Concentration Of Transition Metal Ions Research Articles

English

Mineral waters from Bardejovske Kupele spa are natural, strongly mineralized, with healing effects. They are classified as hydrocarbonic - containing chloride and sodium - carbonic, cold, hypotonic, with a relatively high boric acid content. Potential anti-oxidative effects of curative waters from Bardejovske Kupele were investigated against the hyaluronan (HA) degradation. High-molar-mass HA was exposed to the action of ascorbate and cupric ions, which initiate free-radical chain degradation. Time-dependent changes of dynamic viscosity ( η) of the HA solutions were monitored by rotational viscometry. The radical scavenging capacity of curative waters was determined by the ABTS assay. Despite a significantly high content of transition metal ions, especially iron, remarkable protective effects of the two curative spa waters were found, namely and Even though Alzbetas iron content was 3.5-fold higher than Klaras, Alzbeta was shown to have better protective properties against the HA degradation compared to Klara. Bolus addition of ferric ions to the reaction system instead of the natural iron-containing curative water caused a significant HA degradation. The ABTS decolorization assay revealed that the curative spa waters were proven as poorly effective scavengers of the ABTS •+ cation radical.

Effect of coupling agents on the degradation of polypropylene/fly ash composites

ABSTRACTComposites containing 50% wt fly ash (sourced from the UK and South Africa) in polypropylene homopolymer (manufacturer stabilized for general purpose use) have been prepared by using batch and continuous methods. The effect of the following coupling agents were investigated on the photo‐ and thermal‐decomposition of the composite materials: Lubrizol Solplus C800 (an unsaturated carboxylic acid), γ‐methacryloxypropyl trimethoxy silane (γ‐MPS), 1,3‐phenylene dimaleimide (BMI), and maleic anhydride‐grafted‐polypropylene (m‐PP). High melt, thermal‐, and photo‐stability was favored when the matrix was coupled to the filler surface by monomeric coupling agents that were expected to adsorb in a close packed layer on the fly ash surface. Further improvements were observed in cases where the coupling agent could also self‐polymerize. m‐PP did not lead to increased stability due to its low adsorption density on the fly ash surface. The relatively high water/acid soluble transition metal ion content of the UK sourced fly ash did not appear to affect stability under the test conditions employed in this study. The South African sourced fly ash had a higher level of quartz and mullite together with a high level of group 1 and 2 metals. The latter in particular may have led to debonding of the coupled interfacial region from the filler surface and possible adsorption of stabilizers on the pristine surface. This resulted in the South African fly ash generally possessing poorer resistance to oxidation than the UK fly ash. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39974.

Application of INAA for investigation of magnesium and aluminium oxide materials

The paper presents investigations of changes in optical absorption and photo luminescence spectra of magnesium oxide, and natural and synthetic magnesium aluminium spinel related with the content of transition metal ions (Cr, Fe, Mn) and the irradiation with fast neutrons. Six synthetic single magnesium aluminium spinel crystals with different stoichiometry (MgO·nAl2O3), five natural crystals from Ural and Pamir deposits, and seven MgO crystals were studied. Micro impurities (Cr, Fe, and Mn) and macro component (Mg, Al) quantities have been determined using the instrumental neutron activation analysis technique. Concentrations of impurities in different spinels were found in following ranges: for Cr—1 × 10−4 to 8 × 10−2 %, for Mn—2 × 10−5 to 23 %, for Fe—1 × 10−4 to 1.2 %. Three ranges of luminescence: 380–460, 650–850 and 850–1,050 nm, were established in the most part of the investigated MgO samples. Analysis shows that the intensity of emission in each of these regions is strongly dependent on the concentration of transition metal ions. Great deviation from the stoichiometry of the irradiated MgO·2.8Al2O3 crystal leads to the local structure of α-Al2O3 formation around Cr3+ ions. The orange emission is attributed to Mn2+ in octahedral coordination, it can be assumed that the band at 570 nm is belonging to the complex centre “Mn2+–F+ (or F centre)”.

