Multifunctional organic-inorganic multilayer films of tris(2,2 '-bipyridine)ruthenium and decatungstate

A new multifunctional multilayer films consisting of tris(2,2'-bipyridyl)ruthenium(II) (Rubpy) and sodium decatungstate (W-10) have been prepared by the layer-by-layer (LbL) self-assembly method on ITO substrate. X-ray photoelectron spectra (XPS) confirmed the existence of W10 and Rubpy. Cyclic voltammetry (CV) and UV-Vis spectroscopy demonstrated the uniform assembly of (W-10/Rubpy) multilayer films. The multilayer films possess electrocatalytic activities on the reduction of iodate and oxidation of oxalate. Moreover, the films exhibited electrochemiluminescence (ECL) with tripropylamine (abbreviated as TPA) as the coreactant and the ECL response was proportional to the number of (W-10/Rubpy) layers. These characteristics of the multilayer films might find potential applications in the field of sensors and materials fields.

Miniaturized tris(2,2 '-bipyridyl)ruthenium(II) electrochemiluminescence detection cell for capillary electrophoresis and flow injection analysis

The design and performance of a miniaturized chip-type tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)(3)(2+)] electrochemiluminescence (ECL) detection cell suitable for both capillary electrophoresis (CE) and flow injection (FI) analysis are described. The cell was fabricated from two pieces of glass (20 x 15 x 1.7 mm), and the 0.5-mm-diameter platinum disk was used as working electrode held at +1.15 V (vs silver wire quasi-reference), the stainless steel guide tubing as counter electrode, and the silver wire as quasi-reference electrode. The performance traits of the cell in both CE and FI modes were evaluated using tripropylamine, proline, and oxalate and compared favorably to those reported for CE and FI detection cells. The advantages of versatility, sensitivity, and accuracy make the device attractive for the routine analysis of amine-containing species or oxalate by CE and FI with Ru(bPY)(3)(2divided by) ECL detection.

Local structure and valences of samariurn in SrB4O7 : Sm and SrB6O10 : Sm prepared in-air

The coordination numbers for the samarium atoms and the Sm-O bond distances in SrB4O7:Sm and SrB6O10:Sm prepared in air were determined by means of Sm-L-3 edge EXAFS. The coordination. was found to be nine-folded for both these hosts and the bond distance was 2.40-2.42 Angstrom in SrB4O7:Sm and 2.42-2.44 Angstrom in SrB6O10:Sm. For SrB4O7:Sm the coordination number is coincident with that of the strontium. atoms suggesting the substitution of the samarium atoms at the strontium sites. The coordination number of the strontium atoms in SrB6O10 was also suggested to be nine assuming the same type of substitution. The valences of samarium were determined from the luminescent spectra. Both divalent and trivalent ions were present in both SrB4O7:Sm and SrB6O10:Sm, while the fraction of Sm2+ was higher in the former than in the latter. This difference has been assigned to the difference in rigidity between the B-O networks in these structures.

UV-VUV excited luminescence of SrBPO5 : Sm phosphor prepared in air

The high-resolution luminescent spectrum of divalent samarium excited by 355 nm UV light at 77 K, the VUV excitation spectra, the VUV excited emission spectra and EXAFS at Sm-L-3 edge were reported for samarium doped strontium borophosphate, SrBPO5:Sm prepared by solid state reaction in air at high temperature. The high-resolution luminescent spectrum showed that the divalent samarium ions occupied the C-2upsilon lattice sites. The VUV excitation spectra indicated that the sample exhibited absorption bands with the maxima at 129 and 148 nm, respectively. The performance of EXAFS at Sm-L3 absorption edge suggested that the samarium ions were nine-coordinated and the mean distances of bond Sm-O were 2.38 Angstrom.

Preparation of divalent rare earth ions in air by aliovalent substitution and spectroscopic properties of Ln(2+)

When alkaline earth ions in borates, phosphates or borophosphates [SrB4O7, SrB6O10, BaB8O13, MBPO5 (M=Ca,Sr)] are substituted partially and aliovalently by trivalent rare earth ions such as Sm3+, Eu3+, these rare earth ions can be reduced to divalent state by the produced negative charge vacancy V-M". The matrices must have appropriate structure containing a rigid three-dimensional network of tetragonal AO(4) groups (A=B,P). These groups can surround and isolate the produced divalent RE2+ ions from the reaction with oxygen. Therefore, this reduction reaction can be carried out even in air at high temperature. The produced divalent rare earth ions can be detected by luminescence and XANES methods and their spectroscopic properties are discussed.

