La4Cu(3-x)Zn(x)MoO12: zinc-doped cuprates with Kagomé lattices

Two solid solutions, La4Cu(3-x)Zn(x)MoO12 (0.05 < or = x < or = 0.20, SS1) and La4Cu(3-x)Zn(x)MoO12 (0.30 < or = x < or = 2.40, SS2), were synthesized at ambient pressure and at temperatures from 1025 to 1200 degrees C by traditional solid-state reactions. Their structures were determined from X-ray powder diffraction with the help of electron and neutron diffraction. The atomic arrangements of SS1 and SS2 are similar, but their space groups are different, Pmnm for SS1 and P-1 for SS2, respectively. The copper, zinc, and molybdenum are coordinated by oxygen in corner-sharing trigonal bipyramids that are sandwiched between layers of lanthanum cations. In the transition metal cations layer of SS2, the copper and zinc cations order into a Kagomé-like lattice of triangular clusters. The magnetism has been measured from 2 to 300 K and is highly influenced by the geometric arrangement of the Cu(II) and Zn(II) cations. The number of free electrons per three Cu atoms is close to one for all samples in SS1 and SS2 indicating that the system can be well expressed by independent Cu(II)3 clusters. Spontaneous magnetization was observed in the system.     

Zinc isotope separation in acetone by displacement chromatography using benzo-15-crown-5 resin

Zinc isotope separation was studied by column chromatographies using resorcinol-formaldehyde-resin grafted with benzo-15-crown-5 in the porous silica beads. Chromatography was performed in a break-through manner by feeding the acetone solution of zinc chloride into the columns. Zinc isotopic abundance ratios of ⁶⁶Zn/⁶⁴Zn and ⁶⁸Zn/⁶⁴Zn were measured by ICP-MS. It has been found that the heavier isotopes are preferentially enriched at the front boundary region. This result proves ⁶⁴Zn depleted zinc can be obtained by collecting the effluents of front boundary region. The separation coefficient (ɛ) observed by five meters migration treatment is 0.81 · 10⁻³ for the isotopic pair of ⁶⁸Zn/⁶⁴Zn at 25 °C and higher separation coefficient was obtained from more concentrated zinc chloride solution.     

Anti-Microbial Hydroxyapatite Particles Synthesized by a Sol–Gel Route

Sol–gel route was applied to synthesize anti-microbial hydroxyapatite (HAp) powders by the addition of silver 200–20000 ppm or zinc salts. The bacteria strain, Streptococcus mutans (S. mutans, ATCC 25175) was used in the anti-bacterial tests. HAp phase was reproducibly obtained by the preparation conditions: Ca(NO₃)₂-4H₂O and trietheyl phosphate as sources of calcium and phosphorus sources, respectively, and ethanol as the solvent, aging for 16 h at 80°C, gelation and drying at 80°C for 24 h, then calcining at above 350°C. TGA was used to analyze thermal properties of the as-prepared gel. XRD and FTIR were used to identify the crystalline phase and chemical structure. CaO appeared as an impurity after calcining above 650°C. In the solid-state anti-microbial tests on the brain heart infusion (BHI) agar plates, there formed a microbial inhibition zone surrounding the Ag/Zn added (greater than 2000 ppm) samples. In the liquid-state anti-microbial tests, S. mutans cells readily precipitated with pure HAp powders but not with Ag/Zn added (greater than 2000 ppm) HAp powders. The concentration of silver or zinc ions releasing from the Ag/Zn added HAp powders into the supernatant of the BHI broth was under detection limit of ICP-AES analyses. However, the growth of S. mutans reached same magnitude (6 × 10⁸ CFU/mL) whether pure HAp, 2000 ppm-Ag or 2000 ppm-Zn were added. Therefore, Ag/Zn added HAp powders developed in this research present microbial inhibition properties and are of potential as a solid-state anti-microbial agent.     

