors underestimated significantly the heavy metal inhibition, compared with the continuous system. Therefore, the results of batch reactor tests should not be used directly when heavy metal inhibition is to be interpreted for continuous flow systems. Copyright © 2011 Society of Chemical Industry

Mixed Zn and O substitution of Co and Mn in ZnO

The physical properties of an impurity atom in a semiconductor are primarily determined by the lattice site it occupies. In general, this occupancy can be correctly predicted based on chemical intuition, but not always. We report on one such exception in the dilute magnetic semiconductors Co- and Mn-doped ZnO, experimentally determining the lattice location of Co and Mn using ${\ensuremath{\beta}}^{\ensuremath{-}}$-emission channeling from the decay of radioactive ${}^{61}$Co and ${}^{56}$Mn implanted at the ISOLDE facility at CERN. Surprisingly, in addition to the majority substituting for Zn, we find up to 18% (27%) of the Co (Mn) atoms in O sites, which is virtually unaffected by thermal annealing up to 900${\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}$C. We discuss how this anion site configuration, which had never been considered before for any transition metal in any metal oxide material, may in fact have a low formation energy. This suggests a change in paradigm regarding transition-metal incorporation in ZnO and possibly other oxides and wide-gap semiconductors.

Synthesis, spectral and thermal studies of some transition metal mixed ligand complexes: Modeling of equilibrium composition and biological activity

Several mixed ligand Ni(II), Cu(II) and Zn(II) complexes of 2-amino-3-hydroxypyridine (AHP) and imidazoles viz., imidazole (him), benzimidazole (bim), histamine (hist) and l-histidine (his) have been synthesized and characterized by elemental and spectral (vibrational, electronic, 1H NMR and EPR) data as well as by magnetic moment values. On the basis of elemental analysis and molar conductance values, all the complexes can be formulated as [MAB]Cl except histidine complexes as MAB. Thermogravimetric studies reveal the presence of coordinated water molecules in most of the complexes. From the magnetic measurements and electronic spectral data, octahedral structure was proposed for Ni(II) and Cu(II)-AHP-his, tetrahedral for Cu(II)-AHP-him/bim/hist, but square planar for the Cu(II)-AHP complex. The g ∥/ A ∥ calculated supports tetrahedral environment around the Cu(II) in Cu(II)-AHP-him/bim/hist and distorted octahedral for Cu(II)-AHP-his complexes. The morphology of the reported metal complexes was investigated by scanning electron micrographs (SEM). The potentiometric study has been performed in aqueous solution at 37 °C and I = 0.15 mol dm −3 NaClO 4. MABH, MAB and MAB 2 species has been identified in the present systems. Proton dissociation constants of AHP and stability constants of metal complexes were determined using MINIQUAD-75. The most probable structure of the mixed ligand species is discussed based upon their stability constants. The in vitro biological activity of the complexes was tested against the Gram positive and Gram negative bacteria, fungus and yeast. The oxidative DNA cleavage studies of the complexes were performed using gel electrophoresis method. Cu(II) complexes have been found to promote DNA cleavage in presence of biological reductant such as ascorbate and oxidant like hydrogen peroxide.

Syntheses, Structures, and Structural Transformations of Mixed Na(I) and Zn(II) Metal–Organic Frameworks with 1,3,5-Benzenetricarboxylate Ligands

Three new compounds, [ZnNa(BTC)(H2O)2]·H2O (1), [Zn3Na2(BTC)2(HCOO)2(H2O)8] (2), and [Zn3Na(BTC)2(HCOO)(H2O)3]·2H2O (3) (H3BTC = 1,3,5-benzenetricarboxylate acid), were synthesized under hydrotherm...

Synthesis, structures, and luminescence properties of mixed ligand Cd(II) and Zn(II) coordination compounds mediated by 1,2-bis(4-pyridyl)ethane

Interaction of cadmium(II) or zinc(II) acetate with 1,2-bis(4-pyridyl)ethane (bpe) in the presence of dioxime(1,2-cyclohexanedionedioxime = NioxH 2 or diphenylglyoxime = dpgH 2) resulted in three complexes with the compositions [Cd 2(CH 3COO) 4(NioxH 2) 2(bpe)(H 2O) 2] ( 1), [Cd(CH 3COO) 2(bpe)(H 2O)] n ( 2) and [Zn(CH 3COO) 2(NioxH 2)(bpe)(H 2O)] n ( 3), which were characterized by single-crystal X-ray diffraction, elemental analysis, IR, and luminescence spectroscopy. Dioxime-containing binuclear molecule 1 and 1D linear polymer 3 possess moderate luminescence properties, while the dioxime-free 1D polymer 2 demonstrates strong blue luminescence.

