Theoretical investigations of the spin Hamiltonian parameters for the tetragonal [Rh(CN)4Cl2] complex in KCl

The spin Hamiltonian parameters (g factors, hyperfine structure constants and superhyperfine parameters) for the tetragonal [Rh(CN)₄Cl₂]⁴⁻ complex in KCl are theoretically investigated from the perturbation formulas of these parameters for a 4d⁷ ion in a tetragonally elongated octahedron. This center can be assigned to the substitutional Rh²⁺ on host K⁺ site reduced from Rh³⁺ by capturing one electron during the electron irradiation, associated with the two axial ligands CN⁻ replaced by two Cl⁻. The crystal-fields of the two axial Cl⁻ are weaker than those of the four planar CN⁻, yielding the tetragonal elongation distortion. This system belongs to the case of low spin (S = 1/2) under strong crystal-fields, different from that of high spin (S = 3/2) under weak and intermediate crystal-fields (e.g., 3d⁷ ions such as Fe⁺ and Co²⁺ in conventional chlorides). The calculated spin Hamiltonian parameters show good agreement with the experimental data. The above [Rh(CN)₄Cl₂]⁴⁻ complex due to the different axial and perpendicular ligands is unlike the tetragonally elongated [RhCl₆]⁴⁻ complex due to the Jahn–Teller effect in the similar NaCl:Rh²⁺ crystals.     

Oxygen-17 superhyperfine structure of Rh2+ Jahn-Teller ions in MgO

EPR spectra of the Rh²⁺ impurity centers in MgO crystals labelled with oxygen-17 are reported. Measurements were made at 4.2 K and around liquid nitrogen temperature, which correspond to the (quasi) static and fast averaging regimes of the Jahn-Teller effect. In both temperature ranges satellites due to superhyperfine interaction with ¹⁷O nuclei were observed. The results are analyzed in terms of the covalency parameters of the RhO bond.     

Electrochemical reaction of 5 V cathode LiNi0.4Mn1.6O4

LiNi_0.4Mn_1.6O₄ was prepared under air and oxygen atmospheres using fine Mn₃O₄ particle and large MnO₂ particle at various temperatures. The sample prepared from Mn₃O₄ at 750 °C under air or oxygen atmosphere exhibited an ideal electrochemical behavior, which was based on three redox couples of Mn³⁺/Mn⁴⁺, Ni²⁺/Ni³⁺, and Ni³⁺/Ni⁴⁺. On the other hand, the sample prepared from MnO₂ had a larger capacity at 4 V plateau and smaller one at 5 V plateau. However, when using oxygen atmosphere, the sample exhibited more ideal behavior, which is similar to the sample prepared from Mn₃O₄. This means that some defects exist in LiNi_0.4Mn_1.6O₄, depending on preparation conditions. In order to confirm this point, the chemical composition and the valence state of Mn of the prepared sample was analyzed. From these results, it can be said that electrochemical reactions of LiNi_0.4Mn_1.6O₄ are well explained based on three redox couples of Mn³⁺/Mn⁴⁺, Ni²⁺/Ni³⁺, and Ni³⁺/Ni⁴⁺ by considering a presence of oxygen defects.     

Coumarinic fluorescent chemosensors for the detection of transition metal ions

Fluoroionophores consisting of coumarin-153 linked to mono- and diaza-crown ethers are able to complex transition metal cations (Ni²⁺, Zn²⁺, Cd²⁺) and Pb²⁺, with concomitant large changes in photophysical properties. The stability constants in acetonitrile are higher than 3×10⁶ M ^–1 except for Ni²⁺.     

