Colorimetric and fluorescent sensing of transition metal ions in aqueous medium by salicylaldimine based chemosensor

The cation sensing property of highly sensitive chromogenic receptor N, N′-bis (salicylidine)-o-phenylene diamine (receptor 1) was studied by visual observation, UV–vis spectroscopy and fluorescence spectroscopy. The proposed study has been targeted to sense the first transition series metal cations like Fe³⁺, Co²⁺, Ni²⁺ and Cu²⁺. Binding affinity toward Cu²⁺ is found to be of higher magnitude compared to the other three cations mentioned. Receptor 1 on binding with Fe³⁺, Co²⁺ Ni²⁺ and Cu²⁺ ions shows fluorescence enhancement which is due to the inhibition of PET mechanism.     

Photochemical and complexation studies for new fluorescent and colored chelator

The photo-induced intramolecular proton (or hydrogen atom) transfer (ESIPT) and metal binding properties of Oxa-ester were studied in methanol solution. The dissociation constant between Oxa-ester and the metal ion was highly dependent with the metal ion and was determined by Hill plots or iterative least squares fitting to be 447 mM, 14.9 μM, and 290 nM for Ca²⁺, Zn²⁺, and Cu²⁺, respectively, in methanol. The fluorescence intensity of Oxa-ester greatly increased with increasing concentration of Zn²⁺, while the fluorescence intensity decreased with the addition of Ca²⁺ and Cu²⁺. Transient absorption spectroscopy revealed that Oxa-ester underwent ESIPT to give Z-NH isomer in the excited state in benzene, while Oxa did not undergo ESIPT probably due to the hydrogen bonding with solvent water.     

Highly efficient fluorescence probe for copper (II) ions based on gold nanoclusters supported on wool keratin

A highly efficient fluorescence gold nanoclusters probe for copper (II) (Cu²⁺) ions among various ions has been prepared through wool keratin as chelating and reducing agent. The main features of fluorescent gold nanoclusters supported on wool keratin (AuNCs@WK) probe are the high fluorescence in aqueous solution, the simplicity of synthesis and the hypotoxicity for living cells. The fluorescence probe exhibits high stability of pHs and shows more sensitivity under acidic condition. Upon exposure to various metal irons, only AuNCs@WK system with Cu²⁺ ions shows a fluorescence turnoff response changing from red to blue under UV light, which lead to the dramatically decreased fluorescent intensity of AuNCs@WK at 690 nm. Moreover, the high sensitivity of AuNCs@WK around 1 µM meets the need of detection standards. The slope of Stern–Volmer plot at low concentration of Cu²⁺ ions is greater than it at high concentrations, which indicates the aggregated AuNCs are from small amounts to large numbers with the increasing concentration of Cu²⁺ ions. The design mechanism of AuNCs@WK probe is the coordination of reactive groups to produce the complex (wool keratin-Cu-wool keratin) at 1:2 between Cu²⁺ ions and fluorescence probe. Furthermore, the cytotoxicity in cells indicates that AuNCs@WK system is safe for the selective imaging of copper ions in living cells.     

Theoretical Investigations on the Anomaly of the g Factors and Local Structure for LaCuO3?δ

The anomaly of the g factors and local structure for LaCuO_3??? are theoretically investigated from the perturbation formulas of the g factors for a 3d ⁹ ion in tetragonally distorted tetrahedra based on the cluster approach including the ligand contributions. The anomaly (g _??>2>g _??) of the g factors is ascribed to the paramagnetic Cu²⁺ (originating from the host diamagnetic Cu³⁺ capturing one electron under oxygen deficiency) in a tetragonally elongated tetrahedron. The tetragonal distortion angle is found to be about 3.56° (i.e., the Cu²⁺?CO^2? bond angle related to the C₄ axis is 3.56° smaller than that (??54.74°) of a regular tetrahedron) due to the Jahn?CTeller effect. The coordination number decreases from the original six for the host octahedral Cu³⁺ in LaCuO_3??? to four for the tetrahedral impurity Cu²⁺ in LaCuO_3??? arising from incomplete Cu²⁺?CO^2? bonding due to oxygen deficiency and some Cu²⁺ locating in the surface of the sample.     