Substoichiometric isotope dilution analysis of copper traces in zinc by adsorptive sampling

The spontaneous deposition of Cu²⁺ from aqueous solutions on a hydrogen-saturated platinum surface as a possibility for the substoichiometric sampling of copper is shown. A sensitive isotope dilution method has been developed for the determination of traces of copper in high purity zinc making use of the spontaneous deposition of microquantities of Cu²⁺ from aqueous solutions of zinc salts on a cathodically polarized platinum surface. If the same platinum surface is used in each run, the saturation values of the deposited copper are practically independent of the concentrations and contents of copper and zinc in the solution. The copper traces were labelled with the product of the⁶⁴Zn(n,p)⁶⁴Cu nuclear reaction. A copper content of 0.18±0.03 ppm in zinc was determined by this method.     

Influence of Fe concentration on the properties of the electrodeposited Zn–Fe coatings

Electrodeposition of Zn–Fe alloys on a copper substrate from a sulfate bath with different Fe²⁺ concentration (0.05, 0.10 and 0.20 mol L^?1) at room temperature was investigated using cyclic voltammetry. The influence of the Fe²⁺ content in the plating bath on the surface morphology, structural and magnetic properties of the coatings were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Vibrating Sample Magnetometer (VSM). The results show that the morphology of Zn–Fe films changes with different Fe²⁺ concentration. The EDS analysis demonstrated that the Fe content of the coatings increased with increasing the Fe concentration in the bath. XRD measurements shows the presence of ?Zn (hcp), δ1ZnFe (hcp) and the ΓZnFe (bcc) phases with a (101) preferential orientation in all the electrodeposited films. The magnetic analysis of Zn–Fe films indicated that the saturation magnetization was largely enhanced in comparison to pure Zn, especially with 0.2 at. % Fe, while the coercivity decreased.     

Zinc uptake in swine intestinal brush border membrane vesicles using a <Superscript>65</Superscript>Zn/<Superscript>69m</Superscript>Zn duel isotope experiment

Supplemental zinc as ZnO is routinely added to nursery pig diets at 15 to 20 times the nutritional requirement to alleviate physiological stress and enhance performance. The mechanism by which Zn accomplishes this function is unknown, however, high concentrations of Zn are excreted in the environment at undesirable levels. To study Zn uptake, we developed a multi-stage digestion model followed by exposure to swine intestinal brush border membrane vesicles (BBMV). We report on the feasibility of using a duel label (⁶⁵Zn and ^69mZn) to simultaneously quantify the competitive uptake of Zn from co-existing zinc supplements using our BBMV model.     

Iodine status and the effect of soil erosion on trace elements in Nanka and Oba towns of Anambra State, Nigeria

Iodine Deficiency Disorders (IDD) is common in all populations. Iodine and other trace elements naturally occur in the soil but erosion leaches off these elements from the soil. This results in a continued loss of trace elements from the soil. In the present study, the levels of iodine, selenium, zinc and lead in the environment (measured in soil, bitter leaves (Vernonia amygdalina), cassava roots (mannihot utilissima, staple food in Nigeria), and drinking water) and urinary iodine from school children (n=200), pregnant women (n=60) and women of child bearing age (n=60) were determined for Nanka prone to soil erosion and Oba all in Anambra State, Nigeria (used as control) to assess their risk to IDD. The levels of selenium, zinc and lead were analysed using Atomic Absorption Spectrophotometry while the levels of iodine in the environment and urinary iodine were estimated using the method of Dunn et al.,(1993). In this study there was a positive correlation between iodine and the metals. The results show that the mean concentrations of total soil zinc (0.69 +/- 0.16 ppm); lead (0.40 +/- 0.12 ppm) values in Oba were significantly (p < 0.05) higher than values from Nanka (Zn = 0.33 +/- 0.10 ppm; Pb = 0.21 +/- 0.09 ppm). However, total soil values for selenium and iodine in soil were not significantly different in the two communities. Mean concentration of total vegetable zinc (0.63 +/- 0.14 ppm) value in Oba is significantly (p < 0.05) higher than the value from Nanka (Zn = 0.31 +/- 0.07 ppm). However, total vegetable values for I, Se and Pb were not significantly different in the two communities. Also, mean concentration of total cassava zinc (0.65 = 0.15 ppm) in Oba was significantly (p < 0.05) higher than Zn (0.44 +/- 0.1l ppm) from Nanka. However, values for Se, Pb, and I were not significantly different in the two communities. Mean concentration of total water iodine (105.25 +/- 10.44 microg/L) in Oba was significantly (p < 0.05) higher than the value from Nanka (I = 89.8 +/- 6.42 microg/L). However, total water values for Se, Zn, and Pb were not significantly different in the two communities. The mean urinary iodine concentration of 170.65 +/- 27.17 microg/L in school children from Oba was significantly higher (p < 0.05) than the mean concentration of 156.12 +/- 16.48 microg/L found in school children from Nanka. However, the mean urinary iodine concentration of all the women (pregnant and non-pregnant) were not significantly different in the two communities but they are below the recommended daily intake. The results show that people living in Nanka and Oba, could be at risk of IDD.     