Studies of perchlorate triggered ion-gate behavior of sBLM by electrochemiluminescence and its application to a sensor for perchlorate

Ru(bpy)(3)(2+) electrochemiluminescence (ECL) method and electrocatalysis method were first used to study the ion-gate behavior of supported lipid bilayer membrane (sBLM). We found that sBLM, made of dimethyldioctadecylammonium bromide (a kind of synthetic lipid), showed ion-gate behavior for the permeation of Ru(bpy)(3)(2+) in the presence of perchlorate anion. There existed a threshold concentration (0.1 muM) of perchlorate anion for ion-gate opening. Below the threshold the ion-gate was closed. Above the threshold, the number of opened ion-gate sites increased with the increase of perchlorate anion concentration and leveled off at concentrations higher than 1200 muM. Based on it, a new sensor for perchlorate was developed. Furthermore, the opening and closing of the ion-gate behavior was reversible, which means the sensor can repeatedly be used.

Electrochemiluminescent microoptoprobe with mini-grid working electrode and self-contained sample container

A new electrochemiluminescence (ECL) microoptoprobe with simple structure. small sampling volume and high efficiency was developed. It was constructed by fixing the transparent gold mini-grid on the end surface of the optical fiber, and by surrounding the fiber with the counter- and reference electrodes to form a self-contained three-electrode system. The use of mini-grid electrode increased the surface area and collection efficiency. which resulted in higher ECL signal and better sensitivity. The counter electrode together with one end of the fiber formed a mini-vessel, which eliminated the need of additional container and allowed to perform ECL detection in a very small volume (about 10 mul). The microoptoprobe obtained was characterized with the Ru(bpy)(3)(2-)-tripropylamine system and was applied for the determination of oxalate and chlorpromazine (CPZ). Detection limits (S/N = 3) were 5 x 10(-7) and 1 x 10(-6) mol l(-1) for oxalate and CPZ. respectively. The linear range for oxalate and CPZ extended from 1 x 10(-6) to 1 x 10(-3) mol l(-1), and from 5 x 10(-6) to 5 x 10(-4) mol l(-1). respectively.

Electrochemiluminescence of dichlorotris (1,10-phenanthroline) ruthenium (II) with peroxydisulfate in purely aqueous solution at carbon paste electrode

The electrochemiluminescence (ECL) of dichlorotris (1,10-phenanthroline) ruthenium (11) [Ru(phen)(3)(2+)] with peroxydisulfate (S2O82-) was first described. The use of carbon paste electrodes, organic solvent modified electrodes, allowed obtaining ECL in purely aqueous solution. The ECL produced by the reaction of electrogenerated C Ru(phen)(3)(2+) with the strongly oxidizing intermediate SO4-., was observed only when the applied potential was negative enough to reduce Ru(phen)(3)(2+). In comparison with Ru(bpy)(3)(2+)/S2O82- ECL, the Ru(phen)(3)(2+)/O-8(2-)/S2O82- ECL was more stable in aqueous solution. It was not affected by the storage of the carbon paste electrodes, and it quenched only at quite high S2O82- concentrations. The ECL intensity was a function of S2O82- concentration, increasing linearly with the S2O82- concentration from 5 X 10(-6) to 2 X 10(-3) mol l(-1), and dropping off sharply at S2O82- concentration higher than 20 mmol l(-1). The proposed ECL method with Ru(phen)(3)(2+) was sensitive and selective for the determination of S2O82-. (C) 2002 Elsevier Science B.V. All rights reserved.

Preparation of borates doped with divalent rare earth ions (RE2+) in air and spectroscopy of divalent rare earth ions (RE2+ = Sm, Eu, Tm, Yb)

The spectroscopic feature of divalent Sm2+, Eu2+, Tm2+ and Yb2+ is discussed in this paper. Especially the spectroscopic properties of some berates containing tetrahedral BO4 group such as SrB4O7, SrB6O10 and BaB8O13 doped with these divalent ions are reported. When the divalent alkaline earth ion in these berates is replaced partially by the above trivalent rare earth ion, the charge carried in the produced defects can be used as reductant to reduce the doped rare earth ion into divalent state at high temperature even in air. Therefore, a convenient and safe method is provided to prepared phosphors doped with these divalent rare earths.

Electrochemiluminescence of tris(2,2 '-bipyridine)ruthenium(II) immobilized in poly(p-styrenesulfonate)-silica-Triton X-100 composite thin-films

The electrochemiluminescence (ECL) of tris(2,2'-bipyridine)ruthenium(ii) [Ru(bpy)(3)(2+)] immobilized in poly(p-styrenesulfonate) (PSS)-silica-Triton X-100 composite films was investigated. The cooperative action of PSS, sol-gel and Triton X-100 attached Ru(bpy)(3)(2+) to the electrode strongly, and the presence of Triton X-100 prevented drying fractures of the sol-gel films during gelation and even on repeated wet-dry cycles. The modified electrode was used for the ECL detection of oxalate, tripropylamine (TPA) and NADH in a flow injection analysis (FIA) system with a newly designed flow cell. The detection scheme exhibited good stability, short response time and high sensitivity. Detection limits were 0.1, 0.1 and 0.5 mu mol L-1 for oxalate, TPA and NADH, respectively, and the linear concentration range extended from 0.001 to 1 mmol L-1 for the three analytes. Applications of the flow cell in ECL and electrochemical detection, as well as the immobilization of reagents based on the cooperative action, are suggested.