Synthesis and photochemical properties of Cu2+ doped layered hydrogen titanate

Cu²⁺ doped layered hydrogen titanate was prepared by the calcination of K₂CO₃, TiO₂ and CuO mixtures with the K₂CO₃:TiO₂:CuO molar ratio of 1:2.5(1−x):2.5x at 1200°C for 5 h followed by an ion-exchange reaction in 1 M HCl solution. The crystalline phase changed from monoclinic hydrogen tetratitanate to an orthorhombic lepidocrocite-type hydrogen titanate by increasing the amount of Cu²⁺ doped. Both compounds could be excited by visible light irradiation (λ>400 nm) and were capable of hydrogen gas evolution from an aqueous methanol solution, where the photocatalytic activity of Cu²⁺ doped hydrogen tetratitanate was slightly greater than that of Cu²⁺ doped lepidocrocite-type hydrogen titanate. The photocatalytic activity of Cu²⁺ doped hydrogen tetratitanate was enhanced by constructing Pt and TiO₂ pillars in the interlayer, and the incorporation of Pt in Cu²⁺ doped hydrogen tetratitanate enabled the cleavage of water into hydrogen and oxygen by irradiating visible light (λ>400 nm) without a sacrificial hole acceptor.     

Metal-reduction-induced changes in the paramagnetic properties and the rate of oxygen and hydrogen exchange in copper-containing coal-tar carbon fibers

Changes in the binding of copper to a carbon matrix during the reduction of Cu²⁺ ions to metallic state (Cu⁰) influence the EPR spectra of unpaired electrons and the rate of hydrogen (H₂) and oxygen (O₂) exchange in coal-tar carbon fibers (CFs) with copper chloride (CuCl₂ · 2H₂O) deposited from solution. In the presence of the carbon matrix, Cu²⁺ ions are reduced to Cu⁰ by H₂ at a lower temperature (150°C) than in a pure copper salt. The Cu²⁺ → Cu⁰ transition on the CF surface is accompanied by changes in the EPR spectra of unpaired electrons (g value, linewidth, saturation of resonance transitions). The binding of H₂ to the CF-Cu⁰ surface becomes stronger and the rate of H₂ displacement by O₂ from the pores decreases and becomes equal to the rate of O₂ displacement by H₂.     

Effect of metal ions on reactive dye decolorization by laccase from Ganoderma lucidum

In this work, the influence of different metal ions on laccase activity and laccase-catalyzed dye decolorization was investigated under in vitro conditions using crude laccase obtained from a white rot fungus Ganoderma lucidum. Laccase activity was enhanced by metal ions such as Ca²⁺, Co²⁺, Cu²⁺ and Zn²⁺ at low concentrations (1 mM). Increasing the concentration of metal ions except that of Cu²⁺ and Zn²⁺ up to 5 mM and above decreased the enzyme activity. Among several heavy metals, Fe²⁺ highly inhibited the enzyme activity. Effect of metal ions was tested on decolorization of two reactive dyes, namely Remazol black-B (RB-5) and Remazol brilliant blue R (RBBR) at a concentration of 50 mg l⁻¹. The presence of heavy metals generally did not exert much influence on the decolorization except Fe²⁺. Cu²⁺ and Cr⁶⁺ enhanced the decolorization of both dyes. In the presence of 1 mM Cu²⁺, 94% of RB-5 and 35.5% of RBBR were decolorized during 1 h incubation. G. lucidum laccase was able to tolerate mixture of several metal ions. Treatment of simulated reactive dye effluent by laccase showed that the redox mediator system is necessary for effluent decolorization. Syringaldehyde, a natural redox mediator, was very effective than the synthetic mediator 1-hydroxybenzotriazole (HBT). The initial rate of effluent decolorization in presence of syringaldehyde (0.0831 h⁻¹) was 5.6 times higher than HBT (0.0152 h⁻¹). Although the rate of decolorization was markedly decreased in the effluent containing mixed metal ions, presence of syringaldehyde showed effective decolorization. This study indicates that G. lucidum laccase and natural redox mediator system could be a potential candidate for color removal from reactive dye effluent.     

Cylindrical-design,dehydration, and sorption properties of easily synthesized magnesium phosphosilicate nanopowder

Nanoparticles of magnesium phosphosilicate (MgPSi) with enhanced sorption properties have successfully synthesized using (NH₄)₂HPO₄ as precipitating media. Structure, morphology, and dehydration changes of the synthesized nanopowder were detected using differential thermal analysis (DTA)–thermal gravimetric analysis, scanning electron microscopy (SEM), X-ray powder diffraction, Fourier transform infrared, and X-ray fluorescence. Studies appeared that, the MgPSi have semicrystalline stain with diameter of ～40?nm. SEM image indicated that MgPSi particles were distributed as nanoclumps of cotton-wool morphology after heating up to 400°C. The order and activation energy of main dehydration processes were estimated from DTA-thermogram. Evaluation of MgPSi as new adsorbent was investigated for Cu²⁺, Ni²⁺, and Co²⁺ through a batch technique. MgPSi nanopowder was fabricated into adsorption surface by pressing into cylindrical beads. The kinetic adsorption of Cu²⁺, Ni²⁺, and Co²⁺ onto MgPSi can be qualified by a pseudo-second-order model very well. The adsorption of Cu²⁺, Ni²⁺, and Co²⁺ onto MgPSi is strongly relying on pH and also temperature. The adsorption isotherms are fitted well by Freundlich model. This cylindrical layout make it has an excellent physical stability, soft to handle and provided a pathway to fulfill the target of adsorption and recycling ability than the powder form.     

