Aqueous Solutions Of Zinc Salts Research Articles

Facile synthesis of highly uniform ZnO multipods as the supports of Au and Ag nanoparticles

Through the direct reaction of the aqueous solutions of zinc salts and KOH, highly uniform ZnO multipods consisted of rod-shaped branches are synthesized in an extremely high yield. The synthesis is conducted at low temperature, does not require any organic capping agents to affect the crystal habit, and is independent on the species of zinc sources. Moreover, by changing the reaction temperature from 25 to 70 °C, the tips of the multipods can be adjusted from taper to regular hexagon. The mechanism responsible for the formation of ZnO multipods is the self-regulation growth guided by the inherently asymmetric structure of hexagonal ZnO along the c-axis. After the surface modification with amino groups, ZnO multipods show good affinity to Ag and Au nanoparticles, which results in the spontaneous migration of Au and Ag nanoparticles to the surface of ZnO to form well-defined Au/ZnO and Ag/ZnO heterostructures. The fabricated hybrids are found to be effective surface-enhanced Raman scattering (SERS) substrates because of their distinct geometrical shape, large surface area, and the ability to create a strong local electromagnetic field by the metal–semiconductor heterojunction.

Influence of molecular adsorbates on the structure of electrodeposited nanocrystalline ZnO

Pure ZnO or ZnOEosinY with adsorbed EosinY molecules was deposited electrochemically from aqueous zinc salt solutions on (0001)GaN and (0001)ZnO. X-ray diffraction revealed the deposition of crystalline ZnO in all cases, with almost perfect orientation in the c -direction. Shifts in the peak positions observed for ZnOEosinY were explained by a lattice expansion by 3.6% in the c -direction caused by the strong influence of the EosinY molecules adsorbed during the growth of ZnO. Scanning electron microscopy (SEM) was used to elucidate the film morphology. Photoluminescence measurements served to determine changes in the electronic structure of these nanocrystalline materials. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Textile electrodes as substrates for the electrodeposition of porous ZnO

Metal-coated polyamide threads and filaments were chosen as substrate electrodes to deposit highly porous ZnO films for photovoltaic application. The films were electrodeposited at 70 degrees C from oxygen-saturated aqueous zinc salt solutions containing EosinY as a structure directing agent. The current density during deposition was increased compared with planar electrodes by enhanced diffusion at the filaments operating as cylindrical microelectrodes. Analysis by scanning electron microscopy showed an influence of geometrical constraints within the textiles and the hydrodynamic flow rate in the deposition solution on the film morphology. Photoelectrochemical characterization of sensitized films revealed the feasibility of the presented approach and indicated further steps needed for electrode optimization.

Photoelectrochemical characterisation and optimisation of electrodeposited ZnO thin films sensitised by porphyrins and phthalocyanines

Hybrid thin films of crystalline ZnO modified by 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrinato zinc (TSTPPZn) and 2,9,16,23-tetrasulfophthalocyaninatozinc(II) (TSPcZn) were prepared by electrochemical deposition from aqueous zinc salt solutions. A "one-step" process with the sensitisers adsorbed during ZnO deposition represented the most simple approach. ZnO was also grown independently in the presence of Eosin Y as a structure-directing agent, which was then removed and the sensitisers were chemisorbed from solutions ("readsorption" method). The photoelectrochemical characteristics of the electrodes were studied by photocurrent spectra and by time-resolved photocurrent measurements in an acetonitrile-based solution containing I3(-)/I(-) as the redox electrolyte. In films with both sensitisers present, both sensitisers worked in parallel providing panchromatic sensitisation. Recombination of electrons injected into the conduction band of ZnO with remaining holes in the HOMO of the sensitisers was indicated for the one-step films, but was considerably suppressed for the films prepared by the readsorption method. Films prepared by the readsorption method showed a significantly increased efficiency by an increased surface area and suppressed recombination.

Modification of ZnO Layers by Molecular Adsorbates During Electrochemical Deposition

ABSTRACTZnO and ZnO/EosinY hybrid materials were electrodeposited from aqueous zinc salt solutions on (0001) GaN and on (0001) ZnO. Crystalline ZnO was deposited as proven by X-ray diffraction (XRD). The intensity pattern for ZnO/EosinY showed a preferential orientation with the c- plane of ZnO parallel to GaN (0001) or ZnO (0001). XRD rocking curves with FWHM=0.25° indicated a high level of in-plane orientation of the deposited ZnO crystalline domains. The peak position of (0002) ZnO was shifted by 2Θ=1.3°. This difference and the corresponding simultaneous shift of (0004) ZnO were explained by a lattice expansion by 3.6 % in the c- direction. This clearly indicated the strong influence of the Eosin Y molecules adsorbed during the electrodeposition of ZnO. Scanning electron microscopy (SEM) revealed the formation of domains with different crystal sizes pointing at a varying density of nucleation sites on the substrate.

Mineralization from Aqueous Solutions of Zinc Salts Directed by Amino Acids and Peptides

The suitability of amino acids and dipeptides as structure-directing agents for the deposition of coatings from aqueous solutions of zinc salts is discussed. According to a bio-inspired approach, the influence of these biomolecules was investigated with respect to the evolution of architectures based on zinc oxide and basic zinc salts. The small molecules were able to trigger the morphology of these materials ranging from grainlike to two-dimensional up to three-dimensional features. Besides morphological aspects, the structural characterization of these solids by means of electron and atomic force microscopies, photoelectron and infrared spectroscopies, and X-ray diffraction are discussed in order to extract the function of the biomolecules with regard to the formation of the inorganic phases.