Mixed valence Zn–Co-layered double hydroxides and their exfoliated nanosheets with electrode functionality

New phases of Zn–Co-layered double hydroxides (Zn–Co-LDHs) were synthesized for the first time via a co-precipitation reaction using hydrogen peroxide as an oxidant. According to powder X-ray diffraction and field emission-scanning electron microscopy, both nitrate- and sulfate-forms of the Zn–Co-LDHs crystallized with the brucite-type layer structure having interlayer nitrate and sulfate anions, respectively, and commonly showed plate-like morphology with a crystal size of several hundred nanometers. dc magnetic susceptibility measurements revealed that the Zn–Co-LDHs displayed ferromagnetic/antiferromagnetic transitions below 15 K and the magnetic moment calculated from the paramagnetic region (30–300 K) indicated the co-existence of weak field Co2+ and strong field Co3+ ions. The mixed oxidation state of Co2+/Co3+ was confirmed by the results of iodometry and X-ray absorption near-edge structure spectroscopy. The heat-treatment for the Zn–Co–LDHs at elevated temperatures produced mixed metal oxide nanocomposites composed of spinel ZnCo2O4 and wurzite ZnO phases. The colloidal suspension of exfoliated Zn–Co-LDH nanosheets could be synthesized by dispersion of the pristine LDH materials in formamide, which was confirmed by the Tyndall phenomenon, high resolution-transmission electron microscopy/selected area electron diffraction, and UV-vis spectroscopy. The Zn–Co-LDH film fabricated with the restacked nanosheets exhibited pseudocapacitive behavior with a large specific capacitance and a good capacitance retention. The present findings underscore that the newly synthesized mixed valence Zn–Co-LDH phases showed promising functionality as a supercapacitor electrode material and also showed interesting magnetic coupling behavior.

Cu doped ZnO nanoparticle sheets

Cu doped ZnO nanoparticle sheets were synthesized via a proposed solution route with mixed Zn(NO 3) 2 and Cu(NO 3) 2 precursors at a low temperature of 95 °C. Scanning electron microscopy, transmission electron microscopy, and X-ray energy dispersive spectrometry results demonstrate that the nanostructues synthesized by solutions with higher Cu(NO 3) 2 concentration are nanoparticle sheets comprised of uniform Cu doped ZnO nanoparticles with diameters around 20 nm. Room-temperature photoluminescence spectra of the nanoparticle sheets show tunable near band emissions centered at 390–405 nm and strong yellow emissions at 585–600 nm. Absorbance spectra show gradual redshift in the UV range with the increase of Cu concentrations in the ZnO nanomaterials. The study provides a simple and efficient route to prepare Cu doped ZnO nanomaterials at low temperature. The as-synthesized products with both violet and yellow emissions are promising for white light-emitting diode applications.

Effect of Mg2+ on the microstructure and corrosion resistance of the phosphate conversion coating on hot-dip galvanized sheet steel

► Mg 2+ in the phosphate solution reduces pores in the phosphate coating on HDG steel. ► The phosphate coating with fewer pores display a better corrosion resistance. ► Mg 2+ improves the corrosion resistance of phosphated HDG steel. ► Mg 2+ distributes uniformly in Zn phosphate and (Zn, Mg) phosphate hydrate coating. ► Mg 2+ accelerates the nucleation of (Zn, Mg) phosphate by enhanced impingements. The effect of Mg 2+ in the phosphate solution on the microstructural evolution and corrosion resistance of the coating on hot-dip galvanized steel has been explored. Surface morphology observations reveal that increasing the solution Mg 2+ concentration increases the population density and refines the grain size of the phosphate grains. In the presence of Mg 2+ , the phosphate coating is composed of mixed Zn phosphate hydrate and (Zn, Mg) phosphate hydrate. Furthermore, elevating Mg 2+ in the solution reduces the porosity of the phosphate coating. As a result, the corrosion resistance of the phosphate coating is improved.