N-methacryloyl-(l)-histidine methyl ester carrying porous magnetic beads for metal chelate adsorption of cytochrome c

A magnetic metal-chelate adsorbent utilizing N-methacryloyl-(l)-histidine methyl ester (MAH) as a metal-chelating ligand was prepared. MAH was synthesized using methacryloyl chloride and l-histidine methyl ester. Magnetic beads with an average diameter of 50–100 μm were produced by suspension polymerization of ethylene glycol dimethacrylate (EGDMA) and MAH carried out in a dispersion medium. Specific surface area of the magnetic beads was found to be 80 m²/g. Elemental analysis of the magnetic beads for nitrogen was estimated as 70 μmol MAH/g polymer. Magnetic beads were complexed with the Cu²⁺ ions directly via MAH for the adsorption of cytochrome c from aqueous solutions. The cytochrome c adsorption on the mag-poly(EGDMA–MAH) beads was 51 mg/g. Cu²⁺ complexing increased the cytochrome c adsorption significantly. The maximum cytochrome c adsorption capacity of the Cu²⁺-chelated beads (carrying 68 μmol Cu²⁺ per gram of polymer) was found to be 222 mg/g at pH 8.0 in phosphate buffer. Cytochrome c adsorption decreased with increasing temperature. Cytochrome c molecules could be reversibly adsorbed and desorbed ten times with the magnetic adsorbents without noticeable loss in their cytochrome c adsorption capacity. The resulting magnetic chelator beads posses excellent long term storage stability.     

The structure and ferromagnetic properties of (Fe0.12CuxZn0.88−x)O thin films deposited on Si substrates by R.F. sputtering

Fe–Cu co-doped ZnO thin films deposited on silicon substrates were prepared by R.F. magnetron sputtering. The effects of various amounts of copper on the microstructure, surface morphology, composition, and magnetic properties of ZnO thin films were examined. The results of the experiments show that the structures of the ZnO thin films grown on the silicon substrate have a preferred orientation of (002). By increasing the copper concentration, the Fe ions exist as Fe²⁺ in the Fe_0.12Cu_xZn_0.88−xO system, but Cu²⁺ and Cu¹⁺ ions coexist when the Cu replaces the Zn. In addition, the ZnO thin films show ferromagnetic behaviour at room temperature and the largest saturation magnetization (Ms) is 5.64 × 10⁴ A/m for the as-grown Fe_0.12Cu_0.02Zn_0.86O thin film.     

Third order optical susceptibilities of the Cu2O thin film

By performing Z-scan method with a femtosecond laser (800 nm, 50 fs, 1 kHz), we investigated the third-order optical nonlinearities of a cuprous oxide (Cu₂O) film. Single-phase Cu₂O film deposited on a quartz substrate was obtained using the pulsed laser deposition technique. The structure properties, surface morphology and optical transmission spectrum were characterized by X-ray diffraction, scanning electron microscopy and double beam spectrophotometer, respectively. The Z-scan results show that the Cu₂O film exhibits large nonlinear refractive index, n₂ = 3 × 10^− 3 cm²/GW, while the two-photon absorption coefficient, α₂ = 40 cm/GW, is relatively small. It implies that the Cu₂O film is a promising candidate for nonlinear photonic devices.     

Preparation and characterization of transition metal-modified lacunary Keggin 11-tungstophosphates supported on carbon

Transition metal-modified lacunary Keggin heteropolycompounds [PW₁₁O₃₉M]⁵⁻, with M = Ni²⁺, Co²⁺, Cu²⁺, or Zn²⁺, were synthesized and characterized. These heteropolycompounds were used to prepare the carbon-supported catalysts. Both the heteropolycompounds and the carbon-supported catalysts showed FT-IR spectra with the characteristic bands of these compounds and provided an indirect measure of the interaction strength between M and the oxygen of the central tetrahedron group of the Keggin structure. The anion decomposition of the modified compounds takes place at equal or lower temperature than that of the bulk and supported parent lacunary [PW₁₁O₃₉]⁷⁻ anion. The species present on the support surface may be highly dispersed as a non-crystalline form, as a result of the interaction with the support surface groups. The activity of the synthesized catalysts in isopropanol dehydration, reflecting their acidity, increases as the reduction temperature of the decomposition products of the heteropolycompounds decreases. It may be assumed that the generation of acid sites is a result of the interaction of hydrogen, donated by isopropanol during its decomposition, with the M cation, leading to M reduction and protons.     

