Bestimmung der Oberflächenzusammensetzung von Calcit in Mg2+-haltigen Ca-45-markierten Lösungen

The Mg²⁺ ion content in the surface layer of calcite in relation to the Mg²⁺ ion content in Ca-45 labelled solution was determined by Ca²⁺-Mg²⁺ ion exchange process. It was found that the increase of the molar ratio Mg/Ca in the surface due to increase of Mg²⁺ concentration in solution is decreasing significantly when approaching ratios of Mg/Ca ～ 1 and ～ 3. The experimental exchange isotherm can be used to relate the Mg/Ca molar ratio of solutions to that of the surface layers of calcite.     

A Highly Copper‐Selective Ratiometric Fluorescent Sensor Based on BODIPY

A new ratiometric fluorescent sensor ( 1 ) for Cu²⁺ based on 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) with di(2‐picolyl)amine (DPA) as ion recognition subunit has been synthesized and investigated in this work. The binding abilities of 1 towards different metal ions such as alkali and alkaline earth metal ions (Na⁺, K⁺, Mg²⁺, Ca²⁺) and other metal ions ( Ba²⁺, Zn²⁺, Cd²⁺, Fe²⁺, Fe³⁺, Pb²⁺, Ni²⁺, Co²⁺, Hg²⁺, Ag⁺) have been examined by UV‐vis and fluorescence spectroscopies. 1 displays high selectivity for Cu²⁺ among all test metal ions and a ～10‐fold fluorescence enhancement in I₅₈₂/I₅₅₈ upon excitation at visible excitation wavelength. The binding mode of 1 and Cu²⁺ is a 1:1 stoichiometry determined via studies of Job plot, the nonlinear fitting of the fluorometric titration and ESI mass.     

1-(d-Glucopyranosyl-2′-deoxy-2′-iminomethyl)-2-hydroxynaphthalene as chemo-sensor for Fe in aqueous HEPES buffer based on colour changes observable with the naked eye

A new glucose-based C2-derivatized colorimetric chemo-sensor (L₁) has been synthesized by a one-step condensation of glucosamine and 2-hydroxy-1-naphthaldehyde for the recognition of transition metal ions. Among the eleven metal ions studied, viz., Mg²⁺, Ca²⁺, Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Hg²⁺, L₁ results in visual colour change only in the presence of Fe²⁺, Fe³⁺and Cu²⁺ in methanol. However, in an aqueous HEPES buffer (pH 7.2) it is only the Fe³⁺ that gives a distinct visual colour change even in the presence of other metal ions, up to a concentration of 280 ppb. The changes have been explained based on the complex formed, and the composition has been determined to be 2:1 between L₁ and Fe³⁺ based on Job’s plot as well as ESI MS. The structure of the proposed complex has been derived based on HF/6-31G calculations.     

Bulgarian natural diatomites: modification and characterization

Natural Bulgarian diatomite modified by oxidation with sulfuric acid and H₂O₂ or by coating with manganese oxide was characterized considering its chemical composition, surface area, pore volume, and structure. Modified diatomites displayed larger surface area and pore volumes in comparison with untreated natural diatomite, which favored their sorption behavior. Sorption properties of diatomites towards Fe³⁺, Pb²⁺, Cu²⁺, Cd²⁺, Mn²⁺, Ni²⁺, Co²⁺, Cr³⁺, Pd²⁺, Ca²⁺, and Mg²⁺ were investigated and their sorption capacities were determined. Sorption properties of manganese oxide-modified diatomite were superior to those of diatomite modified by oxidation. Owing to its high sorption capacity towards Co²⁺, Ni²⁺, Pb²⁺, Cr³⁺, Fe²⁺, Cu²⁺, and Cd²⁺, the manganese oxide-modified diatomite is a promising low-cost sorbent for selective removal of milligram amounts of these toxic metal ions from contaminated water.     