Activation of C–H bonds mediated by MoMo moieties in heterobimetallic Zn/O/Moclusters

Heterobimetallic drive and cooperativity lead to a striking scenario for C-H bond activation and heteroaggregation involving Mo(III) dimers. Reaction of (RO)(3)Mo[triple bond]Mo(OR)(3) with molar excess of ZnMe(2) at-78 degrees C affords the novel mixed Zn, Mo oxo clusters [Mo(2)(MeZn)(6)(mu(2)-Me)(mu(3)-CH(2))(2)(OR)(7)] 1 (R = neopentyl) and 2 (R = cyclohexyl) preserving the Mo[triple bond]Mo triple bond, while the same reaction performed at ambient temperature gives rise to the related cluster [Mo(2)(MeZn)(6)(mu(2)-CH(2))(mu(3)-CH(2))(2)(OR)(6)] 3. These complexes represent the first examples of heterobimetallic Mo[triple bond]Mo complexes with bridging methyl and methylene groups and agostic C-H-->Mo interactions, as well as penta-coordinate carbon. The complexes 1-3 were characterized by elemental analyses, multinuclear NMR and single-crystal X-ray diffraction analysis.

Synthesis, characterization, DNA interaction and antimicrobial screening of isatin-based polypyridyl mixed ligand Cu(II) and Zn(II) complexes

Several mixed ligand Cu(II)/Zn(II) complexes using 3- phenylimino-1,3-dihydro-2H-indol-2-one (obtained by the condensation of isatin and aniline) as the primary ligand and 1,10-phenanthroline (phen)/2,2'-bipyridine (bpy) as an additional ligand were synthesized and characterized analytically and spectroscopically by elemental analyses, magnetic susceptibility and molar conductance measurements, as well as by UV-Vis, IR, NMR and FAB mass spectroscopy. The interaction of the complexes with calf thymus (CT) DNA was studied using absorption spectra, cyclic voltammetric, viscosity and gel electrophoresis measurements. They exhibit absorption hypochromicity, and the specific viscosity increased during the binding of the complexes to calf thymus DNA. The shifts in the oxidation reduction potential and changes in peak current on addition of DNA were shown by CV measurements. The Cu(II)/Zn(II) complexes were found to promote cleavage of pUC19 DNA from the super coiled form I to the open circular form II and linear form III. The complexes show enhanced antifungal and antibacterial activities compared with the free ligand.

Tritopic phenanthroline and pyridine tail-tied aza-scorpiands

The synthesis of two new tritopic double-scorpiand receptors in which two equivalent 5-(2-aminoethyl)-2,5,8-triaza[9]-(2,6)-pyridinophane moieties have been linked with 2,6-dimethylpyridine (L1) or 2,9-dimethylphenanthroline (L2) units is reported for the first time. Their acid-base behaviour and Zn(2+) coordination chemistry have been studied by pH-metric titrations, molecular dynamic calculations, NMR, UV-Vis and steady-state fluorescence techniques. L1 and L2 behave, respectively, as hexaprotic and heptaprotic bases in the experimental conditions used (298.1 +/- 0.1 K, 0.15 mol dm(-3) NaCl, pH range under study 2.0-11.0). These ligands are able to form mono-, bi- and trinuclear Zn(2+) complexes depending on the Zn(2+)-receptor molar ratio. Interaction of L1 and L2 with pyrophosphate (PPi), tripolyphosphate (TPP) and adenosine 5'-triphosphate (ATP) has been followed by pH-metric titrations, (1)H and (31)P NMR techniques and molecular dynamic analysis. Finally, formation of mixed complexes Zn(2+)-L-PPi, Zn(2+)-L-TPP and Zn(2+)-L-ATP has been studied for both receptors by potentiometric titrations.

Synthesis and characterization of ZnO, CuO and a mixed Zn and Cu oxide

ZnO, CuO, and Cu0.05Zn0.95O nanoparticles have been prepared by a sol–gel method using poly(vinyl alcohol) aqueous solutions and metal nitrate precursors. The precursor powders were analyzed by thermogravimetry (TG) and differential scanning calorimetry (DSC). X-ray powder diffractometry (XRD), infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used to characterize the structural and the chemical features of the nanoparticles. An average nanocrystallite size of 25–30 nm was obtained for ZnO and Cu0.05Zn0.95O and of 40 nm for CuO, as estimated by the Scherrer's equation.