Multifunctional Zn0.99−xMn0.01CuxS nanowires: Structure, luminescence and magnetism

The wurtzite-type Zn_0.99−xMn_0.01Cu_xS (x = 0, 0.003, 0.01) nanowires were prepared by a simple hydrothermal method at 180 °C. The structure and morphology of the samples were characterized by X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), field emission scanning electron micrograph (FESEM) and X-ray photoelectron spectrum (XPS). The results showed that both the Mn²⁺ and Cu²⁺ ions substituted for the Zn²⁺ sites in the host ZnS. The ethylenediamine-mediated template was observed, which was used to explain the growth mechanism of the nanowires. The color-tunable emission can be obtained by adjusting the concentrations of Mn²⁺ and Cu²⁺ ions. The ferromagnetism was observed around room temperature.     

Catalyst preparation through ion-exchange of zeolite Cu-, Ni-, Pd-, CuNi- and CuPd-ZSM-5

Ion-exchanged zeolite ZSM-5 is the best known catalyst for direct NO_x decomposition and a viable candidate for NO_x reduction with methane. The preparation is crucial for the efficiency of the conversion and this paper describes the ion-exchange, with Cu²⁺, Ni²⁺ or Pd²⁺, and the dual exchange, with Cu²⁺/Ni²⁺ or Cu²⁺/Pd²⁺, under appropriate pH and ion concentrations for maximum dispersion.     

Cu-doping effect on structure and magnetic properties of Fe-doped ZnO powders

Fe-doped and Cu, Fe co-doped ZnO diluted magnetic semiconductors powders were synthesized by sol–gel method. The x-ray diffraction (XRD) results showed that Zn_0.97−xFe_0.03Cu_xO (x ≤ 0.02) samples were single phase with the ZnO-like wurtzite structure. X-ray photoelectron spectroscopy (XPS) showed that Fe²⁺ and Fe³⁺ existed in Zn_0.97Fe_0.03O, while Fe²⁺, Fe³⁺and Cu⁺, Cu²⁺ were found in Zn_0.95Fe_0.03Cu_0.02O. Both Zn_0.97Fe_0.03O and Zn_0.95Fe_0.03Cu_0.02O exhibited ferromagnetic performance at room temperature. But the Cu incorporation reduced the saturation magnetization of Fe-doped ZnO diluted magnetic semiconductors.     

In situ incorporation of well-dispersed Cu–Fe oxides in the mesochannels of AMS and their utilization as catalysts towards the Fenton-like degradation of methylene blue

Multi-components active metal oxide-supported catalysts are highly promising in heterogeneous catalysis due to some special promoting effects. In this study, by the controllable amount of Cu, Cu–Fe decorated anionic surfactant-templated mesoporous silica (Cu _x Fe/AMS) was directly prepared. The obtained catalysts were characterized by X-ray diffraction, N₂ adsorption–desorption, inductively coupling plasma emission spectroscopy, scanning electron microscopy, transmission electron microscopy, UV–visible, hydrogen temperature-programmed reduction, and X-ray photoelectron spectroscopy techniques. The results revealed that bimetallic Cu–Fe oxides were directly formed and highly dispersed in the mesochannels during the calcinations and the introduction of Cu²⁺ and Fe²⁺ on the micelles has influence on the structure properties. As compared to the monometallic Fe-modified AMS, the presence of Cu promotes the effects between Fe species and silica wall, leading to the better dispersion of Fe in the mesochannels of AMS. Finally, a series of Cu–Fe-modified AMS were used as Fenton-like catalysts and exhibited good catalytic activity in the degradation of methylene blue (MB), which resulted from high dispersion of Fe species and synergetic effect between Cu and Fe active sites. 1.0 was the optimum molar ratio of Cu²⁺ to Fe²⁺ ions to achieve the best catalytic activity and stability.     