An Unprecedented Interpenetrating Structure Built from Two Differently Bonded Frameworks: Synthesis,Characteristics, and Efficient Removal of Anionic Dyes from Aqueous Solutions

The first example of one single crystal (NTOU-5) containing two different organic-inorganic hybrid open-framework structures was obtained using a hydro(solvo)thermal method and structurally characterized by single-crystal X-ray diffraction. Remarkably, under the same synthetic conditions, the zinc ions are respectively coordinated by oxalic acid (OX) and 1,2,4,5-tetrakis(imidazol-1-ylmethyl)benzene (TIMB) linkers to form two significantly different frameworks: anionic [Zn₂(OX)₃]²⁻ and cationic [Zn(TIMB)]²⁺ networks that interweave with each other to give an unprecedented interpenetrating structure with two differently-bonded open-frameworks. From the inorganic chemistry perspective, it is extremely difficult to control to which metal center the oxygen-donor linkers or/and nitrogen-donor ligands bind. A mixed Co/Zn analogue was also obtained by a similar method. The single-crystal XRD and EDS analyses indicate that the octahedral Zn ions of the anionic framework are replaced by cobalt cations, whereas the Zn ions in the tetrahedral positions of the cationic networks remain intact. This leads to the formation of the interpenetrating analogue with a mixed metal composition. Furthermore, NTOU-5 shows structural stability and efficiently removes organic dyes from aqueous solutions at concentrations of 10 ppm.     

Synthesis and Characterization of Functionalized Nanosilica for Zinc Ion Mitigation; Experimental and Computational Investigations

Zinc is an essential trace metal and its concentration above 4ppm reduces the aesthetic value of water. This study explores the possibility of using functionalized nanohybrids as Zn(II) ion scavengers from aqueous solution. Functionalized nanohybrids were synthesized by the attachment of thiosemicarbazide to silica. The material was characterized by TGA, SEM, FTIR, EDX, and BET analysis, which revealed ligand bonding to silica. The functionalized silica was employed as Zn(II) ion extractant in batch experiments and removed about 94.5% of the Zn(II) ions at pH 7, near zero point charge (6.5) in 30 min. Kinetics investigations revealed that zinc adsorption follows an intra particle diffusion mechanism and first-order kinetics (K = 0.1020 min⁻¹). The data were fitted to Freundlich, Dubinin–Radushkevich, and Langmuir models and useful ion exchange parameters were determined. The impact of co-existing ions on Zn(II) ion sequestration was also studied and it was found that the adsorbent can be used for selective removal of zinc with various ions in the matrix. Quantum mechanical investigations revealed that the Zn(II) ion adsorption on ZnBS1 is more favorable, having higher binding energy (BE) (−178.1 kcal/mol) and ∆H (−169.8), and making tridentate complex with the N and S sites of the chelating ligand. The negative ∆G and BE values suggest highly spontaneous Zn(II) adsorption on the modified silica even at low temperatures.     

