Studies on the synergistic extraction of rare earths with a combination of 2-ethylhexylphosphonic mono-2-ethylhexyl ester and trialkylphosphine oxide

The synergistic extraction of rare earths (La, Nd, Gd, Y and Yb) with a mixture of 2-ethylhexyl 2-ethylhexylphosphonate (EHEHPA) (HA) and trialkylphosphine oxide (Cyanex 923) (B) from a hydrochloride medium was investigated. The mixed system significantly enhances the extraction efficiency for lighter lanthanides and the synergistic enhancement coefficients for La (4.52), Nd (3.35), Gd (2.08), Y (1.31) and Yb (1.08) decrease with decreasing ionic radius of the rare earths. The extraction equilibrium of La, Nd and Gd indicate that La and Nd were extracted as MA(3)(.)B, whereas Gd was extracted as Gd(OH)A(2)(HA)(2)B-.. The equilibrium constants, thermodynamic functions such as Delta G, Delta H and Delta S and formation constants of the extracted species were determined. The stripping properties were also studied.

A new oxide ion conductor: La3GaMo2O12

A new oxide ion conductor, La3GaMo2O12, with a bulk conductivity of 2.7 X 10(-2) S.cm(-1) at 800 degrees C in air atmosphere was prepared by the traditional solid-state reaction. The room temperature X-ray diffraction data could be indexed on a monoclinic cell with lattice parameters of a=0.5602(2) nm, b=0.3224(1) nm, c= 1.5741(1) nm, beta= 102.555(0)degrees, V=0.2775(2) nm(3) and space group Pc(7). Ac impedance measurements in various atmospheres further support that it is an oxide ion conductor. This material was stable in various atmospheres with oxygen partial pressure P(O-2) ranging from 1.0 X 10(5) to 1.0 X 10(-7) Pa at 800 degrees C. A reversible polymorphic phase transition occurred at elevated temperatures as confirmed by the differential thermal analysis and dilatometric measurement.

Dependence of performance of organic light-emitting devices on sheet resistance of indium-tin-oxide anodes

The dependence of the performance of organic light-emitting devices(OLEDs) on the sheet resistance of indium-tin-oxide(ITO) anodes was investigated by measuring the steady state current density brightness voltage characteristics and the electroluminescent spectra. The device with a higher sheet resistance anode shows a lower current density, a lower brightness level, and a higher operation voltage. The electroluminescence(EL) efficiencies of the devices with the same structure but different ITO anodes show more complicated differences. Furthermore, the shift of the light-emitting zone toward the anode was found when an anode with a higher sheet resistance was used. These performance differences are discussed and attributed to the reduction of hole injection and the increase in voltage drop over ITO anode with the increase in sheet resistance.

Sol-gel-derived titanium oxide/copolymer composite based glucose biosensor

A new type of sol-gel-derived titanium oxide/copolymer composite material was developed and used for the construction of glucose biosensor. The composite material merged the best properties of the inorganic species, titanium oxide and the organic copolymer, poly(vinyl alcohol) grafting 4-vinylpyridine (PVA-g-PVP). The glucose oxidase entrapped in the composite matrix retained its bioactivity. Morphologies of the composite-modified electrode and the enzyme electrode were characterized with a scanning electron microscope. The dependence of the current responses on enzyme-loading and pH was studied. The response time of the biosensor was < 20 s and the linear range was up to 9 mM with a sensitivity of 405 nA/mM. The biosensor was stable for at least I month. In addition, the tetrathiafulvalene-mediated enzyme electrode was constructed for the decrease of detection potential and the effect of three common physiological sources that might interfere was also investigated.

Liquid-liquid phase behavior of toluene/polyethylene oxide/poly(ethyleneoxide-b-dimethylsiloxane) polymer-containing ternary mixtures

The experimental data of phase diagrams for both polyethylene oxide/poly(ethylene oxide-b-dimethylsiloxane) binary and toluene/polyethylene oxide/poly(ethylene oxide-b-dimethylsiloxane) ternary polymer-containing systems was obtained at atmosphere pressure by light scattering method. The critical points for some pre-selected compositions and the pressure effect on the phase transition behavior of ternary system were investigated by turbidity measurements. The chosen system is a mixture of ternary which is one of the very few abnormal polymer-containing systems exhibiting pressure-induced both miscibility and immiscibility. This unusual behavior is related to the toluene concentration in the mixtures. The effect of toluene on the phase transition behavior of the ternary polymer-containing mixture was traced. Such behavior can make it possible to process composite materials from incompatible polymers.

