Energy transfer between samarium and europium in phosphate glasses

A study of energy transfer from samarium to europium in phosphate glasses was performed for a range of donor and acceptor concentrations corresponding to a donor-acceptor distance of 13–24 Å. The energy transfer probabilities were calculated. The mechanism of transfer was deduced by fitting the experimental decay curves to the theoretical curves obtained by Inokuti and Hiroyama. Theoretical transition probabilities based on Dexter's formula were calculated. It was inferred that the energy is transferred by a dipole-quadrupole mechanism which is assisted by phonons. It was possible to indicate the path by which the transfer takes place.     

Synthesis of the europium organic phosphate and phosphoramide complexes

Organic phosphates and phosphoramidates containing alkoxysilyl group were synthesized and used to obtain the corresponding europium complexes. The latter are shown to be applicable for the formation of organic-inorganic hybrids with the components connected with each other through a chemical bond.     

On-line preconcentration of phosphate onto molybdate form anion exchange column

In this paper, we describe an automated flow injection system for measuring the concentration of phosphate based on a fluorescence quenching reaction between Rhoadamine 6G and phosphomolybdate with a preconcentration column, which was packed with a molybdate-form ion exchange resin to collect and preconcentrate the phosphate in the sample solution. Rhodamine 6G was chosen because the reaction with phosphomolybdate was fast and did not require heat. For the construction of a stable flow injection system, an aqueous methanol solution was used as the cleaning reagent to overcome the precipitation of ion-associated complexes between Rhodamine 6G and phosphomolybdate or Rhodamine 6G and molybdate. For the preconcentration and collection of the phosphate ions in a water sample, a preconcentration column, which was packed with a molybdate-form ion exchange resin, was combined with the proposed flow injection system and applied to natural water samples containing low concentrations of phosphate.     

Sorption studies of europium on cerium phosphate using Box-Behnken design

Amorphous cerium phosphate was prepared and characterized. Three-level Box-Behnken design (BBD) was employed to analyze the effect of process variables such as initial pH (2–6), contact time (60–180 min), and sorbent amount (0.05–0.15 g) on the sorption capacity of europium. Analysis of variance (ANOVA) revealed that the main effect of initial pH and sorbent amount has a substantial impact on the sorption of Eu(III). Probability F-value (F = 3 × 10^-3) and correlation coefficient (R2 = 0.97) point out that the model is in good accordance with experimental data. The maximum sorption capacity of Eu(III) was found to be 42.14 mg g^-1 at initial pH 6, contact time of 180 min, and a sorbent amount of 0.05 g. Sorption isotherm data was well explained by the Langmuir model and monolayer Eu(III) sorption capacity was obtained as 30.40 mg g^-1. Kinetic data were well described by the pseudo-second-order model. Thermodynamic data suggested that the process is endothermic and spontaneous.     

Solvent extraction-spectrophotometric determination of phosphate with molybdate and malachite green in river water and sea-water

Molybdophosphate, formed between orthophosphate and molybdate in sulphuric acid solution, is extracted into a mixture of toluene and 4-methylpentan-2-one (1:3 v v ) with Malachite Green as counter-ion. A single extraction with equal phase volumes gives an apparent molar absorptivity for phosphate of 2.3 x 10(5) l.mole(-1).cm(-1) at 630 nm; the absorbance of the reagent blank is 0.03. With an organic to aqueous phase-volume ratio of 1:10, the molar absorptivity is 2.5 x 10(5) l.mole(-1).cm(-1) and the absorbance of the reagent blank 0.08. By the proposed method, ng ml levels of phosphorus can be determined, and the detection limit is about 0.1 ng ml . The standard deviation and relative standard deviation for the determination of phosphorus in tap water (4.3 ng ml ) are 0.05 ng ml and 1.1%, respectively. The method can also be applied to the determination of phosphorus in river water and sea-water.     

Third-order derivative spectrophotometric determination of phosphate as ternary complex with molybdate and rhodamine 6G

This paper describes a third-order derivative Spectrophotometric procedure for the determination of traces of phosphate, based on the formation of a ternary ion-association complex by reaction of phosphate with rhodamine 6G in the presence of molybdate. The pink complex is readily formed in 0.08–0.16M H₂SO₄ medium and remained stable for 2 h. The influence of various instrumental parameters and reaction conditions for maximum colour development are discussed. The few interfering ions can be masked by the addition of appropriate reagents. The procedure is simple, rapid and reliable and allows the determination of 1.5 g l^–1 of phosphate. The relative standard deviation for the determination of 0.08 mg l^–1 of phosphate was 1.1%. The method is applicable to the determination of phosphate in river water, sea water, drinking water, milk powder and standard reference materials.     

