UV-Vis and surface photovoltage spectra of Fe2O3/polystyrene composite microspheres

Fe2O3 sol with the particle diameter of 3-5 nm was flocculated by the addition of SDS, and the flocculate formed was redispersed by the further addition of that surfactant. Thus the surfactant bilayer was formed on the surface of Fe2O3. The emulsion polymerization of styrene (St) adsolubilized oil the surfactant adsorbed bilayer was carried out by initiator potassium persulfate (KPS). The UV-Vis and surface photovoltage spectra (SPS) indicate that the Fe2O3 particles were encapsulated in polystyrene(PSt) successfully.

Red electroluminescent device with europium 1,1,1-trifluoroacetylacetonate complex as emissive center

By comparing the phosphorescence spectra of Gd(acac)(3) (acac: acetylacetone) and Gd(TFacac)(3) (TFacac: 1, 1, 1-trifluoro-acetylacetone), the effect of fluorine replacing of hydrogen was discussed. It can lower the triplet state energy of acac and make it more suitable to the D-5(1) energy state of europium. Organic electroluminescent (OEL) devices with corresponding europium complexes as emissive layers were fabricated. A triple laver-type device with a structure of glass substrate/indium-tin oxide (ITO)/poly(N-vinylcarbazole) (PVK)/PVK:Eu(TFacac)(3)phen:2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD)/PBD/Al exhibits bright red luminescence upon applying dc voltage, The device has the properties of a diode and the current-bias voltage line was obtained.

Photoelectrochemical reduction of CO2 mediated with methylviologen at roughened silver electrodes

The photoelectrocatalytic effect for the reduction of CO2 mediated with methylviologen (MV) was studied at mercury, polished silver and roughened silver electrodes using electrochemical and surface-enhanced Raman scattering (SERS) techniques. A large photoelectrocatalytic effect for the reduction of CO2 in the presence of MV was observed at the roughened silver electrode, whereas there was only a very small photoelectrocatalytic current at a more negative potential on mercury and polished silver electrodes. The SERS spectra of MV in the presence and absence of CO2, along with the electrochemical results, demonstrate that the surface adsorbed complexes, MV+ -Ag and MV0-Ag, played a role as the mediator for photoinduced electron transfer to CO2 in the solution. The results also suggest that the surface plasmon resonance of the nanoscale silver particle contributes to the overall photoelectrocatalytic effect on a roughened silver electrode.

VUV excited luminescence of europium activated calcium borophosphate prepared in air

XAFS (EXAFS and XANES) at Eu-L-3 edge were used to determine the local structure and the valences of europium in CaBPO5:Eu prepared in air. The results of EXAFS showed that the doped europium atoms were nine-coordinated by oxygen atoms and the distances of bond Eu-O were 2.39 Angstrom in the host lattice. XANES at Eu-L-3 edge exhibited that Eu2+ and Eu3+ coexisted in the matrix. The luminescent spectrum of the material excited by VUV at 147 nm presented a similar spectrum with that excited by f-f transition of Eu2+ at 396 nm and f-d transition of Eu2+ at 312 nm. The broad emission band due to both 4f(6)5d - 4f(7) transition of EU2+ and f - f transition of Eu3+ could be observed in emission spectra, which indicated that the trivalent europium ions were reduced in air in the matrix at high temperature by the defects [V-Cn]" formed by aliovalent substitution between Ca2+ and Eu3+ ions. The UV excitation spectrum showed the typical f-f transition of Eu3+ and f-d transition of Eu2+. The bands with the maxima at about 113 and 158 nm in VUV excitation spectrum were assigned to originate from the absorption of the host lattice.

