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Sample records for gap photoluminescence properties

  1. Impact of ion-implantation-induced band gap engineering on the temperature-dependent photoluminescence properties of InAs/InP quantum dashes

    SciTech Connect

    Hadj Alouane, M. H.; Ilahi, B.; Maaref, H.; Salem, B.; Aimez, V.; Morris, D.; Turala, A.; Regreny, P.; Gendry, M.

    2010-07-15

    We report on the effects of the As/P intermixing induced by phosphorus ion implantation in InAs/InP quantum dashes (QDas) on their photoluminescence (PL) properties. For nonintermixed QDas, usual temperature-dependent PL properties characterized by a monotonic redshift in the emission band and a continual broadening of the PL linewidth as the temperature increases, are observed. For intermediate ion implantation doses, the inhomogeneous intermixing enhances the QDas size dispersion and the enlarged distribution of carrier confining potential depths strongly affects the temperature-dependent PL properties below 180 K. An important redshift in the PL emission band occurs between 10 and 180 K which is explained by a redistribution of carriers among the different intermixed QDas of the ensemble. For higher implantation doses, the homogeneous intermixing reduces the broadening of the localized QDas state distribution and the measured linewidth temperature behavior matches that of the nonintermixed QDas. An anomalous temperature-dependent emission energy behavior has been observed for extremely high implantation doses, which is interpreted by a possible QDas dissolution.

  2. Degenerate electrical conductive and excitonic photoluminescence properties of epitaxial films of wide gap p-type layered oxychalcogenides, LnCuOCh (Ln=La, Pr and Nd; Ch=S or Se)

    NASA Astrophysics Data System (ADS)

    Hiramatsu, H.; Ueda, K.; Takafuji, K.; Ohta, H.; Hirano, M.; Kamiya, T.; Hosono, H.

    Electrical and photoluminescence properties were investigated for epitaxial films of layered oxychalcogenides, LnCuOCh (Ln=La, Pr, and Nd, Ch=S or Se). Epitaxial films of Mg 10 at.% doped LaCuOS1-xSex are the first demonstration of degenerate conduction with high hole concentration >1020 cm-3 in wide gap p-type semiconductors. Ion substitution varied the excitonic emission energy from 3.21 eV to 2.89 eV while lanthanide and chalcogenide ion substitutions displayed the opposite tendency against cell volume. These unique properties are discussed with respect to the electronic structure originating from the layered crystal structure.

  3. Photoluminescence through in-gap states in phenylacetylene functionalized silicon nanocrystals

    NASA Astrophysics Data System (ADS)

    Angı, Arzu; Sinelnikov, Regina; Meldrum, Al; Veinot, Jonathan G. C.; Balberg, Isacc; Azulay, Doron; Millo, Oded; Rieger, Bernhard

    2016-04-01

    Optoelectronic properties of Si nanocrystals (SiNCs) were studied by combining scanning tunneling spectroscopy (STS) and optical measurements. The photoluminescence (PL) of phenylacetylene functionalized SiNCs red shifts relative to hexyl- and phenyl-capped counterparts, whereas the absorption spectra and the band gaps extracted from STS are similar for all surface groups. However, an in-gap state near the conduction band edge was detected by STS only for the phenylacetylene terminated SiNCs, which can account for the PL shift via relaxation across this state.Optoelectronic properties of Si nanocrystals (SiNCs) were studied by combining scanning tunneling spectroscopy (STS) and optical measurements. The photoluminescence (PL) of phenylacetylene functionalized SiNCs red shifts relative to hexyl- and phenyl-capped counterparts, whereas the absorption spectra and the band gaps extracted from STS are similar for all surface groups. However, an in-gap state near the conduction band edge was detected by STS only for the phenylacetylene terminated SiNCs, which can account for the PL shift via relaxation across this state. Electronic supplementary information (ESI) available: Detailed experimental procedures, additional HR-TEM images and PL lifetime data. See DOI: 10.1039/c6nr01435f

  4. HAC: Band Gap, Photoluminescence, and Optical/Near-Infrared Absorption

    NASA Technical Reports Server (NTRS)

    Witt, Adolf N.; Ryutov, Dimitri; Furton, Douglas G.

    1996-01-01

    We report results of laboratory measurements which illustrate the wide range of physical properties found among hydrogenated amorphous carbon (HAC) solids. Within this range, HAC can match quantitatively the astronomical phenomena ascribed to carbonaceous coatings on interstellar grains. We find the optical band gap of HAC to be well correlated with other physical properties of HAC of astronomical interest, and conclude that interstellar HAC must be fairly hydrogen-rich with a band gap of E(sub g) is approx. greater than 2.0 eV.

  5. High Photoluminescence Quantum Yield in Band Gap Tunable Bromide Containing Mixed Halide Perovskites.

    PubMed

    Sutter-Fella, Carolin M; Li, Yanbo; Amani, Matin; Ager, Joel W; Toma, Francesca M; Yablonovitch, Eli; Sharp, Ian D; Javey, Ali

    2016-01-13

    Hybrid organic-inorganic halide perovskite based semiconductor materials are attractive for use in a wide range of optoelectronic devices because they combine the advantages of suitable optoelectronic attributes and simultaneously low-cost solution processability. Here, we present a two-step low-pressure vapor-assisted solution process to grow high quality homogeneous CH3NH3PbI3-xBrx perovskite films over the full band gap range of 1.6-2.3 eV. Photoluminescence light-in versus light-out characterization techniques are used to provide new insights into the optoelectronic properties of Br-containing hybrid organic-inorganic perovskites as a function of optical carrier injection by employing pump-powers over a 6 orders of magnitude dynamic range. The internal luminescence quantum yield of wide band gap perovskites reaches impressive values up to 30%. This high quantum yield translates into substantial quasi-Fermi level splitting and high "luminescence or optically implied" open-circuit voltage. Most importantly, both attributes, high internal quantum yield and high optically implied open-circuit voltage, are demonstrated over the entire band gap range (1.6 eV ≤ Eg ≤ 2.3 eV). These results establish the versatility of Br-containing perovskite semiconductors for a variety of applications and especially for the use as high-quality top cell in tandem photovoltaic devices in combination with industry dominant Si bottom cells. PMID:26691065

  6. Photoluminescence properties and exciton dynamics in monolayer WSe2

    NASA Astrophysics Data System (ADS)

    Yan, Tengfei; Qiao, Xiaofen; Liu, Xiaona; Tan, Pingheng; Zhang, Xinhui

    2014-09-01

    In this work, comprehensive temperature and excitation power dependent photoluminescence and time-resolved photoluminescence studies are carried out on monolayer WSe2 to reveal its properties of exciton emissions and related excitonic dynamics. Competitions between the localized and delocalized exciton emissions, as well as the exciton and trion emissions are observed, respectively. These competitions are suggested to be responsible for the abnormal temperature and excitation intensity dependent photoluminescence properties. The radiative lifetimes of both excitons and trions exhibit linear dependence on temperature within the temperature regime below 260 K, providing further evidence for two-dimensional nature of monolayer material.

  7. Synthesis, photoluminescence and magnetic properties of barium vanadate nanoflowers

    SciTech Connect

    Xu, Jing; Hu, Chenguo; Xi, Yi; Peng, Chen; Wan, Buyong; He, Xiaoshan

    2011-06-15

    Graphical abstract: The flower-shaped barium vanadate was obtained for the first time. The photoluminescence and magnetic properties of the barium vanadate nanoflowers were investigated at room temperature. Research highlights: {yields} In the paper, the flower-shaped barium vanadate were obtained for the first time. The CHM method used here is new and simple for preparation of barium vanadate. {yields} The photoluminescence and magnetic properties of the barium vanadate nanoflowers were investigated at room temperature. The strong bluish-green emission was observed. {yields} The ferromagnetic behavior of the barium vanadate nanoflowers was found with saturation magnetization of about 83.50 x 10{sup -3} emu/g, coercivity of 18.89 Oe and remnant magnetization of 4.63 x 10{sup -3} emu/g. {yields} The mechanisms of PL and magnetic property of barium vanadate nanoflowers have been discussed. -- Abstract: The flower-shaped barium vanadate has been obtained by the composite hydroxide mediated (CHM) method from V{sub 2}O{sub 5} and BaCl{sub 2} at 200 {sup o}C for 13 h. XRD and XPS spectrum of the as-synthesized sample indicate it is hexagonal Ba{sub 3}V{sub 2}O{sub 8} with small amount of Ba{sub 3}VO{sub 4.8} coexistence. Scan electron microscope and transmission electron microscope display that the flower-shaped crystals are composed of nanosheets with thickness of {approx}20 nm. The UV-visible spectrum shows that the barium vanadate sample has two optical gaps (3.85 eV and 3.12 eV). Photoluminescence spectrum of the barium vanadate flowers exhibits a visible light emission centered at 492 and 525 nm which might be attributed to VO{sub 4} tetrahedron with T{sub d} symmetry in Ba{sub 3}V{sub 2}O{sub 8}. The ferromagnetic behavior of the barium vanadate nanoflowers has been found with saturation magnetization of about 83.50 x 10{sup -3} emu/g, coercivity of 18.89 Oe and remnant magnetization of 4.63 x 10{sup -3} emu/g, which is mainly due to the presence of a non

  8. High resolution 4.2 K near band-gap photoluminescence spectrum of mercuric iodide

    NASA Astrophysics Data System (ADS)

    Bao, X. J.; Schlesinger, T. E.; James, R. B.; Ortale, C.; van den Berg, L.

    1990-09-01

    We have investigated in detail (resolution up to 0.35 Å) the near-band-gap 4.2 K photoluminescence spectrum of undoped Hgl2 in its red tetragonal form. At least 26 emission lines are resolved in the wavelength region between 5290 and 5400 Å. Many of these are reported for the first time. We have also tabulated the steplike emission lines between 5220 and 5290 Å.

  9. HgI2 near-band-gap photoluminescence structure and its relationship to nuclear detector quality

    NASA Astrophysics Data System (ADS)

    Wong, D.; Schlesinger, T. E.; James, R. B.; Ortale, C.; van den Berg, L.; Schnepple, W. F.

    1988-08-01

    The low-temperature photoluminescence spectra of several mercuric iodide detectors and off-stoichiometric bulk material have been characterized. Phonon energies have been determined with Raman spectroscopy over a range of temperatures. In earlier work some of the near-band-gap photoluminescence features were identified as phonon replicas. After careful examination of Raman and photoluminescence data, we find that one or perhaps more of these features is probably due to shallow electronic levels related to native defects. Suggestions as to the relationship between photoluminescence peaks and detector quality are made.

  10. Preparation and photoluminescence properties of porous silicon

    NASA Astrophysics Data System (ADS)

    Chen, Zhiwei; Xu, Zhimou

    2009-08-01

    There are many preparation methods of porous silicon(PS), such as electrochemical etching(ECE), photochemical etching, chemical etching and so on. ECE, also known as anodic etching, is more common among these methods. A lot of holes are given priority to be etched on the surface of silicon. The top and vertical aspects of the holes are easily etched while horizontal aspects wall of the holes are quiet different, and then tree-like or sponge-like porous structure is formed. In this paper, we obtained porous structure on the surface of silicon using lithography and dry etching method. The diameter of the hole was 2μm or 6μm. The etching depth of the samples was about 70nm, 140nm and 260nm. Photoluminescence (PL) phenomenon was observed by using light of 270nm, 280nm, 330nm, 455nm and 460nm wavelength to excite the samples. The results showed that PL intensity was the best when excitation wavelength was 270nm or 280nm, compared with 330nm, 455nm and 460nm. From PL analysis of all samples, It exists three emission peaks about at 372nm, 425nm and 473nm. When the diameter of the PS was the same, it was found that PS with etching depth at 140nm was more efficient. It means that PL intensity of the was better than other samples when the etching depth was 140nm. Likewise, samples of which the diameter was 2μm has much better PL than that of the other samples.

  11. Efficient Excitonic Photoluminescence in Direct and Indirect Band Gap Monolayer MoS2.

    PubMed

    Steinhoff, A; Kim, J-H; Jahnke, F; Rösner, M; Kim, D-S; Lee, C; Han, G H; Jeong, M S; Wehling, T O; Gies, C

    2015-10-14

    We discuss the photoluminescence (PL) of semiconducting transition metal dichalcogenides on the basis of experiments and a microscopic theory. The latter connects ab initio calculations of the single-particle states and Coulomb matrix elements with a many-body description of optical emission spectra. For monolayer MoS2, we study the PL efficiency at the excitonic A and B transitions in terms of carrier populations in the band structure and provide a quantitative comparison to an (In)GaAs quantum well-structure. Suppression and enhancement of PL under biaxial strain is quantified in terms of changes in the local extrema of the conduction and valence bands. The large exciton binding energy in MoS2 enables two distinctly different excitation methods: above-band gap excitation and quasi-resonant excitation of excitonic resonances below the single-particle band gap. The latter case creates a nonequilibrium distribution of carriers predominantly in the K-valleys, which leads to strong emission from the A-exciton transition and a visible B-peak even if the band gap is indirect. For above-band gap excitation, we predict a strongly reduced emission intensity at comparable carrier densities and the absence of B-exciton emission. The results agree well with PL measurements performed on monolayer MoS2 at excitation wavelengths of 405 nm (above) and 532 nm (below the band gap). PMID:26322814

  12. Terahertz photoluminescence from S.I.-GaAs by below gap excitation via EL2 level

    SciTech Connect

    Oyama, Yutaka Dezaki, Hikari; Shimizu, Yusaku; Maeda, Kensaku

    2015-01-12

    Terahertz emission by radiative transitions in semi-conductors via shallow impurity states is investigated. We report on the observation of terahertz photoluminescence from S.I.-GaAs by below gap excitation via EL2 level which is located at the center of band gap. In order to investigate the terahertz wave emission mechanisms, the emission spectra and temperature dependence of the emission intensity are evaluated. It is shown that intense terahertz emission from S.I.-GaAs over 120 K is observed due to the thermal recovery of photo-quenched EL2 meta-stable state, and that the emission peak frequency looks to be attributed to the shallow level energy in GaAs.

  13. Photoluminescence properties of S2 molecule trapped in Melanophlogite

    NASA Astrophysics Data System (ADS)

    Messina, Fabrizio; Todaro, Michela; Buscarino, Gianpiero; Vaccaro, Lavinia; Cannas, Marco; Gelardi, Franco M.

    2016-03-01

    We studied the photoluminescence properties of a sample of SiO2-clathrate Melanophlogite, a crystalline microporous material which is found in nature as a rare mineral. Upon β irradiation, the material displays an intense light emission under near-UV illumination. We studied in detail this optical activity by steady-state and time-resolved photoluminescence measurements as a function of temperature. The spectroscopic properties we find can be ascribed to a population of quasi-free molecules trapped within each of the two different types of cage available in the structure of this clathrate, although the spectroscopic properties of the guest molecules are affected by their interactions with the host matrix. Based on the available data, we attribute the observed photoluminescence to trapped S2 molecules, emitting from their excited 3Σ u - or 3Π u electronic states, depending on the cage they are trapped in and on temperature. Our results have an impact on the fundamental understanding of host-guest interactions characteristic of microporous systems such as clathrates. Indeed, the data highlight that even a relatively weak coupling between quasi-free S2 molecules and the two types of cages provided by the Melanophlogite host has a surprisingly complex influence on the optical properties of the guest.

  14. Photoluminescence of Giant Quantum Dots Coupled With Waveguide Modes of Plasmonic Gap Bar Nanoantennas

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Nguyen, Hue-Minh; Karan, Niladri; Ghosh, Yagnaseni; Sheehan, Chris; Hollingsworth, Jennifer; Htoon, Han

    2015-03-01

    We designed a plasmonic gap bar nanoantenna, which is in resonances with the emission band of silica-coated giant-CdSe/CdS quantum dots. This antenna is composed of two parallel gold nano-bars with 40 nm gap fabricated on top of a 20 nm thick gold film and glass substrate. Utilizing two-step e-beam lithography process, we have fabricated this antenna and integrated the single silica-coated giant quantum dots into the gap. The enhanced emission rate and emission polarization have been studied for quantum dots placed at different positions along the gap bar antennas. The use of silica shell suppressed the energy transfer quenching from giant quantum dots to metal. Therefore, the detected lifetime shortening by a factor of 8 is purely resulted from the enhancement of decay rate. Experimental measurements also show that the photoluminescence intensity with polarization perpendicular to the bar can be 9 times stronger than along the bar, leading to a linear polarization degree of 0.8. Strong modulation of emission spectra has also been observed. Numerical simulations indicate that the strong linear polarization and the spectral modulation could be due to the emission coupling with the plasmonic waveguide modes.

  15. Near-Infrared Photoluminescence Properties of Endohedral Mono- and Dithulium Metallofullerenes.

    PubMed

    Wang, Zhiyong; Izumi, Noriko; Nakanishi, Yusuke; Koyama, Takeshi; Sugai, Toshiki; Tange, Masayoshi; Okazaki, Toshiya; Shinohara, Hisanori

    2016-04-26

    The optical properties of endohedral metallofullerene molecules can be tuned by changing the fullerene size as well as the number of metal atoms inside the fullerene cages. In this work we have synthesized and isolated a series of mono- and dithulium metallofullerenes, including Tm@C82 (isomers I, II, III, IV), Tm@C88 (I-IV), Tm2@C82 (I-III), and (Tm2C2)@C82 (I-III). Near-infrared photoluminescence is observed from the thulium metallofullerenes. By changing the number of Tm ion in the fullerene cage, we have found that one can vary and tune the photoluminescence from 1200 to 1300-2000 nm observed for Tm(2+) (4f(13)) in Tm@C88 and Tm(3+) (4f(12)) in (Tm2C2)@C82, respectively. The photoluminescence intensity depends sensitively on the fullerene cages. (Tm2C2)@C82 (III) exhibits the highest photoluminescence intensity among the three structural isomers because of its large HOMO-LUMO energy gap. PMID:27057619

  16. Enhanced Photoluminescence Properties of Carbon Dots by Doping with Europium.

    PubMed

    Chen, Yuan; Xu, Jiafu; Liu, Bitao; Li, Jiyun; Fang, Xiaomei; Xiong, Liqiong; Peng, Lingling; Han, Tao; Tu, Mingjing

    2016-04-01

    Europium (Eu) doped carbon dots (CDs) were synthesized via a rapid and simple microwave medi- ated method using polyethylene glycol (PEG) as a precursor, and characterized in detail. The results were that these as-prepared CDs showed a uniform and small particle size, and exhibit good pho- tostability and high photoluminescence quantum yields. Additionally, it also found that the doped Eu would change the fluorescence properties, which indicates potential applications in the field of biolabeling. PMID:27451699

  17. Indenopyrans – synthesis and photoluminescence properties

    PubMed Central

    Diac, Andreea Petronela; Ţepeş, Ana-Maria; Soran, Albert; Grosu, Ion; Terec, Anamaria; Roncali, Jean

    2016-01-01

    Summary New indeno[1,2-c]pyran-3-ones bearing different substituents at the pyran moiety were synthesized and their photophysical properties were investigated. In solution all compounds were found to be blue emitters and the trans isomers exhibited significantly higher fluorescence quantum yields (relative to 9,10-diphenylanthracene) as compared to the corresponding cis isomers. The solid-state fluorescence spectra revealed an important red shift of λmax due to intermolecular interactions in the lattice, along with an emission-band broadening, as compared to the solution fluorescence spectra. PMID:27340473

  18. Photoluminescent Fe3O4/carbon nanocomposite with magnetic property.

    PubMed

    He, Xiaodie; Liu, Yang; Li, Haitao; Huang, Hui; Liu, Jinglin; Kang, Zhenhui; Lee, Shuit-Tong

    2011-04-01

    Fe(3)O(4)/carbon nanocomposite has been prepared by a facile chemical method, and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, fourier transform infrared spectroscopy and scanning electron microscopy. The fluorescent and magnetic properties of the sample were investigated by fluorescence spectroscopy and vibrating-sample magnetometer, respectively. The results indicate that the Fe(3)O(4)/carbon nanocomposite exhibit good photoluminescent (emission ranging from 425 to 550 nm) and strong magnetic (saturation magnetization of 44.2 emu/g) properties. PMID:21269640

  19. Optical properties of GaAsBi/GaAs quantum wells: Photoreflectance, photoluminescence and time-resolved photoluminescence study

    NASA Astrophysics Data System (ADS)

    Kopaczek, J.; Linhart, W. M.; Baranowski, M.; Richards, R. D.; Bastiman, F.; David, J. P. R.; Kudrawiec, R.

    2015-09-01

    Photoreflectance (PR), photoluminescence (PL) and time-resolved PL were applied to study the optical properties, particularly the localized and delocalized states and carrier dynamics, in GaAs1-xBix/GaAs quantum wells. With increasing Bi concentration the ground state transition (i.e., the transition between the first heavy hole and the first electron subband) red shifts due to Bi-related reduction of the GaAs1-xBix energy gap. Additionally, the transition related to the excited states in the quantum wells is clearly observed for the sample with high Bi concentration of 5.6%, confirming these quantum wells are type I. The PL measurements show the S-shape behavior and indicate the strong localization effect below 150 K for all measured samples, while the PL emission above 150 K is related to delocalized states. The localized character of emission at low temperatures is confirmed by time-resolved PL studies. At 10 K the decay time has strong spectral dispersion (i.e. the decay time increases from ˜10 ns to ˜400 ns going from the high to low energy side of the PL peak). This dispersion disappears above 190 K. At room temperature the decay time is in the order of a few ns.

  20. Photoluminescence properties of cerium oxide nanoparticles as a function of lanthanum content

    SciTech Connect

    Deus, R.C.; Cortés, J.A.; Ramirez, M.A.; Ponce, M.A.; Andres, J.; Rocha, L.S.R.; and others

    2015-10-15

    Highlights: • CeO{sub 2} nanoparticles were obtained by microwave-hydrothermal method. • Rietveld refinement reveals a cubic structure. • KOH mineralizer agent exhibit weak agglomeration at low temperature and shorter time. - Abstract: The structural and photoluminescent properties at room temperature of CeO{sub 2} and La-doped CeO{sub 2} particles were undertaken. The obtained particles were synthesized by a microwave-assisted hydrothermal method (MAH) under different lanthanum contents. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman), Ultra-violet spectroscopy (UV–vis) and photoluminescence (PL) measurements were carried out. XRD revealed that the powders are free of secondary phases and crystallize in the cubic structure. Raman data show that increasing La doping content increase oxygen vacancies due to lattice expansion. The UV/vis absorption spectroscopy suggested the presence of intermediate energy levels in the band gap of structurally ordered powders. Lanthanum addition creates oxygen vacancies and shifts the photoluminescence in the low energy range leading to intense PL emission.

  1. Photoluminescence Investigation of Defects and Optical Band Gap in Multiferroic BiFeO3 Single Crystals

    NASA Astrophysics Data System (ADS)

    Moubah, Reda; Schmerber, Guy; Rousseau, Olivier; Colson, Dorothée; Viret, Michel

    2012-03-01

    Optical measurements have been carried out on high-quality BiFeO3 single crystals in order to show the presence of electronic defect states and calculate the band gap. The photoluminescence spectra show an intense electronic transition peak at a wavelength of 410 nm. This peak is large and asymmetric, indicating the existence of defects inside the gap, which we attribute to oxygen vacancies. These defects are likely to originate from the slow heating rate and long sintering times necessary to synthesize BiFeO3 single crystals. The optical band gap is measured to be 3 eV, a larger value than those previously reported.

  2. Size Dependence in Hexagonal Mesoporous Germanium: Pore Wall Thickness versus Energy Gap and Photoluminescence

    SciTech Connect

    Armatas, G. S.; Kanatzidis, Mercouri G.

    2010-08-10

    A series of hexagonal mesoporous germanium semiconductors with tunable wall thickness is reported. These nanostructures possess uniform pores of 3.1-3.2 nm, wall thicknesses from 1.3 to 2.2 nm, and large internal BET surface area in the range of 404-451 m2/g. The porous Ge framework of these materials is assembled from the templated oxidative self-polymerization of (Ge9)4- Zintl clusters. Total X-ray scattering analysis supports a model of interconnected deltahedral (Ge9)-cluster forming the framework and X-ray photoelectron spectroscopy indicates nearly zero-valence Ge atoms. We show the controllable tuning of the pore wall thickness and its impact on the energy band gap which increases systematically with diminishing wall thickness. Furthermore, there is room temperature photoluminescence emission which shifts correspondingly from 672 to 640 nm. The emission signal can be quenched via energy transfer with organic molecules such as pyridine diffusing into the pores.

  3. Photoluminescence properties of Mg-doped InN nanowires

    SciTech Connect

    Zhao, Songrui; Liu, Xuedong; Mi, Zetian

    2013-11-11

    In this work, photoluminescence (PL) properties of nearly defect-free Mg-doped InN nanowires were investigated in detail. The low-doped sample exhibits two PL emission peaks up to 152 K, which can be ascribed to the band-to-band recombination and the Mg-acceptor energy level related recombination, respectively. For the high-doped sample, the Mg-acceptor energy level related transition dominates. Detailed power dependent PL studies further indicate that the Mg-acceptor energy level related PL emission is due to the donor-acceptor pair recombination process, which subsequently evolves into the free-to-acceptor recombination with increasing temperature.

  4. Enhanced Photoluminescence Property for Quantum Dot-Gold Nanoparticle Hybrid

    NASA Astrophysics Data System (ADS)

    Huang, Qianqian; Chen, Jing; Zhao, Jian; Pan, Jiangyong; Lei, Wei; Zhang, Zichen

    2015-10-01

    In this paper, we have synthesized ZnCdSeS quantum dots (QDs)-gold nanoparticle (Au NPs) hybrids in aqueous solution via bi-functional linker mercaptoacetic acid (MPA). The absorption peaks of ZnCdSeS QDs and Au are both located at 520 nm. It is investigated that PL intensity of QD-Au hybrid can be affected by the amounts of Au and pH value of hybrid solution. The located surface plasmon resonance (LSPR) effect of QD-Au NPs has been demonstrated by increased fluorescence intensity. The phenomenon of fluorescence enhancement can be maximized under the optimized pH value of 8.5. LSPR-enhanced photoluminescence property of QD-Au hybrid will be beneficial for the potential applications in the area of biological imaging and detection.

  5. Enhanced Photoluminescence Property for Quantum Dot-Gold Nanoparticle Hybrid.

    PubMed

    Huang, Qianqian; Chen, Jing; Zhao, Jian; Pan, Jiangyong; Lei, Wei; Zhang, Zichen

    2015-12-01

    In this paper, we have synthesized ZnCdSeS quantum dots (QDs)-gold nanoparticle (Au NPs) hybrids in aqueous solution via bi-functional linker mercaptoacetic acid (MPA). The absorption peaks of ZnCdSeS QDs and Au are both located at 520 nm. It is investigated that PL intensity of QD-Au hybrid can be affected by the amounts of Au and pH value of hybrid solution. The located surface plasmon resonance (LSPR) effect of QD-Au NPs has been demonstrated by increased fluorescence intensity. The phenomenon of fluorescence enhancement can be maximized under the optimized pH value of 8.5. LSPR-enhanced photoluminescence property of QD-Au hybrid will be beneficial for the potential applications in the area of biological imaging and detection. PMID:26471479

  6. Synthesis and photoluminescent and nonlinear optical properties of manganese doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Nazerdeylami, Somayeh; Saievar-Iranizad, Esmaiel; Dehghani, Zahra; Molaei, Mehdi

    2011-01-01

    In this work we synthesized ZnS:Mn 2+ nanoparticles by chemical method using PVP (polyvinylpyrrolidone) as a capping agent in aqueous solution. The structure and optical properties of the resultant product were characterized using UV-vis optical spectroscopy, X-ray diffraction (XRD), photoluminescence (PL) and z-scan techniques. UV-vis spectra for all samples showed an excitonic peak at around 292 nm, indicating that concentration of Mn 2+ ions does not alter the band gap of nanoparticles. XRD patterns showed that the ZnS:Mn 2+ nanoparticles have zinc blende structure with the average crystalline sizes of about 2 nm. The room temperature photoluminescence (PL) spectrum of ZnS:Mn 2+ exhibited an orange-red emission at 594 nm due to the 4T 1- 6A 1 transition in Mn 2+. The PL intensity increased with increase in the Mn 2+ ion concentration. The second-order nonlinear optical properties of nanoparticles were studied using a continuous-wave (CW) He-Ne laser by z-scan technique. The nonlinear refractive indices of nanoparticles were in the order of 10 -8 cm 2/W with negative sign and the nonlinear absorption indices of these nanoparticles were obtained to be about 10 -3 cm/W with positive sign.

  7. Impact of oxygen bonding on the atomic structure and photoluminescence properties of Si-rich silicon nitride thin films

    SciTech Connect

    Nguyen, P. D.; Sunding, M. F.; Vestland, L. O.; Finstad, T. G.; Olsen, A.; Kepaptsoglou, D. M.; Ramasse, Q. M.

    2012-10-01

    The atomic structure and optical properties of Si-rich silicon nitride thin films have been for decades the subject of intense research, both theoretically and experimentally. It has been established in particular that modifying the chemical composition of this material (e.g., the Si excess concentration) can lead to dramatic differences in its physical, optical, and electrical properties. The present paper reports on how the incorporation of oxygen into silicon nitride networks influences their chemical bonding and photoluminescence properties. Here, by using a combination of analytical scanning transmission electron microscopy and x-ray photoelectron spectroscopy it is demonstrated that the structure of Si-rich silicon nitride with low O content can be described by the co-existence of Si nanocrystals in a Si{sub 3}N{sub 4} matrix, with occasional localized nano-regions of a Si{sub 2}ON{sub 2} phase, depending on the amount of excess Si. Furthermore, it is shown that the structure of silicon nitride with high O content can be adequately described by a so-called random bonding model, according to which the material consists in bonded networks of randomly distributed tetrahedral SiO{sub x}N{sub 4-x} (where x = 0, 1, 2, 3, and 4). Photoluminescence measurements indicate that the effect of O is to introduce a gap state in the band gap of Si{sub 3}N{sub 4} matrix. When a large amount of O is introduced, on the other hand, the photoluminescence measurements are in agreement with a shifted conduction band minimum in the dielectric. For both cases (high and low O content), Si dangling bonds were found to give rise to the deep level in the band gap of the nitride matrix, causing the dominant emission band in the photoluminescence of the films.

  8. Temperature dependence of photoluminescence properties in a thermally activated delayed fluorescence emitter

    SciTech Connect

    Niwa, Akitsugu; Kobayashi, Takashi Nagase, Takashi; Naito, Hiroyoshi; Goushi, Kenichi; Adachi, Chihaya

    2014-05-26

    Using steady-state and time-resolved photoluminescence (PL) spectroscopy, we have investigated the temperature dependence of PL properties of 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyano-benzene (4CzIPN), which have a small energy gap between its singlet and triplet excited states and thus exhibits efficient thermally activated delayed fluorescence [H. Uoyama et al., Nature 492, 235 (2012)]. Below around 100 K, PL quantum efficiency of 4CzIPN thin films is largely suppressed and strong photoexcitation intensity dependence appears. These features can be explained by using rate equations for the densities of singlet and triplet excited states considering a triplet-triplet annihilation process.

  9. Temperature dependence of photoluminescence properties in a thermally activated delayed fluorescence emitter

    NASA Astrophysics Data System (ADS)

    Niwa, Akitsugu; Kobayashi, Takashi; Nagase, Takashi; Goushi, Kenichi; Adachi, Chihaya; Naito, Hiroyoshi

    2014-05-01

    Using steady-state and time-resolved photoluminescence (PL) spectroscopy, we have investigated the temperature dependence of PL properties of 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyano-benzene (4CzIPN), which have a small energy gap between its singlet and triplet excited states and thus exhibits efficient thermally activated delayed fluorescence [H. Uoyama et al., Nature 492, 235 (2012)]. Below around 100 K, PL quantum efficiency of 4CzIPN thin films is largely suppressed and strong photoexcitation intensity dependence appears. These features can be explained by using rate equations for the densities of singlet and triplet excited states considering a triplet-triplet annihilation process.

  10. Compositional dependence of the direct and indirect band gaps in Ge1-ySny alloys from room temperature photoluminescence: implications for the indirect to direct gap crossover in intrinsic and n-type materials

    NASA Astrophysics Data System (ADS)

    Jiang, L.; Gallagher, J. D.; Senaratne, C. L.; Aoki, T.; Mathews, J.; Kouvetakis, J.; Menéndez, J.

    2014-11-01

    The compositional dependence of the lowest direct and indirect band gaps in Ge1-ySny alloys has been determined from room-temperature photoluminescence measurements. This technique is particularly attractive for a comparison of the two transitions because distinct features in the spectra can be associated with the direct and indirect gaps. However, detailed modeling of these room temperature spectra is required to extract the band gap values with the high accuracy required to determine the Sn concentration yc at which the alloy becomes a direct gap semiconductor. For the direct gap, this is accomplished using a microscopic model that allows the determination of direct gap energies with meV accuracy. For the indirect gap, it is shown that current theoretical models are inadequate to describe the emission properties of systems with close indirect and direct transitions. Accordingly, an ad hoc procedure is used to extract the indirect gap energies from the data. For y < 0.1 the resulting direct gap compositional dependence is given by ΔE0 = -(3.57 ± 0.06)y (in eV). For the indirect gap, the corresponding expression is ΔEind = -(1.64 ± 0.10)y (in eV). If a quadratic function of composition is used to express the two transition energies over the entire compositional range 0 ≦̸ y ≦̸ 1, the quadratic (bowing) coefficients are found to be b0 = 2.46 ± 0.06 eV (for E0) and bind = 1.03 ± 0.11 eV (for Eind). These results imply a crossover concentration yc = 0.073-0.006+0.007, much lower than early theoretical predictions based on the virtual crystal approximation, but in better agreement with predictions based on large atomic supercells.

  11. Nanotexturing To Enhance Photoluminescent Response of Atomically Thin Indium Selenide with Highly Tunable Band Gap.

    PubMed

    Brotons-Gisbert, Mauro; Andres-Penares, Daniel; Suh, Joonki; Hidalgo, Francisco; Abargues, Rafael; Rodríguez-Cantó, Pedro J; Segura, Alfredo; Cros, Ana; Tobias, Gerard; Canadell, Enric; Ordejón, Pablo; Wu, Junqiao; Martínez-Pastor, Juan P; Sánchez-Royo, Juan F

    2016-05-11

    Manipulating properties of matter at the nanoscale is the essence of nanotechnology, which has enabled the realization of quantum dots, nanotubes, metamaterials, and two-dimensional materials with tailored electronic and optical properties. Two-dimensional semiconductors have revealed promising perspectives in nanotechnology. However, the tunability of their physical properties is challenging for semiconductors studied until now. Here we show the ability of morphological manipulation strategies, such as nanotexturing or, at the limit, important surface roughness, to enhance light absorption and the luminescent response of atomically thin indium selenide nanosheets. Besides, quantum-size confinement effects make this two-dimensional semiconductor to exhibit one of the largest band gap tunability ranges observed in a two-dimensional semiconductor: from infrared, in bulk material, to visible wavelengths, at the single layer. These results are relevant for the design of new optoelectronic devices, including heterostructures of two-dimensional materials with optimized band gap functionalities and in-plane heterojunctions with minimal junction defect density. PMID:27080194

  12. Photoluminescence Properties Research on Graphene Quantum Dots/Silver Composites.

    PubMed

    Wang, Jun; Li, Yan; Zhang, Bo-Ping; Xie, Dan-Dan; Ge, Juan; Liu, Hui

    2016-04-01

    Graphene quantum dots (GQDs) possess unique properties of graphene and exhibit a series of new phenomena of 0 dimension (D) carbon materials. Thus, GQDs have attracted much attention from researchers and have shown great promise for many applications. Recently, many works focus on GQDs-metal ions and metal nanoparticles (NPs). Although, many researches point out that metal ions and metal NPs have significant effect on photoluminescence (PL) feature of GQDs, mainly focus on PL intensity. Here, for the first time, we reported that metal NPs also affected PL peak position which was dependent on the mix mechanism of metal and GQDs. When GQDs-silver (Ag) composite mixed by physical method and excited at a wavelength of 320 nm, PL peak position of composites first showed blue-shifted then red-shifted with increasing of Ag content. However, if GQDs-Ag composite prepared by chemical method, PL peak position of the composites blue-shifted. Furthermore, the shift of PL peak position of GQDs-Ag prepared both for physical and chemical method displayed excitation-dependent feature. When the excitation wavelength approached to Ag SPR peaks, no obvious PL shift was observed. The mechanism for different PL shifts and the phenomenon of excitation-dependent PL shift as well as the formation mechanism of GQDs-Ag composite by chemical method are discussed in detail in this paper. PMID:27451653

  13. The excitonic photoluminescence mechanism and lasing action in band-gap-tunable CdS(1-x)Se(x) nanostructures.

    PubMed

    Dai, Jun; Zhou, Pengxia; Lu, Junfeng; Zheng, Hongge; Guo, Jiyuan; Wang, Fang; Gu, Ning; Xu, Chunxiang

    2016-01-14

    Bandgap tunable semiconductor materials have wide application in integrated-optoelectronic and communication devices. The CdS1-xSex ternary semiconductor materials covering green-red bands have been reported previously, but their basic band-gap and optical properties crucial to the performance of the CdS1-xSex-based optoelectronic devices have not been deeply understood. In this paper, we theoretically simulated and discussed the feasibility of bandgap-tunable CdS1-xSex nanomaterials for designing wavelength tunable microlasers. Then we fabricated the CdS1-xSex nanobelts with their band gap ranging from 2.4 to 1.74 eV by adjusting the composition ratio x in the vapor-phase-transport growth process. The temperature-dependent photoluminescence and exciton-related optical constants of the CdS1-xSex nanobelts were carefully demonstrated. Finally, the wavelength-tunable Fabry-Perot lasing in CdS1-xSex nanobelts was obtained, and the Fabry-Perot lasing mechanism was numerically simulated by the FDTD method. The systematic results on the mechanism of the tunable band gap, exciton properties and lasing of the CdS1-xSex nanostructure help us deeply understand the intrinsic optical properties of this material, and will build a strong foundation for future application of green-red wavelength-tunable CdS1-xSex microlasers. PMID:26488436

  14. Photoluminescence properties and exciton dynamics in monolayer WSe{sub 2}

    SciTech Connect

    Yan, Tengfei; Qiao, Xiaofen; Liu, Xiaona; Tan, Pingheng; Zhang, Xinhui

    2014-09-08

    In this work, comprehensive temperature and excitation power dependent photoluminescence and time-resolved photoluminescence studies are carried out on monolayer WSe{sub 2} to reveal its properties of exciton emissions and related excitonic dynamics. Competitions between the localized and delocalized exciton emissions, as well as the exciton and trion emissions are observed, respectively. These competitions are suggested to be responsible for the abnormal temperature and excitation intensity dependent photoluminescence properties. The radiative lifetimes of both excitons and trions exhibit linear dependence on temperature within the temperature regime below 260 K, providing further evidence for two-dimensional nature of monolayer material.

