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Sample records for gap photoluminescence properties

  1. Band gap control and photoluminescence properties of Ba(Co2x Ti1-x )O3 thin films prepared by Sol-gel method

    NASA Astrophysics Data System (ADS)

    Srivastava, Anchal; Misra, Kamakhya Prakash

    2014-06-01

    This paper reports on the preparation, characterization and optical properties of transparent Ba(Co2x Ti1-x )O3 (0 ≤ x ≤ 0.06) thin films prepared by sol-gel method and deposited on fused quartz substrate by spin-coating technique. Their formation is confirmed by X-ray diffraction patterns, energy dispersive X-ray spectrometry and Fourier transformed infrared measurements. Hitherto unreported near-band-gap photoluminescence in ultraviolet, at 378 nm (3.28 eV), of exciton origin is observed which remains unaffected with change in excitation wavelength from 320 to 350 nm. A weak defect emission appears in green region. For larger excitation wavelength, i.e., 488 nm, emission arising from localized states again occurs in green region but with lower energy. The occurrence of efficient violet-blue PL emission is related to `direct' band gap and shallow levels with high optical band gap values. Analysis of band gap variation with dopant concentration, determined using Tauc's plot assuming them both of `direct' and `indirect' nature, also indicates the `direct' nature. Co+2 ions as dopants promote a decrease of band gap of films linearly. Scanning electron micrographs show the granular and flakes-like surface growth. Atomic force microscopy images show the presence of ribbon-like nanostructured grains throughout the surface of the films which is smooth with small values of surface roughness.

  2. Highly aqueous soluble CaF2:Ce/Tb nanocrystals: effect of surface functionalization on structural, optical band gap, and photoluminescence properties.

    PubMed

    Ansari, Anees A; Parchur, Abdul K; Kumar, Brijesh; Rai, S B

    2016-12-01

    The design of nanostructured materials with highly stable water-dispersion and luminescence efficiency is an important concern in nanotechnology and nanomedicine. In this paper, we described the synthesis and distinct surface modification on the morphological structure and optical (optical absorption, band gap energy, excitation, emission, decay time, etc.) properties of highly crystalline water-dispersible CaF2:Ce/Tb nanocrystals (core-nanocrystals). The epitaxial growth of inert CaF2 and silica shell, respectively, on their surface forming as CaF2:Ce/Tb@CaF2 (core/shell) and CaF2:Ce/Tb@CaF2@SiO2 (core/shell/SiO2) nanoarchitecture. X-ray diffraction and transmission electron microscope image shows that the nanocrystals were in irregular spherical phase, highly crystalline (~20 nm) with narrow size distribution. The core/shell nanocrystals confirm that the surface coating is responsible in the change of symmetrical nanostructure, which was determined from the band gap energy and luminescent properties. It was found that an inert inorganic shell formation effectively enhances the luminescence efficiency and silica shell makes the nanocrystals highly water-dispersible. In addition, Ce(3+)/Tb(3+)-co-doped CaF2 nanocrystals show efficient energy transfer from Ce(3+) to Tb(3+) ion and strong green luminescence of Tb(3+) ion at 541 nm((5)D4→(7)F5). Luminescence decay curves of core and core/shell nanocrystals were fitted using mono and biexponential equations, and R (2) regression coefficient criteria were used to discriminate the goodness of the fitted model. The lifetime values for the core/shell nanocrystals are higher than core-nanocrystals. Considering the high stable water-dispersion and intensive luminescence emission in the visible region, these luminescent core/shell nanocrystals could be potential candidates for luminescent bio-imaging, optical bio-probe, displays, staining, and multianalyte optical sensing. A newly designed CaF2:Ce/Tb nanoparticles via

  3. 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.

  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. 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.

  6. 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.

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

    SciTech Connect

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

    2015-12-21

    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. (Figure Presented).

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

    DOE PAGES

    Sutter-Fella, Carolin M.; Li, Yanbo; Amani, Matin; ...

    2015-12-21

    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 luminescencemore » 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. (Figure Presented).« less

  10. Photoluminescence properties of silica aerogel/porous silicon nanocomposites

    NASA Astrophysics Data System (ADS)

    Karlash, A. Yu; Zakharko, Yu E.; Skryshevsky, V. A.; Tsiganova, A. I.; Kuznetsov, G. V.

    2010-08-01

    The luminescent properties of nanocomposite pellets based on silica aerogel and porous Si powder are studied depending on the ratio of chemical compounds. The photoluminescence of nanocomposites is characterized by a red-orange band related to silicon nanoparticles and a blue-green band related to silica aerogel with close values of decay time and activation energy. Remarkable tuning of nanocomposites' photoluminescence spectra in the RGB region is established allowing their use as promising phosphor materials for light-emitting diodes. The outgoing spectra of pellet photoluminescence are guided by the chemical composition ratio, porous Si and silica aerogel technology, and the storage time in ambient atmosphere. It was shown that using the silica aerogel as a dielectric matrix considerably increases the stability of photoluminescence yield of silicon nanoparticles.

  11. Optical properties in complex-structured nanometric quantum wells: Photoluminescence, photoluminescence excitation, and Stokes shift

    NASA Astrophysics Data System (ADS)

    Silva, A. A. P.; Vasconcellos, Áurea. R.; Luzzi, Roberto; Meneses, E. A.; Laureto, E.

    2009-10-01

    Systems in which one or more directions are in the nanometric space scale exhibit significantly some peculiar phenomena and processes. We consider here the case of nanometric quantum wells with complex structure, displaying fractal-like characteristics, which are part of semiconductor heterostructures. An extensive theoretical study of the optical properties of photoluminescence and excited photoluminescence, and then involving absorption and the question of emergence of the so-called Stokes shift that is observed in some cases are performed. The results are compared with some experimental data. This is of relevance for opening up the possibility to use optical measurements to perform a (nondestructive) quality control of samples grown under different methods and protocols.

  12. The excitonic photoluminescence mechanism and lasing action in band-gap-tunable CdS1-xSex nanostructures

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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.

  13. Photoluminescence properties of polystyrene-hosted fluorophore thin films

    NASA Astrophysics Data System (ADS)

    Chakraborty, Subha; Harris, Katherine; Huang, Mengbing

    2016-12-01

    We report on a photo-luminescence study of four different fluorophores: Coumarin 6, 2,5-Diphenyloxazole (PPO), 1,4-Bis(5-phenyl-2-oxazolyl)benzene (POPOP) and Para-terpehnyl (PTP), doped in a polystyrene-based thin film. All of the samples are prepared by spin coating from a non-polar polymer solution at various concentrations. Their emission spectra and transient properties are characterized by photoluminescence measurements. Red-shifts in the emission spectra are observed for all four types of fluorophores as their concentration increases. We explain this phenomenon based on concentration dependence of solvatochromic effects and the results show good agreement with existing literature. We also show that the singlet-singlet annihilation processes are possibly a prevalent mechanism in the high concentration regime that affects the steady state and transient emission characteristics of the fluors. With the exception of PTP, photoluminescence quenching occurs as the fluorophore concentration in the polymer is increased. Rate equations for excited state decay mechanisms are analysed by considering different radiative and non-radiative energy transfer mechanisms. The results show consistency with our experimental observations. PTP shows the best photoluminescence results as an efficient fluor in the thin film, whereas PPO shows the strongest concentration dependent quenching and an anomalous lifetime distribution.

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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.

  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. Temperature dependence of the band gap of zinc nitride observed in photoluminescence measurements

    NASA Astrophysics Data System (ADS)

    Trapalis, A.; Farrer, I.; Kennedy, K.; Kean, A.; Sharman, J.; Heffernan, J.

    2017-09-01

    We report the photoluminescence properties of DC sputtered zinc nitride thin films in the temperature range of 3.7-300 K. Zinc nitride samples grown at 150 °C exhibited a narrow photoluminescence band at 1.38 eV and a broad band at 0.90 eV, which were attributed to the recombination of free carriers with a bound state and deep-level defect states, respectively. The high-energy band followed the Varshni equation with temperature and became saturated at high excitation powers. These results indicate that the high-energy band originates from shallow defect states in a narrow bandgap. Furthermore, a red-shift of the observed features with increasing excitation power suggested the presence of inhomogeneities within the samples.

  19. 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.

  20. Tunable band gap photoluminescence from atomically thin transition-metal dichalcogenide alloys.

    PubMed

    Chen, Yanfeng; Xi, Jinyang; Dumcenco, Dumitru O; Liu, Zheng; Suenaga, Kazu; Wang, Dong; Shuai, Zhigang; Huang, Ying-Sheng; Xie, Liming

    2013-05-28

    Band gap engineering of atomically thin two-dimensional (2D) materials is the key to their applications in nanoelectronics, optoelectronics, and photonics. Here, for the first time, we demonstrate that in the 2D system, by alloying two materials with different band gaps (MoS2 and WS2), tunable band gap can be obtained in the 2D alloys (Mo(1-x)W(x)S(2) monolayers, x = 0-1). Atomic-resolution scanning transmission electron microscopy has revealed random arrangement of Mo and W atoms in the Mo(1-x)W(x)S(2) monolayer alloys. Photoluminescence characterization has shown tunable band gap emission continuously tuned from 1.82 eV (reached at x = 0.20) to 1.99 eV (reached at x = 1). Further, density functional theory calculations have been carried out to understand the composition-dependent electronic structures of Mo(1-x)W(x)S(2) monolayer alloys.

  1. Revealing the Origin and History of Lead-White Pigments by Their Photoluminescence Properties.

    PubMed

    Gonzalez, Victor; Gourier, Didier; Calligaro, Thomas; Toussaint, Kathleen; Wallez, Gilles; Menu, Michel

    2017-03-07

    The lead white pigment, composed of two main mineral phases cerussite PbCO3 and hydrocerussite 2PbCO3·Pb(OH)2, has been used in paintings since the Antiquity. The study of historical sources revealed that a large variety of lead white qualities were proposed, depending on the degree of sophistication of the pigment synthesis. Investigation of photoluminescence of the two constitutive mineral phases gave insight into the origin of the visible emission of these materials and emphasized the influence of structural defects on their photoluminescence properties. These effects were observed by combining emission and excitation spectra in two-dimensional representations. For each excitation wavelength, between 250 and 400 nm (4.9-3.1 eV), luminescence spectra were collected between 400 and 800 nm (3.1-1.5 eV). Two types of emission-excitation bands were identified: an emission excited in the optical bandgap of the compounds (about 5 eV), which depends on the constitutive phase (2.8 eV in cerussite and 2.1 eV in hydrocerussite), and broad emission bands in the same energy range excited below the optical gap, which are sensitive to the synthesis method and the nature of postsynthesis treatments. It is proposed that this sensitivity of photoluminescence properties of lead-white pigments could be used as fingerprints of their origin and history.

  2. Synthesis and photoluminescence properties of ZnO nanohelices

    NASA Astrophysics Data System (ADS)

    Zhou, M. Y.; Qu, L. S.; Gao, H.

    2017-06-01

    Sb-doped zinc oxide nanohelices were synthesized on silicon substrates by chemical vapor deposition. The morphologies and structures of the samples have been investigated by XRD, SEM, and HR-TEM. The ZnO nanohelices have a single crystallinewurtzite structure. Its length is up to tens of micrometres as a whole. It grows in the direction of (0001). There are six sticks in each period of the helices, which grow al-ong six directions of the equivalent ≤ft< {0\\bar 111} \\right> . In addition, its growth mechanism is discussed. Optical properties of the nanohelices were demonstrated by Photo-luminescence (PL) spectra.

  3. Leucas aspera mediated multifunctional CeO2 nanoparticles: Structural, photoluminescent, photocatalytic and antibacterial properties.

    PubMed

    Malleshappa, J; Nagabhushana, H; Sharma, S C; Vidya, Y S; Anantharaju, K S; Prashantha, S C; Daruka Prasad, B; Raja Naika, H; Lingaraju, K; Surendra, B S

    2015-01-01

    Spherical shaped cerium dioxide (CeO2) nanoparticles (NPs) were synthesized via bio mediated route using Leucas aspera (LA) leaf extract. The NPs were characterized by PXRD, SEM, UV-Visible techniques. Photoluminescence (PL), photocatalysis and antibacterial properties of NPs were studied. PXRD patterns and Rietveld analysis confirm cubic fluorite structure with space group Fm-3m. SEM results evident that morphology of the NPs was greatly influenced by the concentration of LA leaf extract in the reaction mixture. The band gap energy of the NPs was found to be in the range of 2.98-3.4 eV. The photocatalytic activity of NPs was evaluated by decolorization of Rhodamine-B (RhB) under UVA and Sun light irradiation. CeO2 NPs show intense blue emission with CIE coordinates (0.14, 0.22) and average color coordinated temperature value ∼148,953 K. Therefore the present NPs quite useful for cool LEDs. The superior photocatalytic activity was observed for CeO2 NPs with 20 ml LA under both UVA and Sunlight irradiation. The enhanced photocatalytic activity and photoluminescent properties were attributed to defect induced band gap engineered CeO2 NPs. Further, CeO2 with 20 ml LA exhibit significant antibacterial activity against Escherichia coli (EC) and Staphylococcus aureus (SA). These findings show great promise of CeO2 NPs as multifunctional material for various applications.

  4. 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.

  5. Photoluminescence properties of TiO2 nanofibers

    NASA Astrophysics Data System (ADS)

    Chetibi, Loubna; Busko, Tetiana; Kulish, Nikolay Polikarpovich; Hamana, Djamel; Chaieb, Sahraoui; Achour, Slimane

    2017-04-01

    Multi-walled carbon nanotube (MWCNT)-TiO2 nanofiber (NF) composites forming a layered nanostructure (MWCNTs/TiO2 NFs/Ti) were prepared by impregnation at low temperature. Room temperature photoluminescence (PL) of these nanostructures shows a broad intense band in the visible light range (˜450-600 nm). The origin of the PL emission which, mainly, resulted from surface oxygen vacancies and other defects was investigated. We studied the effect of MWCNT deposition on the PL of TiO2 NFs where the MWCNTs can act as an electron reservoir of electrons emitted from TiO2 nanofibers when irradiated with UV light. The combination of MWCNTs and TiO2 results in quenching of TiO2 luminescence in the visible range. In addition, the prepared surface of MWCNTs-TiO2 was irradiated with Ti+ ions using irradiation energy of 140 keV and doses of 1013 ions/cm2. Also, this treatment induced the PL intensity quenching due to the generation of non-radiative additional levels inside the band gap.

  6. Photoluminescence Investigation of the Indirect Band Gap and Shallow Impurities in Icosahedral B12As2

    DTIC Science & Technology

    2012-07-05

    could be effectively modulated by Si doping, resulting in p-type con- duction with a 105 reduction in the resistivity. Hall effect measurements on...conductivity has not been reported in IBA. Other studies of IBA have focused on thermal properties ( Seebeck coefficient, thermal conductivity16...2.56 eV), leading to a band gap of 3.2 eV. This band structure calculation also provided the first determination of the electron and hole effective

  7. EPR, thermo and photoluminescence properties of ZnO nanopowders.

    PubMed

    Jagannatha Reddy, A; Kokila, M K; Nagabhushana, H; Rao, J L; Shivakumara, C; Nagabhushana, B M; Chakradhar, R P S

    2011-10-15

    Nanocrystalline ZnO powders have been synthesized by a low temperature solution combustion method. The photoluminescence (PL) spectrum of as-formed and heat treated ZnO shows strong violet (402, 421, 437, 485 nm) and weak green (520 nm) emission peaks respectively. The PL intensities of defect related emission bands decrease with calcinations temperature indicating the decrease of Zn(i) and V(o)(+) caused by the chemisorptions of oxygen. The results are correlated with the electron paramagnetic resonance (EPR) studies. Thermoluminescence (TL) glow curves of gamma irradiated ZnO nanoparticles exhibit a single broad glow peak at ∼343°C. This can be attributed to the recombination of charge carriers released from the surface states associated with oxygen defects, mainly interstitial oxygen ion centers. The trapping parameters of ZnO irradiated with various γ-doses are calculated using peak shape method. It is observed that the glow peak intensity increases with increase of gamma dose without changing glow curve shape. These two characteristic properties such as TL intensity increases with gamma dose and simple glow curve structure is an indication that the synthesized ZnO nanoparticles might be used as good TL dosimeter for high temperature application.

  8. EPR, thermo and photoluminescence properties of ZnO nanopowders

    NASA Astrophysics Data System (ADS)

    Jagannatha Reddy, A.; Kokila, M. K.; Nagabhushana, H.; Rao, J. L.; Shivakumara, C.; Nagabhushana, B. M.; Chakradhar, R. P. S.

    2011-10-01

    Nanocrystalline ZnO powders have been synthesized by a low temperature solution combustion method. The photoluminescence (PL) spectrum of as-formed and heat treated ZnO shows strong violet (402, 421, 437, 485 nm) and weak green (520 nm) emission peaks respectively. The PL intensities of defect related emission bands decrease with calcinations temperature indicating the decrease of Zn i and V o+ caused by the chemisorptions of oxygen. The results are correlated with the electron paramagnetic resonance (EPR) studies. Thermoluminescence (TL) glow curves of gamma irradiated ZnO nanoparticles exhibit a single broad glow peak at ˜343 °C. This can be attributed to the recombination of charge carriers released from the surface states associated with oxygen defects, mainly interstitial oxygen ion centers. The trapping parameters of ZnO irradiated with various γ-doses are calculated using peak shape method. It is observed that the glow peak intensity increases with increase of gamma dose without changing glow curve shape. These two characteristic properties such as TL intensity increases with gamma dose and simple glow curve structure is an indication that the synthesized ZnO nanoparticles might be used as good TL dosimeter for high temperature application.

  9. Synthesis and Photoluminescence Properties of Porous Silicon Nanowire Arrays.

    PubMed

    Lin, Linhan; Guo, Siping; Sun, Xianzhong; Feng, Jiayou; Wang, Yan

    2010-08-05

    Herein, we prepare vertical and single crystalline porous silicon nanowires (SiNWs) via a two-step metal-assisted electroless etching method. The porosity of the nanowires is restricted by etchant concentration, etching time and doping lever of the silicon wafer. The diffusion of silver ions could lead to the nucleation of silver nanoparticles on the nanowires and open new etching ways. Like porous silicon (PS), these porous nanowires also show excellent photoluminescence (PL) properties. The PL intensity increases with porosity, with an enhancement of about 100 times observed in our condition experiments. A "red-shift" of the PL peak is also found. Further studies prove that the PL spectrum should be decomposed into two elementary PL bands. The peak at 850 nm is the emission of the localized excitation in the nanoporous structure, while the 750-nm peak should be attributed to the surface-oxidized nanostructure. It could be confirmed from the Fourier transform infrared spectroscopy analyses. These porous SiNW arrays may be useful as the nanoscale optoelectronic devices.

  10. 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.

  11. Structural evolution, growth mechanism and photoluminescence properties of CuWO4 nanocrystals.

    PubMed

    Souza, E L S; Sczancoski, J C; Nogueira, I C; Almeida, M A P; Orlandi, M O; Li, M S; Luz, R A S; Filho, M G R; Longo, E; Cavalcante, L S

    2017-09-01

    Copper tungstate (CuWO4) crystals were synthesized by the sonochemistry (SC) method, and then, heat treated in a conventional furnace at different temperatures for 1h. The structural evolution, growth mechanism and photoluminescence (PL) properties of these crystals were thoroughly investigated. X-ray diffraction patterns, micro-Raman spectra and Fourier transformed infrared spectra indicated that crystals heat treated and 100°C and 200°C have water molecules in their lattice (copper tungstate dihydrate (CuWO4·2H2O) with monoclinic structure), when the crystals are calcinated at 300°C have the presence of two phase (CuWO4·2H2O and CuWO4), while the others heat treated at 400°C and 500°C have a single CuWO4 triclinic structure. Field emission scanning electron microscopy revealed a change in the morphological features of these crystals with the increase of the heat treatment temperature. Transmission electron microscopy (TEM), high resolution-TEM images and selected area electron diffraction were employed to examine the shape, size and structure of these crystals. Ultraviolet-Visible spectra evidenced a decrease of band gap values with the increase of the temperature, which were correlated with the reduction of intermediary energy levels within the band gap. The intense photoluminescence (PL) emission was detected for the sample heat treat at 300°C for 1h, which have a mixture of CuWO4·2H2O and CuWO4 phases. Therefore, there is a synergic effect between the intermediary energy levels arising from these two phases during the electronic transitions responsible for PL emissions. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. 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.

  13. Specific features of photoluminescence properties of copper-doped cadmium selenide quantum dots

    SciTech Connect

    Tselikov, G. I.; Dorofeev, S. G.; Tananaev, P. N.; Timoshenko, V. Yu.

    2011-09-15

    The effect of doping with copper on the photoluminescence properties of cadmium selenide quantum dots 4 nm in dimension is studied. The quenching of the excitonic photoluminescence band related to the quantum dots and the appearance of an impurity photoluminescence band in the near-infrared region are observed after doping of the quantum dots with copper. It is established that, on doping of the quantum dots, the photoluminescence kinetics undergoes substantial changes. The photoluminescence kinetics of the undoped quantum dots is adequately described by a sum of exponential relaxation relations, whereas the photoluminescence kinetics experimentally observed in the region of the impurity band of the copper-doped samples follows stretched exponential decay, with the average lifetimes 0.3-0.6 {mu}s at the photon energies in the range of 1.47-1.82 eV. The experimentally observed changes in the photoluminescence properties are attributed to transformation of radiative centers in the quantum dots when doped with copper atoms.

  14. 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.

  15. Properties of Zn-doped GaN. I - Photoluminescence

    NASA Technical Reports Server (NTRS)

    Pankove, J. I.; Berkeyheiser, J. E.; Miller, E. A.

    1974-01-01

    It is shown that zinc in gallium nitride forms an efficient radiative center emitting blue light at 2.86 plus or minus 0.02 eV and acts as a deep acceptor that can render the crystal insulating. A systematic variation of growth conditions indicates that an optimization of the photoluminescence efficiency is possible. Under nonoptimal conditions lower photon energy emission is obtained.

  16. Properties of Zn-doped GaN. I - Photoluminescence

    NASA Technical Reports Server (NTRS)

    Pankove, J. I.; Berkeyheiser, J. E.; Miller, E. A.

    1974-01-01

    It is shown that zinc in gallium nitride forms an efficient radiative center emitting blue light at 2.86 plus or minus 0.02 eV and acts as a deep acceptor that can render the crystal insulating. A systematic variation of growth conditions indicates that an optimization of the photoluminescence efficiency is possible. Under nonoptimal conditions lower photon energy emission is obtained.

  17. Recovery properties of vacuum spark gaps

    SciTech Connect

    Sampayan, S.E. ); Gurbaxani, S.H. . Dept. of Electrical Engineering); Buttram, M.T. . Pulsed Power Systems Dept.)

    1989-12-01

    Multi-kilohertz vacuum spark gap switching utilizing diffuse discharge and counter-pulse techniques has recently been demonstrated. In addition, commercial, high coulomb vacuum interrupter switches have shown free recovery rates greater than 10 kV / {mu}s. Thus, vacuum spark gap switches may provide an alternative method of high average power switching. The authors have investigated the recovery properties of a 90 kV, 15 kA multiple site, triggered vacuum spark gap. Triggering was accomplished with a multisite surface flashover plasma source with approximately 60 sites distributed over a 10 cm/sup 2/ area. Gap dimensions were 1-cm spacing by 7.5-cm diam. Recovery measurements are presented and discussed.

  18. Photoluminescence properties of polynaphthalisoimides and polynapththalimides in solutions and thin layers

    NASA Astrophysics Data System (ADS)

    Wanic, Andrzej; Mazurak, Zbigniew; Cisowski, Jan

    2011-09-01

    A series of polynaphthalsoimides and polynaphthalimides from 1,4,5,8-naphthalene dianhydride and 4,4'-methylene-bis(2,6-diisopropylaniline) or its hydrochloride in HMPA were synthesized in one-step high temperature polycondensation process. The different temperatures of the reaction from 125°C to 180°C were applied. The products were investigated using PL techniques in both solutions and thin layers. The observed changes in all investigated spectra and photochemical properties were presented. The remarkable changes in emission wavelength in photoluminescence was observed together with the increase of the reaction temperature. This work presents novel approach to the class of polymers well known to literature worldwide trying to explain of some surprising aspects of photoluminescence of these compounds. When investigated in solution, the polymer synthesized at 125°C exhibit almost no photoluminescence. The increase of the temperature to 150°C causes the strong increase in the photoluminescence intensity at 545 nm. When the reaction temperature increase to 180°C the intensity of photoluminescence exhibits moderate increase at 546.5 nm, however, remarkable increase was observed for 476.5 nm and 440 nm. The photoluminescence analysis of the polymers synthesized shows that depending on reaction temperature products emitting at different wavelengths may be obtained. Investigations were repeated for thin layers of the polymers. The obtained results and their comparison with the results in solution were also presented and discussed.

  19. Photoluminescence properties of polynaphthalisoimides and polynapththalimides in solutions and thin layers

    NASA Astrophysics Data System (ADS)

    Wanic, Andrzej; Mazurak, Zbigniew; Cisowski, Jan

    2012-02-01

    A series of polynaphthalsoimides and polynaphthalimides from 1,4,5,8-naphthalene dianhydride and 4,4'-methylene-bis(2,6-diisopropylaniline) or its hydrochloride in HMPA were synthesized in one-step high temperature polycondensation process. The different temperatures of the reaction from 125°C to 180°C were applied. The products were investigated using PL techniques in both solutions and thin layers. The observed changes in all investigated spectra and photochemical properties were presented. The remarkable changes in emission wavelength in photoluminescence was observed together with the increase of the reaction temperature. This work presents novel approach to the class of polymers well known to literature worldwide trying to explain of some surprising aspects of photoluminescence of these compounds. When investigated in solution, the polymer synthesized at 125°C exhibit almost no photoluminescence. The increase of the temperature to 150°C causes the strong increase in the photoluminescence intensity at 545 nm. When the reaction temperature increase to 180°C the intensity of photoluminescence exhibits moderate increase at 546.5 nm, however, remarkable increase was observed for 476.5 nm and 440 nm. The photoluminescence analysis of the polymers synthesized shows that depending on reaction temperature products emitting at different wavelengths may be obtained. Investigations were repeated for thin layers of the polymers. The obtained results and their comparison with the results in solution were also presented and discussed.

  20. Hydrothermal synthesis, photoluminescence and photocatalytic properties of two silver(I) complexes

    NASA Astrophysics Data System (ADS)

    Yang, Yuan-Yuan; Zhou, Lin-Xia; Zheng, Yue-Qing; Zhu, Hong-Lin; Li, Wen-Ying

    2017-09-01

    Two new dinuclear silver(I) coordination complexes [Ag(Hntph)(tpyz)2/2]n1 and [Ag2(dtrz)2(Hntph)2] 2 (H2ntph=2-nitroterephthalic acid, tpyz=2,3,5-trimethylpyrazine, dtrz=3,5-dimethyl-4H-1,2,4-triazol-4-amine) have been obtained by hydrothermal reactions of Ag(I) salts with H2ntph and various N-donor ligands. Complex 1 exhibits a 2D layer structure constructed by the binuclear Ag2(Hntph)2 units and tpyz ligands. Complex 2 also shows a different binuclear unit Ag2(dtrz)2, which was assembled via hydrogen bonds interactions to a 3D supramolecular architecture. The photocatalytic experiments showed that complex 2 is an excellent visible light candidate for degradation of RhB, and the degradation ratio of RhB reached 91.4% after 7 h under the light of 90 W white LED lamp. Moreover, the photoluminescent properties and the optical band gaps of 1-2 have also been investigated.

  1. CdSe nanocrystals ingrained dielectric nanocomposites: synthesis and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Dey, Chirantan; Goswami, Madhumita; Karmakar, Basudeb

    2015-01-01

    Cadmium selenide (CdSe) nanocrystals ingrained dielectric nanocomposites in a B2O3-SiO2-Al2O3-Na2O-K2O borosilicate glass system were synthesized by a single step in situ melt quenching technique. The sizes of the nanocrystals as well as the band gap of the nanocomposites were controlled by both concentration of CdSe and post thermal treatment duration. The nanocomposites were characterized by different instrumental techniques including detailed photoluminescence studies. The sizes of the CdSe nanocrystals were found to alter in the range 4-16 nm as estimated from the effective mass approximation model and optical absorption spectroscopy. However, the TEM analysis revealed the generation of two different size ranges, 3-4 and 23-45 nm, of the particles within the dielectric matrix. Selected area diffraction (SAED) and x-ray diffraction (XRD) patterns authenticate the formation of hexagonal nanostructures of CdSe. These nanocomposites were found to be capable of exhibiting strong visible red luminescence around 715 nm on excitation at 446 nm. This has originated from the electron-hole recombination of CdSe nanocrystal and defects or traps related transitions. The properties of these nanocomposites advocate their significant applications as semiconductor based luminescent materials.

  2. Photoluminescence properties of cadmium-selenide quantum dots embedded in a liquid-crystal polymer matrix

    SciTech Connect

    Tselikov, G. I. Timoshenko, V. Yu.; Plenge, J.; Ruehl, E.; Shatalova, A. M.; Shandryuk, G. A.; Merekalov, A. S.; Tal'roze, R. V.

    2013-05-15

    The photoluminescence properties of cadmium-selenide (CdSe) quantum dots with an average size of {approx}3 nm, embedded in a liquid-crystal polymer matrix are studied. It was found that an increase in the quantum-dot concentration results in modification of the intrinsic (exciton) photoluminescence spectrum in the range 500-600 nm and a nonmonotonic change in its intensity. Time-resolved measurements show the biexponential decay of the photoluminescence intensity with various ratios of fast and slow components depending on the quantum-dot concentration. In this case, the characteristic lifetimes of exciton photoluminescence are 5-10 and 35-50 ns for the fast and slow components, respectively, which is much shorter than the times for colloidal CdSe quantum dots of the same size. The observed features of the photoluminescence spectra and kinetics are explained by the effects of light reabsorption, energy transfer from quantum dots to the liquid-crystal polymer matrix, and the effect of the electronic states at the CdSe/(liquid crystal) interface.

  3. Photoluminescence and electrical properties of silicon oxide and silicon nitride superlattices containing silicon nanocrystals

    NASA Astrophysics Data System (ADS)

    Shuleiko, D. V.; Ilin, A. S.

    2016-08-01

    Photoluminescence and electrical properties of superlattices with thin (1 to 5 nm) alternating silicon-rich silicon oxide or silicon-rich silicon nitride, and silicon oxide or silicon nitride layers containing silicon nanocrystals prepared by plasma-enhanced chemical vapor deposition with subsequent annealing were investigated. The entirely silicon oxide based superlattices demonstrated photoluminescence peak shift due to quantum confinement effect. Electrical measurements showed the hysteresis effect in the vicinity of zero voltage due to structural features of the superlattices from SiOa93/Si3N4 and SiN0.8/Si3N4 layers. The entirely silicon nitride based samples demonstrated resistive switching effect, comprising an abrupt conductivity change at about 5 to 6 V with current-voltage characteristic hysteresis. The samples also demonstrated efficient photoluminescence with maximum at ∼1.4 eV, due to exiton recombination in silicon nanocrystals.

  4. Influence of surface coating on structural and photoluminescent properties of CaMoO₄:Pr nanoparticles.

    PubMed

    Ansari, Anees A; Parchur, A K; Alam, M; Labis, J; Azzeer, Abdallah

    2014-07-01

    CaMoO4:Pr(core), CaMoO4:Pr@CaMoO4 (core/shell) and CaMoO4:Pr@CaMoO4@SiO2 (core/shell/shell) nanoparticles were synthesized using polyol method. X-ray diffraction (XRD), thermogravimatric analysis (TGA), UV-vis absorption, optical band gap energy analysis, Fourier transform infrared (FTIR), FT-Raman and photoluminescence (PL) spectroscopy were employed to investigate the structural and optical properties of the synthesized core and core/shell nanoparticles. The results of the XRD indicate that the obtained core, core/shell and core/shell/shell nanoparticles crystallized well at ~150 °C in ethylene glycol (EG) under urea hydrolysis. The growth of the CaMoO4 and SiO2 shell (~12 nm) around the CaMoO4:Pr core nanoparticles resulted in an increase of the average size of the nanopaticles as well as in a broadening of their size distribution. These nanoparticles can be well-dispersed in distilled water to form clear colloidal solutions. The photoluminescence spectra of core, core/shell and core/shell/shell nanoparticles show the characteristic charge transfer emission band of MoO4 (2-) (533 nm) and Pr(3+) 4f(2) → 4f(2), with multiple strong (3)H4 → (3)P2, (1)D2 → (3)H4 and (3)P0 → (3) F2 transitions located at ~490, 605 and 652 nm, respectively. The emission intensity of the CaMoO4:Pr@CaMoO4 core/shell and CaMoO4:Pr@CaMoO4@SiO2 core/shell/shell nanoparticles increased ~4.5 and 1.7 times,respectively, with respect to those of CaMoO4:Pr core nanoparticles. This indicates that a significant amount of nonradiative centers existing on the surface of CaMoO4:Pr@CaMoO4 core/shell nanoparticles can be eliminated by the shielding effect of CaMoO4 shells.

  5. Surface chemistry and photoluminescence property of functionalized silicon nanoparticles

    NASA Astrophysics Data System (ADS)

    Gupta, Anoop; Wiggers, Hartmut

    2009-05-01

    We report an efficient method of producing macroscopic quantity of functionalized silicon nanoparticles (Si NPs) with bright photoluminescence (PL). Single crystalline Si NPs were synthesized in a microwave plasma reactor via pyrolysis of silane (SiH 4). Organic molecules were grafted onto the Si surface by reacting freshly etched NPs with 1-hexadecene at high temperature. Both freshly prepared and coated Si NPs were analyzed by Fourier transform infrared (FTIR) spectroscopy to evaluate the effectiveness of the surface modification. An increase in the PL intensity and a blue shift in the emission spectrum of functionalized Si NPs were observed compared to as-prepared NPs. The change in particle shape and morphology before and after the surface grafting was investigated by transmission electron microscopy (TEM). The electron diffraction patterns confirmed that Si NPs maintain their crystallinity after the functionalization process. In addition, functionalized Si NPs showed a red shift in the PL emission spectrum after air oxidation, which originated from the oxidation of remaining Si-H bonds on the surface.

  6. Physiochemical properties of greatly enhanced photoluminescence of aqueous dispersible upconversion CaF2:Yb/Er nanoparticles.

    PubMed

    Ansari, Anees A; Yadav, Ranvijay; Rai, S B

    2017-06-14

    Crystal phase morphological structure and optical properties of the as-prepared upconversion CaF2:Yb/Er(core) and sequential coating of an inert crystalline material and silica layers surrounding the seed core-nanoparticles (NPs) were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), optical absorption, FTIR spectroscopy and upconversion photoluminescence spectroscopy. Owing to the unique properties of CaF2 host matrix, we realized their practical applications in biomedical science to improve the upconversion luminescence property and aqueous dispersibility. The surface coating on the seed core particles will significantly influence the structural, optical band gap energy and upconversion luminescence properties. These NPs were well-dispersed in aqueous and non-aqueous solvents to form clear colloidal solutions. The colloidal solutions of three samples show a characteristic optical absorption band in UV/Visible region. As a result, optical band gap gradually decreases after sequential growth of the inert shell and amorphous silica due to an increase in the crystalline size. Comparative upconversion luminescence analysis showed that after inert shell growth, the upconversion intensity was greatly improved, and such an improvement was found to arise from efficient suppression of surface-related deactivation from the core nanocrystals. Interestingly, growth of an inert (CaF2) shell over the seed core NPs shows intense upconversion emission lines under 980 nm NIR laser excitation, highlighting their promising applications, such as multi-analyte biolabels, staining, displays and other photonic based technological applications.

  7. Growth and photoluminescence properties of PbS nanocubes

    NASA Astrophysics Data System (ADS)

    Cao, Huaqiang; Wang, Guozhi; Zhang, Sichun; Zhang, Xinrong

    2006-07-01

    This paper reports the synthesis of semiconductor nanocrystals of PbS through a facile and inexpensive synthetic route between lead acetate [Pb(Ac)2·3H2O] and dithioglycol (HSCH2CH2SH) without any surfactant. The products were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Raman spectroscopy, x-ray photelectron spectroscopy (XPS) and infrared (IR) spectroscopy. The size of cube-shaped PbS nanocrystals can be controlled by changing the relative amount of Pb(Ac)2·3H2O and dithioglycol. Smaller cube-shaped PbS nanocrystals were obtained at higher sulfur content in the reaction system. The nanometre-sized single crystals of PbS measure ~83 nm × 59 nm × 22 nm and 39 nm × 10 nm × 7 nm, for lead acetate:dithioglycol ratios of 1:0.375 (denoted as PbS-1) and 1:1.5 (denoted as PbS-2), respectively, when a mixture of NaOH solution of lead acetate and ethyl alcohol solution of dithioglycol is maintained at 220 °C for 4 h in a Teflon-lined autoclave. XRD patterns and HRTEM images confirm the crystalline structure of the PbS crystals. TEM helped to determine the dimension of the single crystals. Raman, XPS and IR helped to further demonstrate the purity of the as-synthesized samples. The optical absorption spectra of suspensions of the these crystals in glycol show shifts in absorption band edge for as-prepared sample PbS-1 from 246 to 271 nm and for PbS-2 from 246 to 275 nm, after four days of storage, respectively. The photoluminescence peaks from the two samples are located at 434 and 433 nm for photoexcitation radiation of 315-355 nm, thus exhibiting a Stokes shift compared with band edge energy. The principal contribution of this work is that the nanometre-size PbS single crystals are prepared without using a surfactant or templating agent. The formation of a five-membered ring via the chelation between the Pb2+ ion and dithioglycol is considered to be crucial in this mechanism.

  8. 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

    2014-11-03

    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.

  9. 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.

  10. Photoluminescent Properties of Composites Based on the Liquid Crystal 5CB with Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Bezrodna, T. V.; Klishevich, G. V.; Nesprava, V. V.; Melnyk, V. I.; Roshchin, A. N.; Skryshevskyi, Yu. A.

    2017-01-01

    We have studied the influence of inorganic particles on the photoluminescent properties of the nematic liquid crystal 5CB in composites based on carbon nanotubes (CNTs) and hybrid nanoparticles consisting of carbon nanotubes and platelets of the organically modified mineral montmorillonite (MMT). We show that the photoluminescence (PL) of 5CB + CNT composites is characterized by excimer emission of the 5CB molecules. Adding carbon nanotubes to the liquid crystal medium leads to a considerable decrease in the photoluminescence intensity, but has practically no effect on the bulk structural alignment in the organic matrix. Hybrid CNT-MMT particles form a uniform coagulation network in the composite with 5CB and significantly disrupt the nematic structure of the liquid crystal. Bent conformations of the 5CB molecules appear which are typical of the liquid crystal monomers. The presence of the indicated 5CB conformers in the system and also the weaker interaction between the liquid crystal and the inorganic filler explain the increase in the photoluminescence intensity for the composite 5CB + CNT-MMT compared with the emission characteristics for the original liquid crystal.

  11. Microwave Synthesis, Characterization, and Photoluminescence Properties of Nanocrystalline Zirconia

    PubMed Central

    Singh, A. K.; Nakate, Umesh T.

    2014-01-01

    We report synthesis of ZrO2 nanoparticles (NPs) using microwave assisted chemical method at 80°C temperature. Synthesized ZrO2 NPs were calcinated at 400°C under air atmosphere and characterized using FTIR, XRD, SEM, TEM, BET, and EDS for their formation, structure, morphology, size, and elemental composition. XRD results revealed the formation of mixed phase monoclinic and tetragonal ZrO2 phases having crystallite size of the order 8.8 nm from most intense XRD peak as obtained using Scherrer formula. Electron microscope analysis shows that the NPs were less than 10 nm and highly uniform in size having spherical morphology. BET surface area of ZrO2 NPs was found to be 65.85 m2/g with corresponding particle size of 16 nm. The band gap of synthesized NPs was found to be 2.49 eV and PL spectra of ZrO2 synthesized NPs showed strong peak at 414 nm, which corresponds to near band edge emission (UV emission) and a relatively weak peak at 475 and 562 nm. PMID:24578628

  12. Observational Properties of Protoplanetary Disk Gaps

    NASA Astrophysics Data System (ADS)

    Varnière, Peggy; Bjorkman, J. E.; Frank, Adam; Quillen, Alice C.; Carciofi, A. C.; Whitney, Barbara A.; Wood, Kenneth

    2006-02-01

    We study the effects of an annular gap induced by an embedded protoplanet on disk scattered light images and the infrared spectral energy distribution (SED). We find that the outer edge of a gap is brighter in the scattered light images than a similar location in a gap-free disk. The stellar radiation that would have been scattered by material within the gap is instead scattered by the disk wall at the outer edge of the gap, producing a bright ring surrounding the dark gap in the images. Given sufficient resolution, such gaps can be detected by the presence of this bright ring in scattered light images. A gap in a disk also changes the shape of the SED. Radiation that would have been absorbed by material in the gap is instead reprocessed by the outer gap wall. This leads to a decrease in the SED at wavelengths corresponding to the temperature at the radius of the missing gap material, and to a corresponding flux increase at longer wavelengths corresponding to the temperature of the outer wall. We note, however, that the presence of an annular gap does not change the bolometric IR flux; it simply redistributes the radiation previously produced by material within the gap to longer wavelengths. Although it will be difficult on the basis of the SED alone to distinguish between the presence of a gap and other physical effects, the level of changes can be sufficiently large to be measurable with current instruments (e.g., Spitzer).

  13. 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.

  14. Transition Metal Titanophosphates with Intercalated Molecular Photoluminescence and Catalytic Properties.

    PubMed

    Hung, Ling-I; Chen, Pei-Lin; Yang, Jia-Hao; Peng, Chi-How; Wang, Sue-Lein

    2017-08-10

    In this study, α-TiP layered structure incorporating a heterometal center for organic ligand binding to enhance structural complexity and functionality were prepared. The protons of the α-TiP layer were replaced with zinc ions coordinated by 4-pyridinecarboxylic acid (PCA) and water to form a layer structure, TiZn(PO4 )2 (H2 O)(PCA) (1). The tetrahedral zinc center with coordinated water in 1 is unprecedented in zincophosphate or zinc-MOF systems and is usually only found in metalloenzyme systems. The neutral zincotitanophosphate layers, tightly stacked through hydrogen bonds, showed velcro-like behavior on intercalating 4,4'-trimethylenedipyridine (TMDP) reversibly. It rendered a remarkable luminescence property to 1, emitting blue-to-white light under UV excitation. Surprisingly, the replacement of TMDP for PCA in the hydrothermal synthesis still resulted in 1, plus another structure, Ti4 Zn2 (H2 TPB)(PO4 )4 (HPO4 )4 (H2 PO4 )2 (2) (TPB=1,2,4,5-tetra(4-pyridyl)benzene). Clearly, in situ C-C cracking and C-C coupling of TMDP simultaneously occurred to generate PCA and TPB and thereafter the oxidant, Zn(NO3 )2 , was quantitatively determined to isolate crystal 1 from 2. The structure of 2 also featured α-TiP layers with pedant Zn tetrahedra but formed a three-dimensional neutral framework through TPB. For the first time, α-TiP-derived structures and their properties have been elucidated, which help in understanding intriguing in situ ligand formation and intercalation-induced luminescence, to exploit potential photocatalysis in polymerization. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. 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

    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 mediated by defect luminescence of the nanoparticles. Indications for an influence of shape on photoluminescence (PL) properties were found. Finally, rod-like Eu@ZnO colloids were used as tracers to investigate their uptake into biological samples like HeLa cells. The PL was sufficient for identifying green and red emission under visible light excitation. Electronic supplementary information (ESI) available: ESI-1: Pure ZnO nanorods prepared via the emulsion-based method. ESI-2: Additional analytical data for different M@ZnO particles grown for χM = 0.03% and χM = 0.7%. ESI-3: Proposed effect of cations on the growth of ZnO nanorods. ESI-4: Additional data for differently shaped particles. ESI-5: Additional analytical data for the different Eu@ZnO particles grown for different Eu3+ concentration. ESI-6: Eu@ZnO nanorods with different length. ESI-7: HRTEM analysis of Eu@ZnO. ESI-8: XPS and EPR spectroscopy performed on Eu@ZnO nanorods. ESI-9: Micro-Raman comparison between ZnO and Eu@ZnO nanorods. ESI-10: Additional PL data for Eu@ZnO. See DOI: 10.1039/c5nr02550h

  16. 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.

  17. Synthesis and unique photoluminescence properties of nitrogen-rich quantum dots and their applications.

    PubMed

    Chen, Xiuxian; Jin, Qingqing; Wu, Lizhu; Tung, ChenHo; Tang, Xinjing

    2014-11-10

    Nitrogen-rich quantum dots (N-dots) were serendipitously synthesized in methanol or aqueous solution at a reaction temperature as low as 50 °C. These N-dots have a small size (less than 10 nm) and contain a high percentage of the element nitrogen, and are thus a new member of quantum-dot family. These N-dots show unique and distinct photoluminescence properties with an increasing percentage of nitrogen compared to the neighboring carbon dots. The photoluminescence behavior was adjusted from blue to green simply through variation of the reaction temperature. Furthermore, the detailed mechanism of N-dot formation was also proposed with the trapped intermediate. These N-dots have also shown promising applications as fluorescent ink and biocompatible staining in C. elegans. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Photoluminescence, ferroelectric, dielectric and piezoelectric properties of Er-doped BNT-BT multifunctional ceramics

    NASA Astrophysics Data System (ADS)

    Lau, Chi Man; Xu, Xiao Wu; Kwok, K. W.

    2015-05-01

    0.93(Bi0.5-x/0.93Erx/0.93Na0.5)TiO3-0.07BaTiO3 photoluminescent ceramics have been prepared by a conventional ceramic fabrication technique and their photoluminescence, ferroelectric, dielectric and piezoelectric properties have been studied. Under an excitation of 980 nm, the ceramics exhibit visible up-conversion luminescent emissions at 532 nm (green), 540 nm (green) and 600 nm (red), as well as broadband down-conversion luminescent emissions in near-infrared (1.44-1.66 μm) and mid-infrared (2.62-2.84 μm) regions. The quenching concentration for the ceramics is high, about 6%, and both the visible and invisible emissions are very strong. Among the emissions, the photoluminescence intensity of the red emission band increases most significantly by more than 47 times as the Er-concentration increases from 0.005 to 0.07. As a result, the Commission Internationale de L'Eclairage chromaticity coordinates shift from (0.29, 0.69) to (0.49, 0.50), and the emission color changes from green to yellowish green. Owing to the establishment of a dynamic circulatory energy process at high Er-concentrations, the photoluminescence intensity of the mid-infrared emission increases significantly by more than 4 times at the expense of the near-infrared emission. Together with the good ferroelectric and piezoelectric properties, the ceramics should be promising candidates for multifunctional optoelectronic applications.

  19. Glass Former Effects on Photoluminescence and Optical Properties of Some Heavy Metal Oxide Glasses Doped with Transition Metal Ions

    NASA Astrophysics Data System (ADS)

    Marzouk, M. A.; Abo-Naf, S. M.; Zayed, H. A.; Hassan, N. S.

    2017-03-01

    Heavy metal oxide (PbO and Bi2O3) glasses doped with transition metal (TM) ions (TiO2, V2O5, Cr2O3, and MnO2) and having low content of common glass formers (B2O3, SiO2, or P2O5) were prepared by the conventional melt annealing method. Ultraviolet, visible absorption, and photoluminescence properties of these glasses were measured, and the data were employed to investigate the prepared glassy samples. The optical absorption spectra of TiO2 and V2O5 exhibited three bands centered at about 240, 305, and 380 nm, followed by a broad asymmetrical near-visible band centered at 425-432 nm, while Cr2O3 and MnO2 exhibited an extended visible peak at 517-548 nm. Results showed that the luminescence intensity changed with different transition metal oxides. From the absorption edge data, the values of the optical band gap Eopt and Urbach energy (ΔE) were calculated. The calculated values of the optical energy gap were found to be dependent on the glass composition. The changing values of optical band gap and band tail can be related to the structural changes that are taking place in the glass samples. The variations of the luminescence intensity, values of optical band gap, band tail, and refractive index gave an indication of the potential use of the prepared glasses to design novel optical functional materials with higher optical performance.