Sol-gel deposition and luminescent properties of oxyapatite Ca-2(Y,Gd)(8)(SiO4)(6)O-2 phosphor films doped with rare earth and lead ions

Rare-earth and lead ions (Eu3+, Tb3+, Dy3+, Pb2+) doped Ca2Y8 (SiO4)(6)O-2 and Ca2Gd8(SiO4)(6)O-2 thin films have been dip- coated on silicon and quartz glass substrates through the sol- gel route. X- Ray diffraction (XRD), TG- DTA, scanning electron microscopy (SEM), atomic force microscopy (AFM), FT- IR and luminescence excitation and emission spectra as well as luminescence decays were used to characterize the resulting films. The results of XRD reveal that these films remain amorphous below 700 degreesC, begin to crystallize at 800 degreesC and crystallize completely around 1000 degreesC with an oxyapatite structure. The grain structure of the film can be seen clearly from SEM and AFM micrographs, where particles with various shapes and average size of 250 nm can be resolved. Eu3+ and Tb3+ show their characteristic red (D-5(0)-F-7(2)) and green (D-5(4) - F-7(5)) emission in the films with a quenching concentration of 10 and 6 mol% (of Y3+), respectively. The lifetime and emission intensity of Eu3+ increase with the temperature treatment from 700 to 1100 degreesC, while those of Tb3+ show a maximum at 800 degreesC. Energy transfer phenomena have been observed by activating the oxyapatite film host- lattice Ca2Gd8(SiO4)(6)O-2 with Tb3+ (Dy3+). In addition, Pb2+ can sensitize the Gd3+ sublattice in Ca2Gd8(SiO4)(6)O-2.

Study on photochemical fluorescence enhancement of terbium-fleroxacin complex

The sensitized fluorescence intensity of terbium ion can be notably enhanced when the Tb3+-fleroxacin complex is exposed to 365 nm light. By the measurements of fluorescence spectra, phosphorescence spectra, fluorescence quantum yield and fluorescence lifetime of the system, it is proved that irradiation makes the complex undergo a photochemical reaction and produces a new terbium complex which is more favorable to intramolecular energy transfer. The mechanism of the photochemical fluorescence enhancement was discussed.

The VUV spectra properties of (Y,Gd)BO3 : Eu

The (Y, Gd) BO3 : Eu phosphor was synthesized by solid-state reaction, The UV spectra showed that in a certain range of Gd3+ concentration, more Gd3+ absorbed energy and transferred it to Eu3+ with its increasing concentration. From the spectra in VUV region, it was observed that both the doping and the concentrations of Gd3+, Eu3+ greatly affected the absorption of the host lattice. The absorbances at 147 nm and 170 nm increased when the Gd3+ was doped which can be explained as that Gd3+ transferred energy to BO4. The optical properties of (Y, Gd)BO3 : Eu were the best when the concentration of Eu3+ was about 0.04.

Fluorescence analysis of phospholipase A(2) isolated from Chinese agkistrodon blomhoffii Ussurensis venom

The general and synchronous spectra of phospholipase A(2) (PLA(2)) isolated from Chinese agkistrodon blomhoffii Ussurensis snake venom were studied. The chromophores of PLA(2) were mainly contributed by tyrosine and tryptophane residues when the intervals between the excitation wavelength and the emssion waveleagth (Delta lambda) were 20nm and 75nm, respectively. The pH of buffers could change the fluorescence intensities of PLA(2) by changing the charge distribution of its amino acid chain. Ca2+ can not only increase the emission fluorescence intensity of PLA(2) but also improve the reaction rate of PLA(2) with its corresponding substrate DPPC.

Preparation and characterization of luminescent thin films doped with rare earth (Tb3+, Eu3+) complexes derived from a sol-gel process

Sol-gel derived luminescent thin films doped with rare earth (RE) complexes were prepared using an in-situ synthesis method with a two-step hydrolysis process and the luminescence spectra were measured. Fluorescence Lifetime and thermal stability were investigated. The results show that a broad excitation band indicates the formation of RE complexes in the solid thin films. RE ions, which are restrained in a silica matrix, present longer lifetime and higher thermal stability than that in DMF/PVB films containing the corresponding pure complexes. (C) 2000 Elsevier Science B.V. All rights reserved.

XANES at Eu-L-3 edge and valence of europium in SrB4O7 : EU and BaB8O13 : Eu

The luminescent materials SrB4O7:Eu and BaB8O13:Eu were synthesized, and the valence states of europium in the materials were measured by means of XANES at Eu-L-3 edge. It is found that the Ed(3+) and Eu2+ ions are all present in the materials, and more Eu3+ ions can be reduced in SrB4O7:Eu than in BaB8O13:Eu. The excitation and emission spectra of Eu3+ in SrB4O7:Eu and BaB8O13:Eu were determined.