  15. Photoluminescence properties of Jahn-Teller transition-metal ions

    NASA Astrophysics Data System (ADS)

    Sanz-Ortiz, Marta N.; Rodríguez, Fernando

    2009-09-01

    This work investigates the influence of electron-phonon coupling associated with E ⊗e and T ⊗e Jahn-Teller (JT) effect in different transition-metal (TM) ions on de-excitation phenomena through nonradiative multiphonon relaxation, i.e., photoluminescence (PL) quenching. We developed a configurational curve model which is able to predict from the absorption spectrum whether a given JT-TM ion is PL or quenched. The prediction is made on the basis of an adapted Dexter-Klick-Russell parameter for JT systems, defined in terms of spectroscopic parameters through ΛJT=αΔeabs/Eabs, where Δeabs refers to the splitting of the parent octahedral Eg states by the JT distortion in E ⊗e (α =3/4) or T ⊗e (α =1/4), and Eabs is the energy of the first absorption band involving electronic transition between Eg and T2g. We show that PL in any JT-TM ion occurs whenever ΛJT<0.1 or is quenched if ΛJT>0.2. This result is noteworthy since it allows us to establish structural requirements for the JT-TM ion and the host crystal to be PL. Although PL properties of materials containing TM ions depend on a variety of structural factors such as the electronic configuration, the site symmetry, and the crystal field produced by neighboring atoms, the present model achieves this goal through a simple spectroscopic parameter: ΛJT. In this work we correlated the PL properties of different sixfold-coordinated JT systems such as Ti3+, Cu2+, Mn3+, Cr2+, Fe2+, Co3+, and Ni3+ in halides and oxides with ΛJT obtained from their respective absorption spectra. From this analysis we conclude that depending on the nature of the JT coupling and its strength, PL is either strongly favored or quenched in T ⊗e while it is mostly quenched in E ⊗e systems due to the larger JT distortion.

  16. Tailoring the photoluminescence properties of ionic iridium complexes.

    PubMed

    Terki, Rachida; Simoneau, Louis-Philippe; Rochefort, Alain

    2009-01-22

    Density functional theory/time-dependent density functional theory (DFT/TD-DFT) calculations were performed to investigate the structural, electronic, and optical properties of ionic Ir complexes with several different substituents on the cyclometalated ligand. Geometric parameters, highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap, and Mulliken charge on different parts of the molecule were obtained and correlated to the calculated emission and absorption energies. We also discuss the influence of the position of fluoro-substituent on the spectroscopic properties of Ir complexes. As a major trend, the investigated complexes exhibit band shifts that correlate with the electron-withdrawing nature of the ligand substituent. Our results also show that the lowest emission wavelength is observed at ortho position with respect to the coordinating carbon. The different variations observed are discussed in terms of emissive states and, more especially, in terms of the mixture of ligand-ligand charge-transfer (LLCT) and metal-ligand charge-transfer (MLCT) states. PMID:19117414

  17. Microstructural and photoluminescence properties of tin dioxide modified by electron beam irradiation.

    PubMed

    Du, Juan; Wang, Jian; Jiao, Zheng; Wu, Minghong; Shek, C H; Wu, C M L; Lai, J K L; Chen, Z W

    2011-11-01

    A modified technique was developed by electron beam irradiation to prepare tin dioxide (SnO2) nanocrystals using the sol-gel method. SnO2 nanoparticles were radiated under a 1,400 KGy dose. The morphology and microstructure of the SnO2 nanocrystals were investigated by X-ray diffraction, high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. The results indicate that the irradiated SnO2 nanoparticles have better crystallinity than unirradiated SnO2 nanoparticles, and the resulting nanocrystals have a tetragonal rutile crystalline structure. The HRTEM image proves that the average grain size is about 4 nm, and the clear lattice fringes indicate the improvement of SnO2 nanocrystals after irradiation. The Raman spectrum shows that there are new peaks at 535 cm(-1) and 691 cm(-1). The optical properties of SnO2 nanoparticles were characterized by ultraviolet-visible (UV-vis) and photoluminescence spectrophotometers. The band gap energy of the irradiated SnO2 was 3.29 eV smaller than that of the unirradiated SnO2 due to size effects and some defects of SnO2 nanocrystals. This work provides a novel approach for the improvement of SnO2 nanocrystals. The optical properties of the irradiated SnO2 nanomaterials are also expected to improve. PMID:22413277

  18. Plasmonically-enhanced mid-infrared photoluminescence in a metal/narrow-gap semiconductor structure

    NASA Astrophysics Data System (ADS)

    Lu, Pengqi; Cai, Chunfeng; Zhang, Bingpo; Liu, Bozhi; Wu, Huizhen; Bi, Gang; Si, Jianxiao

    2016-05-01

    We report the enhancement of the mid-infrared (MIR) luminescence intensity in a nanoscale metal/semiconductor structure by the coupling of surface plasmon polaritons (SPPs) with excitons in a narrow-gap semiconductor. The SPPs are efficiently excited by the total internal reflection photons at a metal/semiconductor interface. The intense electric field induced by SPPs, in turn, greatly changes the radiative recombination rates of the excitons generated by the pumping laser and thus the MIR luminescence intensity. The finding avails the understanding of fundamental science of SPs in narrow-gap semiconductors and the development of novel MIR devices.

  19. Synthesis of ZnO flowers and their photoluminescence properties

    SciTech Connect

    Wu Changle; Qiao Xueliang Luo Langli; Li Haijun

    2008-07-01

    Flower-like ZnO nano/microstructures have been synthesized by thermal treatment of Zn(NH{sub 3}){sub 4}{sup 2+} precursor in aqueous solvent, using ammonia as the structure directing agent. A number of techniques, including X-ray diffraction (XRD), field emission scan electron microscopy (FESEM), transmission electron microscopy (TEM), thermal analysis, and photoluminescence (PL) were used to characterize the obtained ZnO structures. The photoluminescence (PL) measurements indicated that the as-synthesized ZnO structures showed UV ({approx}375 nm), blue ({approx}465 nm), and yellow ({approx}585 nm) emission bands when they were excited by a He-Gd laser using 320 nm as the excitation source. Furthermore, it has been interestingly found that the intensity of light emission at {approx}585 nm remarkably decreased when the obtained ZnO nanocrystals were annealed at 600 deg. C for 3 h in air. The reason might be the possible oxygen vacancies and interstitials in the sample decreased at high temperature.

  20. Synthesis and Photoluminescence Properties of SnO2 Nanopowder

    NASA Astrophysics Data System (ADS)

    Arai, Takahiro; Adachi, Sadao

    2012-10-01

    SnO2 nanopowder was synthesized by calcining metastannic salt (SnO2·H2O) prepared by chemically etching metallic Sn in aqueous HNO3 solution. The calcined SnO2 nanopowder was investigated by X-ray diffraction (XRD) measurement and photoluminescence (PL) spectroscopy. The XRD and PL intensities increased with increasing calcining temperature, yielding an activation energy of ˜0.65 eV. The PL spectra of the calcined SnO2 nanopowder exhibited green (G) and red (R) emission bands with peaks at ˜2.5 and ˜2.0 eV, respectively, that were clearly dependent not only on the excitation light wavelength but also on the sample temperature. The temperature dependence of the PL intensity between 20 and 300 K was explained by the thermal quenching with activation energies of ˜15 meV (T=20-60 K) and ˜0.12-0.18 eV (T ≥100 K). The G and R emission states were found to originate from the Jahn-Teller effect of the 5s2 (Sn2+) ions in the SnO2 matrix and were similar to those generally observed in many ns2-doped alkali halides and SnCl2.

  1. Heterometallic europium disiloxanediolates: synthesis, structural diversity, and photoluminescence properties.

    PubMed

    Rausch, Janek; Lorenz, Volker; Hrib, Cristian G; Frettlöh, Vanessa; Adlung, Matthias; Wickleder, Claudia; Hilfert, Liane; Jones, Peter G; Edelmann, Frank T

    2014-11-01

    This contribution presents a full account of a structurally diverse class of heterometallic europium disiloxanediolates. The synthetic protocol involves in situ metalation of (HO)SiPh2OSiPh2(OH) (1) with either (n)BuLi or KN(SiMe3)2 followed by treatment with EuCl3 in suitable solvents such as 1,2-dimethoxyethane (DME) or tetrahydrofuran (THF). Reaction of EuCl3 with 2 equiv of (LiO)SiPh2OSiPh2(OLi) in DME afforded the Eu(III) bis(disiloxanediolate) "ate" complex [{(Ph2SiO)2O}2{Li(DME)}3]EuCl2 (2), which upon attempted reduction with Zn gave the tris(disiloxanediolate) [{(Ph2SiO)2O}3{Li(DME)}3]Eu (3). Treatment of EuCl3 with (LiO)SiPh2OSiPh2(OLi) in a molar ratio of 1:2 yielded both the ate complex [{(Ph2SiO)2O}3Li{Li(THF)2}{Li(THF)}]EuCl·Li(THF)3 (4) and the LiCl-free europium(III) complex [{(Ph2SiO)2O}2{Li(THF)2}2]EuCl (5). Compound 5 was found to exhibit a brilliant red triboluminescence. When (KO)SiPh2OSiPh2(OK) was used as starting material in a 3:1 reaction with EuCl3, the Eu(III) tris(disiloxanediolate) [{(Ph2SiO)2O}3{K(DME)}3]Eu (6) was isolated. Attempted ligand transfer between 5 and (DAD(Dipp))2Ba(DME) (DAD(Dipp) = N,N'-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene) afforded the unique mixed-valent Eu(III)/Eu(II) disiloxanediolate cluster [(Ph2SiO)2O]6Eu(II)4Eu(III)2Li4O2Cl2 (7). All new complexes were structurally characterized by X-ray diffraction. Photoluminescence studies were carried out for complex 5 showing an excellent color quality, due to the strong (5)D0→(7)F2 transition, but a weak antenna effect. PMID:25330143

  2. Photophysical properties and biocompatibility of Photoluminescent Y2O3:Eu nanoparticles in polymethylmetacrylate matrix.

    PubMed

    Abe, Shigeaki; Hamba, Yusuke; Iwadera, Nobuki; Yamagata, Shuichi; Yawaka, Yasutaka; Uo, Motohiro; Iida, Junichiro; Kiba, Takayuki; Murayama, Akihiro; Watari, Fumio

    2014-04-01

    In this study, we produced europium-doped yttoria (Y2O3:Eu) nanoparticles and investigated their photoluminescent properties and biocompatibility. The Y2O3:Eu nanoparticles showed excellent photoluminescent properties and cytocompatibility. We also analyzed the photophysical properties of the nanoparticles in PMMA films. When the Y2O3:Eu nanoparticles were incorporated in the polymer film, they showed a strong red emission spectrum, similar to that seen with the particles alone. Energy dispersive X-ray spectroscopy (EDS) measurements indicated that the particles were distributed homogeneously in the PMMA film. Such materials could be applied not only to optoelectronic devices but also to biomedical applications such as bioimaging tools or luminescent medical/dental adhesive materials. PMID:24734706

  3. One-dimensional rare earth compounds and complexes: preparation and improved photoluminescence properties.

    PubMed

    Song, Hongwei; Pan, Guohui; Bai, Xue; Li, Suwen; Yu, Hongquan; Zhang, Hui

    2008-03-01

    One-dimensional nanosized phosphors demonstrate special structural and photoluminescence properties, which have application potential in some optical fields. In this article, we present our recent progress on preparation and luminescence properties of some one-dimensional rare earth compounds and complexes, the core-shell oxide nanowires prepared by a two-step hydrothermal route, the nanowires of some inorganic compounds doped with rare earths and rare earth complexes/PVP composites prepared by the electrospinning method, and the rare earth complexes in the SBA-15 mesoporous molecule sieves. In these systems, some novel or improved photoluminescence properties are observed such as improved luminescence quantum yield, thermal stability and/or photostability, and depressed thermal effect in upconversion luminescence. PMID:18468146

  4. Radiative recombination model of degenerate semiconductor and photoluminescence properties of 3C-SiC by P and N doping

    NASA Astrophysics Data System (ADS)

    Wang, Kun; Fang, Xiao-Yong; Li, Ya-Qin; Yin, Ai-Cha; Jin, Hai-Bo; Yuan, Jie; Cao, Mao-Sheng

    2012-08-01

    Based on radiative recombination theory, we have established a recombination model that can be used to calculate photoluminescence (PL) intensity for degenerate semiconductors. Using this model and density functional theory, we calculated photoluminescence excitation (PLE) and PL spectra of intrinsic 3C-SiC, P-doped SiC and N-doped SiC. The violet or near ultraviolet PLE peaks were found to be observed in PLE spectra for Sin-1PCn and SinNCn-1 (n = 4, 8, 12, and 16). Compared to intrinsic 3C-SiC, doped 3C-SiC exhibits higher PL peaks which for P-doped SiC are in the indigo spectral region, near the 3C-SiC's peak, and for N-doped SiC appear in the green. The phenomena are studied through analyses of band structure, carrier concentration, and absorption. For doped 3C-SiC, the PL properties are mainly improved by the band-gap transformation from indirect to direct and the increase in carrier concentration near the Fermi level.

  5. Nanoparticle shape anisotropy and photoluminescence properties: Europium containing ZnO as a Model Case.

    PubMed

    Gerigk, Melanie; Ehrenreich, Philipp; Wagner, Markus R; Wimmer, Ilona; Reparaz, Juan Sebastian; Torres, Clivia M Sotomayor; Schmidt-Mende, Lukas; Polarz, Sebastian

    2015-10-28

    The precise control over electronic and optical properties of semiconductor (SC) materials is pivotal for a number of important applications like in optoelectronics, photocatalysis or in medicine. It is well known that the incorporation of heteroelements (doping as a classical case) is a powerful method for adjusting and enhancing the functionality of semiconductors. Independent from that, there already has been a tremendous progress regarding the synthesis of differently sized and shaped SC nanoparticles, and quantum-size effects are well documented experimentally and theoretically. Whereas size and shape control of nanoparticles work fairly well for the pure compounds, the presence of a heteroelement is problematic because the impurities interfere strongly with bottom up approaches applied for the synthesis of such particles, and effects are even stronger, when the heteroelement is aimed to be incorporated into the target lattice for chemical doping. Therefore, realizing coincident shape control of nanoparticle colloids and their doping still pose major difficulties. Due to a special mechanism of the emulsion based synthesis method presented here, involving a gelation of emulsion droplets prior to crystallization of shape-anisotropic ZnO nanoparticles, heteroelements can be effectively entrapped inside the lattice. Different nanocrystal shapes such as nanorods, -prisms, -plates, and -spheres can be obtained, determined by the use of certain emulsification agents. The degree of morphologic alterations depends on the type of incorporated heteroelement M(n+), concentration, and it seems that some shapes are more tolerant against doping than others. Focus was then set on the incorporation of Eu(3+) inside the ZnO particles, and it was shown that nanocrystal shape and aspect ratios could be adjusted while maintaining a fixed dopant level. Special PL properties could be observed implying energy transfer from ZnO excited near its band-gap (3.3 eV) to the Eu(3+) states

  6. Synthesis and Photoluminescent Properties of Arylethynyl substituted 9,10-Anthraquinones

    NASA Technical Reports Server (NTRS)

    Yang, Jin-Hua; Dass, Amala; Sotiriou-Leventis, Chariklia; Leventis, Nicholas

    2003-01-01

    A series of arylethynyl substituted anthraquinones were synthesized via Sonogashira coupling reactions of 2,7- dibromo-, 2,6-dibromo- and 2-bromoanthraquinone with para-substituted phenylacetylenes. While the redox properties of those compounds are almost insensitive to substitution, their absorption maxima are linearly related to the Hammett constants for electron donating and electron withdrawing groups separately. All compounds are photoluminescent both in solution (quantum yield of emission approximately 2%) and as solids. X-ray crystallographic characterization of 2,7-bisphenylethynyl anthraquinone indicates a monoclinic p2(l/n) space group and no indication for pi-overlap that would promote self-quenching. The emission maxima are red- shifted by both electron donating and electron withdrawing groups alike. The Stokes shifts of all compounds are significant and are correlated to the electronic properties of the substituents. The reduced forms of these compounds are also photoluminescent and the emission originates from the dihydroanthraquinone core.

  7. Photoluminescent properties of SPAN-80 coated intrinsic and extrinsic ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Kavita; Kumar, Dinesh; Singh, Karamjit; Kumar, Sunil; Bhatti, H. S.

    2016-05-01

    Semiconductor nanostructures catch the attention due to morphology tunable properties. SPAN-80-Capped intrinsic and extrinsic ZnO nanostructures have been synthesized by the simple wet-chemical synthesis route. Structural behavior (morphology and crystallography) and photoluminescence performance of synthesized nanomaterials have been explored as a function of variable SPAN-80 concentration (0.05-0.125%). Crystallographic studies reveal that the prepared products possess wurtzite structure. Electron microscopy infers that the quantum dots are bunched together to form multifaceted morphology for 0.05% SPAN-80 concentration, whereas rectangular shape has been observed for extreme capping concentration. Photoluminescence properties have affected drastically with the introduction of SPAN-80 during the precipitation reaction. Photoluminescent properties of the synthesized nanostructures are strongly dependent on SPAN-80 concentration. Augmentation of capping concentration from 0.05% to 0.075% diminishes the luminescence quantum yield due to increased surface passivation whereas further addition of capping agent beyond the optimum capping concentration (0.075%) enhances the PL intensity due to increased energy transfer from capping shell to the nanostructure core.

  8. Transmission properties of frequency selective structures with air gaps

    NASA Astrophysics Data System (ADS)

    Meng, Zhi-Jun; Wang, Li-Feng; Lü, Ming-Yun; Wu, Zhe

    2010-12-01

    The transmission properties of compound frequency selective structures with dielectric slab and air gaps were investigated by computation and experimentation. Mechanism analyses were also carried out. Results show that the air gaps have a distinct influence on the transmission properties. Resonant frequency of the structure would increase rapidly when the air gap appears. After the gap gets larger to a specific value, generally 1/5 wavelength corresponding to the resonant frequency, the transmission properties would change periodically with the gap thickness. The change of transmission properties in one period has a close relationship with the dielectric thickness. These results provide a new method for designing a bandpass radome of large incidence angle and low loss with the concept of stealth shield radome.

  9. Photoluminescence and radiation response properties of Ce3+-doped CsCaCl3 crystalline scintillator

    NASA Astrophysics Data System (ADS)

    Fujimoto, Yutaka; Saeki, Keiichiro; Tanaka, Hironori; Yahaba, Takuma; Yanagida, Takayuki; Koshimizu, Masanori; Asai, Keisuke

    2016-09-01

    In this paper, we report on the photoluminescence and scintillation properties of a newly developed CsCaCl3:Ce (0.5 mol%) crystalline scintillator grown by the vertical Bridgman method. The fluorescence quantum efficiency for the Ce3+ characteristic emission bands centered at around 350–400 nm was 76% under excitation at 330 nm light. The photoluminescence decay time of the Ce3+ was approximately 32 ns. When x-ray excited the crystal, intense emission bands were observed at 350–400 nm, and could be attributed to the Ce3+ emission. The scintillation light yield of the developed crystal was ∼7600 ph MeV‑1 compared to a NaI:Tl commercial scintillator, and the principal scintillation decay time was approximately 340 ns plus two fast components of around 1.6 ns and 45 ns.

  10. Preparation and photoluminescence properties of europium ions doped TiO2 nanocrystals.

    PubMed

    Liu, Hai; Yu, Lixin

    2013-07-01

    In this paper, pure and Eu3+ doped TiO2 nanocrystals (NCs) have been fabricated successfully by a two steps of sol-gel and hydrothermal methods. The microstructures, morphologies and photoluminescent properties of Eu(3+)-TiO2 were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and photoluminescence spectroscopy (PL). XRD and PL results show that the existent of rare earth can inhibit the transformation of TiO2 NCs from anatase to rutile phase and can improve the luminescence intensity of the prepared samples. The room-temperature PL emission of the as-grown samples is dominated by the 5D(0)-7F(j) transitions of Eu3+ ions. But the luminescence intensity drops dramatically when the annealing temperature reaches a relatively high degree because of the formation of the rutile phase of TiO2 NCs hosts. PMID:23901539

  11. Preparation and photoluminescence properties of Sm3+-doped ZrO2 nanotube arrays

    NASA Astrophysics Data System (ADS)

    Fu, Ning; Wang, Xixin; Ma, Yuanhui; Wang, Mingli; Li, Jiaxin; Zhao, Jianling

    2016-04-01

    Zr-Sm (3 at.% Sm) alloy was prepared through a powder metallurgical method. Sm3+-doped ZrO2 nanotube arrays have been achieved directly by anodizing the Zr-Sm alloy. The effects of electrolyte and annealing temperature on the morphologies and structures of the nanotube arrays were studied. The photoluminescence properties of Sm3+-doped ZrO2 nanotube arrays prepared in aqueous solution and formamide  +  glycerol solution were studied in detail as well. Results show that tetragonal ZrO2 promoted the photoluminescence efficiency of this system. Under excitation at 407 nm, the sample prepared in aqueous solution annealed at 600 °C displayed the strongest emission peak at 571 nm, corresponding to the 4G5/2  →  6H5/2 samarium transition.

  12. Temperature-dependent photoluminescence properties of quaternary ZnAgInS quantum dots.

    PubMed

    Zhou, Ping; Zhang, Xiaosong; Liu, Xiaojuan; Xu, Jianping; Li, Lan

    2016-08-22

    A series of ZnAgInS (ZAIS) quantum dots were synthesized and their optical properties were tuned by adjusting the reaction times from 5 to 30 min. The emission spectra were observed ranging from 619 to 667 nm. The temperature-dependent photoluminescence properties of ZAIS QDs were investigated from 10 K to 300 K that show a blue shift of spectra line with increasing intensity as well as broadening of spectral line owing to the coupling of the carrier to acoustic phonon. We have also discussed and investigated the internal luminescence mechanism of ZAIS QDs. PMID:27557228

  13. Effects of rapid thermal annealing conditions on GaInNAs band gap blueshift and photoluminescence intensity

    SciTech Connect

    Liverini, V.; Rutz, A.; Keller, U.; Schoen, S.

    2006-06-01

    We have studied the effects of various conditions of rapid thermal annealing (RTA) on 10 nm GaInNAs/GaAs single quantum wells (SQWs) with fixed indium concentration and increasing nitrogen content to obtain photoluminescence (PL) in the telecom wavelength regime of 1.3 and 1.5 {mu}m. Specifically, we analyzed the results of annealing for a fixed short time but at different temperatures and for longer times at a fixed temperature. In all experiments, InGaAs SQWs with the same In concentration were used as references. For both RTA conditions, the well-known blueshift of the band gap energy and the PL intensity improvement show trends that reveal that these are unrelated effects. At high RTA temperatures the PL efficiency reaches a maximum and then drops independently of N content. On the contrary, the blueshift experiences a rapid increase up to 700 deg. C (strong blueshift regime) and it saturates above this temperature (weak blueshift regime). Both these blueshift regimes are related to the nitrogen content in the SQWs but in different ways. In the strong blueshift regime, we could obtain activation energy for the blueshift process in the range of 1.25 eV, which increases with N content. Analysis with high-resolution x-ray diffraction (HRXRD) shows that the blueshift experienced in this regime is not due to a stoichiometric change in the QW. In the weak blueshift regime, the blueshift, which is only partly due to In outdiffusion, saturates more slowly the higher the N content. Annealing at the same temperature (600 deg. C) for a longer time shows that the blueshift saturates earlier than the PL intensity and that samples with higher nitrogen experience a larger blueshift. Only a small In outdiffusion for annealing at high temperatures (>650 deg. C) and long duration was observed. However, this modest stoichiometric change does not explain the large blueshift experienced by the GaInNAs SQWs. We conclude that the mechanism responsible for the drastic blueshift after

  14. Photoluminescence, electrical and structural properties of ZnO films, grown by ALD at low temperature

    NASA Astrophysics Data System (ADS)

    Przeździecka, E.; Wachnicki, Ł.; Paszkowicz, W.; Łusakowska, E.; Krajewski, T.; Łuka, G.; Guziewicz, E.; Godlewski, M.

    2009-10-01

    We report the first results of the low-temperature photoluminescence study on polycrystal zinc oxide (ZnO) films obtained by atomic layer deposition at 100 °C, 130 °C and 200 °C. These ZnO films, when studied 'as-grown', show a strong excitonic emission even at room temperature. Low-temperature (T = 9 K) photoluminescence reveals lack of defect-related bands and a sharp photoluminescence peak at 3.36 eV with full width at half maximum of 6 meV which is comparable with the value reported for good quality bulk ZnO crystals. The energy position of the excitonic peak scales with temperature according to standard formulas and give the Debye temperature of 963 ± 26 K. We show that optical properties of low-temperature 'as-grown' ZnO films are correlated with structural and electrical ones and that optical study can be a valuable tool for evaluation of quality of ZnO films for novel electronic applications.

  15. Study on the optical band gap and photoluminescence of PbMoO4 nano powder synthesized by an auto igniting combustion technique

    NASA Astrophysics Data System (ADS)

    Vidya, S.; Thomas, J. K.

    2015-02-01

    Nano crystalline PbMoO4 was synthesized through an auto-ignited combustion technique. The X-ray diffraction studies of PbMoO4 nanoparticles reveals that the as-prepared powder itself is single phase and possess tetragonal structure. The average particle size of the as-prepared powder calculated using scherrer formula is 28nm. Fourier transform Infrared spectrum shows that the as prepared powder itself is phase pure with no formation of secondary phase .The optical band gap determined from UV-Visible absorption spectra is 3.20eV.Photoluminescence spectra of the samples shows blue emission.

  16. Nanoparticle shape anisotropy and photoluminescence properties: Europium containing ZnO as a Model Case

    NASA Astrophysics Data System (ADS)

    Gerigk, Melanie; Ehrenreich, Philipp; Wagner, Markus R.; Wimmer, Ilona; Reparaz, Juan Sebastian; Sotomayor Torres, Clivia M.; Schmidt-Mende, Lukas; Polarz, Sebastian

    2015-10-01

    The precise control over electronic and optical properties of semiconductor (SC) materials is pivotal for a number of important applications like in optoelectronics, photocatalysis or in medicine. It is well known that the incorporation of heteroelements (doping as a classical case) is a powerful method for adjusting and enhancing the functionality of semiconductors. Independent from that, there already has been a tremendous progress regarding the synthesis of differently sized and shaped SC nanoparticles, and quantum-size effects are well documented experimentally and theoretically. Whereas size and shape control of nanoparticles work fairly well for the pure compounds, the presence of a heteroelement is problematic because the impurities interfere strongly with bottom up approaches applied for the synthesis of such particles, and effects are even stronger, when the heteroelement is aimed to be incorporated into the target lattice for chemical doping. Therefore, realizing coincident shape control of nanoparticle colloids and their doping still pose major difficulties. Due to a special mechanism of the emulsion based synthesis method presented here, involving a gelation of emulsion droplets prior to crystallization of shape-anisotropic ZnO nanoparticles, heteroelements can be effectively entrapped inside the lattice. Different nanocrystal shapes such as nanorods, -prisms, -plates, and -spheres can be obtained, determined by the use of certain emulsification agents. The degree of morphologic alterations depends on the type of incorporated heteroelement Mn+, concentration, and it seems that some shapes are more tolerant against doping than others. Focus was then set on the incorporation of Eu3+ inside the ZnO particles, and it was shown that nanocrystal shape and aspect ratios could be adjusted while maintaining a fixed dopant level. Special PL properties could be observed implying energy transfer from ZnO excited near its band-gap (3.3 eV) to the Eu3+ states

  17. Chemical vapor deposition synthesis and photoluminescence properties of ZnS hollow microspheres

    SciTech Connect

    Pi Zhengbang; Su Xiaolu; Yang Chao; Tian Xike Pei Fang; Zhang Suxin; Zhen Jianhua

    2008-08-04

    ZnS hollow microspheres were prepared via a facile template-free chemical vapor deposition (CVD) route using metallic zinc powders and sulphur sublimed as reactants. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectrometer (EDX). The results showed that the as-prepared ZnS hollow spheres had uniform size about 4-8 {mu}m in diameter. The growth mechanism of such interesting was discussed. The optical property of the products was also recorded by means of photoluminescence (PL) spectroscopy.

  18. Photoluminescent properties of Eu3+ doped electrospun CeO2 nanofibers

    NASA Astrophysics Data System (ADS)

    Fang, Dong; Zhang, Min; Luo, Zhiping; Cao, Tingting; Wang, Qing; Zhou, Zhi; Jiang, Ming; Xiong, Chuanxi

    2014-12-01

    In this study, CeO2 nanofibers and that doped with Eu3+ were prepared via a facile electrospinning route and annealed at different temperatures ranging from 500 to 900 °C. Their structures were investigated using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Photoluminescence properties of the nanofibers were studied in detail. It was found that the nanofibers with Eu% concentration of 0.67 mol.% and annealed at 700 °C exhibited the highest intensities of the luminescence peaks between 550 and 650 nm.

  19. Hydrothermal synthesis, crystal structures and photoluminescence properties of mixed europium-yttrium organic frameworks

    NASA Astrophysics Data System (ADS)

    Han, Yinfeng; Fu, Lianshe; Mafra, Luís; Shi, Fa-Nian

    2012-02-01

    Three mixed europium-yttrium organic frameworks: Eu2-xYx(Mel)(H2O)6 (Mel=mellitic acid or benzene-1,2,3,4,5,6-hexacarboxylic acid, x=0.38 1, 0.74 2, and 0.86 3) have been synthesized and characterized. All the compounds contain a 3-D net with (4, 8)-flu topology. The study indicates that the photoluminescence properties are effectively affected by the different ratios of europium and yttrium ions, the quantum efficiency is increased and the Eu3+ lifetime becomes longer in these MOFs than those of the Eu analog.

  20. Modification of Photoluminescence Properties of ZnO Island Films by Localized Surface Plasmons

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Li, Xue-Hong; Peng, Cheng-Xiao

    2012-10-01

    The modification of localised surface plasmons of photoluminescence properties of ZnO is studied. It is found that the ultraviolet emission is drastically enhanced, and the visible emission related to the defects is almost completely suppressed, after an Au layer of nanoparticles is deposited on the surface of ZnO island films. This pronounced change in PL spectra is attributed to the efficient electron transfer via the coupling of localised surface plasmons at the interface between the Au nanoparticle layer and ZnO films.

  1. Synthesis and Photoluminescent Properties of Eu²⁺-Doped BaSiF₆ Nanoparticles.

    PubMed

    Zhao, Xin; Hua, Ruinian; Zhang, Wei; Zhao, Jun; Tang, Dongxin; Sun, Zhengang

    2016-01-01

    By adjusting the molar ratio of oleic acid (OA), oleylamine (OM), and 1-octadecene (OD) ligands in reaction solution, Eu²⁺-doped BaSiF₆ nanoparticles were synthesized using a thermal decomposition synthesis route. Eu²⁺ ions have been successfully doped into BaSiF₆ host lattice and strong 4f-4f line emission of the Eu²⁺ in BaSiF₆ matrix is observed. Meanwhile, the photoluminescent (PL) properties of BaSiF₆:Eu²⁺ nanoparticles doping Eu²⁺ ions at different concentrations were also studied. PMID:27398531

  2. Time-resolved photoluminescence properties of semiconductor quantum dot superlattices of different microcrystal shapes

    SciTech Connect

    Chae, Weon-Sik Choi, Eunjin; Ku Jung, Yun; Jung, Jin-Seung; Lee, Jin-Kyu

    2014-04-14

    We report time-resolved photoluminescence properties on semiconductor quantum dot (QD) superlattices (SLs) using PL lifetime imaging microscopy at a single particle level. PL lifetime imaging technique clearly reveals that different shaped QD SL microcrystals have different time-resolved PL characteristics. The faceted SL microcrystals consisted of well-organized QDs showed faster recombination rates than those of the spherical microparticles including randomly organized QDs, which can be explained by the different degree of energetic couplings among component QDs due to different packing fraction.

  3. Three new Ag(I) coordination architectures based on mixed ligands: Syntheses, structures and photoluminescent properties

    SciTech Connect

    Li, Yamin; Xiao, Changyu; Li, Shu; Chen, Qi; Li, Beibei; Liao, Qian; Niu, Jingyang

    2013-04-15

    Three new silver (I) coordination complexes, [Ag{sub 2}(1,2-bdc)(phdat)]{sub n} (1), [Ag{sub 2}(NO{sub 2}-bdc)(phdat)]{sub n} (2), [Ag{sub 4}(nta){sub 3}(phdat)NO{sub 3}]{sub n} (3) (1,2-bdc=phthalic acid dianion, NO{sub 2}-bdc=5-nitro-1,3-benzenedicarboxylic acid dianion, nta=nicotinic acid anion, phdat=2,4-diamine-6-phenyl-1,3,5-triazine) have been hydrothermally synthesized by the reactions of silver nitrate and phdat with the homologous ligands 1,2-H{sub 2}bdc, NO{sub 2}-H{sub 2}bdc, and Hnta, respectively, and characterized by single-crystal X-ray diffractions, IR spectra, elemental analyses thermogravimetric analyses (TGA). The compound 1 exhibits a chiral 3D network with cbs/CrB self-dual topological net, which contains two kinds of single helical chains. For compound 2, the 3D network is comprised of two kinds of similar 2D sheets with the topological symbol of sql-type packed in AABBAA mode by Ag–N/O weakly contacts. And compound 3 has 2D double layer architecture, consisting of the 2D plane with hcb-type topological symbol connected by Ag–O weakly coordinations. The photoluminescent properties associated with the crystal structures of three compounds have also been measured. - Graphical abstract: Three new silver(I) coordination complexes 1–3 have been synthesized and characterized by single-crystal X-ray diffractions, IR spectra, elemental analyses, thermogravimetric analyses (TGA) and photoluminescent spectra. Highlights: ► The compound 1 exhibits a novel chiral 3D network with two kinds of single helical chains. ► 3D or 2D new Ag coordination complexes. ► The photoluminescent properties have been measured.

  4. Photoluminescence and radioluminescence properties of MnO-doped SnO-ZnO-P2O5 glasses

    NASA Astrophysics Data System (ADS)

    Masai, Hirokazu; Hino, Yusuke; Yanagida, Takayuki; Fujimoto, Yutaka

    2015-04-01

    In this study, the photoluminescence and radioluminescence properties of MnO-doped SnO-ZnO-P2O5 glasses are examined. We have confirmed that linear dose-dependence and radioluminescence emission decay depend on Mn2+ concentration. Energy transfer from donor Sn2+ center to acceptor Mn2+ center is observed in both photoluminescence and radioluminescence processes, and the energy transfer efficiency is more than 90% when the Mn2+/Sn2+ ratio is 5. Since emission intensity of Mn2+ is higher than that of Sn2+ in radioluminescence compared to photoluminescence, it is suggested that energy transfer from the host matrix to Mn2+ center by X-ray occurred preferentially over energy transfer to Sn2+ center. The present results suggest that the conventional parity rule for photoluminescence is not always adaptable for radioluminescence, although emission-related energy levels are the same for both the processes.

  5. Geometrical, response, and gap properties of Lindbladians

    NASA Astrophysics Data System (ADS)

    Albert, Victor V.; Bradlyn, Barry; Fraas, Martin; Jiang, Liang

    We study Lindbladians admitting multi-dimensional steady-state subspaces (SSS) which can be used to store, protect, and process quantum information. We derive an analytical formula for the left eigenmatrices of such Lindbladians corresponding to purely imaginary eigenvalues. This formula resolves how Lindbladian evolution affects perturbative response and geometrical features of the SSS and allows us to generalize recent work to all types of SSS. We show that Hamiltonian and certain jump operator perturbations induce, to first order, exclusively unitary evolution on the SSS. Similarly, the holonomy (generalization of geometric phase) induced on the SSS after adiabatic traversal of a closed path in parameter space is unitary. We derive a new Riemannian metric tensor in parameter space induced by one type of SSS, generalizing the Fubini-Study metric to Lindbladians possessing one or more mixed steady states. We derive a Kubo formula governing linear response of the SSS to Hamiltonian perturbations. Finally, we show that the energy scale governing leakage out of the SSS is different from the conventional Lindbladian dissipative gap.

  6. Green synthesis of magnesium ion incorporated nanocrystalline hydroxyapatite and their mechanical, dielectric and photoluminescence properties

    SciTech Connect

    Arul, K. Thanigai; Kolanthai, Elayaraja; Manikandan, E.; Bhalerao, G.M.; Chandra, V. Sarath; Ramya, J. Ramana; Mudali, U. Kamachi; Nair, K.G.M.; Kalkura, S.Narayana

    2015-07-15

    Highlights: • Rapid technique to synthesize nanorods of magnesium ion incorporated hydroxyapatite. • Enhanced electrical and mechanical properties. • Improved photoluminescence and wettability on magnesium incorporation. • Increased in vitro bioactivity. - Abstract: Nanocrystalline hydroxyapatite (HAp-Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2,} 35 nm) and magnesium (Mg{sup 2+}) ion incorporated HAp were synthesized by microwave technique. XRD (X-ray diffraction), FTIR (Fourier transform infrared spectroscopy), FE-HRTEM (Field emission high resolution transmission electron microscopy), DLS (dynamic light scattering), EDXRF (energy dispersive X-ray fluorescence spectrometry), microhardness, permittivity and alternating current (ac) conductivity, besides the PL (photoluminescence), wettability and in vitro bioactivity of the samples were analysed. EDXRF revealed the Mg{sup 2+} ion incorporation in HAp. The Mg{sup 2+} ion incorporation did not alter the phase but drastically reduced the crystallite size and particle size respectively by 48% and 32%. There was enhanced microhardness (24%) at low level (<13%) and decreased zeta potential of Mg{sup 2+} ion incorporation. The permittivity, ac conductivity, PL, wettability and in vitro bioactivity were enhanced on Mg{sup 2+} ion incorporation. These properties enable them to be a promising candidate for wound healing, bone replacement applications and also as a biosensor.