  20. The influence of amphiphilic additional agents on the morphology and photoluminescence properties of calcium carbonate phosphor

    NASA Astrophysics Data System (ADS)

    Mou, Yongren; Kang, Ming; Liu, Min; Wang, Feng; Chen, Kexu; Sun, Rong

    2017-06-01

    In order to investigate the effect of amphiphilic additional agents on the morphology (particle shape, particle size and particle size distribution) and photoluminescence performance of calcium carbonate phosphor, the phosphors AA-CaCO3:Eu3+ (AA = glycerol or sodium dodecyl sulfate) were synthesized by the microwave-assisted co-precipitation method using glycerol (Gly) and sodium dodecyl sulfate (SDS) as amphiphilic additional agents (AA), respectively. The phase structure, morphology and luminescent properties of the as-synthesized samples were characterized by X-ray diffraction, scanning electron microscope, laser diffraction particle size analyzer and Fluorescence spectrophotometer, respectively. The results showed that the phase structure and morphology of AA-CaCO3:Eu3+ changed along with different types and amount of amphiphilic additional agents evidently. The particle size of Gly-CaCO3 decreased to 1.383 µm when the volume ratio reached 8:2 (Gly:H2O). Photoluminescence (PL) spectra show that all the AA-CaCO3:Eu3+ phosphors exhibit strong red emission peak originating from electric-dipole transition 5D0 → 7F2 (614 nm) of Eu3+ ions and the amphiphilic molecules (Gly and SDS) had a huge influence on photoluminescence intensity.

  1. A new stepped tetranuclear copper(II) complex: synthesis, crystal structure and photoluminescence properties.

    PubMed

    Gungor, Elif

    2017-05-01

    Binuclear and tetranuclear copper(II) complexes are of interest because of their structural, magnetic and photoluminescence properties. Of the several important configurations of tetranuclear copper(II) complexes, there are limited reports on the crystal structures and solid-state photoluminescence properties of `stepped' tetranuclear copper(II) complexes. A new Cu(II) complex, namely bis{μ3-3-[(4-methoxy-2-oxidobenzylidene)amino]propanolato}bis{μ2-3-[(4-methoxy-2-oxidobenzylidene)amino]propanolato}tetracopper(II), [Cu4(C11H13NO3)4], has been synthesized and characterized using elemental analysis, FT-IR, solid-state UV-Vis spectroscopy and single-crystal X-ray diffraction. The crystal structure determination shows that the complex is a stepped tetranuclear structure consisting of two dinuclear [Cu2(L)2] units {L is 3-[(4-methoxy-2-oxidobenzylidene)amino]propanolate}. The two terminal Cu(II) atoms are four-coordinated in square-planar environments, while the two central Cu(II) atoms are five-coordinated in square-pyramidal environments. The solid-state photoluminescence properties of both the complex and 3-[(2-hydroxy-4-methoxybenzylidene)amino]propanol (H2L) have been investigated at room temperature in the visible region. When the complex and H2L are excited under UV light at 349 nm, the complex displays a strong blue emission at 469 nm and H2L displays a green emission at 515 nm.

  2. Synthesis and photoluminescence property of nanostructured sol-gel antimony tin oxide film on silica glass

    NASA Astrophysics Data System (ADS)

    Dua, Laxmikanta; Biswas, Prasanta K.

    2013-05-01

    Sol-gel based spin coated nanostructured films of tetragonal phase of antimony (10 at%) doped tin oxide (ATO) were prepared on silica glass. XRD and TEM images identify the crystallite size lying in the range, ∼3.4-9.8 nm. Quantum confinement was observed in the nanoclusters. Evaluated band gaps at 3.62 eV correspond to the transition for bulk ATO and 4.51 eV, 5.26 eV for excitons and oxygen deficiency. Schemes have been proposed for absorption and photoluminescence excitation (PLE). Two excitonic transitions were observed at 275 nm and 310 nm for different nanocluster sizes. Evaluation of mean free path and Fermi energy correspond to ionized scattering and degeneracy of the ATO films.

  3. 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.

  4. 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

  5. Study of the effects of structural properties on the photoluminescence behavior of erbium thin films

    NASA Astrophysics Data System (ADS)

    Kamineni, Himani S.; Gallis, Spyros; Huang, Mengbing; Kaloyeros, Alain E.

    2012-10-01

    Erbium oxide is a promising candidate for possible applications as Si-based light emitting devices in nanoscale electronics. The current report presents findings pertaining to the effects of the structural properties of erbium-based thin films on their photoluminescence characteristics. Erbium metal films were deposited on silicon via electron beam evaporation followed by thermal oxidation. The effects of post-deposition annealing conditions on the structural and optical properties of the thin films were examined using a variety of techniques, such as spectroscopic ellipsometry, xray diffraction, and x-ray photoelectron spectroscopy. It was shown that the thin films evolved as function of thermal treatment from an Er-rich to an ErO-rich (700°C) to an Er2O3-rich (900°C) phase due to an increase in oxygen incorporation with higher oxidation temperatures. At temperatures >= 1000°C, out-diffusion of silicon from the substrate led to the formation of erbium monosilicate. Furthermore, the photoluminescence spectra of these various phases were measured, and the correlation between structural properties and luminescence characteristics will be discussed in this paper.

  6. 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.

  7. 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.

  8. Conductive properties of switchable photoluminescence thermosetting systems based on liquid crystals.

    PubMed

    Tercjak, Agnieszka; Gutierrez, Junkal; Ocando, Connie; Mondragon, Iñaki

    2010-03-16

    Conductive properties of different thermosetting materials modified with nematic 4'-(hexyl)-4-biphenyl-carbonitrile (HBC) liquid crystal and rutile TiO(2) nanoparticles were successfully studied by means of tunneling atomic force miscroscopy (TUNA). Taking into account the liquid crystal state of the HBC at room temperature, depending on both the HBC content and the presence of TiO(2) nanoparticles, designed materials showed different TUNA currents passed through the sample. The addition of TiO(2) nanoparticles into the systems multiply the detected current if compared to the thermosetting systems without TiO(2) nanoparticles and simultaneously stabilized the current passed through the sample, making the process reversible since the absolute current values were almost the same applying both negative and positive voltage. Moreover, thermosetting systems modified with liquid crystals with and without TiO(2) nanoparticles are photoluminescence switchable materials as a function of temperature gradient during repeatable heating/cooling cycle. Conductive properties of switchable photoluminescence thermosetting systems based on liquid crystals can allow them to find potential application in the field of photoresponsive devices, with a high contrast ratio between transparent and opaque states.

  9. The photoluminescence properties of Er{sup 3+}-doped ZrO{sub 2} nanotube arrays prepared by anodization

    SciTech Connect

    Wang, Xixin; Zhao, Jianling; Du, Peng; Guo, Limin; Xu, Xuewen; Tang, Chengchun

    2012-11-15

    Graphical abstract: Display Omitted Highlights: ► Er{sup 3+}-doped ZrO{sub 2} nanotube arrays were prepared by anodization of Zr–Er alloy. ► Small tetragonal zirconia crystallites are tended to be formed due to the doping of Er{sup 3+}. ► Under excitation at 317 nm, the ZrO{sub 2} nantube arrays have strongest photoluminescence intensity. -- Abstract: Er{sup 3+}-doped ZrO{sub 2} nanotube arrays were prepared by anodization of Zr–Er alloy which was obtained by melting zirconium with 1.0 wt% erbium. The morphology, structure and photoluminescence properties were studied through scanning electron microscope, transmission electron microscope, X-ray diffraction and photoluminescence analyzer. X-ray diffraction results indicate that doping of Er{sup 3+} affects the crystal structure and grain size obviously and the Er{sup 3+}-doped samples tend to form small tetragonal grains. Photoluminescence analyses show that when Er{sup 3+}-doped zirconia nanotube arrays are excited at 317 nm, there are two strong photoluminescence emission peaks at 373 nm and 415 nm. When the excitation wavelength is 257 nm, a photoluminescence emission peak appears at 363 nm. Under same measurement conditions, emission peaks of the undoped ZrO{sub 2} nanotube arrays are very weak.

  10. 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.

  11. Size-dependent photoluminescent property of hybrid nanoparticlesconsisted with YVO4:Eu3+ and gold

    NASA Astrophysics Data System (ADS)

    Zhang, W.; Yan, Y. L.; Guo, F. Q.; Zhong, L. S.; Wang, J.; Wang, Y.; Xu, Y. H.

    2017-03-01

    The hydrothermally synthesizedYVO4:Eu3+nanophosphors were mixed with gold nanoparticles with different sizes to form hybrid nanoparticles. The microstructure and luminescent properties of all hybrid nanoparticles were charaterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Visible absorption spectrum (UV-Vis), and photoluminescence (PL) spectroscopy. The growth process of gold nanoparticles prepared by seeding growth method was discussed firstly. Furthermore, the effects of grain size of gold nanoparticles on the fluorescent property of hybrid nanoparticles were investigated in detail. All the emission spectra presented the characteristic red emission of Eu3+. The emission intensity of hybrid nanoparticles was increasing with the growing of gold nanoparticles. The influential mechanism was discussed as well.

  12. [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+.

  13. Bandedge optical properties of MBE grown GaAsBi films measured by photoluminescence and photothermal deflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Beaudoin, M.; Lewis, R. B.; Andrews, J. J.; Bahrami-Yekta, V.; Masnadi-Shirazi, M.; O'Leary, S. K.; Tiedje, T.

    2015-09-01

    The bandedge optical properties of GaAsBi films, as thick as 470 nm, with Bi content varying from 0.7% Bi to 2.8% Bi grown by molecular beam epitaxy on GaAs substrates are measured by photoluminescence (PL) and photothermal deflection spectroscopy (PDS). The PDS spectra were fit with a modified Fernelius model which takes into account multiple reflections within the GaAsBi layer and GaAs substrate. Three undoped samples and two samples that are degenerately doped with silicon are studied. The undoped samples show a clear Urbach absorption edge with a composition dependent bandgap that decreases by 56 meV/% Bi and a composition independent Urbach slope parameter of 25 meV due to absorption by Bi cluster states near the valence band. The doped samples show a long absorption tail possibly due to absorption by gap states and free carriers in addition to a Burstein-Moss bandgap shift. PL of the undoped samples shows a lower energy emission peak due to defects not observed in the usually available thin samples (50 nm or less) grown under similar conditions.

  14. Structural and photoluminescence properties of Gd implanted ZnO single crystals

    NASA Astrophysics Data System (ADS)

    Murmu, P. P.; Mendelsberg, R. J.; Kennedy, J.; Carder, D. A.; Ruck, B. J.; Markwitz, A.; Reeves, R. J.; Malar, P.; Osipowicz, T.

    2011-08-01

    We present the structural and photoluminescence properties of 30 keV gadolinium implanted and subsequently annealed zinc oxide (ZnO) single crystals. Rutherford backscattering and channeling results reveal a low surface region defect density which was reduced further upon annealing. For low implantation fluence, around 85% of the Gd atoms are estimated to be in sites aligned with the ZnO lattice, while for higher fluences the Gd is largely disordered and likely forms precipitates. The Raman spectra of the implanted samples show defect-induced modes, which match the one-phonon density of states for the most heavily implanted samples. Annealing eliminates these features implying the removal of Gd-associated lattice disorder. Low temperature photoluminescence spectra revealed a red-shift in the defect emission, from green to orange/yellow, indicating the suppression of a deep level, which is thought to be due to oxygen vacancies. It is suggested that the orange/yellow emission is unmasked when the green emission is quenched by the presence of the implanted Gd atoms.

  15. Photoluminescence properties of defect emissions in Al-doped ZnO nanorod array thin films.

    PubMed

    Kim, Soaram; Nam, Giwoong; Park, Hyunggil; Yoon, Hyunsik; Kim, Min Su; Kim, Do Yeob; Kim, Sung-O; Leem, Jae-Young

    2013-09-01

    The power- and temperature-dependent photoluminescence properties of Al-doped ZnO nanorod array thin films grown by the hydrothermal method were investigated. The intensities of both the near-band-edge emission (NBE) and deep-level emission (DLE) as well as the overall spectral line shape were strongly affected by the excitation power. At low excitation power, the blue emission was found to show the highest intensity among the different emission lights. A low-temperature photoluminescence analysis revealed the bound-exciton-related luminescence peak at 3.362 eV. The dependence of peak energy with the excitation power indicates that these DLE processes are generated by DAP transitions. The overall intensity of DLE was found to decrease as the temperature increases. With regard to the blue emission (around 2.52 eV), it showed a well-pronounced shoulder at 200 K. The activation energy for this blue emission was 51.93 meV, which corresponds to the thermal dissociation energy required for the donor-acceptor pair transitions.

  16. Temperature variations in electrical and photoluminescence properties of ZnSe grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Giapis, Konstantinos P.; Lu, Da-Chen; Jensen, Klavs F.; Potts, John E.

    1990-07-01

    The effect of growth temperature on the optoelectronic properties of epitaxial ZnSe grown by metalorganic chemical vapor deposition (MOCVD) on GaAs (100) from dimethyl zinc and hydrogen selenide has been investigated in a vertical reactor. Chlorine was found to be the main donor impurity originating from Se, used to produce the hydrogen selenide. The deposited films were single crystalline for growth temperatures above 225°C and were characterized by low-temperature photoluminescence. With increasing growth temperature, the donor-bound excitonic emission decreased in intensity and linewidth, while the 77 K electron mobility increased. The trend continued until the free exciton became the dominant near-band-edge emission at a growth temperature of 350°C, at which point the films turned out to be highly resistive and Hall measurements could not be performed. High electron mobilities of 8000-9000 cm 2/V·s at 77 K were measured for growth temperatures of 325°C. The transition tto high resistivity was found to be accompanied by a sharp increase in the photoluminescence intensity of the Y0 emission, related to extended defects. Thermally activated dislocations and changes in the charge state of the Y0-related defect are proposed as possible mechanisms for these experimental observations.

  17. Ultrafast carrier dynamics, band-gap renormalization, and optical properties of ZnSe nanowires

    NASA Astrophysics Data System (ADS)

    Tian, Lin; di Mario, Lorenzo; Zannier, Valentina; Catone, Daniele; Colonna, Stefano; O'Keeffe, Patrick; Turchini, Stefano; Zema, Nicola; Rubini, Silvia; Martelli, Faustino

    2016-10-01

    In this paper, we present a comprehensive study of the carrier dynamics and optical properties of ZnSe nanowires (NWs). The transparency of the sample, obtained by the growth of the ZnSe NWs on glass, allowed us to perform transmittance, reflectance, photoluminescence (PL), time-resolved PL, and pump-probe transient absorption spectroscopy on as-grown samples. All measurements were performed at room temperature. Strong light trapping at the band-gap energy has been observed in reflectivity measurements. Fast transient absorption bleaching due to band filling and band-gap renormalization has been observed. The band-gap renormalization has a rise time constant of about 170 fs and a decay time of about 4 ps. Fast transient absorption bleaching is also observed at energies below the band gap, suggesting that intrinsic processes prevail over extrinsic photoinduced transitions in our high-quality NWs. The PL reveals the presence at room temperature of excitonic emission that shows a decay time of 0.5 ns. All of these features indicate that our ZnSe NWs have quality comparable to epitaxial films and can be used for optical devices and nonlinear optics.

  18. Optical properties of dielectric plates coated with gapped graphene

    NASA Astrophysics Data System (ADS)

    Klimchitskaya, G. L.; Mostepanenko, V. M.

    2017-01-01

    The optical properties of dielectric plates coated with gapped graphene are investigated on the basis of first principles of quantum electrodynamics. The reflection coefficients and reflectivities of graphene-coated plates are expressed in terms of the polarization tensor of gapped graphene and the dielectric permittivity of plate material. Simple approximate expressions for the required combinations of components of the polarization tensor applicable in the wide frequency region, where the presence of a gap influences the optical properties, are found. Numerical computations of the reflectivities of graphene-coated SiO 2 plates are performed for different values of the mass-gap parameter at different temperatures. It is shown that with an increasing gap width the reflectivity of a graphene-coated plate at the normal incidence decreases by up to a factor of 8 depending on the values of frequency and mass-gap parameter. The angle dependences of reflectivities for both polarizations of the incident electromagnetic waves have been computed for Si and SiO 2 plates coated with gapped graphene. We demonstrate that the TM reflectivity has a minimum value at some angle of incidence depending on the mass-gap parameter, frequency and temperature, whereas the TE reflectivity depends on the angle of incidence monotonously. However, for the graphene coatings with a nonzero mass-gap parameter the reflected light cannot be fully polarized. Possible applications of the obtained results are discussed.

  19. 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.

  20. Enhanced photocatalytic activity of C@ZnO core-shell nanostructures and its photoluminescence property

    NASA Astrophysics Data System (ADS)

    Chen, Tao; Yu, Shanwen; Fang, Xiaoxin; Huang, Honghong; Li, Lun; Wang, Xiuyuan; Wang, Huihu

    2016-12-01

    An ultrathin layer of amorphous carbon coated C@ZnO core-shell nanostructures were synthesized via a facile hydrothermal carbonization process using glucose as precursor in this work. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance UV-vis spectroscopy (DRS) were used for the characterization of as-prepared samples. Photoluminescence (PL) properties of C@ZnO samples were investigated using PL spectroscopy. The microstructure analysis results show that the glucose content has a great influence on the size, morphology, crystallinity and surface chemical states of C@ZnO nanostructures. Moreover, the as-prepared C@ZnO core-shell nanostructures exhibit the enhanced photocatalytic activity and good photostability for methyl orange dye degradation due to its high adsorption ability and its improved optical characteristics.

  1. Temperature-dependent photoluminescence properties of MnF2: Configurational-coordinate model analysis

    NASA Astrophysics Data System (ADS)

    Arai, Takahiro; Adachi, Sadao

    2011-05-01

    A white MnF2 powder is synthesized by chemical etching of Mn shots in an aqueous HF solution. The optical properties of this synthesized powder are investigated using photoluminescence (PL) analysis, PL excitation spectroscopy, diffuse reflectivity, and PL decay measurements. The MnF2 powder exhibits PL peaks in the red (˜600 nm) and infrared spectral regions (˜780 nm) under visible to ultraviolet excitation. These PL peaks are asymmetric with a tail on the long-wavelength side. Such spectral features and temperature-dependent PL intensities are well interpreted by a newly developed model with Huang-Rhys's factor as the electron-local vibration coupling strength. The ground- and excited-state energy level diagram for the Mn2+ ions in MnF2 is also proposed.

  2. Sonochemically prepared PbWO4 tetragonal-bipyramidal microcrystals and their photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Kannan, S.; Mohanraj, K.; Sivakumar, G.

    2015-03-01

    Lead tungstate (PbWO4) microcrystals were synthesized for the first time, via different concentrations of PVA assisted sonochemical process. The concentration of PVA acts as a structure directing agent and played an important role in the morphological control of resulting PbWO4 microcrystals. The product PbWO4 composing of Pb, W and O and Wsbnd O stretching vibration band of WO4 tetrahedrons were confirmed through XRD, FTIR, FESEM and EDS. The TG/DTA curves showed that the particles are crystallized at room temperature itself and the thermal stability of the product is really good. The optical properties of the product shows extraordinarily high room temperature photoluminescence intensity compared to without PVA assisted product.

  3. Structure, photoluminescent properties and photocatalytic activities of a new Cd(II) metal-organic framework

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng Yan; Ma, Wei Xing; Wang, Ming Yan; Yang, Xu Jie; Xu, Xing You

    2014-01-01

    A new metal-organic framework, [Cd(TDC)(bix)(H2O)]n (H2TDC = thiophene-2,5-dicarboxylic acid; bix = 1,4-bis(imidazol-1-ylmethyl)benzene), has been synthesized under hydrothermal conditions and structurally characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, UV-vis and single X-ray diffraction. Cd-MOF is a 2D infinite layer framework, which is further interconnected by hydrogen-bond interactions leading to a 3D supramolecular architecture. The photoluminescent properties of the Cd-MOF were investigated and this compound shows intense fluorescent emissions in the solid state. In addition, it exhibits good photocatalytic activities for the degradation of methyl organic under UV light irradiation.

  4. 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.

  5. Effect of dopant concentration on photoluminescence properties of Gd2O3:Eu3+

    NASA Astrophysics Data System (ADS)

    Selvalakshmi, T.; Bose, A. Chandra

    2013-02-01

    Red-emitting Gd2-xO3:Eux3+(x = 2,4,6at%) was synthesized by sol-gel method and its optical properties were studied. The formation of Gd2O3 and the presence of metal oxygen bond were confirmed from X-ray diffraction (XRD) and fourier transform infrared (FTIR) spectroscopy studies. Incorporation of Eu3+ in Gd3+ site was proved qualitatively by Energy dispersive X-ray analysis (EDX). A strong charge transfer band (CTB) at 254 nm was observed in the excitation spectra with varying intensity for different dopant concentrations. Photoluminescence (PL) spectra reported red emission peak at 611 nm corresponding to 5D0-7F2 transition between Eu3+ energy levels. Concentration quenching occurred at 2 at % and its critical distance was calculated. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) studies was carried out to study the morphological variations.

  6. 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.

  7. Photoluminescence properties of MgxZn1-xO films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Wu, T. Y.; Huang, Y. S.; Hu, S. Y.; Lee, Y. C.; Tiong, K. K.; Chang, C. C.; Chou, W. C.; Shen, J. L.

    2017-02-01

    The optical properties of MgxZn1-xO films with x=0.03, 0.06, 0.08, and 0.11 grown by molecular beam epitaxy (MBE) have been studied by temperature-dependent photoluminescence (PL) measurement. It is presented that the full-width at half-maximum (FWHM) of the 12 K PL spectrum of MgZnO films increases with increasing Mg concentration and would deviate significantly from the simulation curve of Schubert model with higher Mg contents. The abnormal broader PL FWHM is inferred from larger compositional fluctuation by incorporating higher Mg contents, which results in larger effect of excitonic localization to induce more significant S-shaped behavior of the PL peak energy with temperature dependence. Additionally, the degree of localization increases as the linear proportion of the PL FWHM, indicating that the excitonic behavior in MgZnO films belong to the strong localization effect.

  8. Growth and low-temperature photoluminescence properties of hybrid ZnO-SnO2 nanobelts

    NASA Astrophysics Data System (ADS)

    Sinha, S. K.; Rakshit, T.; Ray, S. K.; Bysakh, S.; Manna, I.

    2012-09-01

    Hybrid ZnO-SnO2 nanobelts were synthesized through a simple thermal evaporation technique without using any catalyst. Detailed microstructural investigation showed that the nanobelts possessed doped/alloyed wurtzite (ZnO) and rutile (SnO2) structures. The diameter and length of the nanobelts were in the ranges 100-200 and 20-40 µm, respectively. Low-temperature photoluminescence properties of the hybrid ZnO-SnO2 nanostructured aggregate revealed a red shift of near-band-edge emission peaks of ZnO with increasing temperature. The method of synthesis offers a convenient and effective technique of producing hybrid ZnO-SnO2 nanobelts for gas sensing in the large quantity.

  9. Effect of Zn doping on the photoluminescence properties of LiNbO3 single crystals

    NASA Astrophysics Data System (ADS)

    Murillo, J. G.; Herrera, G.; Vega-Rios, A.; Flores-Gallardo, S.; Duarte-Moller, A.; Castillo-Torres, J.

    2016-12-01

    An extraordinary violet luminescence at 418 nm together with the intrinsic blue band at 440 nm with excitation in the UV region (380 nm) was observed in a series of LiNbO3 single crystals doped with Zn. Structural and photoluminescence properties were studied by Raman, UV reflectance, and fluorospectrometry, respectively. The emission peaks in PL spectra varied in amplitude according to the level of concentration of Zn in LiNbO3 crystals. It was found, from Raman spectroscopy studies, a connection between the appearance of the new emission band centered at 418 nm and a diminishing in the Li concentration in crystals, which suggest the displacement of the Li ions from their regular sites by the Zn ions. The maximum peak intensity of each one of the three PL emission components found from a deconvolution process shows a linear dependence on the Zn concentration present in the crystals studied.

  10. 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.

  11. 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

  12. Preparation and photoluminescence properties of MMoO4 (M = Cu, Ni, Zn) nano-particles synthesized via electrolysis

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Yin, Jiajia; Min, Fanqi; Jia, Lili; Zhang, Daoming; Zhang, Quansheng; Xie, Jingying

    2017-01-01

    Metal molybdate (MMoO4, M = Cu, Ni, Zn) nano-particles were successfully synthesized by electrochemical method in a cation exchange membrane electrolytic cell with Na2MoO4 solution as anolyte, diluted hydrochloric acid (HCl) as catholyte, metal (Cu, Ni, Zn) as anode and stainless steel as cathode. The composition, morphology, structure, microstructure and photoluminescence property of the synthesized MMoO4 were investigated and characterized. The results show that the photoluminescence spectra of electrolytic synthesized MMoO4 have fine structures, which is markedly different from the existing research.

  13. 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.

  14. Electromechanical and Photoluminescence Properties of Al-doped ZnO Nanorods Applied in Piezoelectric Nanogenerators

    NASA Astrophysics Data System (ADS)

    Chang, Wen-Yang; Fang, Te-Hua; Tsai, Ju-Hsuan

    2015-02-01

    A piezoelectric nanogenerator based on Al-doped ZnO (AZO) nanorods with a V-zigzag layer is investigated at a low temperature. The growth temperature, growth time, growth concentration, photoluminescence (PL) spectrum, and AZO epitaxial growth on the ITO glass substrate using aqueous solution are reported and the associated electromechanical and PL properties are discussed. In general, the properties of piezoelectric nanogenerators and their functionality at ultralow temperatures (near liquid helium temperature) are important for applications in extreme environments. A V-zigzag layer is used to enhance the bending and compression deformation of the piezoelectric nanogenerator. The electromechanical properties of AZO nanorods are tested using an ultrasonic wave generator. Results show that the percent transmittance decreases with increasing growth time and growth temperature. The intensities of the PL spectrum and the (002) peak orientation increases with increasing growth temperature. AZO at a low growth temperature of 90 C has good piezoelectric harvesting efficiency when the piezoelectric nanogenerator has a zigzag structure. The average current, voltage, and power density of the piezoelectric harvesting are 0.76 A, 1.35 mV, and 1.026 nW/mm, respectively. These results confirm the feasibility of growing AZO at low temperature. AZO nanorods have potential for energy harvester applications.

  15. Photoluminescence properties of zinc white: an insight into its emission mechanisms through the study of historical artist materials

    NASA Astrophysics Data System (ADS)

    Artesani, A.; Bellei, S.; Capogrosso, V.; Cesaratto, A.; Mosca, S.; Nevin, A.; Valentini, G.; Comelli, D.

    2016-12-01

    While the photophysical properties of ZnO nanostructures have been widely explored, less research has focused on the bulk material present in artist pigments. This study is based on the analysis of historical pastels, representative of artist materials available at the turn of the twentieth century, and of the pure powder pigment as the control sample. The study of the intensity of the photoluminescence emission as a function of the fluence and of the nanosecond and microsecond emission decay kinetic properties allows the elucidation of the emission mechanisms in control ZnO and historical samples containing ZnO. Data suggest that in historical samples the near-band-edge free-exciton photoluminescence emission, typically occurring in the pure semiconductor, is influenced by the interaction of the pigment with surrounding organic binding material. Conversely, crystal defects, typically expected in historical samples following the imperfect synthesis process available at the beginning of the twentieth century, introduce minor modifications to the photoluminescence emission. The study further suggests that zinc carboxylates, detected in all historical samples and known to introduce characteristic groups on the surface of ZnO, could be responsible for changes in emission mechanisms. Research demonstrates how photoluminescence decay kinetics and the study of the dependence of the emission intensity on the fluence are powerful methods for elucidating the nature of the mechanism processes in luminescent semiconductor pigments.

  16. Electronic structure of narrow gap semiconductors: Understanding gap formation and thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Larson, Paul Melvin

    Electronic band structure calculations are invaluable theoretical tools to understand structural, transport, and optical properties of materials. We have used this tool in the search for new high performance thermoelectric materials, which are usually narrow-gap semiconductors. We have studied the electronic structures of these systems both to understand which properties of the band structure are most important for thermoelectric properties and the nature of the gap formation. Narrow-gap semiconductors lie between metals and wide-gap semiconductors, so understanding the nature of the gap formation is very important. The small band gaps in the systems we have studied generally arise from hybridization between different bands. We have used the local density approximation (LDA) and the generalized gradient approximation (GGA) within density functional theory (DFT). These have been implemented using the full-potential linearized augmented planewave (FLAPW) method within the WIEN97 package. This state-of-the-art method is among the most accurate methods for calculating the electronic structure of solids. We have studied four classes of compounds. These include the half-Heusler compounds, the ternary Zintl-phase compounds, the simple chalcogenides, and the complex chalcogenides. The ternary half-Heusler compounds, considered having a stuffed NaCl structure, show promising thermoelectric properties. The band gap formation is understood by starting with the semi-metallic binary NaCl compounds from which they are formed. Adding the transition (or noble) metal atom causes a strong p-d hybridization near the Fermi energy which opens up the band gap. This hybridization also leads to highly anisotropic effective masses at the conduction band minimum which are found in the best thermoelectric materials. Similar band gap formation is found in the ternary Zintl-phase compounds which are considered a stuffed Th3P4 structure. The band gaps in these ternary compounds are larger than

  17. Optical properties study of InxGa1-xAs/GaAs structures using spectral reflectance, photoreflectance and near-infrared photoluminescence

    NASA Astrophysics Data System (ADS)

    Habchi, M. M.; Bedoui, M.; Tounsi, N.; Zaied, I.; Rebey, A.; El Jani, B.

    2014-09-01

    Optical properties of InxGa1-xAs films grown on GaAs substrates by metalorganic vapor phase epitaxy were investigated. Spectral reflectance (SR) and photoreflectance (PR) at room temperature and near-infrared photoluminescence (PL) at 10 K were performed. SR signals in the range of 200-1700 nm provided the x-dependence of the critical point energies E1, E1 + Δ1 and E2. Furthermore, band-gap and spin-orbit splitting energies, as well as their broadening parameters were determined from PR spectra and studied as function of In composition ranging from 0 to 0.37. On the other hand, the origins of luminescence bands observed in PL spectra were revealed. A redshift of 16 meV/%In in the band-to-band transition was obtained. All results issued from different characterizations tools are correlated and compared to the literature.

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

    SciTech Connect

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

    2016-01-14

    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 CH{sub 4}-H{sub 2}-N{sub 2} 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.

  19. Spectroscopic and Photoluminescent Properties of Indium Zinc Oxide (IZO) and IZO/Ag/IZO Sandwiched Film

    NASA Astrophysics Data System (ADS)

    Yanome, Kazuki; Kiba, Takayuki; Kawamura, Midori; Abe, Yoshio; Kim, Kyung Ho; Takayama, Junichi; Murayama, Akihiro

    2017-07-01

    We report the ellipsometric and photoluminescence (PL) properties of Indium zinc oxide (IZO) films, which were grown by radio frequency sputtering under Ar and O2 atmospheres. IZO films grown under an O2 atmosphere (IZO (O2)) showed enhanced PL properties when compared to the films grown under an Ar atmosphere (IZO (Ar)), particularly with respect to the band-edge emission. The enhancement of band-edge emission can be attributed to the reduction in the non-emissive defect states related to oxygen vacancies, which were repaired by sputtering under O2 atmosphere, whereas the PL enhancement in green region is probably due to the formation of the different types of defects under the excess oxygen environment. This was also supported by the results of time-resolved PL measurements, where the band-edge emission of IZO (Ar) showed rapid decay with a 50 ps lifetime, which indicates the dominance of the relaxation pathway to underlying defect states. In contrast, the PL decay profiles of IZO (O2) for band-edge and emissive defect states showed moderate decay with time-constants of 2.3 ns and 5.7 ns, respectively. The exciton relaxation dynamics were sensitive to the presence and its kinds of defect states, which were controlled by the growth conditions.

  20. 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.

  1. Room temperature photoluminescence properties of ZnO nanorods grown by hydrothermal reaction

    SciTech Connect

    Iwan, S.; Fauzia, Vivi; Umar, A. A.; Sun, X. W.

    2016-04-19

    Zinc oxide (ZnO) nanorods were fabricated by a hydrothermal reaction on silicon (Si) substrate at 95 °C for 6 hours. The ZnO seed layer was fabricated by depositing ZnO thin films on Si substrates by ultrasonic spray pyrolisis (USP). The annealing effects on crystal structure and optical properties of ZnO nanorods were investigated. The post-annealing treatment was performed at 800 °C with different environments. The annealed of ZnO nanorods were characterized by X-ray diffraction (XRD) and photoluminescence (PL) in order to analyze crystal structure and optical properties, respectively. The results show the orientations of [002], [101], [102], and [103] diffraction peaks were observed and hexagonal wurtzite structure of ZnO nanorods were vertically grown on Si substrates. The room temperature PL spectra show ultra-violet (UV) and visible emissions. The annealed of ZnO nanorods in vacuum condition (3.8 × 10{sup −3} Torr) has dominant UV emission. Meanwhile, non-annealed of ZnO nanorods has dominant visible emission. It was expected that the annealed of ZnO in vacuum condition suppresses the existence of native defects in ZnO nanorods.

  2. Tetranuclear Heterometallic {Zn2Eu2} Complexes With 1-Naphthoate Anions: Synthesis, Structure and Photoluminescence Properties.

    PubMed

    Goldberg, Anna; Kiskin, Mikhail; Shalygina, Olga; Kozyukhin, Sergey; Dobrokhotova, Zhanna; Nikolaevskii, Stanislav; Sidorov, Alexey; Sokolov, Sergey; Timoshenko, Victor; Goloveshkin, Alexander; Eremenko, Igor

    2016-02-18

    A series of new tetranuclear heterometallic Zn(II) -Eu(III) complexes have been synthesized, that is, (bpy)2 Zn2Eu2 (naph)10 (1), (bpy)2 Zn2Eu2 (naph)8 (NO3)2 (2), and (phen)2 Zn2Eu2 (naph)8 (NO3)2 (3), and other ones, where naph(-) is the 1-naphthoate anion, bpy=2,2'-bipyridyl, and phen=1,10-phenanthroline. The solid-phase complexes consist of large supramolecular ensembles due to stacking interactions between the aromatic ligands. Photoluminescence (PL) measurements were carried out to study PL spectra, lifetimes and quantum yields (QY) of the synthesized complexes at different temperatures. The external QY for the solid phases of complexes under UV excitation was found to exceed 20 %. It has been shown that partial replacement of naphthoate ligands in the coordination environment of Eu(3+) by NO3(-) anions influences the PL properties. To investigate the behavior of these complexes in solvent, we dissolved complex 3 in MeCN, put it on a transparent glass as a substrate, and studied the PL properties at room temperature. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Structural and photoluminescence properties of Mg substituted ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Mallika, A. N.; Ramachandra Reddy, A.; Sowri Babu, K.; Sujatha, Ch.; Venugopal Reddy, K.

    2014-03-01

    This paper reports on structural and optical properties of Mg doped ZnO nanoparticles prepared through sol-gel method using polyvinyl alcohol as chelating agent. X-ray diffractometer (XRD), Field Emission Scanning Electron Microscope (FE-SEM), UV-Vis (UV-Vis), Fourier Transform Infrared (FTIR) and Photoluminescence (PL) spectrophotometers were employed to study the structural and optical properties. XRD and FE-SEM results demonstrated that particle size of ZnO decreased with increase in Mg concentrations. It was observed that the absorption spectrum of ZnO blue shifted as the Mg concentration enhanced from 1 mol.% to 5 mol.%, presumably due to reduction in particle size. It was found that MgO secondary phase was not formed even above the solid solubility limit of Mg in ZnO. ZnO nanoparticles exhibited an intense and strong UV emission peak at 396 nm and this peak is attributed to the electron transition from the localized level slightly below conduction band to the valence band. The position of this emission peak remained same for all concentrations of Mg in ZnO.

  4. 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.

  5. Photoluminescence properties of anodic aluminum oxide formed in a mixture of ammonium fluoride and oxalic acid

    NASA Astrophysics Data System (ADS)

    Li, Shou-Yi; Wang, Jian; Li, Yan

    2017-06-01

    Highly ordered anodic aluminum oxide (AAO) membranes are fabricated electrochemically in an electrolyte mixture with various concentrations of C2H2O4 or NH4F. Photoluminescence (PL) properties of AAO membranes have been investigated before and after annealing in the range from 300°C to 650°C. X-ray diffraction reveals the amorphous nature of AAO membranes. Energy dispersive spectroscopy indicates the presence of fluorine species incorporated in oxide membranes during the anodizing. PL measurements show a strong PL band in the wavelength range of 350 to 550 nm. With the increase of the concentration of the NH4F or C2H2O4 in the electrolyte mixture, the peak positions of the PL bands have a blueshift or redshift and the intensities have a maximum value. As indicated by the PL excitation spectra, there are two excitation peaks of 285 and 330 nm, which can account for the PL emission band. We have proposed that the PL originates from optical transitions in two kinds of centers that are related to oxygen vacancies, F+ (285 nm) and F (330 nm). This work is not only beneficial to further understanding of the light-emitting property of AAO membranes but also enlarges the application scope.

  6. Photoluminescence and photoconductivity properties of copper-doped Cd1-xZnxS nanoribbons

    NASA Astrophysics Data System (ADS)

    Lui, T. Y.; Zapien, J. A.; Tang, H.; Ma, D. D. D.; Liu, Y. K.; Lee, C. S.; Lee, S. T.; Shi, S. L.; Xu, S. J.

    2006-12-01

    Copper-doped Cd1-xZnxS (x~0.16) nanoribbons were prepared by controlled thermal evaporation of CdS, ZnS, and CuS powders onto Au-coated silicon substrates. The nanoribbons had a hexagonal wurtzite structure, and lengths of several tens to hundreds of micrometres, widths of 0.6-15 µm, and thicknesses of 30-60 nm. Cu doping and incorporation into the CdZnS lattice were identified and characterized by low-temperature photoluminescence (PL) and photoconductivity measurements. Temperature-dependent PL measurement showed that the PL spectra of both Cu-doped and undoped CdZnS nanoribbons have two emission peaks at 2.571 and 2.09 eV, which are assigned to band edge emission and deep trap levels, respectively. In addition, the Cu-doped nanoribbons present two extra peaks at 2.448 and 2.41 eV, which are attributed to delocalized and localized donor and acceptor states in the band gap of CdZnS resulting from Cu incorporation. Photoconductivity results showed the nanoribbons can be reversibly switched between low and high conductivity under pulsed illumination. The Cu-doped CdZnS nanoribbons showed four orders of magnitude larger photocurrent than the undoped ones. The current jumped from ~2 × 10-12 to ~5.7 × 10-7 A upon white light illumination with a power density of ~9 mW cm-2. The present CdZnS:Cu nanoribbons may find applications in opto-electronic devices, such as solar cells, photoconductors, and chemical sensors.

  7. 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.

  8. Highly luminescent lanthanide complexes with novel bis-β-diketone ligand: synthesis, characterization and photoluminescent properties.

    PubMed

    Li, Hong-Feng; Li, Guang-Ming; Chen, Peng; Sun, Wen-Bin; Yan, Peng-Fei

    2012-11-01

    A biphenyl-linked bis-β-diketone ligand, 3,3'-bis(3-phenyl-3-oxopropanol)biphenyl (BPB) has been prepared for the syntheses of a series of dinuclear lanthanide complexes. The ligand bears two benzoyl β-diketonate sites linked by a 3,3'-biphenyl spacer. Reaction of the doubly negatively charged bis-bidenate ligand with lanthanide ions forms triple-stranded dinuclear complexes Ln(2)(BPB)(3) (Ln=Nd (1), Sm (2), Eu (3), Yb (4) and Gd (5)). Electrospray mass spectrometry is used to identify the formation of the triple-stranded dinuclear complexes 1-5, which have been further characterized by various spectroscopic techniques. The complexes display strong visible and NIR luminescence upon excitation at ligands bands around 360 nm, depending on the choice of the lanthanides, and the emission quantum yields and luminescence lifetimes of 2-3 have been determined. It shows that the biphenyl-linked ligand BPB is a more efficient sensitizer than the monodiketone ligand DBM (dibenzoylmethane), through the comparisons of Ln(2)(BPB)(3) and Ln(DBM)(3) on their photoluminescent properties.

  9. 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

  10. Addressing the electronic properties of III-V nanowires by photoluminescence excitation spectroscopy

    NASA Astrophysics Data System (ADS)

    De Luca, M.

    2017-02-01

    Semiconductor nanowires (NWs) have been attracting an increasing interest in the scientific community. This is due to their peculiar filamentary shape and nanoscale diameter, which renders them versatile and cost-effective components of novel technological devices and also makes them an ideal platform for the investigation of a variety of fascinating physical effects. Absorption spectroscopy is a powerful and non-destructive technique able to provide information on the physical properties of the NWs. However, standard absorption spectroscopy is hard to perform in NWs, because of their small volume and the presence of opaque substrates. Here, we demonstrate that absorption can be successfully replaced by photoluminescence excitation (PLE). First, the use of polarization-resolved PLE to address the complex and highly-debated electronic band structure of wurtzite GaAs and InP NWs is shown. Then, PLE is used as a statistically-relevant method to localize the presence of separate wurtzite and zincblende NWs in the same InP sample. Finally, a variety of resonant exotic effects in the density of states of In x Ga1-x As/GaAs core/shell NWs are highlighted by high-resolution PLE. , which features invited work from the best early-career researchers working within the scope of J. Phys. D. This project is part of the Journal of Physics’ series 50th anniversary celebrations in 2017. Marta De Luca was selected by the Editorial Board of J. Phys. D as a Leader.

  11. 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.

  12. 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.

  13. 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.

  14. Photoluminescence properties of silica-based mesoporous materials similar to those of nanoscale silicon

    NASA Astrophysics Data System (ADS)

    Glinka, Yu. D.; Zyubin, A. S.; Mebel, A. M.; Lin, S. H.; Hwang, L. P.; Chen, Y. T.

    Photoluminescence (PL) from composites of 7- and 15-nm sized silica nanoparticles (SNs) and mesoporous silicas (MSs) induced by 266- (4.66-) and 532-nm (2.33-eV) laser light has been studied at room temperature. The multiband PL from MSs in the range of 1.0-2.1 eV is evidenced to originate from isolated bulk and surface non-bridging oxygens (NBOs) and from NBOs combined with variously placed 1-nm sized pore wall oxygen vacancies (OVs). The nature and diversity of NBO light-emitters are confirmed by ab initio calculations. The PL from SNs exhibits only a short wavelength part of the bands (1.5-2.1 eV) originated from isolated bulk and surface NBOs. This fact indicates that the highly OV-bearing structures occur only in extremely thin ( 1 nm) silica layers. The similarity of spectroscopic properties of silica-based nanoscale materials to those of surface-oxidized silicon nanocrystals and porous silicon, containing silica-passivating layers of the same width, is discussed.

  15. Photoluminescence properties of hybrid SiO2-coated CdTe/CdSe quantum dots.

    PubMed

    Liu, Ning; Yang, Ping

    2014-09-01

    Hybrid SiO2-coated CdTe/CdSe quantum dots (QDs) were prepared using CdTe/CdSe QDs prepared by hydrothermal synthesis. A CdSe interlayer made CdTe/CdSe cores with unique type II heterostructures. The hybrid SiO2-coated CdTe/CdSe QDs revealed excellent photoluminescence (PL) properties compared with hybrid SiO2-coated CdTe QDs. Because of the existence of spatial separations of carriers in the type II CdTe/CdSe core/shell QDs, the hybrid QDs had a relatively extended PL lifetime and high stability in phosphate-buffered saline buffer solutions. This is ascribed to the unique components and stable surface state of hybrid SiO2-coated CdTe/CdSe QDs. During the stabilization test in phosphate-buffered saline buffer solutions, both static and dynamic quenching occurred. The quenching mechanism of the hybrid QDs was not suited with the Stern–Volmer equation. However, the relative stable surface of CdTe/CdSe QDs resulted in lower degradation and relative high PL quantum yields compared with hybrid SiO2-coated CdTe QDs. As a result, hybrid SiO2-coated CdTe/CdSe QDs can be used in bioapplications.

  16. Highly luminescent lanthanide complexes with novel bis-β-diketone ligand: Synthesis, characterization and photoluminescent properties

    NASA Astrophysics Data System (ADS)

    Li, Hong-Feng; Li, Guang-Ming; Chen, Peng; Sun, Wen-Bin; Yan, Peng-Fei

    2012-11-01

    A biphenyl-linked bis-β-diketone ligand, 3,3'-bis(3-phenyl-3-oxopropanol)biphenyl (BPB) has been prepared for the syntheses of a series of dinuclear lanthanide complexes. The ligand bears two benzoyl β-diketonate sites linked by a 3,3'-biphenyl spacer. Reaction of the doubly negatively charged bis-bidenate ligand with lanthanide ions forms triple-stranded dinuclear complexes Ln2(BPB)3 (Ln = Nd (1), Sm (2), Eu (3), Yb (4) and Gd (5)). Electrospray mass spectrometry is used to identify the formation of the triple-stranded dinuclear complexes 1-5, which have been further characterized by various spectroscopic techniques. The complexes display strong visible and NIR luminescence upon excitation at ligands bands around 360 nm, depending on the choice of the lanthanides, and the emission quantum yields and luminescence lifetimes of 2-3 have been determined. It shows that the biphenyl-linked ligand BPB is a more efficient sensitizer than the monodiketone ligand DBM (dibenzoylmethane), through the comparisons of Ln2(BPB)3 and Ln(DBM)3 on their photoluminescent properties.

  17. Anticancer, photoluminescence and electrochemical properties of structurally characterized two imine derivatives.

    PubMed

    Ceyhan, Gökhan; Köse, Muhammet; Tümer, Mehmet; Demirtaş, İbrahim

    2015-01-01

    Two imine compounds, 4-[(E)-(2-methoxybenzylidene)amino]phenol (L(1)) and 4-[(E)-(3,4-dimethoxybenzylidene)amino]phenol (L(2)) were synthesized and characterized by the analytical and spectroscopic methods. The electrochemical and photoluminescence properties of the imine compounds L(1) and L(2) were investigated in different solvents. The compounds L(1) and L(2) show different redox processes at some potentials. The molecular structures of two Schiff base compounds are broadly similar, differing principally in the position, the number of methoxy (-OCH3) groups and dihedral angles between aromatic rings. While the compound L(1) has only one methoxy group located on the o-position with respect to the imine bond (C=N), the L(2) contains two methoxy groups on the p-m-positions with respect to the imine bond. The imine compounds show two or three emission bands in the 619-832 nm range in organic solvents. In the 1.0×10(-3) M concentration, the compounds have the highest excitation and emission bands. The imine compounds L(1) and L(2) were screened for their in vitro cytotoxicity on HeLa cell lines using the xCELLigence system (Real Time Cell Analyzer).

  18. 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.