Zinc-67 NMR study of zinc ions in water and in some nonaqueous and mixed solvents

Solutions of zinc salts in water, methanol (MeOH), dimethylformamide (DMF) and binary mixtures of water with the two nonaqueous solvents were studied by zinc-67 NMR measurements. Anhydrous zinc nitrate solutions in DMF and MeOH show upfield, concentration independent, chemical shifts at –27 and –19 ppm, respectively, vs. the aqueous solution standard. Addition of DMF or MeOH to an aqueous solution of a zinc salt results in a diamagnetic shift but for the addition of acetonitrile a paramagnetic shift results. In all cases the signal was broadened very considerably, e.g., in ZnCl₂ solution the linewidth increased from 40 to 600 Hz in going from water to 35% aqueous MeOH. Both⁶⁷Zn and¹³C NMR failed to show any complexation of Zn²⁺ ion by crown ethers in aqueous solution. A gradual addition of EDTA, of diaza-18-crown-6 or of tetraazacyclotetradecane resulted in an immediate broadening of the⁶⁷Zn signal which became undetectable when one equivalent of a ligand was added.     

Measurement of total Zn and Zn isotope ratios by quadrupole ICP-MS for evaluation of Zn uptake in gills of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss)

This study evaluates the potential use of stable zinc isotopes in toxicity studies measuring zinc uptake by the gills of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss). The use of stable isotopes in such studies has several advantages over the use of radioisotopes, including cost, ease of handling, elimination of permit requirements, and waste disposal. A pilot study using brown trout was performed to evaluate sample preparation methods and the ability of a quadrupole inductively coupled plasma mass spectrometer (ICP-MS) system to successfully measure changes in the ⁶⁷Zn/⁶⁶Zn ratios for planned exposure levels and duration. After completion of the pilot study, a full-scale zinc exposure study using rainbow trout was performed. The results of these studies indicate that there are several factors that affect the precision of the measured ⁶⁷Zn/⁶⁶Zn ratios in the sample digests, including variations in sample size, endogenous zinc levels, and zinc uptake rates by individual fish. However, since these factors were incorporated in the calculation of the total zinc accumulated by the gills during the exposures, the data obtained were adequate for their intended use in calculating zinc binding and evaluating the influences of differences in water quality parameters.     

Zn(II)‐Selective Membrane Electrode Based on Tetraazamacrocycle [Bzo2Me2Ph2(16)hexaeneN4]

A PVC membrane electrode using [Bzo₂Me₂Ph₂(16)hexaeneN₄] ( I ) as ionophore, oleic acid as lipophilic additive and o‐nitrophenyloctyl ether as plasticizer has been investigated as Zn(II)‐selective electrode. The membrane incorporating 34.9% (w/w) PVC, 2.3% I , 4.7% OA and 58.1% o‐NPOE gave linear response over the concentration range 2.82×10^?6?1.0×10^?1 M with a Nernstian slope of 28.5±0.2 mV/decade of concentration with a detection limit of 2.24×10^?6 M (0.146 ppm) and showed a response time of less than 10 s and could be used in pH range 2.5–8.5. High selectivity was obtained over a wide variety of metal ions. The proposed electrode was successfully used as an indicator electrode in potentiometric titration of zinc ions with EDTA and for determination of zinc in real samples.     

Chromatographic Zinc Isotope Separation by Chelating Exchange Resin

Zinc isotope separations were studied by displacement chromatography using the chelating properties of malate, citrate and lactate exchange resin and EDTA as ligands. After each chromatographic operation, the heavier zinc isotopes were found to preferentially fractionated into the carboxylate complex solution phase. The separation coefficients (ε) for zinc isotope separation had the largest value and were obtained for the isotopic pairs ⁶⁸Zn/⁶⁴Zn (7.16 × 10^?4) and ⁶⁶Zn/⁶⁴Zn (3.08 × 10^?4), respectively, at 298 ± 1 K. The separation coefficient per unit mass differences (ε/ΔM) for the isotopic pair of ⁶⁸Zn/⁶⁴Zn was found to range around 1.55 × 10^?4.     