  7. Photoluminescence and thermoluminescence properties of Y3(Al,Ga)5O12:Tb3+ phosphor

    NASA Astrophysics Data System (ADS)

    Yousif, A.; Som, S.; Swart, H. C.

    2016-01-01

    A comparative study of the structural, photoluminescence (PL) and thermoluminescence (TL) properties of Y3(Al,Ga)5O12:Tb3+ phosphor powder was performed. The scanning electron microscope images showed that the phosphor particles were agglomerated and irregular in shape. The bigger particles consisted of smaller spherically shaped agglomerated particles ranging in size between 0.5 and 1 μm. The UV-VUV synchrotron radiation was used to study the luminescence properties of the phosphor. The TL study was performed after the sample was irradiated by γ-rays obtained from a 60Co target in the dose range of 10-50 Gy. The effect of heating rate on the TL glow curves and trapping parameters was also calculated. The correlation between PL and TL was explored.

  8. Photoluminescence properties of anodic alumina for application in optical sensors using SERS

    NASA Astrophysics Data System (ADS)

    Gasenkova, I. V.; Mukhurov, N. I.; Zhvavyi, S. P.

    2011-05-01

    The results of optical properties study of porous aluminum oxide films, fabricated by anodizing in a water solution of a sulfuric acid and modified by thermal annealing on air at temperature T>=800°C are reported. On the basis of the comparative analysis of the received data it is shown that a photoluminescence in near UV and visible regions for aluminum oxide anodized in a sulfuric acid solution originates from the divacancies of oxygen (F2, F+2 and F2+2 centers) and sulfates - ions do not render essential influence on luminescent properties AOA in researched spectral area. For samples annealed at T = 1300 °C, intensive narrow strips determined *see abstract on paper* by the radiative transitions (2E --> 4A2) in ions of Mn4+ (678 nm) and Cr3+ (694 nm), replacing ions of Al3+ in octahedral positions of α-Al2O3

  9. [Photoluminescent and electroluminescent properties of a new rare earth terbium complex].

    PubMed

    Wang, Li; Zhang, Xi-qing; Lin, Peng; Xiong, De-pin; Huang, Shi-hua; Yu, Tian-zhi

    2004-06-01

    Pure green and narrowbandwidth emission from an organic electroluminescent device was presented by using arare earth terbium (III) complex as the emissive layer. The structure of the device was ITO/PVK/Tb/PBD/LiF/Al. It was proved that this new kind of rare earth complex has excellent photoluminescent and electroluminescent properties. The electroluminescent spectrum of the device was very similar to that of the terbium (III) complex film. The electroluminescent mechanism of the device was proposed by measuring and analyzing the spectra and electroluminescent property of the device. It is proposed that the excited carriers of PVK and PBD were captured by Tb3+ and light was emitted when the electrons and holes recombined at Tb3+. PMID:15766172

  10. Photon absorption and emission properties of 7 Å SiC nanoclusters: Electronic gap, surface state, and quantum size effect

    NASA Astrophysics Data System (ADS)

    Guo, Xiaoxiao; Chen, Xifang; Fan, Baolu; Zhang, Yumeng; Fan, Jiyang

    2016-07-01

    People know little experimentally about the physical properties of the SiC nanoclusters with sizes of a couple of angstroms. Herein, we study the electronic structure and light absorption/emission properties of the SiC nanoclusters with an average diameter of 7 Å that are fabricated by diminishing the sizes of the SiC microcrystals under high pressure and high temperature. The results reveal that the SiC nanoclusters have an indirect energy gap of 5.1 eV. Unlike the case of larger SiC nanocrystals, the luminescence of the SiC nanoclusters is dominated by two types of oxygen-related surface defects, and the maximum of their photoluminescence/photoluminescence excitation spectrum lies at 4.1/3.3 and 3.8/3.0 eV, respectively. The energy gap of the SiC nanoparticles with reference to bulk value is found to be inversely proportional to the diameter to the power 0.97, which shows slower increase of energy gap with decreasing size than what is predicted by using the first-principles calculations.

  11. Probing the photoluminescence properties of gold nanoclusters by fluorescence lifetime correlation spectroscopy

    SciTech Connect

    Yuan, C. T. Lin, T. N.; Shen, J. L.; Lin, C. A.; Chang, W. H.; Cheng, H. W.; Tang, J.

    2013-12-21

    Gold nanoclusters (Au NCs) have attracted much attention for promising applications in biological imaging owing to their tiny sizes and biocompatibility. So far, most efforts have been focused on the strategies for fabricating high-quality Au NCs and then characterized by conventional ensemble measurement. Here, a fusion single-molecule technique combining fluorescence correlation spectroscopy and time-correlated single-photon counting can be successfully applied to probe the photoluminescence (PL) properties for sparse Au NCs. In this case, the triplet-state dynamics and diffusion process can be observed simultaneously and the relevant time constants can be derived. This work provides a complementary insight into the PL mechanism at the molecular levels for Au NCs in solution.

  12. Enhancement of field emission and photoluminescence properties of graphene-SnO2 composite nanostructures.

    PubMed

    Ding, Jijun; Yan, Xingbin; Li, Jun; Shen, Baoshou; Yang, Juan; Chen, Jiangtao; Xue, Qunji

    2011-11-01

    In this study, the SnO(2) nanostructures and graphene-SnO(2) (G-SnO(2)) composite nanostructures were prepared on n-Si (100) substrates by electrophoretic deposition and magnetron sputtering techniques. The field emission of SnO(2) nanostructures is improved largely by depositing graphene buffer layer, and the field emission of G-SnO(2) composite nanostructures can also further be improved by decreasing sputtering time of Sn nanoparticles to 5 min. The photoluminescence (PL) spectra of the SnO(2) nanostructures revealed multipeaks, which are consistent with previous reports except for a new peak at 422 nm. Intensity of six emission peaks increased after depositing graphene buffer layer. Our results indicated that graphene can also be used as buffer layer acting as interface modification to simultaneity improve the field emission and PL properties of SnO(2) nanostructures effectively. PMID:21967167

  13. Large-scale Synthesis of β-SiC Nanochains and Their Raman/Photoluminescence Properties

    PubMed Central

    2011-01-01

    Although the SiC/SiO2 nanochain heterojunction has been synthesized, the chained homogeneous nanostructure of SiC has not been reported before. Herein, the novel β-SiC nanochains are synthesized assisted by the AAO template. The characterized results demonstrate that the nanostructures are constructed by spheres of 25–30 nm and conjoint wires of 15–20 nm in diameters. Raman and photoluminescence measurements are used to explore the unique optical properties. A speed-alternating vapor–solid (SA-VS) growth mechanism is proposed to interpret the formation of this typical nanochains. The achieved nanochains enrich the species of one-dimensional (1D) nanostructures and may hold great potential applications in nanotechnology.

  14. Improved photoluminescence property of CTAB assisted polyaniline-AlZnO nanocomposite

    NASA Astrophysics Data System (ADS)

    Mitra, Mousumi; Kargupta, Kajari; Ganguly, Saibal; Banerjee, Dipali

    2015-06-01

    Polyaniline-Al doped ZnO ((PANI-AlZnO:: 70:30) nanocomposite was prepared via in situ chemical oxidative polymerization, while the hexagonal powder of AlZnO was synthesized via sol-gel technique, using Hexadecyltrimethylammonium bromide (CTAB) as a capping agent. The prepared nanocomposite was characterized by High resolution transmission electron microscopy (HRTEM), EDAX, X-ray diffraction (XRD) and Fourier transforms infrared (FTIR) spectra. The optical property of the nanomaterials is examined by photoluminescence (PL) spectra analysis. The XRD pattern confirms the formation of Al doped ZnO as well as PANI. The HRTEM images of the composite showed the formation of hexagonal AlZnO embedded in polyaniline matrix. EDAX spectrum shows the compositional analysis of the nanocomposite. FTIR spectra confirm the formation of nanocomposite of PANI and hexagonal AlZnO. The PL intensity of the nanocomposite is improved as compared to pure AlZnO.

  15. Chemical doping modulation of nonlinear photoluminescence properties in monolayer MoS2

    NASA Astrophysics Data System (ADS)

    Mouri, Shinichiro; Miyauchi, Yuhei; Matsuda, Kazunari

    2016-05-01

    We demonstrate a simple modulation technique of nonlinear optical properties in monolayer (1L) MoS2 via chemical doping. The strong nonlinear behavior of the exciton photoluminescence (PL) intensity is observed with increasing excitation power density for low-electron-density 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ)-doped 1L-MoS2, whereas the exciton PL intensity of as-prepared, heavily electron-doped 1L-MoS2 exhibits weak sublinear behavior. These results are attributable to an enhanced exciton–exciton annihilation rate for the excitons in F4TCNQ-doped 1L-MoS2 as the dominant decay pathway under strong optical excitation conditions.

  16. Surface enhanced Raman scattering and photoluminescence properties of catalytic grown ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Panda, S. K.; Jacob, C.

    2009-09-01

    Sword-like (diameter ranging from 40 nm to 300 nm) and needle-like zinc oxide (ZnO) nanostructures (average tip diameter ˜40 nm) were synthesized on annealed silver template over silicon substrate and directly on silicon wafer, respectively via thermal evaporation of metallic zinc followed by a thermal annealing in air. The surface morphology, microstructure, chemical analysis and optical properties of the grown samples were investigated by field emission scanning electron microscopy, X-ray diffraction, energy dispersive X-ray analysis, room temperature photoluminescence and Raman spectroscopy. The sword-like ZnO nanostructures grown on annealed silver template are of high optical quality compared to needle-like ZnO nanorods for UV emission and show enhanced Raman scattering.

  17. Defect induced photoluminescence and ferromagnetic properties of bio-compatible SWCNT/Ni hybrid bundles.

    PubMed

    Gupta, Vinay; Gupta, Bipin Kumar; Kotnala, R K; Narayanan, T N; Grover, Vaneet; Shah, Jyoti; Agrawal, Vikash; Chand, Suresh; Shanker, Virendra

    2011-10-15

    Designing of bio-compatible nanomagnets with multiple functionalities receives immense scientific attention due to their potential applications in bio-labeling, medical diagnosis and treatment. Here we report the synthesis of Nickel (Ni) incorporated single-walled carbon nanotube (SWCNT) hybrid and bio-compatible bundles having interesting magnetic and photoluminescence (PL) properties. The SWCNT exhibits a high-crystallinity and it has an average diameter of ∼1.7 nm. Ni particles of 10-20 nm were incorporated within the SWCNT bundles. These hybrid bundles exhibit PL and it is attributed to the presence of delocalized π electrons and their recombination at the defective sites of SWCNT. Magnetic characterization revealed that the SWCNT/Ni hybrid bundle possesses a high (50 Oe) coercivity compared to bulk Ni and a long range ferromagnetic ordering at room temperature. MTT-assay has been conducted to study the cytotoxicity of these hybrid nanostructures. PMID:21802691

  18. Large-scale synthesis well-dispersed ZnS microspheres and their photoluminescence, photocatalysis properties

    SciTech Connect

    Wang Xinjun Wan Fuquan; Han Kun; Chai Chunxia; Jiang Kai

    2008-12-15

    Large-scale and well-dispersed ZnS microspheres were prepared by a simple hydrothermal method using ZnSO{sub 4}{center_dot}7H{sub 2}O and SC(NH{sub 2}){sub 2} as main original reactant and poly(vinyl pyrrolidone) (PVP)(Mr {approx} 10,000) as the surfactant. The products were characterized by X-Ray diffraction, scanning electron microscopy and transmission electron microscopy. The growth process involves a special oriented aggregation of PVP stabilized ZnS nanoparticles into microspheres of 1.5 {approx} 2.0 {mu}m in sizes. The photocatalytic activity of as-prepared ZnS microsphere was evaluated by using methylene blue (MB) as a model organic compound. The optical properties of the products were also examined by means of photoluminescence (PL) spectroscopy.

  19. Photoluminescence properties of ZnTe layers grown by photo-assisted metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Gheyas, Syed Irfan; Ikejiri, Makoto; Ogata, Toshihiro; Ogawa, Hiroshi; Nishio, Mitsuhiro

    1994-12-01

    Effects of light illumination on the photoluminescence (PL) properties of ZnTe has been investigated by using epitaxial layers grown with different carrier gases, transport rate of source materials and light sources or by introducing triethylaluminum (TEAl) as a dopant. Free exciton emission can be observed in only the epitaxial layers grown with illumination under H 2 atmosphere, implying that the illumination is effective for the growth of good quality ZnTe layers. The illumination strengthens the transition due to excitons bound to donor impurities, namely Cl which is substituted into Te lattice site, at low substrate temperature. These effects are closely related to the use of photons having an energy higher than the bandgap of ZnTe. It seems that the photo-assisted metalorganic vapor phase epitaxy (MOVPE) technique also brings about the effective formation of Al donor by suppressing the generation of the complex of Al and Zn-vacancy in the ZnTe epitaxial layer.

  20. Improved photoluminescence property of CTAB assisted polyaniline-AlZnO nanocomposite

    SciTech Connect

    Mitra, Mousumi; Banerjee, Dipali; Kargupta, Kajari; Ganguly, Saibal

    2015-06-24

    Polyaniline-Al doped ZnO ((PANI-AlZnO:: 70:30) nanocomposite was prepared via in situ chemical oxidative polymerization, while the hexagonal powder of AlZnO was synthesized via sol-gel technique, using Hexadecyltrimethylammonium bromide (CTAB) as a capping agent. The prepared nanocomposite was characterized by High resolution transmission electron microscopy (HRTEM), EDAX, X-ray diffraction (XRD) and Fourier transforms infrared (FTIR) spectra. The optical property of the nanomaterials is examined by photoluminescence (PL) spectra analysis. The XRD pattern confirms the formation of Al doped ZnO as well as PANI. The HRTEM images of the composite showed the formation of hexagonal AlZnO embedded in polyaniline matrix. EDAX spectrum shows the compositional analysis of the nanocomposite. FTIR spectra confirm the formation of nanocomposite of PANI and hexagonal AlZnO. The PL intensity of the nanocomposite is improved as compared to pure AlZnO.

  1. Structural order effect in visible photoluminescence properties of nanocrystalline Si :H thin films

    NASA Astrophysics Data System (ADS)

    Chen, H.; Shen, W. Z.; Wei, W. S.

    2006-03-01

    We report room-temperature visible photoluminescence (PL) properties of highly ordered hydrogenated nanocrystalline Si(nc-Si :H) with good electrical performance. The PL profiles can be well reproduced by the model of Islam and Kumar [J. Appl. Phys. 93, 1753 (2003)], incorporating the effects of quantum confinement and localized surface states, as well as a log-normal crystallite size distribution. Raman, PL, and electrical results consistently reveal that improvement of structural order within nc-Si :H is beneficial to enhance the PL efficiency. Owing to adequate order, strong visible PL and high electron mobility can coexist in nc-Si :H, which may provide possibilities in Si-based optoelectronics.

  2. Photoluminescence properties of silicon nanocrystals interacting with gold nanoparticles via exciton-plasmon coupling

    NASA Astrophysics Data System (ADS)

    Potrick, Karsten; Huisken, Friedrich

    2015-03-01

    The photoluminescence (PL) properties of silicon nanocrystals (Si NCs) deposited on gold nanostructures have been studied regarding PL intensity and lifetime. In contrast to most investigations, which attempt to optimize the overlap between the plasmon resonance and the Si NCs' PL band, we chose much smaller gold nanoparticles to achieve an improved exciton-plasmon coupling. PL enhancements of up to 20 were observed near the plasmon resonance. In the maximum of the PL band at 710 nm, we determined a PL enhancement of ˜4 while the average PL lifetime was found to increase from 45 to 66 μ s . The experimental observations were successfully explained with a model invoking bidirectional energy transfer between excitonic and plasmonic states, being operative in addition to the normal exciton recombination rate enhancement.

  3. Hydrothermal synthesis, crystal structures and photoluminescence properties of mixed europium-yttrium organic frameworks

    SciTech Connect

    Han Yinfeng; Fu Lianshe; Mafra, Luis; Shi, Fa-Nian

    2012-02-15

    Three mixed europium-yttrium organic frameworks: Eu{sub 2-x}Y{sub x}(Mel)(H{sub 2}O){sub 6} (Mel=mellitic acid or benzene-1,2,3,4,5,6-hexacarboxylic acid, x=0.38 1, 0.74 2, and 0.86 3) have been synthesized and characterized. All the compounds contain a 3-D net with (4, 8)-flu topology. The study indicates that the photoluminescence properties are effectively affected by the different ratios of europium and yttrium ions, the quantum efficiency is increased and the Eu{sup 3+} lifetime becomes longer in these MOFs than those of the Eu analog. - Graphical abstract: Three mixed europium and yttrium organic frameworks: Eu{sub 2-x}Y{sub x}(Mel)(H{sub 2}O){sub 6} (Mel=mellitic acid) have been synthesized and characterized. All the compounds contain a 3-D net with (4, 8)-flu topology. The study indicates that the photoluminescence properties are effectively affected by the different ratios of europium and yttrium ions, the quantum efficiency is increased and the Eu{sup 3+} lifetime becomes longer in these MOFs than those of the Eu analog. Highlights: Black-Right-Pointing-Pointer Three (4, 8)-flu topological mixed Eu and Y MOFs were synthesized under mild conditions. Black-Right-Pointing-Pointer Metal ratios were refined by the single crystal data consistent with the EDS analysis. Black-Right-Pointing-Pointer Mixed Eu and Y MOFs show longer lifetime and higher quantum efficiency than the Eu analog. Black-Right-Pointing-Pointer Adding inert lanthanide into luminescent MOFs enlarges the field of luminescent MOFs.

  4. Functional Properties of Dendritic Gap Junctions in Cerebellar Golgi Cells.

    PubMed

    Szoboszlay, Miklos; Lőrincz, Andrea; Lanore, Frederic; Vervaeke, Koen; Silver, R Angus; Nusser, Zoltan

    2016-06-01

    The strength and variability of electrical synaptic connections between GABAergic interneurons are key determinants of spike synchrony within neuronal networks. However, little is known about how electrical coupling strength is determined due to the inaccessibility of gap junctions on the dendritic tree. We investigated the properties of gap junctions in cerebellar interneurons by combining paired somato-somatic and somato-dendritic recordings, anatomical reconstructions, immunohistochemistry, electron microscopy, and modeling. By fitting detailed compartmental models of Golgi cells to their somato-dendritic voltage responses, we determined their passive electrical properties and the mean gap junction conductance (0.9 nS). Connexin36 immunofluorescence and freeze-fracture replica immunogold labeling revealed a large variability in gap junction size and that only 18% of the 340 channels are open in each plaque. Our results establish that the number of gap junctions per connection is the main determinant of both the strength and variability in electrical coupling between Golgi cells. PMID:27133465

  5. Time resolved photoluminescence spectroscopy of narrow gap Hg1-xCdxTe/CdyHg1-yTe quantum well heterostructures

    NASA Astrophysics Data System (ADS)

    Morozov, S. V.; Rumyantsev, V. V.; Antonov, A. V.; Kadykov, A. M.; Maremyanin, K. V.; Kudryavtsev, K. E.; Mikhailov, N. N.; Dvoretskii, S. A.; Gavrilenko, V. I.

    2014-07-01

    Photoluminescence (PL) spectra and kinetics of narrow gap Hg1-xCdxTe/CdyHg1-yTe quantum well (QW) heterostructures grown by molecular beam epitaxy technique are studied. Interband PL spectra are observed from 18 K up to the room temperature. Time resolved studies reveal an additional PL line with slow kinetics (7 μs at 18 K) related to deep defect states in barrier layers. These states act as traps counteracting carrier injection into QWs. The decay time of PL signal from QW layers is about 5 μs showing that gain can be achieved at wavelengths 10-20 μm by placing such QWs in HgCdTe structures with waveguides.

  6. Temperature dependence of the fundamental band gap parameters in cadmium-rich ZnxCd1-xSe using photoluminescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Gupta, Lalita; Rath, S.; Abbi, S. C.; Jain, F. C.

    2003-10-01

    Thin films of ternary ZnxCd1-xSe were deposited on GaAs (100) substrate using metalorganic- chemical-vapour-deposition (MOCVD) technique. Temperature dependence of the nearband- edge emission from these Cd-rich ZnxCd1-x Se (for x _ 0_025, 0.045) films has been studied using photoluminescence spectroscopy. Relevant parameters that describe temperature variation of the energy and broadening of the fundamental band gap have been evaluated using various models including the two-oscillator model, the Bose-Einstein model and the Varshni model. While all these models suffice to explain spectra at higher temperatures, the two-oscillator model not only explains low temperature spectra adequately but also provides additional information concerning phonon dispersion in these materials.

  7. Tuning photoluminescence and surface properties of carbon nanodots for chemical sensing

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaomin; Pan, Yi; Fang, Yaning; Zhang, Lulu; Chen, Junying; Yi, Changqing

    2015-12-01

    Obtaining tunable photoluminescence (PL) with improved emission properties is crucial for successfully implementing fluorescent carbon nanodots (fCDs) in all practical applications such as multicolour imaging and multiplexed detection by a single excitation wavelength. In this study, we report a facile hydrothermal approach to adjust the PL peaks of fCDs from blue, green to orange by controlling the surface passivation reaction during the synthesis. This is achieved by tuning the passivating reagents in a step-by-step manner. The as-prepared fCDs with narrow size distribution show improved PL properties with different emission wavelengths. Detailed characterization of fCDs using elemental analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy suggested that the surface chemical composition results in this tunable PL emission. Surface passivation significantly alters the surface status, resulting in fCDs with either stronger surface oxidation or N element doping that ultimately determine their PL properties. Further experiments suggested that the as-prepared orange luminescent fCDs (O-fCDs) were sensitive and specific nanosensing platforms towards Fe3+ determination in a complex biological environment, emphasizing their potential practical applications in clinical and biological fields.Obtaining tunable photoluminescence (PL) with improved emission properties is crucial for successfully implementing fluorescent carbon nanodots (fCDs) in all practical applications such as multicolour imaging and multiplexed detection by a single excitation wavelength. In this study, we report a facile hydrothermal approach to adjust the PL peaks of fCDs from blue, green to orange by controlling the surface passivation reaction during the synthesis. This is achieved by tuning the passivating reagents in a step-by-step manner. The as-prepared fCDs with narrow size distribution show improved PL properties with different emission wavelengths. Detailed

  8. Insights into photoluminescence property and photocatalytic activity of cubic and rhombohedral ZnIn{sub 2}S{sub 4}

    SciTech Connect

    Shen Shaohua; Guo Penghui; Zhao Liang; Du Yuanchang; Guo Liejin

    2011-08-15

    Cubic and rhombohedral ZnIn{sub 2}S{sub 4} were synthesized by thermal sulfidation of Zn-In mixed oxide precursor in H{sub 2}S atmosphere at different temperatures. Cubic ZnIn{sub 2}S{sub 4} was obtained when Zn-In mixed oxide precursor was sulfurized at 400 deg. C. With sulfidation temperature increasing from 400 to 800 deg. C, the crystal phase of ZnIn{sub 2}S{sub 4} gradually turned from cubic to rhombohedral, which was demonstrated by different analysis techniques such as XRD, Raman, SEM, etc. UV-vis absorption spectra indicated that cubic ZnIn{sub 2}S{sub 4} displayed better light absorption property than rhombohedral ZnIn{sub 2}S{sub 4}, with band gaps calculated to be 2.0 and 2.5 eV, respectively. However, under visible light irradiation, rhombohedral ZnIn{sub 2}S{sub 4} photocatalyzed H{sub 2} evolution from aqueous sodium sulfite/sulfide solution efficiently, whereas cubic ZnIn{sub 2}S{sub 4} was not active for this reaction. The photoluminescence property revealed the different dynamics of photogenerated carriers, which made a predominant contribution to the increasing photocatalytic performances of ZnIn{sub 2}S{sub 4} with crystal phase turning from cubic to rhombohedral. - Graphical Abstract: Rhombohedral ZnIn{sub 2}S{sub 4} showed a superior photocatalytic activity for H{sub 2} evolution than cubic ZnIn{sub 2}S{sub 4}, which was proved to be related with their different dynamics of photogenerated carriers. Highlights: > Cubic and rhombohedral ZnIn{sub 2}S{sub 4} were synthesized by thermal sulfidation. > Rhombohedral ZnIn{sub 2}S{sub 4} could photocatalyze H{sub 2} evolution efficiently. > The dynamics of photogenerated carriers affected the photocatalytic activity.

  9. Structural and photoluminescence properties of Eu(3+) doped α-Ag2WO4 synthesized by the green coprecipitation methodology.

    PubMed

    Pinatti, Ivo M; Nogueira, Içamira C; Pereira, Wyllamanney S; Pereira, Paula F S; Gonçalves, Rosana F; Varela, José A; Longo, Elson; Rosa, Ieda L V

    2015-10-28

    Europium doped silver tungstates α-Ag2-3xEuxWO4 (x = 0, 0.0025, 0.005, 0.0075 and 0.01 mol) were synthesized by the coprecipitation method at 90 °C for 30 minutes. These crystals were structurally characterized by means of X-ray diffraction (XRD), Rietveld refinement, and micro-Raman (MR) and Fourier transformed infrared (FT-IR) spectroscopies. Field emission scanning electron microscopy (FE-SEM) images were employed to observe the shape of the crystals. The optical properties were investigated by ultraviolet-visible (UV-vis) absorption and photoluminescence (PL) measurements. The XRD pattern indicated structural organization at a long range for all undoped and Eu-doped samples, while MR and FT-IR revealed that the presence of the Eu(3+) ions favors the structural organization at a short range. The Rietveld refinement showed that all the crystals are monophasic with an orthorhombic structure and the Pn2[combining macron]n space group. The refined lattice parameters and atomic positions were employed to model the WO6 and AgOn (n = 2, 4, 6 and 7) polyhedra in the unit cell. FE-SEM analysis revealed nanorod-like microcrystals with growth of metallic silver on the surface. Further, the UV-vis absorption spectra indicated the existence of intermediary energy levels within the band gap. PL spectra showed a broad band related to the [WO6] group and characteristic narrow peaks due to the f-f transitions of Eu(3+) as a result of efficient energy transfer from the matrix. Also, the emission line shape transitions from (5)D0 to (7)FJ (J = 0-4) levels of the Eu(3+) were noticed. Among the samples, the most intense photoluminescence results were observed for the α-Ag2-3xEuxWO4 (x = 0.0075) sample. Lifetime decays support that the Eu(3+) ions occupy at least two crystallographic sites. CIE coordinates confirmed the colors of the emission spectra which classify this material as a potential phosphor in the visible range. PMID:26394903

  10. New nanostructured zinc phosphite templated by cetyltrimethylammonium cations: synthesis, crystal structure, adsorption, and photoluminescence properties.

    PubMed

    Wang, Chih-Min; Chang, Tsung-Yuan; Chiu, Cheng-Wei; Lin, Hsiu-Mei; Lii, Kwang-Hwa

    2014-04-01

    Nanostructured zinc phosphite templated by cetyltrimethylammonium (CTA(+)) cations was synthesized using a hydro(solvo)thermal method. This is the first example of a crystalline metal phosphite containing long carbon tails of the CTA(+) ions as templates in its structure, as is structurally characterized by single-crystal X-ray diffraction. The 2D inorganic structures with 4.8(2) topologies are constructed from the interconnection of tetrahedral ZnO3Br and HPO3 units, which are sandwiched between CTA(+) ion surfactants in a packing behavior of a largely lamellar liquid-crystalline structure to extend the interlayer d spacing to 28.05 Å. Adsorption experiment shows selective adsorption properties of 1-naphthol and a adsorption capacity of 0.17 mmol/mmol (CTA)ZnBr(HPO3). This compound has potential as an adsorbent for the removal of 1-naphthol pollutant from wastewater. In addition, the naphthol-adsorbed sample shows interesting luminescent properties that are different from that of an as-synthesized sample. The crystal structure, thermal stability, IR spectrum, adsorption, and photoluminescence properties have been studied. PMID:24661090

  11. EPR and photoluminescence properties of Mn2+ doped CdS nanoparticles synthesized via co-precipitation method.

    PubMed

    Gupta, Atul K; Kripal, Ram

    2012-10-01

    The structural properties of Mn doped CdS (Mn:CdS) nanoparticles (NPs) are studied using X-ray diffraction (XRD), Transmission electron microscopy (TEM), Ultraviolet-visible (UV-vis), Photoluminescence (PL), Raman and Electron paramagnetic resonance (EPR) spectroscopy. XRD analysis shows the nanostructure with 2-4 nm of average crystallite size. The planes (110), (103) and (112) in XRD pattern distinguish the wurtzite structure of the Mn:CdS NPs. The intensity of the plane (102) increases as the doping concentration of Mn(2+) increases. UV-vis absorption spectra show blue shift as compared to bulk CdS. The optical band gap energy of Mn(2+) (0, 0.35, 0.70 and 1.35 at.%) doped CdS NPs corresponding to absorption edge are found to be 5.29, 5.28, 5.25 and 5.21 eV, respectively. The intensity of luminescence is changing with the concentration of Mn(2+) doped in CdS NPs. Raman spectra show blue shift in fundamental optical phonon mode (1LO) as well as second optical phonon mode (2LO) as compared to bulk CdS. The intensity ratio of the 2LO to 1LO modes slightly decreases as Mn(2+) concentration increases. EPR shows the existence of Mn(2+) with different local structures in CdS nanoparticles. The values of spectroscopic splitting factor (g) and hyperfine interaction constant (A) decrease as Mn(2+) concentration increases in CdS NPs. PMID:22868335

  12. Semiconducting tin and lead iodide perovskites with organic cations: phase transitions, high mobilities, and near-infrared photoluminescent properties.

    PubMed

    Stoumpos, Constantinos C; Malliakas, Christos D; Kanatzidis, Mercouri G

    2013-08-01

    A broad organic-inorganic series of hybrid metal iodide perovskites with the general formulation AMI3, where A is the methylammonium (CH3NH3(+)) or formamidinium (HC(NH2)2(+)) cation and M is Sn (1 and 2) or Pb (3 and 4) are reported. The compounds have been prepared through a variety of synthetic approaches, and the nature of the resulting materials is discussed in terms of their thermal stability and optical and electronic properties. We find that the chemical and physical properties of these materials strongly depend on the preparation method. Single crystal X-ray diffraction analysis of 1-4 classifies the compounds in the perovskite structural family. Structural phase transitions were observed and investigated by temperature-dependent single crystal X-ray diffraction in the 100-400 K range. The charge transport properties of the materials are discussed in conjunction with diffuse reflectance studies in the mid-IR region that display characteristic absorption features. Temperature-dependent studies show a strong dependence of the resistivity as a function of the crystal structure. Optical absorption measurements indicate that 1-4 behave as direct-gap semiconductors with energy band gaps distributed in the range of 1.25-1.75 eV. The compounds exhibit an intense near-IR photoluminescence (PL) emission in the 700-1000 nm range (1.1-1.7 eV) at room temperature. We show that solid solutions between the Sn and Pb compounds are readily accessible throughout the composition range. The optical properties such as energy band gap, emission intensity, and wavelength can be readily controlled as we show for the isostructural series of solid solutions CH3NH3Sn(1-x)Pb(x)I3 (5). The charge transport type in these materials was characterized by Seebeck coefficient and Hall-effect measurements. The compounds behave as p- or n-type semiconductors depending on the preparation method. The samples with the lowest carrier concentration are prepared from solution and are n-type; p

  13. Structure and photoluminescence properties of carbon nanotip-vertical graphene nanohybrids

    NASA Astrophysics Data System (ADS)

    Wang, B. B.; Zhu, K.; Ostrikov, K.; Shao, R. W.; Zheng, K.

    2016-01-01

    We report on the effective enhancement and tuning of photoluminescence (PL) by combining vertical graphene nanoflakes (VGs) and carbon nanotips (CNTPs). The VGs are grown on the vertical CNTPs by hot filament chemical vapor deposition in the methane environment, where the CNTPs are synthesized on silicon substrates by CH4-H2-N2 plasma-enhanced hot filament chemical vapor deposition. The results of field emission scanning electron microscopy, transmission electron microscopy, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy indicate that the VGs can be grown on the CNTP and silicon substrate surfaces with the orientation perpendicular to the surfaces of CNTPs and silicon substrates. The PL properties of VG, CNTP, and CNTP-VG structures are studied using a 325 nm line of He-Cd laser as the excitation source. The PL results indicate that the PL of VGs is enhanced by the CNTPs due to the increasing density of PL emitters, while the PL properties of the nanohybrid system can be tuned. Furthermore, the potential applications of CNTP-VG structures in optoelectronic devices are analyzed. These results contribute to the design of functional graphene-based materials and the development of next-generation optoelectronic devices.

  14. The photoluminescence properties of tri-colour silicoaluminate phosphors prepared from oil shale ash

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Song, Yanhua; Sheng, Ye; Zheng, Keyan; Ding, Shizhou; Yuan, Bo; Xu, Xuechun; Zou, Haifeng

    2015-09-01

    In this paper, high value-added tri-colour phosphors Ba0.96Mg1.88Si2O7:0.02Eu2+, 0.02Dy3+, 0.12Mn2+; CaSr0.995SiO4:0.005Eu2+ and Ba0.91MgAl10O17:0.09Eu2+ were prepared using the white carbon black (hereinafter referred to as WCB) and alumina extracted from oil shale ash as raw materials. The structure and luminescence properties of the samples were characterized by X-ray diffraction (XRD) and photoluminescent spectra. The results show that the red and green phosphors synthesized by WCB exhibited much weaker emission than the phosphors synthesized by pure chemical reagent silica, which is mainly due to the high content of iron in the WCB. After purifying the WCB under laboratory conditions, the luminescence properties were improved and close to that of pure chemical reagent. By comparing with the emission of the samples synthesized with chemical reagents, the results show that the products extracted from oil shale ash can be applied to synthesize luminescent materials which have potential applications in white-light ultraviolet (UV)-LED field.

  15. Effect of graphene on photoluminescence properties of graphene/GeSi quantum dot hybrid structures

    SciTech Connect

    Chen, Y. L.; Ma, Y. J.; Wang, W. Q.; Ding, K.; Wu, Q.; Fan, Y. L.; Yang, X. J.; Zhong, Z. Y.; Jiang, Z. M.; Chen, D. D.; Xu, F.

    2014-07-14

    Graphene has been discovered to have two effects on the photoluminescence (PL) properties of graphene/GeSi quantum dot (QD) hybrid structures, which were formed by covering monolayer graphene sheet on the multilayer ordered GeSi QDs sample surfaces. At the excitation of 488 nm laser line, the hybrid structure had a reduced PL intensity, while at the excitation of 325 nm, it had an enhanced PL intensity. The attenuation in PL intensity can be attributed to the transferring of electrons from the conducting band of GeSi QDs to the graphene sheet. The electron transfer mechanism was confirmed by the time resolved PL measurements. For the PL enhancement, a mechanism called surface-plasmon-polariton (SPP) enhanced absorption mechanism is proposed, in which the excitation of SPP in the graphene is suggested. Due to the resonant excitation of SPP by incident light, the absorption of incident light is much enhanced at the surface region, thus leading to more exciton generation and a PL enhancement in the region. The results may be helpful to provide us a way to improve optical properties of low dimensional surface structures.

  16. Enhanced UV absorbance and photoluminescence properties of ultrasound assisted synthesized gold doped ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Sahu, Dojalisa; Panda, N. R.; Acharya, B. S.; Panda, A. K.

    2014-06-01

    Au doped ZnO (ZnO:Au) nanostructures were synthesized by ultrasound assisted wet chemical method. The concentration of dopant was varied and both structural and optical properties of ZnO:Au were investigated. The crystal structure and morphology of the samples were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). These results showed the formation of nanorods of ZnO:Au having wurtzite structure and c-axis orientation. Gradual increase in crystallite size and bond length was also observed with the increase in gold concentration in ZnO intending the expansion of lattice after gold doping. The optical absorption measurements showed high ultraviolet (UV) absorbance property of ZnO:Au with sharp and intense absorption band in this region as compared to pristine ZnO. Photoluminescence (PL) measurements showed excitonic emission band of ZnO around 390 nm for both undoped and Au doped ZnO nanoparticles. Further, a strong emission around 467 nm was observed in the PL spectra of ZnO/ZnO:Au which was attributed to the transitions related to excess of oxygen vacancies. Interestingly, a new band was observed at 582 nm for doped ZnO samples which grew in intensity with doping concentration. This band was ascribed to the gold nanoparticle adsorbed on the surface of ZnO.

  17. Influence of annealing temperature on photoluminescence properties and optical constants of N-doped ZnO thin films grown on muscovite mica substrates

    NASA Astrophysics Data System (ADS)

    Kim, Younggyu; Leem, Jae-Young

    2015-11-01

    A sol-gel spin-coating method was used to synthesize N-doped ZnO (NZO) thin films on muscovite mica substrates; the films were then annealed at 200, 300, 400, and 500 °C. The effects of the annealing temperature on their photoluminescence properties and optical constants were investigated. All the films had strong UV emissions in their photoluminescence spectra, but the green emissions at ~2.4 eV were observed only for the annealed films. The average transmittance of all the films was about 80% in the visible range and the absorption edges in the UV range at 375 nm depended strongly on the annealing temperature. The optical band gap of the films decreased gradually as the annealing temperature was increased up to 400 °C, and the Urbach energy decreased significantly as the annealing temperature increased. Finally, the various optical constants, the dielectric constant, and the optical conductivity were measured for the un-annealed film and the film annealed at 500 °C.

