Effect of chloride ions' introduction on structural, thermal stability, and spectroscopic properties in Yb3+Er3+-codoped germanate-bismuth-lead glasses

Yb3+Er3+-codoped chloride-modified germanate-bismuth-lead glasses have been synthesized by the conventional melting and quenching method. Structural and thermal stability properties have been obtained on the basis of the Raman spectra and differential thermal analysis, which indicate that the PbCl2 addition has an important influence on the phonon density of states, maximum phonon energy, and thermal stability of host glasses. The Judd-Ofelt intensity parameters and quantum efficiencies were calculated on the basis of the Judd-Ofelt theory and lifetime measurements. For the 1.53 mu m emission band, the full widths at the half-maximum increase and peak wavelengths are blueshifted with increasing PbCl2 content. Moreover, the effect of the PbCl2 addition on the phonon density of states, OH- content, and upconversion luminescence has been discussed and evaluated. Our results reveal that, with increasing PbCl2 content, the decrease of phonon density and OH- content contributes more to the enhanced upconversion emissions than that of maximum phonon energy. (c) 2005 Optical Society of America

The electrochemical reduction reaction of dissolved oxygen on Q235 carbon steel in alkaline solution containing chloride ions

Cyclic voltammetry, electrochemical impedance spectroscopy, and rotating disk electrode voltammetry have been used to study the effect of chloride ions on the dissolved oxygen reduction reaction (ORR) on Q235 carbon steel electrode in a 0.02 M calcium hydroxide (Ca(OH)(2)) solutions imitating the liquid phase in concrete pores. The results indicate that the cathodic process on Q235 carbon steel electrode in oxygen-saturated 0.02 M Ca(OH)(2) with different concentrations of chloride ions contain three reactions except hydrogen evolution: dissolved oxygen reduction, the reduction of Fe(III) to Fe(II), and then the reduction of Fe(II) to Fe. The peak potential of ORR shifts to the positive direction as the chloride ion concentration increases. The oxygen molecule adsorption can be inhibited by the chloride ion adsorption, and the rate of ORR decreases as the concentration of chloride ions increases. The mechanism of ORR is changed from 2e(-) and 4e(-) reactions, occurring simultaneously, to quietly 4e(-) reaction with the increasing chloride ion concentration.

Investigation of AISI 1040 steel corrosion H(2)S solution containing chloride ions by digital image processing coupled with in electrochemical techniques

This paper presents a study of AISI 1040 steel corrosion in aqueous electrolyte of acetic acid buffer containing 3.1 and 31 x 10(-3) mol dm(-3) of Na(2)S in both the presence and absence of 3.5 wt.% NaCl. This investigation of steel corrosion was carried out using potential polarization, and open-circuit and in situ optical microscopy. The morphological analysis and classification of types of surface corrosion damage by digital image processing reveals grain boundary corrosion and shows a non-uniform sulfide film growth, which occurs preferentially over pearlitic grains through successive formation and dissolution of the film. (C) 2011 Elsevier Ltd. All rights reserved.

Effects of the magnesium and chloride ions and shikimate on the structure of shikimate kinase from Mycobacterium tuberculosis

Bacteria, fungi and plants can convert carbohydrate and phosphoenolpyruvate into chorismate, which is the precursor of various aromatic compounds. The seven enzymes of the shikimate pathway are responsible for this conversion. Shikimate kinase (SK) is the fifth enzyme in this pathway and converts shikimate to shikimate-3-phosphate. In this work, the conformational changes that occur on binding of shikimate, magnesium and chloride ions to SK from Mycobacterium tuberculosis (MtSK) are described. It was observed that both ions and shikimate influence the conformation of residues of the active site of MtSK. Magnesium influences the conformation of the shikimate hydroxyl groups and the position of the side chains of some of the residues of the active site. Chloride seems to influence the affinity of ADP and its position in the active site and the opening length of the LID domain. Shikimate binding causes a closing of the LID domain and also seems to influence the crystallographic packing of SK. The results shown here could be useful for understanding the catalytic mechanism of SK and the role of ions in the activity of this protein.

The effect of chloride ions and A. ferrooxidans on the oxidative dissolution of the chalcopyrite evaluated by electrochemical noise analysis (ENA)

It is believed that the dissolution of chalcopyrite (CuFeS2) in acid medium can be accelerated by the addition of Cl- ions, which modify the electrochemical reactions in the leaching system. Electrochemical noise analysis (ENA) was utilized to evaluate the effect of the Cl- ions and Acidithiobacillus ferrooxidans on the oxidative dissolution of a CPE-chalcopyrite (carbon paste electrode modified with chalcopyrite) in acid medium. The emphasis was on the analysis of the admittance plots (Ac) calculated by ENA. In general, a stable passive behavior was observed, mainly during the initial stages of CPE-chalcopyrite immersion, characterized by a low passive current and a low dispersion of the Ac plots, mainly after bacteria addition. This can be explained by the adhesion of bacterial cells on the CPE-chalcopyrite surface acting as a physical barrier. The greater dispersions in the Ac plots occurred immediately after the Cl- ions addition, in the absence of bacteria characterizing an active-state. In the presence of bacteria the addition of Clions only produced some effect after some time due to the barrier effect caused by bacteria adhesion. © (2009) Trans Tech Publications.