Electrodeposition of polycrystalline ZnTe from simple and citrate-complexed acidic aqueous solutions

The cathodic electrodeposition of polycrystalline zinc telluride from aqueous acidic solutions of zinc sulphate and tellurite, under constant or pulsing voltage, is described. Various compositions of the bath were tested with respect to the Zn/Te precursor ratio, including addition of citrate buffer as a complexation agent. Metallic (Ni and Ti) and semiconductor (CdTe and CdSe) electrodes were used as cathode-substrates. The deposits were characterized by XRD, SEM-EDX and FTIR techniques. The formation of compact barrier layers of zinc blend, stoichiometric ZnTe or mixed (Zn,Cd)Te was attained. Pulse plating in a citrate-free bath and constant potential plating from a citrate bath were seen to have the most beneficial effect on the properties of the electrodeposits, as leading to improved microstructure of the ZnTe films, in terms of crystallinity and stoichiometry. Further, the employment of [1 1 1]-oriented CdTe or CdSe substrates featured an epitaxial growth of polycrystalline ZnTe films as well as an improved Zn/Te atomic ratio compared to the metallic substrates.

Experiment Study on Corrosion Control Using Coking Wastewater as Circulating Cooling Water

The coking wastewater drainage will bring severe water environmental pollution, so it is necessary to change the coking wastewater into resource. The reuse of pre-treated coking wastewater as make-up water for circulating cooling system is an important way. To prevent the circulating cooling system corrosion, the characteristic and the corrosion control technology and the effect of the classic corrosion inhibitors in the circulating cooling water system were studied by static experiment and dynamic experiment based on water quality stabilization theory. The results indicate that the corrosion in circulating cooling system is mainly spot corrosion caused by pollutants in coking wastewater, and the corrosion inhibition technology on the model of precipitated membrane based on phosphor series should be preferred. The mixed corrosion inhibitors HEDP and Zn 2+ optimally selected by experiment can form a firm corrosion inhibition membrane on heat transfer surface, and the corrosion inhibition rate could reach 85.6%. The corrosion rate of common carbon steel is 0.105 mm/a, which could satisfy the criterion of > Design criterion of the industrial circulating cooling water treatment > (GB 50050-95). The practical application to the circulating cooling system shows that the mixed corrosion inhibitors HEDP and Zn 2+ can control the corrosion in the system economically when the concentration multiple is 2–2.2, which opens up a feasible way for changing the coking wastewater into resource.

Zinc cysteine active sites of metalloproteins: A density functional theory and x-ray absorption fine structure study

Density functional theory (DFT) and x-ray absorption fine structure (XAFS) spectroscopy are complementary tools for the biophysical study of active sites in metalloproteins. DFT is used to compute XAFS multiple scattering Debye Waller factors, which are then employed in genetic algorithm-based fitting process to obtain a global fit to the XAFS in the space of fitting parameters. Zn-Cys sites, which serve important functions as transcriptional switches in Zn finger proteins and matrix metalloproteinases, previously have proven intractable by this method; here these limitations are removed. In this work we evaluate optimal DFT nonlocal functionals and basis sets for determining optimal geometries and vibrational densities of states of mixed ligation Zn(His)(4-n)(Cys)(n) sites. Theoretical results are compared to experimental XAFS measurements and Raman spectra from the literature and tabulated for use.

Synthesis, properties and crystal structure of a Zn,Nb compound with homo- and heterodinuclear oxalate-bridged units – [{Zn(bpy) 2} 2(μ-C 2O 4)][Zn(bpy) 2(μ-C 2O 4)NbO(C 2O 4) 2] 2·0.5bpy·7H 2O: The impact of weak interactions on the crystal packing