  18. Optical Properties and Band Gap of Single- and Few-Layer MoTe2 Crystals

    NASA Astrophysics Data System (ADS)

    Aslan, Ozgur Burak; Ruppert, Claudia; Heinz, Tony

    2015-03-01

    Single- and few-layer crystals of exfoliated MoTe2 have been characterized spectroscopically by photoluminescence, Raman scattering, and optical absorption measurements. We find that MoTe2 in the monolayer limit displays strong photoluminescence. On the basis of complementary optical absorption results, we conclude that monolayer MoTe2 is a direct-gap semiconductor with an optical band gap of 1.10 eV. This new monolayer material extends the spectral range of atomically thin direct-gap materials from the visible to the near-infrared. Supported by the NSF through Grant DMR-1124894 for sample preparation and characterization by the O?ce of Naval Research for analysis. C.R. acknowledges support from the Alexander von Humboldt Foundation.

  19. Photoluminescence of heterostructures with GaP{sub 1−x}N{sub x} and GaP{sub 1−x−y}N{sub x}As{sub y} layers grown on GaP and Si substrates by molecular-beam epitaxy

    SciTech Connect

    Lazarenko, A. A. Nikitina, E. V.; Sobolev, M. S.; Pirogov, E. V.; Denisov, D. V.; Egorov, A. Yu.

    2015-04-15

    The structural and optical properties of heterostructures containing GaP{sub 1−x}N{sub x} ternary and GaP{sub 1−x−y}N{sub x}As{sub y} quaternary alloy layers are discussed. The heterostructures are grown by molecular-beam epitaxy on GaP and Si substrates. The structures are studied by the high-resolution X-ray diffraction technique and photoluminescence measurements in a wide temperature range from 10 to 300 K. In the low-temperature photoluminescence spectra of the alloys with a low nitrogen fraction (x < 0.007), two clearly resolved narrow lines attributed to the localized states of nitrogen pairs and the phonon replicas of these lines are observed.

  20. Citrate-Complexation Synthesis and Photoluminescence Properties of Y6MoO12:Eu Nanocrystalline.

    PubMed

    Li, Huaiyong; Pu, Xipeng; Yao, Shujuan; Wang, Xiaoqing; Noh, Hyeon Mi; Jeong, Jung Hyun

    2016-04-01

    Y6MoO12 doped with Eu3+ was synthesized using a citrate-complexation route, and was calcined at 800 °C and 1400 °C, respectively. The structure, morphology and photoluminescence (PL) properties of the samples, and their dependence on the crystallite size were investigated. XRD patterns indicate that the Y6MoO12:Eu3+ powder was obtained at both calcination temperatures, and had a cubic structure. The results also suggest that Y6MoO12:Eu3+ calcined at 800 °C was in the nanocrystalline phase, which was confirmed by the SEM microimage. The crystalline size was about 140 nm. Both phosphors could be excited via three channels: f-f excitation of Eu3+ by blue light, MoO groups excitation by near-UV light, and charge transfer state excitation of Eu3+ by UV light. Both samples yielded red light emissions dominated by the 5D0-7F2 transition at 613 nm. The excitation efficient of the three channels depended on the calcination temperature. The energy transfer from the MoO groups to the Eu3+ ions was more effective in the nanocrystalline phase. The temporal decay feature of the phosphor was also characterized. PMID:27451680

  1. Cation distribution and photoluminescence properties of Mn-doped ZnGa2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Jian; Duan, Xiulan; Zhang, Yang; Jiang, Huaidong

    2015-06-01

    Mn-doped ZnGa2O4 nanoparticles with the composition of MnxZn1-xGa2O4 (0≤x≤1) were prepared by the citrate sol-gel method. The cation distribution in the nanoparticles was studied by using X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). The results show that the nanoparticles with the size of 20-48 nm were obtained when the precursor was annealed at 600 °C or above, and the size increases with increasing annealing temperature. The cations (Ga3+, Zn2+ and Mn2+) occupy the tetrahedral (Td) sites as well as the octahedral (Oh) sites of spinel structure in the nanoparticles. Ga3+ ions are located in a large proportion at the octahedral sites and in a small proportion at the tetrahedral sites. The inversion parameter (two times the fraction of Ga3+ in the tetrahedral sites) increases with decreasing annealing temperature and Mn-enrichment. The luminescent properties were studied by using fluorescence spectrophotometer. The photoluminescence (PL) spectra exhibit green and red emissions with excitation wavelength of 304 nm, which is attributed to 4T1(4G)→6A1(6S) transition of Mn2+ ions in the tetrahedral and octahedral sites of MnxZn1-xGa2O4 nanoparticles, respectively.

  2. Photoluminescence and photocatalytic properties of rhombohedral CuGaO2 nanoplates

    PubMed Central

    Shi, Linlin; Wang, Fei; Wang, Yunpeng; Wang, Dengkui; Zhao, Bin; Zhang, Ligong; Zhao, Dongxu; Shen, Dezhen

    2016-01-01

    Rhombohedral phase CuGaO2 nanoplates with a diameter of about 10 μm were synthesized via low temperature hydrothermal method. Room temperature and low temperature photoluminescence of the obtained CuGaO2 nanoplates were characterized. CuGaO2 nanoplates exhibited blue emission at room temperature and free exciton emission were appeared at low temperature. The blue emission is originated from defects such as Cu vacancies, which is the possible origin of p-type conductivity. The appearance of free exciton emission can demonstrate the direct bandgap transition behavior of CuGaO2 nanoplates. The as-prepared p-type CuGaO2 nanoplates were further decorated by n-type ZnO nanoparticles via calcination method to fabricate p-n junction nanocomposites. The nanocomposites exhibited enhanced photocatalytic activity which can be ascribed to the effective separation of photogenerated carriers by the internal electrostatic field in the p-n junction region, and the enhanced light absorption properties resulted from sub-bandgap absorption effect of p-n junction. This work has offered a new insight into the design of p-n junction devices using p-type CuGaO2 nanoplates. PMID:26887923

  3. Photoluminescence and photocatalytic properties of rhombohedral CuGaO2 nanoplates.

    PubMed

    Shi, Linlin; Wang, Fei; Wang, Yunpeng; Wang, Dengkui; Zhao, Bin; Zhang, Ligong; Zhao, Dongxu; Shen, Dezhen

    2016-01-01

    Rhombohedral phase CuGaO2 nanoplates with a diameter of about 10 μm were synthesized via low temperature hydrothermal method. Room temperature and low temperature photoluminescence of the obtained CuGaO2 nanoplates were characterized. CuGaO2 nanoplates exhibited blue emission at room temperature and free exciton emission were appeared at low temperature. The blue emission is originated from defects such as Cu vacancies, which is the possible origin of p-type conductivity. The appearance of free exciton emission can demonstrate the direct bandgap transition behavior of CuGaO2 nanoplates. The as-prepared p-type CuGaO2 nanoplates were further decorated by n-type ZnO nanoparticles via calcination method to fabricate p-n junction nanocomposites. The nanocomposites exhibited enhanced photocatalytic activity which can be ascribed to the effective separation of photogenerated carriers by the internal electrostatic field in the p-n junction region, and the enhanced light absorption properties resulted from sub-bandgap absorption effect of p-n junction. This work has offered a new insight into the design of p-n junction devices using p-type CuGaO2 nanoplates. PMID:26887923

  4. Photoluminescence and photocatalytic properties of rhombohedral CuGaO2 nanoplates

    NASA Astrophysics Data System (ADS)

    Shi, Linlin; Wang, Fei; Wang, Yunpeng; Wang, Dengkui; Zhao, Bin; Zhang, Ligong; Zhao, Dongxu; Shen, Dezhen

    2016-02-01

    Rhombohedral phase CuGaO2 nanoplates with a diameter of about 10 μm were synthesized via low temperature hydrothermal method. Room temperature and low temperature photoluminescence of the obtained CuGaO2 nanoplates were characterized. CuGaO2 nanoplates exhibited blue emission at room temperature and free exciton emission were appeared at low temperature. The blue emission is originated from defects such as Cu vacancies, which is the possible origin of p-type conductivity. The appearance of free exciton emission can demonstrate the direct bandgap transition behavior of CuGaO2 nanoplates. The as-prepared p-type CuGaO2 nanoplates were further decorated by n-type ZnO nanoparticles via calcination method to fabricate p-n junction nanocomposites. The nanocomposites exhibited enhanced photocatalytic activity which can be ascribed to the effective separation of photogenerated carriers by the internal electrostatic field in the p-n junction region, and the enhanced light absorption properties resulted from sub-bandgap absorption effect of p-n junction. This work has offered a new insight into the design of p-n junction devices using p-type CuGaO2 nanoplates.

  5. Solution-combustion synthesis and photoluminescence properties of YBO3:Tb3+ phosphor powders

    NASA Astrophysics Data System (ADS)

    Onani, Martin O.; Okil, Joseph O.; Dejene, Francis B.

    2014-04-01

    YBO3:Tb3+ nanocrystalline phosphors were successfully deposited by a solution-combustion method, using rare-earth nitrates, urea and boric acid as starting materials. The crystal structure, morphology, chemical composition and photoluminescence properties of the films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). The results of SEM and XRD revealed that the powders were composed of spherical YBO3:Tb3+ nanocrystals with average grain size of between 50 and 100 nm. The electron diffraction spectroscopy (EDS) confirmed the presence of the Y, B, O, and C. The XRD measurements revealed YBO3:Tb3+ (JCPDS:83-1205) structure when annealed at 1000 °C for 2 h. The YBO3:Tb3+ powders exhibited emissions at 490, 545 and 585 nm, which were assigned to the 5D4-7F6, 5D4-7F5 and 5D4-7F4 transitions of Tb3+, respectively. Among them, the green emission at 545 nm (5D4-7F5) was dominant.

  6. Synthesis, thermal and photoluminescent properties of ZnSe- based oxyfluoride glasses doped with samarium

    NASA Astrophysics Data System (ADS)

    Kostova, I.; Okada, G.; Pashova, T.; Tonchev, D.; Kasap, S.

    2014-12-01

    Rare earth (RE) doped glasses and glass ceramic materials have recently received considerable attention because of their potential or realized applications as X-ray intensifying screens, phosphors, detectors, waveguides, lasers etc. [1]. In this work, we present a new RE doped ZnO-ZnSe-SrF2-P2O5-B2O3-Sm2O3-SmF3 (ZSPB) glass system synthesized by melt quenching technique. The resulting glasses were visually fully transparent and stable with glass the transition temperatures around 530°C. The thermal properties of this glass system were characterized by Modulated Differential Scanning Calorimetry (MDSC) measurements before and after annealing at 650°C. We have characterized these glasses by Raman spectroscopy and photoluminescence (PL) measurements over the UV-VIS range using light emitting diodes (LED) and laser diodes (LD) excitation sources. We have also irradiated thermally treated and non-treated glass samples by X-rays and have studied the resulting PL. We discuss the results in terms of previously reported models for Sm-doped Zn-borophosphate oxide, oxyfluoride and oxyselenide glasses.

  7. Structural and photoluminescence properties of terbium-doped zinc oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Ningthoujam Surajkumar, Singh; Shougaijam Dorendrajit, Singh; Sanoujam Dhiren, Meetei

    2014-05-01

    We present in this paper a study of the structural and photoluminescence (PL) properties of terbium (Tb) doped zinc oxide (ZnO) nanoparticles synthesized by a simple low temperature chemical precipitation method, using zinc acetate and terbium nitrate in an isopropanol medium with diethanolamine (DEA) as the capping agent at 60 °C. The as-prepared samples were heat treated and the PL of the annealed samples were studied. The prepared nanoparticles were characterized with X-ray diffraction (XRD). The XRD patterns show the pattern of typical ZnO nanoparticles and correspond with the standard XRD pattern given by JCPDS card No. 36-1451, showing the hexagonal phase structure. The PL intensity was enhanced due to Tb3+ doping, and it decreased at higher concentrations of Tb3+ doping after reaching a certain optimum concentration. The PL spectra of Tb3+ doped samples exhibited blue, bluish green, and green emissions at 460 nm (5D3 - 7F3), 484 nm (5D4 - 7F6), and 530 nm (5D4 - 7F5), respectively, which were more intense than the emissions for the undoped ZnO sample. Based on the results, an energy level schematic diagram was proposed to explain the possible electron transition processes.

  8. Microsphere morphology tuning and photo-luminescence properties of monoclinic Y2WO6

    NASA Astrophysics Data System (ADS)

    Gao, Hong; Bai, Yulong; Zhang, Junying; Tang, Zilong

    2015-04-01

    Effects of the solution pH value and reaction time on the precursor morphology and photoluminescence properties are investigated for hydrothermally prepared monoclinic Y2WO6 phosphors. In the near-neutral environment, sodium dodecyl benzene sulfonate (SDBS) surfactant forms small microspheres micelles as template to synthesize microspherical precursor. H+ ions concentration affects the arrangement of negative ionic surfactant SDBS. As a result, jujube-liked and popcorn-like loose microspheres formed at low pH value. When the pH value is 5.2 and the hydrothermal reaction time reaches 24 h, respectively, the strongest luminescent intensity can be obtained. Under this condition, the precursor presented regular microsphere with diameter of 4.0 μm. After high-temperature heat treatment, the obtained phosphor particles still exhibit microsphere-like shape. Therefore, we provide an effective method to tune the morphology of Y2WO6 phosphors and study the relationship between morphology and luminescent performance.

  9. Photoluminescent and electroluminescent properties of Mn-doped ZnS nanocrystals

    NASA Astrophysics Data System (ADS)

    Yang, Heesun; Holloway, Paul H.; Ratna, Banahalli B.

    2003-01-01

    ZnS:Mn nanocrystals with sizes between 3 and 4 nm were synthesized via a competitive reaction chemistry method, where the surface capping organic species (p-thiocresol) is used as an inhibitor of the crystal growth. The x-ray diffraction and photoluminescent (PL) properties of ZnS:Mn bulk and nanocrystals were compared. A direct current electroluminescent (EL) device having a hybrid organic/inorganic multilayer structure, indium tin oxide/poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT-PSS)/PVK/ZnS:Mn NC/Al, was tested. In this multilayer EL device structure, the PEDOT-PSS leads to enhanced hole injection, while the poly(N-vinylcarbazole) (PVK) serves as a passivation layer between the PEDOT-PSS and nanocrystal layers. Electron-hole recombination was not confined to the ZnS:Mn nanocrystal layer, but also occurred in the PVK layer. The result was emission from both the blue-emitting PVK and yellow-emitting ZnS:Mn nanocrystals. The EL emission spectrum was dependent upon the voltage, showing an increasing ratio of PVK emission to nanocrystal emission with increased voltage. The dependence of PL and EL emissions on Mn concentration (0.40 to 2.14 mol %) is also reported.

  10. Enhancing photoluminescence properties of SiC/SiO2 coaxial nanocables by making oxygen vacancies.

    PubMed

    Liu, Wenna; Chen, Junhong; Yang, Tao; Chou, Kuo-Chih; Hou, Xinmei

    2016-09-14

    Coaxial nanocables (CNs) with an SiC core and a SiO2 shell were fabricated at a large scale by a simple and low cost method. The thickness of the SiO2 shell could be controlled by etching in 1 M NaOH aqueous solution for different amounts of time. XRD, SEM, TEM, HRTEM, PL and UV-Vis spectra were adopted to investigate the morphology and optical properties of the obtained SiC/SiO2CNs. Blue photoluminescence was observed at room temperature from the coaxial structure. The intensity of the single emission band at 468 nm (2.65 eV) exhibited a strong dependence on the thickness of the SiO2 layer and was significantly enhanced when the outer SiO2 shell had a thickness of 2.8 nm. The enhancement effect was attributed to oxygen vacancies (OV) and this was verified by deliberately enriching the surface OV through hydrogen treatment. PMID:27503431

  11. Effects of natural oxidation on the photoluminescence properties of Si nanocrystals prepared by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Xu, Yanmei; Han, Yinghui

    2014-07-01

    In this work, Si nanocrystals (Si-NCs) have been prepared by pulsed laser ablation technique in dichloromethane, and the microstructure and photoluminescence (PL) properties of the Si-NCs before and after natural oxidation were investigated. Transmission electron microscopy and Raman results show that the average diameter of the Si-NCs is 2.42 nm in the dichloromethane solution. Blue-violet PL with a lifetime of 4.6 ns is observed at room temperature, and the PL peak shifts toward longer wavelength with the red shift of excitation wavelength. The PL excitation spectrum indicates that the bandgap of the Si-NCs in solution is 2.64 eV, which confirms that the blue-violet PL originates from interband transition of Si-NCs caused by quantum confinement effect. The PL peak red shifts to 607 nm after natural oxidation, and the peak lifetime of which is slow down to 13.1 μs. The fixed PL peak excited by different wavelengths and the slow PL decay time indicate that interface defects become the main PL mechanism after natural oxidation. The results will add new information for understanding the PL mechanism of Si-NCs in different environments.

  12. Photoluminescence properties of Sr2MgB2O6:Eu3+ red phosphor under near-UV excitation

    NASA Astrophysics Data System (ADS)

    Guo, Rui; Tang, Songling; Zhong, Shaobin; Luo, Lan; Cheng, Baochang; Xiong, Yuhua

    2015-12-01

    Sr2MgB2O6:Eu3+ red phosphor has been synthesized by modified solid-state reaction method. The photoluminescence properties of Sr2MgB2O6:Eu3+ phosphor have been investigated. Sr2MgB2O6:Eu3+ phosphor can be effectively excited by 394 nm and generate red emission at 615 nm. Eu3+ ions occupy both Sr2+-site and Mg2+-site in Sr2MgB2O6. Univalent charge compensators (Li+, Na+ and K+) can obviously improve the photoluminescence properties of Sr2MgB2O6:Eu3+ phosphor and Na+ is the optimal charge compensator. The effect of substitution of M2+ (M = Mg, Ca or Ba) ion for Sr2+ on the photoluminescence properties of Sr2MgB2O6:Eu3+ phosphor has also been discussed. It implies that Sr2MgB2O6:Eu3+ may be a potential red phosphor for near-UV W-LEDs or other display devices.

  13. The influence of temperature on the photoluminescence properties of single InAs quantum dots grown on patterned GaAs

    PubMed Central

    2012-01-01

    We report the temperature-dependent photoluminescence of single site-controlled and self-assembled InAs quantum dots. We have used nanoimprint lithography for patterning GaAs(100) templates and molecular beam epitaxy for quantum dot deposition. We show that the influence of the temperature on the photoluminescence properties is similar for quantum dots on etched nanopatterns and randomly positioned quantum dots on planar surfaces. The photoluminescence properties indicate that the prepatterning does not degrade the radiative recombination rate for the site-controlled quantum dots. PMID:22713215

  14. Size and temperature dependence of the photoluminescence properties of NIR emitting ternary alloyed mercury cadmium telluride quantum dots

    NASA Astrophysics Data System (ADS)

    Jagtap, Amardeep M.; Chatterjee, Abhijit; Banerjee, Arup; Babu Pendyala, Naresh; Koteswara Rao, K. S. R.

    2016-04-01

    Exciton-phonon coupling and nonradiative relaxation processes have been investigated in near-infrared (NIR) emitting ternary alloyed mercury cadmium telluride (CdHgTe) quantum dots. Organically capped CdHgTe nanocrystals of sizes varying from 2.5-4.2 nm have been synthesized where emission is in the NIR region of 650-855 nm. Temperature-dependent (15-300 K) photoluminescence (PL) and the decay dynamics of PL at 300 K have been studied to understand the photophysical properties. The PL decay kinetics shows the transition from triexponential to biexponential on increasing the size of the quantom dots (QDs), informing the change in the distribution of the emitting states. The energy gap is found to be following the Varshni relation with a temperature coefficient of 2.1-2.8  ×  10-4 eV K-1. The strength of the electron-phonon coupling, which is reflected in the Huang and Rhys factor S, is found in the range of 1.17-1.68 for QDs with a size of 2.5-4.2 nm. The integrated PL intensity is nearly constant until 50 K, and slowly decreases up to 140 K, beyond which it decreases at a faster rate. The mechanism for PL quenching with temperature is attributed to the presence of nonradiative relaxation channels, where the excited carriers are thermally stimulated to the surface defect/trap states. At temperatures of different region (<140 K and 140-300 K), traps of low (13-25 meV) and high (65-140 meV) activation energies seem to be controlling the quenching of the PL emission. The broadening of emission linewidth is found to due to exciton-acoustic phonon scattering and exciton-longitudinal optical (LO) phonon coupling. The exciton-acoustic phonon scattering coefficient is found to be enhanced up to 55 μeV K-1 due to a stronger confinement effect. These findings give insight into understanding the photophysical properties of CdHgTe QDs and pave the way for their possible applications in the fields of NIR photodetectors and other optoelectronic devices.

  15. Half-oxidized phosphorene: band gap and elastic properties modulation

    NASA Astrophysics Data System (ADS)

    Drissi, L. B.; Sadki, S.; Sadki, K.

    2016-04-01

    Based on a first principles approach, we study structural, electronic and elastic properties, as well as stabilities of all possible half-oxidized phosphorene conformers. Stability analysis reveals that oxygen chemisorption is an exothermic process in the six configurations despite the formation of interstitial oxygen bridges in three of them. Electronic structure calculations show that oxidation induces a band gap modulation ranging between 0.54 and 1.57 eV in the generalized gradient approximation corrected to 1.19 and 2.88 eV using GW. The mechanical response of the conformers is sensitively dependent on direction and indicates that the new derivatives are incompressible materials and one configuration has an auxetic behavior. The present results provide a basis for tailoring the electronic and elastic properties of phosphorene via half oxidation.

  16. Half-oxidized phosphorene: band gap and elastic properties modulation.

    PubMed

    Drissi, L B; Sadki, S; Sadki, K

    2016-04-13

    Based on a first principles approach, we study structural, electronic and elastic properties, as well as stabilities of all possible half-oxidized phosphorene conformers. Stability analysis reveals that oxygen chemisorption is an exothermic process in the six configurations despite the formation of interstitial oxygen bridges in three of them. Electronic structure calculations show that oxidation induces a band gap modulation ranging between 0.54 and 1.57 eV in the generalized gradient approximation corrected to 1.19 and 2.88 eV using GW. The mechanical response of the conformers is sensitively dependent on direction and indicates that the new derivatives are incompressible materials and one configuration has an auxetic behavior. The present results provide a basis for tailoring the electronic and elastic properties of phosphorene via half oxidation. PMID:26964522

  17. Hanford Waste Physical and Rheological Properties: Data and Gaps

    SciTech Connect

    Kurath, Dean E.; Wells, Beric E.; Huckaby, James L.; Mahoney, Lenna A.; Daniel, Richard C.; Burns, Carolyn A.; Tingey, Joel M.; Cooley, Scott K.

    2012-03-01

    The retrieval, transport, treatment and disposal operations associated with Hanford Tank Wastes involve the handling of a wide range of slurries. Knowledge of the physical and rheological properties of the waste is a key component to the success of the design and implementation of the waste processing facilities. Previous efforts to compile and analyze the physical and rheological properties were updated with new results including information on solids composition and density, particle size distributions, slurry rheology, and particle settling behavior. The primary source of additional data is from a recent series of tests sponsored by the Hanford Waste Treatment and Immobilization Plant. These tests involved an extensive suite of characterization and bench-scale process testing of 8 waste groups representing approximately 75% of the high-level waste mass expected to be processed through the WTP. Additional information on the morphology of the waste solids was also included. Based on the updated results, a gap analysis to identify gaps in characterization data, analytical methods and data interpretation was completed.

  18. Hanford Waste Physical and Rheological Properties: Data and Gaps - 12078

    SciTech Connect

    Kurath, D.E.; Wells, B.E.; Huckaby, J.L.; Mahoney, L.A.; Daniel, R.C.; Burns, C.A.; Tingey, J.M.; Cooley, S.K.

    2012-07-01

    The retrieval, transport, treatment and disposal operations associated with Hanford Tank Wastes involve the handling of a wide range of slurries. Knowledge of the physical and rheological properties of the waste is a key component to the success of the design and implementation of the waste processing facilities. Previous efforts to compile and analyze the physical and rheological properties were updated with new results including information on solids composition and density, particle size distributions, slurry rheology, and particle settling behavior. The primary source of additional data is from a recent series of tests sponsored by the Hanford Waste Treatment and Immobilization Plant (WTP). These tests involved an extensive suite of characterization and bench-scale process testing of 8 waste groups representing approximately 75% of the high-level waste mass expected to be processed through the WTP. Additional information on the morphology of the waste solids was also included. Based on the updated results, a gap analysis to identify gaps in characterization data, analytical methods and data interpretation was completed. (authors)

  19. Studies on Ferromagnetic and Photoluminescence Properties of ITO and Cu-Doped ITO Nanoparticles Synthesized by Solid State Reaction

    NASA Astrophysics Data System (ADS)

    Babu, S. Harinath; Kaleemulla, S.; Rao, N. Madhusudhana; Krishnamoorthi, C.

    2016-07-01

    Cubic structured indium-tin-oxide (ITO) and copper-doped ITO nanoparticles were synthesized by solid state reaction. The structure, morphology, chemical, magnetic, and photoluminescence properties of the synthesized nanoparticles were studied by x-ray diffraction, field emission scanning electron microscopy, x-ray photoelectron spectroscopy, vibrating sample magnetometry, and photoluminescence spectrophotometry, respectively. Magnetic studies confirmed that the ITO nanoparticles were ferromagnetic at room temperature (300 K) and at 100 K, and it was believed that the observed ferromagnetism may be due to oxygen vacancies and defects present in the system. No hysteresis loop was observed in copper-doped ITO nanoparticles at room temperature and 100 K. The ITO and Cu-doped ITO nanoparticles exhibited two broad emission peaks in the visible region of the electromagnetic spectrum.

  20. Investigation on photoluminescence properties and defect chemistry of GdAlO3:Dy3+ Ba2+ phosphors

    NASA Astrophysics Data System (ADS)

    Selvalakshmi, Thangaraj; Sellaiyan, Selvakumar; Uedono, Akira; Semba, Takaaki; Bose, Arumugam Chandra

    2016-08-01

    GdAlO3:Dy3+ Ba2+ phosphors are synthesized by citrate-based sol-gel method. Photoluminescence and positron annihilation studies are used to investigate the emission and defect chemistry of the phosphors respectively. The strong yellow (Dy3+) emission properties of phosphors are discussed for various concentrations of Dy3+ ions. Upon the addition of Ba2+ ion, an enhancement in emission intensity is observed due to the lattice distortions around Dy3+ ion. The positron studies indicate the presence of defects at crystallite boundaries, vacancy clusters and large voids in the materials. The influence of Ba2+ ion on the photoluminescence and lattice distortion around Dy3+ is also explored.

  1. Synthesis and Photoluminescence Properties of Li2SrSiO4 Activated with Dy3+ and Sm3+

    NASA Astrophysics Data System (ADS)

    Erdoğmuş, E.

    2015-01-01

    Li2SrSiO4:M (M: Dy3+ and Sm3+) phosphors were synthesized by the conventional solid state reaction. The synthesized materials were characterized by powder XRD. The emission and excitation spectra of these phosphors were measured at room temperature with a spectrofluorometer. The first phosphor, Li2SrSiO4:Dy3+, emits at 479, 573, and 666 nm upon 351 nm excitation. The second phosphor, Li2SrSiO4:Sm3+, emits at 561-571, 594, 647-655, and 703-713 nm upon 399 nm excitation. Also, the dependence of the photoluminescence properties of both phosphors on boric acid concentration was investigated. The results showed that boric acid was effective in improving the photoluminescence intensity of both phosphors.

  2. Photoluminescence properties of nanocrystalline Tb 3+ doped Y 2O 3 phosphor prepared through a novel synthetic route

    NASA Astrophysics Data System (ADS)

    Ray, S.; Patra, A.; Pramanik, P.

    2007-12-01

    Green emitting cubic Y2O3:Tb3+ nanocrystalline phosphor having particle size of 22 nm was synthesized by TEA (triethanolamine) based precursor solution method. We have characterized our nanocrystalline sample by XRD, HRTEM and Raman spectroscopic measurement. We compared the photoluminescence properties of our nanocrystalline sample with the bulk one. Due to the presence of defect states and lower phonon density of nanomaterials, cross relaxation process seems to be less effective in nanosized sample reflecting higher blue/green ratio in nanosized sample. Relative intensity of 5D4-7F5 transition with respect to 5D4-7F6 transition is reduced in nanosized sample due to greater transition probability of the latter transition in the distorted nanostructured material. Our analysis suggests that change of local environments takes place with decreasing the particle size and it is reflected in the photoluminescence spectra.

  3. Synthesis and photoluminescence properties of Ho3+ doped LaAlO3 nanoparticles.

    PubMed

    Vu, Hong Ha Thi; Atabaev, Timur S; Kim, Hyung-Kook; Hwang, Yoon-Hwae

    2012-07-01

    Nanosized particles with different Ho3+ concentrations were synthesized in LaAlO3 lattices using a simple Pechini-type sol-gel method. X-ray diffraction measurements were used to investigate the structural composition and the effects of holmium dopant concentration on LaAlO3:Ho3+ crystal formation. Field-emission scanning-electron microscopy images confirm the formation of approximately spherical particles with an average size about 100 nm. The photoluminescence results yielded optimal holmium ion concentration in LaAlO3 host matrices was about 3% in mol equivalent. The mechanism that are responsible for the photoluminescence emission processes discussed with the help of Ho3+-ion Dieke energy level diagram. Power dependent slope measurements were performed to identify up-conversion photoluminescence process involved in LaAlO3:Ho3+. PMID:22966668

  4. Microwave-assisted hydrothermal synthesis of Ag2(W1 -xMox)O4 heterostructures: Nucleation of Ag, morphology, and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Silva, M. D. P.; Gonçalves, R. F.; Nogueira, I. C.; Longo, V. M.; Mondoni, L.; Moron, M. G.; Santana, Y. V.; Longo, E.

    2016-01-01

    Ag2W1 -xMoxO4 (x = 0.0 and 0.50) powders were synthesized by the co-precipitation (drop-by-drop) method and processed using a microwave-assisted hydrothermal method. We report the real-time in situ formation and growth of Ag filaments on the Ag2W1 -xMoxO4 crystals using an accelerated electron beam under high vacuum. Various techniques were used to evaluate the influence of the network-former substitution on the structural and optical properties, including photoluminescence (PL) emission, of these materials. X-ray diffraction results confirmed the phases obtained by the synthesis methods. Raman spectroscopy revealed significant changes in local order-disorder as a function of the network-former substitution. Field-emission scanning electron microscopy was used to determine the shape as well as dimensions of the Ag2W1 -xMoxO4 heterostructures. The PL spectra showed that the PL-emission intensities of Ag2W1 -xMoxO4 were greater than those of pure Ag2WO4, probably because of the increase of intermediary energy levels within the band gap of the Ag2W1 -xMoxO4 heterostructures, as evidenced by the decrease in the band-gap values measured by ultraviolet-visible spectroscopy.

  5. Microwave-assisted hydrothermal synthesis of Ag₂(W(1-x)Mox)O₄ heterostructures: Nucleation of Ag, morphology, and photoluminescence properties.

    PubMed

    Silva, M D P; Gonçalves, R F; Nogueira, I C; Longo, V M; Mondoni, L; Moron, M G; Santana, Y V; Longo, E

    2016-01-15

    Ag2W(1-x)MoxO4 (x=0.0 and 0.50) powders were synthesized by the co-precipitation (drop-by-drop) method and processed using a microwave-assisted hydrothermal method. We report the real-time in situ formation and growth of Ag filaments on the Ag2W(1-x)MoxO4 crystals using an accelerated electron beam under high vacuum. Various techniques were used to evaluate the influence of the network-former substitution on the structural and optical properties, including photoluminescence (PL) emission, of these materials. X-ray diffraction results confirmed the phases obtained by the synthesis methods. Raman spectroscopy revealed significant changes in local order-disorder as a function of the network-former substitution. Field-emission scanning electron microscopy was used to determine the shape as well as dimensions of the Ag2W(1-x)MoxO4 heterostructures. The PL spectra showed that the PL-emission intensities of Ag2W(1-x)MoxO4 were greater than those of pure Ag2WO4, probably because of the increase of intermediary energy levels within the band gap of the Ag2W(1-x)MoxO4 heterostructures, as evidenced by the decrease in the band-gap values measured by ultraviolet-visible spectroscopy. PMID:26361214

  6. Controlled fabrication and tunable photoluminescence properties of Mn{sup 2+} doped graphene–ZnO composite

    SciTech Connect

    Luan, Xinglong; Zhang, Yihe Tong, Wangshu; Shang, Jiwu; An, Qi; Huang, Hongwei

    2014-11-15

    Highlights: • Graphene–ZnO composites were synthesized by a mixed solvothermal method. • ZnO quantum dots are distributed uniformly on the graphene sheets. • A possible hypothesis is raised for the influence of graphene oxide on the nucleation of ZnO. • Mn{sup 2+} doped graphene–ZnO composites were fabricated and the emission spectra can be tuned by doping. - Abstract: Graphene–ZnO composites (G–ZnO) with controlled morphology and photoluminescence property were synthesized by a mixed solvothermal method. Mixed solvent were composed by dimethyl sulfoxide and ethylene glycol. Fourier transform infrared spectroscopy, transmission electron microscopy and photoluminescence spectra were used to characterize G–ZnO. Graphene as a substrate can help the distribution and the dispersity of ZnO, and a possible model of the interaction between graphene oxide and ZnO particles is proposed. At the same time, graphene also reduce the size of ZnO particles to about 5 nm. Furthermore, Mn{sup 2+} ions dopes G–ZnO successfully by the mixed solvothermal synthesis and the doping of Mn{sup 2+} makes G–ZnO shift red from 465 nm to 548 nm and 554 nm in the emission spectrum. The changes of the emission spectrum by the adding of Mn{sup 2+} make G–ZnO have tunable photoluminescence spectrum which is desirable for practical applications.

  7. Influence of substituent position on thermal properties, photoluminescence and morphology of pyrene-fluorene derivatives

    NASA Astrophysics Data System (ADS)

    Feng, Xing; Hu, Jian-Yong; Wei, Xian-Fu; Redshaw, Carl; Yamato, Takehiko

    2015-04-01

    New position-dependent conjugated hydrocarbon dyes containing a pyrene core and multi-fluorene moieties 3 have been synthesized and characterized by 1H/13C NMR spectroscopy, as well as by optical and theoretical studies. The solubility of mono-, bis- and tetra-fluorenyl-pyrene 3 tends to decrease and leads to varied thermal properties. The results of the optical studies and DFT calculations revealed that the energy gap can be easily modified or fine-tuned by either varying the substituent number or position. Remarkably, such pyrene-fluorene materials exhibited deep blue fluorescence (λmax = 400-458 nm in CH2Cl2) with excellent quantum yields (≈78%). These results suggest that these new pyrene-fluorene derivatives have potential application in OLED technology as blue host materials.

  8. Enhancement in ferroelectric, pyroelectric and photoluminescence properties in dye doped TGS crystals

    NASA Astrophysics Data System (ADS)

    Sinha, Nidhi; Goel, Neeti; Singh, B. K.; Gupta, M. K.; Kumar, Binay

    2012-06-01

    Pure and dye doped (0.1 and 0.2 mol%) Triglycine Sulfate (TGS) single crystals were grown by slow evaporation technique. A pyramidal coloring pattern, along with XRD and FT-IR studies confirmed the dye doping. Decrease in dielectric constant and increase in Curie temperature (Tc) were observed with increasing doping concentration. Low absorption cut off (231 nm) and high optical transparency (>90%) resulting in large band gap was observed in UV-VIS studies. In addition, strong hyper-luminescent emission bands at 350 and 375 nm were observed in which the relative intensity were found to be reversed as a result of doping. In P-E hysteresis loop studies, a higher curie temperature and an improved and more uniform figure of merit over a large region of the ferroelectric phase were observed. The improved dielectric, optical and ferroelectric/pyroelectric properties make the dye doped TGS crystals better candidate for various opto- and piezo-electronics applications.

  9. Influence of acetylcholinesterase immobilization on the photoluminescence properties of mesoporous silicon surface

    NASA Astrophysics Data System (ADS)

    Saleem, Muhammad; Rafiq, Muhammad; Seo, Sung-Yum; Lee, Ki Hwan

    2014-07-01

    Acetylcholinesterase immobilized p-type porous silicon surface was prepared by covalent attachment. The immobilization procedure was based on support surface chemical oxidation, silanization, surface activation with cyanuric chloride and finally covalent attachment of free enzyme on the cyanuric chloride activated porous silicon surface. Different pore diameter of porous silicon samples were prepared by electrochemical etching in HF based electrolyte solution and appropriate sample was selected suitable for enzyme immobilization with maximum trapping ability. The surface modification was studied through field emission scanning electron microscope, EDS, FT-IR analysis, and photoluminescence measurement by utilizing the fluctuation in the photoluminescence of virgin and enzyme immobilized porous silicon surface. Porous silicon showed strong photoluminescence with maximum emission at 643 nm and immobilization of acetylcholinesterase on porous silicon surface cause considerable increment on the photoluminescence of porous silicon material while acetylcholinesterase free counterpart did not exhibit any fluorescence in the range of 635-670 nm. The activities of the free and immobilized enzymes were evaluated by spectrophotometric method by using neostigmine methylsulfate as standard enzyme inhibitor. The immobilized enzyme exhibited considerable response toward neostigmine methylsulfate in a dose dependent manner comparable with that of its free counterpart alongside enhanced stability, easy separation from the reaction media and significant saving of enzyme. It was believed that immobilized enzyme can be exploited in organic and biomolecule synthesis possessing technical and economical prestige over free enzyme and prominence of easy separation from the reaction mixture.

  10. Structure and Photoluminescent Properties of ZnO Encapsulated in Mesoporous Silica SBA-15 Fabricated by Two-Solvent Strategy

    PubMed Central

    2009-01-01

    The two-solvent method was employed to prepare ZnO encapsulated in mesoporous silica (ZnO/SBA-15). The prepared ZnO/SBA-15 samples have been studied by X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, nitrogen adsorption–desorption isotherm, and photoluminescence spectroscopy. The ZnO/SBA-15 nanocomposite has the ordered hexagonal mesostructure of SBA-15. ZnO clusters of a high loading are distributed in the channels of SBA-15. Photoluminescence spectra show the UV emission band around 368 nm, the violet emission around 420 nm, and the blue emission around 457 nm. The UV emission is attributed to band-edge emission of ZnO. The violet emission results from the oxygen vacancies on the ZnO–SiO2interface traps. The blue emission is from the oxygen vacancies or interstitial zinc ions of ZnO. The UV emission and blue emission show a blue-shift phenomenon due to quantum-confinement-induced energy gap enhancement of ZnO clusters. The ZnO clusters encapsulated in SBA-15 can be used as light-emitting diodes and ultraviolet nanolasers. PMID:20596369

  11. MgO:Dy{sup 3+} nanophosphor: Self ignition route, characterization and its photoluminescence properties

    SciTech Connect

    Devaraja, P.B.; Avadhani, D.N.; Nagabhushana, H.; Prashantha, S.C.; Sharma, S.C.; Nagabhushana, B.M.; Nagaswarupa, H.P.; Daruka Prasad, B.

