Zinc Salt Concentration Research Articles

Formation of ZnO@Cd(OH) 2 core-shell nanoparticles by sol–gel method: An approach to modify surface chemistry for stable and enhanced green emission

We report the formation of highly stable and luminescent ZnO@Cd(OH) 2 core-shell nanoparticles by simple introduction of cadmium salt in the initial precursor solution, used to synthesize ZnO nanoparticles by sol–gel route. The cadmium to zinc salt concentration ratio has been also varied to control the growth of ZnO nanoparticles at the smaller particle size. Formation of ZnO@Cd(OH) 2 core-shell nanostructure has been confirmed by X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX) and X-ray photoelectron spectroscopy (XPS). UV–vis absorption spectroscopy exhibits blue-shift in absorption edge on increasing cadmium concentrations. The photoluminescence emission spectra showed the remarkably stable and enhanced visible (green) emission from suspended ZnO@Cd(OH) 2 nanoparticles in comparison to bare ZnO nanoparticles. It is postulated that Cd(OH) 2 layer at the surface of ZnO nanoparticles prevents the agglomeration of nanoparticles and efficiently assists the trapping of hole at the surface site, a first step necessary for visible emission. The Fourier transform infrared spectroscopy (FTIR) also supports our assumption about surface chemistry.

Effect of zinc salts on the structure–function of actomyosin from pelagic fish

The effect of zinc salts, zinc chloride and zinc sulfate on the structure and ATPase enzyme activity of actomyosin from pelagic fish ( Sardinella longiceps) has been investigated. ATPase enzyme activity decreased in the presence of both the zinc salts. The inhibitory effect is present in both pH of 7.0 and 9.0. At concentration of 1 × 10 −3 M of zinc salts, complete inhibition of ATPase enzyme activity is observed. With the increase in temperature from 25 °C to 45 °C the ATPase activity decreased by nearly 80%. The solubility profile of actomyosin in the presence of zinc salts shows a sigmoid pattern as the concentration of both the zinc salts increases. Free SH content of actomyosin decreased with the increase in concentration of zinc salts. Intrinsic fluorescence indicated significant decrease in relative fluorescence intensity of actomyosin. This indicates significant alterations in the structure of actomyosin. Analysis of secondary structure also indicates significant alteration in the α-helical content upon binding of both zinc salts.

Evaluation of Metals in a Defined Medium for Pichia pastoris Expressing Recombinant β-Galactosidase

Culture growth and recombinant protein yield of the Pichia pastoris GS115 methanol utilization positive system were studied in response to the types and levels of metals present in the growth medium and the supplemental salts typically used for these fermentations. Magnesium and zinc were both required to support cell growth but at significantly reduced levels compared to the control. However, supplementation with calcium, cobalt, iron, manganese, iodine, boron, and molybdenum were not required to sustain cell mass. When the medium was reformulated with only zinc and magnesium, the cells grew to 12-15 generations, which are expected for high cell density fed-batch fermentations. Product yields of the recombinant protein beta-galactosidase were significantly influenced by the trace metal concentrations. By using response surface and full factorial designs, maximum protein yield occurred when the concentration of zinc salt was limited to the level necessary only to support cell mass while protein yield positively correlated to increasing levels of the remaining trace metal salts. These studies are the first to show that excess trace metals must be optimized when developing P. pastoris based fed-batch fermentations.

Spherical Zinc Oxide Nano Particles from Zinc Acetate in the Precipitation Method

AbstractThe liquid precipitation method using zinc acetate dihydrate was applied for the synthesis of uniform and spherical ZnO nanoparticles. The ultrafine zinc oxid was prepared in a water‐ethanol mixture solution. The solution containing zinc cation was soluble in water. The surface‐active agent triethanolamine (TEA) was soluble in ethanol. Then alkali precipitated by adding n‐propylamine. The spherical zinc oxide particle morphology was found to be highly dependent on the zinc salt concentration, ethanol‐water ratio, and the surface‐active agent additive. The process can produce white ZnO powder of 50–90 nm in size. The morphology of zinc oxide showed a powder shape by transmission electron microscopy (TEM), the crystallization phase structure of zinc oxide by X‐ray diffraction (XRD), and the zinc oxide remaining by using an organic analysis by infrared spectroscopy (IR).

Controlled Growth of Well-Aligned ZnO Nanorod Array Using a Novel Solution Method

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.