New coumarin-based sensor molecule for magnesium and calcium ions

A new coumarin-based sensor molecule (L₁) has been synthesized and this was found to bind calcium and magnesium ions more effectively as compared to other alkali/alkaline earth/lanthanide and certain transition metal ions. A significant enhancement in fluorescence intensity was observed on binding to Ca²⁺ and Mg²⁺ ions; while a minor quenching was observed for weakly bound Hg²⁺, Ni²⁺, Fe³⁺, and Co²⁺ ions. PET process, coupled with the ICT process, is proposed to explain the observed spectral response.     

Specific Uphill Transport of Zinc as Zn(SCN)42− Ion using Na+-Dicyclohexyl-18-Crown-6 as Carrier

Sodium-dicyclohexyl- 18-crown-6 complex cation was used as carrier for the uphill transport of zinc as Zn(SCN)₄^2? complex anion. By using L-cysteine as a metal ion acceptor in the receiving phase at the optimized pH of 7.6, the amount of zinc transport through the liquid membrane after 90 min was 97.2 ± 1.0%. The selectivity and efficiency of zinc transport from aqueous solutions containing equimolar mixtures of Ag⁺, Cd²⁺ Co²⁺, Cu²⁺, Fe²⁺, Ni²⁺, Pb²⁺, Pd²⁺, Sr²⁺, Bi³⁺, Cr³⁺ and Fe³⁺ ions was investigated. In the presence of NH₂OH.HCl as a suitable masking agent in the source phase, the interfering effect of Cu²⁺ and Pb²⁺ ions was diminished drastically.     

Effect of Complexation on Photocatalytic Degradation of Dissolved Organic Nitrogen Compounds

Abstract

The effect of metal ions on TiO₂ mediated photocatalytic oxidation for the determination of dissolved organic nitrogen compounds is investigated. Ethylenediaminetetraaceticacid was chosen as a model molecule for DON compounds. At pH 2, 5, 7, and 10 aqueous EDTA solutions were irradiated at 254 nm in the presence of Fe²⁺, Cu²⁺, Zn²⁺, Ni²⁺ or Co²⁺ ions. The sum of produced nitrate, nitrite, and ammonium ion concentrations gave the total oxidation recovery. At low pH, the photocatalytic oxidation recoveries of Fe‐EDTA, Ni‐EDTA, and Co‐EDTA were significantly lower than the photocatalytic degradation of EDTA. The presence of free Fe²⁺, Ni²⁺, and Co²⁺ ions decreased the photocatalytic oxidation recovery. The [NH₄ ⁺]/[NO₃ ^?] ratio was higher for Cu‐EDTA.     

Kinetics of the exchange between MnO or Mn3O4 and some divalent cations in aqueous solution

The kinetics of the exchange between MnO or Mn₃O₄ and Co²⁺, Cu²⁺, Ni²⁺, or Zn²⁺ ions in solution, was determined by measuring the γ-activity of⁵⁶Mn acquired by the solution after shaking with the neutron irradiated solid. The results indicated a fast exchange followed by a slower apparently diffusion-controlled exchange. The exchange capacity increased in the series: Co²⁺<Ni²⁺<Cu²⁺=Zn²⁺ for MnO and Ni²⁺<Co²⁺<Zn²⁺<Cu²⁺ for Mn₃O₄. The trends could not be satisfactorily explained by the ionic radii or crystal field stabilisation-energies. In the case of MnO, the results were discussed in terms of the estimated standard enthalpy change of the exchange reaction.     

Membrane Transport of Pb(II) with a Cooperative Carrier Composed of Dibenzyldiaza‐18‐Crown‐6 and Palmitic Acid

A chloroform membrane system containing a given mixture of dibenzyldiaza‐18‐crown‐6 and palmetic acid was applied for transport of Pb²⁺ ions. The transport was capable of moving metal ions “uphill”. Thus, it was possible to follow the transfer of Pb(II) from the aqueous source phase to the organic layer and from the organic layer to the receiving phase. The effects of thiosulfate concentration in the receiving phase, palmetic acid and dibenzyldiaza‐18‐crown‐6 concentration in the organic phase on the efficiency of the transport system were examined. By using S₂O₃^2? ion as metal ion acceptor in the receiving phase, the amount of lead ion transport across the liquid membrane after 150 minutes is 96 ± 1.5%. The selectivity and efficiency of lead transport from aqueous solution containing Cu²⁺, Tl⁺, Ag⁺, Co²⁺, Ni²⁺, Mg²⁺, Zn²⁺, Hg²⁺, Cd²⁺, Ca²⁺ were investigated. In the presence of thiosulfate as a suitable masking agent in the source phase, the interfering effects of Ag⁺ and Cu²⁺ were diminished drastically.     