    2014-11-15

    For the first time series of MgO phosphors doped with different concentrations of Dy{sup 3+} (1–9 mol%) were prepared by solution combustion method using glycine as a fuel. The final products were well characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The powder X-ray diffraction patterns of the as-formed product show single cubic phase. The crystallite size estimated using Scherrer's method was found to be in the range 5–15 nm and the same was confirmed by transmission electron microscopy result. Photoluminescence properties of Dy{sup 3+} (1–9 mol%) doped MgO for near ultra violet excitation (325 nm) was studied in order to investigate the possibility of its use in white light emitting diode applications. The emission spectra consists of intra 4f transitions of Dy{sup 3+}, namely {sup 4}F{sub 9/2} → {sup 6}H{sub 15/2} (483 nm), and {sup 4}F{sub 9/2} → {sup 6}H{sub 13/2} (573 nm). Further, the emission at 573 nm shows strong yellow emission and can be applied to the yellow emission of phosphor for the application for near ultraviolet excitation. The intensity of yellow emission was attributed to intrinsic defects, especially oxygen-vacancies, which could assist the energy transfer from the MgO host to the Dy{sup 3+} ions. The Commission International De I-Eclairage chromaticity co-ordinates were calculated from emission spectra, the values (x,y) were very close to the National Television System Committee standard value of white emission. Therefore, the present phosphor was highly useful for display applications. - Graphical Abstract: PL emission spectra and CIE diagram of MgO:Dy{sup 3+} nanophosphor. - Highlights: • MgO:Dy{sup 3+} prepared by simple and low cost LCS method at low temperature (400 °C). • Characteristic emission peaks of Dy{sup 3+} ion at ∼ 483 and 573 nm are recorded. • CIE co-ordinate values located in the white region.

  12. Synthesis of nanostructured sol gel ITO films at different temperatures and study of their absorption and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Kundu, Susmita; Biswas, Prasanta K.

    2008-10-01

    Nanostructured indium tin oxide (ITO) films were deposited on silica glass by sol-gel dipping method from salt derived PVA based aqueous precursor. The films were cured at 250 °C, 350 °C, 450 °C, 600 °C, 700 °C and 900 °C and characterized by XRD, SEM, AFM techniques to observe heating effect on nanostructured feature. Nanocluster sizes were determined by TEM study. Different crystal phases of ITO were existed in the temperature range 250-900 °C. Quantum confinement behavior of the nanoclusters was observed for their size being near Bohr radius. Absorption, band gap and photoluminescence behavior of the nanstructured ITO films supported excitonic transitions due to the formation of electron hole pair generated by interaction of electromagnetic radiation.

  13. [Photoluminescence properties of nanocrystalline A3(VO4)2:Eu(A = Mg, Ca, Sr and Ba)].

    PubMed

    Fu, Xiao-yan; Niu, Shu-yun; Zhang, Hong-wu; Xin, Qin

    2006-01-01

    A series of europium doped alkali earth orthovanadates were prepared by Pechini-type sol-gel. The powders were characterized by transmission electron microscopy (TEM), infrared spectrum (IR) and photoluminescence (PL). The results of TEM show that high-quality nanopowders with controlled particle size about 50 nm were prepared. The relation between alkali earth ions and luminescence properties was observed from the results of luminescence spectra. Due to the similar ion radius of Ca2+ ions and Eu3+ ions, Ca3 (VO4 )2:Eu powders exhibit the strongest emission intensity among the four kind of phosphors. PMID:16827335

  14. Effect of Al3+ on Photoluminescence Properties of Eu3+-Doped BaZr(BO3)2 Phosphors

    NASA Astrophysics Data System (ADS)

    Li, Guang-Min; Li-Lan; Wang, Da-Jian; Zhang, Xiao-Song; Tao, Yi

    2006-08-01

    We discuss the influence of Al3+ 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 20 nm for the charge transfer state when doping with Al3+ and indicate the formation of `free' electrons due to the change of microstructures. In addition, the influence of Al3+ 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.

  15. Properties of dark subhaloes from gaps in tidal streams

    NASA Astrophysics Data System (ADS)

    Erkal, Denis; Belokurov, Vasily

    2015-12-01

    Cold or warm, the dark matter substructure spectrum must extend to objects with masses as low as 107 M⊙, according to the most recent Lyman α measurements. Around a Milky Way-like galaxy, more than a thousand of these subhaloes will not be able to form stars but are dense enough to survive even deep down in the potential well of their host. There, within the stellar halo, these dark pellets will bombard tidal streams as they travel around the Galaxy, causing small but recognizable damage to the stream density distribution. The detection and characterization of these stream ruptures will allow us to constrain the details of the subhalo-stream interaction. In this work, for the first time, we will demonstrate how the properties of a subhalo, most importantly its mass and size, can be reliably inferred from the gap it produces in a tidal stream. For a range of realistic observational setups, mimicking e.g. SDSS, DES, Gaia, and LSST data, we find that it is possible to measure the complete set of properties (including the phase-space coordinates during the flyby) of dark perturbers with M > 107 M⊙, up to a 1D degeneracy between the mass and velocity.

  16. Structural and photoluminescence properties of Ce, Dy, Er-doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Jayachandraiah, C.; Kumar, K. Siva; Krishnaiah, G.

    2015-06-01

    Undoped ZnO and rare earth elements (Ce, Dy and Er with 2 at. %) doped nanoparticles were synthesized by wet chemical co-precipitation method at 90°C with Polyvinylpyrrolidone (PVP) as capping agent. The structural, morphological, compositional and photoluminescence studies were performed with X-ray diffraction (XRD), Transmission electron microscopy (TEM), Energy dispersive spectroscopy (EDS), FTIR spectroscopy and Photoluminescence (PL) respectively. XRD results revealed hexagonal wurtzite structure with average particle size around 18 nm - 14 nm and are compatible with TEM results. EDS confirm the incorporation of Ce, Dy and Er elements into the host ZnO matrix and is validated by FTIR analysis. PL studies showed a broad intensive emission peak at 558 nm in all the samples. The intensity for Er- doped ZnO found maximum with additional Er shoulder peaks at 516nm and 538 nm. No Ce, Dy emission centers were found in spectra.

  17. [The photoluminescence and absorption properties of Co/AAO nano-array composites].

    PubMed

    Li, Shou-Yi; Wang, Cheng-Wei; Li, Yan; Wang, Jian; Ma, Bao-Hong

    2008-03-01

    Ordered Co/AAO nano-array structures were fabricated by alternating current (AC) electrodeposition method within the cylindrical pores of anodic aluminum oxide (AAO) template prepared in oxalic acid electrolyte. The photoluminescence (PL) emission and photoabsorption of AAO templates and Co/AAO nano-array structures were investigated respectively. The results show that a marked photoluminescence band of AAO membranes occurs in the wavelength range of 350-550 nm and their PL peak position is at 395 nm. And with the increase in the deposition amount of Co nanoparticles, the PL intensity of Co/AAO nano-array structures decreases gradually, and their peak positions of the PL are invariable (395 nm). Meanwhile the absorption edges of Co/AAO show a larger redshift, and the largest shift from the near ultraviolet to the infrared exceeds 380 nm. The above phenomena caused by Co nano-particles in Co/AAO composite were analyzed. PMID:18536402

  18. Iron hydroxyl phosphate microspheres: Microwave-solvothermal ionic liquid synthesis, morphology control, and photoluminescent properties

    SciTech Connect

    Cao Shaowen; Zhu Yingjie; Cui Jingbiao

    2010-07-15

    A variety of iron hydroxyl phosphate (NH{sub 4}Fe{sub 2}(PO{sub 4}){sub 2}OH.2H{sub 2}O) nanostructures such as solid microspheres, microspheres with the core in the hollow shell, and double-shelled hollow microspheres were synthesized by a simple one-step microwave-solvothermal ionic liquid method. The effects of the experimental parameters on the morphology and crystal phase of the resultant materials were investigated. Structural dependent photoluminescence was observed from the double-shelled hollow microspheres and the underlying mechanisms were discussed. - Graphical abstract: A variety of iron hydroxyl phosphate (NH{sub 4}Fe{sub 2}(PO{sub 4}){sub 2}OH.2H{sub 2}O) nanostructures were synthesized by a simple one-step microwave-solvothermal ionic liquid method. Structural dependent photoluminescence was observed from the double-shelled hollow microspheres.

  19. Structural and photoluminescence properties of Ce, Dy, Er-doped ZnO nanoparticles

    SciTech Connect

    Jayachandraiah, C.; Kumar, K. Siva; Krishnaiah, G.

    2015-06-24

    Undoped ZnO and rare earth elements (Ce, Dy and Er with 2 at. %) doped nanoparticles were synthesized by wet chemical co-precipitation method at 90°C with Polyvinylpyrrolidone (PVP) as capping agent. The structural, morphological, compositional and photoluminescence studies were performed with X-ray diffraction (XRD), Transmission electron microscopy (TEM), Energy dispersive spectroscopy (EDS), FTIR spectroscopy and Photoluminescence (PL) respectively. XRD results revealed hexagonal wurtzite structure with average particle size around 18 nm - 14 nm and are compatible with TEM results. EDS confirm the incorporation of Ce, Dy and Er elements into the host ZnO matrix and is validated by FTIR analysis. PL studies showed a broad intensive emission peak at 558 nm in all the samples. The intensity for Er- doped ZnO found maximum with additional Er shoulder peaks at 516nm and 538 nm. No Ce, Dy emission centers were found in spectra.

  20. Structural and photoluminescence properties of Cd and Cu co-doped zinc oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Samuel, T.; Sujatha, K.; Rao, K. Ramachandra; Rao, M. C.

    2016-05-01

    Cd and Cu co-doped ZnO nanoparticles were synthesized by Polyol method and subsequently have been characterized by their structure, optical and photoluminescence studies. XRD and PSA results revealed the formation of Cd and Cu co-doped ZnO nanoparticles with an average crystallite size of 50 nm and average particle size of 246 nm. From Zeta Potential measurements the Zeta Potential was found to be - 29.2 eV indicating the stability of prepared nanoparticles. From Uv-Vis studies, it is found that the absorption of undoped ZnO is less compared with Cd and Cu co-doped ZnO and the absorbance increases with increase in dopant concentration. Photoluminescence studies revealed that the samples are with high structural and optical quality.

  1. Preparation, characterization and photoluminescence properties of ultra long SiC/SiOx nanocables

    NASA Astrophysics Data System (ADS)

    Cai, K. F.; Zhang, A. X.; Yin, J. L.; Wang, H. F.; Yuan, X. H.

    2008-06-01

    SiC core and SiOx shell nanocables of a few millimeters long have been prepared by pyrolysis of SiO2 nanopowder added poly(dimethyl siloxane) without catalyst in a tube furnace at 1050 °C in Ar. The influence of the synthesis conditions (synthesis temperature and cooling time) on the products is studied. The products obtained from different conditions are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution electron microscopy equipped with energy dispersive X-ray spectroscopy, and photoluminescence spectroscopy. The results show that the cores and the shells are crystalline and amorphous, respectively, and that the addition of SiO2 nanopowder and prolongation of cooling time both increase the diameter of the cores. The growth process of the nanocables is discussed. The photoluminescence emission bands of the nanocables are mainly from their shells.

  2. The influence of pressure on the photoluminescence properties of a terbium-adipate framework

    SciTech Connect

    Spencer, Elinor C.; Zhao, Jing; Ross, Nancy L.; Andrews, Michael B.; Surbella, Robert G.; Cahill, Christopher L.

    2013-06-15

    The influence of pressure (over the 0–4.7 GPa range) on the photoluminescence emissions and crystal structure of the known 3D terbium-adipate metal-organic framework material Tb-GWMOF6 has been evaluated by high-pressure single-crystal X-ray diffraction and spectroscopic techniques. The results from this study show that this complex lanthanide framework structure undergoes three phase transitions within the 0–4 GPa pressure range that involve alterations in the number of symmetry independent Tb{sup 3+} ion sites within the crystal lattice. These pressure induced modifications to the structure of Tb-GWMOF6 lead to pronounced changes in the profiles of the {sup 5}D{sub 4}→{sup 7}F{sub 5} emission spectra of this complex. - Graphical abstract: The influence of pressure on the structure and photoluminescence emissions of a 3D terbium-adipate framework. - Highlights: • High-pressure luminescence spectra for a Tb framework were collected. • High-pressure single-crystal XRD experiments were conducted with the Tb Framework. • The framework undergoes two pressure-induced phase transitions. • The three phases of the material show different photoluminescence behaviour.

  3. Structural analysis, electronic and optical properties of the synthesized Sb2S3 nanowires with small band gap

    NASA Astrophysics Data System (ADS)

    Validžić, I. Lj; Mitrić, M.; Abazović, N. D.; Jokić, B. M.; Milošević, A. S.; Popović, Z. S.; Vukajlović, F. R.

    2014-03-01

    We report a simple colloidal synthesis of two types of Sb2S3 nanowires with small band gap and high aspect ratio. Field-emission scanning electron and transmission electron microscopies confirmed formation of high aspect ratio Sb2S3 nanowires, separated in the form of bundles and coalesced with each other in long bars. Diffuse reflectance and absorption spectroscopies revealed that the optical band-gap energies of the synthesized nanowires separated in the form of bundles are 1.56 and 1.59 eV, and coalesced with each other in long bars are 1.36 and 1.28 eV, respectively. The structure refinement showed that Sb2S3 powders belong to the orthorhombic structure with space group Pnma (no. 62). It was found that Sb2S3 nanowires separated in the form of bundles predominantly grow along the [0 1 0] direction being in the needle-like shape. The nanowires coalesced with each other in long bars rise in the form of long bars, are ribbon-like in shape and have expressed {1 0 1} facets which grow along the [0 1 0] direction. No peaks in photoluminescence spectra were observed in the spectral range from 250 to 600 nm. In order to shed more light on the experimental results concerning the band-gap energies and, in the literature generally poorly investigated electronic properties of the synthesized material, we performed theoretical calculations of the electronic structure and optical properties of the Sb2S3 samples synthesized here. This was done on the basis of density functional theory with the generalized gradient approximation, and also with an improved version of the exchange potential suggested recently by Tran and Blaha. The main characteristic is the significant improvement of the band gap value.

  4. Raman and photoluminescence properties of type II GaSb/GaAs quantum dots on (001) Ge substrate

    NASA Astrophysics Data System (ADS)

    Zon; Poempool, Thanavorn; Kiravittaya, Suwit; Nuntawong, Noppadon; Sopitpan, Suwat; Thainoi, Supachok; Kanjanachuchai, Songphol; Ratanathammaphan, Somchai; Panyakeow, Somsak

    2016-07-01

    We investigate structural Raman and photoluminescence properties of type II GaSb/GaAs quantum dots (QDs) grown on (001) Ge substrate by molecular beam epitaxy. Array of self-assembled GaSb QDs having an areal density of ˜1.66 × 1010 dots/cm2 is obtained by a growth at relatively low substrate temperature (450 °C) on a GaAs surface segmented into anti-phase domains (APDs). Most of QDs form in one APD area. However, a few QDs can be observed at the APD boundaries. Raman spectroscopy is used to probe the strain in GaAs layer. Slight redshift of both LO and TO GaAs peaks are observed when GaSb QDs are buried into GaAs matrix. Optical properties of capped QDs are characterized by photoluminescence measurement at low temperatures (20 K and 30 K). Emission peaks of GaSb/GaAs QDs are found in the range of 1.0-1.3 eV at both temperatures. Slight redshift is observed when the laser excitation power is increased at 20 K while blueshift of QD peak is observed at 30 K. We attribute this abnormal behavior to the contribution of overlapped GaSb wetting layer peak in the PL emission as well as the feature of type II band structure. [Figure not available: see fulltext.

  5. Enhanced photoluminescence properties of methylene blue dye encapsulated in nanosized hydroxyapatite/silica particles with core-shell structure

    NASA Astrophysics Data System (ADS)

    Ge, Xiaolu; Li, Chengfeng; Fan, Chengyu; Feng, Xiaoxing; Cao, Bingqiang

    2013-11-01

    Organic dye of methylene blue (MB) was encapsulated in core-shell structured hydroxyapatite/silica particles (HAp/silica-MB) through a modified Stöber method with the addition of polyvinylpyrrolidone molecules. It was found that MB molecules were released from HAp/silica-MB at a slower rate than those from silica-MB in deionized water. In phosphate buffered saline (pH: 7.2-7.4) and acidic solutions (pH: 1.5-1.6), the penetration of ions in the interface influenced the interaction between HAp and MB molecules, which resulted in the rapid release of MB molecules from HAp/silica-MB. From the UV-Vis absorbance spectra, one could see that MB molecules in HAp/silica-MB were weakly aggregated in comparison with those in silica-MB. For HAp/silica-MB, enhanced luminescence properties were observed in the photoluminescence spectra and dual luminescence with two emission peaks were caused by the presence of monomers and dimers. Contrarily, no photoluminescence emission was detected for samples of free MB and silica-MB under the same excitation condition because of the self-quenching effect. It was the adsorption of MB molecules on HAp that had resulted in the enlargement of intramolecular distance and the reduction of self-quenching effect. These hybrid particles with enhanced luminescent properties might find wide applications in the field of bioanalysis, bioseparation, and biomedical imaging.

  6. Structural and photoluminescence properties of doped and core-shell LaPO4:Eu3+ nanocrystals

    NASA Astrophysics Data System (ADS)

    Ghosh, Pushpal; Kar, Arik; Patra, Amitava

    2010-12-01

    Here, we have fabricated of LaPO4:Eu3+ doped and LaPO4/Eu2O3 core-shell nanocrystals using solution based methods. The morphologies, structure, formation mechanism, and photoluminescence properties of these nanocrystals are investigated in detail. The compressive and tensile lattice strains are obtained for hexagonal and monoclinic LaPO4 nanocrystals, respectively. Photoluminescence properties are found to be sensitive to the crystal phase, morphology, and core-shell structures. Judd-Ofelt parameters (Ω2) are calculated to understand the asymmetric nature of the dopant Eu3+ ion in LaPO4 nanocrystals host of various morphologies and crystal phases. It is seen that Ω2 value for nanorod (4.4×10-20 cm2) is higher than the nanoparticles (3.38×10-20 cm2). The quantum yield values increases from 28.27% to 52.4% by changing the crystal phase from hexagonal to monoclinic. The quantum yield of nanorods (58.50%) is higher than nanoparticles (28.68%).

  7. Optoelectronic properties analysis of Ti-substituted GaP.

    PubMed

    Tablero, C

    2005-11-01

    A study using first principles of the electronic and optical properties of materials derived from a GaP host semiconductor where one Ti atom is substituted for one of the eight P atoms is presented. This material has a metallic intermediate band sandwiched between the valence and conduction bands of the host semiconductor for 0 < or = U < or = 8 eV where U is the Hubbard parameter. The potential of these materials is that when they are used as an absorber of photons in solar cells, the efficiency is increased significantly with respect to that of the host semiconductor. The results show that the main contribution to the intermediate band is the Ti atom and that this material can absorb photons of lower energy than that of the host semiconductor. The efficiency is increased with respect to that of the host semiconductor mainly because of the absorption from the intermediate to conduction band. As U increases, the contribution of the Ti-d orbitals to the intermediate band varies, increasing the d(z2) character at the bottom of the intermediate band. PMID:16292917

  8. Synthesis, structure and photoluminescence properties of Sm3+-doped BiOBr phosphor

    NASA Astrophysics Data System (ADS)

    Halappa, Pramod; Shivakumara, C.; Saraf, Rohit; Nagabhushana, H.

    2016-05-01

    Well-crystallized tetragonal layered BiOBr and Bi0.95Sm0.05OBr phosphors were prepared by the solid state method. These compounds were characterized using powder X-Ray diffraction and photoluminescence technique. In PL spectra, the electric dipole transitions dominate than other transitions which indicate that the Sm3+ ions occupy a site with an inversion center of BiOBr. CIE chromaticity diagram confirmed that these phosphors can be useful in the fabrication of red component in white light emitting diodes (WLEDs) for display device applications.

  9. Nonlinear photoluminescence properties of trions in hole-doped single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Akizuki, Naoto; Iwamura, Munechiyo; Mouri, Shinichiro; Miyauchi, Yuhei; Kawasaki, Tomohiro; Watanabe, Hiroshi; Suemoto, Tohru; Watanabe, Kouta; Asano, Kenichi; Matsuda, Kazunari

    2014-05-01

    We studied the excitation density dependence of photoluminescence (PL) spectra of excitons and trions (charged excitons) in hole-doped single-walled carbon nanotubes. We found that the PL intensity of trions exhibited a strong nonlinear saturation behavior as the excitation density increased, whereas that of excitons exhibited a weak sublinear behavior. The strong PL saturation of trions is attributed to depletion of doped holes that are captured by excitons in the formation processes. Moreover, the effective radiative lifetime of a trion was evaluated to be approximately 20 ns.

  10. Ferroelectric (Na1/2Bi1/2)TiO3 thin films showing photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Zannen, M.; Dietze, M.; Khemakhem, H.; Es-Souni, M.

    2014-06-01

    Polycrystalline lead-free (Na1/2Bi1/2)TiO3 (NBT) ferroelectric thin films doped with 1 mol% of rare earth (RE) elements are processed on Pt-terminated silicon substrates using a solution deposition method. The thin films that exhibit single-phase perovskite structure show photoluminescence properties with highest intensities in the wavelength range between 700 and 850 nm, depending on RE element. The ferroelectric properties of the pure NBT film (P r: 20.5 µC cm-2, E c: 150 kV cm-1) are somewhat decreased for the doped films, which is ascribed to decreasing of the number of Bi lone pairs through the substitution of Bi with RE elements in the perovskite lattice.

  11. Effect of Silica Nanoparticles on the Photoluminescence Properties of BCNO Phosphor

    NASA Astrophysics Data System (ADS)

    Nuryadin, Bebeh W.; Faryuni, Irfana Diah; Iskandar, Ferry; Abdullah, Mikrajuddin; Khairurrijal, Khairurrijal

    2011-12-01

    Effect of additional silica nanoparticles on the photoluminescence (PL) performance of boron carbon oxy-nitride (BCNO) phosphor was investigated. As a precursor, boric acid and urea were used as boron and nitrogen sources, respectively. The carbon sources was polyethylene glycol (PEG) with average molecule weight 20000 g/mol.. Precursor solutions were prepared by mixing these raw materials in pure water, followed by stirring to achieve homogeneous solutions. In this precursor, silica nanoparticles were added at various mass ratio from 0 to 7 %wt in the solution. The precursors were then heated at 750 °C for 60 min in a ceramic crucible under atmospheric pressure. The photoluminescence (PL) spectrum that characterized by spectrophotometer showed a single, distinct, and broad emission band varied from blue to near red color, depend on the PEG, boric acid and urea ratio in the precursor. The addition of silica nanoparticles caused the increasing of PL intensity as well as the shifting of peak wavelength of PL spectrum. The peak shifting of PL was affected by the concentration of silica nanoparticles that added into the precursor. We believe that the BCNO-silica composite phosphor becomes a promising material for the phosphor conversion-based white light-emitting diodes.

  12. Shape controlled synthesis of CaMoO{sub 4} thin films and their photoluminescence property

    SciTech Connect

    Marques, Ana Paula de Azevedo Longo, Valeria M.; Melo, Dulce M.A. de; Pizani, Paulo S.; Leite, Edson R.; Varela, Jose Arana; Longo, Elson

    2008-05-15

    CaMoO{sub 4} (CMO) disordered and ordered thin films were prepared by the complex polymerization method (CPM). The films were annealed at different temperatures and time in a conventional resistive furnace (RF) and in a microwave (MW) oven. The microstructure and surface morphology of the structure were monitored by atomic force microscopy (AFM) and high-resolution scanning electron microscopy (HRSEM). Order and disorder were characterized by X-ray diffraction (XRD) and optical reflectance. A strong photoluminescence (PL) emission was observed in the disordered thin films and was attributed to complex cluster vacancies. The experimental results were compared with density functional and Hartree-Fock calculations. - Graphical abstract: CaMoO{sub 4} thin films were prepared by the complex polymerization method (CPM). The films were annealed at different temperatures and time in a conventional resistive furnace and in a microwave oven. A strong photoluminescence emission was observed in the disordered thin films and was attributed to complex cluster vacancies. The experimental results were confirmed by high level first principle calculations.

  13. Photoluminescence and electrical properties of polyvinyl alcohol films doped with CdS nanoparticles

    NASA Astrophysics Data System (ADS)

    Ali, Z. I.; Hosni, H. M.; Saleh, H. H.; Ghazy, O. A.

    2016-05-01

    In situ preparation of polyvinyl alcohol (PVA) films doped with cadmium sulfide (CdS) nanoparticles was conducted by gamma radiation. The films were characterized in terms of photoluminescence and electrical conductivity. The photoluminescence results indicated the existence of two emission peaks around 470 and 530 nm, which are due to electron-hole recombination of CdS nanoparticles and surface trapped emission due to the PVA capping, respectively. DC electrical conductivity ( σ DC) measurement in the temperature range from 303 up to 373 K reveals an increase in its value with increasing both Cd2+ ion molar concentration and irradiation dose. AC electrical conductivity ( σ AC) measurement over the same temperature range at an applied field frequency of 10, 100, 500 and 1000 kHz shows an increase behavior with increasing temperature, frequency, Cd2+ ion molar concentration and irradiation dose. Dielectric constant ( ɛ 1) exhibits an increase with temperature, whereas it shows reduced values with increasing frequency, Cd2+ ion molar concentration and irradiation dose. Also, the dielectric loss tangent (tan δ) follows an increasing trend with increasing temperature, Cd2+ ion molar concentration and irradiation dose while it has an opposite trend with increasing frequency. The CdS/PVA nanocomposite films behavior could be explained on the basis of formation of charge-transfer complexes (CTCs) by the CdS nanoparticles doped into the PVA matrix and the role of radiation in enhancing the charge carrier mobility of such CTCs.

  14. Enhancement in ferroelectric, pyroelectric and photoluminescence properties in dye doped TGS crystals

    SciTech Connect

    Sinha, Nidhi; Goel, Neeti; Singh, B.K.; Gupta, M.K.; Kumar, Binay

    2012-06-15

    Pure and dye doped (0.1 and 0.2 mol%) Triglycine Sulfate (TGS) single crystals were grown by slow evaporation technique. A pyramidal coloring pattern, along with XRD and FT-IR studies confirmed the dye doping. Decrease in dielectric constant and increase in Curie temperature (T{sub c}) were observed with increasing doping concentration. Low absorption cut off (231 nm) and high optical transparency (>90%) resulting in large band gap was observed in UV-VIS studies. In addition, strong hyper-luminescent emission bands at 350 and 375 nm were observed in which the relative intensity were found to be reversed as a result of doping. In P-E hysteresis loop studies, a higher curie temperature and an improved and more uniform figure of merit over a large region of the ferroelectric phase were observed. The improved dielectric, optical and ferroelectric/pyroelectric properties make the dye doped TGS crystals better candidate for various opto- and piezo-electronics applications. - Graphical abstract: Dye doping in TGS crystal resulted in hourglass morphology, increased hyper-luminescence intensity, improved T{sub c} and figure of merit. Highlights: Black-Right-Pointing-Pointer Amaranth dye doping in TGS crystals resulted in hourglass morphology. Black-Right-Pointing-Pointer Doping resulted in enhancement of Curie temperature from 49 to 53 Degree-Sign C. Black-Right-Pointing-Pointer Low cut off (230 nm) and wider transmittance window observed. Black-Right-Pointing-Pointer Strong hyper-luminescent emission bands at 350 and 375 nm were observed. Black-Right-Pointing-Pointer High and uniform figure of merit in ferroelectric phase was obtained.

  15. Influence of sputtering power on structural, mechanical and photoluminescence properties of nanocrystalline SiC thin films

    NASA Astrophysics Data System (ADS)

    Singh, Narendra; Kaur, Davinder

    2016-05-01

    In the present study, SiC thin films were deposited on Si (100) substrate by magnetron sputtering using a 4N purity commercial SiC target in argon atmosphere. The effect of sputtering RF power (140-170W) on structural, mechanical and photoluminescence properties were systematically studied by X-ray diffraction, field emission scanning electron microscopy, Nanoindentation and Spectrophotometer respectively. X-ray diffraction shows polycrystalline 4H-SiC phase with (105) preferred orientation and an enhancement in crystallite size with increasing power was also observed. The decrement in hardness and Young's modulus with increment in RF power was ascribed to Hall-Petch relation. The maximum hardness and Young's modulus were found to be 32 GPa and 232 GPa respectively. The photoluminescence spectra show peaks at 384 nm (3.22 eV) which corresponds to bandgap of 4H-SiC (phonon assisted band to band recombination) and 416 nm (2.99 eV) may be attributed to defect states and intensity of both peaks decreases as power increases.

  16. Effect of heat treatment on the structure of incorporated oxalate species and photoluminescent properties of porous alumina films formed in oxalic acid

    NASA Astrophysics Data System (ADS)

    Vrublevsky, I.; Jagminas, A.; Hemeltjen, S.; Goedel, W. A.

    2008-09-01

    The present work focuses on the use of IR spectroscopy and photoluminescence spectral measurements for studying the treatment temperature effect on the compositional and luminescent properties of oxalic acid alumina films. In line with the recent researches we have also found that heat treatment of porous alumina films formed in oxalic acid leads to considerable changes in their photoluminescence properties: upon annealing the intensity of photoluminescence (PL) increases reaching a maximum at the temperature of around 500 °C and then decreases. IR spectra of as-grown and heat-treated films have proved that PL emission in the anodic alumina films is related with the state of 'structural' oxalate species incorporated in the oxide lattice. These results allowed us to conclude that PL behavior of oxalic acid alumina films can be explained through the concept of variations in the bonding molecular orbitals of incorporated oxalate species including σ- and π-bonds.

  17. Electrospinning preparation and photoluminescence properties of poly (methyl methacrylate)/Eu{sup 3+} ions composite nanofibers and nanoribbons

    SciTech Connect

    Li, Maoying; Zhang, Zhenyi; Cao, Tieping; Sun, Yangyang; Liang, Pingping; Shao, Changlu; Liu, Yichun

    2012-02-15

    Graphical abstract: Nanofibers and nanoribbons of poly (methyl methacrylate)/Eu{sup 3+} ions composites were successfully prepared by using a simple electrospinning technique. And the photoluminescence properties of the above PMMA/Eu{sup 3+} ions composites were studied. Highlights: Black-Right-Pointing-Pointer Nanofibers and nanoribbons of PMMA/Eu{sup 3+} ions composites are fabricated by electrospinning. Black-Right-Pointing-Pointer Photoluminescence properties of as-electrospun PMMA/Eu{sup 3+} ions composites are studied. Black-Right-Pointing-Pointer The ratios of electric- and magnetic-dipole transitions are enhanced by increasing electrospinning voltage. -- Abstract: Nanofibers and nanoribbons of poly (methyl methacrylate) (PMMA)/Eu{sup 3+} ions composites with different concentration of Eu{sup 3+} ions were successfully prepared by using a simple electrospinning technique. From the results of scanning electron microscopy and energy-dispersive X-ray spectroscopy, we found that the morphology of the as-electrospun PMMA/Eu{sup 3+} ions composites could be changed from fiber to ribbon structure by adjusting the concentration of Eu{sup 3+} ions in the electrospun precursor solution. The coordination between the Eu{sup 3+} ions and PMMA molecules were investigated by Fourier transform infrared spectroscopy and differential thermal analysis. The photoluminescence (PL) properties of the as-electrospun PMMA/Eu{sup 3+} ions composites were studied in comparison to those of the Eu(NO{sub 3}){sub 3} powder. It was showed that the {sup 5}D{sub 0}-{sup 7}F{sub J} (J = 0, 1, 2, 3, 4) emission appeared in the PL spectra of the as-electrospun PMMA/Eu{sup 3+} ions composites, whereas the {sup 5}D{sub 0}-{sup 7}F{sub 0} emission was completely absent in the PL spectra of Eu(NO{sub 3}){sub 3} powder due to the different local environments surrounding Eu{sup 3+} ions. It was interesting to note that the intensity ratios of the electric-dipole and magnetic-dipole transitions for

  18. NaGd(MoO4)2 nanocrystals with diverse morphologies: controlled synthesis, growth mechanism, photoluminescence and thermometric properties

    PubMed Central

    Li, Anming; Xu, Dekang; Lin, Hao; Yang, Shenghong; Shao, Yuanzhi; Zhang, Yueli

    2016-01-01

    Pure tetragonal phase, uniform and well-crystallized sodium gadolinium molybdate (NaGd(MoO4)2) nanocrystals with diverse morphologies, e.g. nanocylinders, nanocubes and square nanoplates have been selectively synthesized via oleic acid-mediated hydrothermal method. The phase, structure, morphology and composition of the as-synthesized products are studied. Contents of both sodium molybdate and oleic acid of the precursor solutions are found to affect the morphologies of the products significantly, and oleic acid plays a key role in the morphology-controlled synthesis of NaGd(MoO4)2 nanocrystals with diverse morphologies. Growth mechanism of NaGd(MoO4)2 nanocrystals is proposed based on time-dependent morphology evolution and X-ray diffraction analysis. Morphology-dependent down-shifting photoluminescence properties of NaGd(MoO4)2: Eu3+ nanocrystals, and upconversion photoluminescence properties of NaGd(MoO4)2: Yb3+/Er3+ and Yb3+/Tm3+ nanoplates are investigated in detail. Charge transfer band in the down-shifting excitation spectra shows a slight blue-shift, and the luminescence intensities and lifetimes of Eu3+ are decreased gradually with the morphology of the nanocrystals varying from nanocubes to thin square nanoplates. Upconversion energy transfer mechanisms of NaGd(MoO4)2: Yb3+/Er3+, Yb3+/Tm3+ nanoplates are proposed based on the energy level scheme and power dependence of upconversion emissions. Thermometric properties of NaGd(MoO4)2: Yb3+/Er3+ nanoplates are investigated, and the maximum sensitivity is determined to be 0.01333 K−1 at 285 K. PMID:27506629

  19. NaGd(MoO4)2 nanocrystals with diverse morphologies: controlled synthesis, growth mechanism, photoluminescence and thermometric properties

    NASA Astrophysics Data System (ADS)

    Li, Anming; Xu, Dekang; Lin, Hao; Yang, Shenghong; Shao, Yuanzhi; Zhang, Yueli

    2016-08-01

    Pure tetragonal phase, uniform and well-crystallized sodium gadolinium molybdate (NaGd(MoO4)2) nanocrystals with diverse morphologies, e.g. nanocylinders, nanocubes and square nanoplates have been selectively synthesized via oleic acid-mediated hydrothermal method. The phase, structure, morphology and composition of the as-synthesized products are studied. Contents of both sodium molybdate and oleic acid of the precursor solutions are found to affect the morphologies of the products significantly, and oleic acid plays a key role in the morphology-controlled synthesis of NaGd(MoO4)2 nanocrystals with diverse morphologies. Growth mechanism of NaGd(MoO4)2 nanocrystals is proposed based on time-dependent morphology evolution and X-ray diffraction analysis. Morphology-dependent down-shifting photoluminescence properties of NaGd(MoO4)2: Eu3+ nanocrystals, and upconversion photoluminescence properties of NaGd(MoO4)2: Yb3+/Er3+ and Yb3+/Tm3+ nanoplates are investigated in detail. Charge transfer band in the down-shifting excitation spectra shows a slight blue-shift, and the luminescence intensities and lifetimes of Eu3+ are decreased gradually with the morphology of the nanocrystals varying from nanocubes to thin square nanoplates. Upconversion energy transfer mechanisms of NaGd(MoO4)2: Yb3+/Er3+, Yb3+/Tm3+ nanoplates are proposed based on the energy level scheme and power dependence of upconversion emissions. Thermometric properties of NaGd(MoO4)2: Yb3+/Er3+ nanoplates are investigated, and the maximum sensitivity is determined to be 0.01333 K‑1 at 285 K.