The major function of a metallothionein from the aquatic fungus Heliscus lugdunensis is cadmium detoxification

A spring from a former copper shale mine in the area of Mansfelder Land, Germany, shows extremely high transition metal ion concentrations, i.e. 40mM ZnII, 208μM CuII, 61μM AsV, and 25μM CdII. This makes it a challenging habitat for living organisms as they have to cope with metal ion concentrations that by far exceed the values usually observed in spring water. One of the surviving species found is the aquatic fungus Heliscus lugdunensis (teleomorph: Nectria lugdunensis). Investigation of its redox related heavy metal tolerance revealed the presence of small thiol containing compounds as well as a small metallothionein, Neclu_MT1 (MT1_NECLU: P84865). While CdII-induction of metallothioneins is observed in many species, the fact that exclusively CdII, but not ZnII, CuI, AsIII or oxidative stress can induce Neclu_MT1 protein synthesis is unparalleled. To complement the physiological studies performed in the fungus H. lugdunensis, the CdII and ZnII binding characteristics of the recombinantly expressed protein were spectroscopically analysed in vitro aiming to demonstrate the observed CdII specificity also on the protein level. Stoichiometric analyses of the recombinant protein in combination with photospectrometric metal ion titrations and 113Cd-NMR experiments reveal that metal ion binding capacities and consequently the structures formed at physiological Neclu_MT1 concentrations differ from each other. Concluding, we describe the first solely CdII-inducible metallothionein, Neclu_MT1, from H. lugdunensis, featuring a difference in the structure of the CdIIversus the ZnII metalated protein in a physiologically relevant concentration range.

Studies on the Performance of Ethylamine-Modified Chitosan Carbonized Rice Husk Composite Beads for Adsorption of Metal Ion

ABSTRACT Heavy metals in the soil and ground water have endangered our environment and human bodies by direct or indirect pathways. Currently, bioremediation is a developing process that offers the possibility to destroy various contaminants using natural biological activity. Biopolymers are industrially attractive because of their capability of lowering transition metal ion concentrations to parts per billion, they are widely available, and they are environmentally safe. This paper deals with the preparation of an ethylamine-modified biopolymer (chitosan) and carbon from biowaste (rice husk) composite beads (EAM-CCRCB) for metal ion removal. The prepared adsorbent was used for the adsorption of hexavalent chromium ions from aqueous solutions. The activation and surface properties of the adsorbent were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analyses. The effect of process variables such as initial metal ion concentration, adsorbent dosage, and pH of the solution on the performance of percentage removal and adsorption capacity were studied. Various isotherm and kinetic models were fitted with experimental data to describe the solute interaction and nature of adsorption with the adsorbent through batch studies. Mass thermodynamic parameters were determined. Regeneration studies were attempted to check the stability and activity of the adsorbent.

Preparation and characterization of transition metal based organo-inorganic hybrid optical materials for bioassay fluorescence sensor probe

High refractive index (H.R.I.) tetravalent transition metal ion coordinated with organic co-dopant to form charge transfer complexes into the optical acrylic preform. They have been fabricated with different concentrations of transition metal ions and H.R.I. organic co-dopant and characterized. The improved photo physical properties, thermal, structure, optical, and morphology of transition metal ions into the optical acrylic preform hybrid matrix were analyzed. Transition metal ions are dispersed inside the preform matrix with nanoparticles of mesophase structural organization through charge transfer complex formation. It gives a crucial role of nano-interface properties on fluorescence bright imaging and less life time. This hybrid functional optical hybrid material has high potential use in bio-assay sensor probe.

Factors Influencing Benzene Formation from the Decarboxylation of Benzoate in Liquid Model Systems

Benzene may occur in foods due to the oxidative decarboxylation of benzoate in the presence of hydroxyl radicals. This study investigated factors influencing benzene formation in liquid model systems. The type of buffer, other sources of hydroxyl radical formation in food (photo oxidation of riboflavin and lipid oxidation), transition metal ion concentrations, and the inhibitory effect of antioxidants were tested in benzoate containing model systems. Regarding the hydroxyl radical sources tested, the highest benzene formation was observed in light exposed model systems containing ascorbic acid, Cu(2+), and riboflavin in Na-citrate buffer (1250 ± 131 μg kg(-1)). In practice, it seems that the combination ascorbic acid/transition metal ion remains the biggest contributor to benzene formation in food. However, the concentration of Cu(2+) influences significantly benzene formation in such a system with highest benzene yields observed for Cu(2+) 50 μM (1400 μg kg(-1)). The presence of antioxidants with metal chelation or reduction properties could prevent completely benzene formation.