Color Tuning in Garnet Oxides: The Role of Tetrahedral Coordination Geometry for 3 d Metal Ions and Ligand–Metal Charge Transfer (Band‐Gap Manipulation)

We explored garnet‐structured oxide materials containing 3d transition‐metal ions (e.g., Co²⁺, Ni²⁺, Cu²⁺, and Fe³⁺) for the development of new inorganic colored materials. For this purpose, we synthesized new garnets, Ca₃Sb₂Ga₂ZnO₁₂ ( I ) and Ca₃Sb₂Fe₂ZnO₁₂ ( II ), that were isostructural with Ca₃Te₂Zn₃O₁₂. Substitution of Co²⁺, Ni²⁺, and Cu²⁺ at the tetrahedral Zn²⁺ sites in I and II gave rise to brilliantly colored materials (different shades of blue, green, turquoise, and red). The materials were characterized by optical absorption spectroscopy and CIE chromaticity diagrams. The Fe³⁺‐containing oxides showed band‐gap narrowing (owing to strong sp–d exchange interactions between Zn²⁺ and the transition‐metal ion), and this tuned the color of these materials uniquely. We also characterized the color and optical absorption properties of Ca₃Te₂Zn_3−x Co_x O₁₂ (0<x ≤2.0) and Cd₃Te₂Zn_3−x Co_x O₁₂ (0<x ≤1.0), which display brilliant blue and green‐blue colors, respectively. The present work brings out the role of the distorted tetrahedral coordination geometry of transition‐metal ions and ligand–metal charge transfer (which is manifested as narrowing of the band gap) in producing brilliantly colored garnet‐based materials.     

A Bis‐Oxime Derivative of Diaza‐18‐Crown‐6 as an Ionophore for Silver Ion

A new pendant‐arm derivative of diaza‐18‐crown‐6, containing two oxime donor groups, has been synthesized and incorporated into a polyvinyl chloride (PVC) membrane ion‐selective electrode. The electrode shows selectivity for Ag⁺ ion, with a near Nernstian response. Pb²⁺, Cu²⁺, Hg²⁺, and Tl⁺ are major interfering ions, with Cd²⁺ having minor interference. The electrode shows no potentiometric response for the ions Mg²⁺, Al³⁺, K⁺, Ca²⁺, Ni²⁺, Fe³⁺, and La³⁺, and is responsive to H⁺ at pH<6.     

Graft copolymerization to cellulose by the metallic ion–hydrogen peroxide initiator system

The decomposition of hydrogen peroxide and the graft copolymerization of methyl methacrylate has been investigated by use of cellulose samples adsorbing various metallicions. Metallic ions generally accelerate the decomposition of hydrogen peroxide, increase the number of grafts, and lower the average molecular weight. However their effects are much influenced by the range of pH values. It is clear that the amount of grafts formed is not necessarily proportional to the amount of decomposed hydrogen peroxide and is dependent upon a function peculiar to each metallic ion. The effective metallic ions in the neutral system were Cu²⁺, Ag⁺, Fe²⁺, Co²⁺, Cr³⁺, and Zn²⁺. The effects of Ce³⁺, Mg²⁺, Hg³⁺, Cd²⁺, Ni²⁺ and Mn²⁺ were either negligible or negative. Comparative studies on various conditions confirmed that Fe²⁺ in the neutral system gives graft copolymer having a minimum average molecular weight and the greatest number of grafts.     