  20. Effects of Forest Gaps on Soil Properties in Castanopsis kawakamii Nature Forest.

    PubMed

    He, Zhongsheng; Liu, Jinfu; Su, Songjin; Zheng, Shiqun; Xu, Daowei; Wu, Zeyan; Hong, Wei; Wang, James Li-Ming

    2015-01-01

    The aim of this study is to analyze the effects of forest gaps on the variations of soil properties in Castanopsis kawakamii natural forest. Soil physical and chemical properties in various sizes and development stages were studied in C. kawakamii natural forest gaps. The results showed that forest gaps in various sizes and development stages could improve soil pore space structure and water characteristics, which may effectively promote the water absorbing capacity for plant root growth and play an important role in forest regeneration. Soil pore space structure and water characteristics in small gaps showed more obvious improvements, followed by the medium and large gaps. Soil pore space structure and water characteristics in the later development stage of forest gaps demonstrated more obvious improvements, followed by the early and medium development stages. The contents of hydrolysable N and available K in various sizes and development stages of forest gaps were higher than those of non-gaps, whereas the contents of total N, total P, available P, organic matter, and organic carbon were lower. The contents of total N, hydrolysable N, available K, organic matter, and organic carbon in medium gaps were higher than those of large and small gaps. The disturbance of forest gaps could improve the soils' physical and chemical properties and increase the population species' richness, which would provide an ecological basis for the species coexistence in C. kawakamii natural forest. PMID:26496710

  1. Effects of Forest Gaps on Soil Properties in Castanopsis kawakamii Nature Forest

    PubMed Central

    He, Zhongsheng; Liu, Jinfu; Su, Songjin; Zheng, Shiqun; Xu, Daowei; Wu, Zeyan; Hong, Wei; Wang, James Li-Ming

    2015-01-01

    The aim of this study is to analyze the effects of forest gaps on the variations of soil properties in Castanopsis kawakamii natural forest. Soil physical and chemical properties in various sizes and development stages were studied in C. kawakamii natural forest gaps. The results showed that forest gaps in various sizes and development stages could improve soil pore space structure and water characteristics, which may effectively promote the water absorbing capacity for plant root growth and play an important role in forest regeneration. Soil pore space structure and water characteristics in small gaps showed more obvious improvements, followed by the medium and large gaps. Soil pore space structure and water characteristics in the later development stage of forest gaps demonstrated more obvious improvements, followed by the early and medium development stages. The contents of hydrolysable N and available K in various sizes and development stages of forest gaps were higher than those of non-gaps, whereas the contents of total N, total P, available P, organic matter, and organic carbon were lower. The contents of total N, hydrolysable N, available K, organic matter, and organic carbon in medium gaps were higher than those of large and small gaps. The disturbance of forest gaps could improve the soils’ physical and chemical properties and increase the population species’ richness, which would provide an ecological basis for the species coexistence in C. kawakamii natural forest. PMID:26496710

  2. Synthesis and Photoluminescence Property of Silicon Carbide Nanowires Via Carbothermic Reduction of Silica.

    PubMed

    Luo, Xiaogang; Ma, Wenhui; Zhou, Yang; Liu, Dachun; Yang, Bin; Dai, Yongnian

    2009-01-01

    Silicon carbide nanowires have been synthesized at 1400 degrees C by carbothermic reduction of silica with bamboo carbon under normal atmosphere pressure without metallic catalyst. X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy and Fourier transformed infrared spectroscopy were used to characterize the silicon carbide nanowires. The results show that the silicon carbide nanowires have a core-shell structure and grow along <111> direction. The diameter of silicon carbide nanowires is about 50-200 nm and the length from tens to hundreds of micrometers. The vapor-solid mechanism is proposed to elucidate the growth process. The photoluminescence of the synthesized silicon carbide nanowires shows significant blueshifts, which is resulted from the existence of oxygen defects in amorphous layer and the special rough core-shell interface. PMID:20651911

  3. Solvothermal synthesis, photoluminescence and photocatalytic properties of pencil-like ZnO microrods

    NASA Astrophysics Data System (ADS)

    Liu, Zhifu; Zhang, Qinghong; Li, Yaogang; Wang, Hongzhi

    2012-05-01

    Pencil-like ZnO microrods was synthesized via a simple solvothermal process in an aqueous solution of ethylenediamine and ethanolamine. The as-prepared ZnO was characterized by X-ray powder diffraction, field-emission scanning electron microscopy, room temperature photoluminescence spectra and UV-vis absorption spectra. The results indicated that ZnO microrods had the length in the range of 1.3-25 μm. The photocatalytic activity was studied by degradation of methylene blue (MB) aqueous solution, which showed that the as-prepared ZnO microrods possessed a high photocatalytic activity. The formation mechanism of the pencil-like ZnO was also investigated based on the experimental results.

  4. Synthesis and Photoluminescence Property of Silicon Carbide Nanowires Via Carbothermic Reduction of Silica

    NASA Astrophysics Data System (ADS)

    Luo, Xiaogang; Ma, Wenhui; Zhou, Yang; Liu, Dachun; Yang, Bin; Dai, Yongnian

    2010-01-01

    Silicon carbide nanowires have been synthesized at 1400 °C by carbothermic reduction of silica with bamboo carbon under normal atmosphere pressure without metallic catalyst. X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy and Fourier transformed infrared spectroscopy were used to characterize the silicon carbide nanowires. The results show that the silicon carbide nanowires have a core-shell structure and grow along <111> direction. The diameter of silicon carbide nanowires is about 50-200 nm and the length from tens to hundreds of micrometers. The vapor-solid mechanism is proposed to elucidate the growth process. The photoluminescence of the synthesized silicon carbide nanowires shows significant blueshifts, which is resulted from the existence of oxygen defects in amorphous layer and the special rough core-shell interface.

  5. The synthesis of size-controlled 3C-SiC nanoflakes and their photoluminescent properties.

    PubMed

    Fan, Xiujun; Ye, Ruquan; Peng, Zhiwei; Wang, Juanjuan; Fan, Ailing; Guo, Xia

    2016-06-24

    Size-controlled and high-purity 3C-SiC nanoflakes (NFs) are synthesized on the tips of vertically aligned carbon nanotube (VA-CNT) carpets with a hot-filament chemical vapor deposition (HF-CVD) method. The average diameter and height of SiC NFs can be tuned by changing the thickness of per-deposited Si and growth conditions. The growth process of the SiC NFs is suggested to be dominated by a vapor-solid (VS) mechanism. The prepared SiC NFs exhibit quantum-confinement effects, emitting strong violet-blue photoluminescence (PL) under ultraviolet excitation. The PL peak position changes from 410 to 416 nm as the excitation line increases from 290 to 400 nm. This result opens the possibility for the application of the luminescent solid-state freestanding 3C-SiC NFs in photonics as well as photonics/electronics integration. PMID:27184338

  6. Synthesis and Photoluminescence Property of Silicon Carbide Nanowires Via Carbothermic Reduction of Silica

    PubMed Central

    2010-01-01

    Silicon carbide nanowires have been synthesized at 1400 °C by carbothermic reduction of silica with bamboo carbon under normal atmosphere pressure without metallic catalyst. X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy and Fourier transformed infrared spectroscopy were used to characterize the silicon carbide nanowires. The results show that the silicon carbide nanowires have a core–shell structure and grow along <111> direction. The diameter of silicon carbide nanowires is about 50–200 nm and the length from tens to hundreds of micrometers. The vapor–solid mechanism is proposed to elucidate the growth process. The photoluminescence of the synthesized silicon carbide nanowires shows significant blueshifts, which is resulted from the existence of oxygen defects in amorphous layer and the special rough core–shell interface. PMID:20651911

  7. The synthesis of size-controlled 3C-SiC nanoflakes and their photoluminescent properties

    NASA Astrophysics Data System (ADS)

    Fan, Xiujun; Ye, Ruquan; Peng, Zhiwei; Wang, Juanjuan; Fan, Ailing; Guo, Xia

    2016-06-01

    Size-controlled and high-purity 3C-SiC nanoflakes (NFs) are synthesized on the tips of vertically aligned carbon nanotube (VA-CNT) carpets with a hot-filament chemical vapor deposition (HF-CVD) method. The average diameter and height of SiC NFs can be tuned by changing the thickness of per-deposited Si and growth conditions. The growth process of the SiC NFs is suggested to be dominated by a vapor–solid (VS) mechanism. The prepared SiC NFs exhibit quantum-confinement effects, emitting strong violet-blue photoluminescence (PL) under ultraviolet excitation. The PL peak position changes from 410 to 416 nm as the excitation line increases from 290 to 400 nm. This result opens the possibility for the application of the luminescent solid-state freestanding 3C-SiC NFs in photonics as well as photonics/electronics integration.

  8. Photoluminescence properties of novel KBaBP2O8:M (M = Pb2+ and Bi3+) phosphors

    NASA Astrophysics Data System (ADS)

    Han, Bing; Zhang, Jie; Li, Pengju; Li, Jianliang; Bian, Yang; Shi, Hengzhen

    2014-11-01

    A series of novel inorganic phosphors KBa1-xPbxBP2O8 and K1+xBa1-2xBixBP2O8 (0.01 ⩽ x ⩽ 0.08) were synthesized by using a solid-state reaction technique at high-temperature and their photoluminescence properties were investigated. The dependence of the emission intensity on the Pb2+ and Bi3+ concentration for the KBa1-xPbxBP2O8 and K1+xBa1-2xBixBP2O8 was studied, in which the optimal concentration as well as the critical transfer distance Rc for Pb2+ and Bi3+ was obtained and determined. The as-prepared phosphors can be effectively excited with ultraviolet (UV), and exhibit UV - blue emission with large Stokes shift. The above work indicates these phosphors could be potential candidates for application in UV lamps industry.

  9. Photoluminescence Properties of SrMoO4:Eu3+, Sm3+ Nanophosphors Prepared by Sol-Gel Method.

    PubMed

    Xu, Xiaoli; Dong, Wenge; Ding, Jiajun; Feng, Yuanzhang; Zhang, Fang; Ma, Lingli; Peng, Zifei

    2015-07-01

    Novel red light-emitting nanophosphors of SrMoO4:Eu3+, Sm3+ were synthesized by a facile sol-gel method. Particles have sizes in the range of 50-80 nm. The structures, morphologies and optical properties of as-prepared products were characterized by means of X-ray diffraction (XRD), transmission electron microscope (TEM) and photo luminescent (PL). The results indicate that the red emission intensity was enhanced significantly with the increase of Sm3+ doping concentrations. When the mole fraction of Sm3+ is 2%, the emission intensity of red light is the strongest. It has been found that the incorporation of R+(Li+, Na+) into SrMoO4:Eu3+, Sm3+ phosphor could lead to a remarkable increase of photoluminescence. Thus, it is considered to be efficient red-emitting phosphors. PMID:26373154

  10. The photoluminescence and structural properties of (Ce, Yb) co-doped silicon oxides after high temperature annealing

    SciTech Connect

    Heng, C. L. Li, J. T.; Su, W. Y.; Yin, P. G.; Finstad, T. G.

    2015-01-28

    We studied the photoluminescence (PL) and structural properties of Ce and Yb co-doped silicon oxide films after high temperature annealing. The PL spectra of Ce{sup 3+} and Yb{sup 3+} ions were sensitive to the structural variation of the films, and the Yb PL intensities were significantly enhanced especially upon 1200 °C annealing. X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy, indicated that rare earth silicates and the CeO{sub 2} phase had formed in the oxides. The proportions of the phases varied with the “nominal Si-richness” of the films. Energy transfer from the excited Ce{sup 3+} to Yb{sup 3+} can be inferred from both PL excitation and decay spectra.

  11. Synthesis and photoluminescence properties of core-shell structured YVO4:Eu3+@SiO2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Liu, Lina; Xiao, Hongyu; An, Xiuyun; Zhang, Yongsheng; Qin, Ruifei; Liu, Lishuang; Zhang, Dongmei; Sun, Ruirui; Chen, Linfeng

    2015-01-01

    Well-dispersed YVO4:Eu3+ nanoparticles (NPs) of about 8 nm were synthesized by a precipitation reaction and they were coated with SiO2 by a reverse microemulsion method. The thickness of SiO2 shells was altered by changing the molar ratio of tetraethoxysilane (TEOS)/YVO4:Eu3+. The influence of SiO2 coating on the photoluminescence properties of the YVO4:Eu3+ NPs was studied in detail. With the increase of the SiO2 shell thickness, the intensity ratio of 5D0-7F2/5D0-7F1 becomes lower. It was interesting to observe that the quantum yield of naked YVO4:Eu3+ is higher than that of YVO4:Eu3+@SiO2 nanocomposites, and the result is opposite to a previous reference.

  12. Synthesis and photoluminescence properties of Pb2+ doped inorganic borate phosphor NaSr4(BO3)3

    NASA Astrophysics Data System (ADS)

    Chauhan, A. O.; Koparkar, K. A.; Bajaj, N. S.; Omanwar, S. K.

    2016-05-01

    A series of Inorganic borate phosphors NaSr4(BO3)3 doped with Pb2+ was successfully synthesized by modified solid state diffusion method. The crystal structure and the phase purity of sample were characterized by powder X-ray diffraction (XRD). The photoluminescence properties of synthesized materials were investigated using spectrofluorometer at room temperature. The phosphor show strong broad band emission spectra in UVA region maximum at 370 nm under the excitation of 289 nm. The dependence of the emission intensity on the Pb2+ concentration for the NaSr4(BO3)3 were studied in details. The concentration quenching of Pb2+ doped NaSr4(BO3)3 was observed at 0.02 mol. The Stokes shifts of NaSr4(BO3)3: Pb2+ phosphor was calculated to be 7574 cm-1.

  13. Enhancement of photoluminescence properties in ZnO/AlN bilayer heterostructures grown by atomic layer deposition

    SciTech Connect

    Zhu, Shang-Bin; Lu, Hong-Liang Zhang, Yuan; Sun, Qing-Qing; Zhou, Peng; Ding, Shi-Jin; Zhang, David Wei; Zhang, Qiu-Xiang

    2015-01-15

    The AlN/ZnO bilayer heterostructures were deposited on Si (100) substrate by thermal atomic layer deposition. X-ray diffraction results show that the crystallinity of polycrystalline ZnO layer is enhanced by amorphous AlN capping layer. Compared with ZnO thin film, ZnO/AlN bilayer with 10.7 nm AlN capping layer exhibits three times enhanced near band edge (NBE) emission from the photoluminescence measurements. In addition, the near band edge emission from the ZnO can be further increased by ∼10 times through rapid thermal annealing at 600 °C. The underlying mechanisms for the enhancement of the NBE emission after coating AlN capping layer and thermal treatment are discussed. These results suggest that coating of a thin AlN layer and sequential thermal treatments can effectively tailor the luminescence properties of ZnO film.

  14. Study of photoluminescence properties of CaAl2O4: Eu2+ prepared by combustion synthesis method

    NASA Astrophysics Data System (ADS)

    Hingwe, V. S.; Bajaj, N. S.; Omanwar, S. K.

    2016-05-01

    Eu2+ doped alkaline earth metals such as strontium aluminate, calcium aluminate and barium aluminate prepared by using modified combustion synthesis method at 600°c with Urea as fuel. Crystal structure is determined by using XRD and the sample confirmation by using the FTIR. The effect of the host material on the photoluminescence (PL) and phosphorescence properties were studied by using the Hitachi F-7000 spectrofluorimeter equipped with a 450W Xenon lamp, in the range 200-650 nm. The emission spectra of Eu2+ range from 450 to 500nm in the Blue to aqua region and the transition 4f7-4f6 5d1. The observed emission in CaAl2O4 is 440nm.

  15. Photoluminescent properties of Y2O3:Eu3+ phosphors prepared via urea precipitation in non-aqueous solution

    SciTech Connect

    Sun, Yu; Qi, Jason L.; Lee, M.; Lee, Burtrand I.; Samuels, William D.; Exarhos, Gregory J.

    2004-08-01

    Europium-doped yttrium oxide phosphors were prepared by firing precursors obtained by urea solvothermal method. The nature of solvents plays an important role in determining the structure and chemical composition of the precursor compounds. Amorphous hydroxides/carbonates mixture, amorphous carbonates and crystalline carbonates were obtained by urea solvothermal reactions from ethylenediamine, ethanol and aqueous media, respectively. The morphology and particle size distribution of the phosphor particles were studied by SEM and dynamic laser scattering method. The photoluminescence of the phosphor prepared by urea solvothermal method is improved as compared with that of the phosphor obtained by conventional urea homogeneous precipitation method. Urea solvothermal method provides a possible way to tailor the properties of a variety of carbonates and oxides by exploiting the nature of different solvents.

  16. Synthesis, molecular structure and photoluminescence properties of 1,2-diphenyl-4-(3-methoxyphenyl)-1,3-cyclopentadiene

    NASA Astrophysics Data System (ADS)

    Ye, Junwei; Deng, Dai; Gao, Yuan; Wang, Xiaoxiao; Yang, Lijian; Lin, Yuan; Ning, Guiling

    2015-01-01

    1,2-Diphenyl-4-(3-methoxyphenyl)-1,3-cyclopentadiene (DPMPCP) was synthesized via aldol condensation reaction followed by cyclization and dehydration reaction. Its structure was characterized by 1H NMR, 13C NMR spectra, high-resolution mass spectrometry and single-crystal X-ray diffraction. The UV-vis absorption and photoluminescence spectra of DPMPCP in solution and aggregation state were studied. It shows solvent-dependent fluorescence emission and aggregation-induced emission enhancement (AIEE) characteristic when DPMPCP aggregated in water/acetonitrile mixture or in crystals. The crystal structure analysis reveals combination effects of J-aggregation molecule stacking and restriction of intramolecular rotation by intermolecular interactions on AIEE. Additionally, the thermal stability, electrochemical property and DFT calculation of DPMPCP were investigated.

  17. Influence of cation substitution and activator site exchange on the photoluminescence properties of Eu3+-doped quaternary pyrochlore oxides.

    PubMed

    Mahesh, S K; Rao, P Prabhakar; Thomas, Mariyam; Francis, T Linda; Koshy, Peter

    2013-12-01

    Stannate-based pyrochlore-type red phosphors CaGd(1-x)SnNbO7:xEu(3+), Ca(1-y)Sr(y)Gd(1-x)SnNbO7:xEu(3+), and Ca(0.8-x)Sr0.2GdSnNbO(7+δ): xEu(3+) were prepared via conventional solid-state method. Influence of cation substitution and activator site control on the photoluminescence properties of these phosphors are elucidated using powder X-ray diffraction, Rietveld analysis, Raman spectrum analysis, and photoluminescence excitation and emission spectra. The Eu(3+) luminescence in quaternary pyrochlore lattice exemplifies as a very good structural probe for the detection of short-range disorder in the lattice, which otherwise is not detected by normal powder X-ray diffraction technique. The Eu(3+) emission due to magnetic dipole transition ((5)D0-(7)F1 MD) is modified with the increase in europium concentration in the quaternary pyrochlore red phosphors. (5)D0-(7)F1 MD transition splitting is not observable for low Eu(3+) doping because of the short-range disorder in the pyrochlore lattice. Appearance of narrow peaks in Raman spectra confirms that short-range disorder in the crystal lattice disappears with progressive europium doping. By using Sr as a network modifier ion in place of Ca we were able to increase the f-f transition intensities and europium quenching concentration. The influence of effective positive charge of the central Eu(3+) ions when it replaces a metal ion having lower oxidation state such as Ca(2+) was also investigated. The relative intensities of A1g (∼500 cm(-1)) and F2g (∼330 cm(-1)) Raman vibrational modes get inverted when Eu(3+) ions replaces Ca(2+) ions instead of Gd(3+) as trivalent europium ions can attract the electron cloud of oxygen ions strongly in comparison with divalent calcium ions. The influence of positive charge effect of Eu(3+) in Ca0.7Sr0.2GdSnNbO7+δ:0.1Eu(3+) phosphor is greatly strengthened the charge transfer band and (7)F0-(5)L6 transition intensities than that of the Ca0.8Sr0.2Gd0.9SnNbO7:0.1Eu(3+) phosphor. Our

  18. Synthesis and photoluminescence properties of a novel reddish orange-emitting Sm3+-doped strontium borosilicate phosphor

    NASA Astrophysics Data System (ADS)

    Sun, Jianfeng; Ding, Debao; Sun, Jiayue

    2016-08-01

    Sr3-2xSmxNaxB2SiO8 phosphors were synthesized by the solid-state reactions. X-ray diffraction, diffuse reflection, photoluminescence excitation and emission, as well as fluorescence decay measurements were utilized to investigate the structural and spectral properties of the samples. The results indicated that Sr3-2xSmxNaxB2SiO8 phosphors could be efficiently excited by the near-ultraviolet light to realize a novel reddish orange luminescence corresponding to the characteristic transitions 4G5/2→6HJ (J = 5/2, 7/2, 9/2, 11/2) of Sm3+ ions, with a maximum intensity at 600 nm. Based on the theoretical calculation, the dipole-dipole interaction was dominantly involved concentration quenching of Sm3+ in the phosphors, and the critical transfer distance (Rc) was determined to be 13.59 Å. Furthermore, Judd-Ofelt analysis was applied to evaluate three phenomenological Judd-Ofelt intensity parameters (Ωλ, λ = 2, 4, 6), and in turn radiative properties such as radiative transition probabilities (AR), radiative lifetimes (τR) and fluorescence branching ratios (βR) for the excited 4G5/2 luminescent level of Sm3+ ions were determined. Upon 402 nm excitation, the composition-optimized Sr2.90Sm0.05Na0.05B2SiO8 exhibited the preferable photoluminescence intensity and CIE coordinates of (0.534, 0.448). These results suggest that the Sm3+-doped Sr3B2SiO8 phosphors are competitive as the reddish orange-emitting phosphor-converted materials for application in near-ultraviolet-pumped LEDs.

  19. Aqueous solution synthesis and photoluminescence properties of two-dimensional dendritic PbWO{sub 4} nanostructures

    SciTech Connect

    Wang, W.S.; Zhen, L.; Xu, C.Y.; Yang, L.; Shao, W.Z.; Chen, Z.L.

    2014-08-15

    Graphical abstract: PbWO{sub 4} two-dimensional dendritic nanostructures (2DDNs) were prepared at room temperature through a facile aqueous solution route using only Pb(NO{sub 3}){sub 2} and Na{sub 2}WO{sub 4} as reaction reagents and distilled water as solvent. - Highlights: • Two-dimensional dendritic PbWO4 nanostructures were prepared through a facile aqueous solution route at room temperature. • A “two-step” growth mechanism was proposed for the formation of two-dimensional dendritic PbWO4 nanostructures. • The two-dimensional dendritic PbWO4 nanostructures exhibit good photoluminescence properties. - Abstract: PbWO{sub 4} two-dimensional dendritic nanostructures (2DDNs) were prepared at room temperature through a facile aqueous solution route. X-ray diffraction, scanning electron microscope, transmission electron microscope and X-ray energy dispersive spectrometer were used to characterize the obtained samples. The PbWO{sub 4} 2DDN was in one plane, with a nearly circular shape and sizes of ∼10 μm. The PbWO{sub 4} 2DDNs were composed of curved nanowires around 200 nm in diameters, which were connected together to form a network nanostructure. The effects of reaction conditions including the concentration of react reagents, the reaction temperature, and the reaction time were systematically investigated and a possible formation mechanism for the formation of 2DDNs was proposed. The optical properties, such as UV–vis spectra and photoluminescence spectra of PbWO{sub 4}, were studied. The advantages of this synthetic route include the first synthesis of PbWO{sub 4} 2DDNs, simple synthetic procedure, room reaction temperature, and high reproducibility of the process.

  20. A co-precipitation preparation, crystal structure and photoluminescent properties of Er5%:Gd2O3 nanorods

    NASA Astrophysics Data System (ADS)

    Boopathi, G.; Raj, S. Gokul; Kumar, G. Ramesh; Mohan, R.

    2015-06-01

    An inexpensive preparation method is being reported for obtaining erbium doped gadolinium oxide (Er5%:Gd2O3) nanoscale rods. The elongated nanoscale systems, as-formed through a co-precipitation process, are characterized by using X-ray powder diffraction (XRD) patterns, scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) mapping, Ultra Violet-visible (UV-vis.) absorption spectroscopy and photoluminescence (PL) spectroscopy. In addition, the Williamson-Hall (W-H) plot is also performed to distinguish the effect of crystalline size-induced broadening and strain-induced broadening at full-width at half-maximum (FWHM) of the XRD profile. The XRD patterns of as-formed and calcined products show that the phase confirmation. As revealed from the SEM micrographs, the morphology of the products show that the rod-like nanoparticles. The EDX micrographs show that the presence of elements in our samples. The band gap values in calcined samples are found to be in the range of 3.569 eV. Upon 230 nm excitation on calcined samples, three broad emission peaks are observed from PL studies. The possible mechanism for the formation of Er5%:Gd2O3 nanorods is briefly discussed.

  1. A joint experimental and theoretical study on the electronic structure and photoluminescence properties of Al2(WO4)3 powders

    NASA Astrophysics Data System (ADS)

    Batista, F. M. C.; La Porta, F. A.; Gracia, L.; Cerdeiras, E.; Mestres, L.; Siu Li, M.; Batista, N. C.; Andrés, J.; Longo, E.; Cavalcante, L. S.

    2015-02-01

    In this paper, aluminum tungstate Al2(WO4)3 powders were synthesized using the co-precipitation method at room temperature and then submitted to heat treatment processes at different temperatures (100, 200, 400, 800, and 1000 °C) for 2 h. The structure and morphology of the powders were characterized by means of X-ray diffraction (XRD), Rietveld refinement data, and field emission scanning electron microscopy (FE-SEM) images. Their optical properties were examined with ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy and photoluminescence (PL) measurements. XRD patterns and Rietveld refinement data showed that Al2(WO4)3 powders heat treated at 1000 °C for 2 h have a orthorhombic structure with a space group (Pnca) without the presence of deleterious phases. FE-SEM images revealed that these powders are formed by the aggregation of several nanoparticles leading to the growth of microparticles with irregular morphologies and an agglomerated nature. UV-vis spectra indicated that optical band gap energy increased from 3.16 to 3.48 eV) as the processing temperature rose, which was in turn associated with a reduction in intermediary energy levels. First-principle calculations were performed in order to understand the behavior of the PL properties using density functional theory at the B3LYP calculation level on periodic model systems and indicate the presence of stable electronic excited states (singlet). The analyses of the band structures and density of states at both ground and first excited electronic states provide insight into the main features, based on structural and electronic order-disorder effects in octahedral [AlO6] clusters and tetrahedral [WO4] clusters, as constituent building units of this material.

  2. Electrical properties and photoluminescence of SiO{sub x} layers with Si nanocrystals in relation to the SiO{sub x} composition

    SciTech Connect

    Antonova, I. V. Gulyaev, M. B.; Yanovitskaya, Z. Sh.; Volodin, V. A.; Marin, D. V.; Efremov, M. D.; Goldstein, Y.; Jedrzejewski, J.

    2006-10-15

    The photoluminescence and electrical properties are compared for silicon-oxide layers containing Si nanocrystals and having different Si content. The oxide was deposited by co-sputtering of silicon dioxide and silicon with the subsequent annealing for the formation of nanocrystals. Excess Si content in the layer varies along the sample from 6 to 74 vol %. It is found that a charge magnitude determined from the flat-band voltage has a pronounced peak for the excess Si content of about 26%, the largest charge correlating with the highest photoluminescence intensity. The further increase in the excess Si content in oxide leads to a decrease in both the oxide charge and the photoluminescence intensity and to the appearance of percolation conductivity.

  3. Synthesis and photoluminescence properties of Sm3+-doped YAl3(BO3)4 phosphor.

    PubMed

    Kumar, R Satheesh; Ponnusamya, V; Jose, M T

    2014-09-01

    A near ultraviolet excitable phosphor based on Sm3+-doped YAl3(BO3)4 has been synthesized by modified solid-state reaction at 1000°C. The phase purity and photoluminescence (PL) behavior of the phosphor are studied in detail using the powder X-ray diffraction technique and PL measurements. X-ray diffraction reveals that the phase purity of YAl3(BO3)4 critically depends upon the boric acid concentration. The phosphor has strong excitation at 406 nm in the near ultraviolet region (350–420 nm) and its emission peaks were monitored at 564, 599 and 643 nm. Further, detailed PL analysis demonstrates that the substitution of Sm3+ ions at sites of Y3+ and Al3+ ions enhances the PL efficiency of the phosphor appreciably. First, the PL efficiency of YAl3(BO3)4:Sm3+ was compared with commercial (Y,Gd)BO3:Eu3+ red phosphor. The Fourier transform infrared study provides essential information regarding the change in metal–oxygen bond vibrations of the phosphor. The morphology of the phosphor was investigated through scanning electron microscopy, which reveals that the phosphor possessed distorted spherical and rectangular shapes with average grain sizes in the range 0.5–1 μm. PMID:25337617

  4. Photoluminescence and lasing properties of MAPbBr3 single crystals grown from solution

    NASA Astrophysics Data System (ADS)

    Aryal, Sandip; Lafalce, Evan; Zhang, Chuang; Zhai, Yaxin; Vardeny, Z. Valy

    Recent studies of solution-grown single crystals of inorganic-organic hybrid lead-trihalide perovskites have suggested that surface traps may play a significant role in their photophysics. We study electron-hole recombination in single crystal MAPbBr3 through such trap states using cw photoluminescence (PL) and ps transient photoinduced absorption (PA) spectroscopies. By varying the depth of the collecting optics we examined the contributions from surface and bulk radiative recombination. We found a surface dominated PL band at the band-edge that is similar to that observed from polycrystalline thin films, as well as a weaker red-shifted emission band that originates from the bulk crystal. The two PL bands are distinguished in their temperature, excitation intensity and polarization dependencies, as well as their ps dynamics. Additionally, amplified spontaneous emission and crystal-related cavity lasing modes were observed in the same spectral range as the PL band assigned to the surface recombination. This work was funded by AFOSR through MURI Grant RA 9550-14-1-0037.

  5. Tunable photoluminescent and cathodoluminescent properties of ZnO and ZnO:Zn phosphors.

    PubMed

    Wang, Zhenling; Lin, Cuikun; Liu, Xiaoming; Li, Guangzhi; Luo, Yan; Quan, Zewei; Xiang, Hongping; Lin, Jun

    2006-05-18

    ZnO and ZnO:Zn powder phosphors were prepared by the polyol-method followed by annealing in air and reducing gas, respectively. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectra (XPS), electron paramagnetic resonance (EPR), and photoluminescence (PL) and cathodoluminescence (CL) spectra, respectively. The results indicate that all samples are in agreement with the hexagonal structure of the ZnO phase and the particle sizes are in the range of 1-2 microm. The PL and CL spectra of ZnO powders annealed at 950 degrees C in air consist of a weak ultraviolet emission band (approximately 390 nm) and a broad emission band centered at about 527 nm, exhibiting yellow emission color to the naked eyes. When the sample was reduced at the temperatures from 500 to 1050 degrees C, the yellow emission decreased gradually and disappeared completely at 800 degrees C, whereas the ultraviolet emission band became the strongest. Above this temperature, the green emission ( approximately 500 nm) appeared and increased with increasing of reducing temperatures. According to the EPR results and spectral analysis, the yellow and green emissions may arise from the transitions of photogenerated electron close to the conduction band to the deeply trapped hole in the single negatively charged interstitial oxygen ion (Oi(-)) and the single ionized oxygen vacancy (V.O) centers, respectively. PMID:16686492

  6. Synthesis, photoluminescence, thermoluminescence and dosimetry properties of novel phosphor Zn(BO2)2:Tb

    NASA Astrophysics Data System (ADS)

    Li, J.; Zhang, C. X.; Tang, Q.; Zhang, Y. L.; Hao, J. Q.; Su, Q.; Wang, S. B.

    2007-02-01

    Polycrystalline powder samples of terbium doped Zn(BO2)2 phosphors were prepared by solid state reaction in the thermal carbon reducing atmosphere at high temperature. The photoluminescence (PL), three-dimensional (3D) TL emission spectrum and dosimetric characteristics following 60Co gamma-rays irradiation were studied. Characteristic emission bands of Tb3+ at about 490, 543, 584 and 620 nm, attributed to the 5D4→7FJ (J=3, 4, 5, 6) transitions of Tb3+ ions, were observed in the TL and PL emission spectrum. No emission from Tb4+ ions was observed in the TL emission spectrum. The TL-dose response of the powder samples Zn(BO2)2:Tb to 60Co gamma-rays radiation in the dose range from 1 to 100 Gy for clinical dose levels was almost linear. The experiment results showed that Zn(BO2)2:Tb has potential use as the materials of gamma-rays thermoluminescence dosimeter (TLD) for clinical dosimetry.

  7. Photoluminescence properties of ZnS nanoparticles co-doped with Pb 2+ and Cu 2+

    NASA Astrophysics Data System (ADS)

    Yang, Ping; Lü, Mengkai; Xü, Dong; Yuan, Duolong; Zhou, Guangjun

    2001-03-01

    Nanometer-scale ZnS, ZnS:Cu, ZnS:Pb, and ZnS co-doped with Cu 2+ and Pb 2+ have been synthesized using a chemical precipitation method. X-ray diffraction analysis shows that the diameter of the particles is 2-4 nm. These nanocrystals can be doped with copper and lead during the synthesis without altering the X-ray diffraction pattern. However, doping has shifted the luminescence to 530 nm (Cu 2+-doped) and 500-550 nm (co-doped with Cu 2+ and Pb 2+). In the case of ZnS:Pb nanocrystals, a relatively broad emission band (color range from blue to yellow) has been observed and its excitation wavelength shows a red shift. The photoluminescence intensity increases as the ZnS nanoparticles co-doped with Pb 2+ and Cu 2+. The results strongly suggest that doped ZnS nanocrystals, especially two kinds of metals activated ZnS nanocrystals, form a new class of luminescent materials.

  8. Photoluminescence and energy transfer properties of Sm 3+ doped CFB glasses

    NASA Astrophysics Data System (ADS)

    Suresh Kumar, J.; Pavani, K.; Sasikala, T.; Sreenivasa Rao, A.; Giri, Neeraj Kumar; Rai, S. B.; Rama Moorthy, L.

    2011-08-01

    The present paper describes the optical absorption, photoluminescence and lifetime measurements of trivalent samarium doped calcium fluoroborate (CFB) glasses. From the observed energy levels, the free-ion energy level parameters for the 4f 5 electronic configuration of Sm 3+ ion have been evaluated using H FI model. The experimental oscillator strengths of absorption bands have been analyzed to determine the Judd-Ofelt (J-O) parameters. From the evaluated J-O parameters and luminescence data, the radiative parameters such as AR, τR and σe values were obtained from the excited 4G 5/2 level to different lower energy levels. The decay curves of 4G 5/2 → 6H 7/2 transition were analyzed by the Inokuti-Hirayama model assuming dipole-dipole interaction between the dopant ions. The decrease of fluorescence intensities as well as measured lifetimes at higher concentrations has been explained based on energy transfer process through cross-relaxation between Sm 3+ ions.

  9. Direct Band Gap Wurtzite Gallium Phosphide Nanowires

    PubMed Central

    2013-01-01

    The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency. Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong photoluminescence at a wavelength of 594 nm with short lifetime, typical for a direct band gap. Furthermore, by incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555–690 nm). This approach of crystal structure engineering enables new pathways to tailor materials properties enhancing the functionality. PMID:23464761

  10. A green chemical approach to the synthesis of photoluminescent ZnO hollow spheres with enhanced photocatalytic properties

    SciTech Connect

    Patrinoiu, Greta; Tudose, Madalina; Calderon-Moreno, Jose Maria; Birjega, Ruxandra; Budrugeac, Petru; Ene, Ramona; Carp, Oana

    2012-02-15

    ZnO hollow spheres have been synthesized by a simple and environmentally friendly template assisted route. Starch-derived carbonaceous spheres were used as template, impregnated with Zn(CH{sub 3}COO){sub 2}{center_dot}2H{sub 2}O to obtain zinc-containing precursor spheres and thermally treatment at 600 Degree-Sign C, yielding hollow ZnO spherical shells. The precursor spheres and hollow shells were characterized by X-ray diffraction, FTIR spectroscopy, scanning electron microscopy, thermal analysis and room-temperature photoluminescence measurements. The hollow spherical shells with diameters of {approx}150 nm and wall thickness of {approx}20 nm, are polycrystalline, with a mean crystallite size of 22 nm, exhibiting interesting emission features, with a wide multi-peak band covering blue and green regions of the visible spectrum. The photocatalytic activities (under UV and visible light irradiations) of the ZnO spherical shells evaluated for the phenol degradation reaction in aqueous solutions are outstanding, a total phenol conversion being registered in the case of UV irradiation experiments. - Graphical abstract: The photocatalytic reaction initiated by the photoexcitation of the semiconductor (ZnO), leads to the formation of electron-hole, while part of the electron-hole pairs recombine, some holes combine with water to form {center_dot}OH radicals and some electrons convert oxygen to super oxide radical ({center_dot}O{sub 2}{sup -}). Highlights: Black-Right-Pointing-Pointer Green synthesis of ZnO hollow spheres. Black-Right-Pointing-Pointer Starch-derived carbonaceous spheres as spherical hard template. Black-Right-Pointing-Pointer ZnO hollow spheres with notable visible photoluminescence properties. Black-Right-Pointing-Pointer ZnO hollow spheres with photocatalytical activity in degradation/mineralization of phenol.

  11. Biological fabrication of nanostructured silicon-germanium photonic crystals possessing unique photoluminescent and electroluminescent properties

    NASA Astrophysics Data System (ADS)

    Rorrer, Gregory L.; Jeffryes, Clayton; Chang, Chih-hung; Lee, Doo-Hyoung; Gutu, Timothy; Jiao, Jun; Solanki, Raj

    2007-09-01

    Diatoms are single-celled algae which possess silica shells called "frustules" that contain periodic submicron scale features. A diatom cell culture process was used to fabricate a two-dimensional photonic crystal slab of Ge-doped biosilica that possessed 120 nm holes, 330 nm lattice constant, and dielectric constant of 8.5. This material was integrated into an electroluminescent (EL) device by spin coating of the frustules onto indium tin oxide, followed by atomic layer deposition of 400 nm hafnium silicate. No photonic band gap was predicted. However, the EL spectrum possessed resonant UV line emissions that were consistent with photonic band calculations. An EL band gap between 500-640 nm was also observed between blue and red EL line emissions. These EL characteristics have not been observed previously, and are unique to the diatom photonic crystal. This study represents a first step towards the realization of optoelectronic devices which utilize nanoscale components fabricated through cell culture.

  12. Tailoring magnetic and photoluminescence properties in ZnS/ZnO core/shell nanostructures through Cr doping

    NASA Astrophysics Data System (ADS)

    Chawla, Santa; Sharma, Simmi; Kotnala, R. K.

    2013-11-01

    Work on doped inverted core/shell semiconductor structure and study of their magnetic and luminescence properties is very rare. We have successfully prepared core/shell (C/S) nanostructure of important semiconductors ZnS core/ZnO shell with doping of chromium in both core and shell regions for tailoring magnetic and luminescence properties. Cooperative exchange of pinned spins at the interface of core and shell magnetic regions lead to ferromagnetism in ZnS:Cr/ZnO:Cr C/S nanoparticles (NP) at room temperature. Ferromagnetic interaction enhances at low temperature. Growth of hexagonal ZnO shell on cubic ZnS NPs in coprepitous aqueous solution has been confirmed by XRD and HRTEM analysis. Substitutional transition metal Cr in ZnS core and/or ZnO shell region could induce magnetic moments, create spin ordering and pinning while on C/S interface and also domain alignment leading to different magnetic states in varied C/S architecture. Cr also induces blue photoluminescence in doped ZnS/ZnO C/S NPs thus paving a possibility of tailoring multifunctional properties in C/S semiconductors architecture.