Structure and properties of Li2Zn2(MoO4)3 crystals activated with copper and chromium ions

Based on the corrected phase diagrams proper growth conditions for Li2Zn2(MoO4)3 crystals are selected. Large crystals (up to 100 mm), both impurity-free and activated by transition metal ions (Cu, Cr), are grown by the low-gradient Czochralski method. By the EPR method the charge state and structural position of copper and chromium ions are determined. The performed studies of luminescent properties show that for impurity-free crystals luminescence with λ = 388 nm with a two-exponential luminescence decay with τ1 = 2 ns and τ2 = 6 ns is observed at room temperature. At 77 K for both impurity-free crystals and those activated with transition metal ions luminescence with λ = 560 nm and the luminescence lifetime τ = 100 ns is observed, the intensity of luminescence with λ = 560 nm depending on the nature and concentration of transition metal ions. Cation vacancies responsible for the charge compensation of impurity transition metal ions are assumed to be also responsible for low-temperature luminescence.

ChemInform Abstract: Organometallic Acetylides of PtII, AuI and HgII as New Generation Optical Power Limiting Materials

AbstractReview: 106 refs.

Organometallic acetylides of PtII, AuI and HgII as new generation optical power limiting materials

Within the scope of nonlinear optics, optical power limiting (OPL) materials are commonly regarded as an important class of compounds which can protect the delicate optical sensors or human eyes from sudden exposure to damaging intense laser beams. Recent efforts have been devoted to developing organometallic acetylide complexes, dendrimers and polymers as high performance OPL materials of the next generation which can favorably optimize the optical limiting/transparency trade-off issue. These metallated materials offer a new avenue towards a new family of highly transparent homo- and heterometallic optical limiters with good solution processability which outperform those of current state-of-the-art visible-light-absorbing competitors such as fullerenes, metalloporphyrins and metallophthalocyanines. This critical review aims to provide a detailed account on the recent advances of these novel OPL chromophores. Their OPL activity was shown to depend strongly on the electronic characters of the aryleneethynylene ligand and transition metal moieties as well as the conjugation chain length of the compounds. Strategies including copolymerization with other transition metals, change of structural geometry, use of a dendritic platform and variation of the type and content of transition metal ions would strongly govern their photophysical behavior and improve the resulting OPL responses. Special emphasis is placed on the structure-OPL response relationships of these organometallic acetylide materials. The research endeavors for realizing practical OPL devices based on these materials have also been presented. This article concludes with perspectives on the current status of the field, as well as opportunities that lie just beyond its frontier (106 references).

On the Structure, Function and Metalloregulatory Properties of the Zinc-Activated Repressor Streptococcus Pneumoniae AdcR

A response to a change in transition metal ion concentration is mediated by metal-sensing transcriptional regulators that harbor metal-specific coordination sites. Zinc homeostasis in the gram positive human pathogen Streptococcus pneumoniae (Spn) is maintained by two novel zinc-regulated repressors, SczA and AdcR. Spn AdcR is the first putative metal-dependent member of the MarR family of transcriptional repressors. Expression profiling on BHI media under microaerobic conditions with a wild-type and isogenic ΔadcR strain reveals that AdcR regulates the expression of genes encoding the high affinity zinc uptake system adcRCBA, a group of zinc-binding pneumococcal histidine triad proteins (PhtA, PhtB, PhtD and PhtE) and an orphan AdcA homologue (AdcAII).

Fluorescence Enhancement of Levosulpiride Upon Coordination with Transition Metal Ions and Spectrophotometric Determination of Complex Formation

Absorbance and fluorescence spectral pattern of levosulpiride in absence and presence of first row transition metal ions (Mn-Zn) has been studied at room temperature under physiological condition. The fluorescence spectra of the drug in presence of different concentrations of transition metal ions showed enhancement in fluorescence intensity of levosulpiride. The photophysical changes owing to the direct interaction between metal ion and the amide nitrogen of levosulpiride has been described in terms of CHEF (chelating enhancement fluorescence) effect. The absorption spectra of the drug at different pH exhibited two isosbestic points at 255 and 275 nm respectively, indicating the presence of three chemical species in solution. The ratio of the drug to metal ions is found to be 2:1 and the log K of the resulting complex was determined spectrophotometrically and potentiometrically. The apparent ionization constant of levosulpiride is found to be 8.98. The low value of stability constant suggests that complexes may dissolve and the drug can be absorbed.

Room Temperature Ferromagnetism in Spin-coated Anatase- and Rutile- Ti1-x Mx O2 ( M= Fe, Mn, Co) Films

AbstractDiluted magnetic semiconductors (DMS) have been explored extensively, because of their potential application in spintronic devices. We studied the structural optical and magnetic properties of Ti1-xMxO2 (M= Fe, Mn, Co; x = 0.00, 0.05, 0.08, 0.10, 0.15, 0.20, 0.25, 0.30), thin films by sol-gel process and deposited using spin coating on Pt (Pt/Ti/SiO2/Si) and quartz substrates. X-ray diffraction studies and Raman spectroscopy reveal anatase and rutile phases of the synthesized films when annealed at 500 and 10000 C, respectively. Optical transmission measurements show high degree of transparency that decreases with increase in transition metal ion concentration. The films show room temperature ferromagnetism, suggesting their potential in spin based heterojunction devices.