Determination of copper in zinc by proton activation analysis

A method for the determination of copper in zinc by proton activation analysis using the⁶³Cu(p, n)⁶³Zn reaction has been developed.⁶³Zn has to be separated chemically from gallium and copper activities formed out of the zinc matrix and from indium activity formed out of cadnium impurity. Gallium radionuclides are retained on a cation exchanger in chloride medium and the residual activity is extracted in di-isopropyl ether. Copper and indium are subsequently extracted with cupferron in chloroform. The method was applied to BCR reference materials with a copper concentration at the μg.g^?1 level. The detection limit amounts to 0.5 μg.g^?1.     

Isotope ratio determinations by inductively coupled plasma/mass spectrometry for zinc bioavailability studies

A method is described for the measurement of ⁶⁷Zn/^6*Zn and ⁷⁰ZN/⁶⁸Zn ratios by inductively coupled plasma/mass spectrometry with ultrasonic nebulization. The method provides sufficient accuracy and precision for zinc bioavailability studies that use samples of human feces or blood plasma. Extraction of zinc from ashed samples yields aqueous solutions sufficiently devoid of matrix ions that could affect count rates and isotope ratios. Effects of sodium matrix, zinc concentration, and instrumental parameters on the precision of isotope ratio determinations are documented. Additions of spikes enriched in ⁶⁷Zn and ⁷⁰Zn to natural-abundance fecal samples verify that ratios can be determined on solutions 30 μM in zinc (<300 nmol of zinc per sample) with relative accuracies of <1% and relative standard deviations (r.s.d.) of ?1% over the range from natural abundance to 370 atom% excess of ⁷⁰Zn and to 84 atom% excess of ⁶⁷Zn.     

Zinc(II) complexes of 4-aminoantipyrine (AAP). Crystal structure of [Zn(AAP)<Subscript>2</Subscript>Cl<Subscript>2</Subscript>]

Zinc(II) complexes of 4-aminoantipyrine (AAP), [Zn(AAP)₂X₂] (X = Cl^–, I^–) and [Zn(AAP)(CN)₂] · 2H₂O were prepared and characterized by elemental analysis, IR and NMR (¹H & ¹³C) spectroscopy. The crystal structure of [Zn(AAP)₂Cl₂] (1) was determined by X-ray crystallography. The structural analysis of 1 shows that the complex exists as a monomeric nonionic molecule with zinc atom bound to two AAP ligands and two chloride ions adopting a distorted tetrahedral geometry. In [Zn(AAP)₂(CN)₂] · 2H₂O, the appearance of a band at 2162 cm^–1 in IR and resonances around 142 ppm in the ¹³C NMR spectra indicated the binding of cyanide to zinc(II).     

Phosphatation of iron powder metallurgical samples for corrosion protection

Recently, powder metallurgy methods have been used widely for industrial purposes. In this work, powder-metallurgically produced samples were selected for zinc phosphate coating. Zinc phosphate coating was performed at 50 and 70 °C for 20 min in a bath containing 10 g l^?1 ZnO, 25.5 g l^?1 H₃PO₄, 5.88 g l^?1 HNO₃, and 2 g l^?1 NaNO₃. The effect of temperature on the phosphating process has been studied. The structure and corrosion resistance of coats have been investigated using scanning electron microscopy (SEM) and electrochemical methods (polarization and EIS). Results show that an increase in temperature affects the crystalline structure of the coats. The formation of the zinc phosphate coat on the powder metallurgical samples significantly decreases the corrosion rate of the samples.     

