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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
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-(MoOx) embedded in a macroporous anion exchange resin (D-201). [Fe(MoOx)]-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. 相似文献
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)63?, SO42?, S2O82?, 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相似文献
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)63−, SO42−, S2O82−, 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
<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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
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. 相似文献
Impedance spectroscopy, X-ray powder diffraction, and electron microscopy are used to study silver magnesium and silver cobalt molybdates of composition Ag2A2II (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. 相似文献
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. 相似文献