Solvothermal synthesis of nanocrystalline zinc oxide doped with Mn2+, Ni2+, Co2+ and Cr3+ ions

ZnO nanopowders doped with Mn²⁺, Ni²⁺, Co²⁺ and Cr³⁺ ions have been synthesised for the first time using a solvothermal reaction with microwave heating. The nanopowders were produced from a solution of zinc acetate and manganese (II), chromium (III), nickel (II) and cobalt (II) acetates, using ethylene glycol as a solvent. The content of Ni²⁺, Co²⁺ and Cr³⁺ ions in the solution and in the solid phase were close to each other up to 5 mol%. The doping level of Mn²⁺ ions in the solid is about 50% of that in the solution. No phases or compounds other than ZnO were detected by X-ray diffraction with Mn²⁺, Co²⁺ and Ni²⁺ doping. With Cr³⁺ ions a small amount of chromium oxide was found. None of the powders displayed any luminescence after doping. The Mn²⁺-doped powder displayed a paramagnetic behaviour. ESR and magnetisation investigations have revealed that no clustering of Mn²⁺ ions occurred up to a doping level of 3.9 mol%. The average grain size of powders doped with Ni²⁺, Cr³⁺, Co²⁺ and Mn²⁺ for a 10 mol% ion content in the solution was about 20 nm and the grain size dispersion 30%. With increasing dopant content the grain size decreased. It appears that the solvothermal process employed allows relatively high doping levels of the transition metal ions to be achieved without any dopant clustering or oxide precipitation.     

ESR assessment of 3d7 transition metal impurity states in GaP,GaAs and InP

Photo-sensitive electron spin resonance of the 3d⁷-ions Fe⁺, Co²⁺, Ni³⁺ has been detected and analysed in GaP, GaAs and InP. For GaP : Ni³⁺, hyperfine interaction with the four nearest P³¹-ligands could be resolved.     

Preparation of Zn2+–Ni2+–Fe3+–CO32−LDHs and study of photocatalytic activities for decomposition of Methyl Orange solution

New type photocatalytic materials of Zn²⁺–Ni²⁺–Fe³⁺–CO₃^2?LDHs were prepared by complexing agent-assisted homogeneous precipitation technique and Zn(NO₃)₂·6H₂O, Ni(NO₃)·6H₂O, Fe(NO₃)₃·9H₂O used as raw materials in the case of molar ratio of Zn²⁺/Ni²⁺/Fe³⁺ = 1:6:2. Zn²⁺–Ni²⁺–Fe³⁺–CO₃^2?LDHs having a specific surface area of 96.5 m²/g. The structure and catalytic properties of the material were systematically studied. The experimental results show that the Zn²⁺–Ni²⁺–Fe³⁺–CO₃^2?LDHs has a higher adsorption performance and lower band gap which make it an excellent catalyst for reducing the degradation of the methyl orange. Study on the process of photocatalytic reaction shows that Methyl Orange was adsorbed to the layer of Zn²⁺–Ni²⁺–Fe³⁺–CO₃^2?LDHs, and then it was photodecomposed to inorganic molecules and ions by Zn²⁺, Ni²⁺, and Fe³⁺ on the surface of Zn²⁺–Ni²⁺–Fe³⁺–CO₃^2?LDHs.     

Preparation,characterization, and ion exchange behavior of nanocomposite polyaniline zirconium(IV) selenotungstophosphate for the separation of toxic metal ions

A conducting polymer-based advanced nanocomposite ion exchanger was synthesized by incorporating polyaniline (PANI) into the inorganic counterpart zirconium(IV) selenotungstophosphate (ZSWP). The nanocomposite exhibited an excellent ion exchange capacity of 1.20 meq g^?1 in addition to high thermal stability. The polymeric–inorganic nanocomposite ion exchanger was characterized by Fourier transform infrared (FTIR), XRD, SEM, and TEM studies. The DC conductivity of PANI/ZSWP was also investigated. The nanocomposite ion exchanger was found to be highly selective for Cu²⁺ ions with a distribution coefficient value of 650 mL/g. The analytical applications of the material were explored by achieving selective separations of Cu²⁺ and Ca²⁺ ions from a synthetic mixture of Cu²⁺, Pb²⁺, Zn²⁺, Ni²⁺, Fe³⁺, Mg²⁺, and Al³⁺ and Ca²⁺, Pb²⁺, Zn²⁺, Ni²⁺, Al³⁺, Mg²⁺, and Ba²⁺.     