Electrodeposition of zinc + cobalt alloys.: Relation between the electrochemical response and the composition and morphology of the deposits

The electrodeposition of cobalt and zinc + cobalt alloy in aqueous chloride solution has been studied on vitreous carbon electrodes under different concentration conditions (total concentration of metallic ion 0.1 mol dm ⁻³, chloride ion 1 mol dm ⁻³, pH = 3), particularly during the initial stages of the deposition process. For the alloy a relation has been found between the shape of the current-time transients, the morphology of the deposits, the stripping analysis and the results of X-ray microanalysis. The different alloy phases present in the deposits were identified using X-ray microanalysis data, stripping voltammetry results and literature data.The results indicate that the electrocrystallization of cobalt is inhibited even at very low concentrations of zinc in solution: voltammetric and galvanostatic results indicate that the deposition potentials always correspond to more negative values than those for cobalt deposition. This inhibition depends strongly on both the metallic ion ratio in solution and the applied overpotential (or current density). For Zn(II)/Co(II) ratios greater than 1/9, low overpotentials (or low current densities) favoured homogeneous and compact deposits that were rich in zinc and were mainly composed of γ-phases of zinc + cobalt alloy. However, when high overpotentials or current densities were used and/or when the Zn(II)/Co(II) ratio was very low (< 1/9), dendritic and non-homogeneous cobalt-rich deposits were obtained.     

Radionuclides and heavy metal concentrations as complementary tools for studying the impact of industrialization on the environment

The aim of the study was to determine whether using chemical and radiochemical analysis of lake sediments can highlight changes in the climate. Also it was studied whether human impact on the environment can be observed and to what extent such changes are in agreement with historical data. Samples of 16 cm thick sediment cores from the Smreczynski Staw Lake were collected and divided into 1 cm thick sub-samples. The samples were air dried and homogenized. The quantitative analysis of Fe, Mn, Zn, Cr, Cu, Ni, Cd, and Pb in the digested sediment samples was made by using atomic absorption spectrometry. Simultaneously, the radioactivity of ¹³⁷Cs using gamma spectrometry and ²¹⁰Pb_uns using alpha spectrometry, were measured for sediment layer dating. Results showed that iron concentration was in the range 0.3–over 1 % (w/w), and zinc 0.01–0.05 % (w/w). Lesser concentrations were found for copper 18.37–43.6 ppm, manganese 37.5–50.7 ppm, lead 146.1–432 ppm, chromium 12.3–37.4 ppm, nickel 3.1–10.8 ppm and cadmium 0.9–34.6 ppm. Changes in ¹³⁷Cs radioactivity was in the range of 89 ± 11 to 865 ± 62 (Bq kg^?1). Sediments composition can accurately reflect (in terms of time and to what extent) air pollution and natural geo-chemical processes in the environment. However, the choice of the analysed object is crucial in this respect. The Smreczynski Staw Lake, due to its location in the mountains and hydrological situation, proved to be very useful for providing undisturbed analytical samples.     

Role of Ligand in the Selective Production of Hydrogen from Formic Acid Catalysed by the Mononuclear Cationic Zinc Complexes [(L)Zn(H)]+ (L=tpy,phen, and bpy)

A series of zinc-based catalysts was evaluated for their efficiency in decomposing formic acid into molecular hydrogen and carbon dioxide in the gas phase using quadrupole ion trap mass spectrometry experiments. The effectiveness of the catalysts in the series [(L)Zn(H)]⁺, where L=2,2′:6′,2′′-terpyridine (tpy), 1,10-phenanthroline (phen) or 2,2′-bipyrydine (bpy), was found to depend on the ligand used, which turned out to be fundamental in tuning the catalytic properties of the zinc complex. Specifically, [(tpy)Zn(H)]⁺ displayed the fastest reaction with formic acid proceeding by dehydrogenation to produce the zinc formate complex [(tpy)Zn(O₂CH)]⁺ and H₂. The catalysts [(L)Zn(H)]⁺ are reformed by decarboxylating the zinc formate complexes [(L)Zn(O₂CH)]⁺ by collision-induced dissociation, which is the only reaction channel for each of the ligands used. The decarboxylation reaction was found to be reversible, since the zinc hydride complexes [(L)Zn(H)]⁺ react with carbon dioxide yielding the zinc formate complex. This reaction was again substantially faster for L=tpy than L=phen or bpy. The energetics and mechanisms of these processes were modelled using several levels of density functional theory (DFT) calculations. Experimental results are fully supported by the computational predictions.