Vacuum Ultraviolet Excited Photoluminescence Properties of Novel Na3Y9O3（BO3）8：Tb^3＋ Phosphor

The novel vacuum ultraviolet （VUV） excited Na3 Y9O3 （BO3）8：Tb^3＋ （NYOB：Tb^3＋） green phosphor is prepared. Strong VUV photoluminescence and high quenching concentration of Tb^3＋ （20 wt%） are observed in NYOB： Tb^3＋ and the strong emission are correlated with the unique layer-type structure of NYOB. All the characteristic 4 f - 5d transitions of Tb^3＋ and the host absorption band in VUV region are identified in the excitation spectrum. Based on the results, the energy levels scheme of Tb^3＋ in NYOB：Tb^3＋ is first established. This newly developed NYOB：Tb^3＋ phosphor shows excellent optical properties when compared with the commercial Zn2SiO4：Mn^2＋ and would be a potential VUV-excited green phosphor.     

Photoluminescence Property of Co3O4 Nanowires

Co3O4 nanowire arrays are fabricated by electrodeposition with following heat-treatment in atmosphere ambient. Photoluminescence is investigated at 295K. In the experiment, when increasing the excitation light wavelength from 260 nm to 360 nm, two kinds of emissions corresponding to the increasing excitation light wavelength are observed. One of them alters the excited emission position, another keeps its emission position. The distinct behaviour of excited emissions related to the increasing excitation wavelength indicates that the mechanism of them must be different. According to the experimental comparison and first-principle calculation, the two kinds of emissions are discussed.     

Preparation and Luminescence Characteristics of Ca3Y2（BO3）4：Eu^3＋ Phosphor

Ca3Y2 （BO3）4：Eu^3＋ phosphor is synthesized by high temperature solid-state reaction method, and the Iuminescence characteristics are investigated. The emission spectrum exhibits two strong red emissions at 613 and 621 nm corresponding to the electric dipole ^5 Do- ^7F2 transition of Eu^3＋ under 365 nm excitation, the reason is that Eu^3＋ substituting for Y^3＋ occupies the non-centrosymmetric position in the crystal structure of Ca3 Y2 （BO3）4. The excitation spectrum for 613 nm indicates that the phosphor can be effectively excited by ultraviolet （UV） （254 nm, 365nm and 400nm） and blue （470nm） light. The effect of Eu^3＋ concentration on the emission intensity of Ca3 Y2 （BO3）4 ：Eu^3＋ phosphor is measured, the result shows that the emission intensities increase with increasing Eu^3＋ concentration, then decrease. The CIE colour coordinates of Ca3Y2 （BO3）4：Eu^3＋ phosphor is （0.639, 0.357） at 15mol% Eu^3＋.     

Photophysical analysis of the organic complex [Eu(C12H8N2)2](NO3)3

We have determined the photophysical properties of [Eu(C₁₂H₈N₂)₂](NO₃)₃, (EuPhen), a complex which is very promising for photonic and optoelectronic applications, because of its easy synthetic procedure and high thermal stability (up to 300 °C) combined with large sensitization efficiency and good emission quantum yield. Available experimental absorption and emission data have been analyzed by using Judd-Ofelt analysis. Moreover, semi-empirical calculations have been used to determine the structure of the complex and to interpret the convoluted shape of the absorption spectrum.     

Concentration and Temperature Dependences of YBO3：Bi^3＋ Luminescence under Vacuum Ultraviolet Excitation

Bi^3＋ doped YB03 phosphors are prepared by solid state reaction and their luminescent properties are investi- gated by using synchrotron radiation instrument, Concentration and temperature dependences of YBO3：Bi3＋ luminescence under VUV/UV excitation is observed, The emission and excitation spectra are assigned, and the mechanism for these phenomena is explored, which result from the energy transfer between Bi^3＋ ions occupying different sites in YB03 crystal lattice.     