A Novel Ratiometric Fluorescent Chemosensor for Cd2+

Novel ratiometric fluorescent chemosensor C7 was synthesized and characterized by UV–vis and fluorescence spectroscopy. C7 showed high sensitivity for Cd²⁺ among Na⁺, Mg²⁺, Cu²⁺, Pb²⁺, Ni²⁺, Fe³⁺, Zn²⁺, Ag⁺ Hg²⁺ and Cd²⁺ in ethanol.     

Theoretical study of EPR spectra and local structure for (NiO6) cluster in LiNbO3:Ni and Al2O3:Ni systems

For a d⁸ configuration ion, the 45×45 complete energy matrix, which contains the electron-electron repulsion interaction, the ligand-field interaction, the spin-orbit coupling interaction as well as the Zeeman interaction, has been established. By diagonalizing the complete energy matrix, the local lattice structure, EPR parameters (D, g_//, g_⊥) and optical absorption spectra for Ni²⁺ ions doped in LiNbO₃ and Al₂O₃ have been investigated. The local structure distortion parameters ΔR, Δθ₁ and Δθ₂ are determined for LiNbO₃:Ni²⁺ and Al₂O₃:Ni²⁺ systems, simultaneously. These results show that local structure of (NiO₆)¹⁰⁻ cluster exhibits an elongation distortion in both LiNbO₃:Ni²⁺ and Al₂O₃:Ni²⁺ systems, in spite of the different reasons of the elongation in both systems. In addition, we have found that the orbit reduction effect is very important to understand the anisotropic g-factors for Ni²⁺ ions doped in LiNbO₃ and Al₂O₃ crystals.     

The effect of pH and role of Ni in zinc phosphating of 2024-Al alloy: Part I: Macroscopic studies with XPS and SEM

Coatings formed on 2024-T3 aluminum alloy were studied by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) after dipping in zinc phosphating (ZPO) baths at different acidities, for different lengths of time, and with or without Ni²⁺ additive. The overall objective was to learn more about the role of Ni²⁺ on the ZPO coating mechanism, particularly since this additive is believed to improve corrosion protection for the Al alloy. Secondary phosphates dominate the coatings when the Ni-containing solution is adjusted to starting pH values of either 3 or 5, while tertiary phosphate is predominant at pH 4. AlF₃ precipitates during the early stages of the coating process. Ni²⁺ has two main roles in the mechanism. First, the rate of increase in local solution pH is retarded by the slower kinetics of reactions involving Ni²⁺ compared to Zn²⁺, leading to thinner ZPO coatings when Ni²⁺ is present in the coating solution. Second, most Ni²⁺ deposition occurs during the later stages of the coating process, by nickel phosphate deposition and/or by formation of a Ni-rich oxide.     

CALCULATION OF THE TRANSITION ENERGIES OF THE Ne-LIKE IONS WITH THE CORRECTION OF CORE POLARIZATION

The transition energies between n=3 and n=2 of the Ne-like ion Ge²²⁺, Se²⁴⁺, Zr³⁰⁺, Rh³⁵⁺, Ag³⁷⁺, Sb⁴¹⁺, Xe⁴⁴⁺, La⁴⁷⁺, Nd⁵⁰⁺ and Eu⁵³⁺ are calculated by adding polarization in the core. The systematic errors in multi-configuration Dirac-Fock calculation are greatly reduced and a good agreement is obtained between the theory and the experiment. This study shows that introducing the polarization of core orbitals is a good method to calculate the atomic structure, and there is a close relation between polarizability and nucleus charge.     