Selective and Sensitive Two New Macroacyclic Schiff base Fluorescent Turn-Off Receptors for Fe3+, DFT Calculation and Their Antibacterial Activity

Two new Macroacyclic Schiff base chemosensors (L₁ and L₂) were synthesized by the one pot condensation reaction of 2-[3-(2-formyl phenoxy)propoxy]benzaldehyde and aminophenol in a 1:2 molar ratio and were characterized by IR, NMR spectroscopy. Both Schiff bases displayed high selectivity and sensitivity towards Fe³⁺ over other metal ions in H₂O-DMF solution (Ag⁺,Cu²⁺, Ni²⁺, Zn²⁺, Mg⁺², Mn⁺², Pb⁺², Co⁺², Hg⁺², Cr⁺³, Na⁺, Ba⁺² and Cd²⁺) due to their structure including oxygen donor atoms. The test results showed fluorescence quenching of the fluorophores when Fe³⁺ was bound to the recognition units. From test results, a high selectivity for Fe³⁺ were discovered in this type of sensors, especially, the probe based on 2-aminophenol exhibited more significant quenching in fluorescence intensity compared with 4-aminophenol-based due to its rigidity structure. In addition, the structure of ligands and their antibacterial properties was investigated.     

Photo-physical behavior as chemosensor properties of anthracene-anchored 1,3-di-derivatives of lower rim calix[4]arene towards divalent transition metal ions

Anthracene anchored 1,3-di-derivatives of lower rim p-tert-butyl-calix[4]arene were synthesized and characterized. These derivatives were subjected to the binding studies with the divalent metal ions, viz., Mg²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ using fluorescence and absorption spectra. The imine moiety that is in conjugation with the anthryl unit is responsible for quenching the fluorescence in the absence of metal ion, however, in the presence of Fe²⁺ and Cu²⁺, the spectra showed very high enhancement in fluorescence intensity indicating that the lone pair present on the imine-N is involved in the metal ion binding and as a result the photo-induced electron transfer is prevented. Based on the photo-physical studies, it has been found that the anthracene derivative that is coupled with the calix[4]arene unit through an imine bond acts as a chemosensor for Fe²⁺ and Cu²⁺. The fluorescence studies are further augmented by the absorption spectra.     

Synthesis and characterization of 2, 4-dihydroxy-benzaldehydeoxime-formaldehyde polymers and their application as ion-exchangers

Polymers were prepared by the condensation of 2, 4-dihydroxybenzaldehydeoxime (2, 4-DBO) and formaldehyde (F) in the presence of oxalic acid as catalyst with varying molar ratios of reacting monomers. Polymers were characterized by their IR spectra, elemental analyses, TGA and M_n as determined by vapour pressure osmometry as well as by non-aqueous conductometric titrations. Viscosity measurements of the solutions of polymer samples were carried out in dimethylformamide. Chelation ion-exchange properties have also been studied employing the batch equilibration method. This method involved the measurement of distribution of a given metal between the polymer sample and a solution containing metal ions. The study was carried out over a wide pH range and in media of various ionic strengths. The polymer showed a higher selectivity for UO ₂ ²⁺ and Fe³⁺ ions than for Cu²⁺, Ni²⁺, Co²⁺ and Mn²⁺ ions.     

Complexation of 3-hydroxy-2,2′-iminodisuccinic acid (HIDS) with Mg2+, Ca2+, Mn2+, Fe3+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+ ions in aqueous solution

In a search for environmental-friendly metal chelating ligands for industrial applications, the protonation and complex formation equilibria of 3-hydroxy-2,2′-iminodisuccinic acid with Mg²⁺, Ca²⁺, Mn²⁺, Fe³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ ions in aqueous 0.1 mol L^?1 NaCl solution were studied at 25°C by potentiometric titration. The model for complexation and the stability constants of the different complexes were determined for each metal ion using the computer program SUPERQUAD. In all cases, complex formation was dominated by stable ML ^{n ?4} complexes.     

Synthesis of a Four-Strand N2O2-Donor Ligand and its Transition Metal Complexation Probed by Electrospray Ionisation Mass Spectrometry

The four-strand and potentially N₂O₂-donor ligand 2,3-endo,endo-bis(aminomethyl)-5,6-endo,endo-bis(hydroxymethyl)bicyclo[2.2.1]heptane (L1), a close analogue of the known tetraalcohol 2,3,5,6-endo,endo,endo,endo-tetrakis(hydroxymethyl)bicyclo[2.2.1]heptane (L2), has been prepared via a multi-step synthesis and isolated as the copper(II) complex [Cu(L1)₂](ClO₄)₂. An ESI-MS study of the complex and metal ion exchange with other transition metal ions (Fe²⁺, Co²⁺, Ni²⁺, Mn²⁺ or Zn²⁺) indicates that 1:1 complexes form readily. Apparently special stability for the Ni²⁺ species observed in the ESI-MS study suggests strong encapsulation of this ion.     