  13. Band gap anomaly and topological properties in lead chalcogenides

    NASA Astrophysics Data System (ADS)

    Simin, Nie; Xiao, Yan Xu; Gang, Xu; Zhong, Fang

    2016-03-01

    Band gap anomaly is a well-known issue in lead chalcogenides PbX (X = S, Se, Te, Po). Combining ab initio calculations and tight-binding (TB) method, we have studied the band evolution in PbX, and found that the band gap anomaly in PbTe is mainly related to the high on-site energy of Te 5s orbital and the large s-p hopping originated from the irregular extended distribution of Te 5s electrons. Furthermore, our calculations show that PbPo is an indirect band gap (6.5 meV) semiconductor with band inversion at L point, which clearly indicates that PbPo is a topological crystalline insulator (TCI). The calculated mirror Chern number and surface states double confirm this conclusion. Project supported by the National Natural Science Foundation of China (Grant No. 11204359), the National Basic Research Program of China (Grant No. 2013CB921700), and the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB07020100).

  14. Nanoscale morphology of multilayer PbTe/CdTe heterostructures and its effect on photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Karczewski, G.; Szot, M.; Kret, S.; Kowalczyk, L.; Chusnutdinow, S.; Wojtowicz, T.; Schreyeck, S.; Brunner, K.; Schumacher, C.; Molenkamp, L. W.

    2015-03-01

    We study nanoscale morphology of PbTe/CdTe multilayer heterostuctures grown by molecular beam epitaxy on hybrid GaAs/CdTe (100) substrates. Nominally, the structures consist of 25 repetitions of subsequently deposited CdTe and PbTe layers with comparable thicknesses of 21 and 8 nm, respectively. However, the morphology of the resulting structures crucially depends on the growth temperature. The two-dimensional layered, superlattice-like character of the structures remains preserved only when grown at low substrate temperatures, such as 230 °C. The samples grown at the slightly elevated temperature of 270 °C undergo a morphological transformation to structures consisting of CdTe and PbTe pillars and columns oriented perpendicular to the substrate. Although the pillar-like objects are of various shapes and dimensions these structures exhibit exceptionally strong photoluminescence in the near infrared spectral region. At the higher growth temperature of 310 °C, PbTe and CdTe separate completely forming thick layers oriented longitudinally to the substrate plane. The observed topological transformations are driven by thermally activated atomic diffusion in the solid state phase. The solid state phase remains fully coherent during the processes. The observed topological transitions leading to the material separation in PbTe/CdTe system could be regarded as an analog of spinodal decomposition of an immiscible solid state solution and thus they can be qualitatively described by the Cahn-Hillard model as proposed by Groiss et al (2014 APL Mater. 2 012105).

  15. Photoluminescence properties and crystallization of silicon quantum dots in hydrogenated amorphous Si-rich silicon carbide films

    NASA Astrophysics Data System (ADS)

    Wen, Guozhi; Zeng, Xiangbin; Wen, Xixin; Liao, Wugang

    2014-04-01

    Silicon quantum dots (QDs) embedded in hydrogenated amorphous Si-rich silicon carbide (α-SiC:H) thin films were realized by plasma-enhanced chemical vapor deposition process and post-annealing. Fluorescence spectroscopy was used to characterize the room-temperature photoluminescence properties. X-ray photoelectron spectroscopy was used to analyze the element compositions and bonding configurations. Ultraviolet visible spectroscopy, Raman scattering, and high-resolution transmission electron microscopy were used to display the microstructural properties. Photoluminescence measurements reveal that there are six emission sub-bands, which behave in different ways. The peak wavelengths of sub-bands P1, P2, P3, and P6 are pinned at about 425.0, 437.3, 465.0, and 591.0 nm, respectively. Other two sub-bands, P4 is red-shifted from 494.6 to 512.4 nm and P5 from 570.2 to 587.8 nm with temperature increasing from 600 to 900 °C. But then are both blue-shifted, P4 to 500.2 nm and P5 to 573.8 nm from 900 to 1200 °C. The X-ray photoelectron spectroscopy analysis shows that the samples are in Si-rich nature, Si-O and Si-N bonds consumed some silicon atoms. The structure characterization displays that a separation between silicon phase and SiC phase happened; amorphous and crystalline silicon QDs synthesized with increasing the annealing temperature. P1, P2, P3, and P6 sub-bands are explained in terms of defect-related emission, while P4 and P5 sub-bands are explained in terms of quantum confinement effect. A correlation between the peak wavelength shift, as well as the integral intensity of the spectrum and crystallization of silicon QDs is supposed. These results help clarify the probable luminescence mechanisms and provide the possibility to optimize the optical properties of silicon QDs in Si-rich α-SiC: H materials.

  16. Photoluminescence properties and crystallization of silicon quantum dots in hydrogenated amorphous Si-rich silicon carbide films

    SciTech Connect

    Wen, Guozhi; Zeng, Xiangbin Wen, Xixin; Liao, Wugang

    2014-04-28

    Silicon quantum dots (QDs) embedded in hydrogenated amorphous Si-rich silicon carbide (α-SiC:H) thin films were realized by plasma-enhanced chemical vapor deposition process and post-annealing. Fluorescence spectroscopy was used to characterize the room-temperature photoluminescence properties. X-ray photoelectron spectroscopy was used to analyze the element compositions and bonding configurations. Ultraviolet visible spectroscopy, Raman scattering, and high-resolution transmission electron microscopy were used to display the microstructural properties. Photoluminescence measurements reveal that there are six emission sub-bands, which behave in different ways. The peak wavelengths of sub-bands P1, P2, P3, and P6 are pinned at about 425.0, 437.3, 465.0, and 591.0 nm, respectively. Other two sub-bands, P4 is red-shifted from 494.6 to 512.4 nm and P5 from 570.2 to 587.8 nm with temperature increasing from 600 to 900 °C. But then are both blue-shifted, P4 to 500.2 nm and P5 to 573.8 nm from 900 to 1200 °C. The X-ray photoelectron spectroscopy analysis shows that the samples are in Si-rich nature, Si-O and Si-N bonds consumed some silicon atoms. The structure characterization displays that a separation between silicon phase and SiC phase happened; amorphous and crystalline silicon QDs synthesized with increasing the annealing temperature. P1, P2, P3, and P6 sub-bands are explained in terms of defect-related emission, while P4 and P5 sub-bands are explained in terms of quantum confinement effect. A correlation between the peak wavelength shift, as well as the integral intensity of the spectrum and crystallization of silicon QDs is supposed. These results help clarify the probable luminescence mechanisms and provide the possibility to optimize the optical properties of silicon QDs in Si-rich α-SiC: H materials.

  17. Further improvements in program to calculate electronic properties of narrow band gap materials

    NASA Technical Reports Server (NTRS)

    Patterson, James D.

    1991-01-01

    Research into the properties of narrow band gap materials during the period 15 Jun. to 15 Dec. 1991 is discussed. Abstracts and bibliographies from papers presented during this period are reported. Graphs are provided.

  18. Large-Scale Synthesis and Systematic Photoluminescence Properties of Monolayer MoS2 on Fused Silica.

    PubMed

    Wan, Yi; Zhang, Hui; Zhang, Kun; Wang, Yilun; Sheng, Bowen; Wang, Xinqiang; Dai, Lun

    2016-07-20

    Monolayer MoS2, with fascinating mechanical, electrical, and optical properties, has generated enormous scientific curiosity and industrial interest. Controllable and scalable synthesis of monolayer MoS2 on various desired substrates has significant meaning in both basic scientific research and device application. Recent years have witnessed many advances in the direct synthesis of single-crystalline MoS2 flakes or their polycrystalline aggregates on numerous diverse substrates, such as SiO2-Si, mica, sapphire, h-BN, and SrTiO3, etc. In this work, we used the dual-temperature-zone atmospheric-pressure chemical vapor deposition method to directly synthesize large-scale monolayer MoS2 on fused silica, the most ordinary transparent insulating material in daily life. We systematically investigated the photoluminescence (PL) properties of monolayer MoS2 on fused silica and SiO2-Si substrates, which have different thermal conductivity coefficients and thermal expansion coefficients. We found that there exists a stronger strain on monolayer MoS2 grown on fused silica, and the strain becomes more obvious as temperature decreases. Moreover, the monolayer MoS2 grown on fused silica exhibits the unique trait of a fractal shape with tortuous edges and has stronger adsorbability. The monolayer MoS2 grown on fused silica may find application in sensing, energy storage, and transparent optoelectronics, etc. PMID:27338112

  19. Composition-dependent photoluminescence properties of CuInS2/ZnS core/shell quantum dots

    NASA Astrophysics Data System (ADS)

    Hua, Jie; Du, Yuwei; Wei, Qi; Yuan, Xi; Wang, Jin; Zhao, Jialong; Li, Haibo

    2016-06-01

    CuInS2/ZnS (CIS/ZnS) core/shell quantum dots (QDs) with various Cu/In ratios were synthesized using the hot-injection method, and their photoluminescence (PL) properties were investigated by measuring steady-state and time-resolved PL spectroscopy. The emission peak of the CIS/ZnS QDs were tuned from 680 to 580 nm by decreasing the Cu/In precursor ratio from 1/1 to 1/9. As the Cu/In ratio decreases, the PL lifetimes and PL quantum yields (QYs) of CIS/ZnS core/shell QDs increased firstly and then decreased. Two dominant radiative recombination processes were postulated to analyze composition-dependent PL properties, including the recombination from a quantized conduction band to deep defects state and donor-acceptor pair (DAP) recombination. The decrease of PL efficiency resulted from high density defects and traps, which formed at the interface between CIS core and ZnS shell due to the large off-stoichiometry composition. The PL intensity and peak energy for CIS/ZnS core/shell QDs as a function of temperature were also provided. The thermal quenching further confirmed that the PL emission of CIS/ZnS QDs did not come from the recombination of excitons but from the recombination of many kinds of intrinsic defects inside the QDs as emission centers.

  20. Photoluminescence properties of MgY4Si3O13:Gd3+, Tb3+ under vacuum ultraviolet excitation

    NASA Astrophysics Data System (ADS)

    Zhao, Wenyu; An, Shengli; Fan, Bin; Li, Songbo

    2013-07-01

    Gd3+ and Tb3+ co-doped MgY4Si3O13 green phosphors were prepared by a solid-state reaction. The photoluminescence properties in vacuum ultraviolet-visible (VUV-vis) range and decay properties were investigated in details. The f-d transition of Gd3+ ions and spin-allowed f-d transition of Tb3+ ions locate at about 134 nm and 239 nm, respectively. Two charge transfer bands of O2- → Gd3+ and O2- → Tb3+ overlap at about 155 nm. Some f-f transition of Tb3+ and Gd3+ ions are confirmed in VUV-vis range. Upon excitation at 172 nm, the optimal composition of MgY3.3Si3O13:0.5Gd3+, 0.2Tb3+ phosphor exhibits the characteristic transitions of Gd3+ and Tb3+ with chromaticity coordinate of (0.2849, 0.5843). The phosphor has a shorter decay time (2.13 ms) than that of Zn2SiO4:Mn2+ (4.56 ms). The results suggest that this green phosphor is a potential candidate for mercury-free luminescence lamps and plasma display panels (PDPs) application.

  1. New metal based drug as a therapeutic agent: Spectral, electrochemical, DNA-binding, surface morphology and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Muslu, Harun; Gölcü, Ayşegül

    2015-07-01

    Cu(II) complexes of non-steroidal anti-inflammatory drug (NSAID) Meloxicam (H2MLX) was synthesized and characterized via spectroscopic and analytical techniques. The thermal behavior of the complex was also analyzed. The photoluminescence properties of the compounds were analyzed under different conditions. The electrochemical properties of both ligand and complex have been analyzed by Cyclic Voltammetry (CV) using glassy carbon electrode. The biological activities of the compounds were evaluated through examining their capacity to bind to fish sperm double strand DNA (FSdsDNA) with absorption spectroscopy and differential pulse voltammetry (DPV). Absorption studies of the interaction of the H2MLX and its Cu(II) complex with FSdsDNA have indicated that these compounds could bind to FSdsDNA, and the binding constants were calculated. The morphology of the FSdsDNA, H2MLX, and Cu(II) complex were analyzed thanks to using scanning electron microscopy (SEM). In the DPV technique, pencil graphite electrode was used as a working electrode. The decrease in the intensity of the guanine oxidation signals was used as an indicator for the interaction mechanism.

  2. Structural and electronic properties of GaAs and GaP semiconductors

    SciTech Connect

    Rani, Anita; Kumar, Ranjan

    2015-05-15

    The Structural and Electronic properties of Zinc Blende phase of GaAs and GaP compounds are studied using self consistent SIESTA-code, pseudopotentials and Density Functional Theory (DFT) in Local Density Approximation (LDA). The Lattice Constant, Equillibrium Volume, Cohesive Energy per pair, Compressibility and Band Gap are calculated. The band gaps calcultated with DFT using LDA is smaller than the experimental values. The P-V data fitted to third order Birch Murnaghan equation of state provide the Bulk Modulus and its pressure derivatives. Our Structural and Electronic properties estimations are in agreement with available experimental and theoretical data.

  3. Time resolved photoluminescence spectroscopy of narrow gap Hg{sub 1−x}Cd{sub x}Te/Cd{sub y}Hg{sub 1−y}Te quantum well heterostructures

    SciTech Connect

    Morozov, S. V.; Rumyantsev, V. V. Antonov, A. V.; Kadykov, A. M.; Maremyanin, K. V.; Kudryavtsev, K. E.; Gavrilenko, V. I.; Mikhailov, N. N.; Dvoretskii, S. A.

    2014-07-14

    Photoluminescence (PL) spectra and kinetics of narrow gap Hg{sub 1−x}Cd{sub x}Te/Cd{sub y}Hg{sub 1−y}Te quantum well (QW) heterostructures grown by molecular beam epitaxy technique are studied. Interband PL spectra are observed from 18 K up to the room temperature. Time resolved studies reveal an additional PL line with slow kinetics (7 μs at 18 K) related to deep defect states in barrier layers. These states act as traps counteracting carrier injection into QWs. The decay time of PL signal from QW layers is about 5 μs showing that gain can be achieved at wavelengths 10–20 μm by placing such QWs in HgCdTe structures with waveguides.

  4. Systhesis, phase transformation and photoluminescence properties of Eu:La(1-x)Gd(x)VO4 nanofibers by electrospinning method.

    PubMed

    Huang, Zuocai; Huang, Siya; Ou, Gang; Pan, Wei

    2012-08-21

    One dimensional Eu:La(1-x)Gd(x)VO(4) nanofibers were successfully prepared via an electrospinning method. Thermogravimetry and differential scanning calorimeter (TG-DSC), X-ray diffraction, Raman spectroscopy, scanning electron microscopy and photoluminescence were used to characterize the samples. The nanofibers crystallized well below 600 °C and with the increase of Gd contents, the nanofibers crystallized in a zircon-type structure. The Raman spectra shifted to higher frequency with the increase of Gd content for zircon Eu:La(1-x)Gd(x)VO(4). The peaks of photoluminescence spectra shift towards longer wavelength when Gd replaces La and when x = 0.4, the photoluminescence intensity reaches its maximum value. The band structure and density of states of m-LaVO(4), t-LaVO(4), t-LaGdVO(4) and t-GdVO(4) were calculated by local-spin density approximation (LSDA) band theory with Hubbard term of U. The band gap of t-LaGdVO(4) is just the average of t-LaVO(4) and t-GdVO(4). In t-LaGdVO(4), La 5p states are highly localized. PMID:22772795

  5. Synthesis of nitrogen-doping carbon dots with different photoluminescence properties by controlling the surface states.

    PubMed

    Yuan, Yun Huan; Liu, Ze Xi; Li, Rong Sheng; Zou, Hong Yan; Lin, Min; Liu, Hui; Huang, Cheng Zhi

    2016-03-28

    Surface states of carbon dots (CDs) are critical to the photoemission properties of CDs. By carefully adjusting the reaction conditions in a hydrothermal synthesis route, we have prepared a series of CDs with excitation-dependent emission (EDE) and excitation-independent emission (EIE) properties by controlling the content of nitrogen elements, confirming that the characteristic optical properties of CDs originate from their energy levels. It has been found that surface-passivation of the as-prepared CDs by nitrogen doping can improve the emission efficiency and be beneficial to EIE features due to the single electron transition resulting from the single functional groups. And the as-prepared CDs can specifically bind with Hg(2+) with the emission quenched because of the electron transfer from the LUMO levels of CDs to Hg(2+). PMID:26955862

  6. Synthesis of nitrogen-doping carbon dots with different photoluminescence properties by controlling the surface states

    NASA Astrophysics Data System (ADS)

    Yuan, Yun Huan; Liu, Ze Xi; Li, Rong Sheng; Zou, Hong Yan; Lin, Min; Liu, Hui; Huang, Cheng Zhi

    2016-03-01

    Surface states of carbon dots (CDs) are critical to the photoemission properties of CDs. By carefully adjusting the reaction conditions in a hydrothermal synthesis route, we have prepared a series of CDs with excitation-dependent emission (EDE) and excitation-independent emission (EIE) properties by controlling the content of nitrogen elements, confirming that the characteristic optical properties of CDs originate from their energy levels. It has been found that surface-passivation of the as-prepared CDs by nitrogen doping can improve the emission efficiency and be beneficial to EIE features due to the single electron transition resulting from the single functional groups. And the as-prepared CDs can specifically bind with Hg2+ with the emission quenched because of the electron transfer from the LUMO levels of CDs to Hg2+.Surface states of carbon dots (CDs) are critical to the photoemission properties of CDs. By carefully adjusting the reaction conditions in a hydrothermal synthesis route, we have prepared a series of CDs with excitation-dependent emission (EDE) and excitation-independent emission (EIE) properties by controlling the content of nitrogen elements, confirming that the characteristic optical properties of CDs originate from their energy levels. It has been found that surface-passivation of the as-prepared CDs by nitrogen doping can improve the emission efficiency and be beneficial to EIE features due to the single electron transition resulting from the single functional groups. And the as-prepared CDs can specifically bind with Hg2+ with the emission quenched because of the electron transfer from the LUMO levels of CDs to Hg2+. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00402d

  7. γ irradiation induced effects on bismuth active centres and related photoluminescence properties of Bi/Er co-doped optical fibres.

    PubMed

    Sporea, D; Mihai, L; Neguţ, D; Luo, Yanhua; Yan, Binbin; Ding, Mingjie; Wei, Shuen; Peng, Gang-Ding

    2016-01-01

    We investigate the effects of γ irradiation on bismuth active centres (BACs) and related photoluminescence properties of bismuth/erbium co-doped silica fibre (BEDF), [Si] ~28, [Ge] ~1.60, [Al] ~0.10, [Er] ~ <0.10 and [Bi] ~0.10 atom%, fabricated by in-situ solution doping and Modified Chemical Vapor Deposition (MCVD). The samples were irradiated at 1 kGy, 5 kGy, 15 kGy, 30 kGy and 50 kGy doses, and dose rate of 5.5 kGy/h, at room temperature. The optical properties of BEDF samples are tested before and after γ irradiation. We found that high dose γ irradiation could significantly influence the formation and composition of BACs and their photoluminescence performance, as important changes in absorption and emission properties associated with the 830 nm pump produces the direct evidence of γ irradiation effects on BAC-Si. We notice that the saturable to unsaturable absorption ratio at pump wavelength could be increased with high dose γ irradiation, indicating that emission and pump efficiency could be increased by γ irradiation. Our experimental results also reveal good radiation survivability of the BEDF under low and moderate γ irradiation. Our investigation suggests the existence of irradiation related processing available for tailoring the photoluminescence properties and performance of bismuth doped/co-doped fibres. PMID:27440386

  8. γ irradiation induced effects on bismuth active centres and related photoluminescence properties of Bi/Er co-doped optical fibres

    NASA Astrophysics Data System (ADS)

    Sporea, D.; Mihai, L.; Neguţ, D.; Luo, Yanhua; Yan, Binbin; Ding, Mingjie; Wei, Shuen; Peng, Gang-Ding

    2016-07-01

    We investigate the effects of γ irradiation on bismuth active centres (BACs) and related photoluminescence properties of bismuth/erbium co-doped silica fibre (BEDF), [Si] ~28, [Ge] ~1.60, [Al] ~0.10, [Er] ~ <0.10 and [Bi] ~0.10 atom%, fabricated by in-situ solution doping and Modified Chemical Vapor Deposition (MCVD). The samples were irradiated at 1 kGy, 5 kGy, 15 kGy, 30 kGy and 50 kGy doses, and dose rate of 5.5 kGy/h, at room temperature. The optical properties of BEDF samples are tested before and after γ irradiation. We found that high dose γ irradiation could significantly influence the formation and composition of BACs and their photoluminescence performance, as important changes in absorption and emission properties associated with the 830 nm pump produces the direct evidence of γ irradiation effects on BAC-Si. We notice that the saturable to unsaturable absorption ratio at pump wavelength could be increased with high dose γ irradiation, indicating that emission and pump efficiency could be increased by γ irradiation. Our experimental results also reveal good radiation survivability of the BEDF under low and moderate γ irradiation. Our investigation suggests the existence of irradiation related processing available for tailoring the photoluminescence properties and performance of bismuth doped/co-doped fibres.

  9. γ irradiation induced effects on bismuth active centres and related photoluminescence properties of Bi/Er co-doped optical fibres

    PubMed Central

    Sporea, D.; Mihai, L.; Neguţ, D.; Luo, Yanhua; Yan, Binbin; Ding, Mingjie; Wei, Shuen; Peng, Gang-Ding

    2016-01-01

    We investigate the effects of γ irradiation on bismuth active centres (BACs) and related photoluminescence properties of bismuth/erbium co-doped silica fibre (BEDF), [Si] ~28, [Ge] ~1.60, [Al] ~0.10, [Er] ~ <0.10 and [Bi] ~0.10 atom%, fabricated by in-situ solution doping and Modified Chemical Vapor Deposition (MCVD). The samples were irradiated at 1 kGy, 5 kGy, 15 kGy, 30 kGy and 50 kGy doses, and dose rate of 5.5 kGy/h, at room temperature. The optical properties of BEDF samples are tested before and after γ irradiation. We found that high dose γ irradiation could significantly influence the formation and composition of BACs and their photoluminescence performance, as important changes in absorption and emission properties associated with the 830 nm pump produces the direct evidence of γ irradiation effects on BAC-Si. We notice that the saturable to unsaturable absorption ratio at pump wavelength could be increased with high dose γ irradiation, indicating that emission and pump efficiency could be increased by γ irradiation. Our experimental results also reveal good radiation survivability of the BEDF under low and moderate γ irradiation. Our investigation suggests the existence of irradiation related processing available for tailoring the photoluminescence properties and performance of bismuth doped/co-doped fibres. PMID:27440386

  10. Effect of the Nd content on the structural and photoluminescence properties of silicon-rich silicon dioxide thin films

    PubMed Central

    2011-01-01

    In this article, the microstructure and photoluminescence (PL) properties of Nd-doped silicon-rich silicon oxide (SRSO) are reported as a function of the annealing temperature and the Nd concentration. The thin films, which were grown on Si substrates by reactive magnetron co-sputtering, contain the same Si excess as determined by Rutherford backscattering spectrometry. Fourier transform infrared (FTIR) spectra show that a phase separation occurs during the annealing because of the condensation of the Si excess resulting in the formation of silicon nanoparticles (Si-np) as detected by high-resolution transmission electron microscopy and X-ray diffraction (XRD) measurements. Under non-resonant excitation at 488 nm, our Nd-doped SRSO films simultaneously exhibited PL from Si-np and Nd3+ demonstrating the efficient energy transfer between Si-np and Nd3+ and the sensitizing effect of Si-np. Upon increasing the Nd concentration from 0.08 to 4.9 at.%, our samples revealed a progressive quenching of the Nd3+ PL which can be correlated with the concomitant increase of disorder within the host matrix as shown by FTIR experiments. Moreover, the presence of Nd-oxide nanocrystals in the highest Nd-doped sample was established by XRD. It is, therefore, suggested that the Nd clustering, as well as disorder, are responsible for the concentration quenching of the PL of Nd3+. PMID:21711673

  11. Photoluminescent properties of Tb3+ doped GdSrAl3O7 nanophosphor using solution combustions synthesis

    NASA Astrophysics Data System (ADS)

    Khatkar, Satyender Pal; Singh, Sonika; Lohra, Sheetal; Khatkar, Avni; Taxak, Vinod

    2015-05-01

    A color tunable terbium doped GdSrAl3O7 nanophosphor has been synthesized at low temperature using solution combustion synthesis. The photoluminescent properties of nanophosphors have been explored by analyzing their excitation and emission spectra alongwith their decay curves. The emission spectra exhibit dominating green light at 544 nm due to 5D4→7F5 transition of Tb3+ ions in GdSrAl3O7 on excitation by UV light of 239 nm. Furthermore, the luminescence in Gd( 1- x)SrAl3O7: xTb3+nanophosphors shifted from blue to green color by properly tuning the concentration of terbium ions. Decay curves indicate that non-radiative cross-relaxation is primarily responsible for concentration quenching phenomenon in the GdSrAl3O7 host. X-ray diffraction (XRD) analysis confirmed that single tetragonal phased nanophosphor could be readily obtained at low temperature 550°C. The smooth surfaced nanocrystals with particle size of 45 - 50 nm have also been examined by transmission electron microscopy (TEM). All these features augmented the probability of GdSrAl3O7: Tb3+ nanophosphor for potential applications in optical devices. [Figure not available: see fulltext.

  12. Crystal structure, thermally stability and photoluminescence properties of novel Sr10(PO4)6O:Eu2+ phosphors

    NASA Astrophysics Data System (ADS)

    Guo, Qingfeng; Liao, Libing; Mei, Lefu; Liu, Haikun

    2015-03-01

    A series of novel luminescent phosphors Sr10(PO4)6O:Eu2+ with apatite structure were synthesized via a high temperature solid-state reaction. The phase structure, photoluminescence (PL) properties, the PL thermal stability, as well as the fluorescence decay curves of the samples were investigated to characterize the resulting samples, and the selected Sr9.97(PO4)6O:0.03Eu2+ phosphor exhibits strong thermal quenching resistance, retaining the luminance of 88.73% at 150 °C. The quenching concentration of Eu2+ in Sr10(PO4)6O was about 0.03 attributing to the dipole-quadrupole interaction. The Sr10(PO4)6O:Eu2+ phosphor exhibited a broad-band blue emission at 439 nm upon excitation at 346 nm. The results indicate that Sr10(PO4)6O:Eu2+ phosphors have potential applications as near UV-convertible phosphors for white-light UV LEDs.

  13. Anodic luminescence, structural, photoluminescent, and photocatalytic properties of anodic oxide films grown on niobium in phosphoric acid

    NASA Astrophysics Data System (ADS)

    Stojadinović, Stevan; Tadić, Nenad; Radić, Nenad; Stefanov, Plamen; Grbić, Boško; Vasilić, Rastko

    2015-11-01

    This article reports on properties of oxide films obtained by anodization of niobium in phosphoric acid before and after the dielectric breakdown. Weak anodic luminescence of barrier oxide films formed during the anodization of niobium is correlated to the existence of morphological defects in the oxide layer. Small sized sparks generated by dielectric breakdown of formed oxide film cause rapid increase of luminescence intensity. The luminescence spectrum of obtained films on niobium under spark discharging is composed of continuum radiation and spectral lines caused by electronic spark discharging transitions in oxygen and hydrogen atoms. Oxide films formed before the breakdown are amorphous, while after the breakdown oxide films are partly crystalline and mainly composed of Nb2O5 hexagonal phase. The photocatalytic activity of obtained oxide films after the breakdown was investigated by monitoring the degradation of methyl orange. Increase of the photocatalytic activity with time is related to an increase of oxygen vacancy defects in oxide films formed during the process. Also, higher concentration of oxygen vacancy defects in oxide films results in higher photoluminescence intensity.

  14. Effect of manganese concentration on photoluminescence properties of Zn2SiO4:Mn nanophosphor material

    NASA Astrophysics Data System (ADS)

    Omri, K.; El Mir, L.

    2014-06-01

    Nanophosphor β-Zn2SiO4:Mn with bright yellow light emission were synthesized by a sol-gel process. These samples were prepared by a simple solid-phase reaction under natural atmosphere at 1500 °C after the incorporation of ZnO:Mn nanoparticles, in silica monolith. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the phase purity, particle size and morphology. In addition photoluminescence (PL) was used for optical study. The PL spectrum for the β-Zn2SiO4:Mn nanophosphors showed a dominant peak at 574 nm, which originated from the 4T1 → 6A1 transitions of Mn2+ ions. The level of manganese doping did not greatly affect the crystallinity, but did affect the luminescence of nanophosphors. Upon 255 nm excitation, the luminescence decay time of the yellow emission of β-Zn2SiO4 with a Mn doping concentration of 2 at.% around 574 nm is 13 ms. The characteristics of crystallinity, morphology and luminescence property of the obtained nanophosphors were investigated.

  15. Photoluminescence properties of Ho{sup 3+} ion in lithium-fluoroborate glass containing different modifier oxides

    SciTech Connect

    Balakrishna, A. Rajesh, D. Ratnakaram, Y. C.

    2014-04-24

    Trivalent holmium (0.5 mol%) doped lithium fluoro-borate glasses with the chemical compositions 49.5Li{sub 2}B{sub 4}O{sub 7−}20BaF{sub 2−}10NaF−20MO (where M=Mg, Ca, Cd and Pb), 49.5Li{sub 2}B{sub 4}O{sub 7−}20BaF{sub 2−}10NaF−10MgO−10CaO and 49.5Li{sub 2}B{sub 4}O{sub 7−}20BaF{sub 2−}10NaF−10CdO−10PbO were synthesized and investigated their photoluminescence properties. The variation in chemical composition by varying modifier oxides causes changes in the structural spectroscopic behavior of Ho{sup 3+} ions. These changes are examined by UV-VIS- NIR and luminescence spectroscopic techniques. The visible luminescence spectra were obtained by exciting samples at 409 nm radiation.

  16. Carboxylate-modulated two novel Ag(I) coordination compounds with benzoguanamine ligand: Syntheses, structures, thermal stability and photoluminescent properties

    NASA Astrophysics Data System (ADS)

    Hao, Hong-Jun; Sun, Di; Liu, Fu-Jing; Huang, Rong-Bin; Zheng, Lan-Sun

    2012-03-01

    Two mixed-ligand coordination complexes (CCs) of the formula [Ag2(bga)2(pnba)2(H2O)]·(bga)2 (1) and {[Ag3(bga)3(dnb)3(H2O)]·(CH3OH)·(C2H5OH)}n (2) (bga = benzoguanamine, Hpnba = 4-nitrobenzoic acid, Hdnb = 3,5-dinitrobenzoic acid) were synthesized by reactions of AgNO3 and bga in the presence of different carboxylates under the ammoniacal condition. Both CCs have been characterized by element analysis, powder X-ray diffraction (PXRD), IR and X-ray single-crystal diffraction. Complex 1 is 0D discrete molecule which is extended to 1D supramolecular chains through intermolecular N-H···N complementary hydrogen bonds. Complex 2 is a 1D infinite chain containing monodentate and bidentate bga ligands. Analogously, the presence of complementary N-H···N hydrogen bonds drives the 1D chains to form 2D supramolecular sheet. In addition, the thermal stabilities and the photoluminescence properties of them were also investigated.

  17. Photoluminescence properties of a new orange-red emitting Sm3+-doped Y2Mo4O15 phosphor

    NASA Astrophysics Data System (ADS)

    Deng, Huajuan; Zhao, Ze; Wang, Jing; Hei, Zhoufei; Li, Mengxue; Noh, Hyeon Mi; Jeong, Jung Hyun; Yu, Ruijin

    2015-08-01

    A series of novel Y2Mo4O15:xSm3+ ((0.01 ≤ x ≤ 0.20) phosphors for white light-emitting (W-LEDs) were successfully prepared by the solid state reaction technology at 973 K for 12 h. X-ray diffraction and photoluminescence spectra were utilized to characterize the structure and luminescence properties of the as-synthesized phosphors. The emission spectra of the Y2Mo4O15:Sm3+ phosphors consisted of some sharp emission peaks of Sm3+ ions centered at 565 nm, 605 nm, 650 nm, and 712 nm. The strongest one is located at 605 nm due to 4G5/2-6H7/2 transition of Sm3+, generating bright orange-red light. The optimum dopant concentration of Sm3+ ions in Y2Mo4O15:xSm3+ is around 5 mol% and the critical transfer distance of Sm3+ is calculated as 23.32 Å. The CIE chromaticity coordinates of the Y2Mo4O15:0.05Sm3+ phosphors were located in the orange reddish region. The Y2Mo4O15:Sm3+ phosphors may be potentially used as red phosphors for white light-emitting diodes.

  18. Positional isomerism-driven two 3D pillar-layered metal-organic frameworks: Syntheses, topological structures and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Sun, Yayong; Zhao, Siwei; Ma, Haoran; Han, Yi; Liu, Kang; Wang, Lei

    2016-06-01

    Two novel three-dimensional (3D) pillar-layered metal-organic frameworks (MOFs), namely [Zn2(μ2-OH)(boaba)(1,4-bmimb)]n (1) and {[Zn5K2(μ2-H2O)2(boaba)4(1,2-bmimb)2(H2O)2]·H2O}n (2), were prepared by hydrothermal reactions (H3boaba=3,5-bis-oxyacetate-benzoic acid; 1,4-bmimb=1,4-bis((2-methyl-1H-imidazol-1-yl)methyl)benzene; 1,2-bmimb =1,2-bis((2-methyl-1H-imidazol-1-yl)methyl)benzene). Notably, 1 exhibits a (3,5)-connected binodal (63)(69·8)-gra net with binuclear [Zn2(μ2-OH)(COO)]2+ clusters, while 2 shows a novel (4,4,5,9)-connected 4-nodal net constructed from the unique Zn(II)-K(I) heterometal rod-like substructures. The results indicate that the disposition of the 2-methylimidazolyl groups of bis(imidazole) ligands have a significant effect on structural diversity. Moreover, the photoluminescence properties of 1 and 2 have been investigated.

  19. Nanostructures of Sr2+ doped BiFeO3 multifunctional ceramics with tunable photoluminescence and magnetic properties.

    PubMed

    Mandal, S K; Rakshit, T; Ray, S K; Mishra, S K; Krishna, P S R; Chandra, Amreesh

    2013-02-01

    Careful tuning of formation (calcination) temperature of Sr(2+) doped BiFeO(3) multiferroic ceramics results in tailorable particle morphologies ranging from spherical to pillar-like. Based on the minimization of Gibb's free energy approach, the dominant homogeneous mechanism for particle growth is suggested. The chemical substitution of a trivalent ion (Bi(3+)) by a divalent ion (Sr(2+)) causes the transformation of certain fraction of Fe(3+) to Fe(4+) and/or the appearance of oxygen vacancies. This has been respectively proved by the analysis of XPS and refinement of neutron diffraction data. Although significant modification in the particle morphology is observed, the crystal unit cell remains rhombohedral with a R3c space group but interesting variations in physical properties are achieved. O-vacancies induced strong and sharp photoluminescence activity in the IR region, similar to ZnO, is reported for the first time. This observation opens up a new application for multiferroic ceramics. SQUID M-H data confirms the straightening of the canted spin structure of BiFeO(3), which in turn results in magnetism similar to ferromagnetic materials. Findings of the magneto-dielectric effect are also discussed to claim the multiferroic nature of the sample. PMID:23300169

  20. Nanostructures of Sr2+ doped BiFeO3 multifunctional ceramics with tunable photoluminescence and magnetic properties

    NASA Astrophysics Data System (ADS)

    Mandal, S. K.; Rakshit, T.; Ray, S. K.; Mishra, S. K.; Krishna, P. S. R.; Chandra, Amreesh

    2013-02-01

    Careful tuning of formation (calcination) temperature of Sr2+ doped BiFeO3 multiferroic ceramics results in tailorable particle morphologies ranging from spherical to pillar-like. Based on the minimization of Gibb’s free energy approach, the dominant homogeneous mechanism for particle growth is suggested. The chemical substitution of a trivalent ion (Bi3+) by a divalent ion (Sr2+) causes the transformation of certain fraction of Fe3+ to Fe4+ and/or the appearance of oxygen vacancies. This has been respectively proved by the analysis of XPS and refinement of neutron diffraction data. Although significant modification in the particle morphology is observed, the crystal unit cell remains rhombohedral with a R3c space group but interesting variations in physical properties are achieved. O-vacancies induced strong and sharp photoluminescence activity in the IR region, similar to ZnO, is reported for the first time. This observation opens up a new application for multiferroic ceramics. SQUID M-H data confirms the straightening of the canted spin structure of BiFeO3, which in turn results in magnetism similar to ferromagnetic materials. Findings of the magneto-dielectric effect are also discussed to claim the multiferroic nature of the sample.

  1. Chemical states and electronic properties of the interface between aluminium and a photoluminescent conjugated copolymer containing europium complex

    NASA Astrophysics Data System (ADS)

    Cai, Q. J.; Ling, Q. D.; Li, S.; Zhu, F. R.; Huang, Wei; Kang, E. T.; Neoh, K. G.

    2004-01-01

    The chemical states and electronic properties of the interface between thermally evaporated aluminium and a photoluminescent conjugated copolymer containing 9,9'-dihexylfluorene and europium complex-chelated benzoate units in the main chain (PF6-Eu(dbm) 2phen) were studied in situ by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The changes in C 1s, Eu 3d, N 1s, and Al 2p core-level lineshapes with progressive deposition of aluminium atoms were carefully monitored. Aluminium was found to interact with the conjugated backbone of the copolymer to form the Al carbide, Al-O-C complex, and Al(III)-N chelate at the interface. In addition, the europium ions were reduced to the metallic state by the deposited aluminium atoms, which were oxidized and chelated by the 1,10-phenanthroline ligands (phen). The changes in chemical states at the interface suggest that the intramolecular energy transfer process in this copolymer had been affected. Moreover, aluminium also interacted with the bulk-adsorbed oxygen, which migrates to the surface in response to the deposition of aluminium atoms, to form a layer of metal oxides. On the other hand, the evolution of the UPS spectra suggests that the π-states of the conjugated system were affected and an unfavorable dipole layer was induced by the deposited aluminium atoms.