  19. Structural and photoluminescence properties of Al-doped zinc oxide nanoparticles synthesized in polyol

    NASA Astrophysics Data System (ADS)

    Louhichi, Mariem; Romdhane, Samir; Fkiri, Anis; Smiri, Leila Samia; Bouchriha, Habib

    2015-11-01

    Al-doped ZnO (AZO) nanoparticles have been prepared using a modified polyol process that makes use of di-ethylene glycol as a solvent. This procedure allows for obtaining nanoparticles with a narrowed size distribution, a controlled morphology and a high crystal quality. The prepared AZO nanoparticles were annealed at 400 °C. We studied the effect of doping and annealing on structural and optical properties. The structural investigations of the products confirmed the hexagonal wurtzite structure for all products and having a most preferred orientation along (1 0 1) plane. The results obtained by TEM revealed that the average particle size of the products decreases by doping and increases by annealing temperature. Energy dispersive spectroscopy (EDS) confirms the substitution of Al into ZnO lattice. Raman scattering analysis shows that the crystallinity of the material was improved by increasing the concentration of the dopant Al3+ and the photoluminescence spectra shows that the UV emission peak position of AZO nanoparticles exhibited a slight blue shift from 384 to 383 nm, and the intensity decreased with increasing the Al concentration, which is attributed to an increase in nonradiative recombination. However the UV emission peak position of AZO (0.2% and 0.6%) nanoparticles annealed at 400 °C exhibited a slight red shift due to the influence of the size effect on the energy level of confined excitons, because of the average size of the nanoparticles obviously became bigger with the increase of annealing temperature.

  20. 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.

  1. 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.

  2. Structure, optical and photoluminescence properties of LiGd1-xErx(WO4)2 green luminescence phosphor

    NASA Astrophysics Data System (ADS)

    Demiaï, A.; Derbal, M.; Guerbous, L.; Rekik, B.

    2017-03-01

    Double tungstate of lithium and trivalent gadolinium ions were prepared by mean of solid state reaction, and have been studied using X-ray diffraction, Raman scattering and photoluminescence analysis. The Er3+ concentration effects on the structural and optical properties were studied. The compounds crystallize in the scheelite like structure with space group I41/a, and Z = 2. Spectroscopic and structural properties of the Er3+ ions doping elements in LiGd(WO4)2 have been determined at room temperature. Steady and time resolved photoluminescence spectroscopies of the synthesized compounds are reported. Samples exhibit intense green emission of Er3+ (4S3/2 → 4I15/2 and 2H11/2 → 4I15/2 transitions) under 377 nm excitation wavelength and present luminescent quenching around 3 at% Er3+ concentration. The decay time decrease with increasing the Er3+ concentration.

  3. 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. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  4. Programmable Colloidal Approach to Hierarchical Structures of Methylammonium Lead Bromide Perovskite Nanocrystals with Bright Photoluminescent Properties

    DOE PAGES

    Teunis, Meghan B.; Johnson, Merrell A.; Muhoberac, Barry B.; ...

    2017-04-05

    Here, systematic tailoring of nanocrystal architecture could provide unprecedented control over their electronic, photophysical, and charge transport properties for a variety of applications. However, at present, manipulation of the shape of perovskite nanocrystals is done mostly by trial-and-error-based experimental approaches. Here, we report systematic colloidal synthetic strategies to prepare methylammonium lead bromide quantum platelets and quantum cubes. In order to control the nucleation and growth processes of these nano crystals, we appropriately manipulate the solvent system, surface ligand chemistry, and reaction temperature causing syntheses into anisotropic shapes. We demonstrate that both the presence of chlorinated solvent and a long chainmore » aliphatic amine in the reaction mixture are crucial for the formation of ultrathin quantum platelets (similar to 1.5 nm in thickness), which is driven by mesoscale-assisted growth of spherical seed nanocrystals (similar to 1.6 nm in diameter) through attachment of monomers onto selective crystal facets. A combined surface and structural characterization, along with small-angle X-ray scattering analysis, confirm that the long hydrocarbon of the aliphatic amine is responsible for the well ordered hierarchical stacking of the quantum platelets of 3.5 nm separation. In contrast, the formation of similar to 12 nm edge-length quantum cubes is a kinetically driven process in which a high flux of monomers is achieved by supplying thermal energy. The photoluminescence quantum yield of our quantum platelets (similar to 52%) is nearly 2-fold higher than quantum cubes. Moreover, the quantum platelets display a lower nonradiative rate constant than that found with quantum cubes, which suggests less surface trap states. Together, our research has the potential both to improve the design of synthetic methods for programmable control of shape and assembly and to provide insight into optoelectronic properties of these

  5. 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.

  6. 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.

  7. Band gap engineering and optical properties of tungsten trioxide

    NASA Astrophysics Data System (ADS)

    Ping, Yuan; Li, Yan; Rocca, Dario; Gygi, Francois; Galli, Giulia

    2012-02-01

    Tungsten trioxide (WO3) is a good photoanode material for water oxidation but it is not an efficient absorber of sunlight because of its large band gap (2.6 eV). Recently, stable clathrates of WO3 with interstitial N2 molecules were synthesized [1], which are isostructural to monoclinic WO3 but have a substantially smaller bang gap, 1.8 eV. We have studied the structural, electronic, an vibrational properties of N2-WO3 clathrates using ab-initio calculations and analyzed the physical origin of their gap reduction. We also studied the effect of atomic dopants, in particular rare gases. Substantial band gap reduction has been observed, especially in the case of doping with Xe, due to both electronic and structural effects. Absorption spectra have been computed by solving the Bethe-Salpeter Equation [2] to gain a thourough insight into the optical properties of pure and doped tungsten trioxide. [1] Q. Mi, Y. Ping, Y. Li., B.S. Brunschwig, G. Galli, H B. Gray, N S. Lewis (preprint) [2]D. Rocca, D. Lu and G. Galli, J. Chem. Phys. 133, 164109 (2010)

  8. 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.

    2016-11-01

    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.

  9. 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.

  10. 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.

  11. Polarization properties of surface plasmon enhanced photoluminescence from a single Ag nanowire.

    PubMed

    Song, Min; Chen, Gengxu; Liu, Yan; Wu, E; Wu, Botao; Zeng, Heping

    2012-09-24

    Metallic nanowires are of great research interest due to their applications in surface plasmon polariton coupling of light. The efficiency is much dependent on the polarization of the light due to the phase matching requirement in the light-surface plasmon polariton coupling. By scanning confocal microscope, the photoluminescence from a single Ag nanowire was demonstrated strongly dependent on the excitation laser polarization, showing good consistency with the theoretical simulation. Meanwhile strong avalanche photoluminescence from a single Ag nanowire was observed when the excitation laser was polarized along the long axis of the Ag nanowire. The photoluminescence emission exhibited a polarization-sensitive spatial distribution. This may stimulate promising applications in designing polarization-controllable nanoscale plasmonic devices.

  12. Optical and electronic properties of some semiconductors from energy gaps

    NASA Astrophysics Data System (ADS)

    Tripathy, Sunil K.; Pattanaik, Anup

    2016-03-01

    II-VI and III-V tetrahedral semiconductors have significant potential for novel optoelectronic applications. In the present work, some of the optical and electronic properties of these groups of semiconductors have been studied using a recently proposed empirical relationship for refractive index from energy gap. The calculated values of these properties are also compared with those calculated from some well known relationships. From an analysis of the calculated electronic polarisability of these tetrahedral binary semiconductors from different formulations, we have proposed an empirical relation for its calculation. The predicted values of electronic polarisability of these semiconductors agree fairly well with the known values over a wide range of energy gap. The proposed empirical relation has also been used to calculate the electronic polarisability of some ternary compounds.

  13. A New Star-shaped Carbazole Derivative with Polyhedral Oligomeric Silsesquioxane Core: Crystal Structure and Unique Photoluminescence Property.

    PubMed

    Xu, Zixuan; Yu, Tianzhi; Zhao, Yuling; Zhang, Hui; Zhao, Guoyun; Li, Jianfeng; Chai, Lanqin

    2016-01-01

    A new inorganic–organic hybrid material based on polyhedral oligomeric silsesquioxane (POSS) capped with carbazolyl substituents, octakis[3-(carbazol-9-yl)propyldimethylsiloxy]-silsesquioxane (POSS-8Cz), was successfully synthesized and characterized. The X-ray crystal structure of POSS-8Cz were described. The photophysical properties of POSS-8Cz were investigated by using UV–vis,photoluminescence spectroscopic analysis. The hybrid material exhibits blue emission in the solution and the solid film.The morphology and thermal stablity properties were measured by X-ray diffraction (XRD) and TG-DTA analysis.

  14. 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.

  15. 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.

  16. Crystal growth and photoluminescence properties of Sm3+ doped CeO2 nanophosphors by solvothermal method.

    PubMed

    Yang, Hyun Kyoung; Moon, Byung Kee; Choi, Byung Chun; Jeong, Jung Hyun; Kim, Kwang Ho

    2013-09-01

    The phosphor of CeO2 activated with the trivalent rare-earth Sm3+ ions were synthesized by using a solvothermal method. The CeO2:Sm3+ powders were finally obtained through calcination process sintered in the air at 800-1200 degrees C. The synthesized phosphors were characterized systematically by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence (PL) and photoluminescence excitation spectra (PLE). The XRD and FE-SEM results reveal that the phosphor exhibit agglomerated spherical shape and with the increase of sintering temperature peaks become sharper and narrower and the crystal sizes also increase, respectively. The room temperature photoluminescence spectra of Sm3+ doped CeO2 powders were recorded on a PTI (Photon Technology International) flurimeter using a Xe-arc lamp with a power of 60 W. The emitted radiation was dominated by the orange light with the characteristic emission of Sm3+ from the transitions of 4G5/2 --> 6H5/2,7/2. The sharp emission properties show that the CeO2 has the potential to serve as a host material for rare-earth doped laser crystal and phosphor material.

  17. Structural and optical properties of Er implanted AlN thin films: Green and infrared photoluminescence at room temperature

    NASA Astrophysics Data System (ADS)

    Soares, M. J.; Leitão, J. P.; da Silva, M. I. N.; González, J. C.; Matinaga, F. M.; Lorenz, K.; Alves, E.; Peres, M.; Monteiro, T.

    2011-05-01

    In this work erbium ions were implanted into AlN films grown on sapphire with fluence range: (0.5-2) × 10 15 at/cm -2, ion energy range: 150-350 keV and tilt angle: 0°, 10°, 20°, 30°. The optical and structural properties of the films are studied by means of photoluminescence and Raman spectroscopy in combination with Rutherford backscattering/channeling (RBS/C) measurements. The photoluminescence spectra of the Er 3+ were recorded in the visible and infrared region between 9 and 300 K after thermal annealing treatments of the samples. The emission spectrum of the AlN:Er films consists of two series of green lines centered at 538 and 558 nm with typical Er 3+ emission in the infrared at 1.54 μm. The green lines have been identified as Er 3+ transitions from the 2H 11/2 and 4S 3/2 levels to the 4I 15/2 ground state. Different erbium centers in the matrix are suggested by the change of infrared photoluminescence relative intensity of some of the emission lines when different excitation wavelengths are used. The relative abundances of these centers can be varied by using different implantation parameters. The Raman and RBS/C measurements show good crystalline quality for all the studied films.

  18. Magneto-thermodynamic properties of gapped graphene-like structures

    NASA Astrophysics Data System (ADS)

    Yarmohammadi, Mohsen; Beig-Mohammadi, Maryam; Shirzadi, Bahram

    2017-06-01

    By applying the Green's function technique and using the tight-binding Hamiltonian model, thermodynamic properties of gapped graphene-like structures, including silicon carbide (SiC), boron nitride (BN) and beryllium monooxide (BeO) in the presence of a transverse magnetic field are investigated. In fact, we have studied electronic density of states (DOS), electronic heat capacity (EHC) and magnetic susceptibility (MS) in order to investigate the dynamics of Dirac fermions. At an applied certain value of magnetic field, the band gap width increases for SiC, BN and BeO structures with respect to the gapless graphene and a double peak appears in DOS with increasing of quantum states. On the other hand, the band gap size decreases with magnetic field. We have found that EHC and MS increase slightly at low temperatures with gap and magnetic field. Also, EHC and MS reach to their maximum value at a critical temperature point while an increase behavior has been observed for high temperatures significantly.

  19. Magneto-thermodynamic properties of gapped graphene-like structures

    NASA Astrophysics Data System (ADS)

    Yarmohammadi, Mohsen; Beig-Mohammadi, Maryam; Shirzadi, Bahram

    2017-02-01

    By applying the Green's function technique and using the tight-binding Hamiltonian model, thermodynamic properties of gapped graphene-like structures, including silicon carbide (SiC), boron nitride (BN) and beryllium monooxide (BeO) in the presence of a transverse magnetic field are investigated. In fact, we have studied electronic density of states (DOS), electronic heat capacity (EHC) and magnetic susceptibility (MS) in order to investigate the dynamics of Dirac fermions. At an applied certain value of magnetic field, the band gap width increases for SiC, BN and BeO structures with respect to the gapless graphene and a double peak appears in DOS with increasing of quantum states. On the other hand, the band gap size decreases with magnetic field. We have found that EHC and MS increase slightly at low temperatures with gap and magnetic field. Also, EHC and MS reach to their maximum value at a critical temperature point while an increase behavior has been observed for high temperatures significantly.

  20. 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.

  1. Negative thermal expansion and photoluminescence properties in a novel material ZrScW2PO12

    NASA Astrophysics Data System (ADS)

    Ge, Xianghong; Liu, Xiansheng; Cheng, Yongguang; Yuan, Baohe; Chen, Dongxia; Chao, Mingju; Guo, Juan; Wang, Junqiao; Liang, Erjun

    2016-11-01

    A novel material, ZrScW2PO12, with negative thermal expansion (NTE) behavior, at least from 138 to 1300 K, and intense photoluminescence (PL) property is first reported in this paper. Temperature dependent Raman and PL spectral studies indicate that the material holds an orthorhombic structure down to about 74 K and exhibits NTE property in the temperature range. The intense PL covering nearly the whole visible region was observed and can be deconvoluted into four bands, which present different shifts with elevation of temperature. The abundant optical property may be attributed to n- and p-type like co-doping effect and the specific structure with the abnormal thermal expansion property of the material. The integrated properties might suggest potential applications of this material in light emitting diodes and other light emitting devices.

  2. 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.

  3. Optical properties of type-II AlInAs/AlGaAs quantum dots by photoluminescence studies

    SciTech Connect

    Saïdi, I.; Neffati, R.; Ben Radhia, S.; Boujdaria, K.; Lemaître, A.; Bernardot, F.; Testelin, C.

    2016-07-21

    We report photoluminescence (PL) characterization and model simulation of AlInAs/AlGaAs type-II quantum dots (QDs). A thorough and precise determination of the band parameters for QD and matrix materials is given, focusing on the effects of alloy composition and strain state on the electronic properties. Origins of experimentally observed PL emission peaks are identified through a comparison with the band lineup theoretically determined in this work. We interpret the QD emission as originating from indirect type-II transitions involving electrons in the barrier X valley and heavy holes with S and P symmetry.

  4. 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.

  5. 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.

  6. 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.

  7. Strong Photoluminescence and Improved Electrical Properties in Eu-Modified SrBi4Ti4O15 Multifunctional Ceramics

    NASA Astrophysics Data System (ADS)

    Yu, Lei; Hao, Jigong; Xu, Zhijun; Li, Wei; Chu, Ruiqing

    2017-03-01

    A red-emitting piezoelectric ceramic of SrBi4-x Eu x Ti4O15 (SBT-xEu, x = 0.000-0.010) with strong photoluminescence and improved piezoelectric properties was prepared. All samples had a bismuth oxide layered structure with a dense microstructure. After Eu3+ doping, a bright red photoluminescence upon blue light excitation of the 400 nm to 500 nm was observed in the modified samples. Upon the excitation of 465 nm light, the emission peaks centered at 537-703 nm were noted, which correspond to a weak green 5D1 → 7F1 transition and the characteristic emission bands (5D0 → 7F J , J = 1-4). Simultaneously, Eu3+ doping promotes electrical properties. At 0.6 mol.% Eu, samples exhibit the optimal electric properties (d 33 = 22 pC/N, 2P r = 19.86 μC/cm2 and T c = 534°C), together with excellent temperature stability (25-450°C). As a multifunctional material, Eu-doped SBT ferroelectric oxide showed great potential in sensors and optical-electro integration device applications.

  8. Strong Photoluminescence and Improved Electrical Properties in Eu-Modified SrBi4Ti4O15 Multifunctional Ceramics

    NASA Astrophysics Data System (ADS)

    Yu, Lei; Hao, Jigong; Xu, Zhijun; Li, Wei; Chu, Ruiqing

    2017-07-01

    A red-emitting piezoelectric ceramic of SrBi4- x Eu x Ti4O15 (SBT- xEu, x = 0.000-0.010) with strong photoluminescence and improved piezoelectric properties was prepared. All samples had a bismuth oxide layered structure with a dense microstructure. After Eu3+ doping, a bright red photoluminescence upon blue light excitation of the 400 nm to 500 nm was observed in the modified samples. Upon the excitation of 465 nm light, the emission peaks centered at 537-703 nm were noted, which correspond to a weak green 5D1 → 7F1 transition and the characteristic emission bands (5D0 → 7F J , J = 1-4). Simultaneously, Eu3+ doping promotes electrical properties. At 0.6 mol.% Eu, samples exhibit the optimal electric properties ( d 33 = 22 pC/N, 2 P r = 19.86 μC/cm2 and T c = 534°C), together with excellent temperature stability (25-450°C). As a multifunctional material, Eu-doped SBT ferroelectric oxide showed great potential in sensors and optical-electro integration device applications.

  9. Temperature dependent photoluminescence properties of InAs/InP quantum dashes subjected to low energy phosphorous ion implantation and subsequent annealing.

    PubMed

    Alouane, M H Hadj; Ilahi, B; Maaref, H; Salem, B; Aimez, V; Morris, D; Gendry, M

    2011-10-01

    We report on the impact of phosphorous ion-implantation-induced band gap tuning on the temperature dependent photoluminescence (PL) properties of InAs/InP quantum dashes (QDas). The high temperature range carriers' activation energy, extracted from Arrhenius plots, is found to decrease from 238 to 42 meV when the ion implantation dose increases from 10(11) cm(-2) to 5 x 10(14) cm(-2) which is consistent with the observed emission energy blueshift increase with increasing the ion implantation doses. This effect is attributed to the As/P exchange which reduces the carrier confining potential depth. For intermediate ion implantation doses the reduced carrier confining potential barrier combined with the non-uniform intermixing process, that causes an increased QDas size dispersion, result in anomalous temperature-dependent PL properties. Indeed, the temperature induced PL emission energy redshift measured between 10 K and 300 K is found to be strongly affected by the carrier redistribution within the broadened localized QDas states.

  10. 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.

  11. Photovoltaic properties of low band gap ferroelectric perovskite oxides

    NASA Astrophysics Data System (ADS)

    Huang, Xin; Paudel, Tula; Dong, Shuai; Tsymbal, Evgeny

    2015-03-01

    Low band gap ferroelectric perovskite oxides are promising for photovoltaic applications due to their high absorption in the visible optical spectrum and a possibility of having large open circuit voltage. Additionally, an intrinsic electric field present in these materials provides a bias for electron-hole separation without requiring p-n junctions as in conventional solar cells. High quality thin films of these compounds can be grown with atomic layer precision allowing control over surface and defect properties. Initial screening based on the electronic band gap and the energy dependent absorption coefficient calculated within density functional theory shows that hexagonal rare-earth manganites and ferrites are promising as photovoltaic absorbers. As a model, we consider hexagonal TbMnO3. This compound has almost ideal band gap of about 1.4 eV, very high ferroelectric Curie temperature, and can be grown epitaxially. Additionally hexagonal TbMnO3 offers possibility of coherent structure with transparent conductor ZnO. We find that the absorption is sufficiently high and dominated by interband transitions between the Mn d-bands. We will present the theoretically calculated photovoltaic efficiency of hexagonal TbMnO3 and explore other ferroelectric perovskite oxides.

  12. 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.

  13. 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.

  14. Strong visible and near infrared photoluminescence from ZnO nanorods/nanowires grown on single layer graphene studied using sub-band gap excitation

    NASA Astrophysics Data System (ADS)

    Biroju, Ravi K.; Giri, P. K.

    2017-07-01

    Fabrication and optoelectronic applications of graphene based hybrid 2D-1D semiconductor nanostructures have gained tremendous research interest in recent times. Herein, we present a systematic study on the origin and evolution of strong broad band visible and near infrared (NIR) photoluminescence (PL) from vertical ZnO nanorods (NRs) and nanowires (NWs) grown on single layer graphene using both above band gap and sub-band gap optical excitations. High resolution field emission scanning electron microscopy and X-ray diffraction studies are carried out to reveal the morphology and crystalline quality of as-grown and annealed ZnO NRs/NWs on graphene. Room temperature PL studies reveal that besides the UV and visible PL bands, a new near-infrared (NIR) PL emission band appears in the range between 815 nm and 886 nm (1.40-1.52 eV). X-ray photoelectron spectroscopy studies revealed excess oxygen content and unreacted metallic Zn in the as-grown ZnO nanostructures, owing to the low temperature growth by a physical vapor deposition method. Post-growth annealing at 700 °C in the Ar gas ambient results in the enhanced intensity of both visible and NIR PL bands. On the other hand, subsequent high vacuum annealing at 700 °C results in a drastic reduction in the visible PL band and complete suppression of the NIR PL band. PL decay dynamics of green emission in Ar annealed samples show tri-exponential decay on the nanosecond timescale including a very slow decay component (time constant ˜604.5 ns). Based on these results, the NIR PL band comprising two peaks centered at ˜820 nm and ˜860 nm is tentatively assigned to neutral and negatively charged oxygen interstitial (Oi) defects in ZnO, detected experimentally for the first time. The evidence for oxygen induced trap states on the ZnO NW surface is further substantiated by the slow photocurrent response of graphene-ZnO NRs/NWs. These results are important for tunable light emission, photodetection, and other cutting edge

  15. 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.

  16. 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.

  17. Photoluminescence and dielectric properties of pure/Yb-doped SrZrO3 crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Lulu; Wang, Jilin; Peng, Daijiang; Long, Fei; Mo, Shuyi; Wu, Yi; Zou, Zhengguang

    2017-05-01

    High quality SrZrO3 nanocubes have been successfully synthesized via a facile hydrothermal method using Sr(NO3)2 and Zr(NO3)4·5H2O as raw materials. Then, the Yb-doped SrZrO3 were also fabricated by solid state reaction using the as-synthesized pure SrZrO3. The phase structure, morphology, composition and specific surface area of the samples were investigated by XRD, FESEM, EDS, TEM, FTIR, Raman and BET techniques. The as-synthesized SrZrO3 nanocubes distributed homogeneously and displayed sharp edges with an average particle size of about 100 nm. In addition, the dielectric loss value of the pure SrZrO3 at 1 MHz was only 0.05 when the temperature rose from 25 °C to 550 °C, indicating a good dielectric property at high temperature. Meanwhile, the band gap of SrZrO3 could be reduced by about 0.3 eV after Yb3+ doping, where Yb3+ mainly occupied Sr2+ position (A site doping). Besides, all of the pure and Yb-doped SrZrO3 samples exhibit violet light emission centered at 423 nm (excited at 372 nm), which was originated from material intrinsic defects.

  18. Synthesis and photoluminescent properties of SnO-containing germanate and germanosilicate glasses

    NASA Astrophysics Data System (ADS)

    Chernov, A. I.; Denker, B. I.; Ermakov, R. P.; Galagan, B. I.; Iskhakova, L. D.; Sverchkov, S. E.; Velmiskin, V. V.; Dianov, E. M.

    2016-09-01

    Divalent tin-containing germanate glasses have demonstrated wide photoluminescence similar to that of tin silicate glasses discovered recently. In comparison with silicate glasses, the germanate glasses are characterized by longer emission lifetimes (145 ÷ 440 µs), emission peaking at 1.59 ÷ 1.64 µm and the absence of SnO disproportionation into SnO2 and Sn during glass synthesis. The potential fabrication of optical fiber via the SnC2O4 + GeO2 powder in silica tube method was demonstrated.

  19. Synthesis, structure and photoluminescence properties of Sm{sup 3+}-doped BiOBr phosphor

    SciTech Connect

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

    2016-05-23

    Well-crystallized tetragonal layered BiOBr and Bi{sub 0.95}Sm{sub 0.05}OBr 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 Sm{sup 3+} 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.

  20. Shape controlled synthesis of CaMoO 4 thin films and their photoluminescence property

    NASA Astrophysics Data System (ADS)

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

    2008-05-01

    CaMoO 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.

  1. Rapid microwave synthesis and photoluminescence properties of rare earth-based coordination polymer core-shell particles

    NASA Astrophysics Data System (ADS)

    Huang, Shuang; Xu, Hualan; Wang, Mengya; Zhong, Shengliang; Zeng, Chenghui

    2016-12-01

    Coordination polymer (CP) core-shell particles, with Eu-based CP as the core and La-based CP as the shell, were prepared using a facile microwave heating method. Pyridine-2, 5-dicarboxylic acid (PDA) was selected as the organic building blo, and DMF was used as the solvent. SEM and TEM images show that the resultant cores are nanospheres with diameters of 200-400 nm. Products with different shell thickness were prepared. The luminescence properties of the core-shell structures were studied and the influence of the La-based CP shell on the photoluminescence properties of the core were investigated. The fluorescence intensity and lifetime of the Eu-based CP core were varied with the addition of shell thickness. Both of them increases at first and then decreases with the increase of shell thickness.

  2. Stimuli-responsive photoluminescent liquid crystals.

    PubMed

    Yamane, Shogo; Tanabe, Kana; Sagara, Yoshimitsu; Kato, Takashi

    2012-01-01

    We describe mechanochromic and thermochromic photoluminescent liquid crystals. In particular, mechanochromic photoluminescent liquid crystals found recently, which are new stimuli-responsive materials are reported. For example, photoluminescent liquid crystals having bulky dendritic moieties with long alkyl chains change their photoluminescent colors by mechanical stimuli associated with isothermal phase transitions. The photoluminescent properties of molecular assemblies depend on their assembled structures. Therefore, controlling the structures of molecular assemblies with external stimuli leads to the development of stimuli-responsive luminescent materials. Mechanochromic photoluminescent properties are also observed for a photoluminescent metallomesogen and a liquid-crystalline polymer. We also show thermochromic photoluminescent liquid crystals based on origo-(p-phenylenevinylene) and anthracene moieties and a thermochromic photoluminescent metallocomplex.

  3. Effects of extraction solvents on photoluminescent properties of eysenhardtia polystachia and their potential usage as biomarker.

    PubMed

    Ferreira-García, M G; Hernandez-Martinez, A R; Esparza, R; Molina, G A; Rodriguez-Melgarejo, F; Jiménez, S; Estevez, M

    2017-03-01

    Currently, nanomaterials had been used for several applications; one of them is as bio-markers. These nanomaterials contain fluorescent compounds as effective indicators for imaging and other applications in Biotechnology. In previous studies, we proposed a functionalized nanomaterial-based biomarker from silica and Eysenhardtia Polystachia, a medicinal tree known in Mexico as "palo azul" (Kidneywood). Our previous results showed the feasibility of the nanomaterial obtained as bio-marker. In this article, our purpose is to evaluate the effects of extraction solvents on fluorescence of that biomarker. The photoluminescence (PL) effect was evaluated at different pH (4, 7.4 and 8); four extraction solvents, ethanol, methanol, methanol-ethanol and methanol-ethanol-water were evaluated. A molecular dynamics simulation was performed to recognize molecular interaction between the compounds of the extracts with solvent molecules and to investigate the solvent molecules effect on photoluminescence spectra. The results were also compared with rhodamine 6G and we found that, at physiological pH (7.4), the fluorescent-coated silica nanoparticles obtained were also stable. We found that extraction solvents could be used for obtaining different nanomaterials for specific applications, and also found the best extraction solvent for obtaining EP nanomaterials for health care applications, specifically for imaging techniques. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. 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.

  5. Photoluminescence properties of Ho3+/Tm3+-doped YAGG nano-crystalline powders

    NASA Astrophysics Data System (ADS)

    Praveena, R.; Sameera, V. Sravani; Babu, P.; Basavapoornima, Ch.; Jayasankar, C. K.

    2017-10-01

    Y3Al4GaO12 (YAGG):(Tm3+, Ho3+) nanoparticles have been synthesized by Pechini sol-gel method and characterised their X-ray diffraction patterns, scanning electron microscope image, energy dispersive and photoluminescence spectra. From XRD results, phase purity and structure have been confirmed. Excitation spectra reveal that 363 nm excitation is suitable to excite the co-doped samples. Under ultraviolet excitation at 363 nm, the characteristic emissions of Tm3+ and Ho3+ ions have been observed in the photoluminescence (PL) spectra. Concentration dependent luminescence and energy transfer between Tm3+ and Ho3+ ions have been studied. The CIE chromaticity coordinates and correlated colour temperature values have been obtained from the emission spectra. Moreover, the emission colour of the YAGG:TmHo nano-powders was slightly shifted to red colour while increasing the Ho concentration and can be tuned from blue/green to white by adjusting the Tm3+/Ho3+ ions concentration. The optimum concentration of Tm3+ and Ho3+ ions were found to be 1:1 ratio in the YAGG host. The optimized single component white light emitting YAGG:TmHo phosphors could be a potential candidate for phosphor-converted white light emitting diode and full colour display applications.

  6. Photoluminescence properties of lead selenide produced by selenization and a solvothermal method.

    PubMed

    Kim, Jungdong; Ahn, Hak-Young; Kim, Seung Gi; Oh, Eunsoon; Ju, Byeong-Kwon; Choi, Won Jun; Cho, So-Hye

    2017-01-06

    We studied temperature-dependent photoluminescence (PL) spectra of lead selenide (PbSe) dendrites and cubes grown by a solvothermal method. Their PL peaks were located at ∼8 μm at 10 K with a full width at half maximum (FWHM) of 10 meV. Using the temperature-dependent FWHM values, we obtained carrier-phonon coupling coefficients for PbSe. We also demonstrated mechanochemical synthesis of polycrystalline PbS nanoparticles and their successful conversion into a PbSe layer composed of nanocrystals by a selenization process with thermal treatment. The nanocrystals were found to be formed by the orientation alignment of small grains in the process. The PL peak energies of the PbSe layers as well as the PbSe dendrites and the cubes agreed well with their absorption edges in the transmission spectra, indicating that the photoluminescence originates from the band-edge emission. The band-edge emissions hold promise for the development of potential mid-infrared light sources using PbSe fabricated by these methods.

  7. Photoluminescence properties of lead selenide produced by selenization and a solvothermal method

    NASA Astrophysics Data System (ADS)

    Kim, Jungdong; Ahn, Hak-Young; Kim, Seung Gi; Oh, Eunsoon; Ju, Byeong-Kwon; Choi, Won Jun; Cho, So-Hye

    2017-01-01

    We studied temperature-dependent photoluminescence (PL) spectra of lead selenide (PbSe) dendrites and cubes grown by a solvothermal method. Their PL peaks were located at ˜8 μm at 10 K with a full width at half maximum (FWHM) of 10 meV. Using the temperature-dependent FWHM values, we obtained carrier-phonon coupling coefficients for PbSe. We also demonstrated mechanochemical synthesis of polycrystalline PbS nanoparticles and their successful conversion into a PbSe layer composed of nanocrystals by a selenization process with thermal treatment. The nanocrystals were found to be formed by the orientation alignment of small grains in the process. The PL peak energies of the PbSe layers as well as the PbSe dendrites and the cubes agreed well with their absorption edges in the transmission spectra, indicating that the photoluminescence originates from the band-edge emission. The band-edge emissions hold promise for the development of potential mid-infrared light sources using PbSe fabricated by these methods.

  8. 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.

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

    SciTech Connect

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

    2016-07-04

    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.

  10. Photoluminescence properties and energy transfer in color tunable BaY2Si3O10:Ce,Tb phosphors

    NASA Astrophysics Data System (ADS)

    Xia, Zhanggen; Liang, Yujun; Yu, Dongyan; Zhang, Mengfei; Huang, Wenzhu; Tong, Miaohui; Wu, Jiamin; Zhao, Jianwen

    2014-03-01

    A series of novel color tunable phosphors BaY2Si3O10:Ce3+,Tb3+ have been synthesized by the solid-state reaction. The crystalline structure, photoluminescence properties, lifetimes and luminous efficiency were characterized using X-ray diffraction (XRD), photoluminescence spectroscopy and quantum yield measurement system. The decay mode of Ce3+ confirms that the energy transfer occurred in BaY2Si3O10:Ce3+,Tb3+ phosphors, and the intense green emission is realized in BaY1.10Si3O10:0.05Ce3+,0.85Tb3+ on the base of high efficient energy transfer from Ce3+ to Tb3+ with an efficiency of 70%. The quantum yield of BaY1.10Si3O10:0.05Ce3+,0.85Tb3+ is 81.6%. The CIE coordinates are tuned from deep blue (0.156, 0.098) to green (0.294, 0.562) by adjusting the concentration of Tb3+. Those results indicate that the BaY2Si3O10:Ce3+,Tb3+ phosphors would be a promising candidate as an ultraviolet convertible phosphor for light emitting devices due to its efficient green emission.

  11. Effect of Rochelle salt on growth, optical, photoluminescence, photoconductive and piezoelectric properties of the triglycine sulphate single crystal

    NASA Astrophysics Data System (ADS)

    Rajesh, P.; Rao, G. Babu; Ramasamy, P.

    2017-06-01

    Triglycine sulphate (TGS) is well-known ferroelectric crystal, finding many applications in IR detectors and laser devices. Triglycine sulphate crystal was grown by conventional method using water as a solvent. The 1 mol% of semiorganic piezoelectric material Rochelle salt (RS) is added into the pure TGS to enhance its optical, photoluminescence and piezoelectric properties. The crystallinity of the grown crystals was examined by powder X-ray diffraction analysis. Optical transmittance shows that the RS doped TGS possesses higher transparency compared to pure TGS. High intense luminescence at 442 nm for the RS doped TGS single crystal is observed from the photoluminescence study. The negative photoconductivity nature is observed for both pure and RS doped TGS and it was studied under different conditions such as dark, light and also under different temperatures such as at Curie temperature, above and below Curie temperature. Low dislocation density for RS doped TGS crystal is observed from chemical etching analysis. The piezoelectric d33 co-efficient is also increased as a result of RS doping in TGS.

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

    SciTech Connect

    Singh, Narendra; Kaur, Davinder

    2016-05-06

    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.

  13. The effect of two additional Eu3+ lumophors in two novel trinuclear europium complexes on their photoluminescent properties.

    PubMed

    Yang, Chaolong; Xu, Jing; Ma, Jianying; Zhu, Dongyu; Zhang, Yunfei; Liang, Liyan; Lu, Mangeng

    2013-02-01

    Two novel trinuclear europium complexes based on trisphen(1,3,5-tris{4-((1,10-phenanthroline-[5,6-d]imidazol-2yl)phenoxy)methyl}-2,4,6-trimethyl-benzene) as a second ligand were designed, synthesized, and characterized by FT-IR, (1)H NMR, UV-visible, photoluminescence (PL) spectroscopy, elemental analysis (EA) and ESI-MS. The geometries of these two trinuclear europium complexes were predicted using the Sparkle/PM3 model and suggested a chemical environment of very low symmetry around the lanthanide ions (C(1)), which is in agreement with the luminescent spectra. CV analysis demonstrated that the trinuclear complexes possessed excellent electro-injection abilities. The effects of two additional Eu(3+) lumophors in these trinuclear europium complexes on their photoluminescent properties were investigated in detail. The results indicated that these trinuclear europium complexes exhibited highly luminescent quantum efficiencies and experimental intensity parameters in the solid state. Especially, due to the contribution of the two additional Eu(3+) lumophors in the trinuclear europium complexes, the quantum efficiency of the trinuclear complex Eu(3)(TTA)(9)trisphen was higher (ca. 34%) than the mononuclear europium complex Eu(TTA)(3)imidazophen.

  14. Bioconjugations of polyethylenimine-capped LaF3:Ce, Tb nanoparticles with bovine serum albumin and photoluminescent properties.

    PubMed

    Zhang, Wei; Hua, Ruinian; Shao, Wanyue; Zhao, Jun; Na, Liyan

    2014-05-01

    Water-soluble Ce3+ and Tb3+ co-doped LaF3 nanoparticles with surfaces functionalized by a layer of polyethylenimine (PEI) were synthesized via a facile one-step hydrothermal method. Bovine serum albumin (BSA) protein was conjugated with LaF3:Ce, Tb nanoparticles via free amino groups on the surfaces of the nanocrystals. The final products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), ultraviolet (UV) spectrophotometry, and photoluminescence (PL) spectroscopy. XRD results showed that pure hexagonal phase LaF3:Ce, Tb nanoparticles could be obtained via a PEI assisted hydrothermal process at 180 degrees C for 24 h. The FE-SEM results showed that the morphology of pure LaF3:Ce, Tb nanoparticles was spherical with an average diameter of -20 nm. The UV spectra showed that BSA had been conjugated with LaF3:Ce, Tb nanoparticles. The photoluminescent (PL) properties of LaF3:Ce, Tb nanoparticles were also studied. The strong green emission of Tb3+ in LaF3:Ce, Tb nanoparticles suggests that these nanoparticles may have potential applications for labels in biological imaging and immunoassays.

  15. 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

  16. 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

  17. 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.

  18. Fabrication of Bi-doped In2O3-ITO nanocomposites and their photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Gil Na, Han; Jung, Taek-Kyun; Lee, Ji-Woon; Hyun, Soong-Keun; Kwon, Yong Jung; Mirzaei, Ali; Kim, Tae-Bum; Shin, Young-Chul; Choi, Ho-Joon; Kim, Hyoun Woo; Jin, Changhyun

    2016-09-01

    For the first time, Bi-doped In2O3-indium tin oxide (ITO) nanocomposites were prepared on Si substrates with the assistance of a Au catalyst through the simple gas-phase transport of a mixture of Bi, In, and Sn powders. The square-shaped Bi-doped In2O3-ITO nanostructures were straight, a few hundreds of nanometres in width, and below a few tens of micrometres in length. Electron microscopy, x-ray diffraction, and energy-dispersive x-ray spectroscopy analyses indicated that the Bi-doped In2O3-ITO nanorods were single crystals with a basis of cubic In2O3 structures. The photoluminescence spectra revealed that the Bi-doped In2O3-ITO nanorods had a strong orange emission band centred at approximately 626 nm without any shoulder bands. The enhancement of orange emission might be due to the oxygen deficiencies of structural defects in the nanorods.

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    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 Tb3+ 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 5D4→7F5 emission spectra of this complex.

  20. Photoluminescence enhancement and morphological properties of carbon codoped GaN:Er

    SciTech Connect

    Overberg, M.E.; Abernathy, C.R.; Pearton, S.J.; Wilson, R.G.; Zavada, J.M.

    2000-07-01

    The surface morphology and the room temperature 1.54 {micro}m photoluminescence (PL) intensity from GaN:Er grown by gas source molecular beam epitaxy have been investigated as a function of C concentration as introduced by CBr{sub 4}. Similar to previous results with increasing Er level, increasing the C concentration initially improved the surface smoothness as measured by atomic force microscopy (AFM) and scanning electron microscopy (SEM), with RMS roughness improving by a factor of seven over undoped GaN. The PL also improved dramatically. However, the highest amounts of C investigated produced a decrease in the PL as well as a roughening of the film surface. These effects indicate that the GaN:Er had reached its C solubility limit, producing an increased amount of defect induced nonradiative recombination.

  1. Vaterite-type YBO 3:Eu 3+ crystals: hydrothermal synthesis, morphology and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Lin, Jun

    2004-10-01

    Vaterite-type YBO 3:Eu 3+ crystals with interesting flower and hedgehog fungus-like structures composed of nanosheets were obtained by controlled crystallization of Y 2O 3 and Eu 2O 3 in H 3BO 3 solutions under acidic hydrothermal (HT) conditions. Nanosheets of uniform thicknesses were formed by preferential crystal growth along the (1 0 0) crystallographic plane and specific three-dimensional structures were further developed through a homocentric growth mechanism. Optical emission measurements showed that the HT-grown nanosheet crystals exhibited a higher ratio of the emitted red-to-orange light ratio than crystals grown from solid-state reactions. The photoluminescence intensity and emission lifetimes were also studied as a function of the Eu 3+ dopant concentration and the HT synthesis temperature. The effect of some additives: a chelating ligand, a surfactant and a polymer, on the YBO 3:Eu 3+ crystals morphology was also investigated.

  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

    2009-11-11

    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.

  3. 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

  4. Thermal-treatment effect on the photoluminescence and gas-sensing properties of tungsten oxide nanowires

    SciTech Connect

    Sun, Shibin; Chang, Xueting; Li, Zhenjiang

    2010-09-15

    Single-crystalline non-stoichiometric tungsten oxide nanowires were initially prepared using a simple solvothermal method. High resolution transmission electron microscopy (HRTEM) investigations indicate that the tungsten oxide nanowires exhibit various crystal defects, including stacking faults, dislocations, and vacancies. A possible defect-induced mechanism was proposed to account for the temperature-dependent morphological evolution of the tungsten oxide nanowires under thermal processing. Due to the high specific surface areas and non-stoichiometric crystal structure, the original tungsten oxide nanowires were highly sensitive to ppm level ethanol at room temperature. Thermal treatment under dry air condition was found to deteriorate the selectivity of room-temperature tungsten oxide sensors, and 400 {sup o}C may be considered as the top temperature limit in sensor applications for the solvothermally-prepared nanowires. The photoluminescence (PL) characteristics of tungsten oxide nanowires were also strongly influenced by thermal treatment.

  5. Indium-incorporation enhancement of photoluminescence properties of Ga(In)SbBi alloys

    NASA Astrophysics Data System (ADS)

    Linhart, W. M.; Gladysiewicz, M.; Kopaczek, J.; Rajpalke, M. K.; Ashwin, M. J.; Veal, T. D.; Kudrawiec, R.

    2017-09-01

    Ga(In)SbBi alloys grown by molecular-beam epitaxy on GaSb substrates with up to 5.5% In and 1.8% Bi were studied by temperature- and power-dependent photoluminescence (PL) and compared to previous photoreflectance (PR) results. High energy and low energy PL peaks were observed and attributed respectively to Ga(In)SbBi bandgap-related emission and native acceptor-related emission. For GaSbBi below 100 K, the HE peak is at slightly lower energy than the bandgap determined from PR, indicating carrier localization. This phenomenon is significantly weaker in PL of GaInSbBi alloys, suggesting that the presence of indium improves the optical quality over that of GaSbBi.

  6. 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

    2010-11-01

    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.

  7. Synthesis and photoluminescence properties of SnO 2/ZnO hierarchical nanostructures

    NASA Astrophysics Data System (ADS)

    Lan, Changyong; Gong, Jiangfeng; Su, Yun; Li, Kenan; Yang, Shaoguang

    2012-01-01

    SnO 2/ZnO hierarchical nanostructures were synthesized by a two-step carbon assisted thermal evaporation method. SnO 2 nanowires were synthesized in the first step and were then used as substrates for the following growth of ZnO nanowires in the second step. Sn metal droplets were formed at the surfaces of the SnO 2 nanowires during the second step and were acted as catalyst to facilitate the growth of ZnO nanowires via vapor-liquid-solid mechanism. Room temperature photoluminescence measurements showed that the SnO 2/ZnO hierarchical nanostructures exhibited a strong green emission centered at about 520 nm and a weak emission centered at about 380 nm. The emissions from the SnO 2 were drastically constrained due to screen effect caused by the ZnO layer.

  8. New copper(I) iodides with bisimidazole molecules: Synthesis, structural characterization and photoluminescence property

    NASA Astrophysics Data System (ADS)

    Wang, Rong-Yan; Zhang, Xiao; Yang, Qing-Feng; Huo, Qi-Sheng; Yu, Jie-Hui; Xu, Jia-Ning; Xu, Ji-Qing

    2017-07-01

    The hydro(solvo)thermal reactions of CuI with diverse bisimidazole molecules were investigated, affording five new copper(I) iodides [Cu4I4(L1)2] (L1=1,3-bis(2-methylimidazol-1-ylmethyl)benzene) 1, [CuI(L2)] (L2=4,4‧-bis(imidazolyl)biphenyl) 2, [Cu4I4(L3)] (L3=1,3-bis(2-methylimidazol-1-yl)propane) 3, [Cu4I4(L4)2] (L4=1,4-bis(2-ethylimidazol-1-yl)butane) 4, and [Cu4I4(L5)] (L5=1,4-bis(1-imidazoly)benzene) 5. X-ray single-crystal diffraction analysis reveals that (i) in 1, a tetranuclear Cu-I cluster (stepped cubane) is observed, and the L1 molecule only acts as an ancillary ligand; (ii) in 2, the L2 molecules extend the castellated Cu-I chains into a 2-D layer network with a certain thickness; (iii) in 2-D single-layer network of 3, a 1-D Cu-I column is found, which can be viewed as a longitudinal packing of stepped Cu4I4 cubanes; (vi) in 4, the L4 molecules propagate the cubic Cu4I4 cubanes into a 3-D 4-fold interpenetrated network with a cds topology; and (v) in 5, the L5 molecules link the 1-D Cu-I ribbons into a 2-D single-layer network. The photoluminescence analysis indicates that 1, 2 and 4 emit light (red light for 1; yellow light for 2 and 4), while 3 and 5 are not emissive. Their photoluminescence behaviors are confirmed to be related to the Cu···Cu interactions in the molecules.

  9. Self-assembled nanostructures of specially designed Schiff-bases and their zinc complexes: Preparation, characterization and photoluminescence property

    NASA Astrophysics Data System (ADS)

    Guha, Averi; Sanyal, Ria; Chattopadhyay, Tanmay; Han, YounGyu; Mondal, Tapan Kumar; Das, Debasis

    2013-06-01

    Four specially designed Schiff bases 2-formyl-4-R-6-(3N-4-hydroxybenzoicacid)-iminomethyl-phenolato (where R = methyl/tert-butyl/chloro for L1, L2, L3 respectively) and 2-(3N-4-hydroxybenzoicacid)-iminomethyl-phenolato (L4) having ability to form hydrogen bonding and their zinc complexes (1-4) have been synthesized and characterized. These complexes gave various types of nano-sized materials via self-assembly in solid state. FE-SEM was employed to investigate their morphology. Using a variety of analytical techniques such as elemental analysis, infrared spectroscopy (FT-IR), ESI-MS and 1H NMR spectroscopy, a consistent picture of structures of these complexes are obtained. All the Schiff-bases and their zinc complexes exhibit photoluminescence property. Density functional theory calculation has been performed to rationalize the origin of the spectral bands of the ligands as well as the complexes.

  10. 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.

  11. Synthesis of Sb-doped ZnO microspheres by pulsed laser ablation and their photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Tanaka, T.; Shimogaki, T.; Nagasaki, F.; Higashihata, M.; Nakamura, D.; Ikenoue, H.; Okada, T.

    2015-03-01

    We succeeded in synthesizing antimony (Sb)-doped ZnO microspheres by ablating a ZnO sintered target containing 5 wt% of Sb with a Nd:YAG laser at a fluence of 25 J/cm2 in air. The well-spherical ZnO microcrystals with diameters of 1-20 μm were collected on a substrate which was put near the ablation spot. Most of the ZnO microspheres have a crystalline structure. In addition, Raman peak of the Sb-doped ZnO microspheres was shifted toward lower frequency side, indicating substitutional Sb3+ at Zn antisite. Room-temperature photoluminescence properties of the microsphere were investigated under 325 nm He-Cd laser or 355 nm Nd:YAG laser excitation. An ultraviolet (UV) emission and lasing in whispering gallery mode were observed from the photoexcited microsphere.

  12. 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.

  13. 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.

  14. 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.