Waste calcite sludge as an adsorbent for the removal of cadmium, copper, lead, and zinc from aqueous solutions

Sludge residues, an industrial waste material for the removal of cadmium (Cd²⁺), copper (Cu²⁺), lead (Pb²⁺), and zinc (Zn²⁺) from aqueous solutions were investigated using batch method. Batch mode experiments were carried out as a function of solution pH, adsorbent dosage, initial concentration, and contact time. The results indicated that the adsorbent showed good sorption potential and maximum metal removal was observed at pH ≥?3. Within 120?min of operation, about 63.7, 95.2, 99.9, and 88.2% of Cd²⁺, Cu²⁺, Pb²⁺, and Zn²⁺ ions were removed from the solutions, respectively. Sorption curves were well fitted to the Langmuir and Freundlich models. The adsorption capacities for Cd²⁺, Cu²⁺, Pb²⁺, and Zn²⁺ ions at optimum conditions were 121.2, 1067.8, 566.4, and 534.2?mg?g^?1, respectively. The kinetics of Cd²⁺, Cu²⁺, Pb²⁺, and Zn²⁺ adsorption from aqueous solutions was analyzed by fitting the experimental data to pseudo-first- and pseudo-second-order kinetic models. However, the pseudo-first-order kinetics model provided much better R ² values and the rate constant was found to be 0.001?min^?1 for Cd²⁺, Cu²⁺, Pb²⁺, and Zn²⁺ ions. The results revealed that sludge residues can adsorb considerable amount of Cd²⁺, Cu²⁺, Pb²⁺, and Zn²⁺ ions and it could be an economical method for the removal of these ions from aqueous systems.     

Synthesis and equilibrium studies of titanium vanadate and its use in the removal of some hazardous elements

Titanium vanadate was synthesized and characterized by X-ray diffraction, thermal analysis (TGA and DTA), X-ray fluorescence, and IR spectroscopy. The empirical formula of titanium vanadate is Ti₂V₂O₉·2.5H₂O. Titanium vanadate was tested as sorbent for removing some harmful ions such as Cs, Co, Cu, and Cd. The distribution coefficients (K _d) were determined. They decrease in the order Cs⁺ ? Cu²⁺ > Co²⁺ > Cd²⁺. The distribution coefficients increase with increasing pH and reaction temperature. The thermodynamic functions of sorption (ΔH ⁰, ΔS ⁰, ΔG ⁰) were calculated. Negative values of ΔG ⁰ and positive values of ΔH ⁰ show that the sorption is a spontaneous endothermic reaction.     

In situ e.s.r. monitoring of the coordination and oxidation states of copper in Cu-ZSM-5 up to 500°C in flowing gas mixtures: 1. Interaction with He,O2, NO,NO2, and H2O

A flow cell was designed for the monitoring of the state of copper ions in Cu-ZSM-5 in situ at high temperatures by e.s.r. In thoroughly purified He or in vacuum there is no spontaneous reduction of the cupric ions up to 500°C. The formation of adsorption complexes between isolated Cu²⁺ cations and NO molecules at 20°C leads to a measurable change in coordination. Strong adsorption complexes of Cu²⁺ with NO₂ are formed on treatment of CuH-ZSM-5 by an [NO + O₂] mixture. Bonding of Cu²⁺ ions with such strong ligands as NO₂ or H₂O attenuates the spin-lattice interaction between Cu²⁺ and the zeolitic framework. The number of Cu²⁺ ions in CuH-ZSM-5 is quantified by the use of the e.s.r. signal of frozen, dilute water solutions of CuSO₄ as a reference. In the samples used in this work the e.s.r. signal is associated with all the copper introduced into ZSM-5 by ion-exchange.     

The effect of Cu content on the structure of Ni1−xCuxFe2O4 spinels

A series of Ni_1−xCu_xFe₂O₄ (0 ≤ x ≤ 0.5) spinels were synthesized employing sol-gel combustion method at 400 °C. The decomposition process was monitored by thermal analysis, and the synthesized nanocrystallites were characterized by X-ray diffraction, transmission electron microscopy, infra-red and X-ray photoelectron spectroscopy. The decomposition process and ferritization occur simultaneously over the temperature range from 280 °C to 350 °C. TEM indicates the increase of lattice parameter and particle size with the increase of copper content in accordance with the XRD analysis. Cu²⁺ can enter the cubic spinel phase and occupy preferentially the B-sites within x = 0.3, and redundant copper forms CuO phase separately. A broadening of the O 1s region increases with the increment of copper content compared to pure NiFe₂O₄, showing different surface oxygen species from the spinel and CuO. Cu²⁺ substitution favors the occupancy of A-sites by Fe³⁺.