Hybrid thin films of ZnO with porphyrins and phthalocyanines prepared by one-step electrodeposition

Hybrid thin films of crystalline zinc oxide and the zinc complex of 5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrin (ZnTPPS) have been prepared by cathodic electrodeposition from different aqueous zinc salt solutions. Films from a solution containing zinc nitrate and the porphyrin derivate show a rough surface and porosity, whereas films prepared from an oxygen-saturated zinc chloride solution were very smooth. The presence of the porphyrin derivative in the deposition solution has a clear influence on the morphology of the hybrid films compared with pure zinc oxide films. In aqueous zinc nitrate solution the addition of the porphyrin derivative hinders the growth of zinc oxide. In contrast, the addition of the dye to the oxygen-saturated zinc chloride solution leads to an increase of the growth rate of ZnO /porphyrin hybrid films. An increased spectral absorbance was reached when two dyes (zinc complex of tetrasulfonated phthalocyanine and porphyrin) were added to the zinc nitrate solution since the electrodeposited hybrid thin films contained both dyes. UV-vis spectra revealed the presence of both macrocyclic metal complexes in the ZnO films.

Charakterystyka fizykochemicznych wlasciwosci nieorganicznych skladnikow mieszanin polimerowych o budowie jadro-powloka. Czesc II. Uklady zawierajace krzemionke pirogeniczna

Wet impregnation of pyrogenic silica (Aerosil 200 and Aerosil 300) with aqueous solutions of zinc salts [Zn(NO 3 ) 2 , Zn(CH 3 COO) 2 , Zn(NH 3 ) 4 (NO 3 ) 2 and zinc complexes with EDTA, ethylene diamine and diethyl triamine] was used to obtain a new type of dispersoids with core-shell (ZnO/SiO 2 systems) structure, containing 1-20% ZnO by weight. Physicochemical properties of ZnO/SiO 2 systems were determined using EDX, ICP, adsorptive static method and XRD. Wet impregnation allows to obtain ZnO/SiO 2 systems with the assumed ZnO content, regardless of the kind of zinc salt being supported (Table 4). Bulk and surface layer ZnO content is proportional to the amount of zinc salt being supported, and the surface layer is ZnO enriched (Table 3). XRD shows that ZnO supported on pyrogenic silica is amorphous. Increase in ZnO content decreases the ZnO/SiO 2 system specific surface (more visible in Aerosil 300), whereas their capillary structure remains unchanged (Table 6). Deposition of ZnO on pyrogenic silica improves its dispersion and ZnO/SiO 2 systems may be used as white fillers, crosslinking agents and activators of elastomer mixtures.

Zeolite ZnY catalysts prepared by solid-state ion exchange

Zeolites ZnY with various overall zinc contents were prepared from mixtures of zeolite NH4Y and crystalline zinc chloride by solid-state ion exchange. The obtained materials were investigated with carbon monoxide, xenon, and nitrogen adsorption as well as with 129Xe NMR and XRF spectroscopy. From the results of these measurements, the zinc cation distributions between the different types of cages of the faujasite framework as well as between the crystallographic positions SIII and SII within the large voids (supercages) were quantitatively determined. The concentrations of zinc cations in the supercages of the presently prepared zeolites are considerably higher than in materials obtained from NaY by conventional wet ion exchange using aqueous zinc salt solutions. Experimental evidence is provided for salt inclusion under certain conditions of preparation.

The Effect of Zinc-Containing Chewing Gum on Volatile Sulfur-Containing Compounds in the Oral Cavity

Wåler SM. The effect of zinc-containing chewing gum on volatile sulfur-containing compounds in the oral cavity.Volatile sulfur-containing compounds (VSC) are known to constitute the major component of halitosis. Aqueous solutions of zinc salts have been shown to reduce the levels of VSC produced orally. The aim of the present study was to examine whether zinc could be made available in the oral cavity and inhibit VSC production when delivered by a chewing gum. VSC measurements were carried out on the ‘morning breath’ of 11 test subjects and re-examined after the use of test solutions containing 0.02% zinc chloride, 0.2% chlorhexidine, or water or the use of chewing gums containing 2 mg, 0.5 mg, or 0 mg zinc acetate. The results showed that similar amounts of zinc in mouthrinses or chewing gum had the same effect, with a reduction of the oral VSC of 45%. Chewing gum thus seems to be a viable alternative for delivering zinc to reduce I'SC levels in the oral cavity.

Preparation of zinc oxide and zinc sulfide powders by controlled precipitation from aqueous solution

ZnO and ZnS powders were prepared from aqueous solutions of zinc salts in the presence of ethylenediamine or triethanolamine. The morphology of the powders was analysed by scanning electron microscopy and infrared spectroscopy. The effect of the experimental conditions upon the size and shape of the particles is described with a special emphasis on the role of the organic ligand.

Uniform colloidal zinc compounds of various morphologies

The preparation of finely dispersed zinc compounds consisting of uniform particles is described. Aging at elevated temperatures ({approx} 90{degree}C) of aqueous solutions of zinc nitrate or zinc chloride in the presence of urea resulted in precipitation of uniform rodlike basic zinc carbonate particles. These solids show x-ray characteristics of crystalline hydrozincite. In the presence of sulfate ions amorphous spherical particles of narrow size distribution of the same chemical composition are generated. On calcination both kinds of solids change to zinc oxide yet retain the original shape. In the presence of NaH{sub 2}PO{sub 4} and urea, aqueous zinc salt solutions on aging yield rather uniform amorphous spherical zinc basic phosphate particles, which on calcination lose water.

The Solubility Product Constant of ZnO

not Available.

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.