Surface Modification of Nanoclays by Catalytically Active Transition Metal Ions

A unique class of nanoclays was prepared by modification of pristine clays or organoclays (Cloisite C20A) with transition metal ions (TMIs). The composition, structure, morphology and thermal properties of TMI-modified nanoclays were investigated by atomic absorption spectroscopy (AAS), elemental analysis (EA), scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray absorption near-edge structure (XANES) spectroscopy. The content of TMIs in modified clays was found to be close to the limiting value of ion exchange capacity. SEM and X-ray results confirmed that TMIs were located between the mineral layers instead of being adsorbed on the surface of clay particles. TGA results indicated that the TMI treatment of organoclays could significantly increase the thermal stability, which was more pronounced in air than in nitrogen. Temperature-resolved SAXS measurements revealed that the presence of TMIs increased the onset temperature of structural degradation. The higher thermal stability of TMI-modified organoclays can be attributed to the change in the thermal degradation mechanism, resulting in a decrease in the yield of volatile products and the formation of char facilitated by the presence of catalytically active TMIs.

DNA Strand Breaks by Metal‐Induced Oxygen Radicals in Purified Salmonella typhimurium DNA

Purified Salmonella typhimurium DNA was incubated for 1h at 37 degrees C with various concentrations (10-100 muM) of transition metal ions (Fe(2+), Fe(3+), Cu(2+), Ni(2+), Cd(2+)), with various concentrations (0.1-100 mM) of H(2)O(2), and with various concentrations of each transition metal ion in the presence of various concentrations of H(2)O(2). Damage to DNA was assessed by electrophoresis of the reaction mixtures in 1% agarose gel. Breakage of the DNA strands would produce a series of DNA fragments resulting in a smear in the gel, while intact DNA produced a single band. Results showed that no damage to the DNA was detectable after incubation with either H(2)O(2) alone or either of the metal ions alone. However, all of the metal ions investigated triggered DNA breakage in the presence of H(2)O(2). The extent of breakage depended on the metal ion and on its concentration, as well as on the H(2)O(2) concentration. Addition of either EDTA or catalase to the reaction mixture completely inhibited the DNA degradation, confirming the involvement of both the metal ion and the H(2)O(2) in the breakage of DNA strands. Production of the hydroxyl radical when H(2)O(2) and a metal ion were both present in the reaction mixture was evidenced by the thiobarbituric acid method. The most extensive damage was caused by Cu(2+) followed, in decreasing order, by Fe(2+), Fe(3+), Ni(2+), and Cd(2+).

Structural and electrical properties of tellurovanadate glasses containing Li 2O

Glassy materials are promising intercalation compounds, due to their open network structure and absence of grain boundaries. Some glasses containing alkali ions and a high concentration of transition metal ions can present mixed ionic-electronic conductivity and are therefore potential candidates for application as cathode material in Li-ion batteries. The present work is devoted to the ternary system xLi 2O–(1 − x)[0.3V 2O 5–0.7TeO 2] with 0 ≤ x ≤ 0.4. These compounds were prepared by heat treatment in air at 800 °C followed by traditional quenching. Raman spectroscopy and 51V nuclear magnetic resonance measurements were performed in order to highlight the structural short range order modifications induced by the introduction of the Li 2O network modifier. These structural effects can be related to the electrical behaviour, as studied by complex impedance spectroscopy measurements.