Removal of heavy metals from aqueous solutions using Fe3O4, ZnO, and CuO nanoparticles

This study investigated the removal of Cd²⁺, Cu²⁺, Ni²⁺, and Pb²⁺ from aqueous solutions with novel nanoparticle sorbents (Fe₃O₄, ZnO, and CuO) using a range of experimental approaches, including, pH, competing ions, sorbent masses, contact time, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The images showed that Fe₃O₄, ZnO, and CuO particles had mean diameters of about 50?nm (spheroid), 25?nm (rod shape), and 75?nm (spheroid), respectively. Tests were performed under batch conditions to determine the adsorption rate and uptake at equilibrium from single and multiple component solutions. The maximum uptake values (sum of four metals) in multiple component solutions were 360.6, 114.5, and 73.0?mg?g^?1, for ZnO, CuO, and Fe₃O₄, respectively. Based on the average metal removal by the three nanoparticles, the following order was determined for single component solutions: Cd²⁺?>?Pb²⁺?>?Cu²⁺?>?Ni²⁺, while the following order was determined in multiple component solutions: Pb²⁺?>?Cu²⁺?>?Cd²⁺?>?Ni²⁺. Sorption equilibrium isotherms could be described using the Freundlich model in some cases, whereas other isotherms did not follow this model. Furthermore, a pseudo-second order kinetic model was found to correctly describe the experimental data for all nanoparticles. Scanning electron microscopy, energy dispersive X-ray before and after metal sorption, and soil solution saturation indices showed that the main mechanism of sorption for Cd²⁺ and Pb²⁺ was adsorption, whereas both Cu²⁺ and Ni²⁺ sorption were due to adsorption and precipitation. These nanoparticles have potential for use as efficient sorbents for the removal of heavy metals from aqueous solutions and ZnO nanoparticles were identified as the most promising sorbent due to their high metal uptake.     

Enhanced superhyperfine interaction on Ru3+ in Tm3Al5O12 and on Ru3+ and Yb3+ in Tm3Ga5O12

Measurements of the enhanced superhyperfine interaction linking the electron spin of an impurity EPR ion and the nuclear moments of Van Vleck host lattice ions are reported for Ru³⁺ in Tm₃Al₅O₁₂ and for Ru³⁺ and Yb³⁺ in Tm₃Ga₅O₁₂. The Ru³⁺ results appear to be the first reported where this interaction is large enough to give rise to a well resolved superhyperfine structure. For Yb³⁺ the observed temperature dependent line narrowing evidences the role of Tm spin fluctuations.     

8-Hydroxyquinoline Functionalized Graphene Oxide: an Efficient Fluorescent Nanosensor for Zn<Superscript>2+</Superscript> in Aqueous Media

A nanosensor, based on 8-hydroxyquinoline functionalized graphene oxide, was developed for the fluorescence detection of Zn²⁺. It showed high selectivity and sensitivity for Zn²⁺ion in aqueous solution over other metal ions such as Li⁺, Na⁺, Ca²⁺, Mg²⁺, Al³⁺, Cd²⁺, Co²⁺, Cu²⁺, Hg²⁺, Ni²⁺, Pb²⁺, Fe²⁺, Fe³⁺and Cr³⁺. Due to the linearity of the emission intensity toward Zn²⁺ concentration, fluorescent technique could be used for the detection of Zn²⁺ ion even at very low concentrations.     

Superhyperfine structure of the EPR spectra of Nd<Superscript>3+</Superscript> and U<Superscript>3+</Superscript> ions in Li<Emphasis Type="Italic">R</Emphasis>F<Subscript>4</Subscript> (<Emphasis Type="Italic">R</Emphasis> = Y,Lu, Tm) double fluorides

The superhyperfine structure of the EPR spectra of impurity Nd³⁺ and U³⁺ ions in LiYF₄, LiLuF₄, and LiTmF₄ double-fluoride single crystals has been observed and discussed. In LiYF₄: Nd (g _| = 1.987, g _⊥ = 2.554) and LiTmF₄: Nd, the superhyperfine structure is observed at the orientation of the external magnetic field B in parallel to the c axis of the crystals and consists of nine components with a splitting of ∼15.4 MHz. In LiYF₄: U (g _| = 1.149, g _⊥ = 2.508) and LiLuF₄: U, the superhyperfine structure is observed at both B | c and B ⊥ c and consists of nine and eleven components, respectively, with a splitting of ∼21.5MHz. It should be noted that the resolution of the superhyperfine structure of the EPR spectrum of LiLuF₄: U³⁺ becomes significantly higher with a deviation from the orientation B ⊥ c.     