Gold coating of silica and zinc oxide nanoparticles by the surface reduction of gold(I) chloride

The possibility of a surface inner sphere electron transfer mechanism leading to the coating of gold via the surface reduction of gold(I) chloride on metal and semi-metal oxide nanoparticles was investigated. Silica and zinc oxide nanoparticles are known to have very different surface chemistry, potentially leading to a new class of gold coated nanoparticles. Monodisperse silica nanoparticles were synthesised by the well known Stöber protocol in conjunction with sonication. The nanoparticle size was regulated solely by varying the amount of ammonia solution added. The presence of surface hydroxyl groups was investigated by liquid proton NMR. The resultant nanoparticle size was directly measured by the use of TEM. The synthesised silica nanoparticles were dispersed in acetonitrile (MeCN) and added to a bis acetonitrile gold(I) co-ordination complex [Au(MeCN)2]+ in MeCN. The silica hydroxyl groups were deprotonated in the presence of MeCN generating a formal negative charge on the siloxy groups. This allowed the [Au(MeCN)2]+ complex to undergo ligand exchange with the silica nanoparticles, which formed a surface co-ordination complex with reduction to gold(0), that proceeded by a surface inner sphere electron transfer mechanism. The residual [Au(MeCN)2]+ complex was allowed to react with water, disproportionating into gold(0) and gold(III) respectively, with gold(0) being added to the reduced gold already bound on the silica surface. The so-formed metallic gold seed surface was found to be suitable for the conventional reduction of gold(III) to gold(0) by ascorbic acid. This process generated a thin and uniform gold coating on the silica nanoparticles. This process was modified to include uniformly gold coated composite zinc oxide nanoparticles (Au@ZnO NPs) using surface co-ordination chemistry. AuCl dissolved in acetonitrile (MeCN) supplied chloride ions which were adsorbed onto ZnO NPs. The co-ordinated gold(I) was reduced on the ZnO surface to gold(0) by the inner sphere electron transfer mechanism. Addition of water disproportionated the remaining gold(I) to gold(0) and gold(III). Gold(0) bonded to gold(0) on the NP surface with gold(III) was reduced to gold(0) by ascorbic acid (ASC), which completed the gold coating process. This gold coating process of Au@ZnO NPs was modified to incorporate iodide instead of chloride. ZnO NPs were synthesised by the use of sodium oxide, zinc iodide and potassium iodide in refluxing basic ethanol with iodide controlling the presence of chemisorbed oxygen. These ZnO NPs were treated by the addition of gold(I) chloride dissolved in acetonitrile leaving chloride anions co-ordinated on the ZnO NP surface. This allowed acetonitrile ligands in the added [Au(MeCN)2]+ complex to surface exchange with adsorbed chloride from the dissolved AuCl on the ZnO NP surface. Gold(I) was then reduced by the surface inner sphere electron transfer mechanism. The presence of the reduced gold on the ZnO NPs allowed adsorption of iodide to generate a uniform deposition of gold onto the ZnO NP surface without the use of additional reducing agents or heat.

Interaction of metal ions with 6-oxopurine nucleotides. Part 1. X-Ray structures of ternary cobalt(III) complexes with inosine 5'-monophosphate or guanosine 5'-monophosphate

The crystal structures of two ternary metal nucleotide complexes of cobalt, [Co(en)2(H2O)2]-[Co(5?-IMP)2(H2O)4]Cl2·4H2O (1) and [Co(en)2(H2O)2][Co(5?-GMP)2(H2O)4]Cl2·4H2O (2), have been analysed by X-ray diffraction (en = ethylenediamine, 5?-IMP = inosine 5?-monophosphate, and 5?-GMP = guanosine 5?-monophosphate). Both complexes crystallize in the orthorhombic space group C2221 with a= 8.725(1), b= 25.891(5), c= 21.212(5)Å, Z= 4 for (1) and a= 8.733(2), b= 26.169(4), c= 21.288(4)Å, Z= 4 for (2). The structure of (1) was solved by the heavy-atom method, while that of (2) was deduced from (1). The structures were refined to R values of 0.09 and 0.10 for 1 546 and 1 572 reflections for (1) and (2) respectively. The two structures are isomorphous. A novel feature is that the chelate ligand en and the nucleotide are not co-ordinated to the same metal ion. One of the metal ions lying on the two-fold a axis is octahedrally co-ordinated by two chelating en molecules and two water oxygens, while the other on the two-fold b axis is octahedrally co-ordinated by two N(7) atoms of symmetry-related nucleotides in a cis position and four water oxygens. The conformations of the nucleotides are C(2?)-endo, anti, and gauche�gauche. In both (1) and (2) the charge-neutralising chloride ions are disordered in the vacant space between the molecules. These structures bear similarities to the mode of nucleotide co-ordination to PtII complexes of 6-oxopurine nucleotides, which are the proposed models for intrastrand cross-linking in DNA by a metal complex.