  15. Photoluminescence properties of new Zn(II) complexes with 8-hydroxyquinoline ligands: Dependence on volume and electronic effect of substituents

    NASA Astrophysics Data System (ADS)

    Huo, Yanping; Lu, Jiguo; Hu, Sheng; Zhang, Liming; Zhao, Fenghua; Huang, Huarong; Huang, Baohua; Zhang, Li

    2015-03-01

    A series of 2-arylethenyl-8-hydroxyquinoline ligands (A1-A4) with a trimethoxyphenyl, naphthyl, 2-fluoro-4-bromophenyl and anthracenyl group and their corresponding Zn(II) complexes (B1-B4) were synthesized and characterized by means of 1H NMR, ESI-MS, FT-IR and elemental analysis. A1 and A4 were characterized by single-crystal X-ray crystallography. The aggregation behavior of zinc salt and ligands in solution was investigated by several techniques, containing 1H NMR, UV-vis and photoluminescence (PL). The electronic nature and volume of arylethenyl substituents affect the absorption wavelength, the emission color, fluorescence lifetime, fluorescence quantum yield and thermostability of Zn(II) complexes. The experiments corroborated that the properties of Zinc(II) complexes can be tuned by introducing different functional substituents.

  16. 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.

  17. INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Dependence of the photoluminescence density on surface preparation and properties of n-type InP

    NASA Astrophysics Data System (ADS)

    Knauer, A.; Gramlich, S.; Staske, R.

    1988-11-01

    Comprehensive studies were made of the relationship between the photoluminescence intensity and the effective carrier lifetime, on the one hand, and the quality of the surface treatment of wafers (damage, oxide layer thickness) and the initial properties of a material (surface and bulk defects, inhomogeneity of the dopant concentration), on the other.

  18. Photoluminescence and electrochemical properties of transparent CeO2-ZnO nanocomposite thin films prepared by Pechini method

    NASA Astrophysics Data System (ADS)

    Sani, Z. Khosousi; Ghodsi, F. E.; Mazloom, J.

    2017-02-01

    Nanocomposite thin films of CeO2-ZnO with different molar ratios of Zn/Ce (=0, 0.25, 0.5, 0.75 and 1) were prepared by the Pechini sol-gel route. Various spectroscopic and electrochemical techniques were applied to investigate the films. XRD patterns of all the samples exhibited the peaks corresponding to cubic fluorite structure of ceria and the (101) and (103) peaks of ZnO with hexagonal structure was just observed in the sample with molar ratio of 1. EDS confirmed the presence of constituent of element in the samples. FESEM images of the films showed a surface composed of nanograins. AFM analysis revealed that root mean square roughness was enhanced as molar ratio of Zn/Ce increased. Moreover, fractal dimension of surfaces were calculated by cube counting approach. Optical measurements indicated that the film with molar ratio of 1 has the highest transmission and lowest reflectivity. The optical band gap values varied between 2.95 and 3.42 eV. The compositional dependence of refractive index and extinction coefficient were reported. The UV and blue emission appeared in PL spectra. The highest photoluminescence emission intensity was observed in the 1:1 molar ratio sample. The cyclic voltammetry measurements indicated the highest charge density (9.75 mC cm-2) and diffusion coefficient (3.507 × 10-17 cm2 s-1) belonged to the Ce/Zn (1:1) thin film.

  19. Structure twinning, electronic and photoluminescence properties of yavapaiite-type orthophosphate BaTi(PO4)2

    NASA Astrophysics Data System (ADS)

    Zhao, Dan; Ma, Fa-Xue; Yang, Hong; Wei, Wei; Fan, Yun-Chang; Zhang, Lei; Xin, Xia

    2016-12-01

    A ternary orthophosphate BaTi(PO4)2 has been prepared using a high temperature molten salt method and structurally determined by single crystal X-Ray diffraction analysis. It crystallizes in yavapaiite-type structure with monoclinic space group C2/m. The structure was refined by a non-merohedral twinning model with the twin law (-0.435 1.4350 -0.564 -0.435 0 0.097 -0.099 1). Band structure calculation using the density functional theory (DFT) method indicates that BaTi(PO4)2 has a direct bond gap of about 3.00 eV, which is well fitted with the experimental value of 2.95 eV. The photoluminescence excitation and emission spectra, decay curve, and the color coordinates for BaTi(PO4)2 were investigated. It can be efficiently excited by UV light (270 nm) and presents blue-green emission (centered at 506 nm), which may be attributed to the lattice defect emission.

  20. Photoluminescent properties of spider silk coated with Eu-doped nanoceria

    NASA Astrophysics Data System (ADS)

    Dmitrović, Svetlana; Nikolić, Marko G.; Jelenković, Branislav; Prekajski, Marija; Rabasović, Mihailo; Zarubica, Aleksandra; Branković, Goran; Matović, Branko

    2017-02-01

    Spider dragline silk was coated with pure as well as Eu-doped ceria nanopowders at the room temperature. The treatment was done by immersion of the spider silk mesh into aqueous solutions of cerium nitrate (Ce(NO3)3) and ammonium hydroxide (NH4OH). Depending on the relationship between Ce3+ ion and ammonium hydroxide concentration, coated fibers exhibited a different thickness. Obtained materials were studied by means of FESEM. It was found that ceria nanoparticles of average size of 3 nm were coated along spider thread. X-ray diffraction (XRD) and selected-area electron diffraction (SAED) confirmed crystal nature of nanoparticle coating of spider silk. By using Williamson-Hall plots, crystallite size and strain were estimated. EDS measurement confirmed the presence of Eu in spider-Eu-doped ceria composite, and according to FTIR analysis, the interaction between CeO2 and spider silk was proposed. The morphology of obtained composite was observed by TEM. The photoluminescence emission spectra of spider silk coated with Eu-doped ceria were measured with two different excitations of 385 and 466 nm. The two-photon excited auto-fluorescence of spider silk coated with Eu-doped ceria was detected using a nonlinear laser scanning microscope. Obtained composite has a potential as a fluorescent labeling material in diverse applications.

  1. Growth, structure and photoluminescence properties of SnO2-ZnO (TZO) micro cubes

    NASA Astrophysics Data System (ADS)

    Samal, S.; Panda, A. B.; Acharya, B. S.

    2017-02-01

    Structural investigation from X-ray diffraction patterns of TZO revealed the presence of SnO2 (cassiterite), ZnO (wurtzite) and ZnSnO3 and ZnSnO4 phases. The optical absorption spectra recorded for these powders dispersed in ethanol show the nature of the composite nanopowders to be semiconducting one having an optical absorption band around 280nm. Electron microscopy confirms a change in shape and size of the particles with a change in Sn/Zn ratio. The amorphous nature increases while going from Sn/Zn ratio of 0.87 to 3.75 and cubes of size ∼ 2μm, rhombohedral and irregular shaped particles are also observed. The prepared tin zinc oxide samples (TZO) show excitation bands at 241, 287 and 351 nm and common emission bands at 448, 485, 462 and 531 nm for all excitation energies. The photoluminescence and other studies reveal the role played by composition in changing the shape.

  2. Growth Mechanisms of Inductively-Coupled Plasma Torch Synthesized Silicon Nanowires and their associated photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Agati, M.; Amiard, G.; Le Borgne, V.; Castrucci, P.; Dolbec, R.; de Crescenzi, M.; El Khakani, M. A.; Boninelli, S.

    2016-11-01

    Ultra-thin Silicon Nanowires (SiNWs) were produced by means of an industrial inductively-coupled plasma (ICP) based process. Two families of SiNWs have been identified, namely long SiNWs (up to 2–3 micron in length) and shorter ones (~100 nm). SiNWs were found to consist of a Si core (with diameter as thin as 2 nm) and a silica shell, of which the thickness varies from 5 to 20 nm. By combining advanced transmission electron microscopy (TEM) techniques, we demonstrate that the growth of the long SiNWs occurred via the Oxide Assisted Growth (OAG) mechanism, while the Vapor Liquid Solid (VLS) mechanism is responsible for the growth of shorter ones. Energy filtered TEM analyses revealed, in some cases, the existence of chapelet-like Si nanocrystals embedded in an otherwise silica nanowire. Such nanostructures are believed to result from the exposure of some OAG SiNWs to high temperatures prevailing inside the reactor. Finally, the intense photoluminescence (PL) of these ICP-grown SiNWs in the 620–950 nm spectral range is a clear indication of the occurrence of quantum confinement. Such a PL emission is in accordance with the TEM results which revealed that the size of nanostructures are indeed below the exciton Bohr radius of silicon.

  3. Low-temperature collapsing boron nitride nanospheres into nanoflakes and their photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Li, Jie; Luo, Han; Lin, Jing; Xue, Yanming; Liu, Zhenya; Jin, Peng; Xu, Xuewen; Huang, Yang; Liu, Dong; Zhang, Jun; Tang, Chengchun

    2014-09-01

    Flake-like boron nitride (BN) nanocrystals with a uniform diameter of ˜200 nm and thickness of ˜20 nm were fabricated by directly transforming from BN nanospheres with the assistance of NaCl salt at 1300 °C. The transformation from nanospheres to nano-pies and further to nanoflakes was achieved in a simple procedure of Na or Cl ions intercalation/deintercalation procedure at such low temperature. The morphologies of the spherical precursor and resulting nanoflakes were almost identical. X-ray powder diffractions revealed that the BN nanoflakes (BNfs) were well crystallized in the hexagonal structure via graphitizing index calculation. Elemental content analysis, FTIR spectra and TEM images were also used to characterize the products. Strong ultraviolet (UV) emissions were detected by photoluminescence (PL) spectroscopic analysis, in which the emission regions could be facilely tuned by controlling the reaction temperature. Detailed studies indicated that the collapsing temperature of unstable BN nanospheres into nanoflakes was strongly dependent on the introduction of NaCl molten salts or not. We believe the use of the NaCl molten salt medium may enhance the kinetics of the crystallization and also purification. The green fabrication characteristics, such as using NaCl salt as the additive, energy saving (300 °C lower than the commercial process), non-toxicity of byproduct and easy scale-up, make the present novel synthetic route likely to be of interest to commercial-scale production of BN nanoflakes.

  4. Ion Insertion on the Crystal Structure, Photoluminescence, and Dielectric Properties of o-Mullite Nanoparticles

    NASA Astrophysics Data System (ADS)

    Sanad, M. M. S.; Rashad, M. M.; Abdel-Aal, E. A.; El-Shahat, M. F.; Powers, K.

    2014-09-01

    Nanocrystalline Gd3+-doped Gd x Al6- x Si2O13 mullite powders with x from 0.005 to 0.025 have been synthesized via a facile coprecipitation technique. X-ray diffraction results revealed that o-mullite was detected as the major phase for x = 0.0 to 0.01, whereas corundum α-Al2O3 was predominant for x = 0.025. It was found that the volume of the mullite unit cell increased with Gd3+ ion incorporation. Differential scanning calorimetry thermograms evinced that the exothermic peak temperature of mullite shifted to lower values with Gd3+ ion insertion. Transmission electron microscopy observations of pure mullite nanoparticles displayed orthorhombic-like shapes. Meanwhile, at 0.5% Gd3+ ion content, the mullite particles exhibited platelet-like shapes, which distorted into spheroidal-like crystals at high Gd3+ ion contents (1% and 2.5%). The photoluminescence spectra indicated that the intensity of the emission spectra improved considerably with Gd3+ ion doping. On the other hand, dielectric measurements of sintered samples showed that the maximum dielectric loss values were 1.7 and 1.4 at 1.5 MHz and 1.5 GHz, respectively, with 2.5% Gd3+ ion content.

  5. Growth Mechanisms of Inductively-Coupled Plasma Torch Synthesized Silicon Nanowires and their associated photoluminescence properties.

    PubMed

    Agati, M; Amiard, G; Le Borgne, V; Castrucci, P; Dolbec, R; De Crescenzi, M; El Khakani, M A; Boninelli, S

    2016-11-22

    Ultra-thin Silicon Nanowires (SiNWs) were produced by means of an industrial inductively-coupled plasma (ICP) based process. Two families of SiNWs have been identified, namely long SiNWs (up to 2-3 micron in length) and shorter ones (~100 nm). SiNWs were found to consist of a Si core (with diameter as thin as 2 nm) and a silica shell, of which the thickness varies from 5 to 20 nm. By combining advanced transmission electron microscopy (TEM) techniques, we demonstrate that the growth of the long SiNWs occurred via the Oxide Assisted Growth (OAG) mechanism, while the Vapor Liquid Solid (VLS) mechanism is responsible for the growth of shorter ones. Energy filtered TEM analyses revealed, in some cases, the existence of chapelet-like Si nanocrystals embedded in an otherwise silica nanowire. Such nanostructures are believed to result from the exposure of some OAG SiNWs to high temperatures prevailing inside the reactor. Finally, the intense photoluminescence (PL) of these ICP-grown SiNWs in the 620-950 nm spectral range is a clear indication of the occurrence of quantum confinement. Such a PL emission is in accordance with the TEM results which revealed that the size of nanostructures are indeed below the exciton Bohr radius of silicon.

  6. Growth Mechanisms of Inductively-Coupled Plasma Torch Synthesized Silicon Nanowires and their associated photoluminescence properties

    PubMed Central

    Agati, M.; Amiard, G.; Le Borgne, V.; Castrucci, P.; Dolbec, R.; De Crescenzi, M.; El Khakani, M. A.; Boninelli, S.

    2016-01-01

    Ultra-thin Silicon Nanowires (SiNWs) were produced by means of an industrial inductively-coupled plasma (ICP) based process. Two families of SiNWs have been identified, namely long SiNWs (up to 2–3 micron in length) and shorter ones (~100 nm). SiNWs were found to consist of a Si core (with diameter as thin as 2 nm) and a silica shell, of which the thickness varies from 5 to 20 nm. By combining advanced transmission electron microscopy (TEM) techniques, we demonstrate that the growth of the long SiNWs occurred via the Oxide Assisted Growth (OAG) mechanism, while the Vapor Liquid Solid (VLS) mechanism is responsible for the growth of shorter ones. Energy filtered TEM analyses revealed, in some cases, the existence of chapelet-like Si nanocrystals embedded in an otherwise silica nanowire. Such nanostructures are believed to result from the exposure of some OAG SiNWs to high temperatures prevailing inside the reactor. Finally, the intense photoluminescence (PL) of these ICP-grown SiNWs in the 620–950 nm spectral range is a clear indication of the occurrence of quantum confinement. Such a PL emission is in accordance with the TEM results which revealed that the size of nanostructures are indeed below the exciton Bohr radius of silicon. PMID:27874057

  7. Study on Photoluminescence Properties of Co-DOPED ZnO

    NASA Astrophysics Data System (ADS)

    Guo, Shuxia; Li, Jiwu; Du, Zuliang

    2014-12-01

    ZnO and Co-doped ZnO have been synthesized by co-precipitation technique. X-ray diffraction (XRD) patterns and absorption spectra show that Co ions are doped into the lattice positions of ZnO. Photoluminescence (PL) experiments on the samples have been performed in order to study the sp-d interaction in ZnO:Co. Room temperature measurements show two additional emissions related to Co besides the ZnO exciton-related and trap emissions. The two emissions are attributed to the transitions from Co+ to the excited Co2+ state and from 2E(G) to 4 A2(F), respectively. The charge-transfer transitions related to Co2+ exciting 3d intrashell luminescence at 1.78 eV has been observed. A blue-shift in the exciton-related emission, a red-shift in the blue emission and no shift in the green emission were revealed and interpreted by the sp-d interaction.

  8. Sol-gel synthesis, structure and photoluminescence properties of nanocrystalline Lu{sub 2}MoO{sub 6}:Eu

    SciTech Connect

    Li, Huaiyong; Yang, Hyun Kyoung; Jeong, Jung Hyun; Jang, Kiwan; Lee, Ho Sueb; Yi, Soung Soo

    2011-09-15

    Highlights: {yields} Monoclinic-structural Lu{sub 2}MoO{sub 6} has strong absorption of near-UV light. {yields} The absorbed energy can be transferred from MoO{sub 5} groups to doped Eu{sup 3+} and luminescence. {yields} The absorption edge and the peak of the MoO{sub 5} excitation band shift in reverse ways. {yields} The decline of the crystallinity and the introduced defect respond for the variation. -- Abstract: In this paper, we reported the obtention of Eu{sup 3+} ion doped Lu{sub 2}MoO{sub 6} powders synthesized by a sol-gel method, and followed by annealing at different temperatures. The structure and photoluminescence properties of these powders were investigated. The X-ray diffraction pattern suggests that Lu{sub 2}MoO{sub 6} powder has a monoclinic structure. It was observed that the UV-visible and photoluminescence spectra of Lu{sub 2}MoO{sub 6}:Eu nanocrystallines varied systematically with the calcination temperature. The near-UV absorption edge shifts to long wavelength direction with the decreasing of the calcination temperature, while the peak of MoO{sub 5} excitation band shifts in an opposite way. The decline of the crystallinity and the introduced lattice defect were considered to respond for these variations. Additionally, due to the efficient red light emission under near-UV light excitation, the powder can be a candidate as red phosphor for white-light-emitting diodes.

  9. 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.

  10. Optoelectronic properties analysis of Ti-substituted GaP.

    PubMed

    Tablero, C

    2005-11-08

    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.

  11. Homoleptic lanthanide 1,2,3-triazolates (∞)(2–3)[Ln(Tz*)3] and their diversified photoluminescence properties.

    PubMed

    Rybak, J-Christoph; Meyer, Larissa V; Wagenhöfer, Julian; Sextl, Gerhard; Müller-Buschbaum, Klaus

    2012-12-17

    The series of homoleptic lanthanide 1,2,3-triazolates (∞)(3)[Ln(Tz*)3] (Ln3+ = lanthanide cation, Tz*– = 1,2,3-triazolate anion, C2H2N3(–)) is completed by synthesis of the three-dimensional (3D) frameworks with Ln = La, Ce, Pr, Nd, and Sm, and characterization by X-ray powder diffraction, differential thermal analysis-thermogravimetry (DTA/TG) investigations and molecular vibration analysis. In addition, α-(∞)(2)[Sm(Tz*)3], a two-dimensional polymorph of 3D β-(∞)(3)[Sm(Tz*)3], is presented including the single crystal structure. The 3D lanthanide triazolates form an isotypic series of the formula (∞)(3)[Ln(Tz*)3] ranging from La to Lu, with the exception of Eu, which forms a mixed valent metal organic framework (MOF) of different structure and the constitution (∞)(3)[Eu(Tz*)(6+x)(Tz*H)(2–x)]. The main focus of this work is put on the investigation of the photoluminescence behavior of lanthanide 1,2,3-triazolates (∞)(3)[Ln(Tz*)3] and illuminates that six different luminescence phenomena can be found for one series of isotypic compounds. The luminescence behavior of the majority of these compounds is based on the photoluminescence properties of the organic linker molecules. Differing properties are observed for (∞)(3)[Yb(Tz*)3], which exhibits luminescence properties based on charge transfer transitions between the linker and Yb3+ ions, and for (∞)(3)[Ce(Tz*)3] and (∞)(3)[Tb(Tz*)3], in which the luminescence properties are a combination of the ligand and the lanthanide metal. In addition, strong inner-filter effects are found in the ligand emission bands that are attributed to reabsorption of the emitted light by the trivalent lanthanide ions. Antenna effects of varying efficiency are present indicated by the energy being transferred to the lanthanide ions subsequent to excitation of the ligand. (∞)(3)[Ce(Tz*)3] shows a 5d-4f induced intense blue emission upon excitation with UV light, while (∞)(3)[Tb(Tz*)3] shows emission in the green

  12. A Facile Synthesis and Photoluminescence Properties of Boron Carbon Oxynitride (BCNO) Phosphor Materials for Security Ink Application

    NASA Astrophysics Data System (ADS)

    Nuryantini, A. Y.; Nuryadin, B. W.; Mahen, E. C. S.; Sawitri, A.

    2017-02-01

    A facile synthesis of rare-earth free using boron carbon oxynitride (BCNO) phosphor material for security ink has been investigate. BCNO were synthesize by low temperature microwave heating methods, with H3BO3, citric acid and urea to be used as boron, carbon and nitrogen source, respectively. Then, the BCNO nanocrystals were disperse in water-polymer based solution until they became evenly spreading and turn into security ink without rare earth metals. The photoluminescence (PL) and UV-Visible spectroscopy were use to characterize the optical properties of BCNO and the security ink. The characterization results showed that BCNO and the security ink had similar PL properties (PL Peak and PL Peak Intensity). In addition, the UV-Vis spectra proved that the security ink had electronic properties such as being semiconductors based phosphor materials. The results indicate that BCNO phosphor material can be potentially be developed as rare-earth free security inks, and other applications such as optoelectronic, white LED, lighting, etc.

  13. Full-colour carbon dots: from energy-efficient synthesis to concentration-dependent photoluminescence properties.

    PubMed

    Meng, Xun; Chang, Qing; Xue, Chaorui; Yang, Jinlong; Hu, Shengliang

    2017-03-09

    We present a facile approach, without the need for external heating and any additional energy input, to produce fluorescent carbon dots (CDs) inexpensively and on a large scale. Fluorescence emission wavelengths from the obtained CDs shift gradually from 630 to 400 nm with reduction in their concentration in solution. This work offers a novel avenue for tuning band gaps in CDs and endowing them with potential for various applications.

  14. Correlation between surface modification and photoluminescence properties of β-Ga{sub 2}O{sub 3} nanostructures

    SciTech Connect

    Jangir, R. Tiwari, Pragya; Mondal, Puspen; Rai, S. K.; Srivastava, A. K.; Ganguli, Tapas; Porwal, S.; Bhaumik, Indranil

    2016-03-15

    In this work three different growth methods have been used to grow β-Ga{sub 2}O{sub 3} nanostructures. The nanostructures were characterized by Grazing Incident X-Ray Diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy and Photoluminescence Spectroscopy. Photoluminescence spectra for all the samples of β-Ga{sub 2}O{sub 3} nanostructures exhibit an UV and blue emission band. The relative intensity of UV and blue luminescence is strongly affected by the surface defects present on the nanostructures. Our study shows that Photoluminescence intensity of UV and blue luminescence can be reliably used to determine the quality of β-Ga{sub 2}O{sub 3} nanostructures. Further the work opens up the possibility of using UV excitation and subsequent Photoluminescence analysis as a possible means for oxygen sensing. The Photoluminescence mechanism in β-Ga{sub 2}O{sub 3} nanostructures is also discussed.

  15. 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.

  16. An enhancement of photoluminescence property of Ag doped La2O3 thin films at room temperature

    NASA Astrophysics Data System (ADS)

    Jbeli, R.; Boukhachem, A.; Ben Jemaa, I.; Mahdhi, N.; Saadallah, F.; Elhouichet, H.; Alleg, S.; Amlouk, M.; Ezzaouïa, H.

    2017-09-01

    Metal transition doped oxide thin films or nanocomposites have recently emerged at the forefront of potentials research. With the focus mainly on efficiency, the aspect of stability against optical irradiation of such materials has so far not been thoroughly addressed. This work covers the synthesis of silver doped lanthanum oxide thin films (La2O3:Ag) which have been prepared by the spray pyrolysis technique on glass substrates at 460 °C. Then, Ag thin films were grown on lanthanum oxide thin films by thermal evaporation. The present work aims to reach the synthesis of La2O3:Ag thin films using both the spray pyrolysis and thermal evaporation techniques. First, X-ray diffraction analysis shows that undoped and Ag doped films crystallize in a mixture of hexagonal and cubic phase with crystallites oriented along (001) direction. Raman spectroscopy shows the bands positions corresponding to hexagonal and cubic phases. On the other hand, an attempt regarding their optical properties has been carried out by means of photoluminescence measurements. Second, from electrical conductivity measurements, the activation energy decreases from 1.42 to 1.09 eV with the increase of annealing time and the charge carriers are following the CBH model as dominant charge transport mechanism. Finally, the annealing time influences the surface wettability property and transforms La2O3 character from hydrophobic (θ > 90°) to hydrophilic (θ < 90°).

  17. 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.

  18. Influences of doping and annealing on the structural and photoluminescence properties of Y2O3 nanophosphors.

    PubMed

    Som, S; Sharma, S K; Shripathi, T

    2013-05-01

    This paper reports the structural and optical properties of rare earth doped and codoped yttrium oxide nanophosphors. Dysprosium (Dy(3+)) and Terbium (Tb(3+)) doped and codoped yttrium oxide (Y2O3) phosphors were prepared by combustion synthesis method and subsequently annealed to high temperature to eliminate the hydroxyl group (-OH) and to get more crystallinity. The formation of compounds was confirmed by the X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR). The diffuse reflectance spectra (DRS) of doped and codoped Y2O3 powder phosphors were measured and it is observed that the absorption edge of the doped samples is shifted towards blue region with respect to undoped sample. The bandgap of the prepared samples were evaluated with the help of Kubelka-Munk function using Diffuse Reflectance Spectra (DRS) and an increase in bandgap was observed with the decrease in crystallite size. A strong characteristics emission from Tb(3+) and Dy(3+) ions was identified and the influence of doping concentration and annealing temperature on photoluminescence properties was systematically studied. Transfer of energy was observed in dysprosium-terbium codoped Y2O3 nanophosphor at room temperature from Dy(3+) ions to Tb(3+) ions.

  19. Effect of Mn doping on the optical, structural and photoluminescence properties of nanostructured ZnO thin film synthesized by sol-gel technique

    NASA Astrophysics Data System (ADS)

    Xin, Mei; Hu, Li Zhong; Liu, Dong-Ping; Yu, Nai-Sen

    2014-10-01

    Undoped and manganese doped nanocrystalline ZnO (ZnO:Mn) films were deposited onto glass substrates by a sol gel method combined with spin coating technique and water bath treatment. All of the films were annealed at 400 °C for 1 h. The effect of Mn incorporation on the structural, optical and photoluminescence (PL) properties of the ZnO films have been investigated. X-ray diffraction (XRD) analysis of the films reveals that the Mn-doped ZnO films consist of single phase ZnO with zincite structure (Card No. 36-1451) and 3 at.% Mn incorporation leads to the great improvement of the crystalline quality in Mn doped films and preferential c-axis orientation. Scanning electron microscopy (SEM) images showed that morphology and size of films were affected significantly by the Mn incorporation. Energy dispersive X-ray spectroscopy (EDX) analysis revealed the presence of Mn in the ZnO films. The doped films have improved optical transparency in the visible range. The optical band gap of the 3 at.% Mn incorporated ZnO thin film was found to be 3.43 eV. All films had a very strong blue-green emission under 390 nm excitation, for Mn doped films showed a weak band at 416 nm, a strong blue-green band at 455 nm and another weak peak at 586 nm. Indicating the potential applications of the nanostructured Mn doped ZnO thin films in nanoscale optoelectronic devices.

  20. A novel yellow-emitting SrAlSi4N7:Ce3+ phosphor for solid state lighting: Synthesis, electronic structure and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Ruan, Jian; Xie, Rong-Jun; Funahashi, Shiro; Tanaka, Yoshinori; Takeda, Takashi; Suehiro, Takayuki; Hirosaki, Naoto; Li, Yuan-Qiang

    2013-12-01

    Ce3+-doped and Ce3+/Li+-codoped SrAlSi4N7 phosphors were synthesized by gas pressure sintering of powder mixtures of Sr3N2, AlN, α-Si3N4, CeN and Li3N. The phase purity, electronic crystal structure, photoluminescence properties of SrAlSi4N7:Ce3+(Ce3+/Li+) were investigated in this work. The band structure calculated by the DMol3 code shows that SrAlSi4N7 has a direct band gap of 3.87 eV. The single crystal analysis of Ce3+-doped SrAlSi4N7 indicates a disordered Si/Al distribution and nitrogen vacnacy defects. SrAlSi4N7 was identified as a major phase of the fired powders, and Sr5Al5Si21N35O2 and AlN as minor phases. Both Ce3+ and Ce3+/Li+ doped SrAlSi4N7 phosphors can be efficiently excited by near-UV or blue light and show a broadband yellow emission peaking around 565 nm. A highest external quantum efficiency of 38.3% under the 450 nm excitation was observed for the Ce3+/Li+-doped SrAlSi4N7 (5 mol%). A white light LED lamp with color temperature of 6300 K and color rendering index of Ra=78 was achieved by combining Sr0.97Al1.03Si3.997N\\94\\maccounttest14=t0005_18193 7:Ce3+0.03 with a commercial blue InGaN chip. It indicates that SrAlSi4N7:Ce3+ is a promising yellow emitting down-conversion phosphor for white LEDs.

  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. 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.

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

    SciTech Connect

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

    2016-06-15

    Two novel three-dimensional (3D) pillar-layered metal-organic frameworks (MOFs), namely [Zn{sub 2}(μ{sub 2}-OH)(boaba)(1,4-bmimb)]{sub n} (1) and {[Zn_5K_2(μ_2-H_2O)_2(boaba)_4(1,2-bmimb)_2(H_2O)_2]·H_2O}{sub n} (2), were prepared by hydrothermal reactions (H{sub 3}boaba=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 (6{sup 3})(6{sup 9}·8)-gra net with binuclear [Zn{sub 2}(μ{sub 2}-OH)(COO)]{sup 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. - Graphical abstract: Two novel 3D pillar-layered metal-organic coordination networks with aromatic multicarboxylate anion and bis(imidazole) ligands have been synthesized and structurally characterized. Display Omitted - Highlights: • It is rarely reported that metal-organic frameworks prepared with 3,5-bis-oxyacetate-benzoic acid. • Two metal-organic frameworks based on positional isomeric ligands were synthesized and structurally characterized. • Compond 1 displays unique (3,5)-connected binodal gra topology. • Compound 2 exhibits (4,4,5,9)-connected 4-nodal topology based on the Zn(II)-K(I) heterometal rod-like substructures. • The photoluminescence properties of compound 1 and 2 have been investigated.

  4. Electronic properties of Janus silicene: new direct band gap semiconductors

    NASA Astrophysics Data System (ADS)

    Sun, Minglei; Ren, Qingqiang; Wang, Sake; Yu, Jin; Tang, Wencheng

    2016-11-01

    Using first-principles calculations, we propose a new class of materials, Janus silicene, which is silicene asymmetrically functionalized with hydrogen and halogen atoms. Formation energies and phonon dispersion indicated that all the Janus silicene systems exhibit good kinetic stability. As compared to silicane, all Janus silicene systems are direct band gap semiconductors. The band gap of Janus silicene can take any value between 1.91 and 2.66 eV by carefully tuning the chemical composition of the adatoms. In addition, biaxial elastic strain can further reduce the band gap to 1.11 eV (under a biaxial tensile strain up to 10%). According to moderate direct band gap, these materials demonstrate potential applications in optoelectronics, exhibiting a very wide spectral range, and they are expected to be highly stable under ambient conditions.

  5. 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.

  6. Soil properties in old-growth Douglas-fir gaps in the western Cascade Mountains of Oregon

    Treesearch

    Robert P. Griffiths; Andrew N. Gray; Thomas A. Spies

    2010-01-01

    This study had three objectives: (1) to determine if there are correlations between aboveground vegetation and belowground soil properties within large 50-m-diameter gaps, (2) to determine how large gaps influence forest soils compared with nongap soils, and (3) to measure the effects of differently sized gaps on gap soils. Circular canopy gaps were created in old-...

  7. 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

  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. 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. 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.

  11. Lanthanide-organic frameworks constructed from multi-functional ligands: Syntheses, structures, near-infrared and visible photoluminescence properties

    SciTech Connect

    Li Xinfa; Xie Zailai; Lin Jingxiang; Cao Rong

    2009-08-15

    A series of multi-functional ligands supported lanthanide-organic frameworks, formulated as [Ln(HL{sub 1})(H{sub 2}L{sub 2}){sub 0.5}(H{sub 4}L{sub 2}){sub 0.5}(H{sub 2}O)].(H{sub 2}O){sub 1.5}.{l_brace}Ln=La (1), Pr (2), Nd (3), Sm (4), Eu (5); H{sub 3}L{sub 1}=5-Sulfosaclicylic acid; H{sub 4}L{sub 2}=N,N'-piperazine (bis-methylene phosphonic acid){r_brace}, have been synthesized by hydrothermal reactions. Single crystal X-ray diffractions and powder XRD patterns confirm they are isostructural. They feature 3D framework structures based on extension of a 'zigzag' inorganic chain by organic linkers. Moreover, the photoluminescence properties of 5 and 3 have been investigated, and they show strong solid-state emissions in the visible and near-infrared (IR) regions at room temperature. - Graphical abstract: Five multi-functional ligands supported 3D lanthanide-organic frameworks have been synthesized and structurally characterized. Compounds 5 and 3 displayed strong solid-state emissions in the visible and near-infrared region at room temperature.

  12. 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.

  13. Improvement of photoluminescence properties of Eu3+ doped SrNb2O6 phosphor by charge compensation

    NASA Astrophysics Data System (ADS)

    Xue, Junpeng; Guo, Yue; Moon, Byung Kee; Park, Sung Heum; Jeong, Jung Hyun; Kim, Jung Hwan; Wang, Lili

    2017-04-01

    In this paper, a series of Eu3+-doped SrNb2O6 phosphors have been successfully prepared by a high-temperature solid-state reaction technique. The as-prepared samples exhibit strong red emission peak at around 612 nm, which is attributed to the 5D0-7F2 transition of the Eu3+ ion. Both the emission intensity and color rendering effect can be obviously improved in SrNb2O6:Eu3+ phosphors by self-compensation or co-doping with Li+ ions. Meanwhile, the decay time of phosphors can also be extended by charge compensation. The Judd-Ofelt theory is used to calculate the optical transition strength parameters and quantum efficiencies of the obtained samples. In addition, Eu3+ and Li+ concentration-dependent excitation and emission spectra are investigated in detail. The critical distance is determined to be about 11.48 Å and the strongest red emission intensity is achieved in the Sr0.7Nb2O6:0.15Eu3+,0.15Li+ phosphor. The CIE-1931coordinate (0.633, 0.366) of this sample is very close to that of the standard red light (0.67, 0.33). All of the results indicate that charge compensation approach can greatly improve the photoluminescence properties of Eu3+-doped SrNb2O6 phosphors, which will further promote their applications in solid state lighting.

  14. Effect of Al concentration on photoluminescence properties of sol-gel derived hydrogen annealed ZnO

    NASA Astrophysics Data System (ADS)

    Khan, Firoz; Ameen, Sadia; Song, Minwu; Husain, Mushahid; Mobin, Abdul; Shin, Hyung Shik

    2013-03-01

    The effect of the Al/Zn atomic ratio on the photoluminescence properties of hydrogen annealed undoped and Al rich ZnO (AZO) films was studied. The Al/Zn atomic ratios in the AZO films were varied from 0 to 40%. All the AZO films exhibited three peaks in the UV, green and red regions, whereas the undoped ZnO films had two peaks in the UV and green regions. The PL intensity in the UV and red regions increased with an increase in Al concentrations. The highest PL intensity in the UV region was observed in the 20% Al/Zn atomic ratio due to improvement in crystal quality which was also confirmed by XRD measurements. The PL emission in the red region was due to complex luminescent centers like (Vzn-Alzn)-. A blue shift was seen in the red region with the introduction of Al. The 20% AZO films obtained the strongest signal at -420 cm-1, whereas no FTIR signal was observed at 420 cm-1 in undoped ZnO. The bond signature at -420 cm-1 might be responsible for the highest PL intensity in NBE and red regions.

  15. 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.

  16. Syntheses, structures, and photoluminescent properties of two silver (I) coordination polymers with 1, 4-bis(imidazol-1-ylmethyl) benzene

    NASA Astrophysics Data System (ADS)

    Wang, Zhan-Hui; Chen, Shu-Fen; Wang, Dan-Feng; Hao, Hong-Jun; Mei, Hong-Xin; Huang, Rong-Bin; Zheng, Lan-Sun

    2013-10-01

    The ultrasonic reactions of Ag2O with 1, 4-bis(imidazol-1-ylmethyl) benzene (bix) and ancillary carboxylate ligands under the ammoniacal condition lead to two new coordination compounds, namely [Ag4(bix)4(pma)·(H2O)18]n(1) and [Ag(bix)(onb)·H2O]n(2)(H4pma = pyromellitic acid, Honb = o-nitrobenzoic acid). Both of the complexes have been characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. In complex 1, the Ag-bix 1D chains are connected with the 2D nets containing [Ag4(bix)2(pma)2] to form a 3D framework by Ag⋯Ag interaction. In complex 2, the coordination bonds link Ag(I) ions and bix ligands to form 1D chains which are extended into a 2D layer by inter-chain hydrogen bonds. The Ag⋯Ag interaction is also observed in 2. Moreover, the photoluminescence properties of the complexes were also investigated in the solid state at room temperature.

  17. Silver nanoparticles with 4,4‧-dicyanamidobiphenyl ligand: Synthesis, photoluminescent and electroluminescent properties and DFT calculations

    NASA Astrophysics Data System (ADS)

    Chiniforoshan, Hossein; Khalesi, Sara Bahmanpour; Tabrizi, Leila; Hajipour, Abdol R.; Chermahini, Alireza Najafi; Karimzadeh, Morteza

    2015-02-01

    In this research, a new complex of 4,4‧-dicyanamidobiphenyl (bpH2) ligand, Ag(bpH) has been synthesized and characterized by FT-IR, UV-Vis spectroscopies, and elemental analysis. The morphology and size of complex were determined by the scanning electron microscopy (SEM) image. The diameter of the complex was about 61 nm and the nanoparticles were spherical. TGA result indicated that this complex was thermally stable. Also, photoluminescent and electroluminescent properties of Ag(bpH) were reported. The blue-green light emission was observed by fabricating double-layer devices using Ag(bpH) as electron-transport and NPB as hole-transport material. In addition, this complex was optimized by B3LYP/LANL2DZ method. The calculated FT-IR and UV-Vis data are in better agreement with the experimental results. In addition to DFT calculations, natural bond orbital (NBO) was also performed at the same level of theory.

  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. Photoluminescence properties and energy levels of RE (RE = Pr, Sm, Er, Tm) in layered-CaZnOS oxysulfide

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi-Jun; Feng, Ang; Chen, Xiang-Yang; Zhao, Jing-Tai

    2013-12-01

    RE3+ (RE = Pr, Sm, Er, Tm)-activated CaZnOS samples were prepared by a solid-state reaction method at high temperature, and their photoluminescence properties were investigated. Doping with RE3+ (RE = Pr, Sm, Er, Tm) into layered-CaZnOS resulted in typical RE3+ (RE = Pr, Sm, Er, Tm) f-f line absorptions and emissions, as well as the charge transfer band of Sm3+ at about 3.3 eV. The energy level scheme containing the position of the 4f and 5d levels of all divalent and trivalent lanthanide ions with respect to the valence and conduction bands of CaZnOS has been constructed based on the new data presented in this work, together with the data from literature on Ce3+ and Eu2+ doping in CaZnOS. The detailed energy level scheme provides a platform for interpreting the optical spectra and could be used to comment on the valence stability of the lanthanide ions in CaZnOS.

  20. Influence of metallic and dielectric nanowire arrays on the photoluminescence properties of P3HT thin films.

    PubMed

    Handloser, M; Dunbar, R B; Wisnet, A; Altpeter, P; Scheu, C; Schmidt-Mende, L; Hartschuh, A

    2012-08-03

    The optical properties of organic semiconductor thin films deposited on nanostructured surfaces are investigated using time-resolved two-photon photoluminescence (PL) microscopy. The surfaces consist of parallel aligned metallic or dielectric nanowires forming well-defined arrays on glass substrates. Keeping the nanowire dimensions constant and varying only their spacing from 40 to 400 nm, we study the range of different types of nanowire-semiconductor interactions. For silver nanowires and spacings below 100 nm, the PL intensity and lifetime of P3HT and MDMO-PPV decrease rapidly due to the short-ranged metal-induced quenching that dominates the PL response with respect to a possible plasmonic enhancement of optical transition rates. In the case of P3HT however, we observe an additional longer-ranged reduction of non-radiative losses for both metallic and dielectric nanowires that is not observed for MDMO-PPV. Excitation polarization dependent measurements indicate that this reduction is due to self-assembly of the P3HT polymer chains along the nanowires. In conclusion, nanostructured surfaces, when fabricated across large areas, could be used to control film morphologies and to improve energy transport and collection efficiencies in P3HT-based solar cells.

  1. 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

  2. Synthesis and photoluminescent properties of nanocrystalline CaMoO4 thin film via chemical solution processing.

    PubMed

    Yu, Ping; Hu, Guo-Bing; Tian, Yun-Fei; Xiao, Ding-Quan; Liu, Yang; Guo, Qing-Wu

    2008-05-01

    Stoichiometric CaMoO4 thin film was successfully fabricated based on chemical solution processing. The thin films were deposited on Si(100) substrates by means of the spin-coating technique. X-ray diffraction reveals that the CaMoO4 thin film prepared are pure and well crystalline thin films. Atom Force Microscope photographs indicate that the film prepared possesses a homogeneous and dense surface morphology. The average grain size of the films was 40-50 nm, and the root-mean-square (RMS) of the surface roughness and the average surface roughness of the film measured were 2.161 nm and 1.726 nm respectively. The photoluminescent properties of calcium molybdate thin film under ultraviolet light excitation were systematically measured from 12 K to room temperature and a green emission band of the films were observed. The results of present work confirm that the chemical solution processing is a promising technology on the fabrication of CaMoO4 thin film.

  3. Synthesis, characterization and photoluminescence properties of CaSiO3:Eu3+ red phosphor.

    PubMed

    Nagabhushana, H; Nagabhushana, B M; Madesh Kumar, M; Chikkahanumantharayappa; Murthy, K V R; Shivakumara, C; Chakradhar, R P S

    2011-01-01

    CaSiO3:Eu3+ (1-5 mol%) red emitting phosphors have been synthesized by a low-temperature solution combustion method. The phosphors have been well characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and optical spectroscopy. PXRD patterns reveal monoclinic CaSiO3 phase can be obtained at 900°C. The SEM micrographs show the crystallites with irregular shape, mostly angular. Upon 254 nm excitation, the phosphor show characteristic fluorescence 5D0→7FJ (J=0, 1, 2, 3, 4) of the Eu3+ ions. The electronic transition located at 614 nm corresponding to 5D0→7F2 of Eu3+ ions, which is stronger than the magnetic dipole transition located at 593 nm corresponding to 5D0→7F1 of Eu3+ ions. Different pathways involved in emission process have been studied. Concentration quenching has been observed for Eu3+ concentration>4 mol%. UV-visible absorption shows an intense band at 240 nm in undoped and 270 nm in Eu3+ doped CaSiO3 which is attributed to oxygen to silicon (O-Si) ligand-to-metal charge-transfer (LMCT) band in the SiO3(2-) group. The optical energy band gap is widened with increase of Eu3+ ion dopant. Copyright © 2010 Elsevier B.V. All rights reserved.

  4. Optical absorption and photoluminescence properties of Nd3+ doped mixed alkali phosphate glasses-spectroscopic investigations.

    PubMed

    Ratnakaram, Y C; Srihari, N V; Kumar, A Vijaya; Naidu, D Thirupathi; Chakradhar, R P S

    2009-02-01

    Spectroscopic investigations were performed on 68NH(4)H(2)PO(4).xLi(2)CO(3)(30-x)K(2)CO(3) and 68NH(4)H(2)PO(4).xNa(2)CO(3)(30-x)K(2)CO(3) (where x=5, 10, 15, 20 and 25) glasses containing 2 mol% Nd(2)O(3). Various spectroscopic parameters (Racah (E(1), E(2), E(3)), spin-orbit (xi(4f)) and configuration interaction (alpha)) are reported. Judd-Ofelt intensity parameters (Omega(2), Omega(4), Omega(6)) are calculated for Nd(3+) doped two mixed alkali phosphate glass matrices. From the magnitude of Judd-Ofelt parameters, covalency is studied as a function of x in the glass matrix. Using Judd-Ofelt intensity parameters, total radiative transition probabilities (A(T)), radiative lifetimes (tau(R)), branching ratios (beta) and integrated absorption cross sections (Sigma) have been computed for certain excited states of Nd(3+) in these mixed alkali phosphate glasses. Emission cross sections (sigma(P)) are calculated for the two transitions, (4)G(7/2)-->(4)I(11/2) and (4)G(7/2)-->(4)I(13/2) of Nd(3+) in these mixed alkali phosphate glasses. Optical band gaps (E(opt)) for direct and indirect transitions are reported.

  5. Effects of counterions of colorful sandwich-type zinc(II) 4‧-phenyl-terpyridine compounds on photoluminescent and thermal properties

    NASA Astrophysics Data System (ADS)

    Zhang, Yongqiang; Zhou, Peng; Liang, Baohuan; Huang, Ling; Zhou, Yanling; Ma, Zhen

    2017-10-01

    Reactions between 4‧-phenyl-terpyridine (L) and several Zn(II) salts (p-toluenesulfonate, nitrate, trifluoromethane sulfonate or hexafluoroantimonate) led to the formation of the complexes [ZnL2](p-OSO2PhCH3)2 (1), [ZnL2](NO3)2 (2), [ZnL2](SO3CF3)2 (3) and [ZnL2](SbF6)2 (4), which were characterized by IR, 1H NMR, elemental analysis, UV-vis spectroscopies and single crystal X-ray diffraction, along with their TG-DTA thermal and photoluminescent properties. The four compounds show mononuclear Zn(II) structures with hexacoordinated, irregular ZnN6 octahedron geometries. Their colours and photo-luminescent properties have changed regularly depending on the counterions of the compounds.

  6. Effect of different Er 3+ compounds doping on microstructure and photoluminescent properties of oxyfluoride glass ceramics

    NASA Astrophysics Data System (ADS)

    Zeng, Fanqing; Ren, Guozhong; Qiu, Xiannian; Yang, Qibin

    2008-07-01

    Four different erbium compounds: Er 2O 3, ErOF, ErF 3 and ErCl 3, doped oxyfluoride glass ceramics were prepared. The microstructure and optical properties of the glasses and glass ceramics were determined by differential scanning calorimetry (DSC), X-ray diffraction (XRD), absorption spectra and luminescence spectra. The influence of four different Er 3+ compounds on the microstructure and optical properties of the glasses and their corresponding glass ceramics was analyzed in detail. The results indicated that upconversion luminescence and ratios of red to green emission of all the samples have close relationship with microstructures and the variety of the Er 3+ compounds. It was concluded that the glass ceramics doped with ErF 3 was the most beneficial for the precipitation of PbF 2 crystallites and had the lowest ratio of red to green emission. The mechanisms of the observed phenomena were discussed.

  7. Structural, morphological, ferromagnetic and photoluminescence properties of Fe-doped ZnO, prepared by hydrothermal route

    NASA Astrophysics Data System (ADS)

    Cernea, Marin; Mihalache, Valentina; Secu, Elisabeta Corina; Trusca, Roxana; Bercu, Vasile; Diamandescu, Lucian

    2017-04-01

    Fe doped ZnO particles of flower-like shape, hexagonal prisms and hybrid structures flower-prisms have been synthesized by hydrothermal technique, and their luminescence and magnetic properties have been investigated as a function of the morphology changes due to iron dopant (0-0.03 at.% Fe3+). The X-ray diffractograms of Zn1-xFexO powders indicated a hexagonal wurtzite polycrystalline structure. SEM images reveal the change of Zn1-xFexO grains shape from flower-like to hexagonal prisms as the Fe concentration (x) increases from 0 to 3 at.% Fe. Undoped ZnO shown weak room temperatures ferromagnetism, with high coercivity (Hc = 107 Oe) and saturation magnetization Ms of 1.5·10-3 emu/g. ZnO doped with 1 and 3 at.% Fe presented a significant increase of the magnetization in comparison with the undoped ZnO. For ZnO doped with 3 at.% Fe, Ms = 32.5·10-3 emu/g and Mrem = 0.78·10-3 emu/g. Compared with other reports on magnetic properties of undoped and Fe doped ZnO, these results indicated higher coercivity and smaller magnetizations. The drop in the intensity of characteristic green-yellow photoluminescence band of ZnO at about 550-600 nm was attributed to the decrease of the number of oxygen vacancies and interstitial oxygen. By increasing the Fe concentration, the electron paramagnetic resonance (EPR) signal of undoped ZnO decreases due to the decrease of defects concentration.