Photoluminescence Characterization of Silicon Nanoparticles Hybridized Europium Complex

A europium complex Eu (DBM)3 TPPO (Eu tris(benzoylmethide)-(triphenylphosphine oxide)) and silicon nanoparticles have been hybridized.The hybridization can evidently change the photoluminescence (PL) characteristics of the Eu complex in the following aspects:under an excitation of 390nm,the intensity of the PL peak at 611nm due to the ^5Du-^7F2 transition of the Eu^3 ions has been increased by 30%,and thc integrated PL intensity in the visible range has been increased by nearly 3 times;the PL excitation efficiency beyond 440nm has been improved cvidently;the peak in the PL excitation spectrum shifts from 408nm to 388nm,and the PL decay time decreases from 2.07 to 0.96μs,The experimental results indicatde that in the PL process,the photoexcited energy may transfer from the silicon nanoparticlcs to the Eu^3 ions.     

Broadband Infrared Luminescence from Bismuth-Doped GeS2--Ga2S3 Chalcogenide Glasses

Near-infrared luminescence is observed from bismuth-doped GeS2-Ga2Sa chalcogenide glasses excited by an 808 nm laser diode. The emission peak with a maximum at about 1260 nm is observed in 80GeS2-2OGa2 Sa：O.fBi glass and it shifts toward the long wavelength with the addition of Bi gradually. The full width of half maximum （FWHM） is about 200 nm. The broadband infrared luminescence of Bi-doped GeS2-Ga2Sa chalcogenide glasses may be predominantly originated from the low valence state of Bi, such as Bi＋. Raman scattering is also conducted to claxify the structure of glasses. These Bi-doped GeS2 Ga2Sa chalcogenide glasses can be applied potentially in novel broadband optical fibre amplifiers and broadly tunable laser in optical communication system.     

VUV/UV/X-Ray Excited Luminescent Properties of Eu^3＋ and Pr^3＋ Doped BiSbO4

Absorption spectra of BiSbO4 are studied. The electronic structure calculated by the DFT shows that BiSbO4 is a semiconductor, with direct band gap 2.96 eV, which is consistent with UV-visible diffuse reflectance experiment. The host lattice emission band is located at 440 nm under VUV excitation. Eu^3＋ and Pr^3＋ doped samples have high luminescence efficiency in emitting red and green light, respectively. From the partial density of states, Eu^3＋ doped emitting spectrum, and the host crystal structure parameters, the relationship between structure and optical properties is discussed. It is found that the Eu^3＋ ions occupied Bi^3＋ sites, and there could be an energy transfer from Bi^3＋ ions to RE^3＋ ions.     

Luminescent Characteristics of LiSrBO3：Eu3＋ Phosphor for White Light Emitting Diode

LiSrBO3 ：Eu3＋ phosphor is synthesized by a high solid-state reaction method, and its luminescent characteristics are investigated. The emission and excitation spectra of LiSrBO3：Eu3＋ phosphors exhibit that the phosphors can be effectively excited by near ultraviolet （401 nm） and blue （471 nm） light, and emit 615nm red light. The effect of Eua＋ concentration on the emission spectrum of LiSrBO3：Eu3＋ phosphor is studied; the results show that the emission intensity increases with increasing Eu3＋ concentration, and then decreases because of concentration quenching. It reaches the maximum at 3mol%, and the concentration self-quenching mechanism is the dipoledipole interaction according to the Dexter theory. Under the conditions of charge compensation Li＋, Na＋ or K＋ incorporated in LiSrBO3, the luminescent intensities of LiSrBO3 ：Eua＋ phosphor are enhanced.     

Spectral Hole-Burning of Eu^3＋：Y2SiO5 Crystal at 16 K

By using an Ar^＋ ion laser, a tunable Rh 6G dye laser （linewidth 0.5cm^-1） pumped by the second harmonic of a YAG：Nd laser and a Coherent 899-21 dye laser as light sources and using a monochromator, a phase-locking amplifier and a computer as the data detecting system, we detect the optical properties of Eu^3＋-doped Y2SiO5 crystal. Persistent ,spectral hole burning （PSHB） are observed in the Eu^3＋ ions spectral lines （^5 Do-T Fo transition） in the crystal at the temperature of 16K. For 15mW dye laser burning the crystal for 0.1 s spectral holes with hole width about 80 MHz both at 579.62nm and at 579.82nm are detected and the holes can remain for a long time, more than 10h.     