A heterometallic Zn,Nb compound of the formula [{Zn(bpy) 2} 2(μ-C 2O 4)][Zn(bpy) 2(μ-C 2O 4)NbO(C 2O 4) 2] 2·0.5bpy·7H 2O ( 1) (bpy = 2,2′-bipyridine) has been synthesized by the reaction of the tris(oxalato)oxoniobate(V) anion, [NbO(C 2O 4) 3] 3− and [Zn(bpy) 3] 2+ in an aqueous solution, and characterized by IR and UV/vis spectroscopy, elemental and thermogravimetric analyses and X-ray single crystal diffraction method. The compound crystallizes in the triclinic P 1 ¯ space group with a = 15.9060(9), b = 16.0804(9), c = 21.5892(12) Å, α = 69.504(4), β = 82.598(5), γ = 86.012(5)°, V = 5127.5(5) Å 3, and Z = 2. The molecular structure consists of three dinuclear oxalate-bridged units, one homodinuclear Zn IIZn II and two heterodinuclear Zn IINb V units, seven water molecules and half of a bipyridine molecule. Zinc atoms are in all units octahedrally surrounded by four nitrogen atoms from the bipyridine ligands and by two oxygen atoms from the bridging oxalate groups. Niobium atoms in the two mixed Zn IINb V units adopt a pentagonal bipyramidal coordination formed by six oxygen atoms from the oxalate groups and one oxo-oxygen atom. Weak interactions, primarily hydrogen bondings and π–π stacking interactions, influence greatly the supramolecular motifs recognized in the crystal packing. Thermal decomposition of the title compound resulted in the formation of the mixed-metal Zn 3Nb 2O 8 oxide phase.

Synthesis, characterization and fluorescence spectra of mixed ligand Zn(II), Cd(II) and Hg(II) complexes with 1,10-phenanthroline-5,6-dione ligand

The novel mixed ligand complexes [M(bpy)(phen-dione)](PF6)2 (M = Zn(II), Cd(II) and Hg(II), bpy = 2,2′-bipyridine and phen-dione = 1,10-phenanthroline-5,6-dione) have been synthesized and characterized by elemental analysis, IR, 1H NMR and electronic absorption spectroscopies. The ν(C=O) of coordinated phen-dione in these complexes are very similar to the free phen-dione ligand showing that phen-dione is not coordinated to metal ion from its C=O sites. Absorption spectra of the complexes show two absorption bands for intraligand transitions. These absorption bands show dependence to the dielectric constant of solvent. These complexes exhibit an intensive fluorescence band around 535 nm in DMF when the excitation wavelength is 260 nm at room temperature. The fluorescence intensity of these complexes is larger than that of the free ligand.

Zn-Assisted Synthesis and Photoluminescence Properties of MgO Nanotubes

A newly developed one-step Zn-assisted route has been used to produce MgO nanotubes (MNTs) by simple thermal evaporation of the mixed Zn and Mg powders without catalysts. The MNTs have average outer diameters of 80 nm and wall thicknesses of about 15 nm. The growth mechanism of MNTs is discussed in detail. The Zn/ZnO nanocables formed at the initial growth stage are crucial, act as interim templates for the formation of MNTs, and disappear automatically after formation of MNTs. Room-temperature photoluminescence measurement reveals structural-defect-related visible emissions of the synthesized MNTs. This kind of MNT with a high surface area may have promising applications as the sorbent for chemisorption and destructive adsorption of various pollutants and as a protective template by filling the MNTs with low-melting-point metals or semiconductor nanoparticles, due to their excellent refractory and thermal properties.

Preparation of Zn(1−x)CdxFe2O4 (x = 0.0,0.1, 0.3, 0.5, 0.7 and 1.0) ferrite samples and their characterization by Mössbauer andpositron annihilation techniques

Single phase Zn(1−x)CdxFe2O4 (x = 0.0,0.1, 0.3, 0.5, 0.7 and 1.0) ferrite samples have been prepared by the solid statereaction method. The room temperature Mössbauer spectra for all the samplesindicate the paramagnetic nature of the prepared samples. Mössbauer spectrahave been deconvoluted separately for the tetrahedral ‘A’ site and the octahedral‘B’ site to identify the variations of the Mössbauer parameters, i.e. isomer shift,quadrupole splitting and linewidth, with the concentration of Cd doping,x,for the tetrahedral ‘A’ site and octahedral ‘B’ site. Changes of these parameters with concentration,x, confirmthat the Cd2+ ions prefer to go to the tetrahedral ‘A’ site compared to the octahedral ‘B’ site in thisZn(1−x)CdxFe2O4 cubic spinel ferrite system. To study the changes in the electron momentumdistributions, coincidence Doppler broadening of the electron positron annihilationγ-radiation measurement technique has been employed. The results indicate that positrons areannihilating less with the oxygen 2p electrons and other core electrons in the case of mixed(Zn(1−x)CdxFe2O4) ferritesthan ZnFe2O4 or CdFe2O4 ferrites.