Synthesis, electrochemistry, and photophysics of a novel binuclear polypyridyl Ru ( II ) complex with an 1,8-adipoylamido-bis(1, 10-phenanthroline-5-yl) ligand

The present paper covers the syntheses of 1,8-adipoylamido-bis(1,10-phenanthroline-5-yl)(bphaa) and its binuclear complex {[(bpy)(2)Ru](2)(bphaa)} (PF6)(4), where bpy is 2,2'-bipyridine. The two novel compounds were confirmed by means of elemental analysis, IR, and LD-MS and H-1 NMR, and H-1 NMR spectra were completely assigned in virtue of H-1-H-1 COSY. chemical behavior of the binuclear Ru (I) complex was obtained using cyclic and voltammetry. Its photophysical property was investigated by electronic absorption, excitation and emission spectra.

Stimulated emission in the film of polymer/dye blend

Optically pumped stimulated emission behavior in an organic film was demonstrated in this study. The gain material consists of a laser dye perylene doped into polystyrene (PS) matrix in an appropriate weight ratio. The sample was transversely pumped by the three harmonic output of a mode-locked Nd:YAG laser. The change of the emission spectra showed a clear threshold action and gain narrowing phenomenon when increasing the excitation intensity. Three emission peaks were observed below the excitation threshold, which are locate at 446, 475 and 506 nm, respectively. However, only the gain narrowing peak centered at 475 nm could be detected above the threshold. The spectra narrowing observed results from the amplified spontaneous emission (ASE) in the gain material. (C) 2000 Elsevier Science S.A. All rights reserved.

A comparative study on the electroluminescence properties of some terbium beta-diketonate complexes

By comparing the phosphorescence spectra of Gd(acac)(3) (acac=acetylacetone), Gd(TFacac)3 (TFacac=1,1,1-trifluoroacetylacetone), the effects of fluorine replacement of hydrogen on the triplet state energy of the ligands were revealed. Fluorine can lower the triplet state energy of Hacac and make it more suitable for energy transfer towards the D-5(4) state of terbium. Organic electroluminescent devices (OELDs) with the corresponding trivalent terbium complexes as emissive layers were fabricated. Triple-layer-type devices with a structure of glass substrate/ITO (indium tin oxide)/PVK [poly(N-vinylcarbazole)]/PVK : Tb complex: PBD [2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole]/PBD/Al exhibit bright green luminescence upon applying a dc voltage. The luminance of a device with Tb(TFacac)(3)phen (1,10-phenanthroline) and Tb( TFacac) 3 as emissive layer is higher than that of the corresponding devices with Tb(acac)(3)(phen) and Tb(acac)(3) as emissive layers. The EL device with Tb(TFacac)(3)(phen) as emitter exhibits characteristic emission of Tb3+ ions with a maximum luminance of 58 cd m(-2) at 25 V.

Surface photovoltage spectra and photoelectrochemical properties of semiconductor-sensitized nanostructured TiO2 electrodes

Three kinds of TiO2 nanostructured thin films and their CdS-sensitized films, consisting of different sizes of TiO2 nanoparticles prepared with different methods, have been investigated. The surface photovoltage spectra (SPS) measurements indicate that the density of surface states on TiO2 is likely dependent upon the details of prepared methods. TiO2 particles prepared from basic sol have more surface states than that prepared from acidic sol. When the TiO2 thin films prepared using the TiO2 sols were sensitized by CdS particles, the SPS responses relative to the surface states on TiO2 from 350 to 800 nm were decreased. The photoelectrochemical properties of nanostructured TiO2 electrodes suggest that the fewer the surface states and the smaller the particle sizes of TiO2, the larger the photocurrent response. For CdS sensitized TiO2 thin film electrode, it is shown that the semiconductor sensitization is an efficient way to decrease the influence of surface states on the charge separation, and can improve the intensity of photocurrent response. (C) 2001 Elsevier Science B.V. All rights reserved.