Broadband and High Efficient 1530 nm Emission from Oxyfluoride Glass Ceramics Codoped with Er3＋ and Yb3＋ Ions

The emission at 1530nm and its applications in optical communications are discussed. The efficient width of the emission band △eff, which is up to 91 nm, is larger as compared with silica-based glass, bismuth glass and ZrF4-BaF2-LaFa-AIF3-NaF （ZBLAN） glass doped by Er^3＋ ions. Under the excitation of 785 nm laser, the emission integral intensity of 153Onto increases about five times in the glass ceramics higher than that in the glass. This is explained by the quantum cutting process by two-photon emission with phonon assistance. The results indicate that the glass ceramics are a promising candidate for developing broadband optical amplifiers in wavelength-division multiplexed systems.     

Electroluminescence of Si Nanocrystal-Doped SiO2

We perform a comparative st udy on the electroluminescence （EL） and photoluminescence （PL） of Si nanocrystaldoped SiO2 （nc-Si：SiO2） and SiO2, and clarify whether the contribution from Si nanocrystals in the EL of nc-Si：SiO2 truly exists. The results unambiguously indicate the presence of EL of Si nanocrystals. The difference of peak positions between the EL and PL spectra are discussed. It is found that the normal method of passivation to enhance the PL of Si nanocrystals is not equally effective for the EL, hence new methods need to be explored to promote the EL of Si nanocrystals.[第一段]     

Space-Selective Precipitation of Ba2TiSi2O8 Crystals in Sm3^＋-Doped BaO-TiO2-SiO2 Glass by Femtosecond Laser Irradiation

The ferroelectric crystal Ba2TiSi2O8 with high second-order optical nonlinearity is precipitated in Sm^3＋-doped BaO-TiO2-SiO2 glass by a focused 800hm, 250 kHz and 150fs femtosecond laser irradiation. No apparent blue and red emissions are observed at the beginning, while strong blue emission due to second harmonic generation and red emission due to the f-f transitions of Sm^3＋ are observed near the focal point of the laser beam after irradiation for 25s. Micro-Raman spectra confirm that Ba2 TiSi2O8 crystalline dots and lines are formed after laser irradiation. The mechanism of the phenomenon is discussed.     

Optical properties of Eu(fod)3-doped polymers using supercritical carbon dioxide

X-ray diffraction pattern of solvated Eu(fod)₃(H₂O)_1,5(i-PrOH)_0,5 form of Eu(fod)₃ complex (fod=6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate) is presented. The photoluminescence (PL) spectra of Eu³⁺ ions in polycrystalline powder Eu(fod)₃ and also in Eu(fod)₃-doped polymethylmethacrylate (PMMA), polypropylene (PP) and polydimethylsiloxane (PDMS) were investigated. It is revealed that the matrix influences the temperature quenching of PL intensity in the range 20-100 °C. A polycrystalline powder Eu(fod)₃ and Eu(fod)₃-doped PP are the most effective materials for PL quenching. It is shown that water molecules in the first coordinating sphere of Eu³⁺ ions increase PL intensity temperature quenching.     

Effect of Al^3＋ on Photoluminescence Properties of Eu^3＋-Doped BaZr（BO3）2 Phosphors

We discuss the influence of Al^3＋ on the charge transfer state （CTS） and the photoluminescence properties of BaZr（BO3）2：Eu. The results reveal that there is a red shift which is about 20nm for the charge transfer state when doping with Al^3＋ and indicate the formation of ‘free＇ electrons due to the change of microstructures. In addition, the influence or Al^3＋ doping on the PPR is analysed and a new explanation is raised based on the photo luminescent mechanism. It is the CTS intensity rather than the CTS energy that influences the peak-peak ratio.     