  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

    SciTech Connect

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

    2016-07-15

    Six new Co{sup II} complexes [Co(L{sup 1}){sub 4}(OH){sub 2}] (1), {[Co(L"1)(H_2O)_4]·2ClO_4}{sub ∞} (2), {[Co(L"1)(H_2O)_4]·SiF_6}{sub ∞} (3), {[Co(L"1)_3]·2ClO_4}{sub ∞} (4), [Co(L{sup 2})Cl{sub 2}]{sub ∞} (5) and {[Co(L"2)_2]·SiF_6}{sub ∞} (6) [L{sup 1}=3,6-bis(N-imidazolyl) pyridazine, L{sup 2}=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 Co{sup II} centers were linked by the L{sup 1} 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(L{sup 2})Cl{sub 2}]{sub n} with the Co{sup II} 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. - Graphical abstract: Six Co{sup II} complexes of bis(N-imidazolyl/benzimidazolyl)pyridazine were synthesized and structurally characterized. The fluorescence properties and photocatalytic activity for dye degradation under UV light of all complexes have been investigated and discussed. Display Omitted - Highlights: • Six new Co{sup II} complexes with bis(N-imidazolyl/benzimidazolyl) pyridazine. • Structural analysis of all complexes. • Fluorescent property of all complexes. • Photocatalytic activity for dye degradation under UV light of all complexes.

  10. 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.

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

    PubMed

    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.

  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. Synthesis and photoluminescent properties of two novel tripodal compounds containing coumarin moieties

    NASA Astrophysics Data System (ADS)

    Yu, Tianzhi; Zhang, Peng; Zhao, Yuling; Zhang, Hui; Meng, Jing; Fan, Duowang

    2009-07-01

    Two novel tripodal compounds, tris[2-(7-diethylamino-coumarin-3-carboxamide)ethyl]amine (Tren-C1) and tris[2-(benzo[5,6]coumarin-3-carboxamide)ethyl]amine (Tren-C2), were synthesized and characterized. The UV-vis and fluorescence properties of Tren-C1 and Tren-C2 in solutions were investigated. These two compounds exhibited strong blue emission under ultraviolet light excitation. The maximal fluorescence emission occurred at about the level of 10 -5 mol/L. The chromophore units in the tripodal compounds shown a little interaction in the ground state, while the interactions in the excited state was notable and which leads to a broad and bathochromic shift of the emission bands.

  14. Structural, optical and photoluminescence properties of Eu3 + doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Ntwaeaborwa, Odireleng Martin; Mofokeng, Sefako J.; Kumar, Vinod; Kroon, Robin E.

    2017-07-01

    The structure, particle morphology and luminescent properties of europium (Eu3 +) doped ZnO nanoparticles (NPs) prepared by co-precipitation method are discussed. When excited using a 325 nm He-Cd laser, undoped ZnO NPs exhibited weakly the well-known ultraviolet excitonic recombination emission (at 384 nm) and strongly broad band visible emissions associated with defects (at 600 nm). In addition, the ZnO NPs exhibited green emission at 600 nm associated with defects when excited using a monochromatized xenon lamp. Upon Eu3 + doping line emissions attributed to 5D0 → 7F1,2,3,4 transitions of Eu3 + ions were observed when the materials were excited using a monochromatized xenon lamp. The exchange interaction mechanism is identified as the cause for concentration quenching of the luminescence of Eu3 + doped ZnO NPs in this study.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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 Fe2+ ions in the ZnS NWs was about two times larger than that of the Mn2+ or Cu2+ 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 Mn2+/Cu2+/Fe2+ related emission peaks can be observed in the Mn2+,Cu2+ and Fe2+ doped ZnS NWs. The ferromagnetic properties of the co-doped samples were investigated at room temperature.

  16. 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).

  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. 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.

  19. 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.

  20. Microstructure, ferromagnetic and photoluminescence properties of ITO and Cr doped ITO nanoparticles using solid state reaction

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    Indium-tin-oxide (ITO) (In0.95Sn0.05)2O3 and Cr doped indium-tin-oxide (In0.90Sn0.05Cr0.05)2O3 nanoparticles were prepared using simple low cost solid state reaction method and characterized by different techniques to study their structural, optical and magnetic properties. Microstructures, surface morphology, crystallite size of the nanoparticles were studied using X-ray diffractometer (XRD), field emission scanning electron microscope (FE-SEM). From these methods it was found that the particles were about 45 nm. Chemical composition and valence states of the nanoparticles were studied using energy dispersive analysis of X-rays (EDAX) and X-ray photoelectron spectroscopy (XPS). From these techniques it was observed that the elements of indium, tin, chromium and oxygen were present in the system in appropriate ratios and they were in +3, +4, +3 and -2 oxidation states. Raman studies confirmed that the nanoparticle were free from unintentional impurities. Two broad emission peaks were observed at 330 nm and 460 nm when excited wavelength of 300 nm. Magnetic studies were carried out at 300 K and 100 K using vibrating sample magnetometer (VSM) and found that the ITO nanoparticles were ferromagnetic at 100 K and 300 K. Where-as the room temperature ferromagnetism completely disappeared in Cr doped ITO nanoparticles at 100 K and 300 K.

  1. [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.

  2. Structural, photoluminescence and radioluminescence properties of Eu3+ doped La2Hf2O7 nanoparticles

    NASA Astrophysics Data System (ADS)

    Wahid, Kareem; Pokhrel, Madhab; Mao, Yuanbing

    2017-01-01

    This study presents the structural, optical, and radioluminescent characterization of newly synthesized europium-doped lanthanum hafnate (La2Hf2O7:xmol%Eu3+, x=0 to 35) nanoparticles (NPs) for use as phosphors and scintillation materials. Samples prepared through a combined co-precipitation and molten salt synthetic process were found to crystalize in the pyrochlore phase, a radiation tolerant structure related to the fluorite structure. These samples exhibit red luminescence under ultraviolet and X-ray excitation. Under these excitations, the optical intensity and quantum yield of the La2Hf2O7:xmol%Eu3+ NPs depend on the Eu3+ concentration and are maximized at 5%. It is proposed that there is a trade-off between the quenching due to defect states/cross-relaxation and dopant concentration. An optimal dopant concentration allows the La2Hf2O7:5 mol%Eu3+ NPs to show the best luminescent properties of all the samples.

  3. 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.

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

    SciTech Connect

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

    2015-11-15

    Lanthanide MOFs, [Eu(TCA)(NDC)·H{sub 2}O]{sub n} (1) and [Tb(TCA)(NDC)·H{sub 2}O]{sub n} (2), have been prepared with the mixed aromatic carboxylate ligands, namely, 4,4′,4″-tricarboxytriphenylamine (H{sub 3}TCA) and 1,4-naphthalenedicarboxylate (H{sub 2}NDC). 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 (Φ{sub overall}=11%) comparing with those of 1 (τ=0.335 ms, Φ{sub overall}=0.06%). - Graphical abstract: Synoptic: Two Ln-MOFs (Ln=Eu{sup III}, Tb{sup III}) with mixed polycarboxylate ligands present different luminescent properties. - Highlights: • Two Eu/Tb-MOFs with H{sub 3}TCA and H{sub 2}NDC ligands have been obtained. • The ancillary ligand is employed to decrease water molecule coordinate numbers. • 2displays superior quantum yield and lifetime than those of 1.

  5. 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.

  6. Photoluminescence properties of Tb3Al5O12:Ce3+ garnet synthesized by the metal organic decomposition method

    NASA Astrophysics Data System (ADS)

    Onishi, Yuya; Nakamura, Toshihiro; Adachi, Sadao

    2017-02-01

    Tb3Al5O12:Ce3+ garnet (TAG:Ce3+) phosphor was synthesized by the metal organic decomposition (MOD) method and subsequent calcination at Tc = 800-1200°C for 1 h in air. The effects of Ce3+ concentration on the phosphor properties were investigated in detail using X-ray diffraction (XRD) analysis, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and PL decay measurements. The maximum intensity in the Ce3+ yellow emission was observed at the Ce3+ concentration of ∼0.20%. PLE and PL decay measurements suggested an evidence of the energy transfer from Tb3+ to Ce3+. Calcination temperature dependence of the XRD and PL intensities yielded an energy of ∼1.5 eV both for the TAG formation in the MOD process and for the optical activation of Ce3+ in its lattice sites. Temperature dependences of the PL intensity for the TAG:Ce3+ yellow-emitting and K2SiF6:Mn4+ red-emitting phosphors were also examined for the future solid-state lighting applications at T = 20-500 K in 10-K steps. The data of TAG:Ce3+ were analyzed using a theoretical model with considering a reservoir level of Et ∼9 meV, yielding a quenching energy of Eq ∼0.35 eV, whereas the K2SiF6:Mn4+ red-emitting phosphor data yielded a value of Eq ∼1.0 eV. The schematic energy-level diagrams for Tb3+ and Ce3+ were proposed for the sake of a better understanding of these ions in the TAG host.

  7. Photoluminescence properties of the high-brightness Eu(3+)-doped KNaCa2(PO4)2 phosphors.

    PubMed

    jin, Cheng; Ma, Hengxin; Liu, Qingbo; Li, Xu; Liu, Pengfei

    2014-03-25

    A series of red-emitting phosphors Eu(3+)-doped KNaCa2(PO4)2 were synthesized by solid-state reaction, and the photoluminescence (PL) properties were also investigated. The excitation spectrum is composed of charge-transfer (CT) of Eu-O and excitation lines of Eu(3+) ions. The strongest excitation lines appeared at 393 nm. The emission spectra of KNaCa2(PO4)2:Eu(3+) phosphors exhibit five peaks assigned to the (5)D0-(7)FJ (J=0, 1, 2, 3, 4) transitions of Eu(3+) and have dominating emission peak at 621 nm under 393 nm excitation. The luminescence intensity enhanced with increasing Eu(3+) content and the emission reached the maximum intensity at x=0.02 in KNaCa2-x(PO4)2:xEu(3+). The effect of the charge compensators on the emission intensity of the phosphors was investigated. The integral intensity of the emission spectrum of KNaCa1.96(PO4)2:0.02Eu(3+), 0.02Na(+) excited at 393 nm is about 2.4 times as strong as that of Y2O3:0.05Eu(3+) commercial red phosphor. The color coordinates for KNaCa1.96(PO4)2:0.02Eu(3+),0.02Na(+) were measured. The results indicate that KNaCa2(PO4)2:Eu(3+) might be a promising phosphor for w-LEDs.

  8. Molecular dynamics study of the structures and properties of RDX/GAP propellant.

    PubMed

    Li, Miaomiao; Li, Fengsheng; Shen, Ruiqi; Guo, Xiaode

    2011-02-28

    Molecular dynamics simulations have been performed to investigate well-known energetic material cyclotrimethylene trinitramine (RDX) crystal, glycidyl azide polymer (GAP) and RDX/GAP propellant. The results show that the binding energies on different crystalline surface of RDX change in the order of (0 1 0) > (1 0 0) > (0 0 1). The interactions between RDX and GAP have been analyzed by means of pair correlation functions. The mechanical properties of RDX/GAP propellant, i.e., elastic coefficients, modulus, Cauchy pressure, and Poisson's ratio, etc., have been obtained. It is found that mechanical properties are effectively improved by adding some amounts of GAP polymer, and the overall effect of GAP on three crystalline surfaces of RDX changes in the order of (1 0 0) > (0 1 0) > (0 0 1). The energetic properties of RDX/GAP propellant have also been calculated and the results show that compared with the pure RDX crystal, the standard theoretical specific impulse (I(sp)) of RDX/GAP propellant decrease, but they are still superior to those of double base propellant. Copyright © 2010 Elsevier B.V. All rights reserved.

  9. Structural phase transitions and photoluminescence properties of oxonitridosilicate phosphors under high hydrostatic pressure

    PubMed Central

    Lazarowska, Agata; Mahlik, Sebastian; Grinberg, Marek; Li, Guogang; Liu, Ru-Shi

    2016-01-01

    Spectroscopic properties of a series of (Sr0.98-xBaxEu0.02)Si2O2N2 (0 ≤ x ≤ 0.98) compounds has been studied under high hydrostatic pressure applied in a diamond anvil cell up to 200 kbar. At ambient pressure the crystal structures of (Sr0.98-xBaxEu0.02)Si2O2N2 (0 ≤ x ≤ 0.98) are related to the ratio of strontium to barium and three different phases exists: orthorhombic Pbcn(0.78 ≤ x ≤ 0.98), triclinic P1 (0 < x ≤ 0.65) and triclinic P1 (0.65 < x < 0.78). It was found that Eu2+ luminescence reveals abrupt changes under pressure (decay time, energy and shape) which indicate the variation of the local symmetry and crystal field strength in Eu2+ sites. These changes are attributed to the reversible pressure-induced structural phase transitions of triclinic (Sr0.98-xBaxEu0.02)Si2O2N2 into orthorhombic structure. Pressure in which phase transition occurs decreases linearly with increasing of Ba composition in (Sr0.98-xBaxEu0.02)Si2O2N2 series. Additionally, very different pressure shifts of the Eu2+ luminescence in different phases of (Sr0.98-xBaxEu0.02)Si2O2N2:Eu from −40 cm−1/kbar to 0 cm−1/kbar have been observed. This effect is explained by different interaction of the Eu2+ 5d electron with the second coordination sphere around the impurity cations. PMID:27734847

  10. 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.

  11. Photoluminescence properties of Pr3+ doped Bi2ZnOB2O6 microcrystals and PMMA-based composites

    NASA Astrophysics Data System (ADS)

    Jaroszewski, K.; Chrunik, M.; Głuchowski, P.; Coy, E.; Maciejewska, B.; Jastrzab, R.; Majchrowski, A.; Kasprowicz, D.

    2016-12-01

    Photoluminescence properties of red-emitting Pr3+-doped Bi2ZnOB2O6 microcrystalline powder and PMMA-based composite materials were reported. Bi2ZnOB2O6:Pr3+ powders were synthesized by means of the modified Pechini method. The morphology and crystallographic structure of Bi2ZnOB2O6:Pr3+ microcrystals were investigated by XRD and HRTEM. The PMMA-based composite materials were prepared by embedding of Bi2ZnOB2O6:Pr3+ powder in the PMMA matrix. The vibrational properties of the powder and composite systems were investigated by μ-Raman spectroscopy. Emission spectra of the samples were measured under blue (451.6 nm) and UV (320 nm) excitation. Both, the powder and composite samples show enhancement of red emission (1D2 → 3H4) and quenching of greenish-blue luminescence from 3P0 level of Pr3+ ions after excitation in UV and VIS caused by the 3P0 ∼ 1D2 non-radiative relaxation of Pr3+ ion by low-lying charge transfer state and non-radiative de-excitation through Pr3+-Bi3+ energy transfer. The response of the powder and composite samples to pulsed excitation at 451.6 nm was measured by monitoring emission from the 1D2 level (595 nm/3P0 → 3H6 transition). The determined lifetimes τ1 and τ2 of the red emission at 595 nm (1D2 → 3H4 transition) of the composite are significantly longer in comparison to powder samples. Moreover, because of the good nonlinear optical properties of the Bi2ZnOB2O6 crystals and effective luminescence of the Pr3+-doped Bi2ZnOB2O6 powders and composites, they can be very useful as bi-functional materials in the new generation of optoelectronic devices.

  12. 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

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

    PubMed

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

    2016-04-14

    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.

  14. 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.

  15. 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

  16. 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.

  17. Influence of excitation wavelength on photoluminescence properties of CdSe/CdZnS colloidal quantum dots on micro-patterned silver films

    NASA Astrophysics Data System (ADS)

    Khan, Rizwan; Jeon, Ju-Won; Jang, Lee-Woon; Kim, Min-Kyu; Ko, Eun-Yee; Lee, Joo-In; Lee, In-Hwan

    2014-03-01

    We examined the excitation wavelength dependence of photoluminescence (PL) property in CdSe/CdZnS colloidal quantum dots (QDs) on micro-patterned silver (Ag) films (MPSFs). PL quenching of the fluorophore was observed when the excitation wavelength was out of the absorption range of MPSF substrates. In contrast, when the excitation wavelength was within the absorption spectrum range, the PL intensity on Ag films was markedly enhanced by a factor of two. It was expected that the principal causes on the PL properties of the fluorophore on Ag films would be the energy match between the incident light and the surface plasmon of Ag metal films.

  18. The relation between photoluminescence properties and gas pressure with [0001] InGaN single quantum well systems

    NASA Astrophysics Data System (ADS)

    Tsutsumi, Toshiaki; Alfieri, Giovanni; Kawakami, Yoichi; Micheletto, Ruggero

    2017-01-01

    We show for the first time that photoluminescence of InGaN single quantum wells (SQW) devices is related to the gas pressure in which the sample is immersed, also we give a model of the phenomena to suggest a possible cause. Our model shows a direct relation between experimental behavior and molecular coverage dynamics. This strongly suggests that the driving force of photoluminescence decrease is oxygen covering the surface of the device with a time dynamics that depends on the gas pressure. This aims to contribute to the understanding of the physical mechanism of the so-called optical memory effect and blinking phenomenon observed in these devices.

  19. Photoluminescence and thermoluminescence properties of Tb{sup 3+} doped K{sub 3}Gd(PO{sub 4}){sub 2} nanophosphor

    SciTech Connect

    Gupta, Palvi; Bedyal, A.K.; Kumar, Vinay; Khajuria, Y.; Lochab, S.P.; Pitale, S.S.; Ntwaeaborwa, O.M.; Swart, H.C.

    2014-12-15

    Energy level diagram of Tb{sup 3+} ion in the K{sub 3}Gd(PO{sub 4}){sub 2} host lattice. - Highlights: • First time, a detailed TL and PL study on undoped and Tb{sup 3+} doped K{sub 3}Gd(PO{sub 4}){sub 2} nanophosphor. • Combustion method was employed to synthesize the Tb{sup 3+} doped K{sub 3}Gd(PO{sub 4}){sub 2} nanophosphor. • Mechanism of excitation and emission in undoped and Tb{sup 3+} doped K{sub 3}Gd(PO{sub 4}){sub 2} nanophosphor was given. - Abstract: Tb{sup 3+} doped nanoparticulate K{sub 3}Gd(PO{sub 4}){sub 2} phosphor was prepared by combustion method using urea as a fuel. The structure, optical and luminescent properties of the phosphor were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and thermoluminescence (TL) spectroscopy. In undoped K{sub 3}Gd(PO{sub 4}){sub 2}, the excitation and emission peaks at 273 nm and 323 nm belongs to the {sup 8}S{sub 7/2} → {sup 6}I{sub J(J=7/2)} and {sup 6}P{sub J(J=7/2)} → {sup 8} S{sub 7/2} transitions of Gd{sup 3+} while green emission was observed in the Tb{sup 3+} doped K{sub 3}Gd(PO{sub 4}){sub 2}. TL study was carried out after exposing the samples to γ-radiations (0.1–5 kGy) in the K{sub 3}Gd(PO{sub 4}){sub 2}:Tb{sup 3+} (1.5 mol%). The calculated kinetic parameters were compared with different methods. The band gap of the phosphor was estimated as 5.80 eV. The green shade of the Tb{sup 3+} ion with the CIE coordinates (x, y) as (0.29, 0.54) was in good agreement with the well known green phosphors.

  20. Thermoluminescence and photoluminescence properties of NaCl:Mn, NaCL:Cu nano-particles produced using co-precipitation and sono-chemistry methods

    NASA Astrophysics Data System (ADS)

    Mehrabi, M.; Zahedifar, M.; Saeidi-Sogh, Z.; Ramazani-Moghaddam-Arani, A.; Sadeghi, E.; Harooni, S.

    2017-02-01

    The NaCl: Cu and NaCl: Mn nanoparticles (NPs) were produced by co-precipitation and sono-chemistry methods and their thermoluminescence (TL) and photoluminescence (PL) properties were studied. By decreasing the particles size a considerable increase in sensitivity of the samples to high dose gamma radiation was observed. The NPs produced by sono-chemistry method have smaller size, homogeneous structure, more sensitivity to high gamma radiation and less fading than of those produced by co-precipitation method.

  1. Photoluminescence and electrical properties of Eu-doped (Na0.5Bi0.5)TiO3 ferroelectric single crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Haiwu; Zhao, Xiangyong; Deng, Hao; Chen, Chao; Lin, Di; Li, Xiaobing; Yan, Jun; Luo, Haosu

    2014-02-01

    Eu3+-doped Na0.5Bi0.5TiO3 (Eu:NBT) single crystals were grown by a top-seeded solution growth method. Photoluminescence emission and excitation spectra of Eu:NBT were investigated. The two transitions in 7F0 → 5D0 excitation spectra reveal that Eu3+ ions were incorporated into two adjacent crystallographic sites in NBT, i.e., Bi3+ and Na+ sites. The former has a symmetrical surrounding, while the later has a disordered environment, which was confirmed by decay curve measurements. The dielectric dispersion behavior was depressed and the piezoelectric and ferroelectric properties were improved after Eu doping.

  2. Photoluminescence Properties of β-Ga2O3 Thin Films Produced by Ion-Plasma Sputtering

    NASA Astrophysics Data System (ADS)

    Bordun, O. M.; Bordun, B. O.; Kukharskyy, I. Yo.; Medvid, I. I.

    2017-03-01

    Photoluminescence and photoexcitation spectra of β-Ga2O3 thin films prepared by high-frequency ion-plasma sputtering in an Ar atmosphere were investigated. Photoluminescence spectra were deconvoluted by the Alentsev—Fock method into ultimate constituents. The nature of two strong bands with maxima at 2.95 and 3.14 eV and two weak bands with maxima at 3.90 and 4.25 eV was discussed. The two strong bands were attributed to an associate originating from the interaction of oxygen and gallium vacancies; the weak ones, recombination of excitons in quantum wells formed by acceptor clusters. It was found that the damping time constant for the 3.14-eV band was 105 μs; for the 2.95-eV band, 114 μs. The similarity of the decay time constants for these bands confirmed their relationship to a common associate.

  3. The photoluminescence, drug delivery and imaging properties of multifunctional Eu3+/Gd3+ dual-doped hydroxyapatite nanorods.

    PubMed

    Chen, Feng; Huang, Peng; Zhu, Ying-Jie; Wu, Jin; Zhang, Chun-Lei; Cui, Da-Xiang

    2011-12-01

    The design and synthesis of multifunctional systems with high biocompatibility are very significant for the future of clinical applications. Herein, we report a microwave-assisted rapid synthesis of multifunctional Eu(3+)/Gd(3+) dual-doped hydroxyapatite (HAp) nanorods, and the photoluminescence (PL), drug delivery and in vivo imaging of as-prepared Eu(3+)/Gd(3+) doped HAp nanorods. The photoluminescent and magnetic multifunctions of HAp nanorods are realized by the dual-doping with Eu(3+) and Gd(3+). The PL intensity of doped HAp nanorods can be adjusted by varying Eu(3+) and Gd(3+) concentrations. The magnetization of doped HAp nanorods increases with the concentration of doped Gd(3+). The as-prepared Eu(3+)/Gd(3+)-doped HAp nanorods exhibit inappreciable toxicity to the cells in vitro. More importantly, the Eu(3+)/Gd(3+)-doped HAp nanorods show a high drug adsorption capacity and sustained drug release using ibuprofen as a model drug, and the drug release is governed by a diffusion process. Furthermore, the noninvasive visualization of nude mice with subcutaneous injection indicates that the Eu(3+)/Gd(3+)-doped HAp nanorods with the photoluminescent function are suitable for in vivo imaging. In vitro and in vivo imaging tests indicate that Eu(3+)/Gd(3+)-doped HAp nanorods have a potential in applications such as a multiple-model imaging agent for magnetic resonance (MR) imaging, photoluminescence imaging and computed tomography (CT) imaging. The Eu(3+)/Gd(3+) dual-doped HAp nanorods are promising for applications in the biomedical fields such as multifunctional drug delivery systems with imaging guidance.

  4. Photoluminescent and Electroluminescent Properties of Cd sub 0.95 Mn sub 0.05 Se Electrodes.

    DTIC Science & Technology

    1984-09-28

    electroluminescence, cadmium manganese selenide electrodes, photoelectrochemistry, dead-layer model 10. ABSTRACT (Contlave on Fvors&a side 110080080Y d...to map the electric field in theme solids, grown by a modified Bridgman method. , DD P1’H"I. 1473 CITION Of I NOV 66 IS OSSOLCTE nlssfe 012.L.014501...used to map the electric field in these solids, grown by a modified Bridgman method. 1. INTRODUCTION Photoluminescence (PL) and electroluminescence (EL

  5. [Preparation and Photoluminescent Properties of Ce³⁺-Activated LaPO₄ Nanocrystals and Core/Shell Structure].

    PubMed

    Li, Zhen-ya; Huang, Shi-ming; Gu, Mu; Liu, Xiao-lin

    2015-11-01

    Hydrophobic, monodisperse LaPO₄: Ce³⁺ nanoparticles, LaPO₄:Ce³⁺/LaPO₄ and LaPO₄:Ce³⁺/LaPO₄: Ce³⁺/ LaPO₄ core/shell structure nanocrystals were synthesized via a high-temperature organic solution approach. The as-synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and photoluminescence spectroscopy (PL). The results show that: all the samples are a monoclinic phase, Because of the size small nanoparticles, the diffraction peaks of the sample occurs width phenomenon. The LaPO₄:Ce³⁺ nano- crystals exhibits the characteristic emission of Ce³⁺ ions, the photoluminescence intensity increases first and then decreases with the increasing doping concentration of Ce³⁺ ions, and the best doping amount is 6 at %, with the increasing doping amount, the photoluminescence intensity decreases which may caused by the concentration quenching. Compared to LaPO₄:Ce³⁺ nanoparti- cles, the photoluminescence intensity of LaPO₄:Ce³⁺/LaPO₄ and LaPO₄: Ce³⁺/LaPO₄: Ce³⁺/LaPO₄ core/shell structure nanocrystals improves about 41% and 95% respectively, this may be a synergy of larger particle size of nanocrystals and surface passivation effect. FTIR spectra data shows that the absorption peak at 1545 and 1461 cm⁻¹ corresponded to the asymmetric and symmetric stretching vibration of --COO⁻, the separation, Δ, between the two peaks is 84 cm⁻¹, The mechanism of the sample surface modification by the organics might be that the oxygen atoms of the carboxyl are coordinated with the lanthunum ions by a bidentate mode.

  6. Tough photoluminescent hydrogels doped with lanthanide.

    PubMed

    Wang, Mei Xiang; Yang, Can Hui; Liu, Zhen Qi; Zhou, Jinxiong; Xu, Feng; Suo, Zhigang; Yang, Jian Hai; Chen, Yong Mei

    2015-03-01

    Photoluminescent hydrogels have emerged as novel soft materials with potential applications in many fields. Although many photoluminescent hydrogels have been fabricated, their scope of usage has been severely limited by their poor mechanical performance. Here, a facile strategy is reported for preparing lanthanide (Ln)-alginate/polyacrylamide (PAAm) hydrogels with both high toughness and photoluminescence, which has been achieved by doping Ln(3+) ions (Ln = Eu, Tb, Eu/Tb) into alginate/PAAm hydrogel networks, where Ln(3+) ions serve as both photoluminescent emitters and physical cross-linkers. The resulting hydrogels exhibit versatile advantages including excellent mechanical properties (∼ MPa strength, ≈ 20 tensile strains, ≈ 10(4) kJ m(-3) energy dissipation), good photoluminescent performance, tunable emission color, excellent processability, and cytocompatibility. The developed tough photoluminescent hydrogels hold great promises for expanding the usage scope of hydrogels.

  7. Photoluminescent properties of white-light-emitting Li6Y(BO3)3:Dy3+ phosphor

    NASA Astrophysics Data System (ADS)

    Fawad, U.; Kim, H. J.; Khan, Sajid; Khan, Matiullah; Ali, Luqman

    2016-12-01

    In this study, lithium yttrium borate (LYBO) phosphor was doped with various concentrations of trivalent dysprosium ions. To produce these phosphors, the raw materials were sintered. The phase conformation, crystallinity, grain size, and overall morphology of the synthesized phosphors were studied with X-ray diffraction and scanning electron microscopy. The optimized LYBO phosphor, i.e., the LYBO phosphor that exhibited the highest X-ray- and ultraviolet (UV)-induced photoluminescent intensities, had a Dy3+ concentration of 4 mol%. Photoluminescence analysis showed that this phosphor could be easily excited with near-UV light (300-400 nm). The dominant photoluminescence bands were found in the blue (480 nm) and yellow (577 nm) regions of the visible spectrum. The light yield of the X-ray-induced luminescence of the optimized Li6Y(BO3)3:Dy3+ was found to be 66% of that of the commercially available X-ray imaging material, Gd2O2S:Tb3+ (GOS). The chromaticity coordinates of the Li6Y(BO3)3:Dy3+ phosphor were x = 0.34 and y = 0.32, which agree well with achromatic white (x = 0.33, y = 0.33). The results of this study show that the synthesized Li6Y(BO3)3:Dy3+ phosphor could be used as X-ray imaging material.

  8. Syntheses, structures and photoluminescent properties of three d{sup 10} coordination architectures based on in-situ 1,3,5-triazine derivatives

    SciTech Connect

    Xiao, Changyu; Li, Yamin; Lun, Huijie; Cui, Caiyan; Xu, Yanqing

    2013-12-15

    In the presence of aromatic carboxylic acids, three new d{sup 10} transition metal coordination polymers, [Ag(PAHT)]{sub n}(1), [Ag{sub 2}(HCA)]{sub n}(2) and [Cu{sub 6}(CA){sub 2}(H{sub 2}O)]{sub n}(3) (HPAHT=2-phenyl-4-amino-6-hydroxy-1,3,5-triazine, H{sub 3}CA=cyanuric acid) have been synthesized based on in-situ 1,3,5-triazine derivatives resulting from 2,4-diamino-6-phenyl-1,3,5-triazine, 2-chloro-4,6-diamino-1,3,5-triazine and melamine under hydrothermal conditions. Complexes 1–3 have been characterized by single-crystal X-ray diffraction, IR spectra, elemental analysis and thermogravimetric analysis (TGA). The compound 1 exhibits a uninodal three-connected 3D network with a rare lig LiGe type topology, which contains right-handed and left-handed [Ag(PAHT)]{sub n} helical chains. For compound 2, the 3D network is comprised of 2D sheet by strongly Ag–O and weakly Ag(I)…Ag(I) interactions. In compound 3, it is infrequently observed that dodecanuclear copper(I) units as secondary building units (SBUs) construct 3D network by the ligands CA{sup 3−} with a rare uninodal 10-connected bct topology (3{sup 12}.4{sup 28}.5{sup 5}). The photoluminescent properties of three compounds have also been measured. - Graphical abstract: Three d{sup 10} transition metal coordination polymers 1–3 have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, IR spectra, elemental analysis, photoluminescent spectra and thermogravimetric analysis (TGA). - Highlights: • The compound 1 exhibits a new 3D network with two kinds of single helical chains. • New 3D d{sup 10} transition metal coordination polymers. • The photoluminescent properties have been measured.

  9. Development of Intrinsically Photoluminescent and Photostable Polylactones

    PubMed Central

    Xie, Zhiwei; Zhang, Yi; Liu, Li; Weng, Hong; Mason, Ralph P.; Tang, Liping; Nguyen, Kytai T.; Hsieh, Jer-Tsong

    2014-01-01

    A method of introducing intrinsically photoluminescent properties to biodegradable polymer was introduced, exemplified by the synthesis of intrinsically photoluminescent polylactones that enable non-invasively monitoring and tracking material degradation in vivo in real-time and the formation of theranostic nanoparticles for cancer imaging and drug delivery. PMID:24668888

  10. Ab-initio study of structural, electronic, and transport properties of zigzag GaP nanotubes.

    PubMed

    Srivastava, Anurag; Jain, Sumit Kumar; Khare, Purnima Swarup

    2014-03-01

    Stability and electronic properties of zigzag (3 ≤ n ≤ 16) gallium phosphide nanotubes (GaP NTs) have been analyzed by employing a systematic ab-intio approach based on density functional theory using generalized gradient approximation with revised Perdew Burke Ernzerhoff type parameterization. Diameter dependence of bond length, buckling, binding energy, and band gap has been investigated and the analysis shows that the bond length and buckling decreases with increasing diameter of the tube, highest binding energy of (16, 0) confirms this as the most stable amongst all the NTs taken into consideration. The present GaP NTs shows direct band gap and it increases with diameter of the tubes. Using a two probe model for (4, 0) NT the I-V relationship shows an exponential increase in current on applying bias voltage beyond 1.73 volt.

  11. Structure and photoluminescence properties of Ce0.5Zr0.5O2:Eu3+ nanoparticles synthesized by hydrothermal method

    NASA Astrophysics Data System (ADS)

    Ozawa, Masakuni; Yoshimura, Yusuke; Kobayashi, Katsutoshi

    2017-01-01

    Eu3+-doped Ce0.5Zr0.5O2 nanocrystals were prepared by a hydrothermal method. The structural and optical properties of the samples were characterized by X-ray diffraction, Raman scattering and photoluminescence spectra. No luminescence was observed for Ce0.5Zr0.5O2, while Ce0.5Zr0.5O2:Eu3+ nanoparticles as-prepared and calcined at 400 °C showed emission due to Eu3+. The emission spectrum of the Eu3+ site shows that the total intensity decreases with increasing concentration of Eu3+ from 1 to 10% in Ce0.5Zr0.5O2. The broad band in the excitation spectrum of calcined Ce0.5Zr0.5O2:Eu3+ originates from the charge transfer (CT) transition. The local distortion and the asymmetry factor around the Eu3+ centers were discussed with the Raman and photoluminescence spectra. The present study provides both knowledge expected to lead to novel nanocrystal phosphor materials and a useful measure for analyzing the catalytic properties of nanocrystalline Ce0.5Zr0.5O2.

  12. Low-temperature growth of well-aligned ZnO nanorods/nanowires on flexible graphite sheet and their photoluminescence properties

    SciTech Connect

    Zhong, Guo; Kalam, Abul; Al-Shihri, Ayed Sad; Su, Qingmei; Li, Jie; Du, Gaohui

    2012-06-15

    Highlights: ► Well-aligned ZnO nanostructures were grown on flexible graphite sheets at 500–650 °C. ► ZnO nanostructures are formed via self-catalytic vapor–solid process assisted by immiscibility of ZnO with graphite. ► The ZnO nanostructures show intensive green emission. ► The photoluminescence property can be easily tuned by changing growth condition or annealing treatment. -- Abstract: We have grown large-scale well-aligned ZnO nanorods/nanowires on commercial flexible graphite sheet (FGS) at low temperature via chemical vapor deposition method. The products were characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. The effects of the growth temperature and oxygen flow rate on the morphology of ZnO nanostructures have been investigated. The growth mechanism of ZnO is found to be a self-catalytic vapor–solid process assisted by the immiscibility of ZnO with graphite. The as-grown ZnO/FGS products show strong green emission and their photoluminescence properties can be tuned by changing growth condition or annealing treatment.

  13. Study of structural, optical and photoluminescence properties of indium-doped zinc sulfide thin films for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Jrad, Abdelhak; Ben Nasr, Tarek; Turki-Kamoun, Najoua

    2015-12-01

    In the present work, we have deposited indium-doped zinc sulfide (ZnS:In) thin films by chemical bath deposition technique (CBD). The structural properties studied by X-ray diffraction indicate that ZnS:In has a cubic structure with an average crystallite size 4.7-11.0 nm. Transmission and reflection spectra reveal the presence of interference fringes indicating thickness uniformity and surface homogeneity of deposited material. All the films were transparent in the visible and infrared regions (⩾60%), which allows us to use this material as an optical window or a buffer layer in solar cells. The obtained band gap energy Eg is in the range of 3.70-3.76 eV. The refractive index and thickness of ZnS:In thin films was calculated using envelope method. The variation of the refractive index along the Cauchy distribution was observed in all ZnS:In thin films. The analysis of the refractive index data through the Wemple-DiDomenico model leads to the single oscillator energy (E0) and the dispersion energy (Ed).

  14. Theoretical study of optical properties of anti phase domains in GaP

    NASA Astrophysics Data System (ADS)

    Tea, E.; Vidal, J.; Pedesseau, L.; Cornet, C.; Jancu, J.-M.; Even, J.; Laribi, S.; Guillemoles, J.-F.; Durand, O.

    2014-02-01

    III-V/Si heterostructures are currently investigated for silicon photonics and solar energy conversion. In particular, dilute nitride alloy GaAsPN grown on a GaP/Si platform exhibits lattice match with Si and an optimal band gap configuration for tandem solar cell devices. However, monolithic "coherent" growth of the GaP thin layer on Si suffers from the nucleation of extended structural defects, which can hamper device operation as well as the GaP/Si interface level and through their propagation inside the overall heterostructure. However, the effect of such structural defects on optical and transport properties is actually not well understood in details. In this letter, we investigate the anti phase domains defect (also called inversion domains) by means of ab initio calculations giving insights into the alteration of optical and transport properties of GaP due to the defective GaP/Si interface.

  15. Theoretical study of optical properties of anti phase domains in GaP

    SciTech Connect

    Tea, E.; Vidal, J.; Laribi, S.; Guillemoles, J.-F.; Pedesseau, L.; Cornet, C.; Jancu, J.-M.; Even, J.; Durand, O.

    2014-02-14

    III-V/Si heterostructures are currently investigated for silicon photonics and solar energy conversion. In particular, dilute nitride alloy GaAsPN grown on a GaP/Si platform exhibits lattice match with Si and an optimal band gap configuration for tandem solar cell devices. However, monolithic “coherent” growth of the GaP thin layer on Si suffers from the nucleation of extended structural defects, which can hamper device operation as well as the GaP/Si interface level and through their propagation inside the overall heterostructure. However, the effect of such structural defects on optical and transport properties is actually not well understood in details. In this letter, we investigate the anti phase domains defect (also called inversion domains) by means of ab initio calculations giving insights into the alteration of optical and transport properties of GaP due to the defective GaP/Si interface.

  16. Photoluminescent Properties of Y2O3:Eu3+ Phosphors Prepared via Urea Precipitation in Non-Aqueous Solution

    SciTech Connect

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

    2004-08-02

    Europium-doped yttrium oxide phosphors were obtained by firing precursors prepared by urea precipitation in ethanol and ethylenediamine. The precipitation in non-aqueous solution was carried out in an autoclave at 150 C to allow the decomposition of urea. The photoluminescent intensities of the phosphors prepared in ethanol and ethylenediamine increased by about 30% compared to that of the phosphor prepared by the conventional urea homogeneous precipitation in aqueous solution. Amorphous carbonates and amorphous hydroxides/carbonates mixtures were identified as precursors from ethanol and ethylenediamine, respectively. The morphology and particle size were studied by SEM and dynamic laser scattering method.

  17. Control of Photoluminescence of Carbon Nanodots via Surface Functionalization using Para-substituted Anilines

    PubMed Central

    Kwon, Woosung; Do, Sungan; Kim, Ji-Hee; Seok Jeong, Mun; Rhee, Shi-Woo

    2015-01-01

    Carbon nanodots (C-dots) are a kind of fluorescent carbon nanomaterials, composed of polyaromatic carbon domains surrounded by amorphous carbon frames, and have attracted a great deal of attention because of their interesting properties. There are still, however, challenges ahead such as blue-biased photoluminescence, spectral broadness, undefined energy gaps and etc. In this report, we chemically modify the surface of C-dots with a series of para-substituted anilines to control their photoluminescence. Our surface functionalization endows our C-dots with new energy levels, exhibiting long-wavelength (up to 650 nm) photoluminescence of very narrow spectral widths. The roles of para-substituted anilines and their substituents in developing such energy levels are thoroughly studied by using transient absorption spectroscopy. We finally demonstrate light-emitting devices exploiting our C-dots as a phosphor, converting UV light to a variety of colors with internal quantum yields of ca. 20%. PMID:26218869

  18. Elucidating Quantum Confinement in Graphene Oxide Dots Based On Excitation-Wavelength-Independent Photoluminescence.

    PubMed

    Yeh, Te-Fu; Huang, Wei-Lun; Chung, Chung-Jen; Chiang, I-Ting; Chen, Liang-Che; Chang, Hsin-Yu; Su, Wu-Chou; Cheng, Ching; Chen, Shean-Jen; Teng, Hsisheng

    2016-06-02

    Investigating quantum confinement in graphene under ambient conditions remains a challenge. In this study, we present graphene oxide quantum dots (GOQDs) that show excitation-wavelength-independent photoluminescence. The luminescence color varies from orange-red to blue as the GOQD size is reduced from 8 to 1 nm. The photoluminescence of each GOQD specimen is associated with electron transitions from the antibonding π (π*) to oxygen nonbonding (n-state) orbitals. The observed quantum confinement is ascribed to a size change in the sp(2) domains, which leads to a change in the π*-π gap; the n-state levels remain unaffected by the size change. The electronic properties and mechanisms involved in quantum-confined photoluminescence can serve as the foundation for the application of oxygenated graphene in electronics, photonics, and biology.

  19. Anisotropic Effective Mass, Optical Property, and Enhanced Band Gap in BN/Phosphorene/BN Heterostructures.

    PubMed

    Hu, Tao; Hong, Jisang

    2015-10-28

    Phosphorene is receiving great research interests because of its peculiar physical properties. Nonetheless, the phosphorus has a trouble of degradation due to oxidation. Hereby, we propose that the electrical and optical anisotropic properties can be preserved by encapsulating into hexagonal boron nitride (h-BN). We found that the h-BN contributed to enhancing the band gap of the phosphorene layer. Comparing the band gap of the pristine phosphorene layer, the band gap of the phosphorene/BN(1ML) system was enhanced by 0.15 eV. It was further enhanced by 0.31 eV in the BN(1ML)/phosphorene/BN(1ML) trilayer structure. However, the band gap was not further enhanced when we increased the thickness of the h-BN layers even up to 4 MLs. Interestingly, the anisotropic effective mass and optical property were still preserved in BN/phosphorene/BN heterostructures. Overall, we predict that the capping of phosphorene by the h-BN layers can be an excellent solution to protect the intrinsic properties of the phosphorene.

  20. Synthesis and photoluminescence properties of Eu2+ activated CaO ceramic powders for near-ultraviolet chip based white light emitting diodes

    NASA Astrophysics Data System (ADS)

    Hao, Zhendong; Wang, Ying; Zhang, Liangliang; Pan, Guohui; Zhang, Xia; Wu, Huajun; Luo, Yongshi; Zhang, Jiahua

    2017-09-01

    In this paper, we synthesized series of Eu2+ activated CaO ceramic powders by conventional solid state reaction. Using NH4Cl as a reducing additives, the Eu3+ has been successfully reduced to Eu2+. An intense blue emission peaked at 460 nm from Eu2+ was observed. The luminescent intensity of the doping-optimized CaO:Eu2+ sample can be as high as 106% of commercial BAM blue phosphor under 400 nm near-ultraviolet (NUV) excitation. The effect of Eu2+ and NH4Cl contents on photoluminescence properties and crystal phase formation have been investigated, respectively. The thermal stable property which is an important performance for LED application has also been measured. The emission intensity at 120 °C can maintain 94% of that at room temperature. Our results suggest that CaO: Eu2+ ceramic powder could be used as a promising blue emitting phosphor for NUV chip based white LEDs.

  1. Structural, optical and luminescence properties of Dy3+ doped bismuth phosphate glasses: Insights from 31P MAS NMR, absorption and photoluminescence

    NASA Astrophysics Data System (ADS)

    Damodaraiah, S.; Prasad, V. Reddy; Ratnakaram, Y. C.

    2017-05-01

    An investigation was carried out to observe structural and optical properties of 0.5 mol% Dy3+ doped different compositions of bismuth phosphate glasses (5, 10, 15 and 20 mol% Bi2O3). The structural characterization was accomplished by X-ray diffraction (XRD), 31P magic angle spin nuclear magnetic resonance (MAS NMR) spectroscopy. The optical properties were studied using absorption and photo luminescence (PL) spectroscopy. Judd-Ofelt intensity parameters Ωλ (λ=2, 4 and 6) were evaluated from absorption spectra. From photoluminescence spectra, experimental branching ratios (βexp) and stimulated emission cross-sections (σP) were calculated. The decay profiles for 4F9/2 level were recorded and were fit exponential. The obtained results show the prepared Dy3+ doped bismuth phosphate glasses might be useful as good optical material for yellow emission.

  2. Photoluminescence, enhanced ferroelectric, and dielectric properties of Pr{sup 3+}-doped SrBi{sub 2}Nb{sub 2}O{sub 9} multifunctional ceramics

    SciTech Connect

    Zou, Hua; Yu, Yao; Li, Jun; Cao, Qiufeng; Wang, Xusheng; Hou, Junwei

    2015-09-15

    Pr{sup 3+}-doped SrBi{sub 2}Nb{sub 2}O{sub 9} (SBN) multifunctional ceramics were synthesized by the conventional solid state method. The photoluminescence (PL) excitation and emission spectra, enhanced ferroelectric and dielectric properties were investigated. The X-ray diffraction (XRD) and FESEM analyses indicated that the samples were simple phase and uniform flake-structure. Under the 250–350 nm ultraviolet (UV) excitations, the red emission was obtained and the optimal emission intensity was investigated when Pr doping level was 0.005 mol. With the increasing of the Pr{sup 3+} ion contents, the ferroelectric properties were enhanced obviously. As a new multifunctional material, the Pr{sup 3+}-doped SBN ceramics could be used for a wide range of application, such as integrated electro-optical devices.

  3. Photoluminescence properties of rare-earth-doped (Er³⁺,Yb³⁺) Y₂O₃ nanophosphors by a combustion synthesis method.

    PubMed

    Kaur, Manmeet; Bisen, D P; Brahme, N; Singh, Prabhjot; Sahu, I P

    2016-05-01

    In this work, we report the synthesis of Y2O3:Er(3+), Y2O3:Yb(3+) and Y2O3:Er(3+),Yb(3+) nanophosphors by the combustion synthesis method using urea as fuel. The doping agents were incorporated in the form of erbium nitrate and ytterbium nitrate. X-Ray diffraction (XRD) patterns revealed that the synthesized particles have a body-centered cubic structure with space group Ia-3. The photoluminescence (PL) properties were investigated after UV and infrared irradiation at room temperature. A strong characteristic emission of Er(3+) and Yb(3+) ions was identified, and the influence of doping concentration on the PL properties was systematically studied. Energy transfer from Yb(3+) to Er(3+) ions was observed in Y2O3 nanophosphors. The obtained result may be useful in potential applications such as bioimaging. Copyright © 2015 John Wiley & Sons, Ltd.

  4. High-temperature photoluminescence of CdSe/CdS core/shell nanoheterostructures.

    PubMed

    Diroll, Benjamin T; Murray, Christopher B

    2014-06-24

    The steady-state and time-resolved photoluminescence properties of CdSe/CdS heterostructures are studied as a function of temperature from 300 to 600 K. The emission properties of samples are found to behave similarly to bulk CdSe, with the samples maintaining high color purity and a slightly contracting band gap at elevated temperature. Photoluminescence from CdSe/CdS samples is maintained with high stability over prolonged illumination and multiple heating and cooling cycles. Structures synthesized with variation in the core and the shell dimensions show that the preservation of emission intensity at high temperature depends strongly on the microscopic structure of the samples. For samples synthesized by seeded growth, the size of the CdSe core is highly correlated with the fraction of preserved sample photoluminescence intensity at high temperature. Temperature-dependent lifetime data suggest that the core structure predicts the stability of photoluminescence at elevated temperatures by controlling the radiative rate. The rate of electron capture, for which the volume fraction of the core is a structural proxy, underpins the ability for radiative processes to compete with thermally induced nonradiative decay pathways. Heterostructures synthesized below 200 °C using highly reactive organometallic precursors show markedly lower thermal stability than samples prepared by seeded growth at 360 °C, suggesting that the temperature of nanocrystal synthesis has direct consequences for the thermal stability of photoluminescence.