Renewable molybdate complexes encapsulated in anion exchange resin for selective and durable removal of phosphate

The existence of many anions in wastewater reduces the removal efficiency of phosphate by adsorbents under realistic conditions. Facing this challenge, the study reports on an insistent and stable composite adsorbent of molybdate complexes Fe-(MoO_x) embedded in a macroporous anion exchange resin (D-201). [Fe(MoO_x)]-D-201 shows 93.7% adsorption capacity (28.3 mg/g) for phosphate even when the molar concentration of coexisting ions is 5 times higher than phosphate. The capacity of adsorbent is maintained more than 84.2% after five regeneration cycles to remove phosphate in the wastewater containing coexisting ions. The ability of highly selective removal of phosphate is maintained during the regeneration cycles explained by the change of the binding of molybdate clusters with phosphate, which is due to the different structures of molybdate clusters depending on various pH. In general, this work puts forward a new idea for the development of phosphorus removal adsorbents for the treatment of wastewater containing coexisting ions.     

Probing phosphate ion via the europium(III)-modulated fluorescence of gold nanoclusters

Fluorescent gold nanoclusters (Au-NCs) were synthesized by a one-pot method using 11-mercaptoundecanoic acid as a reducing and capping reagent. It is found that the red fluorescence of the Au-NCs is quenched by the introduction of Eu(III) at pH 7.0, but that fluorescence is restored on addition of phosphate. The Au-NCs were investigated by transmission electron microscopy and fluorescence photographs. The effect of pH on fluorescence was studied in the range from pH 6 to 10 and is found to be strong. Based on these findings, we have developed an assay for phosphate. Ions such as citrate, Fe(CN)₆ ^3?, SO₄ ^2?, S₂O₈ ^2?, Cl^?, HS^?, Br^?, AcO^?, NO₂ ^?, SCN^?, ClO₄ ^?, HCO₃ ^?, NO₃ ^?, Cd²⁺, Ba²⁺, Zn²⁺, Mg²⁺, and glutamate do not interfere, but ascorbate and Fe³⁺ can quench Au-NCs fluorescence. The fluorescent nanocluster probe responds to phosphate in the range from 0.18 to 250 μM, and the detection limit is 180 nM. The probe also responds to pyrophosphate and ATP. Figure

Off/on fluorescence sensor for phosphate based on Eu³⁺-modulated Au NCs thanks to the competition of oxygen-donor atoms from phosphate with those from the carboxylate groups was developed     

Probing phosphate ion via the europium(III)-modulated fluorescence of gold nanoclusters

Fluorescent gold nanoclusters (Au-NCs) were synthesized by a one-pot method using 11-mercaptoundecanoic acid as a reducing and capping reagent. It is found that the red fluorescence of the Au-NCs is quenched by the introduction of Eu(III) at pH 7.0, but that fluorescence is restored on addition of phosphate. The Au-NCs were investigated by transmission electron microscopy and fluorescence photographs. The effect of pH on fluorescence was studied in the range from pH 6 to 10 and is found to be strong. Based on these findings, we have developed an assay for phosphate. Ions such as citrate, Fe(CN)₆ ³⁻, SO₄ ²⁻, S₂O₈ ²⁻, Cl⁻, HS⁻, Br⁻, AcO⁻, NO₂ ⁻, SCN⁻, ClO₄ ⁻, HCO₃ ⁻, NO₃ ⁻, Cd²⁺, Ba²⁺, Zn²⁺, Mg²⁺, and glutamate do not interfere, but ascorbate and Fe³⁺ can quench Au-NCs fluorescence. The fluorescent nanocluster probe responds to phosphate in the range from 0.18 to 250 μM, and the detection limit is 180 nM. The probe also responds to pyrophosphate and ATP.