A highly selective fluorescent chemosensor for Fe (III) based on rhodamine 6G dyes derivative

A new fluorescent probe L based on the rhodamine 6G platforms for Fe³⁺ has been designed and synthesised. L showed excellent selectivity and high sensitivity for Fe³⁺ against other metal ions such as K⁺, Na⁺, Ag⁺, Cu²⁺, Co²⁺, Mg²⁺, Cd²⁺, Ni²⁺, Zn²⁺, Fe²⁺, Hg²⁺, Ce³⁺ and Y³⁺ in HEPES buffer (10 mM, pH 7.4)/CH₃CN (40:60, V/V). The distinct color change and the rapid emergence of fluorescence emission provided naked-eyes detection for Fe³⁺. The recognition mechanism of the probe toward Fe³⁺ was evaluated by Job’s plots, IR and ESI-MS. In order to further study their fluorescent properties, L + Fe³⁺ fluorescence lifetime was also measured. Moreover, the test strip results showed that these probes could act as a convenient and efficient Fe³⁺ test kit.     

Determination of alkali, alkaline earth and transition metal ions in UO2, ThO2 powders and sintered (Th,U)O2 pellets by ion chromatography

An ion chromatographic method has been developed for the determination of traces of Li⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺, Sr²⁺, Fe³⁺, Cu²⁺, Ni^2+, Co²⁺, Zn²⁺, Cd²⁺, Mn²⁺ in UO₂, ThO₂ powders and sintered (Th,U)O₂ pellets. This new method utilizes poly-(butadiene-maleic acid) (PBDMA) coated silica cation exchange column and mixed functionality column of anion and cation exchange to achieve the separation of alkali, alkaline earths and transition metal ions, respectively. It involves matrix separation after sample dissolution by solvent extraction with TBP (tri butyl phosphate)-TOPO (tri octyl phosphine oxide)/CCl₄. Interference of transition metal ions in the determination of alkali, alkaline earth metal ions are removed by using pyridine 2,6-dicarboxylic acid (PDCA) in the tartaric acid mobile phase. Mobile phase composition is optimized for the base line separation of alkali, alkaline earth and transition metal ions. Linear calibration graphs in the range 0.01–20 μg mL⁻¹ were obtained with regression coefficients better than 0.999. The respective relative standard deviations were also determined. Recoveries of the spiked samples are within ±10% of the expected value. The developed method is authenticated by comparison with certified standards of UO₂ and ThO₂ powders.     

In situ X-ray absorption and diffraction studies of carbon coated LiFe1/4Mn1/4Co1/4Ni1/4PO4 cathode during first charge

Synchrotron based in situ X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) techniques are used to study electronic and crystal structure changes of the carbon coated LiFe_1/4Mn_1/4Co_1/4Ni_1/4PO₄ (LiFe_1/4Mn_1/4Co_1/4Ni_1/4PO₄/C) cathode material for Li-ion batteries during the first charge. In situ Fe, Mn, Co and Ni K-edge XAS results revealed that the three voltage plateaus at ～3.6, 4.2 and 4.7 V vs. Li/Li⁺ are attributed to the redox reactions of Fe²⁺/Fe³⁺, Mn²⁺/Mn³⁺ and Co²⁺/Co³⁺, respectively, while the apparent capacities above 4.9 V is not originated from the Ni²⁺/Ni³⁺ redox, but very likely from the electrolyte decomposition. Interesting phase transition behaviors of LiFe_1/4Mn_1/4Co_1/4Ni_1/4PO₄/C were observed with the formation of an intermediate phase and the solid solution regions. Combined in situ XAS and XRD techniques indicate fast electronic structural changes and slow bulk crystal structural changes.