  5. Synthesis, characterization and photoluminescence properties of Bi3+ co-doped CaSiO3:Eu3+ nanophosphor

    NASA Astrophysics Data System (ADS)

    Madesh Kumar, M.; Hari Krishna, R.; Nagabhushana, B. M.; Shivakumara, C.

    2015-03-01

    Ceramic luminescent powders with the composition Ca0.96-xEu0.04BixSiO3 (x = 0.01-0.05) were prepared by solution combustion method. The nanopowders are characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and photoluminescence (PL) techniques. PXRD patterns of calcined (950 °C for 3 h) Ca0.96-xEu0.04BixSiO3 powders exhibit monoclinic phase with mean crystallite sizes ranging from 28 to 48 nm. SEM micrographs show the products are foamy, agglomerated and fluffy in nature due to the large amount of gases liberated during combustion reaction. TEM micrograph shows the crystalline characteristics of the nanoparticles. Upon 280 nm excitation, the photoluminescence of the Ca0.96-xEu0.04BixSiO3 particles show red emission at 611 nm corresponding to 5D0→7F2 transition. It is observed that PL intensity increases with Bi3+ concentration. Our work demonstrates very interesting energy transfer from Bi3+ to Eu3+ in CaSiO3 host.

  6. Warm white light emitting ThO{sub 2}:Sm{sup 3+} nanorods: Cationic surfactant assisted reverse micellar synthesis and Photoluminescence properties

    SciTech Connect

    Gupta, Santosh K.; Gupta, Ruma; Natarajan, V.; Godbole, S.V.

    2014-01-01

    Graphical abstract: - Highlights: • ThO{sub 2}:Sm{sup 3+} nanoparticles have been synthesized using cationic surfactant assisted reverse micellar route. • HRTEM shows the formation of thoria nanorods. • Photoluminescence investigation shows host as well as samarium ion emission. • Time resolved fluorescence spectroscopy shows the presence of two types of samarium ion in thoria host. - Abstract: Sm{sup 3+} activated thorium oxide nanorods were synthesized by cationic surfactant assisted reverse micellar route. Phase purity, morphological and luminescent properties were investigated by X-ray diffraction, high resolution transmission electron microscopy and photoluminescence spectroscopy. Upon UV light excitation (245 nm), ThO{sub 2}:Sm{sup 3+} exhibited host emission at 447 nm, along with characteristic emission lines of Sm{sup 3+} at 569, 609, 662 and 716 nm. Lifetime spectroscopy shows the presence of two types of Sm{sup 3+} (τ = 1.1 ms and 4.9 ms) with different asymmetric ratios.

  7. Photoluminescent properties of novel rare earth organic-inorganic nanocomposite with TiO2 modified silica via double crosslinking units.

    PubMed

    Zhao, Yan; Yan, Bing

    2012-01-01

    A series of novel organic/inorganic rare earth (europium, terbium) hybrid materials through the coordination bond and covalent bond are synthesized and form an inorganic Si-O-Si by the sol-gel process. Mercapto-functionalized 4-mercaptobenzoic acid (MBA-Si) is obtained by using MBA and 3-(triethoxysilyl)-propyl isocyanate (TESPIC) as an organic bridge molecule, and then the carboxyl group of the precursor MBA-Si is used to modify the titanium dioxide, so as to sensitize the luminescence of rare earth ions. CdS-TiO(2) is added to observe the influence of photoluminescence. 3-mercaptopropyltrimethoxysilane (MPS) is also used to modify the CdS quantum dot and obtain MPS functionalized MPS-CdS nanocomposite. These multicomponent hybrids with double cross-linking siloxane (MBA-Si) covalently bonding MPS-CdS are characterized. Subsequently, 1,10-phenanthroline (Phen) and 2,2,-bipyridyl (Bipy) as the assistant ligands together with water molecules are introduced into the rare earth hybrid system. The FT-IR, X-ray diffraction, UV-Vis, thermogravimetry and especially the photoluminescence properties of them are studied in detail. © 2011 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2011 The American Society of Photobiology.

  8. Structural study, 31P NMR and europium photoluminescence properties of a new synthetic fillowite-type phosphate: Na3SrMg11(PO4)9

    NASA Astrophysics Data System (ADS)

    Boukhris, Amal; Ben Hamed, Teycir; Glorieux, Benoit; Ben Amara, Mongi

    2017-05-01

    A new phosphate compound, Na3SrMg11(PO4)9 was synthesized as single crystals by flux method and as powdered sample by Pechini technique and investigated by X-ray diffraction, 31P NMR and photoluminescence spectroscopies. This compound crystallizes in the rhombohedral space group R 3 bar and its equivalent hexagonal cell has the following parameters: a = 14.941(1) Ǻ, c = 42.478(2) Ǻ and Z = 12. The structure consisted of MgOx (x = 5,6), NaOx (x = 6,7) and (Na,Sr)Ox (x = 8,9) polyhedra which are linked either directly through common corners, edges and faces and by means of the PO4 tetrahedra via common corners and edges, giving rise to a three-dimensional framework, similar to that of the fillowite-like structure. 31P NMR spectroscopy confirmed the presence of six distinct phosphors sites in the structure. Finally, strontium was partially substitute by divalent europium in order to examine whether this material could be used in optical applications. Optical studies were performed on the Na3Sr0.98Eu2+0.02Mg11(PO4)9 compound. The photoluminescence are consistent with the crystal structural and show various properties as a function of the excitation wavelength.

  9. Controlled synthesis, characterization and photoluminescence property of olive-like tetragonal α-Nd{sub 2}(MoO{sub 4}){sub 3}

    SciTech Connect

    Zhang, Youjin; Zheng, Ao; Yang, Xiaozhi; He, Hongmei; Fan, Yun

    2012-09-15

    Highlights: ► The olive-like tetragonal α-Nd{sub 2}(MoO{sub 4}){sub 3} was gained with EDTA assisted hydrothermal method. ► The product was characterized by XRD, XPS, FTIR, FESEM, and PL. ► The possible formation mechanism for olive-like α-Nd{sub 2}(MoO{sub 4}){sub 3} was proposed. ► The PL in visible region of the olive-like α-Nd{sub 2}(MoO{sub 4}){sub 3} was studied. -- Abstract: The olive-like tetragonal α-Nd{sub 2}(MoO{sub 4}){sub 3} was obtained by a convenient and facile complex agent assisted hydrothermal method. The product was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FESEM) and photoluminescence (PL). The possible formation mechanism of the olive-like α-Nd{sub 2}(MoO{sub 4}){sub 3} was proposed. The photoluminescence property in visible region of the olive-like tetragonal α-Nd{sub 2}(MoO{sub 4}){sub 3} was studied.

  10. Temperature-Driven Structural and Morphological Evolution of Zinc Oxide Nano-Coalesced Microstructures and Its Defect-Related Photoluminescence Properties.

    PubMed

    Lim, Karkeng; Abdul Hamid, Muhammad Azmi; Shamsudin, Roslinda; Al-Hardan, N H; Mansor, Ishak; Chiu, Weesiong

    2016-04-20

    In this paper, we address the synthesis of nano-coalesced microstructured zinc oxide thin films via a simple thermal evaporation process. The role of synthesis temperature on the structural, morphological, and optical properties of the prepared zinc oxide samples was deeply investigated. The obtained photoluminescence and X-ray photoelectron spectroscopy outcomes will be used to discuss the surface structure defects of the prepared samples. The results indicated that the prepared samples are polycrystalline in nature, and the sample prepared at 700 °C revealed a tremendously c-axis oriented zinc oxide. The temperature-driven morphological evolution of the zinc oxide nano-coalesced microstructures was perceived, resulting in transformation of quasi-mountain chain-like to pyramidal textured zinc oxide with increasing the synthesis temperature. The results also impart that the sample prepared at 500 °C shows a higher percentage of the zinc interstitial and oxygen vacancies. Furthermore, the intensity of the photoluminescence emission in the ultraviolet region was enhanced as the heating temperature increased from 500 °C to 700 °C. Lastly, the growth mechanism of the zinc oxide nano-coalesced microstructures is discussed according to the reaction conditions.

  11. Synthesis, structure and photoluminescence of (PLAGH){sub 2}[ZnCl{sub 4}] and comparative analysis of photoluminescence properties with tris(2,2′-bipyridine)ruthenium(II)

    SciTech Connect

    Radanović, Mirjana M.; Jelić, Miodrag G.; Romčević, Nebojša Ž.; Boukos, Nikos; Vojinović-Ješić, Ljiljana S.; Leovac, Vukadin M.; Hadžić, Branka B.; Bajac, Branimir M.; Nađ, Laslo F.; Chandrinou, Chrysoula; Baloš, Sebastian S.

    2015-10-15

    Highlights: • New zinc(II) complex with pyridoxalaminoguanidine was synthesized. • The enhancement of the photoluminescence due to the compound formation was achieved. • Very high photoluminescence of Zn(II) compound was noticed. • Comparative analysis of photoluminescence with tris(2,2′-bipyridine) ruthenium(II) was provided. - Abstract: The first compound of zinc(II) containing pyridoxalaminoguanidine has been synthesized and characterized by elemental analysis, infrared spectra, conductometric measurements and X-ray crystallography. Single crystals of the compound were obtained in the reaction of methanolic solution of zinc(II) chloride and pyridoxalaminoguanidine hydrochloride. In this compound the coordination of chelate ligand is absent and tetrachlorido complex of zinc(II) with pyridoxalaminuguanidinium cation as contraion is obtained. Photoluminescence spectra were measured. Lorentzian multipeak technique was used to determine peak wavelengths and their intensities. Photoluminescence spectroscopy upon 325, 488 and 514 nm laser excitation light was used to obtain results. This novel compound of zinc(II) was compared to the well-known organic light emitting diode material—ruthenium(II) complex with bypiridine i.e., tris(2,2′-bipyridine)ruthenium(II), under the same circumstances and the identical experimental setup. A scheme of energy levels and transitions is proposed to explain the obtained experimental results.

  12. Experimental Platform for Studying Thermoelectric Properties in Vacuum Gaps and Molecular Junctions

    NASA Astrophysics Data System (ADS)

    Jeong, Wonho; Kim, Youngsang; Kim, Kyeongtae; Lee, Woochul; Reddy, Pramod

    2014-03-01

    Electromigrated break junction (EBJ) based molecular devices have enabled many research groups to study nanoscale charge transport. Although EBJ devices have been extensively used due to the advantages of a three terminal configuration in tuning the electronic structure, it has not been possible to use them to study thermoelectric properties. This is because creating temperature differentials across the nanogap of EBJs is technically challenging. In order to overcome this experimental limitation, we carefully designed and created a new experimental platform (EBJIH, EBJ with integrated heater) that enables us to study thermoelectric properties in vacuum gaps and molecular junctions. To prove that temperature differentials can be established in these three terminal devices, we performed nanometer resolution thermal imaging using scanning thermal microscopy under UHV conditions. The results clearly show that temperature differentials can indeed be established in the devices. Further, we have used these devices to study the thermoelectric properties of vacuum gaps between gold electrodes and found that the thermoelectric properties were very sensitive to gap dimensions. We are also currently adopting this platform to study thermoelectric properties in molecular junctions.

  13. The photoluminescence properties of QWs with asymmetrical step-like InGaN/GaN quantum barriers

    NASA Astrophysics Data System (ADS)

    Rajabi, Kamran; Yang, Wei; Li, Ding; He, Juan; Zong, Hua; Ji, Qingbin; Shen, Bingran; Yan, Tongxin; Hu, Xiaodong

    2015-04-01

    The asymmetrical structures were created by inserting a low-indium-content layer between the QW and barrier to form a step-like quantum barrier (QB) at one side of QW. The optical effects of the inserting layer on QW emission were investigated with low-temperature photoluminescence (PL) and time-resolved PL (TRPL). The inserted layer partially relaxed the strain within QW layer and induced about 25 nm red-shift in the PL emission compared with conventional QW, while the presence of localization centers around QW affected the emission mechanism and increased the radiative decay time. Furthermore, the position of the inserted layer played different roles in the changed structures, and whilst the n-side step-barrier exhibited strong localization in the energy levels of the inserted layer, the p-side step-barrier showed stronger localization center for the QW levels.

  14. Photoluminescence properties of thermographic phosphors YAG:Dy and YAG:Dy, Er doped with boron and nitrogen

    NASA Astrophysics Data System (ADS)

    Chepyga, Liudmyla M.; Jovicic, Gordana; Vetter, Andreas; Osvet, Andres; Brabec, Christoph J.; Batentschuk, Miroslaw

    2016-08-01

    This paper investigates Dy3+-doped and Dy3+, Er3+-co-doped yttrium aluminum garnets (YAG) with the admixture of boron nitride with the aim of using them as efficient thermographic phosphors at high temperatures. The phosphors were synthesized using a conventional high-temperature solid-state method. The influence of two fluxes, B2O3 and LiF/NH4F, and the effect of activator and coactivator concentrations were investigated. Additionally, the effect of B3+ and N3- substituting for Al3+ and O2- ions, respectively, in the YAG:Dy3+ co-doped with Er3+ was studied for the first time. The changes in the host lattice led to a much stronger photoluminescence compared with the samples without B3+ and N3- substitution. The admixture of BN also improves the thermal sensitivity of the YAG:Dy and YAG:Dy, Er thermographic phosphors.

  15. Investigation to the deep center related properties of low temperature grown InPBi with Hall and photoluminescence

    SciTech Connect

    Wang, Peng; Pan, Wenwu; Wu, Xiaoyan; Wang, Kai; Yue, Li; Gong, Qian; Wang, Shumin

    2015-12-15

    InP{sub 1-x}Bi{sub x} epilayers with bismuth (Bi) concentration x= 1.0% were grown on InP by gas source molecular beam epitaxy (GS-MBE) at low temperature (LT). Bi incorporation decreased the intrinsic free electron concentration of low temperature grown InP indicated by hall analysis. It is concluded that deep level center was introduced by Bi. Influence of Si doping on the InP{sub 1-x}Bi{sub x} films Photoluminescence (PL) was investigated. N-type doping in the InP{sub 1-x}Bi{sub x} epilayers was found to be effective at PL enhancement. Blue shift of InPBi PL emission wavelength was observed as the Si doping concentration increasing. Two independent peaks were fitted and their temperature dependence behavior was observed to be distinct obviously. Two individual radiative recombination processes were expected to be involved.

  16. Tuning the morphologies of SiC nanowires via the control of growth temperature, and their photoluminescence properties.

    PubMed

    Wu, Renbing; Li, Baosheng; Gao, Mingxia; Chen, Jianjun; Zhu, Qimiao; Pan, Yi

    2008-08-20

    Single crystalline SiC nanowires were synthesized by a catalyst free vapor deposition method using elemental silicon and graphite carbon as the starting materials. The phase, morphology, crystal structure, and defects of the products were characterized by x-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Within a 6 h reaction time, the morphology of the SiC nanowires can be tuned to cylinder, hexagonal prism, or bamboo shape by simply altering the reaction temperature from 1470 °C, 1550 °C to 1630 °C, respectively. The photoluminescence of these differently shaped SiC nanowires was measured and is discussed. Based on the characterization results, the vapor-solid growth mechanisms for the multi-shaped SiC nanowires are proposed by taking into account the possible reactions between intermediate gas phases, the reaction steps, and the surface energy minimization.

  17. Effect of electrode gap on the sensing properties of multiwalled carbon nanotubes based gas sensor

    NASA Astrophysics Data System (ADS)

    Saheed, Mohamed Shuaib Mohamed; Mohamed, Norani Muti; Burhanudin, Zainal Arif

    2016-11-01

    Vertically aligned multiwalled carbon nanotubes (MWCNT) were grown on Si substrate coated with alumina and iron using chemical vapor deposition. Electrode gap of 10, 25 and 50 µm were adopted to determine the effect of varying gap spacing on the sensing properties such as voltage breakdown, sensitivity and selectivity for three gases namely argon, carbon dioxide and ammonia. Argon has the lowest voltage breakdown for every electrode gap. The fabricated MWCNT based gas sensor drastically reduced the voltage breakdown by 89.5% when the electrode spacing is reduced from 50 µm to 10 µm. The reduction is attributed to the high non-uniform electric field between the electrodes caused by the protrusion of nanotips. The sensor shows good sensitivity and selectivity with the ability to detect the gas in the mixture with air provided that the concentration is ≥ 20% where the voltage breakdown will be close to the pure gas.

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

    NASA Astrophysics Data System (ADS)

    Malozovsky, Yuriy; Franklin, Lashounda; Ekuma, Chinedu; Zhao, Guang-Lin; Bagayoko, Diola

    2013-03-01

    We present results from ab-initio, self consistent local density approximation (LDA) calculations of electronic and related properties of zinc blende indium and gallium phosphides (InP & GaP) We employed a local density approximation (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 methodically increasing the size of the basis set, up to the optimal one, and the accompanying enrichment of angular symmetry and of radial orbitals. Our calculated, direct band gap of 1.398 eV (1.40 eV) for InP, at the Γ point, is in excellent agreement with experimental values. We discuss our preliminary results for the indirect band gap, from Γ to X, of GaP. We also report calculated electron and hole effective masses for both InP and GaP and the total (DOS) and partial (pDOS) densities of states. This work was funded in part by the National Science Foundation and the Louisiana Board of Regents, through LASiGMA and LS-LAMP, [EPS-1003897, No. NSF (2010-15)-RII-SUBR, and HRD-1002541] and by the Louisiana Optical Network Initiative (LONI) at SUBR.

  19. Reflectivity properties of graphene with a nonzero mass-gap parameter

    NASA Astrophysics Data System (ADS)

    Klimchitskaya, G. L.; Mostepanenko, V. M.

    2016-05-01

    The reflectivity properties of graphene with a nonzero mass-gap parameter are investigated in the framework of a Dirac model using the polarization tensor in (2 +1 ) -dimensional space-time. For this purpose, a more simple explicit representation for the polarization tensor along the real frequency axis is found. The approximate analytic expressions for the polarization tensor and for the reflectivities of graphene are obtained in different frequency regions at any temperature. We show that the nonzero mass-gap parameter has a profound effect on the reflectivity of graphene. Specifically, at zero temperature the reflectivity of gapped graphene goes to zero with vanishing frequency. At nonzero temperature the same reflectivities are equal to unity at zero frequency. We also find the resonance behavior of the reflectivities of gapped graphene at both zero and nonzero temperature at the border frequency determined by the width of the gap. At nonzero temperature the reflectivities of graphene drop to zero in the vicinity of some frequency smaller than the border frequency. Our analytic results are accompanied with numerical computations performed over a wide frequency region. The developed formalism can be used in devising nanoscale optical detectors and optoelectronic switches and in other optical applications of graphene.

  20. Photoluminescence properties of NaPbB{sub 5}O{sub 9}:Dy{sup 3+} new material for white light applications

    SciTech Connect

    Rajesh, D. Ratnakaram, Y. C.

    2014-04-24

    Keeping in view of the recent increased interest towards phosphor materials and its applications, an attempt has been made in the present paper to analyze the new NaPbB{sub 5}O{sub 9}:Dy{sub 3+} phosphor with different Dy{sub 3+} concentrations. Special attention is paid to investigate their crystal structure, morphology and luminescence properties. X-ray diffraction (XRD) results confirm the formation of NaPbB{sub 5}O{sub 9}:Dy{sub 3+} phosphor powder. The scanning electron microscope (SEM) images show that the grains are in micrometer range. Photoluminescence spectra are recorded with different excitation wavelengths for the investigated phosphor and analyzed the variation of intensity of emission bands with Dy{sub 3+} ion concentration. Color co-ordinates are calculated and are used to characterize the color of the phosphor.

  1. Synthesis, crystal structure, photoluminescence property and photoelectronic behavior of two uranyl-organic frameworks constructed from 1, 2, 4, 5-benzenetetracarboxylic acid as ligand.

    PubMed

    Hou, Ya-Nan; Xing, Yong-Heng; Bai, Feng-Ying; Guan, Qing-Lin; Wang, Xuan; Zhang, Rui; Shi, Zhan

    2014-04-05

    By using 1, 2, 4, 5-benzenetetracarboxylic acid as organic ligands, two uranyl coordination complexes, (UO2)2(bta)(DMA)2 (1) and [(UO2)2(bta)(μ3-OH2)]·2[HN(CH3)2]·H2O (2) (H4bta=1, 2, 4, 5-benzenetetracarboxylic acid, DMA=N,N-Dimethylacetamide) were synthesized. The X-ray single crystal analysis revealed that complex 1 exhibits a 3-demensional framework, while complex 2 exhibits a 2-demensional framework. In order to furthermore characterize the two complexes and extend their functional properties, spectroscopies of IR, UV-vis, photoluminescence and surface photovoltage were also studied primarily. In addition, thermogravimetric analyses and photocatalytic studies for complexes 1 and 2 were discussed in detail.

  2. Synthesis and photoluminescence properties of Ca{sub 3}B{sub 2}O{sub 6}:Tb{sup 3+} nanophosphors

    SciTech Connect

    Manhas, Mohit; Kumar, Vinay; Ntwaeaborwa, O. M.; Swart, H. C.

    2014-04-24

    The green light emitting Tb{sup 3+} doped Ca{sub 3}B{sub 2}O{sub 6} nanophosphors have been synthesized by combustion method at 600°C, and their luminescent properties have been studied. The formation of phosphors has been confirmed by X-ray diffraction (XRD). The photoluminescence (PL) spectra show four emission peaks at 491 nm, 544 nm, 587 and 621 nm. It exhibited a strong green emission located at 544 nm. The effect of different dopant concentrations on emission intensity has also been studied. The maximum photo emission intensity of the Ca{sub 3}B{sub 2}O{sub 6}:Tb{sup 3+} was obtained at a dopant concentration of 1.5 mol% of Tb{sup 3+}.

  3. Study of photoluminescence properties of CaAl{sub 2}O{sub 4}: Eu{sup 2+} prepared by combustion synthesis method

    SciTech Connect

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

    2016-05-06

    Eu{sup 2+} 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 Eu{sup 2+} range from 450 to 500 nm in the Blue to aqua region and the transition 4f{sup 7}-4f{sup 6} 5d{sup 1}. The observed emission in CaAl{sub 2}O{sub 4} is 440 nm.

  4. LETTER TO THE EDITOR: Photoluminescence properties of single CdSe quantum dots in ZnSe obtained by self-organized growth

    NASA Astrophysics Data System (ADS)

    Shen, M. Y.; Goto, T.; Kurtz, E.; Zhu, Z.; Yao, T.

    1998-03-01

    The photoluminescence of single CdSe quantum dots in ZnSe grown by molecular beam epitaxy and that of the same system grown by atomic layer epitaxy were investigated. The spectral diffusion and on/off behaviour of single CdSe quantum dots were observed, and the spectral diffusion range was only about 1 meV. The spectral peak shifting became quicker as the temperature rose. The spectral change from blue-shift to red-shift (or vice versa) was much quicker than that found in CdSe quantum dots synthesized as colloids. The phenomena are qualitatively explained by a Stark effect which originated from an Auger ionization process. The spectral diffusion may be a common property among single quantum dots.

  5. The influece of forest gaps on some properties of humus in a managed beech forest, northern Iran

    NASA Astrophysics Data System (ADS)

    Vajari, K. A.

    2015-10-01

    The present research focuses on the effect of eight-year-old artificially created gaps on some properties of humus in managed beech-dominated stand in Hyrcanian forest of northern Iran. In this study, six-teen gaps were sampled in site and were classified into four classes (small, medium, large, and very large) with four replications for each. Humus sampling was carried out at the centre and at the cardinal points within each gap as well as in the adjacent closed stand, separately, as composite samples. The variables of organic carbon, P, K, pH, and total N were measured for each sample. It was found that the gap size had significant effect only on total N (%) and organic carbon (%) in beech stand. The amount of potassium clearly differed among three positions in beech forest. The adjacent stand had higher significantly potassium than center and edge of gaps. Different amount of potassium was detected in gap center and gap edge. Comparison of humus properties between gaps and its adjacent stand pointed to the higher amount of potassium in adjacent stand than that in gaps but there was no difference between them regarding other humus properties. According to the results, it can be concluded that there is relatively similar condition among gaps and closed adjacent stands in terms of humus properties eight years after logging in the beech stand.

  6. Structural variations and photoluminescent properties of a series of metal-organic frameworks constructed from 5-(4-carboxybenzoylamino)-isophthalic acid

    SciTech Connect

    Zhao, Wen; Zhang, Li-Juan; Zhao, Xiao-Li

    2013-06-01

    Five new metal-organic frameworks (MOFs) with 5-(4-carboxybenzoylamino)-isophthalic acid (H₃L), namely, [Cd₉L₆(DMA)₆]·4DMA (1), [Cd₃L₂(H₂O)₉]·4H₂O (2), [LaL(H₂O)₄]·2H₂O (3), [CeL(H₂O)₄]·H₂O (4) and [Tb(HL)(H₂L)(H₂O)₃]·5H₂O (5) (DMA=N,N-dimethylacetamide), have been synthesized. Complex 1 shows a three-dimensional architecture generated from linkage of Cd–O chains via L³⁻ ligands. Minor variations in synthetic conditions of 1 afforded 2, which features an interesting 2D→3D catenation architecture containing helical chains. Complexes 3 and 4 are isostructural and each feature a two-dimensional architecture constructed from the linkage of L³⁻ with Ln³⁺. Complex 5 displays a chain-like structure, of which the most interesting feature is the existence of free carboxylic acid (–COOH) group which may confer unique functionality. Moreover, the investigations of the thermal stability, powder X-ray diffractions and solid-state photoluminescent properties for these crystalline materials have been carried out. - Graphical Abstract: Solvothermal reactions of tricarboxylate ligand H₃L with Cd²⁺/Ln³⁺ has yielded a series of new MOFs containing interesting structural motifs. Highlights: • A tricarboxylate ligand whose coordinating functionalities are not symmetry equivalent is employed to construct MOFs. • Complex 2 features an interesting 2D→3D catenation architecture containing helical chains. • Complex 3 feature chain-like structure containing free – COOH group, which may confer unique functionality. • Photoluminescent properties and thermal behaviors for 1–5 have been reported.

  7. A co-precipitation preparation, crystal structure and photoluminescent properties of Er5%:Gd{sub 2}O{sub 3} nanorods

    SciTech Connect

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

    2015-06-24

    An inexpensive preparation method is being reported for obtaining erbium doped gadolinium oxide (Er5%:Gd{sub 2}O{sub 3}) 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%:Gd{sub 2}O{sub 3} nanorods is briefly discussed.

  8. Engineering of the band gap and optical properties of thin films of yttrium hydride

    NASA Astrophysics Data System (ADS)

    You, Chang Chuan; Mongstad, Trygve; Maehlen, Jan Petter; Karazhanov, Smagul

    2014-07-01

    Thin films of oxygen-containing yttrium hydride show photochromic effect at room temperature. In this work, we have studied structural and optical properties of the films deposited at different deposition pressures, discovering the possibility of engineering the optical band gap by variation of the oxygen content. In sum, the transparency of the films and the wavelength range of photons triggering the photochromic effect can be controlled by variation of the deposition pressure.

  9. Engineering of the band gap and optical properties of thin films of yttrium hydride

    SciTech Connect

    You, Chang Chuan; Mongstad, Trygve; Maehlen, Jan Petter; Karazhanov, Smagul

    2014-07-21

    Thin films of oxygen-containing yttrium hydride show photochromic effect at room temperature. In this work, we have studied structural and optical properties of the films deposited at different deposition pressures, discovering the possibility of engineering the optical band gap by variation of the oxygen content. In sum, the transparency of the films and the wavelength range of photons triggering the photochromic effect can be controlled by variation of the deposition pressure.

  10. A highly bioactive poly (amido amine)/70S30C bioactive glass hybrid with photoluminescent and antimicrobial properties for bone regeneration.

    PubMed

    Akbari Dourbash, Fakhraddin; Alizadeh, Parvin; Nazari, Shahram; Farasat, Alireza

    2017-09-01

    The field of tissue engineering constantly calls for novel biomaterials that possess intrinsically multifunctional properties such as bioactivity, bioimaging ability and antibacterial properties. In this paper, poly (amido amine) generation 5/bioactive glass inorganic-organic hybrids have been developed through direct hybridization by 3-glycidoxypropyltrimethoxysilane (GPTMS) as coupling agent. Results indicated that the degree of covalent coupling by GPTMS and the weight percent of inorganic and organic constituents highly influence hybrids properties. It was found that nanoscale integration of inorganic and organic chains by GPTMS significantly endows hybrids with high thermal stability. Furthermore, hybrids exhibited photoluminescent ability (emission 400-600nm and 700nm) without incorporating of any organic dyes or quantum dots. In addition, hydrophilicity of our hybrids indicated good cell/material interaction. The biological apatite was formed on the surface of calcium containing hybrids when soaked in simulated body fluid (SBF) for 1week. Hybrids also showed linear biodegradation behavior in SBF that could be controlled by the degree of covalent crosslinking which was indicative of their stable biodegradation ability. High inherent antibacterial properties against Staphylococcus aureus was also observed from poly (amido amine)/silica hybrids. No adverse cytotoxicity for human gingival fibroblast cell lines (HGF) was detected after 4days. It is envisaged that our novel multifunctional hybrid system will confer intriguing potential in advancing the field of tissue engineering. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Making Graphene Nanoribbons Photoluminescent.

    PubMed

    Senkovskiy, B V; Pfeiffer, M; Alavi, S K; Bliesener, A; Zhu, J; Michel, S; Fedorov, A V; German, R; Hertel, D; Haberer, D; Petaccia, L; Fischer, F R; Meerholz, K; van Loosdrecht, P H M; Lindfors, K; Grüneis, A

    2017-04-03

    We demonstrate the alignment-preserving transfer of parallel graphene nanoribbons (GNRs) onto insulating substrates. The photophysics of such samples is characterized by polarized Raman and photoluminescence (PL) spectroscopies. The Raman scattered light and the PL are polarized along the GNR axis. The Raman cross section as a function of excitation energy has distinct excitonic peaks associated with transitions between the one-dimensional parabolic subbands. We find that the PL of GNRs is intrinsically low but can be strongly enhanced by blue laser irradiation in ambient conditions or hydrogenation in ultrahigh vacuum. These functionalization routes cause the formation of sp(3) defects in GNRs. We demonstrate the laser writing of luminescent patterns in GNR films for maskless lithography by the controlled generation of defects. Our findings set the stage for further exploration of the optical properties of GNRs on insulating substrates and in device geometries.

  12. Photoluminescence properties of a novel red emitting Ba10F2(PO4)6:Eu3+ phosphor

    NASA Astrophysics Data System (ADS)

    Peng, You-shun; Shi, Wei-wei; Han, Cong-lin; Kang, Yan-yan; Wang, Yan-su; Zhang, Zhi-wei

    2015-06-01

    A novel red-emitting phosphor Ba10F2(PO4)6:Eu3+ is synthesized by a high-temperature solid-state reaction. X-ray powder diffraction (XRD) analysis confirms the phase formation of Ba10F2(PO4)6:Eu3+ materials. The photoluminescence excitation (PLE) and emission (PL) spectra, the concentration dependence of the emission intensity, decay curves and Commission International de I'Eclairage (CIE) of the phosphors are investigated. It is observed that Ba10F2(PO4)6:Eu3+ phosphors exhibit two dominating bands situated at 591 and 616 nm, originating from the 5D0 → 7F1 and 5D0 → 7F2 transition of the Eu3+ ion, respectively. The decay time is also determined for various concentrations of Eu3+ in Ba10F2(PO4)6:Eu3+. Crystal lattice, PL spectra and decay time analysis indicate there exist two isolated Eu3+ crystallography sites in Ba10F2(PO4)6. The calculated color coordinates lie in the red region. Therefore, Ba10F2(PO4)6:Eu3+ phosphors may be good candidates for red components in near-UV (NUV) white LEDs.

  13. Photoluminescence, white light emitting properties and related aspects of ZnO nanoparticles admixed with graphene and GaN

    NASA Astrophysics Data System (ADS)

    Kumar, Prashant; Panchakarla, L. S.; Venkataprasad Bhat, S.; Maitra, Urmimala; Subrahmanyam, K. S.; Rao, C. N. R.

    2010-09-01

    ZnO nanoparticles exhibit a broad band centred around 530 nm in the photoluminescence (PL) spectrum due to the presence of oxygen vacancies. Composites of ZnO nanoparticles with graphenes show marked changes in the PL spectrum with broad bands covering the entire visible region, making them candidates for solid state lighting, while graphene prepared by arc discharge of graphite in a hydrogen atmosphere (HG) containing 2-3 layers as well as boron-doped (BHG) and nitrogen-doped (NHG) samples of HG give white light when admixed with ZnO nanoparticles; excellent results are obtained with the addition of just 7 wt% of BHG to the ZnO nanoparticles. Mixtures of ZnO and GaN nanoparticles also exhibit white light emission. The quantum yields of these ZnO nanoparticle based white light sources are in the 4-6% range. Photoconductivity characteristics of ZnO nanoparticles are affected by the addition of even a small amount of graphene (<0.5 wt%).

  14. Absorption and photoluminescence properties of Er-doped and Er/Yb codoped soda-silicate laser glasses

    SciTech Connect

    Li, S.F.; Zhang, Q.Y.; Lee, Y.P.

    2004-11-01

    Er-doped and Er/Yb codoped soda-silicate laser glasses with various concentrations of Er and Yb were fabricated. The absorption and the photoluminescence (PL) spectra were measured and analyzed. For the Er- doped soda-slilicate glasses, the optimum Er concentration for the PL intensity at 1536 nm turns out to be 0.5 at. %, and the full width at half maximum (FWHM) of PL spectrum increases from 18 to 26 nm, with the increase of the concentration from 0.1 to 0.8 at. %. The PL intensity of Er/Yb codoped soda-silicate glasses with an Er concentration of 0.5 at. % is enhanced approximately by four times, and the optimum Yb concentration for the PL intensity at 1536 nm is analyzed to be 3.0 at. %. The PL spectrum becomes broader with increasing the Yb concentration, up to a FWHM of 80 nm at 6.0 at. %. Yb. The relation between the absorption and PL spectra, together with the mechanism of PL broadening, has also been addressed.

  15. SiC Nanorods Grown on Electrospun Nanofibers Using Tb as Catalyst: Fabrication, Characterization, and Photoluminescence Properties

    PubMed Central

    2009-01-01

    Well-crystallizedβ-SiC nanorods grown on electrospun nanofibers were synthesized by carbothermal reduction of Tb doped SiO2(SiO2:Tb) nanofibers at 1,250 °C. The as-synthesized SiC nanorods were 100–300 nm in diameter and 2–3 μm in length. Scanning electron microscopy (SEM) results suggested that the growth of the SiC nanorods should be governed by vapor-liquid-solid (VLS) mechanism with Tb metal as catalyst. Tb(NO3)3particles on the surface of the electrospun nanofibers were decomposed at 500 °C and later reduced to the formation of Tb nanoclusters at 1,200 °C, and finally the formation of a Si–C–Tb ally droplet will stimulate the VLS growth at 1,250 °C. Microstructure of the nanorod was further investigated by transmission electron microscopy (TEM). It was found that SiC <111> is the preferred initial growth direction. The liquid droplet was identified to be Si86Tb14, which acted as effective catalyst. Strong green emissions were observed from the SiC nanorod samples. Four characteristic photoluminescence (PL) peaks of Tb ions were also identified. PMID:20596383

  16. Semiconductor-olefin adducts. Photoluminescent properties of cadmium sulfide and cadmium selenide in the presence of butenes

    SciTech Connect

    Meyer, G.J.; Leung, L.K.; Ellis, A.B. ); Yu, J.C. ); Lisensky, G.C. )

    1989-07-05

    Direct evidence for adduct formation between butenes and etched, single-crystal n-CdS and n-CdSe (CdS(e)) surfaces has been obtained from photoluminescence (PL) measurements. Exposure of CdS(e) to butenes causes enhancement of the solids' band edge PL relative to a N{sub 2} ambient. For 30% mixtures of the olefins in N{sub 2}, the magnitude of the enhancement follows the order 1,3-butadiene > cis-2-butene {approximately} trans-2-butene > isobutylene {approximately} 1-butene and correlates with the olefin basicities, on the basis of photoionization potentials. Enhancements in PL intensity can be fit to a dead-layer model, allowing the determination of the reduction in depletion width in the semiconductor resulting from olefin exposure; depletion width reductions reach a few hundred angstroms for adducts of 1,3-butadiene with CdS(e). The PL changes were used in conjunction with the Langmuir adsorption isotherm model to yield equilibrium constants for adduct formation of 1,3-butadiene with CdS(e) of 9 {plus minus} 4 atm{sup {minus}1} at 293 K. Surface interactions that may contribute to the observed PL changes are discussed.

  17. The structure and photoluminescence properties of Bi2O3-core/SnO2-shell nanowires.

    PubMed

    Jin, Changhyun; Kim, Hyunsoo; Lee, Chongmu

    2011-01-01

    Bi2O3-core/SnO2-shell nanowires have been prepared by using a two-step process: thermal evaporation of Bi2O3 powders and sputtering of SnO2. The crystalline nature of the Bi2O3-core/SnO2-shell nanowires has been revealed by high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). TEM analysis and X-ray diffraction (XRD) results indicate that the Bi2O3-core/SnO2-shell nanowires consist of pure tetragonal alpha-Bi2O3-phase momocrystalline cores and tetragonal SnO2-phase polycrystalline shells. The photoluminescence (PL) measurements show that Bi2O3 nanowires have a broad emission band centered at around 560 nm in the yellow-green region. On the other hand, the Bi2O3-core/SnO2-shell coaxial nanowires with the sputtering times of 4 and 8 min have a blue emission band centered at around 450 nm. In contrast, those with a sputtering time of 10 min have a broad emission band centered at approximately 550 nm again. The origin of this yellow-green emission from the core/shell nanowires, however, quite differs from that from Bi2O3 nanowires, i.e., it is not from the Bi2O3 cores but from the SnO2 shells.

  18. Photoluminescence quenching, structures, and photovoltaic properties of ZnO nanostructures decorated plasma grown single walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Aïssa, Brahim; Nedil, Mourad; Belaidi, Abdelhak; Isaifan, Rima J.; Bentouaf, Ali; Fauteux, Christian; Therriault, Daniel

    2017-05-01

    Zinc oxide (ZnO) nanostructures were successfully grown directly on single walled carbon nanotubes (SWCNT) template through the CO2 laser-induced chemical liquid deposition (LCLD) process. Photoluminescence (PL) of the deposited ZnO/SWCNT hybrid composites exhibits, at room temperature, a narrow near UV band located at 390 nm with no emission bands in the visible region, indicating a high degree of crystalline quality of the ZnO nanostructures. Moreover, when the relative SWCNT loads are varied within the composites, the PL intensity and the diffused optical reflectance diminish in comparison with those of ZnO alone, owing to the transfer of photo-excited electrons from ZnO to the SWCNT, and the enhancement of the optical absorbance, respectively. Finally, these ZnO/SWCNT hybrid composites are integrated into a heterojunction photovoltaic-based device, using PEDOT:PSS on ITO/glass substrate. The devices show an evident p-n junction behavior in the dark, and a clear I- V curve shift downward when illuminated with an open-circuit voltage of 1.1 V, a short circuit current density of 14.05 μA cm-2, and a fill factor of ˜35%. These results indicate that these composites fabricated via LCLD process could be promising for optoelectronic and energy-harvesting devices.

  19. Cetyltrimethylammonium bromide assisted self-assembly of NiTe{sub 2} nanoflakes: Nanoflake arrays and their photoluminescence properties

    SciTech Connect

    Jiang Ling; Zhu Yingjie; Cui Jingbiao

    2010-10-15

    NiTe{sub 2} nanoflakes and their self-assembled nanoflake arrays (one-dimensional nanostructures) have been prepared by a single-step hydrothermal method using Ni(CH{sub 3}COO){sub 2}.4H{sub 2}O, Na{sub 2}TeO{sub 3}, glucose, and cetyltrimethylammonium bromide (CTAB). CTAB was found to strongly influence the structure and morphology of the resultant NiTe{sub 2}. Morphological transformations from nanoflakes to self-assembled nanoflake arrays and then to solid smooth nanowires were observed as CTAB concentration was increased in the growth solution. Photoluminescence of the NiTe{sub 2} self-assembled nanoflake arrays was investigated for the first time and the formation mechanism of the NiTe{sub 2} nanostructures is also discussed. - Graphical abstract: NiTe{sub 2} nanoflakes and their self-assembled nanoflake arrays have been prepared by a single-step hydrothermal method using Ni(CH{sub 3}COO){sub 2}.4H{sub 2}O, Na{sub 2}TeO{sub 3}, glucose, and cetyltrimethylammonium bromide (CTAB).

  20. Time-resolved photoluminescence properties of ion-beam-synthesized β-FeSi2 and Si-implanted Si

    NASA Astrophysics Data System (ADS)

    Terai, Yoshikazu; Maeda, Yoshihito

    2015-07-01

    Temporal decay characteristics of 1.54 µm photoluminescence (PL) were investigated in β-FeSi2 and Si-implanted Si samples grown by ion-beam-synthesis (IBS). In the samples, the band-edge PL of β-FeSi2 (A-band) and the dislocation-related PL (D1-band) of Si were both observed at ˜0.8 eV. Regarding the dependence of the PL decay curves on excitation power density (P), PL decay curves without extrinsic effects were obtained at a low P of P ≤ 4.3 mW/cm2. The PL decay times obtained at a low P showed clear differences between the A-band and the D1-line. The result showed that the band-edge PL of β-FeSi2 was distinguished from the dislocation-related PL of Si by the PL decay times. The intrinsic PL decay times of β-FeSi2 were determined to be τ1 = 70-100 ns and τ2 = 550-670 ns at 5 K.

  1. [Near-infrared photoluminescence properties of natural sodalite activated with Mn and Fe transition metal ions doping].

    PubMed

    Aidilibike, Tuerxun; Asilibieke, Bahetiguli; Sidike, Aierken

    2013-11-01

    Na8Al6Si6O24Cl2 : Mn and Na8Al6Si6O24Cl2 : Fe NIR phosphors were prepared by a solid-solid reaction at high temperature. Their crystal structures of fluorescent powder were investigated by using X-ray powder diffraction (XRD), and their NIR emission spectrum and excitation spectrum were measured at room temperature. The main emission peak of Mn5+ in the Na8Al6Si6O24Cl2 : Mn phosphor was observed at 1 200 nm in the NIR spectral region under 400 or 602 nm excitation, attributing to the 3A2-3T2 and 3A2-1E transitions of Mn5+ ions. The characteristic NIR luminescence of Mn5+ in sodalite is greatly enhanced by co-doping manganese and sulfur. A mechanism of the energy transfer between S2(-) and Mn5+ was also proposed here. The main emission peak of Fe2+ ions in the Na8Al6Si6O24Cl2 : Fe phosphor was recorded at 1 000 nm in the NIR region under the excitation of 334 or 500 nm. This photoluminescence originated from the 3T1-5 E transition of Fe2+. Such an emission in the NIR region suggests a potential application in improving solar spectrum to enhance the efficiency of silicon solar cells.

  2. Effect of Yb(3+) on the Crystal Structural Modification and Photoluminescence Properties of GGAG:Ce(3+).

    PubMed

    Luo, Zhao-Hua; Liu, Yong-Fu; Zhang, Chang-Hua; Zhang, Jian-Xin; Qin, Hai-Ming; Jiang, Hao-Chuan; Jiang, Jun

    2016-03-21

    Gadolinium gallium aluminum garnet (GGAG) is a very promising host for the highly efficient luminescence of Ce(3+) and shows potential in radiation detection applications. However, the thermodynamically metastable structure would be slanted against it from getting high transparency. To stabilize the crystal structure of GGAG, Yb(3+) ions were codoped at the Gd(3+) site. It is found that the decomposition of garnet was suppressed and the transparency of GGAG ceramic was evidently improved. Moreover, the photoluminescence of GGAG:Ce(3+),xYb(3+) with different Yb(3+) contents has been investigated. When the Ce(3+) ions were excited under 475 nm, a typical near-infrared region emission of Yb(3+) ions can be observed, where silicon solar cells have the strongest absorption. Basing on the lifetimes of Ce(3+) ions in the GGAG:Ce(3+),xYb(3+) sample, the transfer efficiency from Ce(3+) to Yb(3+) and the theoretical internal quantum efficiency can be calculated and reach up to 86% and 186%, respectively. This would make GGAG:Ce(3+),Yb(3+) a potential attractive downconversion candidate for improving the energy conversion efficiency of crystalline silicon (c-Si) solar cells.

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    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(CH3COO)2·2H2O to obtain zinc-containing precursor spheres and thermally treatment at 600 °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 ∼150 nm and wall thickness of ∼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.

  4. Investigation of Boron-doping Effect on Photoluminescence Properties of CdNb2O6: Eu(3+) Phosphors.

    PubMed

    Başak, Ali Sadi; Ekmekçi, Mete Kaan; Erdem, Murat; Ilhan, Mustafa; Mergen, Ayhan

    2016-03-01

    Pure, Eu(3+) - doped and Eu(3+),B(3+) co-doped CdNb2O6 powders have been prepared by a molten salt synthesis method using Li2SO4/Na2SO4 salt mixture as a flux at a relatively low temperatures as compared to solid state reaction. X-ray diffraction patterns of pure CdNb2O6 samples indicated orthorhombic single phase. Photoluminescence investigations of CdNb2O6 samples showed a strong blue emission band centered at 460 nm. For Eu-doped CdNb2O6 samples, the luminescence of Eu(3+) was observed with the host red emission varying with the Eu-doping concentrations. This PL characteristic of the doped samples may be attributed to the energy transfer between Eu(3+) and niobate groups (NbO6). Boron incorporation has remarkably increased the luminescence of Eu(3+)-doped CdNb2O6.

  5. Photoluminescence properties of a novel red emitting Ba₁₀F₂(PO ₄)₆:Eu³⁺ phosphor.

    PubMed

    Peng, You-Shun; Shi, Wei-Wei; Han, Cong-Lin; Kang, Yan-Yan; Wang, Yan-Su; Zhang, Zhi-Wei

    2015-06-15

    A novel red-emitting phosphor Ba10F2(PO4)6:Eu(3+) is synthesized by a high-temperature solid-state reaction. X-ray powder diffraction (XRD) analysis confirms the phase formation of Ba10F2(PO4)6:Eu(3+) materials. The photoluminescence excitation (PLE) and emission (PL) spectra, the concentration dependence of the emission intensity, decay curves and Commission International de I'Eclairage (CIE) of the phosphors are investigated. It is observed that Ba10F2(PO4)6:Eu(3+) phosphors exhibit two dominating bands situated at 591 and 616 nm, originating from the (5)D0→(7)F1 and (5)D0→(7)F2 transition of the Eu(3+) ion, respectively. The decay time is also determined for various concentrations of Eu(3+) in Ba10F2(PO4)6:Eu(3+). Crystal lattice, PL spectra and decay time analysis indicate there exist two isolated Eu(3+) crystallography sites in Ba10F2(PO4)6. The calculated color coordinates lie in the red region. Therefore, Ba10F2(PO4)6:Eu(3+) phosphors may be good candidates for red components in near-UV (NUV) white LEDs.

  6. Self-assembled ZnO nanoparticles on ZnO microsheet: ultrafast synthesis and tunable photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Brahma, Sanjaya; Khatei, Jayakrishna; Sunkara, S.; Lo, K.-Y.; Shivashankar, S. A.