Optical Transmittance and Band Gap of Ferroelectric BaTi2O5 Bulk Glass

Optical transmittance and reflectance on ferroelectric BaTi₂O₅ glasses prepared recently by a containerless synthesis technique are measured at room temperature in the wavelength range 190-800nm. The fundamental absorption edge located around 340nm demonstrates the colourless and transparent character of the glass. The optical band gap of 3.32eV has been estimated. The tail of the optical absorption near the fundamental absorption edge is found to follow the Urbach rule. Our analysis of the experimental spectra supports an indirect allowed interband transition between the valence band formed by O-2p orbitals and the conduction band formed by Ti-3d orbitals.     

Luminescence and Energy Transfer of Eu^2＋, Mn^2＋ in SrZnP2O7

The SrZnP2OT：Eu^2＋, Mn^2＋ phosphor is synthesized by high temperature solid state reaction. The luminescence properties and the energy transfer between Eu^2＋ and Mn^2＋ are investigated. The emission bands of this phosphor peaked at 42Ohm and 67Ohm are originated from the 5d → 4f transition of Eu^2＋ and from the 4T1 （4G） --〉 6A1 （6S） transit/on of Mn^2＋, respectively. With the increasing Mn^2＋ concentration, the intensity of fixed concentra- tion Eu^2＋ decreases and the intensity of Mn^2＋ also increases. It is suggested that there is an energy transfer from Eu^2＋ to Mn^2＋ in SrZnP2O7 host. According to Dexter＇s energy transfer formula of multipolar interaction, the energy transfer between Eu^2＋ and Mn^2＋ is due to the electric dipole-quadrupole interaction of the resonance transfer.     

Hydrogen Passivation Effect on Enhanced Luminescence from Nanocrystalline Si/SiO2 Multilayers

Nanocrystalline Si/SiO2 multilayers are prepared by thermally annealing amorphous Si/SiO2 stacked structures. The photoluminescence intensity is obviously enhanced after hydrogen passivation at various temperatures. It is suggested that the hydrogen trapping and detrapping processes at different temperatures strongly influence the passivation effect. Direct experimental evidence is given by electron spin resonance spectra that hydrogen effectively reduces the nonradiative defect states existing in the Si nanocrystas/SiO2 system which enhances the radiative recombination probability. The luminescence characteristic shows its stability after hydrogen passivation even after aging eight months.     

Correlation between Light Emissions from Amorphous-Si：H/SiO2 and nc-Si/SiO2 Multilayers

We investigate the properties of light emission from amorphous-Si：H/SiO2 and nc-Si/SiO2 multilayers （MLs）. The size dependence of light emission is well exhibited when the a-Si：H sublayer thickness is thinner than 4 nm and the interface states are well passlvated by hydrogen. For the nc-Si/Si02 MLs, the oxygen modified interface states and nanocrystalline silicon play a predominant role in the properties of light emission. It is found that the light emission from nc-Si/SiO2 is in agreement with the model of interface state combining with quantum confinement when the size of nc-Si is smaller than 4 nm. The role of hydrogen and oxygen is discussed in detail.     

Upconversion Luminescence of Er3+ Ions in Transparent Germanate Glass Ceramics Containing CaF2 Nanocrystals

The visible upconversion and near-infrared luminescence of Er3＋ ions in germanate glass ceramics containing GaF2 nanocrystals are investigated. The nanocrystals are characterized by x-ray diffraction （XRD） and transmission electron microscopy, showing their mean sizes less than 20hm. High transmittance of the glass ceramics is displayed by absorption spectra. The upconversion luminescence intensity in the glass ceramics increases significantly with increasing temperature. Both the shifts of the XRD peaks and the Stark-split shown in the luminescence spectra indicate the entrance of the Er3＋ ions into the CaF2 nanocrystals, which is confirmed by a Judd-Ofelt analysis. Possible mechanisms of the upconversion luminescence are analyzed.