Effect of inorganic ions, H(2)O(2) and pH on the photocatalytic inactivation of Escherichia coli with silver impregnated combustion synthesized TiO(2) catalyst

The photocatalytic antibacterial activity of Ag impregnated combustion synthesized TiO(2) (0.25 g/L) was studied against Escherichia coil in presence of UV irradiation. The effect of various parameters, such as anions, canons, hydrogen peroxide and pH, on the photocatalytic inactivation was investigated. The addition of inorganic ions showed a negative effect on inactivation. Among anions, the presence of chloride ions was observed to have a maximum negative effect and reduced the inactivation considerably. Among cations, the bacterial inactivation reduced significantly in the presence of Ca(2+) ions. Hydrogen peroxide addition in combination with Ag/TiO(2) photocatalysis, however, improved the inactivation. Photocatalysis with high concentration of H(2)O(2) yielded complete bacterial inactivation within few minutes. The photocatalytic inactivation of E. coil was not affected by variation in pH. (C) 2011 Elsevier B.V. All rights reserved.

Plant nutrients and major ions in the Little Sea, Studland, Dorset

This short paper records some measurements made on the Little Sea, a shallow, coastal, acidic lake on Studland Heath, Dorset. The lake, formed about 100 years ago by dunes cutting off a sea inlet, has not received any input of agricultural fertilizers or other waste products for at least the last 30 years. It is a Site of Special Scientific Interest (SSSI). Samples of surface water were taken from the northern and southern ends of the lake at 3-monthly intervals, from July 1995 to April 1996. The first samples in July 1995 were taken during a period of drought; rain, sometimes very heavy, came in late September. With the exception of silicate, potassium and phosphate, there were no large changes in plant nutrient concentrations during the year. The concentration of nitrate-nitrogen was very low (close to the limits of analytical detection), but total phosphorus at ca. 30 mu g per litre was similar to concentrations found in some of the Cumbrian eutrophic lakes. The large number of algal species at low cell/colony concentrations suggested that the lake is mesotrophic. Sodium, chloride and magnesium in the lake water were close to the same proportions as those found in sea water. Dry and wet deposition of sea-salts on the lake surface and its catchment area probably is the major source of sodium, magnesium and chloride ions in the lake, and also accounts for about half of the mean potassium and sulphate concentrations.

Concentrations of major ions in the stream water of the River Duddon, England, 1970-1974 [Dataset]

This dataset provides raw data of chemical analyses made during studies on seasonal variations of some major ions in the stream water of the River Duddon in Cumbria. Measurements of sodium, calcium, potassium, magnesium and chloride ions and pH were taken at 5 stations in the River Duddon between January 1970 and August 1974.

Concentrations of major ions in the stream water of the upper basin of the River Duddon, England, 1972-1974 [Dataset]

This dataset provides raw data of chemical analyses made during studies on seasonal variations of some major ions in the stream water of the upper basin of the River Duddon in Cumbria. Measurements of sodium, calcium, potassium, magnesium and chloride ions and pH were taken at 26 stations in the River Duddon basin between 1972 and 1974.

Major ions in 25 frequently sampled tarns in the English Lake District (1954-56, 1974-1976) [Dataset]

This dataset provides raw data of chemical analyses made during studies on seasonal variations of 25 frequently sampled tarns in Cumbria. Measurements of sodium, calcium, potassium, magnesium, pH, chloride ions, alkalinity, sulphite, strong acids and nitrate were taken between 1954 and 1956 and between 1974-1976.

Concentrations of major ions in 182 tarns in the English Lake District (1953-1978) [Dataset]

This dataset provides raw data of chemical analyses made during studies on seasonal variations of 182 tarns in the English Lake District, Cumbria. Measurements of sodium, calcium, potassium, magnesium, pH, chloride ions, alkalinity, sulphite, strong acids and nitrate were taken between 1953 and 1978.

The transfer of chloride ion across an anion exchange membrane

The transfer of chloride ions into a low resistance anion exchange membrane (AEM) was investigated by cyclic voltammetry (CV) and electrochemical impedance spectra. In all cases, concentration polarization of Cl- ions is exterior to the membrane. It controls the flux and produces the limiting currents: either steady state or transient (peak type) current. In CV experiments, when the size of the holes in the membrane was much smaller than the distance between membrane holes, the Cl- anion transfer showed steady state voltammetric behavior. Each hole in the membrane can be regarded as a microelectrode and the membrane was equivalent to a microelectrode array in this condition. When the hole in the membrane was large or the distance between membrane holes was small, the CV curve of the Cl- anion transfer across the membrane showed a peak shape, which was attributed to linear diffusion. In AC impedance measurement, the impedance spectrum of the membrane system was composed of two semicircles at low DC bias, corresponding to the bulk characteristics of the membrane and the kinetic process of ion transfer, respectively. The bulk membrane resistance increases with increasing DC bias and only one semicircle was observed at higher DC bias. The parameters related to kinetic and membrane properties were discussed.