    2015-06-01

    We report on the tunable photoluminescence characteristics of porous ZnO microsheets fabricated within 1-5 min of microwave irradiation in the presence of a capping agent such as citric acid, and mixture of citric acid with polyvinylpyrrolidone (PVP). The UV emission intensity reduces to 60% and visible emission increases tenfold when the molar concentration of citric acid is doubled. Further diminution of the intensity of UV emission (25%) is observed when PVP is mixed with citric acid. The addition of nitrogen donor ligands to the parent precursor leads to a red shift in the visible luminescence. The deep level emission covers the entire visible spectrum and gives an impression of white light emission from these ZnO samples. The detailed luminescence mechanism of our ZnO samples is described with the help of a band diagram constructed by using the theoretical models that describe the formation energy of the defect energy levels within the energy band structure. Oxygen vacancies play the key role in the variation of the green luminescence in the ZnO microsheets. Our research findings provide an insight that it is possible to retain the microstructure and simultaneously introduce defects into ZnO. The growth of the ZnO microsheets may be due to the self assembly of the fine sheets formed during the initial stage of nucleation.

  7. Controllable synthesis and defect-dependent photoluminescence properties of In2O3 nanostructures prepared by PVD

    NASA Astrophysics Data System (ADS)

    Jin, Changqing; Wei, Yongxing; Peterson, George; Zhu, Kexin; Jian, Zengyun

    2017-05-01

    In2O3 nanostructures were successfully synthesized via physical vapor deposition (PVD). It was found that the morphology of nanostuctures could be controlled by manipulation of the synthesis temperature, growth time, use of a Au-catalyst, selection of substrate material, and vapor pressure. A higher synthesis temperature is more favorable for the formation of 1D nanostructures. An increased growth time increased the width and length of the 1D nanostructures. Through the use of a Au-catalyst coated Si (1 0 0) substrate, we were able to preferentially synthesize (1 0 0) In2O3 nanostructures, even at lower growth temperatures. This research shows that a Au-catalyst is necessary for the formation of one-dimensional (1D) In2O3 nanostructures. Three dimensional (3D) octahedral nanoparticles are resultant from a Au-free Si (1 0 0) substrate. Al2O3 (1 0 0) substrates were found to be energetically favorable for the synthesis of nanofilms, not 1D nanostructures, regardless of the presence of Au-catalyst. The photoluminescence curves indicate that the defect related luminescence is not a function of morphology, but rather the ratio of the partial vapor pressures of the constituent elements (In and O), which were controlled by the growth pressure.

  8. Shape tailored green synthesis of CeO2:Ho3+ nanopowders, its structural, photoluminescence and gamma radiation sensing properties

    NASA Astrophysics Data System (ADS)

    Malleshappa, J.; Nagabhushana, H.; Kavyashree, D.; Prashantha, S. C.; Sharma, S. C.; Premkumar, H. B.; Shivakumara, C.

    2015-06-01

    CeO2:Ho3+ (1-9 mol%) nanopowders have been prepared by efficient and environmental friendly green combustion method using Aloe vera gel as fuel for the first time. The final products are well characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), fourier transform infrared (FTIR). Bell, urchin, core shell and flower like morphologies are observed with different concentrations of the A. vera gel. It is apparent that by adjusting the concentration of the gel, considerable changes in the formation of CeO2:Ho3+ nano structures can be achieved. Photoluminescence (PL) studies show green (543, 548 nm) and red (645, 732 nm) emissions upon excited at 400 nm wavelength. The emission peaks at ∼526, 548, 655 and 732 nm are associated with the transitions of 5F3 → 5I8, 5S2 → 5I8, 5F5 → 5I8 and 5S2 → 5I7, respectively. Three TL glow peaks are observed at 118, 267 and 204 °C for all the γ irradiated samples which specify the surface and deeper traps. Linear TL response in the range 0.1-2 kGy shows that phosphor is fairly useful as γ radiation dosimeter. Kinetic parameters associated with the glow peaks are estimated using Chen's half width method. The CIE coordinate values show that phosphor is quite useful for the possible applications in WLEDs as orange red phosphor.

  9. Emerging plasmonic nanostructures for controlling and enhancing photoluminescence

    PubMed Central

    Park, Jeong-Eun; Kim, Jiyeon

    2017-01-01

    Localised surface plasmon resonance endows plasmonic nanostructures with unique, powerful properties such as photoluminescence enhancement, which is a phenomenon based on the interaction between light and a metal nanostructure. In particular, photoluminescence modulation and enhancement are of importance to many research fields such as photonics, plasmonics and biosensing. In this minireview, we introduce basic principles of plasmonic-nanostructure photoluminescence and recently reported plasmonic nanostructures exhibiting surface-enhanced fluorescence and direct photoluminescence, with one-photon photoluminescence being of particular interest. Gaining insights into these systems not only helps understand the fundamental concepts of plasmonic nanostructures but also advances and extends their applications. PMID:28936337

  10. Emerging plasmonic nanostructures for controlling and enhancing photoluminescence.

    PubMed

    Park, Jeong-Eun; Kim, Jiyeon; Nam, Jwa-Min

    2017-07-01

    Localised surface plasmon resonance endows plasmonic nanostructures with unique, powerful properties such as photoluminescence enhancement, which is a phenomenon based on the interaction between light and a metal nanostructure. In particular, photoluminescence modulation and enhancement are of importance to many research fields such as photonics, plasmonics and biosensing. In this minireview, we introduce basic principles of plasmonic-nanostructure photoluminescence and recently reported plasmonic nanostructures exhibiting surface-enhanced fluorescence and direct photoluminescence, with one-photon photoluminescence being of particular interest. Gaining insights into these systems not only helps understand the fundamental concepts of plasmonic nanostructures but also advances and extends their applications.

  11. Crystal, electronic structures and photoluminescence properties of rare-earth doped LiSi{sub 2}N{sub 3}

    SciTech Connect

    Li, Y.Q. Hirosaki, N.; Xie, R.J.; Takeka, T.; Mitomo, M.

    2009-02-15

    The crystal and electronic structures, and luminescence properties of Eu{sup 2+}, Ce{sup 3+} and Tb{sup 3+} activated LiSi{sub 2}N{sub 3} are reported. LiSi{sub 2}N{sub 3} is an insulator with an indirect band gap of about 5.0 eV (experimental value {approx}6.4 eV) and the Li 2s, 2p states are positioned on the top of the valence band close to the Fermi level and the bottom of the conduction band. The solubility of Eu{sup 2+} is significantly higher than Ce{sup 3+} and Tb{sup 3+} in LiSi{sub 2}N{sub 3} which may be strongly related to the valence difference between Li{sup +} and rare-earth ions. LiSi{sub 2}N{sub 3}:Eu{sup 2+} shows yellow emission at about 580 nm due to the 4f{sup 6}5d{sup 1}{yields}4f{sup 7} transition of Eu{sup 2+}. Double substitution is found to be the effective ways to improve the luminescence efficiency of LiSi{sub 2}N{sub 3}:Eu{sup 2+}, especially for the partial replacement of (LiSi){sup 5+} with (CaAl){sup 5+}, which gives red emission at 620 nm, showing highly promising applications in white LEDs. LiSi{sub 2}N{sub 3}:Ce{sup 3+} emits blue light at about 450 nm arising from the 5d{sup 1}{yields}4f{sup 1}5d{sup 0} transition of Ce{sup 3+} upon excitation at 320 nm. LiSi{sub 2}N{sub 3}:Tb{sup 3+} gives strong green line emission with a maximum peak at about 542 nm attributed to the {sup 5}D{sub 4}{yields}{sup 7}F{sub J} (J=3-6) transition of Tb{sup 3+}, which is caused by highly efficient energy transfer from the LiSi{sub 2}N{sub 3} host to the Tb{sup 3+} ions. - Graphical abstract: Local crystal structure and luminescence spectra of Li{sub 1-2x-y}Ca{sub y}Eu{sub x}Si{sub 2-y}Al{sub y}N{sub 3}. The emission band of Eu{sup 2+} shifts from yellow to red spectral region by the double substitution Ca{sup 2+}{yields}Li{sup +} and Al{sup 3+}{yields}Si{sup 4+} simultaneously in Li{sub 1-2x}Eu{sub x}Si{sub 2}N{sub 3} due to the significant changes in the local environment of the Li{sub Ca,Eu} ions.

  12. Properties of gap junction channels formed by Cx46 alone and in combination with Cx50.

    PubMed Central

    Hopperstad, M G; Srinivas, M; Spray, D C

    2000-01-01

    Gap junctions formed of connexin46 (Cx46) and connexin50 (Cx50) in lens fiber cells are crucial for maintaining lens transparency. We determined the functional properties of homotypic Cx46, heterotypic Cx46/Cx50, and heteromeric Cx46/Cx50 channels in a communication-deficient neuroblastoma (N2A) cell line, using dual whole-cell recordings. N2A cultures were stably and/or transiently transfected with Cx46, Cx50, and green fluorescent protein (EGFP). The macroscopic voltage sensitivity of homotypic Cx46 conformed to the two-state model (Boltzmann parameters: G(min) = 0.11, V(0) = +/- 48.1 mV, gating charge = 2). Cx46 single channels showed a main-state conductance of 140 +/- 8 pS and multiple subconductance states ranging from < or =10 pS to 60 pS. Conservation of homotypic properties in heterotypic Cx46/Cx50 cell pairs allowed the determination of a positive relative gating polarity for the dominant gating mechanisms in Cx46 and Cx50. Observed gating properties were consistent with a second gating mechanism in Cx46 connexons. Moreover, rectification was observed in heterotypic cell pairs. Some cell pairs in cultures simultaneously transfected with Cx46 and Cx50 exhibited junctional properties not observed in other preparations, suggesting the formation of heteromeric channels. We conclude that different combinations of Cx46 and Cx50 within gap junction channels lead to unique biophysical properties. PMID:11023900

  13. Structural and photoluminescence properties of stannate based displaced pyrochlore-type red phosphors: Ca(3-x)Sn₃Nb₂O₁₄:xEu³⁺.

    PubMed

    Sreena, T S; Prabhakar Rao, P; Francis, T Linda; Raj, Athira K V; Babu, Parvathi S

    2015-05-14

    New stannate based displaced pyrochlore-type red phosphors, Ca(3-x)Sn3Nb2O14:xEu(3+), were prepared via a conventional solid state method. The influence of partial occupancy of Sn in both A and B sites of the pyrochlore-type oxides on the photoluminescence properties was studied using powder X-ray diffraction, FT-Raman, transmission electron microscopy, scanning electron microscopy with energy dispersive spectrometry, UV-visible absorption spectroscopy, and photoluminescence excitation and emission spectra with lifetime measurements. The structural analysis establishes that these oxides belong to a cubic displaced pyrochlore type structure with a space group Fd3̄m. These phosphors exhibit strong absorptions at near UV and blue wavelength regions and emit intense multiband emissions due to Eu(3+ 5)D0-(7)F(0, 1, 2) transitions. The absence of characteristic MD transition splitting points out that local cation disorder exists in this type of displaced pyrochlores, reducing the D(3d) inversion symmetry, which is not evidenced by such disorder in the X-ray diffraction analysis. The unusual forbidden intense sharp (5)D0-(7)F0 transition indicates single site occupancy of Eu(3+) with a narrower range of bonding environment, preventing the cluster formation. This is supported by the stable (5)D0 lifetime with Eu(3+) concentration. The Judd-Ofelt intensity parameter assessment corroborates these results. The CIE color coordinates of these phosphors were found to be (0.60, 0.40), which are close to the NTSC standard values (0.67, 0.33) for a potential red phosphor.

  14. Photoluminescence properties of phosphors based on Lu3+-stabilized Gd3Al5O12:Tb3+/Ce3+ garnet solid solutions

    NASA Astrophysics Data System (ADS)

    Li, Jinkai; Li, Ji-Guang; Li, Xiaodong; Sun, Xudong

    2016-12-01

    The Gd3Al5O12:Tb/Ce (GdAG:Tb/Ce) garnet solutions effectively stabilized by Lu3+ have been achieved by calcining their precursor at 1300 °C. Detailed characterizations are given to the materials in terms of XRD, FE-SEM, BET, PL/PLE, and fluorescence decay analysis. The occurrence of Gd3+ and Tb3+ transitions from the photoluminescence excitation spectrum monitoring the Ce3+ yellow emission strongly confirmed the efficient Gd3+ → Ce3+ and Tb3+ → Ce3+ energy transfer. The [(Gd0.8Lu0.2)0.99-xCe0.01Tbx]AG (x = 0-0.1) phosphors with good dispersion and uniform particle size exhibit various luminescent properties under different excitation wavelength of 275, 338, and 457 nm, respectively. The photoluminescence comparison indicated that owing to the Gd3+ → Ce3+ and Tb3+ → Ce3+ energy transfer, the best luminescent phosphor [(Gd0.8Lu0.2)0.89Ce0.01 Tb0.1]AG is almost identical to the well-known YAG:Ce, higher than LuAG:Ce in emission intensity, and has a substantially red-shifted emission band that is desired for warm-white lighting. The Tb3+ → Ce3+ energy transfer was suggested to be electric multipolar interactions, and the processes of energy migration among the optically active Gd3+, Tb3+, and Ce3+ ions were discussed in detail. Fluorescence decay analysis found the lifetime for the Ce3+ emission hardly changes with the Tb3+ incorporation. The [(Gd0.8Lu0.2)0.99-xCe0.01Tbx]AG garnets developed in this work may serve as a new type of phosphor that hopefully meets the requirements of various lighting, optical display, and scintillation applications.

  15. Improved photoluminescence properties of a new green SrB{sub 2}O{sub 4}:Tb{sup 3+} phosphor by charge compensation

    SciTech Connect

    Wu, Zhan-Chao; Wang, Ping; Liu, Jie; Li, Chao; Zhou, Wen-Hui; Kuang, Shao-Ping

    2012-11-15

    Highlights: ► New green-emitting SrB{sub 2}O{sub 4}:Tb{sup 3+} phosphor was synthesized by solid-state reaction. ► Li{sup +}, Na{sup +}, and K{sup +} can all increase luminescent intensity of SrB{sub 2}O{sub 4}:Tb{sup 3+}. ► Na{sup +} is the optimal charge compensator among Li{sup +}, Na{sup +} and K{sup +}. ► SrB{sub 2}O{sub 4}:Tb{sup 3+} is a promising green phosphor for fabricating WLED. -- Abstract: A new green-emitting SrB{sub 2}O{sub 4}:Tb{sup 3+} phosphor was synthesized by solid-state reaction. X-ray powder diffraction (XRD) analysis confirmed all the samples with orthorhombic formation of SrB{sub 2}O{sub 4}. The excitation spectra indicate the phosphor can be effectively excited by near ultraviolet (NUV) light, making it attractive as conversion phosphor for LED applications. The phosphor exhibits a bright green emission with the highest photoluminescence (PL) intensity at 544 nm excited by 378 nm light. The critical quenching concentration of Tb{sup 3+} in SrB{sub 2}O{sub 4}:Tb{sup 3+} is about 10 mol%. The effects of charge compensators (Li{sup +}, Na{sup +}, and K{sup +}) on photoluminescence of SrB{sub 2}O{sub 4}:Tb{sup 3+} were also studied. The results show that the emission intensity can be improved by all the three charge compensators and Na{sup +} is the optimal one for SrB{sub 2}O{sub 4}:Tb{sup 3+}. All properties show that the phosphor is a promising green phosphor pumped by NUV InGaN chip for fabricating white light-emitting diodes (WLEDs).

  16. Photoluminescence properties of LiBaPO4:M3+ phosphor for near-UV light-emitting diode (M = Eu and Dy).

    PubMed

    Puppalwar, S P; Dhoble, S J

    2015-09-01

    A novel phosphor LiBaPO4 doped with rare earths Eu and Dy prepared by high temperature solid-state reaction method is reported. The phosphors were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL). The emission and excitation spectra of these materials were measured at room temperature with a spectrofluorophotometer. The excitation spectra of LiBaPO4:Eu(3+) phosphor can be efficiently excited by 394 nm, which is matched well with the emission wavelength of near-UV light-emitting diode (LED) chip. PL properties of Eu(3+)-doped LiBaPO4 exhibited the characteristic red emission coming from (5) D0 → (7) F1 (593 nm) and (5) D0 → (7) F2 (617 nm) electronic transitions with color coordinations of (0.680, 0.315). The results demonstrated that LiBaPO4:Eu(3+) is a potential red-emitting phosphor for near-UV LEDs. Emission spectra of LiBaPO4:Dy(3+) phosphors showed efficient blue (481 nm) and yellow (574 nm) bands, which originated from (4) F9/2 → 6) H15/2 and (4) F9/2 → (6) H13/2 transitions of the Dy(3+) ion, respectively. The 574 nm line is more intense than the 481 nm lines, which indicates that the site Dy(3+) is located with low symmetry. This article summarizes fundamentals and possible applications of optically useful inorganic phosphates with visible photoluminescence of Eu(3+) and Dy(3+) ions. Copyright © 2015 John Wiley & Sons, Ltd.

  17. Low band gap frequencies and multiplexing properties in 1D and 2D mass spring structures

    NASA Astrophysics Data System (ADS)

    Aly, Arafa H.; Mehaney, Ahmed

    2016-11-01

    This study reports on the propagation of elastic waves in 1D and 2D mass spring structures. An analytical and computation model is presented for the 1D and 2D mass spring systems with different examples. An enhancement in the band gap values was obtained by modeling the structures to obtain low frequency band gaps at small dimensions. Additionally, the evolution of the band gap as a function of mass value is discussed. Special attention is devoted to the local resonance property in frequency ranges within the gaps in the band structure for the corresponding infinite periodic lattice in the 1D and 2D mass spring system. A linear defect formed of a row of specific masses produces an elastic waveguide that transmits at the narrow pass band frequency. The frequency of the waveguides can be selected by adjusting the mass and stiffness coefficients of the materials constituting the waveguide. Moreover, we pay more attention to analyze the wave multiplexer and DE-multiplexer in the 2D mass spring system. We show that two of these tunable waveguides with alternating materials can be employed to filter and separate specific frequencies from a broad band input signal. The presented simulation data is validated through comparison with the published research, and can be extended in the development of resonators and MEMS verification.

  18. Polyvinyl alcohol as photoluminescent conductive polymer

    NASA Astrophysics Data System (ADS)

    Ruiz-Limón, B.; Wetzel, G. B. J.; Olivares-Pérez, A.; Ponce-Lee, E. L.; Hernández-Garay, M. P.; Páez-Trujillo, G.; Toxqui-López, S.; Fuentes-Tapia, I.

    2007-02-01

    We synthesized a photoluminescent conductor polymer composed of polyvinyl alcohol, which was doped with nickel chloride to decrease its resistivity (300 Ωcm) and benzalkonium chloride to obtain photoluminescence properties, when it is radiated with a green laser beam (532 nm). We compared its absorbance curve and its energy emitted curve to observe the amount energy that is taken advantage of this process. Besides we research the photoluminescence behavior when an electric currant is applied in our conductor polymer, obtaining a modulation capacity.

  19. The Photoluminescent Properties of New Cationic Iridium(III) Complexes Using Different Anions and Their Applications in White Light-Emitting Diodes.

    PubMed

    Yang, Hui; Meng, Guoyun; Zhou, Yayun; Tang, Huaijun; Zhao, Jishou; Wang, Zhengliang

    2015-09-14

    Three cationic iridium(III) complexes [Ir(ppy)₂(phen)][PF₆] (C1), [Ir(ppy)₂(phen)]₂SiF₆ (C2) and [Ir(ppy)₂(phen)]₂TiF₆ (C3) (ppy: 2-phenylpyridine, phen: 1, 10-phenanthroline) using different anions were synthesized and characterized by ¹H Nuclear magnetic resonance (¹HNMR), mass spectra (MS), Fourier transform infrared (FTIR) spectra and element analysis (EA). After the ultraviolet visible (UV-vis) absorption spectra, photoluminescent (PL) properties and thermal properties of the complexes were investigated, complex C1 and C3 with good optical properties and high thermal stability were used in white light-emitting diodes (WLEDs) as luminescence conversion materials by incorporation with 460 nm-emitting blue GaN chips. The integrative performances of the WLEDs fabricated with complex C1 and C3 are better than those fabricated with the widely used yellow phosphor Y₃Al₅O12:Ce(3+) (YAG). The color rendering indexes of the WLEDs with C1 and C3 are 82.0 and 82.6, the color temperatures of them are 5912 K and 3717 K, and the maximum power efficiencies of them are 10.61 Lm·W(-1) and 11.41 Lm·W(-1), respectively.

  20. Synthesis and photoluminescence properties of cerium-doped terbium-yttrium aluminum garnet phosphor for white light-emitting diodes applications

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Han, Tao; Lang, Tianchun; Tu, Mingjing; Peng, Lingling

    2015-11-01

    Cerium-doped terbium-yttrium aluminum garnet phosphors were synthesized using the solid-state reaction method. The crystalline phase, morphology, and photoluminescence properties were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), and fluorescence spectrophotometer, respectively. The XRD results indicate that with an increase of the amount of x (Tb3+), all of the samples have a pure garnet crystal structure without secondary phases. The SEM images reveal that the samples are composed of sphere-like crystallites, which exhibit different degrees of agglomeration. The luminescent properties of Ce ions in )Al5O12∶Ce0.1 have been studied, and it was found that the emission band shifted toward a longer wavelength. The redshift is attributed to the lowering of the 5d energy level centroid of Ce, which can be explained by the nephelauxetic effect and compression effect. These phosphors were coated on blue light-emitting diode (LED) chips to fabricate white light-emitting diodes (WLEDs), and their color-rendering indices, color temperatures, and luminous efficiencies were measured. As a consequence of the addition of Tb, the blue LED pumped )Al5O12∶Ce0.1 phosphors WLEDs showed good optical properties.

  1. Photoluminescence properties of a novel cyclometalated iridium(III) complex with coumarin-boronate and its recognition of hydrogen peroxide.

    PubMed

    Li, Chunxiang; Wang, Shuqin; Huang, Yangmei; Wen, Qin; Wang, Lei; Kan, Yuhe

    2014-04-14

    A novel neutral iridium(III) complex-based phosphorescent probe (Ir-2) for hydrogen peroxide (H2O2) has been designed and synthesized by incorporating a benzeneboronic acid pinacol ester (bpe) moiety into 3-(benzothiazol-2-yl)-7-hydroxy-coumarin (Bthc) as a cyclometalated ligand (Bthc-bpe). The photophysical behavior of Ir-2 was investigated by UV-Vis absorption spectroscopy, photoluminescence spectroscopy, and quantum mechanical calculations. The absorption spectra of the complex Ir-2 are dominated by the cyclometalated ligand; thus it shows an intense absorption band in the visible region at 460 nm with a molar extinction coefficient (ε) of about 3 × 10(4) M(-1) cm(-1), which is rarely found for typical polypyridine iridium(III) complexes. The complex Ir-2 displays efficient phosphorescent emission at 560 nm at room temperature originating from a mixed triplet metal-to-ligand charge-transfer ((3)MLCT, dπ(Ir) → π* (Bthc-bpe)) and triplet intraligand ((3)ILCT, π-π* (Bthc-bpe)) excited states as suggested by the DFT computational studies. Upon reaction with H2O2, the complex displays an emission decrease induced by an intense intermolecular aggregation due to the cleavage of the bulky benzeneboronic acid pinacol ester substituent, indicating that Ir-2 could act as an ON-OFF-type phosphorescent probe for H2O2. Additionally, selectivity studies reveal that the complex Ir-2 possesses high selectivity toward H2O2 over other reactive oxygen species (ROS).

  2. Characteristic properties of Raman scattering and photoluminescence on ZnO crystals doped through phosphorous-ion implantation

    SciTech Connect

    Jeong, T. S.; Yu, J. H.; Mo, H. S.; Kim, T. S.; Lim, K. Y.; Youn, C. J.; Hong, K. J.

    2014-02-07

    P-doped ZnO was fabricated by means of the ion-implantation method. At the Raman measurement, the blue shift of the E{sub 2}{sup high} mode and A{sub 1}(LO) phonon of the inactive mode were observed after the P-ion implantation. It suggested to be caused by the compressive stress. Thus, Hall effect measurement indicates that the acceptor levels exists in P-doped ZnO while still maintaining n-type ZnO. From the X-ray photoelectron spectroscopy, the chemical bond formation of the P2p{sub 3/2} spectrum consisted of 2(P{sub 2}O{sub 5}) molecules. Therefore, the implanted P ions were substituted to the Zn site in ZnO. From the photoluminescence (PL) spectra, P-related PL peaks were observed in the energy ranges of 3.1 and 3.5 eV, and its origin was analyzed at P{sub Zn}-2V{sub Zn} complexes, acting as a shallow acceptor. With increasing temperatures, the neutral-acceptor bound-exciton emission, (A{sup 0}, X), shows a tendency to quench the intensity and extend the emission linewidth. From the relations of the intensity and the linewidth as a function of temperature, the broadening of linewidth was believed to the result that the vibration mode of E{sub 2}{sup high} participates in the broadening process of (A{sup 0}, X) and the change of luminescent intensity was attributed to the partial dissociation of (A{sup 0}, X). Consequently, these facts indicate that the acceptor levels existed in P-doped ZnO layer by the ion implantation.

  3. Structural and photoluminescence properties of silicon nanowires extracted by means of a centrifugation process from plasma torch synthesized silicon nanopowder

    NASA Astrophysics Data System (ADS)

    Le Borgne, Vincent; Agati, Marta; Boninelli, Simona; Castrucci, Paola; De Crescenzi, Maurizio; Dolbec, Richard; El Khakani, My Ali

    2017-07-01

    We report on a method for the extraction of silicon nanowires (SiNWs) from the by-product of a plasma torch based spheroidization process of silicon. This by-product is a nanopowder which consists of a mixture of SiNWs and silicon particles. By optimizing a centrifugation based process, we were able to extract substantial amounts of highly pure Si nanomaterials (mainly SiNWs and Si nanospheres (SiNSs)). While the purified SiNWs were found to have typical outer diameters in the 10-15 nm range and lengths of up to several μm, the SiNSs have external diameters in the 10-100 nm range. Interestingly, the SiNWs are found to have a thinner Si core (2-5 nm diam.) and an outer silicon oxide shell (with a typical thickness of ˜5-10 nm). High resolution transmission electron microscopy (HRTEM) observations revealed that many SiNWs have a continuous cylindrical core, whereas others feature a discontinuous core consisting of a chain of Si nanocrystals forming a sort of ‘chaplet-like’ structures. These plasma-torch-produced SiNWs are highly pure with no trace of any metal catalyst, suggesting that they mostly form through SiO-catalyzed growth scheme rather than from metal-catalyzed path. The extracted Si nanostructures are shown to exhibit a strong photoluminescence (PL) which is found to blue-shift from 950 to 680 nm as the core size of the Si nanostructures decreases from ˜5 to ˜3 nm. This near IR-visible PL is shown to originate from quantum confinement (QC) in Si nanostructures. Consistently, the sizes of the Si nanocrystals directly determined from HRTEM images corroborate well with those expected by QC theory.

  4. Si-rich Al2O3 films grown by RF magnetron sputtering: structural and photoluminescence properties versus annealing treatment

    PubMed Central

    2013-01-01

    Silicon-rich Al2O3 films (Six(Al2O3)1−x) were co-sputtered from two separate silicon and alumina targets onto a long silicon oxide substrate. The effects of different annealing treatments on the structure and light emission of the films versus x were investigated by means of spectroscopic ellipsometry, X-ray diffraction, micro-Raman scattering, and micro-photoluminescence (PL) methods. The formation of amorphous Si clusters upon the deposition process was found for the films with x ≥ 0.38. The annealing treatment of the films at 1,050°C to 1,150°C results in formation of Si nanocrystallites (Si-ncs). It was observed that their size depends on the type of this treatment. The conventional annealing at 1,150°C for 30 min of the samples with x = 0.5 to 0.68 leads to the formation of Si-ncs with the mean size of about 14 nm, whereas rapid thermal annealing of similar samples at 1,050°C for 1 min showed the presence of Si-ncs with sizes of about 5 nm. Two main broad PL bands were observed in the 500- to 900-nm spectral range with peak positions at 575 to 600 nm and 700 to 750 nm accompanied by near-infrared tail. The low-temperature measurement revealed that the intensity of the main PL band did not change with cooling contrary to the behavior expected for quantum confined Si-ncs. Based on the analysis of PL spectrum, it is supposed that the near-infrared PL component originates from the exciton recombination in the Si-ncs. However, the most intense emission in the visible spectral range is due to either defects in matrix or electron states at the Si-nc/matrix interface. PMID:23758885

  5. A 3D porous zinc MOF constructed from a flexible tripodal ligand: Synthesis, structure, and photoluminescence property

    SciTech Connect

    Wen Lili; Wang Dong'e; Wang Chenggang; Wang Feng; Li Dongfeng Deng Kejian

    2009-03-15

    A new metal-organic framework, [Zn{sub 5}(trencba){sub 2}(OH){sub 2}Cl{sub 2}.4H{sub 2}O] (1) [H{sub 3}trencba=N,N,N',N',N'',N''-tris[(4-carboxylate-2-yl)methyl]-tris (2-aminoethyl)amine], constructed from a flexible tripodal ligand based on C{sub 3} symmetric tris(2-aminoethyl)amine, has been synthesized hydrothermally and characterized by elemental analysis, IR, TG, XRD and single-crystal X-ray diffraction analysis. Compound 1 contains an unprecedented linear penta-nuclear zinc cluster fragment. Each ligand links four penta-nuclear fragments, and every fragment links eight ligands to generate a three-dimensional non-interpenetrated porous framework. The uncoordinated water molecules were observed trapped in the void pores. Compound 1 represents the first example of (6,8)-connected 3D bi-nodal framework based on a single kind of organic ligand. The photoluminescence measurements showed that complex 1 exhibits relatively stronger blue emissions at room temperature than that of the ligand. - Graphical abstract: The MOF [Zn{sub 5}(trencba){sub 2}(OH){sub 2}Cl{sub 2}.4H{sub 2}O] (H{sub 3}trencba=N,N,N',N',N',N'-tris[(4-carboxylate-2-yl)methyl]-tris (2-aminoethyl)amine) reveals a (6,8)-connected bi-nodal three-dimensional porous framework with unprecedented penta-nuclear fragment, which appears to be a good candidate of hybrid inorganic-organic photoactive materials.

  6. Two-dimensional silica: Structural, mechanical properties, and strain-induced band gap tuning

    SciTech Connect

    Gao, Enlai; Xie, Bo; Xu, Zhiping

    2016-01-07

    Two-dimensional silica is of rising interests not only for its practical applications as insulating layers in nanoelectronics, but also as a model material to understand crystals and glasses. In this study, we examine structural and electronic properties of hexagonal and haeckelite phases of silica bilayers by performing first-principles calculations. We find that the corner-sharing SiO{sub 4} tetrahedrons in these two phases are locally similar. The robustness and resilience of these tetrahedrons under mechanical perturbation allow effective strain engineering of the electronic structures with band gaps covering a very wide range, from of that for insulators, to wide-, and even narrow-gap semiconductors. These findings suggest that the flexible 2D silica holds great promises in developing nanoelectronic devices with strain-tunable performance, and lay the ground for the understanding of crystalline and vitreous phases in 2D, where bilayer silica provides an ideal test-bed.

  7. Magneto-resistive property study of direct and indirect band gap thermoelectric Bi-Sb alloys

    NASA Astrophysics Data System (ADS)

    Das, Diptasikha; Malik, K.; Bandyopadhyay, S.; Das, D.; Chatterjee, S.; Banerjee, Aritra

    2014-08-01

    We report magneto-resistive properties of direct and indirect band gap Bismuth-Antimony (Bi-Sb) alloys. Band gap increases with magnetic field. Large positive magnetoresistance (MR) approaching to 400% is observed. Low field MR experiences quadratic growth and at high field it follows a nearly linear behavior without sign of saturation. Carrier mobility extracted from low field MR data depicts remarkable high value of around 5 m2V-1s-1. Correlation between MR and mobility is revealed. We demonstrate that the strong nearly linear MR at high field can be well understood by classical method, co-build by Parish and Littlewood, Nature 426, 162 (2003) and Phys. Rev. B 72, 094417 (2005).

  8. Room-temperature synthesis of three-dimensional porous ZnO@CuNi hybrid magnetic layers with photoluminescent and photocatalytic properties

    PubMed Central

    Guerrero, Miguel; Zhang, Jin; Altube, Ainhoa; García-Lecina, Eva; Roldan, Mònica; Baró, Maria Dolors; Pellicer, Eva; Sort, Jordi

    2016-01-01

    Abstract A facile synthetic approach to prepare porous ZnO@CuNi hybrid films is presented. Initially, magnetic CuNi porous layers (consisting of phase separated CuNi alloys) are successfully grown by electrodeposition at different current densities using H2 bubbles as a dynamic template to generate the porosity. The porous CuNi alloys serve as parent scaffolds to be subsequently filled with a solution containing ZnO nanoparticles previously synthesized by sol-gel. The dispersed nanoparticles are deposited dropwise onto the CuNi frameworks and the solvent is left to evaporate while the nanoparticles impregnate the interior of the pores, rendering ZnO-coated CuNi 3D porous structures. No thermal annealing is required to obtain the porous films. The synthesized hybrid porous layers exhibit an interesting combination of tunable ferromagnetic and photoluminescent properties. In addition, the aqueous photocatalytic activity of the composite is studied under UV−visible light irradiation for the degradation of Rhodamine B. The proposed method represents a fast and inexpensive approach towards the implementation of devices based on metal-semiconductor porous systems, avoiding the use of post-synthesis heat treatment steps which could cause deleterious oxidation of the metallic counterpart, as well as collapse of the porous structure and loss of the ferromagnetic properties. PMID:27877868

  9. Room-temperature synthesis of three-dimensional porous ZnO@CuNi hybrid magnetic layers with photoluminescent and photocatalytic properties.

    PubMed

    Guerrero, Miguel; Zhang, Jin; Altube, Ainhoa; García-Lecina, Eva; Roldan, Mònica; Baró, Maria Dolors; Pellicer, Eva; Sort, Jordi

    2016-01-01

    A facile synthetic approach to prepare porous ZnO@CuNi hybrid films is presented. Initially, magnetic CuNi porous layers (consisting of phase separated CuNi alloys) are successfully grown by electrodeposition at different current densities using H2 bubbles as a dynamic template to generate the porosity. The porous CuNi alloys serve as parent scaffolds to be subsequently filled with a solution containing ZnO nanoparticles previously synthesized by sol-gel. The dispersed nanoparticles are deposited dropwise onto the CuNi frameworks and the solvent is left to evaporate while the nanoparticles impregnate the interior of the pores, rendering ZnO-coated CuNi 3D porous structures. No thermal annealing is required to obtain the porous films. The synthesized hybrid porous layers exhibit an interesting combination of tunable ferromagnetic and photoluminescent properties. In addition, the aqueous photocatalytic activity of the composite is studied under UV-visible light irradiation for the degradation of Rhodamine B. The proposed method represents a fast and inexpensive approach towards the implementation of devices based on metal-semiconductor porous systems, avoiding the use of post-synthesis heat treatment steps which could cause deleterious oxidation of the metallic counterpart, as well as collapse of the porous structure and loss of the ferromagnetic properties.

  10. Surfactant-assisted hydrothermal synthesis of octahedral structured NaGd(MoO4)2:Eu3+/Tb3+ and tunable photoluminescent properties

    NASA Astrophysics Data System (ADS)

    Jiang, Yingying; Liu, Yan; Liu, Guixia; Dong, Xiangting; Wang, Jinxian; Yu, Wensheng; Dong, Qun

    2014-09-01

    NaGd(MoO4)2:Eu3+/Tb3+ phosphors were synthesized via a facile hydrothermal method with a surfactant-assisted environment. The properties were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and photoluminescence (PL). The XRD patterns and FESEM image indicate that NaGd(MoO4)2:Eu3+/Tb3+ phosphors crystallize well with the scheelite structure and the morphology of the sample is octahedral. The octahedral morphology of the phosphors is found to be manipulated by the glutamic acid. The luminescent properties reveal that under 277 nm excitation, Eu3+ and Tb3+ doped NaGd(MoO4)2 phosphors show strong red and green emission. Moreover, Eu3+ and Tb3+ co-doped NaGd(MoO4)2 phosphors display the multicolor luminescence when excited by a single excitation wavelength or different excitation wavelengths, and the luminescence colors of the samples can be tuned from red, yellow, yellow-green, to green when adjusting the doping concentration of the activator ions. Furthermore, the possible energy transfer mechanism in Tb3+ and Eu3+ co-doped NaGd(MoO4)2 was proposed in term of the experimental results and analysis. The as-prepared phosphors may find potential applications in the field such as color displays.

  11. Synthesis and photoluminescent properties of cuboid-like Y2(C2O4)3:Tb3+ green-emitting phosphors

    NASA Astrophysics Data System (ADS)

    Ye, Menglin; Zhou, Liqun; Hong, Fei; Li, Ling; Xia, Qinghua; Yang, Kunzhou; Xiong, Xing

    2015-09-01

    In this paper, the Tb3+-doped Y2(C2O4)3 phosphors were prepared using the hydrothermal method in the presence of surfactants. XRD, SEM and fluorescence spectroscopy were used to study the structure and luminescence properties of the material. The effects of surfactants and pH values on the morphologies and photoluminescent properties of Y2(C2O4)3:Tb3+ phosphors were investigated, respectively. When surfactant CA (Citric Acid) and pH 1.5 were employed, homogeneous cuboid-like structure phosphor was obtained, and it was composed of a small number of homogeneous particles with sizes of 2-4 μm and showed higher luminescent intensity than phosphors prepared with surfactants EDTA, Glycine and PEG. Under the 370 nm radiation excitation, Y2-x(C2O4)3:xTb3+ phosphors exhibit green emission (546 nm) corresponding to the 5D4 → 7F5 transition of Tb3+. The emission intensity of this phosphor can be influenced by Tb3+ doping concentration and the maximum intensity of luminescence is observed at the Tb3+ concentration around x = 1.4. The corresponding concentration quenching mechanism is verified as quadrupole-quadrupole interaction. The CIE chromaticity coordinates values of Y0.6 (C2O4)3:1.4Tb3+ almost locate in the green region.

  12. Effect of Substituents and Initial Degree of Functionalization of Alkylated Single-Walled Carbon Nanotubes on Their Thermal Stability and Photoluminescence Properties.

    PubMed

    Maeda, Yutaka; Takehana, Yuya; Dang, Jing-Shuang; Suzuki, Mitsuaki; Yamada, Michio; Nagase, Shigeru

    2017-02-03

    Alkylated single-walled carbon nanotubes (SWNTs) have been thermally treated to determine the influence of substituents and the degree of functionalization on their thermal stability and photoluminescence (PL) properties. Alkylated SWNTs were prepared by treating SWNTs with sodium naphthalenide and alkyl bromide. The defunctionalization of the alkylated SWNTs was monitored by absorption and Raman spectra. Selective recovery of the characteristic absorption and radial breathing mode peaks was observed during the thermal treatment, which indicates that the thermal stability of the alkylated SWNTs decreases with increases in SWNT diameter and degree of functionalization. n-Butylated and phenethylated SWNTs showed higher thermal stability than sec-butylated and benzylated SWNTs for a similar degree of functionalization, respectively. The diameter selectivity and effect of substituents on the thermal elimination reaction were confirmed by density functional theory. In addition, it was shown that the initial degree of functionalization of the alkylated SWNTs, with the alkyl group and degree of functionalization being kept constant after thermal treatment, strongly affects their PL properties; Stokes shift, and PL peak intensity.

  13. Enhanced Photoluminescence and Raman Properties of Al-Doped ZnO Nanostructures Prepared Using Thermal Chemical Vapor Deposition of Methanol Assisted with Heated Brass

    PubMed Central

    Thandavan, Tamil Many K.; Gani, Siti Meriam Abdul; San Wong, Chiow; Md. Nor, Roslan

    2015-01-01

    Vapor phase transport (VPT) assisted by mixture of methanol and acetone via thermal evaporation of brass (CuZn) was used to prepare un-doped and Al-doped zinc oxide (ZnO) nanostructures (NSs). The structure and morphology were characterized by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). Photoluminescence (PL) properties of un-doped and Al-doped ZnO showed significant changes in the optical properties providing evidence for several types of defects such as zinc interstitials (Zni), oxygen interstitials (Oi), zinc vacancy (Vzn), singly charged zinc vacancy (VZn-), oxygen vacancy (Vo), singly charged oxygen vacancy (Vo+) and oxygen anti-site defects (OZn) in the grown NSs. The Al-doped ZnO NSs have exhibited shifted PL peaks at near band edge (NBE) and red luminescence compared to the un-doped ZnO. The Raman scattering results provided evidence of Al doping into the ZnO NSs due to peak shift from 145 cm-1 to an anomalous peak at 138 cm-1. Presence of enhanced Raman signal at around 274 and 743 cm-1 further confirmed Al in ZnO NSs. The enhanced D and G band in all Al-doped ZnO NSs shows possible functionalization and doping process in ZnO NSs. PMID:25756598

  14. Enhanced photoluminescence and Raman properties of Al-Doped ZnO nanostructures prepared using thermal chemical vapor deposition of methanol assisted with heated brass.

    PubMed

    Thandavan, Tamil Many K; Gani, Siti Meriam Abdul; San Wong, Chiow; Md Nor, Roslan

    2015-01-01

    Vapor phase transport (VPT) assisted by mixture of methanol and acetone via thermal evaporation of brass (CuZn) was used to prepare un-doped and Al-doped zinc oxide (ZnO) nanostructures (NSs). The structure and morphology were characterized by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). Photoluminescence (PL) properties of un-doped and Al-doped ZnO showed significant changes in the optical properties providing evidence for several types of defects such as zinc interstitials (Zni), oxygen interstitials (Oi), zinc vacancy (Vzn), singly charged zinc vacancy (VZn-), oxygen vacancy (Vo), singly charged oxygen vacancy (Vo+) and oxygen anti-site defects (OZn) in the grown NSs. The Al-doped ZnO NSs have exhibited shifted PL peaks at near band edge (NBE) and red luminescence compared to the un-doped ZnO. The Raman scattering results provided evidence of Al doping into the ZnO NSs due to peak shift from 145 cm-1 to an anomalous peak at 138 cm-1. Presence of enhanced Raman signal at around 274 and 743 cm-1 further confirmed Al in ZnO NSs. The enhanced D and G band in all Al-doped ZnO NSs shows possible functionalization and doping process in ZnO NSs.

  15. Photoluminescence properties and energy transfer of color tunable MgZn₂(PO₄)₂:Ce³⁺,Tb³⁺ phosphors.

    PubMed

    Xu, Mengjiao; Wang, Luxiang; Jia, Dianzeng; Zhao, Hongyang

    2015-11-21

    A series of Ce(3+)/Tb(3+) co-doped MgZn2(PO4)2 phosphors have been synthesized by the co-precipitation method. Their structure, morphology, photoluminescence properties, decay lifetime, thermal stability and luminous efficiency were investigated. The possible energy transfer mechanism was proposed based on the experimental results and detailed luminescence spectra and decay curves of the phosphors. The critical distance between Ce(3+) and Tb(3+) ions was calculated by both the concentration quenching method and the spectral overlap method. The energy transfer mechanism from the Ce(3+) to Tb(3+) ion was determined to be dipole-quadrupole interaction, and the energy transfer efficiency was 85%. By utilizing the principle of energy transfer and appropriate tuning of Ce(3+)/Tb(3+) contents, the emission color of the obtained phosphors can be tuned from blue to green light. The MgZn2(PO4)2:Ce(3+),Tb(3+) phosphor is proved to be a promising UV-convertible material capable of green light emitting in UV-LEDs due to its excellent thermal stability and luminescence properties.

  16. Synthesis, crystal structures, mesomorphic and photo-luminescent properties of 1,3,4-thia(oxa)diazole-based compounds with a terminal methoxy or methylthio group

    NASA Astrophysics Data System (ADS)

    Han, Jie; Chang, Xiao-Yong; Wang, Yan-Mei; Pang, Mei-Li; Meng, Ji-Ben

    2009-11-01

    A series of aromatically 2,5-disubstituted 1,3,4-thia(oxa)diazoles with a terminal methoxy or methylthio group were synthesized and characterized by means of 1H NMR, 13C NMR, MS and elemental analysis. The X-ray crystal structures of compounds 1a and 3b revealed that both of them adopted layered arrangement without short intermolecular interactions. The liquid crystal properties have been investigated by means of polarizing optical microscopy (POM), differential scanning calorimetry (DSC), variable temperature X-ray diffraction (VXRD) and thermogravimetric analysis (TGA). All compounds (except 2a and 2b) exhibited various mesophases (nematic, smectic C and/or smectic A) with wide temperature ranges and good thermal stability. In CH 2Cl 2 solution, all these compounds displayed a room temperature emission with λmax at 371-425 nm and quantum yields of 0.25-0.83. The effect of the sulfur and oxygen atoms on mesomorphic and photo-luminescent properties was discussed according to the positions in the central heterocyclic rings and the terminal groups.

  17. Structural, photoluminescent and photocatalytic properties of TiO2:Eu3+ coatings formed by plasma electrolytic oxidation

    NASA Astrophysics Data System (ADS)

    Stojadinović, Stevan; Radić, Nenad; Grbić, Boško; Maletić, Slavica; Stefanov, Plamen; Pačevski, Aleksandar; Vasilić, Rastko

    2016-05-01

    In this paper, we used plasma electrolytic oxidation (PEO) of titanium in water solution containing 10 g/L Na3PO4·12H2O + 2 g/L Eu2O3 powder for preparation of TiO2:Eu3+ coatings. The surfaces of obtained coatings exhibit a typical PEO porous structure. The energy dispersive X-ray spectroscopy analysis showed that the coatings are mainly composed of Ti, O, P, and Eu; it is observed that Eu content in the coatings increases with PEO time. The X-ray diffraction analysis indicated that the coatings are crystallized and composed of anatase and rutile TiO2 phases, with anatase being the dominant one. X-ray photoelectron spectroscopy revealed that Ti 2p spin-orbit components of TiO2:Eu3+ coatings are shifted towards higher binding energy, with respect to pure TiO2 coatings, suggesting that Eu3+ ions are incorporated into TiO2 lattice. Diffuse reflectance spectroscopy showed that TiO2:Eu3+ coatings exhibit evident red shift with respect to the pure TiO2 coatings. Photoluminescence (PL) emission spectra of TiO2:Eu3+ coatings are characterized by sharp emission bands in orange-red region ascribed to f-f transitions of Eu3+ ions from excited level 5D0 to lower levels 7FJ (J = 0, 1, 2, 3, and 4). The excitation PL spectra of TiO2:Eu3+ coatings can be divided into two regions: the broad band region from 250 nm to 350 nm associated with charge transfer state of Eu3+ and the series of sharp peaks in the range from 350 nm to 550 nm corresponding to direct excitation of the Eu3+ ions. It is observed that the intensity of peaks in excitation and emission PL spectra increases with the concentration of Eu3+, but the peak positions remain practically unchanged. The ratio of PL emission for electric and magnetic dipole transitions indicates highly asymmetric environment around Eu3+ ions. The photocatalytic activity (PA) of TiO2:Eu3+ coatings is evaluated by measuring the photodegradation of methyl orange under simulated sunlight conditions. It is shown that PEO time, i.e., the amount

  18. New in situ generated acylhydrazidate-coordinated complexes and acylhydrazide molecules: Synthesis, structural characterization and photoluminescence property

    NASA Astrophysics Data System (ADS)

    Wang, Yan-Ning; Huo, Qi-Sheng; Zhang, Ping; Yu, Jie-Hui; Xu, Ji-Qing

    2016-10-01

    By utilizing the hydrothermal in situ acylation of organic acids with N2H4, three acylhydrazidate-coordinated compounds [Mn(L1)2(H2O)2] (L1 = 2,3-quinolinedicarboxylhydrazidate; HL1 = 2,3-dihydropyridazino[4,5-b] quinoline-1,4-dione) 1, [Mn2(ox)(L2)2(H2O)6]·2H2O (L2 = benzimidazolate-5,6-dicarboxylhydrazide; HL2 = 6,7-dihydro-1H-imidazo[4,5-g]phthalazine-5,8-dione; ox = oxalate) 2, and [Cd(HL3)(bpy)] (L3 = 4,5-di(3‧-carboxylphenyl)phthalhydrazidate; H3L3 = 6,7-dihydro-1H-imidazo[4,5-g]phthalazine-5,8-dione; bpy = 2,2‧-bipyridine) 3, as well as two acylhydrazide molecules L4 (L4 = oxepino[2,3,4-de:7,6,5-d‧e‧]diphthalazine-4,10(5H,9H)-dione) 4 and L5 (L5 = 4,5-dibromophthalhydrazide; L5 = 6,7-dibromo-2,3-dihydrophthalazine-1,4-dione) 5 were obtained. X-ray single-crystal diffraction analysis reveals that (i) 1 only possesses a mononuclear structure, but it self-assembles into a 2-D supramolecular network via the Nhydrazinesbnd H ⋯ Nhydrazine and Owsbnd H ⋯ Ohydroxylimino interactions; (ii) 2 exhibits a dinuclear structure. Ox acts as the linker, while L2 just serves as a terminal ligand; (iii) In 3, L3 acts as a 3-connected node to propagate the 7-coordinated Cd2 + centers into a 1-D double-chain structure; (iv) 4 is a special acylhydrazide molecule. Two sbnd OH groups for the intermediates 3,3‧-biphthalhydrazide further lose one water molecule to form 4; (v) 5 is a common monoacylhydrazide molecule. Via the Nhydrazinesbnd H ⋯ Ohydrazine, Ohydroxyliminosbnd H ⋯ Oacylamino and the π ⋯ π interactions, it self-assembles into a 2-D supramolecular network. The photoluminescence analysis reveals that 4 emits light with the maxima at 510 nm.