Spectral analysis of Mn 2+, Co 2+ and Ni 2+: B 2O 3–ZnO–PbO glasses

This paper reports on the spectral properties of Mn 2+, Co 2+ and Ni 2+ ions doped B 2O 3–ZnO–PbO glasses. XRD, FT-IR spectra and DSC profiles of these glasses have also been carried out, and the FT-IR profiles have shown the presence of both BO 3 and BO 4 units. It is interesting to notice that the FT-IR peak positions are slightly shifted towards higher energy with an increase in transition metal ion concentration change. From the measured DSC thermograms, glass transition ( T g), crystallization ( T c) and temperature of melting ( T m) have been evaluated. From the UV absorption spectra of Mn 2+, Co 2+ and Ni 2+ ions doped glasses, both direct and indirect optical band gaps have been calculated. The visible absorption spectra of Mn 2+:glasses have shown a broad absorption band at 520 nm ( 6A 1g(S) → 4T 1g(G)); with Co 2+ ions one absorption band at 605 nm ( 4A 2( 4F) → 4T 1( 4P)) and another at 1450 nm ( 4A 2( 4F) → 4T 1( 4F)); and for Ni 2+:glasses three absorption bands at 420 nm ( 3A 2g(F) → 3T 1g(P)), 805 nm ( 3A 2g(F) → 1E g(D)) and 880 nm ( 3A 2g(F)→ 3T 1g(F)) have been observed. For Mn 2+:glasses, upon excitation with 262 nm, a green emission (539 nm) with a slight blue shift; and with 392 nm, a green emission (534 nm) with a slight red shift with Mn 2+ ions concentration change (0.2–0.5 mol%) has been observed. This green emission has been assigned to ( 4T 1(G) → 6A 1(S)) d–d transition of Mn 2+ ions that are in tetrahedral co-ordination. For 0.5 mol% Co 2+ ions doped glass, upon excitation with 580 nm, a red emission (625 nm) has been observed which originates from 2E( 2G) → 4A 2( 4F) transition of Co 2+ ions in tetrahedral co-ordination. For Ni 2+ ions doped glasses upon excitation with 420 nm, a green (577 nm) and red (670 nm) emissions are observed and are assigned to ( 1T 2g(D) → 3A 2g(F)) and ( 1T 2g(D) → 3T 2g(F)) d–d transitions of Ni 2+ ions in octahedral co-ordination.

In vitro and in vivo identification of ‘pseudocatalase’ activity in Dead Sea water using Fourier transform Raman spectroscopy

AbstractBalneotherapy with Dead Sea water has been reported as a successful treatment modality for psoriasis, atopic eczema and vitiligo, but the precise mode of action has escaped definition so far. The saturating salt concentration (346 g/litre) together with the unique UV spectrum have been suggested to trigger the release of pro‐inflammatory and chemotactic mediators. The results of our study show for the first time a high content of transition metal ions (manganese, iron and copper) in Dead Sea water. Using in vitro Fourier transform (FT) Raman spectroscopy, we were able to identify ‘pseudocatalase’ activity by observing the decomposition of hydrogen peroxide (H2O2) over time by Dead Sea water. Since patients with vitiligo accumulate millimolar levels of H2O2 in their skin, we followed the degradation of H2O2 in vivo again utilizing the same technique. The results of this in vitro and in vivo study show for the first time a ‘pseudocatalase’ activity of Dead Sea water and provide evidence that the antioxidant properties of Dead Sea water bathing could play an important role in this unique treatment modality. Furthermore, the use of non‐invasive in vivo FT‐Raman spectroscopy introduces an excellent biomedical application in investigative dermatology. Copyright © 2002 John Wiley & Sons, Ltd.

Mixed electronic–ionic conductivity in transition metal oxide glasses containing alkaline ions

In alkali free transition metal oxide glasses conductivity is described by small polaron hopping. The carrier concentration is related to the concentration of transition metal ions in different valence states. Generally ionic conduction depends on the alkali concentration and ion mobility. Assuming that the motion of alkali ions and polarons is independent one may expect that the electrical conductivity increases with the increase in the alkali content. However, real transition metal oxide glasses containing alkali show various behaviors – from strong conductivity anomalies to conductivity weakly dependent on alkali content. A comparison of the electrical properties of iron phosphate glasses containing different amounts of sodium ions and copper oxide glasses to other TMO glass systems has been performed. The influence of the role of transition metal oxide in the glass forming network on the electrical properties of glass has been outlined.

Preparation of wurtzite GaN-based magnetic alloy semiconductors by molecular beam epitaxy

This paper describes the preparation of hexagonal GaN:Mn and GaN:Fe epilayers by molecular beam epitaxy with very high concentrations of transition metal ions which are sufficient to exhibit magnetic orders. We have found that the growth window to obtain epilayers without a macroscopic second phase is relatively large for the GaN:Mn compared with the GaN:Fe. Magnetization data have showed that GaN:Mn epilayers are primarily paramagnetic with the ferromagnetic spin exchange represented by the paramagnetic Curie temperature θp=20K. The effective spin number would be S≈2.5. The GaN:Fe epilayers exhibit superparamagnetic behavior which presumably arises from Fe and/or FeN crystallites.