Off/on fluorescence sensor for phosphate based on Eu³⁺-modulated Au NCs thanks to the competition of oxygen-donor atoms from phosphate with those from the carboxylate groups was developed

     

Potassium dihydrogen phosphate catalyzed one-pot synthesis of 2,4,5-triaryl-1H-imidazoles

<正>A simple and efficient method has been developed;benzil/benzoin undergoes smooth condensation with various substituted aldehyde and ammonium acetate in the presence of potassium dihydrogen phosphate(KH_2PO_4) under mild reaction conditions to afford the corresponding trisubstituted imidazole in excellent yields.The method for synthesis of product,the reaction mixture was reflux in ethanol for 40-90 min.The present method is simple,efficient,and cost-effective.     

Synergetic transport of europium through a contained supported liquid membrane using trioctylamine and tributyl phosphate as carriers

Contained supported liquid membrane (CSLM) system has been explored for synergic liquid membranes. Different experimental variables such as concentration of acid, carrier, metal ion and complexing agents, stirring speed, etc. have been investigated. Trioctylamine (TOA) + tributyl phosphate (TBP) system has been explored for europium.     

Comparative study of iron(III) phosphate,arsenate, antimonate,selenite, molybdate and tungstate

Six water-insoluble compounds of iron(III) have been synthesized by mixing solutions of ferric nitrate and the acidic oxides of elements of Groups V and VI. These compounds have been characterized on the basis of chemical-analysis, pH titration, thermogravimetry, solid-reflectance, IR and Mössbauer studies. Their chemical, thermal and ion-exchange characteristics have been compared.     

Potassium titanyl phosphate membranes: surface properties and application to ionic solution filtration

The relationship between the surface charge of potassium titanyl phosphate (KTP), studied on powder suspensions, and filtration properties of KTP nanofiltration membranes was studied. An experimental investigation of KTP powder characterization in different electrolytic solutions is presented: electrophoretic measurements show that the colloid particles are negatively charged whatever the solution pH, although they present a point of zero charge about 7.8. The selectivity of the membrane depends on the charge and size of ions. The interactions between the membrane and charged species have to be taken into account to explain the transfer through the membrane. With salts having the same cation, the rejection is higher for divalent anions than for monovalent anions. The best rejection rate is observed for applied pressure lower than 7 bar.     

Dye-coated europium monosulfide

Nanoparticles of EuS were synthesized using europium dithiocarbamate complexes. The resulting nanoparticles were coated with the dye, 1-pyrene carboxylic acid and the resulting material was characterized using X-ray powder diffraction, TEM, and UV-visible spectroscopy. Fluorescence spectroscopy was used to determine the relative energy of the conduction band edge to the excited state energy of the dye.     

Silver magnesium molybdate and silver cobalt molybdate: Synthesis and ionic conductivity

Impedance spectroscopy, X-ray powder diffraction, and electron microscopy are used to study silver magnesium and silver cobalt molybdates of composition Ag₂A ₂ ^II (MoO₄)₃ (A = Mg, Co) and the products of their aliovalent doping by scandium(III) and vanadium(V). The double molybdates have high ionic conductivities at temperatures above 600 K. A partial aliovalent substitution of scandium for magnesium or vanadium for molybdenum increases the ionic conductivity of the molybdates below 473 K. The defect mobility and the enthalpy of defect formation in the Ag₂Mg₂(MoO₄)₃ structure are estimated proceeding from the experimental data.     

Disordered modifications of cobalt molybdate

The structures of recently discovered new high-temperature modifications of cobalt molybdate, a′-and a″-CoMoO₄, were determined. a′-and a″-CoMoO₄ appear after the phase a-CoMoO₄ is heated above the temperature range 700–1000°C. They seem to be the disordered modifications of a-CoMoO₄ with metal atoms distributed at random in an a-CoMoO₄ oxygen network.The F(hkl) values, calculated for variously disordered a-CoMoO₄ structure, were compared with the observed intensities of diffraction lines changing in the course of a → a′ and a → a″ transitions. It was concluded that a″-CoMoO₄₄ has a completely disordered structure with random distribution of both Co and Mo atoms in oxygen interatomic voids. The a′-CoMoO₄ is a partly disordered modification, with random distribution of some cations only.The temperature and the kind of order-disorder transition depend on the method of preparation of a-CoMoO₄ samples.The disordered modifications of cobalt molybdate may be supercooled—even to room temperature—before it transforms rapidly into low-temperature b-CoMoO₄ form.