Superhyperfine interaction in the trigonal center BaF2: Gd3+ and the lattice distortion analysis in the vicinity of the impurity ion

The constants of the superhyperfine interaction of Gd³⁺ with the ¹⁹F nuclear spins in the first four coordination shells were determined from the ENDOR spectra of a trigonal BaF₂: Gd³⁺ center. These data were used for analysis of the crystalline lattice distortions in the vicinity of the impurity ion. It was found that the largest displacements of fluorine nuclei occurred in the vicinity of the ion compensator and the impurity ion. To calculate the anion positions within the first coordinate shell, whose electron-nuclear interaction with Gd³⁺ depends considerably on chemical bonds in the Gd³⁺F ₈ ^? complex, an empirical model is used for the isotropic constants of the superhyperfine interaction of Gd³⁺ with fluorine nuclei in cubic centers, with allowance made for the impurity ion polarization.     

Selective extraction of palladium(II) using hydrazone ligand: A novel fluorescent sensor

The acyclic tridentate blue luminescent ligand (λ_ex=300 nm, λ_em=415 nm) quinoline-2-carboxaldehyde 2-pyridylhydrazone, HL, 1, was recognized as a new fluorescent chemosensor for Pd²⁺. In alkaline methanol complete fluorescent quenching was observed in the presence of 2 equivalents of Pd²⁺ that was further reflected in the solid phase fluorescence microscopic study.Ligand formed 1:1 complexes with Ni²⁺, Cu²⁺, Zn²⁺, Pd²⁺ and 1:2 complexes with Co²⁺, Fe²⁺ as obtained from Job's plot of continuous variation. The binding constants of different metal complexes (Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Pd²⁺) were estimated by fluorescence titrations. The ligand can selectively extract significant amount of Pd²⁺ from the aqueous mixture of metal ions, and the extraction efficiency was increased from 80% to 95% with increase in the molar ratio of HL, 1, to Pd²⁺ from 1 to 3. No significant interference was observed up to 2-fold excess addition of Cu²⁺ and Zn²⁺ and 100-fold excess addition of Co²⁺, Fe²⁺ and Ni²⁺over the Pd²⁺ ion concentration (1.0×10⁻³ M).     

Electron energy-loss spectroscopy of UHV-cleaved NiO (100) surfaces

Electron energy-loss spectroscopy of ～ 200 eV electrons has been applied to the study of the electronic states of clean NiO (100) surfaces. Initial attempt has been made on the identification of observed peaks, and they are attributed to the one-electronic transitions (O^2-2p → Ni²⁺3d, 4s and 4p; Ni²⁺3d → 4p, 3p → 3d and 4s), and the collective excitations (bulk plasmons of O^2-2p, Ni²⁺3d electrons, and coupled 2p and 3d electrons).     

Optical properties of 3d-ions doped RbCdF3. Radiation effects

Abstract

The optical properties of RbCdF₃ crystals doped with Cr³⁺, Mn²⁺ and Ni²⁺ have been studied. Absorption and photoluminescence spectra correspond to these ions in an octahedral environment. The lifetimes of the emitting levels have been measured at different temperatures. Single exponential decays are obtained for Mn²⁺ and Ni²⁺ while a non-exponential decay is found in the case of Cr³⁺. Radiation effects have also been studied. A new absorption band is produced in the 305 nm region by RT X-irradiation. Exciting with light in this band the 3d-ions emissions are observed.