Preparation and characterization of precipitated zinc silicates

The study aimed to obtain highly dispersed particles of zinc silicate, a potential filler of polymers or a paint pigment, by precipitation from solutions of sodium metasilicate and of zinc salts. The technique of silicate precipitation was worked out, and the conditions causing precipitation were optimized. The temperature, sodium metasilicate solution flow rate and concentration of zinc salts were selected so as to obtain silicates of the lowest possible bulk density, and which had low water-absorbing capacity and high paraffin oil-absorbing capacity. In the study, the effects of precipitation parameters were examined on the principal physicochemical properties of the silicates, the structure and uniform character of silicate particles, particle size distribution, and the surface morphology. Particular attention was devoted to the particle size distribution and the tendency to form primary agglomerates (aggregates) and secondary agglomerates, using dynamic light scattering (DLS). Studies were undertaken to develop a technique which could prevent formation of silicate particle agglomerates. With this aim, the silicates' surface was modified either during their precipitation or by the so-called dry technique. For the modification, silane coupling agents were applied. The extent of silicate surface hydrophobicity was examined by estimation of the enthalpies of immersion of the modified silicate surface. The silicates obtained were tested as fillers of rubber mixtures (in butadiene–styrene rubber). © 2003 Society of Chemical Industry

Adsorption of Silver onto Activated Carbon from Acidic Media: Nitrate and Sulfate Media

Adsorption of silver from acidic silver nitrate and sulfate media onto a peat-based activated carbon was studied. The effects of pH, temperature, and zinc nitrate and zinc sulfate addition on the adsorption kinetics and capacities were investigated. An XRD study showed that Ag(I) was reduced to Ag(0) on the carbon surface during the adsorption process. Low pH, high zinc salt concentration, and temperature are detrimental to the adsorption of silver. Second-order reactions were involved in the process of silver adsorption with respect to Ag(I). Hydroquinone-like surface oxygen functional groups were probably involved in the reduction reaction of Ag(I) → Ag(0). The addition of butanol to the solution appreciably reduced the adsorption rate and capacity of silver on the activated carbon. This indicates that graphene layer surfaces might also be involved in the Ag(I) → Ag(0) reaction because of the enrichment of π-electrons on the basal planes.

Ericoid mycorrhizal fungi from heavy metal polluted soils: their identification and growth in the presence of zinc ions

Ericoid mycorrhizal fungi can alleviate heavy metal toxicity to their host plant, but the mechanisms that lie behind this increased tolerance are unknown. As a first step in the characterisation of two isolates of Oidiodendron maius from mycorrhizal roots of Vaccinium myrtillus growing in heavily contaminated soils, we investigated their taxonomic position, their mycorrhizal capabilities and their ability to grow in the presence of heavy metals. When growth was compared with isolates from non-polluted soils, a better performance was observed in the presence of increasing concentrations of zinc salts, especially at higher ion concentrations. The mechanisms of tolerance may include the production of mucilage and extracellular pigments.

Effect of zinc salts on the spontaneous copolymerization of 4-vinylpyridine with various electron-rich vinyl monomers

The spontaneous copolymerization of 4-vinylpyridine (4-VP) complexed with three different zinc salts (chloride, acetate, and triflate) with various electron-rich vinyl monomers (p-methoxystyrene, MeOSt; p-methylstyrene, MeSt; α-methylstyrene, α-MeSt; p-tert-butylstyrene, BuSt; styrene, St) was investigated in methanol at 75°C. Increasing the zinc salt concentration or the nucleophilicity of the electron-rich monomer increased the copolymer yields. All obtained copolymers are characterized by high molecular weight (105) and broad molecular weight distribution. Both 1H-NMR and elemental analyses confirmed the almost 1 : 1 copolymer structure. Changing the anion of the zinc salt does not have a considerable effect either on the copolymerization rate or on the molecular weight. The proposed mechanism exhibits the formation of a σ-bond between the β-carbons of the two donor–acceptor monomers. This creates the 1,4-tetramethylene biradical intermediate which can initiate the copolymerization reaction. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2787–2792, 1997

Preferential induction of apoptosis in mouse CD4+CD8+αβTCRIoCD3εIo thymocytes by zinc

High concentrations of zinc salts (500 microM and greater) are known to inhibit apoptosis in a variety of systems. However, closer examination of dose effects revealed that lower concentrations of zinc (80-200 microM) could induce apoptosis in approximately 30-40% of mouse thymocytes following 8 h incubation. The ability of zinc to cause thymocyte apoptosis was detected flow-cytometrically by reduction in propidium iodide DNA fluorescence and forward scatter, both quantitative indicators of apoptotic death. Zinc induced both internucleosomal DNA fragmentation and morphological changes characteristic of apoptosis as determined by gel electrophoresis and electron microscopy, respectively. In addition, transcriptional and translational inhibitors prevented zinc-induced apoptosis, indicating a requirement for de novo mRNA and protein synthesis, another characteristic of apoptotic death. Fluorescent immunophenotype-specific apoptotic analysis indicated that zinc-induced apoptosis occurred primarily in the less mature CD4+CD8+ alpha beta TCRloCD3 epsilon lo thymocyte subset, with lower amounts of death occurring in the other subsets. This lineage specificity was shared with glucocorticoid-induced apoptosis. Taken together, these results indicate that zinc induces true apopotitic death in mouse thymocytes and suggests a role for zinc in the regulation of apoptosis.