Luminescence of RE2+ (RE = Sm, Yb) in barium octoborate

The reduction process from trivalent to divalent state for Sm3+ and Yb3+ ions in barium berates (BaB8O13) prepared in air was observed. The luminescence properties of these divalent rare-earth ions were studied. Yb2+ shows an f-d broad emission band, due to the 4f(14) --> 4f(13)5d transition, while the Sm2+ ion shows an f --> f transition. From the spectra of Yb2+, and using the D-5(0) --> F-7(0) transition of Sm2+ as a structural probe, two crystallographic sites were found to be available for the cations in the host. Vibronic transitions of Sm2+ were observed at low temperature. BaB8O13 was found to be a good host for reducing the trivalent rare-earth ions to divalent state and to exhibit interesting spectroscopic properties,

The reduction of RE3+ in SrB6O10 prepared in air and the luminescence of SrB6O10 : RE2+ (RE=Eu, Sm, Tm)

The reduction of RE3+ to RE2+ (RE=Eu, Sm and Tm) in SrB6O10 prepared in air by high-temperature solid state reaction was observed. The luminescent properties of Eu2+ and Tm2+ show f-d transition and Sm2+ shows f-f transition at room temperature. Three crystallographic sites for Sm2+ in matrix are available. Vibronic transition of D-5(0)-F-7(0) of Sm2+ was studied. The coupled phonon energy about 108 cm(-1), was determined: from the vibronic transition. Due to the thermal population from D-5(0) level, (D1-FJ)-D-5-F-7 (J=0, 1, 2) transitions of Sm2+ were observed at room temperature. A charge compensation mechanism is proposed as a possible explanation.

Effects of heteropoly acids and surfactant on electrochemiluminescence of tris(2,2 '-bipyridine) ruthenium(II)

The effects of heteropoly acids and Triton X-100 on electrochemiluminescence (ECL) of Ru(bpy)(3)(2+) are investigated. Triton X-100 prevents the oxidation of oxalate and results in an increase of the ECL signal. H5SiW11VO40 prevents the direct oxidation of oxalate and makes the electrochemical behavior of Ru(bpy)(3)(2+) less reversible, which leads to a decrease of the ECL signal. In contrast, H3PMo12O40 has negligible effect on ECL intensity. Some possible reasons for the effects on the ECL of Ru(bpy)(3)(2+) are discussed based on the adsorption of SiW11VO405- on electrode surface and the ion association between SiW11VO405- and Ru(bpy)(3)(2+). The signal of ECL decreases linearly with the concentration of heteropoly acid in the range from 2x10-6 to 1x10(-4) mol l(-1). The results indicate that ECL of RU(bpy)(3)(2+) is a potential sensitive and selective detection method for heteropoly acids and hence for the elements comprised in them.

Luminescence properties of Sm2+ in barium octaborates (BaB8O13 : Sm2+)

The luminescence of Sm2+ in BaB8O13 are studied as a function of temperature. At 10 K, several crystallographic sites for Sm2+ ions with inversion symmetry are possible and D-5(0) --> F-7(1) transition show predominant intensities, whereas above 50 K two crystallographic sites without inversion symmetry are clearly observed for Sm2+ in BaB8O13 and the D-5(0) --> F-7(0) transition show strongest intensity. The vibronic transitions and the non-radiative transitions of Sm2+ are studied and a coupled-phonon energy about 50 cm(-1) is obtained. The thermal effects on the line shift, emission intensities, half-width and lifetime of the D-5(0) --> F-7(0) transition are also studied. The decay curves at different temperatures are all in single exponential and are temperature-independent with lifetime around 3.5 ms. (C) 1999 Elsevier Science B.V. All rights reserved.

K-2[MoO3(C2O4)].H2O

In the title compound, catena-poly[dipotassium [[(oxalato-O,O')dioxomolybdate]-mu-oxo]monohydrate], oxalate acts as a bidentate ligand coordinating to each Mo atom through the two deprotonated carboxylate groups. The coordination polyhedron of molybdenum is distorted octahedral and there are infinite chains in the structure. Principal dimensions are: Mo-O(terminal) 1.560 (3) and 1.739 (3) Angstrom, Mo-O(bridging) 2.046 (4) and 2.410 (4) Angstrom, and Mo-O(carboxylate) 1.949 (3) and 2.113 (3) Angstrom.