Microchip capillary electrophoresis with an integrated indium tin oxide electrode-based electrochemiluminescence detector

This paper describes an indium tin oxide (ITO) electrode-based Ru(bPY)(3)(2+) electrochemiluminecence (ECL) detector for a microchip capillary electrophoresis (CE). The microchip CE-ECL system described in this article consists of a poly(dimethylsiloxane) (PDMS) layer containing separation and injection channels and an electrode plate with an ITO electrode fabricated by a photolithographic method. The PDMS layer was reversibly bound to the ITO electrode plate, which greatly simplified the alignment of the separation channel with the working electrode and enhanced the photon-capturing efficiency. In our study, the high separation electric field had no significant influence on the ECL detector, and decouplers for isolating the separation electric field were not needed in the microchip CE-ECL system. The ITO electrodes employed in the experiments displayed good durability and stability in the analytical procedures. Proline was selected to perform the microchip device with a limit of detection of 1.2 muM (S/N = 3) and a linear range from 5 to 600 muM.

Coating carbon nanotubes with europium oxide

Carbon nanotubes (CNTS) coating with europium oxide by a simple method is reported in this letter for the first time. The CNTS were refluxed in a solution of nitric acid containing europium nitrate, and the pH value was subsequently ajusted with ammonia solution. At last, the mixture was filtered and annealed. The TEM micrograph showed that the CNTS were covered with a uniform thin layer with thickness of about 15 nm. The XRD results revealed that the CNTS were coated with europium oxide.

Copolymerization of CO2 and propylene oxide under rare earth ternary catalyst: design of ligand in yttrium complex

Copolymerization of carbon dioxide and propylene oxide was carried out employing (RC6H4COO)(3)Y/glycerin/ZnEt2 (R = -H, -CH3, NO2, -OH) ternary catalyst systems. The feature of yttrium carboxylates (ligand, substituent and its position on the aromatic ring) is of great importance in the final copolymerization. Appropriate design of substituent and position of the ligand in benzoate-based yttrium complex can adjust the microstructure of aliphatic polycarbonate in a moderate degree, where the head-to-tail linkage in the copolymer is adjustable from 68.4 to 75.4%. The steric factor of the ligand in the yttrium complex is crucial for the molecular weight distribution of the copolymer, probably due to the fact that the substituent at 2 and 4-position would disturb the coordination or insertion of the monomer, lead the copolymer with broad molecular distribution. Based on the study of ultraviolet-visible spectra of the ternary catalyst in various solvents, it seems that the absorption band at 240-255 nm be closely related to the active species of the rare earth ternary catalysts.

Copolymerization of carbon dioxide and propylene oxide with neodymium trichloroacetate-based coordination catalyst

The copolymerizations of carbon dioxide (CO2) and propylene oxide (PO) were performed using new ternary rare-earth catalyst, It was found that the rare-earth coordination catalyst consisting of Nd(CCl3COO)(3), ZnEt2 and glycerine was very effective for the copolymerization of PO with CO2. The effects of the relative molar ratio and addition order of the catalyst components, copolymerization reaction time, and operating pressure as well as temperature on the copolymerization were systematically investigated. At an appropriate combination of all variables, the yield could be as high as 6875 g/mol Nd per hour at 90 degreesC in a 8 h reaction period.

Thermal degradation kinetics of poly(propylene carbonate) obtained from the copolymerization of carbon dioxide and propylene oxide

The kinetics of the thermal degradation of poly(propylene carbonate) (PPC) were investigated with different kinetic methods with data from thermogravimetric analysis under dynamic conditions. The apparent activation energies obtained with different integral methods (Ozawa-Flynn-Wall and Coats-Redfern) were consistent with the values obtained with the Kinssinger method (99.93 kJ/mol). The solid-state decomposition process was a sigmoidal A(3) type in terms of the Coats-Redfern and Phadnis-Deshpande results. The influence of the heating rate on the thermal decomposition temperature was also studied. The derivative thermogravimetry curves of PPC confirmed only one weight-loss step.

Low temperature preparation of ceria solid solutions doubly doped with rare-earth and alkali-earth and their properties as solid oxide fuel cells

A series of solid electrolytes, (Ce(0.8)Ln(0.2))(1 - x)MxO2 - delta(Ln = La, Nd, Sm, Gd, M:Alkali-earth), were prepared by amorphous citrate gel method. XRD patterns indicate that a pure fluorite phase is formed at 800 degreesC. The electrical conductivity and the AC impedance spectra were measured. XPS spectra show that the oxygen vacancies increase owing to the MO doping, which results in the increase of the oxygen ionic transport number and conductivity. The performance of ceria-based solid electrolyte is improved. The effects of rare-earth and alkali-earth ions on the electricity were discussed. The open-circuit voltages and maximum power density of planar solid oxide fuel cell using (Ce0.8Sm0.2)(1 - 0.05)Ca0.05O2 - delta as electrolyte are 0.86 V and 33 mW . cm(-2), respectively.