  2. Photoluminescence and long persistent luminescence properties of a novel green emitting phosphor Sr3TaAl3Si2O14:Tb3+

    NASA Astrophysics Data System (ADS)

    Xue, Feihong; Hu, Yihua; Ju, Guifang; Chen, Li; He, Miao; Wang, Tao; Jin, Yahong; Zhang, Shaoan; Lin, Jun

    2016-06-01

    A series of green emitting persistent phosphors Sr3TaAl3Si2O14:Tb3+ were synthesized via a conventional solid-state reaction method. These phosphors show a green persistent luminescence dominated at ~542 nm at room temperature after irradiated by 254 nm ultraviolet light for minutes. X-ray diffraction, scanning micrograph images, photoluminescence spectra, decay curves, afterglow spectra and thermal luminescence were performed to investigate the physical properties of the persistent phosphors. The influence of Tb3+ concentrations on the photoluminescence and long persistent luminescence properties was studied. The optimal concentration of Tb3+ ions for the best afterglow characteristic was experimentally to be 0.5 mol%. A feasible model was proposed on the basis of experimental results to discuss mechanism of long afterglow in Sr3TaAl3Si2O14:Tb3+ in detail.

  3. Crystal Growth and Photoluminescence Properties of Truncated Cubic BaMgAl10O17:Eu2+ Phosphors for Three-Dimensional Plasma Display Panels.

    PubMed

    Liu, Bitao; Chen, Yuan; Peng, Lingling; Han, Tao; Yu, Hong; Tian, Liangliang; Tu, Mingjing

    2016-04-01

    Monodispersed, truncated cube BaMgAl10O17:Eu2+ phosphors were synthesized by the sol-gel process. Scanning electron microscope (SEM), photoluminescence spectrum, powder X-ray diffraction and decay curves were used to evaluate the truncated cubic BaMgAl10O17:Eu2+ phosphors. The crystal growth process and photoluminescence properties were discussed in detail. The results showed that this truncated cubic morphology can be achieved via a simple sinter process. These truncated cubic BaMgAl10O17:Eu2+ phosphors showed acceptable emission intensity and better thermal properties. This result indicates truncated cubic BaMgAl10O17:Eu2+ phosphors would meet the requirements of plasma display panels (PDPs). PMID:27451727

  4. Fabrication and optical properties of non-polar III-nitride air-gap distributed Bragg reflector microcavities

    SciTech Connect

    Tao, Renchun Kako, Satoshi; Arita, Munetaka; Arakawa, Yasuhiko

    2013-11-11

    Using the thermal decomposition technique, non-polar III-nitride air-gap distributed Bragg reflector (DBR) microcavities (MCs) with a single quantum well have been fabricated. Atomic force microscopy reveals a locally smooth DBR surface, and room-temperature micro-photoluminescence measurements show cavity modes. There are two modes per cavity due to optical birefringence in the non-polar MCs, and a systematic cavity mode shift with cavity thickness was also observed. Although the structures consist of only 3 periods (top) and 4 periods (bottom), a quality factor of 1600 (very close to the theoretical value of 2100) reveals the high quality of the air-gap DBR MCs.

  5. Correlations between mechanical and photoluminescence properties in Eu doped sodium bismuth titanate

    NASA Astrophysics Data System (ADS)

    Prusty, Rajesh K.; Kuruva, Praveena; Ramamurty, U.; Thomas, Tiju

    2013-11-01

    Nanoindentation technique is utilized to examine mechanical property variation in Eu doped Na0.5Bi0.5TiO3 (NBT). Doping levels of Eu in NBT is systematically varied. Dilute doping results in a linear reduction in both modulus and hardness. At higher concentrations, a recovery of the mechanical properties (to undoped NBT values) is observed. These experimental trends mirror variations in the optical emission intensities with Eu concentration. Observed trends are rationalized on the basis of a model, which hypothesizes phase segregation beyond a critical Eu doping level. Such segregation leads to the formation of pure NBT, nano-Eu saturated NBT, and nano-mixed Eu oxides in the microstructure. Pure NBT is optically inactive, while saturated Eu:NBT is a much better emitter when compared to europium oxide. Hence beyond the critical concentration, luminescence signal comes primarily from the saturated Eu:NBT phase. The model presented is supported by nanoindentation, and spectroscopic results.

  6. Low temperature synthesis, photoluminescence, magnetic properties of the transition metal doped wurtzite ZnS nanowires

    SciTech Connect

    Cao, Jian; Han, Donglai; Wang, Bingji; Fan, Lin; Fu, Hao; Wei, Maobin; Feng, Bo; Liu, Xiaoyan; Yang, Jinghai

    2013-04-15

    In this paper, we synthesized the transition metal ions (Mn, Cu, Fe) doped and co-doped ZnS nanowires (NWs) by a one-step hydrothermal method. The results showed that the solid solubility of the Fe{sup 2+} ions in the ZnS NWs was about two times larger than that of the Mn{sup 2+} or Cu{sup 2+} ions in the ZnS NWs. There was no phase transformation from hexagonal to cubic even in a large quantity transition metal ions introduced for all the samples. The Mn{sup 2+}/Cu{sup 2+}/Fe{sup 2+} related emission peaks can be observed in the Mn{sup 2+},Cu{sup 2+} and Fe{sup 2+} doped ZnS NWs. The ferromagnetic properties of the co-doped samples were investigated at room temperature. - graphical abstract: The stable wurtzite ZnS:TM{sup 2+} (TM=Mn, Cu, Fe) nanowires with room temperature ferromagnetism properties were obtained. The different elongation of unit cell caused by the different doped ions was observed. Highlights: ► The transition metal ions doped wurtzite ZnS nanowires were synthesized at 180 °C. ► There was no phase transformation from hexagonal to cubic even in a large quantity introduced for all the samples. ► The room temperature ferromagnetism properties of the co-doped nanowires were investigated.

  7. Tuning the band gap and magnetic properties of BN sheets impregnated with graphene flakes

    NASA Astrophysics Data System (ADS)

    Kan, M.; Zhou, J.; Wang, Q.; Sun, Q.; Jena, P.

    2011-11-01

    The BN sheet is a nonmagnetic wide-band-gap semiconductor. Using density functional theory, we show that these properties can be fundamentally altered by embedding graphene flakes. Not only do graphene flakes preserve the two-dimensional (2D) planar structure of the BN sheet, but by controlling their shape and size, unexpected electronic and magnetic properties also emerge. The electronic band structure can be tuned from a direct gap to an indirect gap, the energy gap can be further modulated by changing the bonding patterns, and both hole injecting or electron injecting can be achieved by tailoring the triangular embedding pattern. Furthermore, the Lieb theorem still holds, and the embedded triangular graphene flakes become ferromagnetic with full spin polarizations of the introduced electrons or holes, opening the door to their use as spin filters. The study sheds new light on hybrid single-atomic-layer engineering for unprecedented applications of 2D nanomaterials.

  8. Synthesis, structure and photoluminescence properties of amine-templated open-framework bismuth sulfates

    SciTech Connect

    Marri, Subba R.; Behera, J.N.

    2014-02-15

    Two organically-templated bismuth sulfates of the compositions, [C{sub 6}N{sub 2}H{sub 14}] [Bi(SO{sub 4}){sub 2}(NO{sub 3})], (1) and [C{sub 4}N{sub 2}H{sub 12}]{sub 4}[Bi{sub 4}(SO{sub 4}){sub 10}(H{sub 2}O){sub 4}], (2), with open architecture have been synthesized and their structures determined by single crystal X-ray diffraction. 1 has a corrugated layered structure with 8-membered aperture wherein the SO{sub 4} tetrahedra and the BiO{sub 8} polyhedra join together to form (4, 4) net sheets of the metal centers while 2 has a three-dimensional structure possessing 8- and 12-membered channels. Both the compounds show good fluorescence properties exhibiting blue luminescence. Time-resolved fluorescence behavior of 1 and 2 shows mean fluorescence life time of 0.9 and 1.0 ns, respectively. - Graphical abstract: Two open-framework bismuth sulfates with the layered and three-dimensional structures have been synthesized and characterized. Both the compounds show good fluorescence properties exhibiting blue luminescence. Display Omitted - Highlights: • Two organically-templated bismuth sulfates with open architecture have been synthesized and characterized. • One has a corrugated layered structure while the other one has a three-dimensional structure possessing channels. • They are novel in that open-framework three-dimensional main group metal sulfates are first to be reported. • They show good fluorescence properties exhibiting blue luminescence.

  9. Cobalt(II) complexes with bis(N-imidazolyl/benzimidazolyl) pyridazine: Structures, photoluminescent and photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Li, Jin-Ping; Fan, Jian-Zhong; Wang, Duo-Zhi

    2016-07-01

    Six new CoII complexes [Co(L1)4(OH)2] (1), {[Co(L1)(H2O)4]·2ClO4}∞ (2), {[Co(L1)(H2O)4]·SiF6}∞ (3), {[Co(L1)3]·2ClO4}∞ (4), [Co(L2)Cl2]∞ (5) and {[Co(L2)2]·SiF6}∞ (6) [L1=3,6-bis(N-imidazolyl) pyridazine, L2=3,6-bis (N-benzimidazolyl) pyridazine] have been synthesized and characterized by elemental analysis, IR spectra and single crystal X-ray diffraction. Complex 1 has a mononuclear structure, while complexes 2 and 3 have 1-D chain structures. Considering the CoII centers were linked by the L1 ligands, the 3-D framework of complex 4 can be rationalized to be a {4^12.6^3} 6-c topological net with the stoichiometry uninodal net. 5 reveals a coordination 1-D zigzag chain structure consisting of a neutral chain [Co(L2)Cl2]n with the CoII centers. Complex 6 has a rhombohedral grid with a (4, 4) topology. The TGA property, fluorescent property and photocatalytic activity of complexes 1-6 have been investigated and discussed.

  10. Photoluminescence in quantum-confined SnO2 nanocrystals: Evidence of free exciton decay

    NASA Astrophysics Data System (ADS)

    Lee, E. J. H.; Ribeiro, C.; Giraldi, T. R.; Longo, E.; Leite, E. R.; Varela, J. A.

    2004-03-01

    Nanocrystalline SnO2 quantum dots were synthesized at room temperature by hydrolysis reaction of SnCl2. The addition of tetrabutyl ammonium hydroxide and the use of hydrothermal treatment enabled one to obtain tin dioxide colloidal suspensions with mean particle radii ranging from 1.5 to 4.3 nm. The photoluminescent properties of the suspensions were studied. The particle size distribution was estimated by transmission electron microscopy. Assuming that the maximum intensity photon energy of the photoluminescence spectra is related to the band gap energy of the system, the size dependence of the band gap energies of the quantum-confined SnO2 particles was studied. This dependence was observed to agree very well with the weak confinement regime predicted by the effective mass model. This might be an indication that photoluminescence occurs as a result of a free exciton decay process.

  11. Properties of discharge in the narrow gap glass RPC

    NASA Astrophysics Data System (ADS)

    Semak, A.; Ammosov, V.; Gapienko, V.; Ivanilov, A.; Koreshev, V.; Kulemzin, A.; Sviridov, Yu; Zaets, V.; Gushin, E.; Somov, S.

    2000-12-01

    Properties of discharges in a 2 mm glass Resistive Plate Chamber were investigated using the light amplifier for optical pictures and the digital scope for waveforms of induced pick-up signals. Multiple discharges were observed for different tetrafluoroethane-based gas mixtures both in 'avalanche' and 'streamer' modes. Multiple discharges substantially increase the spatial size of the initial discharge caused by a through-going particle ionisation. Average spatial characteristics and typical optical pictures are presented. Space-time relationships for the streamer do not show any prominent dependence.

  12. Fabrication of ZnO photonic amorphous diamond nanostructure from parrot feathers for modulated photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengli; Yu, Ke; Liao, Na; Yin, Haihong; Lou, Lei; Yu, Qian; Liao, Yuanyuan; Zhu, Ziqiang

    2011-12-01

    A ZnO photonic amorphous diamond nanostructure was successfully synthesised using a feather barb of the Rosy-Faced Lovebird as supporting template via a facile sol-gel process. Different from ordered structures, an isotropic PBG around 500 nm was evidenced from reflectance spectra and an optical metallurgical microscopy image, which overlaps with the visible emission peak of ZnO. As a result, the inhibition of visible emission inside the PBG and the enhancement of UV emission at the PBG edges have both been observed, which is independent from the incident angle. Moreover, the rapid thermal annealing can also help improve the crystallinity of ZnO and raise the UV/visible emission ratio without affecting the structure. These results can be very useful for the study of the modification of the optical emission properties of ZnO and other semiconductor materials as well as research on ZnO random lasing.

  13. Fabrication and photoluminescence properties of Cr:YAG and Yb,Cr:YAG transparent ceramic

    NASA Astrophysics Data System (ADS)

    Chen, Xingtao; Lu, Tiecheng; Wei, Nian; Lu, Zhongwen; Chen, Lijia; Zhang, Qinghua; Cheng, Gang; Qi, Jianqi

    2015-11-01

    Cr:YAG and Yb/Cr:YAG transparent ceramics containing Ca as charge counter element were fabricated by vacuum sintering technique using the co-precipitation synthesis of raw powders. Their spectral and luminescence properties as well as the influence of Cr3+ concentration on the optical properties of Yb,Cr:YAG ceramic were investigated. Results show the transmittance of 10 at.% Yb, 0.25 at.% Cr:YAG and 0.25 at.% Cr:YAG reaches 83% at 1200 nm and 81% at 1400 nm, respectively. And the Yb,Cr:YAG ceramics exhibit a pore free structure with an average grain size of about 5 μm. After annealing, most of Cr3+ ions transform into Cr4+. In the case of excitation wavelength of 440 nm, a sharp emission peak of 694 nm appeared in the Yb,Cr:YAG ceramic before annealing and the band enhanced with the increase of the Cr3+ concentration, which is attributed to the 4T2g-4A2g fluorescence transition. The emission spectrums and fluorescence decays manifest that both the luminescent intensity and the lifetimes of Yb,Cr:YAG are lower than Yb:YAG ceramic and the lifetimes of Yb,Cr:YAG and Yb:YAG are 0.93 and 2.38 ms, respectively. This results demonstrate the existence of the ground state absorption of Cr4+ in the Yb,Cr:YAG ceramic. Experimental evidence proved that Yb,Cr:YAG transparent ceramics could be a potential material for passive self-Q-switched solid-state laser.

  14. Synthesis, crystal structure and photoluminescence property of Eu/Tb MOFs with mixed polycarboxylate ligands

    NASA Astrophysics Data System (ADS)

    Yang, Lu; Zhang, Sheng; Qu, Xiaoni; Yang, Qi; Liu, Xiangyu; Wei, Qing; Xie, Gang; Chen, Sanping

    2015-11-01

    Lanthanide MOFs, [Eu(TCA)(NDC)·H2O]n (1) and [Tb(TCA)(NDC)·H2O]n (2), have been prepared with the mixed aromatic carboxylate ligands, namely, 4,4‧,4″-tricarboxytriphenylamine (H3TCA) and 1,4-naphthalenedicarboxylate (H2NDC). Single-crystal X-ray diffraction analysis reveals that isomorphic 1 and 2 present pillar-layered 3D framework that Eu/Tb(III) bond with carboxylate in various coordination fashions. Optical investigation indicates that the as-prepared compounds feature characteristic luminescence emission bands of Eu/Tb ions in the visible regions at room temperature. Moreover, compound 2 shows a relatively longer luminescence lifetime (τ=0.342 ms) and significantly enhanced quantum yield (Φoverall=11%) comparing with those of 1 (τ=0.335 ms, Φoverall=0.06%). Two Ln-MOFs (Ln=EuIII, TbIII) with mixed polycarboxylate ligands present different luminescent properties.

  15. Photoluminescent properties of nanostructured Y 2O 3:Eu 3+ powders obtained through aerosol synthesis

    NASA Astrophysics Data System (ADS)

    Marinkovic, K.; Mancic, L.; Gomez, L. S.; Rabanal, M. E.; Dramicanin, M.; Milosevic, O.

    2010-10-01

    Red emitting Y 2O 3:Eu 3+ (5 and 10 at.%) submicronic particles were synthesized through ultrasonic spray pyrolysis method from the pure nitrate solutions at 900 °C. The employed synthesis conditions (gradual increase of temperature within triple zone reactor and extended residence time) assured formation of spherical, dense, non-agglomerated particles that are nanostructured (crystallite size ˜20 nm). The as-prepared powders were additionally thermally treated at temperatures up to 1200 °C. A bcc Ia-3 cubic phase presence and exceptional powder morphological features were maintained with heating and are followed with particle structural changes (crystallite growth up to 130 nm). Emission spectra were studied after excitation with 393 nm wavelength and together with the decay lifetimes for Eu 3+ ion 5D0 and 5D1 levels revealed the effect of powder nanocrystalline nature on its luminescent properties. The emission spectra showed typical Eu 3+5D0 → 7F i ( i = 0, 1, 2, 3, 4) transitions with dominant red emission at 611 nm, while the lifetime measurements revealed the quenching effect with the rise of dopant concentration and its more consistent distribution into host lattice due to the thermal treatment.

  16. [Temperature-Dependent Photoluminescence Property Studies of SiN(x) Films with nc-Si].

    PubMed

    Liu, Jian-ping; Zheng, Yan; Liu, Hai-xu; Yu, Wei; Ding, Wen-ge; Lai, Wei-dong

    2016-03-01

    Silicon nitride (SiN(x)) films containing nanocrystalline silicon (nc-Si) were deposited on crystalline silicon substrate by facing-target sputtering technique. Thermal annealing process was performed at 450 degrees C for 50 min in a conventional furnace under FG(10% H2, 90% N2) ambient. The photoluminescece (PL) properties of the SiN(x) films with nc-Si were investigated by steady/transient PL spectra measurements by Fluorescence spectrometer with different temperatures. The PL processes could be attributed to the quantum confinement effect of nc-Si and the defects in the film. The PL peak position exhibits a small blue shift with the increasing of the excitation energy, which indicates that the PL portion of the nc-Si increased with smaller size. In addition, the PL lifetime increases and the PL intensity exhibits exponential increase as a result of the decreased temperature which supressed the nonradiative recombination process and then improved the radiative recombination. The PL lifetime of the film significantly reduces with the decreasing of the detection wavelength, which indicates that the PL process related to the the quantum confinement effect strongly depends on temperature. PMID:27400499

  17. Comparison of photoluminescence properties of HSA-protected and BSA-protected Au25 nanoclusters

    NASA Astrophysics Data System (ADS)

    Tsukamoto, Masato; Kawasaki, Hideya; Saitoh, Tadashi; Inada, Mitsuru; Kansai Univ. Collaboration

    Gold nanoclusters (NCs) have attracted great interest for a wide range of applications. In particular, red light-emitting Au25 NCs have been prepared with various biological ligands. It has been shown that Au25 NCs have Au13-core/6Au2(SR)3-semiring structure. The red luminescence thought to be originated from both core (670 nm) and semiring (625 nm). It is important to reveal a structure of Au25 NCs to facilitate the progress of applications. However, the precise structure of Au25 NCs has not been clarified. There is a possibility of obtaining structural information about Au25 NCs to compare optical properties of the NCs that protected by slightly different molecules. Bovine and human serum albumin (BSA, HSA) are suitable one for this purpose. It has been suggested that rich tyrosine and cysteine residues in these molecules are important to produce the thiolate-protected Au NCs. If Au25 NCs have core/shell structure, only the luminescence of the semiring will be affected by the difference of the albumin molecules. We carefully compared PL characteristics of BSA- and HSA- protected Au25 NCs. As a result, there was no difference in the PL at 670 nm (core), while differences were observed in the PL at 625 nm (semiring). The results support that Au25 NCs have core/semiring structure.

  18. Ab-Initio Calculations of Electronic Properties of InP and GaP

    NASA Astrophysics Data System (ADS)

    Malozovsky, Y.; Franklin, L.; Ekuma, E. C.; Zhao, G. L.; Bagayoko, D.

    2013-06-01

    We present results from ab-initio, self-consistent local density approximation (LDA) calculations of electronic and related properties of zinc blende indium phosphide (InP) and gallium phosphide (GaP). We employed a LDA potential and implemented the linear combination of atomic orbitals (LCAO) formalism. This implementation followed the Bagayoko, Zhao and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF). This method searches for the optimal basis set that yields the minima of the occupied energies. This search entails increases of the size of the basis set and the related modifications of angular symmetry and of radial orbitals. Our calculated, direct band gap of 1.398 eV (1.40 eV), at the Γ point, is in excellent agreement with experimental values, for InP, and our preliminary result for the indirect gap of GaP is 2.135 eV, from the Γ to X high symmetry points. We have also calculated electron and hole effective masses for both InP and GaP. These calculated properties also agree with experimental findings. We conclude that the BZW-EF method could be employed in calculations of electronic properties of high-Tc superconducting materials to explain their complex properties.

  19. Photoluminescence properties of AlN-doped BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} phosphors

    SciTech Connect

    Wang, Yong; Tang, Jianfeng; Ouyang, Xicheng; Liu, Buqiong; Lin, Rong Han

    2013-06-01

    Highlights: ► Ideal hexagonal shape particle size in 5 μm and 2.5–3 μm in thickness are obtained. ► The growth mechanism is studied by a computer simulation. ► The influence of introduced AlN on the sites of Eu{sup 2+} and photoluminescence properties was investigated. - Abstract: The AlN-doped BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} phosphors were synthesized by conventional solid-state reaction. Powder X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence spectrum (PL) were used for characterization. The growth mechanism was carried out by computer simulation with CASTEP application, and revealed that an ideal hexagonal shape, particle size in 5 μm and 2.5–3 μm in thickness, could be obtained by AlN doping. Additionally, due to the low electronegativity of N{sup 3−}, the AlN-doped sample showed 35% increase in PL intensity and improvement of thermal stability. These fine particle size and better photoluminescence properties are expected to be applicable to industrial production of BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} phosphors.

  20. Annealing effect on the photoluminescence properties of ZnO nanorod array prepared by a PLD-assistant wet chemical method

    SciTech Connect

    Wei Sufeng; Lian Jianshe; Wu Hua

    2010-11-15

    Well-aligned ZnO nanorod arrays were synthesized by a wet chemical method on the glass substrate with ZnO thin film as seed layer prepared by pulsed laser deposition. The effect of annealing temperature on the luminescence characteristics was investigated. As the annealing temperature increased, the photoluminescence properties show a general enhancing tendency. The nanorod array with high ultraviolet emission and negligible visible light emission (designated by the photoluminescence intensity ratio of ultraviolet to visible emission of 66.4) is obtained by annealing the sample at 700 deg. C for 1 h. Based on the results of X-ray photoelectron spectroscopy and photoluminescence spectra, the mechanisms of visible emission were discussed. - Research Highlights: {yields} ZnO nanorod array with good crystallography, low defects concentration and good optical property was obtained after annealed at 700 deg. C for 1 h. {yields} The transition from the conduction band to the O{sub i} level may be responsible for the yellow-green emission. {yields} The yellow emission may originate from the presence of Zn(OH){sub 2} on the surface or the band transition from conduction band to V{sub o}Zn{sub i} level. {yields} The transition from the Zn{sub i} level to the level should produce an orange emission or an orange-red emission.

  1. Organic acids and protein compounds causing the photoluminescence properties of natural rubber membranes and the quenching phenomena from Au nanoparticle incorporation.

    PubMed

    Cabrera, Flávio C; Agostini, Deuber L S; Dos Santos, Renivaldo J; Guimarães, Francisco E G; Guerrero, Ariel R; Aroca, Ricardo F; Job, Aldo E

    2014-12-01

    Natural rubber membranes were fabricated using latex from Hevea brasiliensis trees (clone RRIM 600) by casting, and controlling the time and temperature of thermal treatment. Three temperatures were used: 65, 80 and 120 °C and the corresponding annealing times of 6, 8, 10 and 12 h. The centrifugation of the latex produces the constituent phases: solid rubber (F1), serum or protein components (F2) and bottom fraction (F3). The photoluminescence properties could be correlated with organic acid components of latex. Natural rubber membranes were used as the active substrate (reducing agent) for the incorporation of colloidal Au nanoparticles synthesized by in situ reduction at different times. The intensity of photoluminescence bands assigned to the natural rubber decreases with the increase in amount of nanoparticles present on the membrane surface. It can be assumed that Au nanoparticles may be formed by reduction of the Au cation reacting with functional groups that are directly related to photoluminescence properties. However, the quenching of fluorescence may be attributed to the formation of a large amount of metal nanostructures on the natural rubber surface. PMID:24760547

  2. Effect of doping of calcium fluoride nanoparticles on the photoluminescence properties of europium complexes with benzoic acid derivatives as secondary ligands and 2-aminopyridine as primary ligand

    NASA Astrophysics Data System (ADS)

    Sharma, Garima; Narula, Anudeep Kumar

    2015-08-01

    The present article reports the synthesis of three Eu(III) complexes [Eu(BA)3(2-ap)] (1), [Eu(HBA)3(2-ap)] (2) and [Eu(ABA)3(2-ap)] (3) (BA = benzoic acid, HBA = 2-hydroxy benzoic acid, ABA = 2-amino benzoic acid and 2-ap = 2-aminopyridine) carried out in ethanol solution. The complexes were further doped with CaF2 nanoparticles and a change in the photoluminescence properties was observed. The compositions and structural investigation of the complexes were determined by elemental analysis and Fourier transform infrared spectroscopy (FTIR) which suggest the coordination of ligands with the central Eu(III) ion. The optical properties of the complexes were studied by Ultraviolet Visible absorption spectroscopy (UV-Vis) and photoluminescence studies (PL). The relative PL intensity was enhanced in the Eu(III) complexes doped with CaF2 nanoparticles as compared to the pure Eu(III) complexes, however the increase in intensity varied in the order of ligands ABA > HBA > BA. The photoluminescence lifetime decay curves also revealed the longer lifetime (τ) and higher quantum efficiency (η) for europium complexes with ABA ligands suggesting the efficient energy transfer and better sensitizing ability of the ligand to europium ion. The morphology of the synthesized compounds were studied by Scanning Electron Microscopy (SEM) revealing spherical morphology with agglomeration of the nanoparticles.

  3. Synthesis and photoluminescence properties of LaPO4:Ce3+, Tb3+ nanophosphors by microwave-assisted co-precipitation method at low temperature

    NASA Astrophysics Data System (ADS)

    Dong, Wei-Li; Zhang, Xi-Yan; Shi, Hui; Mi, Xiao-Yun; Wang, Neng-Li; Han, Ke-Xuan

    2015-08-01

    Nanosized green phosphor LaPO4:Ce3+, Tb3+ has been synthesized by microwave-assisted co-precipitation method. The morphology, crystal structure and photoluminescence properties have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrophotometer. The lanthanum phosphate phosphors with monoclinic crystal structure and fine crystallinity and dispersibility were synthesized at 900°C for 1 h and the particle size of the phosphors is ˜ 100 nm. The strongest photoluminescence emission peak is located at 543 nm due to the (5D4→7F5) transition of Tb3+ ion. The experimental results indicate that nanosized green phosphor 40% Ce3+ and 20% Tb3+ doped LaPO4 synthesized by microwave-assisted co-precipitation method is a beneficial phosphor for high resolution display devices.

  4. Synthesis and photoluminescence properties of aligned Zn{sub 2}GeO{sub 4} coated ZnO nanorods and Ge doped ZnO nanocombs

    SciTech Connect

    Su Yong; Meng Xia Chen Yiqing; Li Sen; Zhou Qingtao; Liang Xuemei; Feng Yi

    2008-07-01

    Aligned Zn{sub 2}GeO{sub 4} coated ZnO nanorods and Ge doped ZnO nanocombs were synthesized on a silicon substrate by a simple thermal evaporation method. The structure and morphology of the as-synthesized nanostructure were characterized using scanning electron microscopy and transmission electron microscopy. The growth of aligned Zn{sub 2}GeO{sub 4} coated ZnO nanorods and Ge doped ZnO nanocombs follows a vapor-solid (VS) process. Photoluminescence properties were also investigated at room temperature. The photoluminescence spectrum reveals the nanostructures have a sharp ultraviolet luminescence peak centered at 382 nm and a broad green luminescence peak centered at about 494 nm.

  5. Synthesis, characterization, X-ray structure and photoluminescence properties of two Ce(III) complexes derived from pentadentate ligands

    NASA Astrophysics Data System (ADS)

    Köse, Muhammet; Akgün, Eyup; Ceyhan, Gökhan

    2015-12-01

    In this study, two new Ce(III) complexes [Ce(L1)(NO3)3]•H2O and [Ce(L2)(NO3)3]•H2O were synthesized and characterized by spectroscopic and analytical methods where L1 and L2 are pentadentate diimine ligands. Molecular structure of [Ce(L1)(NO3)3]•H2O was determined by single crystal X-ray diffraction study. The complex was found to crystallize as [Ce(L1)(NO3)3] H2O. In the complex, the ligand L1 coordinates to the Ce(III) ion with the N3O2 donor set and the Ce(III) ion sits within the cavity of acyclic ligand. The Ce(III) ion is 11-coordinated by three nitrogen atoms from the ligand and eight O atoms, six of which come from three nitrate ions, two from the ligand. In the structure of the complex, water molecules link molecules together to form a 3D hydrogen bond network. Thermal behavior of the Schiff base ligands and their Ce(III) complexes metal complexes were studied under nitrogen atmosphere in the temperature range of 20-800 °C. Thermal stability of the ligands increased upon complexation with Ce(III) ion. In the UV-Vis spectra of Ce(III) complexes, new absorption bands appeared at 340-450 nm and these new bands were attributed to metal-ligand (M-L) charge transitions. Photoluminescence properties of the ligands and their Ce(III) complexes were examined.

  6. Synthesis, structural characterization and photoluminescence properties of a novel La(III) complex

    NASA Astrophysics Data System (ADS)

    Köse, Muhammet; Ceyhan, Gökhan; Atcı, Emine; McKee, Vickie; Tümer, Mehmet

    2015-05-01

    In this study, a novel La(III) complex [La(H2L)2(NO3)3(MeOH)] of a Schiff base ligand was synthesized and characterized by spectroscopic and analytical methods. Single crystals of the complex suitable for X-ray diffraction study were obtained by slow diffusion of diethyl ether into a MeOH solution of the complex which was found to crystallise as [La(H2L)2(NO3)3(MeOH)]ṡ2MeOHṡH2O. The structure was solved in monoclinic crystal system, P21/n space group with unit cell parameters a = 10.5641(11), b = 12.6661(16), c = 16.0022(17) Å, α = 67.364(2), β = 83.794(2)°, γ = 70.541(2)°, V = 1862.9(4) Å3 and Z = 2 with R final value of 0.526. In the complex, the La(III) ion is ten-coordinated by O atoms, five of which come from three nitrate ions, four from the two Schiff base ligands and one from MeOH oxygen atom. The Schiff base ligands in the structure are in a zwitter ion form with the phenolic H transferred to the imine N atom. Thermal properties of the La(III) complex were examined by thermogravimetric analysis and the complex was found to be thermally stable up to 310 °C. The Schiff base ligand and its La(II) complex were screened for their in vitro antimicrobial activity against Bacillus megaterium, Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus (Gram positive bacteria), Klebsiella pneumonia, Escherichia coli, Enterobacter aerogenes, Pseudomonas aeruginosa (Gram negative bacteria), Candida albicans,Yarrowia lipolytica (fungus) and Saccharomyces cerevisiae (yeast). The complex shows more antimicrobial activity than the free ligand.

  7. Structural and optical properties of (In,Ga)As/GaP quantum dots and (GaAsPN/GaPN) diluted-nitride nanolayers coherently grown onto GaP and Si substrates for photonics and photovoltaics applications

    NASA Astrophysics Data System (ADS)

    Durand, O.; Robert, C.; Nguyen Thanh, T.; Almosni, S.; Quinci, T.; Kuyyalil, J.; Cornet, C.; Létoublon, A.; Levallois, C.; Jancu, J.-M.; Even, J.; Pédesseau, L.; Perrin, M.; Bertru, N.; Sakri, A.; Boudet, N.; Ponchet, A.; Rale, P.; Lombez, L.; Guillemoles, J.-F.; Marie, X.; Balocchi, A.; Turban, P.; Tricot, S.; Modreanu, Mircea; Loualiche, S.; Le Corre, A.

    2013-01-01

    Lattice-matched GaP-based nanostructures grown on silicon substrates is a highly rewarded route for coherent integration of photonics and high-efficiency photovoltaic devices onto silicon substrates. We report on the structural and optical properties of selected MBE-grown nanostructures on both GaP substrates and GaP/Si pseudo-substrates. As a first stumbling block, the GaP/Si interface growth has been optimised thanks to a complementary set of thorough structural analyses. Photoluminescence and time-resolved photoluminescence studies of self-assembled (In,Ga)As quantum dots grown on GaP substrate demonstrate a proximity of two different types of optical transitions interpreted as a competition between conduction band states in X and Γ valleys. Structural properties and optical studies of GaAsP(N)/GaP(N) quantum wells coherently grown on GaP substrates and GaP/Si pseudo substrates are reported. Our results are found to be suitable for light emission applications in the datacom segment. Then, possible routes are drawn for larger wavelengths applications, in order to address the chip-to-chip and within-a-chip optical interconnects and the optical telecom segments. Finally, results on GaAsPN/GaP heterostructures and diodes, suitable for PV applications are reported.

  8. Remarkable changes in the photoluminescent properties of Y2Ce2O7:Eu(3+) red phosphors through modification of the cerium oxidation states and oxygen vacancy ordering.

    PubMed

    Raj, Athira K V; Prabhakar Rao, P; Sreena, T S; Sameera, S; James, Vineetha; Renju, U A

    2014-11-21

    A new series of red phosphors based on Eu(3+)-doped yttrium cerate [Y1.9Ce2O7:0.1Eu(3+), Y2Ce1.9O7:0.1Eu(3+) and Y2Ce2-xO7:xEu(3+) (x = 0.05, 0.10, 0.15, 0.20, 0.25 and 0.50)] was prepared via a conventional solid-state method. The influence of the substitution of Eu(3+) at the aliovalent site on the photoluminescent properties was determined by powder X-ray diffraction, FT Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy with energy-dispersive spectroscopy, UV-visible absorption spectroscopy, photoluminescence spectroscopy and lifetime measurements. The substitution of Eu(3+) at the Ce(4+) site induces a structural transition from a defect fluorite to a C-type structure, which increases the oxygen vacancy ordering and the distortion of the Eu(3+) environment, and decreases the formation of Ce(3+) states. In contrast, phosphors with isovalent substitution at the Y(3+) site exhibit the biphasic nature of defect fluorite and a C-type structure, thereby increasing the number of Ce(3+) oxidation states. These modifications resulted in remarkable changes in the photoluminescent properties of Y2Ce1.9O7:0.1Eu(3+) red phosphors, with emission intensities 3.8 times greater than those of the Ce0.9O2:0.1Eu(3+) and Y1.9Ce2O7:0.1Eu(3+). The photoluminescent properties of Y2Ce2-xO7:xEu(3+) were studied at different Eu(3+) concentrations under excitation with blue light. These phosphors emit intense red light due to the (5)D0-(7)F2 transition under excitation at 466 nm and no concentration quenching is observed with up to 50 mol% Eu(3+). They show increased lifetimes in the range 0.62-0.72 ms at Eu(3+) concentrations. The cation ordering linked to the oxygen vacancy ordering led to the uniform distribution of Eu(3+) ions in the lattice, thus allowing higher doping concentrations without quenching and consequently increasing the lifetime of the (5)D0 states. Our results demonstrate that significant improvements in

  9. Photoluminescence properties of AgInS2-ZnS nanocrystals: the critical role of the surface

    NASA Astrophysics Data System (ADS)

    Chevallier, Théo; Le Blevennec, Gilles; Chandezon, Frédéric

    2016-03-01

    AgInS2-ZnS (ZAIS) nanocrystals are very good candidates for easily synthesized, highly efficient cadmium-free nano-phosphors. They can be employed for the development of next generation white-LED technologies, taking advantage of their nanometric size. This paper describes the combined use of time-resolved emission spectroscopy and photoluminescence quantum yield measurements to quantitatively compare the efficiency of each recombination pathway involved in the photoluminescence of ZAIS nanocrystals. This approach, applied to nanocrystals of different sizes, compositions and surface chemistry revealed the critical role of surface effects. Moreover, we developed a new type of surface passivation that increases the photoluminescence quantum yield of all nanocrystal compositions by 15 to 20%. This molecular surface passivation can be applied as a replacement or in addition to the already established ZnS shell passivation method.AgInS2-ZnS (ZAIS) nanocrystals are very good candidates for easily synthesized, highly efficient cadmium-free nano-phosphors. They can be employed for the development of next generation white-LED technologies, taking advantage of their nanometric size. This paper describes the combined use of time-resolved emission spectroscopy and photoluminescence quantum yield measurements to quantitatively compare the efficiency of each recombination pathway involved in the photoluminescence of ZAIS nanocrystals. This approach, applied to nanocrystals of different sizes, compositions and surface chemistry revealed the critical role of surface effects. Moreover, we developed a new type of surface passivation that increases the photoluminescence quantum yield of all nanocrystal compositions by 15 to 20%. This molecular surface passivation can be applied as a replacement or in addition to the already established ZnS shell passivation method. Electronic supplementary information (ESI) available. See DOI: 10.1039/C5NR07082A

  10. Photoluminescence and thermoluminescence properties of Sr{sub 3}Al{sub 2}O{sub 6}:Tb{sup 3+}

    SciTech Connect

    Page, Pallavi; Ghildiyal, Rahul; Murthy, K.V.R.

    2008-02-05

    Photoluminescence and thermoluminescence characteristics of the SrO-Al{sub 2}O{sub 3} system doped with terbium have been studied and reported here. The phosphor was synthesized by a reflux sol-gel technique. With a view to study the dosimetric properties, the effect of beta irradiation has been studied in detail; further, concentration quenching effects observed in the emission of various terbium doped phosphors have led to optimization of dopant content. A case is made to project the phosphor as an efficient green light emitting material with good dosimetric properties.