  19. Preparation, photoluminescent properties and luminescent dynamics of BaAlF{sub 5}:Eu{sup 2+} nanophosphors

    SciTech Connect

    Zhang, Wei; Hua, Ruinian; Liu, Tianqing; Zhao, Jun; Na, Liyan; Chen, Baojiu

    2014-12-15

    Graphical abstract: Rice-shaped BaAlF{sub 5}:Eu{sup 2+} nanophosphors were synthesized via one-pot hydrothermal process. The as-prepared BaAlF{sub 5}:Eu{sup 2+} are composed of many particles with an average diameter of 40 nm. When excited at 260 nm, the sharp line emission located at 361 nm of Eu{sup 2+} was observed. The optimum doping concentration of Eu{sup 2+} was confirmed to be 5 mol%. The strong ultraviolet emission of Eu{sup 2+} ions in BaAlF{sub 5}:Eu{sup 2+} nanoparticles suggests that these nanoparticles may have potential applications for sensing, solid-state lasers and spectrometer calibration. - Highlights: • BaAlF{sub 5}:Eu{sup 2+} nanophosphors were synthesized via a mild hydrothermal process. • The Van and Huang models were used to research the mechanism of concentration quenching. • The optimum doping concentration of Eu2+ was confirmed to be 5 mol%. - Abstract: Eu{sup 2+}-doped BaAlF{sub 5} nanophosphors were synthesized via a facile one-pot hydrothermal method. The final products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy. XRD results showed that the prepared samples are single-phase. The FE-SEM and TEM images indicated that the prepared BaAlF{sub 5}:Eu{sup 2+} nanophosphors are composed of many rice-shaped particles with an average diameter of 40 nm. When excited at 260 nm, BaAlF{sub 5}:Eu{sup 2+} nanophosphors exhibit the sharp line emissions of Eu{sup 2+} at room temperature. The optimum doping concentration of Eu{sup 2+} was confirmed to be 5 mol%. The Van and Huang models were used to study the mechanism of concentration quenching and the electric dipole–dipole interaction between Eu{sup 2+} can be deduced to be a dominant for quenching fluorescence in BaAlF{sub 5}:Eu{sup 2+} nanophosphors. The strong ultraviolet emission of Eu{sup 2+} in BaAlF{sub 5}:Eu{sup 2+} nanophosphors suggests that

  20. Facile fabrication and photoluminescence properties of rare-earth-doped Gd₂O₃ hollow spheres via a sacrificial template method.

    PubMed

    Gao, Yu; Zhao, Qian; Fang, Qinghong; Xu, Zhenhe

    2013-08-21

    Rare-earth-doped gadolinium oxide (Gd₂O₃) hollow spheres were successfully fabricated on a large scale by using PS spheres as sacrificed templates and urea as a precipitating agent, which involved the deposition of an inorganic coating Gd(OH)CO3 on the surface of PS spheres and subsequent calcination in the air. Various approaches including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), as well as photoluminescence spectroscopies were used to characterize the samples. The results indicate that the sample is composed of uniform hollow Gd₂O₃ spheres with a mean particle size of about 2.3 μm and these hollow spheres have the mesoporous shell that are composed of a large amount of nanoparticles. The possible mechanism of evolution from PS spheres to the amorphous precursor and to the final hollow Gd₂O₃ spheres have been proposed. The as-obtained samples show strong light emission with different colors corresponding to different Ln³⁺ ions under ultraviolet-visible light and electron-beam excitation. Under 980 nm NIR irradiation, Gd₂O₃:Ln³⁺ (Ln³⁺ = Yb³⁺/Er³⁺, Yb³⁺/Tm³⁺ and Yb³⁺/Ho³⁺) exhibit characteristic up-conversion (UC) emissions of red (Er³⁺, ²H11/2, ⁴S3/2, ⁴F9/2 → ⁴I15/2), blue (Tm³⁺, ¹G₄ → ³H₆) and green (Ho³⁺, ⁵F₄, ⁵S₂ → ⁵I₈), respectively. These merits of multicolor emissions in the visible region endow these kinds of materials with potential applications in the field of light display systems, lasers, optoelectronic devices, and MRI contrast agents.

  1. Auxiliary aromatic-acid effect on the structures of a series of Zn{sup II} coordination polymers: Syntheses, crystal structures, and photoluminescence properties

    SciTech Connect

    Xu Yanhong; Lan Yaqian; Shao Kuizhan; Su Zhongmin; Liao Yi

    2010-04-15

    Five novel Zn{sup II}-(pyridyl)imidazole derivative coordination polymers, [Zn(L){sub 2}] (1), [Zn{sub 2}(mu{sub 3}-OH)L(m-BDC)] (2), [Zn{sub 2}(mu{sub 3}-OH)L(p-BDC)].H{sub 2}O (3), [Zn{sub 2}L(BTC)(H{sub 2}O)].2.5H{sub 2}O (4) and [Zn{sub 3.5}(mu{sub 3}-OH)L{sub 2}(BTEC)(H{sub 2}O)].H{sub 2}O (5) (L=4-((2-(pyridine-2-yl)-1H-imidazol-1-yl)methyl)benzoic acid, p-H{sub 2}BDC=1,4-benzenedicarboxylic acid, m-H{sub 2}BDC=1,3-benzenedicarboxylic acid, H{sub 3}BTC=1,3,5-benzenetricarboxylic acid, H{sub 4}BTEC=1,2,4,5-benzenetetracarboxylic acid), were successfully synthesized under hydrothermal conditions through varying auxiliary aromatic-acid ligands and structurally characterized by X-ray crystallography. Compound 1 exhibits a 1D chain linked via double L bridges. Compound 2 features a well-known pcu topology with bent dicarboxylate ligand (m-H{sub 2}BDC) as an auxiliary ligand, while 3 displays a bcu network with linear dicarboxylate ligand (p-H{sub 2}BDC) as an auxiliary ligand. The structure of compound 4 is a novel 3D (3,5)-connected network with (4.6{sup 2})(4.6{sup 4}.8{sup 2}.10.12{sup 2}) topology. It is interesting that compound 5 shows an intricate (3,4,8)-connected framework with (4.6{sup 2})(4{sup 2}.6{sup 3}.8)(4{sup 2}.6{sup 4})(4{sup 2}.6{sup 18}.7.8{sup 6}.10) topology. In addition, their infrared spectra (IR), X-ray powder diffraction (XPRD) and photoluminescent properties were also investigated in detail. - Graphical abstract: Five novel Zn{sup II}-organic architectures have been hydrothermally synthesized through varying auxiliary aromatic-acid ligands and characterized by X-ray diffraction, the photoluminescence properties of compounds 1-5 were studied.

  2. Green engineered ZnO nanopowders by Banyan Tree and E. tirucalli plant latex: auto ignition route, photoluminescent and photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Anilkumar, M. R.; Nagaswarupa, H. P.; Anantharaju, K. S.; Gurushantha, K.; Pratapkumar, C.; Prashantha, S. C.; Shashi Shekhar, T. R.; Nagabhushana, H.; Sharma, S. C.; Vidya, Y. S.; Prasad, Daruka

    2015-03-01

    A simple and eco-friendly solution combustion route was used to prepare ZnO nanoparticles (ZNPs) using Banyan Tree (BT) and Euphorbia tirucalli (ET) plant latexes as fuels. The final products were characterized by powder x-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), UV-visible, scanning electron microcopy (SEM) and transmission electron microscopy (TEM). The PXRD result reveals the formation of hexagonal phase with Wurtzite structure. The crystallite size obtained from TEM was found to be ˜20-25 nm. SEM results reveal rose-like morphology with BT latex and hexagonal shaped with ET latex. The energy band gap of ZNPs obtained by BT and ET latex were found to be 3.20 and 3.38 eV, respectively. Photoluminescence (PL) emission peaks at ˜421, 458, 505, 522, 628 and 695 nm were observed in both the samples when excited at 383 nm. These emission peaks were mainly attributed to deep level oxygen (blue-green) defect and exciton (UV) defects, respectively. The international commission on illumination (CIE) chromaticity co-ordinates, as well as co-ordinated color temperature (CCT), were estimated from the emission spectra; the values (x, y) were very close to national television system committee (NTSC) standard values of pure white emission. Photocatalytic activity (PCA) of ZNPs prepared was studied in detail. The ZNPs prepared using BT latex showed highest PCA under sunlight. The results demonstrate that the synthesized product could be quite useful for display applications as well as photocatalyst. Further, the material prepared by this route was found to be non-toxic, environmentally friendly and could be a potential alternative to economical routes.

  3. Investigation on multiferroic, optical and photoluminescence properties of CoFe2O4/(Pb1-xSrx)TiO3 nanostructured composite thin films

    NASA Astrophysics Data System (ADS)

    Bala, Kanchan; Sharma, Pankaj; Negi, N. S.

    2016-11-01

    Multiferroic nanostructured composite thin films consisting of CoFe2O4 (CFO) and Pb1-xSrxTiO3 (PST; x = 0.1, 0.2, 0.3, 0.4 and 0.5) layers have been deposited on Pt/TiO2/SiO2/Si and quartz substrates by using metallo-organic decomposition process and spin coating. The effect of Sr content on the multiferroic and optical properties have been investigated. The phase purity such as spinel structure of CFO and perovskite structure of PST has been verified by X-ray diffraction. Cross-sectional scanning electron microscopy images revealed clear interface between CFO and PST layers without any noticeable diffusion. The multiferroic properties of CFO/PST composite films have been confirmed by magnetic and ferroelectric hysteresis loops with low leakage current density. The residual strain sensitivity of multiferroic and optical properties has been observed in the composite films. The decrease in saturation magnetization and saturation polarization with increase in Sr content has been observed which could be attributed to the decrease in residual strain of CFO/PST composite films. The magnetic phase transition temperature of the CFO/PST composite films is also reduced. The optical refractive index decreases with increase of amount of Sr content. The photoluminescence spectra of the CFO/PST composite films possess a blue shift which can be attributed to the Pb and oxygen vacancies as localized sensitizing centers. We show that the multiferroic and optical properties of the CFO/PST composite films are highly sensitive to the heterostructure strains which can be controlled by Sr content.

  4. Hydrothermal synthesis of Y{sub 2}O{sub 3} coated Y{sub 2}O{sub 3}:Eu{sup 3+} nanotubes for enhanced photoluminescence properties

    SciTech Connect

    Gao, Linhui; Wang, Guangfa; Zhu, Hongliang; Zhou, Weijie; Ou, Guofu

    2015-10-15

    Highlights: • Eu{sup 3+} doped Y{sub 2}O{sub 3} nanotubes. • Hydrothermal synthesis of Y{sub 2}O{sub 3} coated Y{sub 2}O{sub 3}:Eu{sup 3+} nanostructures assissted with a further heat treatment. • Tunable coating ratios of Y{sub 2}O{sub 3} coated Y{sub 2}O{sub 3}:Eu{sup 3+} nanophosphor. • Enhanced photoluminescence intensity of Y{sub 2}O{sub 3}:Eu{sup 3+} more than 60% by Y{sub 2}O{sub 3} surface coating. - Abstract: Novel Y{sub 2}O{sub 3} coated Y{sub 2}O{sub 3}:Eu{sup 3+} nanotubes with different coating ratios were synthesized successfully by a facile two-step process, including hydrothermal synthesis of Y(OH){sub 3} coated Y(OH){sub 3}:Eu{sup 3+} as precursors and then calcination of them at 1000 °C for 2 h. X-ray diffraction patterns and field emission scanning electron microscope images indicated these Y{sub 2}O{sub 3} coated Y{sub 2}O{sub 3}:Eu{sup 3+} phosphors possess tubular nanostructures. The photoluminescence properties of Y{sub 2}O{sub 3} coated Y{sub 2}O{sub 3}:Eu{sup 3+} were systematically investigated by photoluminescence spectra, and photoluminescence enhancement was observed after proper coating. In other words, the coating ratio played a crucial role in photoluminescence efficiency. When it was 1/9, the photoluminescence intensity of {sup 5}D{sub 0} → {sup 7}F{sub 2} emission (about 613 nm) was 60% higher than that of Y{sub 2}O{sub 3}: Eu{sup 3+} phosphors under 255 nm excitation. Therefore, surface coating may be an alternative route for enhanced photoluminescence properties of the Y{sub 2}O{sub 3}:Eu{sup 3+} red-emitting phosphor.

  5. Photoluminescence and cathodoluminescence properties of Eu{sup 3+} ions activated AMoO{sub 4} (A = Mg, Ca, Sr, Ba) phosphors

    SciTech Connect

    Du, Peng; Yu, Jae Su

    2015-10-15

    Highlights: • Under 393 nm excitation, strong red emission located at 615 nm was observed in all the samples. • The Eu{sup 3+}-activated CaMoO{sub 4} phosphor exhibited the strongest PL properties. • The CIE chromaticity coordinate of Eu{sup 3+}-activated CaMoO{sub 4} phosphor was (0.647,0.352). • The color purity of Eu{sup 3+}-activated CaMoO{sub 4} phosphor was 92.8%. • Strong CL properties were observed in the Eu{sup 3+}-activated CaMoO{sub 4} phosphor. - Abstract: Eu{sup 3+}-activated AMoO{sub 4} (A = Mg, Ca, Sr, Ba) phosphors were synthesized by a solid-state reaction method. Photoluminescence and cathodoluminescence (CL) spectra as well as X-ray diffraction patterns were measured to characterize the fabricated samples. Under 393 nm excitation, strong red emissions located at ∼615 nm corresponding to the {sup 5}D{sub 0} → {sup 7}F{sub 2} transition of Eu{sup 3+} ions were observed in all the samples. Compared with other Eu{sup 3+} ions activated AMoO{sub 4} (A = Mg, Sr, Ba) phosphors, Eu{sup 3+}-activated CaMoO{sub 4} phosphor exhibited the strongest red emission intensity with better Commission Internationale de L’Eclairage chromaticity coordinate and higher color purity. Furthermore, the CL results indicated that the Eu{sup 3+}-activated CaMoO{sub 4} phosphor had excellent luminescence properties.

  6. Transport Properties of DNA Bases Placed in Graphene Nano-gap

    NASA Astrophysics Data System (ADS)

    Wolowiec, Christian; Kioussis, Nick; Novikov, Dmitri

    2009-03-01

    There has been significant demand and research activity for the development of new DNA sequencing technologies employing transverse transport techniques. We present systematic first principles studies based on Density Functional Theory of the transport properties and current-voltage characteristics of nucleotide molecules of the DNA bases, placed in 1.2 nm gap formed between the zigzag edges of graphene nano-electrodes. The linear dispersion of the graphene electrons and the local spin-polarization associated with the zigzag edges allow the exploration of both the charge- and spin-current signatures of the DNA bases to sequence DNA. We will present results in the tunneling regime of the charge- and spin-transport properties as the geometrical conformation of the bases is varied. Such signatures may be used experimentally for developing an efficient means of sequencing larger strands of DNA.

  7. Anisotropic optical properties of free and bound excitons in highly strained A-plane ZnO investigated with polarized photoreflectance and photoluminescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Nam, Yoon Sung; Lee, Sang Wook; Baek, K. S.; Chang, S. K.; Song, Jae-Ho; Song, Jung-Hoon; Han, Seok Kyu; Hong, Soon-Ku; Yao, Takafumi

    2008-05-01

    We have investigated the polarization dependence of the near-band-edge photoluminescence and photoreflectance spectra in nonpolar (A-plane) ZnO films under strong biaxial compressive strain. We show that anisotropic strain and the orientation of the nonpolar plane play an important role in determining the polarization selectivity and properties of excitonic transitions. We identified four distinct band-edge transitions at 3.449, 3.420, 3.386, and 3.326eV. They were identified as E2 and E1 free excitons, E1 excitons bound to a donor, and free-electron-to-bound-hole transition, respectively. Unlike previously reported results on relatively thick nonpolar films, the E1 exciton (lowest energy) was mainly polarized to E ⊥c and weakly polarized to E ∥c under strong biaxial compressive strain in the 100nm thick film. The E2 exciton (next higher energy) was exclusively polarized to E ∥c. The localization energy of DX is 34meV, which is much larger than that in polar ZnO, and the DX was not thermally delocalized even at room temperature.

  8. Site occupation and photoluminescence properties of Ce3+ in Sr4Ca4La2 (PO4)6O2: Experiments and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Zhou, Rongfu; Ning, Lixin; Zhou, Weijie; Lin, Litian; Shi, Rui; Liang, Hongbin

    2017-04-01

    Cerium-doped oxyapatite phosphors, Sr4Ca4La2(PO4)6O2: Ce3+, are prepared by a traditional solid-state reaction method. X-ray diffraction (XRD) refinement reveals that the hexagonal Sr4Ca4La2(PO4)6O2 structure is characterized by a random distribution of Sr and Ca atoms on the nine-coordinated cationic 4f sites and of Sr, Ca, and La atoms on the seven-coordinated cationic 6 h sites. Photoluminescence properties of Ce-doped samples are then studied with excitation energies in the vacuum-ultraviolet (VUV) to ultraviolet (UV) range at low temperature. Three main types of occupation sites for Ce3+ are identified based on analysis of emission and excitation spectra and of luminescence decay behaviors. The Ce3+ occupation on the seven-coordinated La (6 h) site is found to be dominant, which is supported by wave function-based CASSCF/CASPT2 embedded cluster calculations on Ce3+ 4f → 5d transition energies at the spin-orbit level. The role of the coordinated oxygen ion that is not bonded with P5+ in the 5d centroid shift of CeLa(6h)3+ is emphasized. The thermal stability and doping concentration dependence of the 5d luminescence are also investigated and discussed in association with the coordination structures of Ce3+.

  9. Visible and NIR photoluminescence properties of a series of novel lanthanide-organic coordination polymers based on hydroxyquinoline-carboxylate ligands.

    PubMed

    Gai, Yan-Li; Xiong, Ke-Cai; Chen, Lian; Bu, Yang; Li, Xing-Jun; Jiang, Fei-Long; Hong, Mao-Chun

    2012-12-17

    A series of novel two-dimensional (2D) lanthanide coordination polymers with 4-hydroxyquinoline-2-carboxylate (H(2)hqc) ligands, [Ln(Hhqc)(3)(H(2)O)](n)·3nH(2)O (Ln = Eu (1), Tb (2), Sm (3), Nd (4), and Gd (5)) and [Ln(Hhqc)(ox)(H(2)O)(2)](n) (Ln = Eu (6), Tb (7), Sm (8), Tm (9), Dy (10), Nd (11), Yb (12), and Gd (13); H(2)ox = oxalic acid), have been synthesized under hydrothermal conditions. Complexes 1-5 are isomorphous, which can be described as a two-dimensional (2D) hxl/Shubnikov network based on Ln(2)(CO(2))(4) paddle-wheel units, and the isomorphous complexes 6-13 feature a 2D decker layer architecture constructed by Ln-ox infinite chains cross-linked alternatively by bridging Hhqc(-) ligands. The room-temperature photoluminescence spectra of complexes Eu(III) (1 and 6), Tb(III) (2 and 7), and Sm(III) (3 and 8) exhibit strong characteristic emissions in the visible region, whereas Nd(III) (4 and 11) and Yb(III) (12) complexes display NIR luminescence upon irradiation at the ligand band. Moreover, the triplet state of H(2)hqc matches well with the emission level of Eu(III), Tb(III), and Sm(III) ions, which allows the preparation of new optical materials with enhanced luminescence properties.

  10. The effect of citric acid on morphology and photoluminescence properties of white light emitting ZnO-SiO2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Sivakami, R.; Thiyagarajan, P.

    2016-07-01

    The white light emitting ZnO-SiO2 nanocomposites were synthesized by sol-gel combustion method using zinc nitrate, citric acid and tetraethoxysilane. To analyze the effect of fuel content on the photoluminescence properties of ZnO-SiO2 nanocomposites, the citric acid content was varied as 1, 5, and 10 moles with respect to one mole of zinc. The SEM images of the nanocomposites revealed the spherical, flower and platelet like morphology with variation in citric acid content and annealing temperatures. The ZnO-SiO2 nanocomposites prepared with various Zn:CA ratio excited at UV (280 nm), near UV (365 nm), violet (405 nm) and blue (465 nm) wavelength showed blue and greenish-yellow emission. Among all ratios, the ZnO-SiO2 nanocomposites with Zn:CA - 1:1 ratio showed the intense broad band emission compared to Zn:CA - 1:5 and 1:10 values. This particular composition of sample excited under violet (405 nm) LED source shows white light, as confirmed by the CIE chromaticity coordinates (x = 0.342, y = 0.318).

  11. Investigations on photoluminescence and cathodoluminescence properties of Ca3La6(SiO4)6:Tb3 +, Mn2 +

    NASA Astrophysics Data System (ADS)

    Zhang, Jia; Zhou, Beibei; Wang, Xichen

    2016-08-01

    Tb3 +/Mn2 + activated Ca3La6(SiO4)6 (CLS) phosphors were prepared by solid-state reaction method, and their photoluminescence and cathodoluminescence (CL) properties were investigated. The CLS:Tb3 + sample shows a yellowish green emission under 377 nm excitation, and the excitation spectrum reveals the excitation peaks between 340 and 390 nm can match with the near-ultraviolet LED chip. Excellent thermal stability has been obtained in the CLS:Tb3 + phosphor by studying the temperature dependence of the Tb3 + emission intensity. By introducing Mn2 + into CLS:Tb3 +, tunable emissions are generated due to the efficient energy transfer from Tb3 + to Mn2 +. The CL spectrum of CLS:Tb3 + displays that the characteristic 5D4-7FJ (J = 6 - 3) transitions of Tb3 + are found under electron beam excitation. The above investigation results imply that the CLS:Tb3 +, Mn2 + phosphors could have potential applications on LEDs and FEDs.

  12. Structural variations and photoluminescent properties of a series of metal-organic frameworks constructed from 5-(4-carboxybenzoylamino)-isophthalic acid

    NASA Astrophysics Data System (ADS)

    Zhao, Wen; Zhang, Li-Juan; Zhao, Xiao-Li

    2013-06-01

    Five new metal-organic frameworks (MOFs) with 5-(4-carboxybenzoylamino)-isophthalic acid (H3L), namely, [Cd9L6(DMA)6]·4DMA (1), [Cd3L2(H2O)9]·4H2O (2), [LaL(H2O)4]·2H2O (3), [CeL(H2O)4]·H2O (4) and [Tb(HL)(H2L)(H2O)3]·5H2O (5) (DMA=N,N-dimethylacetamide), have been synthesized. Complex 1 shows a three-dimensional architecture generated from linkage of Cd-O chains via L3- ligands. Minor variations in synthetic conditions of 1 afforded 2, which features an interesting 2D→3D catenation architecture containing helical chains. Complexes 3 and 4 are isostructural and each feature a two-dimensional architecture constructed from the linkage of L3- with Ln3+. Complex 5 displays a chain-like structure, of which the most interesting feature is the existence of free carboxylic acid (-COOH) group which may confer unique functionality. Moreover, the investigations of the thermal stability, powder X-ray diffractions and solid-state photoluminescent properties for these crystalline materials have been carried out.

  13. The effects of charge compensation on photoluminescence properties of a new green-emitting ZnB2O4:Tb3+ phosphor.

    PubMed

    Liu, Jie; Wu, Zhan-Chao; Wang, Ping; Mei, Yong-Mei; Jiang, Man; Kuang, Shao-Ping

    2014-11-01

    Charge compensation is an effective way to eliminate charge defects and improve the luminescent intensity of phosphors. In this paper, a new green-emitting phosphor ZnB(2)O(4):Tb(3+) was prepared by solid-state reaction at 750 °C. The effects of Tb(3+) doping content and charge compensators (Li(+), Na(+) or K(+)) on photoluminescence properties of ZnB(2)O(4):Tb(3+) were investigated. X-ray powder diffraction analysis confirms the sample has cubic structure of ZnB(2)O(4). The excitation and emission spectra indicate that this phosphor can be excited by near ultraviolet light at 378 nm, and exhibits bright green emission with the highest peak at 544 nm corresponding to the (5)D4 → (7)F5 transition of Tb(3+). The critical quenching concentration of Tb(3+) in ZnB(2)O(4) host is 8 mol%. The results of charge compensation show that the emission intensity can be improved by Na(+) and K(+). Specifically, K(+) is the optimal one for ZnB(2)O(4):Tb(3+).

  14. Synthesis and Photoluminescence Properties of Sr2Be2B2O7 Doped with Dy3+, Sm3+, Tb3+, and Pb2+

    NASA Astrophysics Data System (ADS)

    Pekgözlü, İ.; Karabulut, H.; Mergen, A.; Basak, A. S.

    2016-07-01

    Pure and Dy3+-, Sm3+-, Tb3+-, and Pb2+-doped Sr2Be2B2O7 materials were prepared by a solution combustion synthesis method. The phase analysis of all synthesized materials was carried out using powder XRD. The photoluminescent properties of Dy3+-, Sm3+-, Tb3+-, and Pb2+-doped Sr2Be2B2O7 materials were investigated using a spectrofl uorometer at room temperature. The fi rst luminescent material, Sr2Be2B2O7:Dy3+, emits 478-493, 573, and 661 nm upon excitation with 344 nm; Sr2Be2B2O7:Sm3+ emits 563-574, 599-613, 647-666, and 705-713 nm upon excitation with 395 nm; Sr2Be2B2O7:Tb3+ emits 489, 545, 584-591, and 622 nm upon excitation with 248 nm; Sr2Be2B2O7:Pb2+ emits 371 nm upon excitation with 281 nm. Also, the dependence of the emission intensity on the activator ion (Dy3+, Sm3+, Tb3+, and Pb2+) concentration for the Sr2Be2B2O7 was studied. It was observed that the concentration quenching of Dy3+, Sm3+, Tb3+, and Pb2+ in Sr2Be2B2O7 is 0.05, 0.02, 0.07, and 0.02 mol.%, respectively.

  15. Optical and structural properties in type-II InAlAs/AlGaAs quantum dots observed by photoluminescence, X-ray diffraction and transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Ben Daly, A.; Craciun, D.; Laura Ursu, E.; Lemaître, A.; Maaref, M. A.; Iacomi, F.; Vasile, B. S.; Craciun, V.

    2017-10-01

    We present the effects of AlGaAs alloy composition on InAlAs quantum dots (QDs) optical and structural properties. Photoluminescence (PL) analysis of samples having a variety of aluminium composition values covering type-II transitions clearly in QDs showed the presence of two transitions X-Sh and X-Ph. High-resolution X-ray diffraction (HRXRD) investigations showed that the layers grew epitaxially on the GaAs substrate, with no relaxation regardless the Al content of AlGaAs layer. From the reciprocal space map (RSM) investigation around (004) and (115) diffraction peaks, it was shown that the InAlAs layer is fully strained, the in-plane lattice parameters (a and b, a = b) being identical to those of GaAs substrate, while the c lattice parameter was dependent on the In and Al concentrations, being larger than that of the substrate. High-resolution transmission electronic microscopy (HRTEM) investigations confirmed that films grew epitaxially on the GaAs substrate with no visible dislocations or other major defects within the InAlAs/GaAlAs QDs structure.

  16. Enhanced photoluminescence property and broad color emission of ZnGa2O4 phosphor due to the synergistic role of Eu3+ and carbon dots

    NASA Astrophysics Data System (ADS)

    Huo, Qiuyue; Tu, Weixia; Guo, Lin

    2017-10-01

    ZnGa2O4 phosphors co-composited with nanoscale carbon dots (CDs) and Eu3+ were presented for the tunable color emission. Novel single phase CDs or/and Eu3+ composited ZnGa2O4 phosphors were synthesized by microwave hydrothermal method and their optical properties were investigated. The ZnGa2O4 phosphors composited with CDs exhibited an intense broad blue light emission at 421 nm and a more enhanced photoluminescence intensity than those without CDs. The Eu3+ composited ZnGa2O4 phosphors gave an ideal red color emission. The CDs/Eu3+ co-composited ZnGa2O4 phosphors exhibited a wide emission band peak at 450 nm and narrow emission peak at 618 nm. Furthermore, the tunable color emissions of CDs/Eu3+ co-composited ZnGa2O4 phosphors from blue to the white light region, and then to red were obtained with the increasing Eu3+ concentration, which can be a promising single phased phosphor candidate in light emitting diodes. Broadly tunable emission single phased phosphor is tuned firstly through the synergistic role of the non-metal element and the rare earth metal ions.

  17. Hydrogen-surfactant-mediated epitaxy of Ge1- x Sn x layer and its effects on crystalline quality and photoluminescence property

    NASA Astrophysics Data System (ADS)

    Nakatsuka, Osamu; Fujinami, Shunsuke; Asano, Takanori; Koyama, Takeshi; Kurosawa, Masashi; Sakashita, Mitsuo; Kishida, Hideo; Zaima, Shigeaki

    2017-01-01

    The effect of hydrogen-surfactant-mediated molecular beam epitaxy (MBE) growth of Ge1- x Sn x layer on Ge(001) substrate on crystalline quality and photoluminescence (PL) property has been investigated. The effect of irradiation of atomic hydrogen (H) generated by dissociating molecular hydrogen (H2) were examined during the MBE growth. H irradiation significantly improves the surface morphology with the enhancement of the two-dimensional growth of the Ge1- x Sn x epitaxial layer. Enhanced diffuse scattering is observed in the X-ray diffraction profile, indicating a high density of point defects. In the PL spectrum of the H2-irradiated Ge1- x Sn x layer, two components are observed, suggesting the radiative recombination with both indirect and direct transitions, while one component related to the direct transition is observable in the H-irradiated sample. The postdeposition annealing in nitrogen ambient at as low as 220 °C decreases the PL intensity of the H-irradiated Ge1- x Sn x layer, although the intensity is recovered after annealing at 300 °C, suggesting the annihilation of point defects in the Ge1- x Sn x layer.

  18. One-pot synthesis and photoluminescence properties of core/porous-shell olive-like BaWO4 microstructure by a template-assisted hydrothermal method

    NASA Astrophysics Data System (ADS)

    Zhang, Suyue; Wang, Yunlong; Wang, Cuiping; Zhang, Hui; Shen, Yuhua; Xie, Anjian

    2016-02-01

    Core/porous-shell olive-like crystalline BaWO4 is synthesized by a combined simple hydrothermal method and soft template approach. The prepared product shows an olive-like shape with diameter of ˜2 μm, length of ˜4 μm, and the thickness of the shell of about 65 nm, which are orderly assembled by many nanoparticles. A possible formation mechanism of olive-like BaWO4 microstructure involving interfacial recognization of ions, nucleation, aggregation, in situ growth and Ostwald ripening process is proposed. Polyacrylic acid sodium (PAAS) as a template plays an important role in inducing the nucleation and growth of olive-like BaWO4 microcrystalline. Other shapes of BaWO4 microcrystalline are also fabricated by varying the concentration of PAAS and Ba2+. The olive-like product with a core-shell structure which exists a large number of pores on crystal surface shows excellent photoluminescence property, which have potentially applied prospects in fields such as light display systems etc.

  19. Synthesis and photoluminescence properties of Pb{sup 2+} doped inorganic borate phosphor NaSr{sub 4}(BO{sub 3}){sub 3}

    SciTech Connect

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

    2016-05-06

    A series of Inorganic borate phosphors NaSr{sub 4}(BO{sub 3}){sub 3} doped with Pb{sup 2+} 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 Pb{sup 2+} concentration for the NaSr{sub 4}(BO{sub 3}){sub 3} were studied in details. The concentration quenching of Pb{sup 2+} doped NaSr{sub 4}(BO{sub 3}){sub 3} was observed at 0.02 mol. The Stokes shifts of NaSr{sub 4}(BO{sub 3}){sub 3}: Pb{sup 2+} phosphor was calculated to be 7574 cm{sup −1}.

  20. Origin of the Photoluminescence Quantum Yields Enhanced by Alkane-Termination of Freestanding Silicon Nanocrystals: Temperature-Dependence of Optical Properties

    NASA Astrophysics Data System (ADS)

    Ghosh, Batu; Takeguchi, Masaki; Nakamura, Jin; Nemoto, Yoshihiro; Hamaoka, Takumi; Chandra, Sourov; Shirahata, Naoto

    2016-11-01

    On the basis of the systematic study on temperature dependence of photoluminescence (PL) properties along with relaxation dynamics we revise a long-accepted mechanism for enhancing absolute PL quantum yields (QYs) of freestanding silicon nanocrystals (ncSi). A hydrogen-terminated ncSi (ncSi:H) of 2.1 nm was prepared by thermal disproportination of (HSiO1.5)n, followed by hydrofluoric etching. Room-temperature PL QY of the ncSi:H increased twentyfold only by hydrosilylation of 1-octadecene (ncSi-OD). A combination of PL spectroscopic measurement from cryogenic to room temperature with structural characterization allows us to link the enhanced PL QYs with the notable difference in surface structure between the ncSi:H and the ncSi-OD. The hydride-terminated surface suffers from the presence of a large amount of nonradiative relaxation channels whereas the passivation with alkyl monolayers suppresses the creation of the nonradiative relaxation channels to yield the high PL QY.

  1. Investigations on photoluminescence and cathodoluminescence properties of Ca3La6(SiO4)6:Tb(3+), Mn(2.).

    PubMed

    Zhang, Jia; Zhou, Beibei; Wang, Xichen

    2016-08-05

    Tb(3+)/Mn(2+) activated Ca3La6(SiO4)6 (CLS) phosphors were prepared by solid-state reaction method, and their photoluminescence and cathodoluminescence (CL) properties were investigated. The CLS:Tb(3+) sample shows a yellowish green emission under 377nm excitation, and the excitation spectrum reveals the excitation peaks between 340 and 390nm can match with the near-ultraviolet LED chip. Excellent thermal stability has been obtained in the CLS:Tb(3+) phosphor by studying the temperature dependence of the Tb(3+) emission intensity. By introducing Mn(2+) into CLS:Tb(3+), tunable emissions are generated due to the efficient energy transfer from Tb(3+) to Mn(2+). The CL spectrum of CLS:Tb(3+) displays that the characteristic (5)D4-(7)FJ (J=6-3) transitions of Tb(3+) are found under electron beam excitation. The above investigation results imply that the CLS:Tb(3+), Mn(2+) phosphors could have potential applications on LEDs and FEDs. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Driving the photoluminescent and structural properties of X2-Y2SiO5 by varying the dopant Dy3+ concentration towards cool WLED applications

    NASA Astrophysics Data System (ADS)

    Ramakrishna, G.; Nagabhushana, H.; Hareesh, K.; Sunitha, D. V.

    2017-07-01

    Dy3+ doped Y2SiO5 nanophosphors were synthesized by solution combustion technique using Calotropis gigantean milk latex and NaCl as fuel and flux respectively. Powder X-ray diffraction (PXRD) confirmed the formation of monoclinic X2-phase Y2SiO5 belonging to the phase group C2/c. Fourier transform infrared spectroscopy (FTIR) shows characteristic metal-oxygen (Y-O) vibration band at 721 cm-1. Transmission electron microscopic (TEM) and Scanning electron microscopic (SEM) morphological feature exhibits non-uniform almost spherical shaped nanosized particles. The photoluminescence (PL) emission peaks, recorded at 388 nm, showed radiative emissions at 483, 575 and 636 nm respectively. Judd-Ofelt (JO) analysis was carried out to estimate the radiative (AR) properties, radiative life time (τR), branching ratio (βR) and stimulated emission crossection (σλp). The CIE and CCT was estimated using McCamy empirical formula. In the beginning, the CIE co-ordinate values were lying in the light blue region. However, with increase in Dy3+ concentration the values shifted towards white region. CCT value was found to be ∼6984 K. Therefore, Y2SiO5:Dy3+ (9 mol%) can be used for cool day light and WLED applications.

  3. Redox properties of a single (7,5)single-walled carbon nanotube determined by an in situ photoluminescence spectroelectrochemical method

    NASA Astrophysics Data System (ADS)

    Hong, Liu; Mouri, Shinichiro; Miyauchi, Yuhei; Matsuda, Kazunari; Nakashima, Naotoshi

    2014-10-01

    The determination of electronic states of single-walled carbon nanotubes (SWNTs) has been a central issue in science and nanotechnology of carbon nanotubes. We here describe the oxidation and reduction potentials of a single SWNT determined by in situ photoluminescence (PL) spectroelectrochemical measurements. By PL imaging and single SWNT PL spectroscopy, the stepwise quenching behavior of the PL from a single (7,5)SWNT was detected as the outer-applied potentials increased. Based on the analysis of the obtained potential-dependent PL plots using the Nernst equation, the oxidation and reduction potentials of the (7,5) tube are successfully determined as 0.41 V and -0.38 V vs. Ag/AgCl, respectively, which shift from those of the bulk (7,5)SWNTs. We further observed a PL blueshift and narrowing of the line width as the external-applied potential to the single SWNT increases. The present results are important for understanding the electronic properties of a single (n,m)SWNT and its applications.

  4. Origin of the Photoluminescence Quantum Yields Enhanced by Alkane-Termination of Freestanding Silicon Nanocrystals: Temperature-Dependence of Optical Properties

    PubMed Central

    Ghosh, Batu; Takeguchi, Masaki; Nakamura, Jin; Nemoto, Yoshihiro; Hamaoka, Takumi; Chandra, Sourov; Shirahata, Naoto

    2016-01-01

    On the basis of the systematic study on temperature dependence of photoluminescence (PL) properties along with relaxation dynamics we revise a long-accepted mechanism for enhancing absolute PL quantum yields (QYs) of freestanding silicon nanocrystals (ncSi). A hydrogen-terminated ncSi (ncSi:H) of 2.1 nm was prepared by thermal disproportination of (HSiO1.5)n, followed by hydrofluoric etching. Room-temperature PL QY of the ncSi:H increased twentyfold only by hydrosilylation of 1-octadecene (ncSi-OD). A combination of PL spectroscopic measurement from cryogenic to room temperature with structural characterization allows us to link the enhanced PL QYs with the notable difference in surface structure between the ncSi:H and the ncSi-OD. The hydride-terminated surface suffers from the presence of a large amount of nonradiative relaxation channels whereas the passivation with alkyl monolayers suppresses the creation of the nonradiative relaxation channels to yield the high PL QY. PMID:27830771

  5. Structure and Photoluminescent Properties of B3+-Doped (Y0.9Dy0.1)InGe2O7 Phosphor

    NASA Astrophysics Data System (ADS)

    Teoh, Lay-Gaik; Tsai, Yeou-Yih; Tsai, Mu-Tsun; Chai, Yin-Lai; Chang, Yee-Shin

    2013-01-01

    A color-tunable, near-white-light-emitting, B3+-doped (Y0.9Dy0.1)InGe2O7 phosphor was synthesized using a solid-state reaction, and its structure and luminescent properties were determined. X-ray powder diffraction patterns showed that all of the diffraction peaks can be attributed to the monoclinic YInGe2O7 crystal structure for B3+ ion concentration up to 5 mol.%, and that the optimal concentration for B3+ doping is 3 mol.%. In the photoluminescent studies, increasing the B3+ ion concentration caused the intensities of both the excitation and emission peaks to increase and then decrease. In addition, the color tone changes gradually, from the near-white-light region, through greenish, and finally to yellowish. This change is caused by a decrease in the symmetry of the local structure around the Dy3+ ion when the B3+ ion in the host reaches the optimum concentration for the H3BO3 flux of 3 mol.%. When the B3+ content is increased further, the distinct difference in ionic radius between the lattice atoms and the substituent atoms causes the lattice to become distorted and the crystallinity of the (Y0.9Dy0.1)InGe2O7 phosphor to decrease.

  6. Energy Dependence and Scaling Property of Localization Length near a Gapped Flat Band

    NASA Astrophysics Data System (ADS)

    Ge, Li; Tureci, Hakan

    Using a tight-binding model for a one-dimensional Lieb lattice, we show that the localization length near a gapped flat band behaves differently from the typical Urbach tail in a band gap: instead of reducing monotonically as the energy E moves away from the flat band energy Ef, the presence of the flat band causes a nonmonotonic energy dependence of the localization length. This energy dependence follows a scaling property when the energy is within the spread (W) of uniformly distributed diagonal disorder, i.e. the localization length is only a function of (E-Ef)/W. Several other lattices are compared to distinguish the effect of the flat band on the localization length, where we eliminate, shift, or duplicate the flat band, without changing the dispersion relations of other bands. Using the top right element of the Green's matrix, we derive an analytical relation between the density of states and the localization length, which shines light on these properties of the latter, including a summation rule for its inverse. This work is partially supported by NSF under Grant No. DMR-1506987.

  7. Crystal structure, electronic structure, and photoluminescent properties of SrMoO{sub 4}:Tb{sup 3+} phosphors

    SciTech Connect

    Park, Sung Wook; Moon, Byung Kee; Jeong, Jung Hyun; Bae, Jong Seong; Kim, Jung Hwan

    2015-10-15

    Highlights: • SrMoO{sub 4}:Tb{sup 3+} phosphor samples were synthesized at different temperatures. • The crystal and electronic structures, and luminescence properties were studied. • The excitation peak shifts to red with increasing the sintering temperature. • The luminescence mechanism of SrMoO{sub 4}:Tb{sup 3+} was suggested. - Abstract: The experimental and theoretical studies of the optical properties of SrMoO{sub 4}:Tb{sup 3+} phosphors were carried out. The structural, optical, and electronical properties of the phosphors were systematically studied. The phosphor samples were crystallized at different temperatures via a sol–gel method. Excitation spectra of SrMoO{sub 4}:Tb{sup 3+} powder samples exhibited gradual red shift and luminescent intensity changed with increasing the sintering temperature. Such spectral changes depend strongly on the crystallographic properties such as lattice parameters and crystallinity. The shift of the excitation spectra is mainly ascribed to the covalent bond interaction between Mo−O bonds. An energy band model was demonstrated to describe the luminescence mechanism in the material.

  8. The optical band gap and surface free energy of polyethylene modified by electron beam irradiations

    NASA Astrophysics Data System (ADS)

    Abdul-Kader, A. M.

    2013-04-01

    In this study, investigations have been carried out on electron beam irradiated ultra high molecular weight polyethylene (UHMWPE). Polyethylene samples were irradiated with 1.5 MeV electron beam at doses ranging from 50 to 500 kGy. Modifications in optical properties and photoluminescence behavior of the polymer were evaluated by UV-vis and photoluminescence techniques. Changes of surface layer composition of UHMWPE produced by electron irradiations were studied by Rutherford back scattering spectrometry (RBS). The change in wettability and surface free energy induced by irradiations was also investigated. The optical absorption studies reveal that both optical band gap and Urbach's energy decreases with increasing electron dose. A correlation between energy gap and the number of carbon atoms in clusters is discussed. Photoluminescence spectra were reveal remarkable decrease in the integrated luminescence intensity with increasing irradiation dose. Contact angle measurements showed that wettability and surface free energy increases with increasing the irradiation dose.

  9. Synthesis, crystal structures, photoluminescent, magnetic and chiroptical properties of two homochiral ErIII complexes with different nuclearity

    NASA Astrophysics Data System (ADS)

    Li, Xi-Li; Liu, Ying-Fan; Zhang, Xue-Li; Cheng, Conghui; Zheng, Xianjun; Zhu, Cancan; Zhou, Liming

    2017-06-01

    Employing chiral bis-bidentate N-donor ligand, (+)-2,5-bis(4,5-pinene-2-pyridyl) pyrazine (L), as a bridging ligand for Er(dbm)3H2O, and depending on the ratio control of reactants, two mono- and dinuclear homochiral ErIII complexes with the formulae Er(dbm)3L·2H2O (1) (dbm- = dibenzoylmethanate) and Er2(dbm)6L·6H2O (2) have been synthesized and structurally characterized. Circular dichroic (CD) spectra verify their chiroptical activities. Investigations on the luminescent properties of complexes 1 and 2 demonstrate that they exhibit characteristic near-infrared (NIR) luminescence of the ErIII ion at around 1533 nm and the emission intensity of the mononuclear complex 1 is much larger than that of dinuclear species 2, the reason of which is elucidated in this work. In addition, the measurements of magnetic properties indicate that the direct-current (dc) magnetic behaviors of complexes 1 and 2 mainly result from the thermal depopulation of the excited MJ sublevels of the ErIII ions. Notablely, complex 2 is the first example of chiral polynuclear lanthanide complexes with NIR-luminescence property.

  10. Spectroscopic properties of poly(9,9‐dioctylfluorene) thin films possessing varied fractions of β‐phase chain segments: enhanced photoluminescence efficiency via conformation structuring

    PubMed Central

    Perevedentsev, Aleksandr; Chander, Nathan; Kim, Ji‐Seon

    2016-01-01

    ABSTRACT Poly(9,9‐dioctylfluorene) (PFO) is a widely studied blue‐emitting conjugated polymer, the optoelectronic properties of which are strongly affected by the presence of a well‐defined chain‐extended “β‐phase” conformational isomer. In this study, optical and Raman spectroscopy are used to systematically investigate the properties of PFO thin films featuring a varied fraction of β‐phase chain segments. Results show that the photoluminescence quantum efficiency (PLQE) of PFO films is highly sensitive to both the β‐phase fraction and the method by which it was induced. Notably, a PLQE of ∼69% is measured for PFO films possessing a ∼6% β‐phase fraction induced by immersion in solvent/nonsolvent mixtures; this value is substantially higher than the average PLQE of ∼55% recorded for other β‐phase films. Furthermore, a linear relationship is observed between the intensity ratios of selected Raman peaks and the β‐phase fraction determined by commonly used absorption calibrations, suggesting that Raman spectroscopy can be used as an alternative means to quantify the β‐phase fraction. As a specific example, spatial Raman mapping is used to image a mm‐scale β‐phase stripe patterned in a glassy PFO film, with the extracted β‐phase fraction showing excellent agreement with the results of optical spectroscopy. © 2016 The Authors. Journal of Polymer Science Part B: Polymer Physics Published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1995–2006

  11. Synthesis, second-harmonic generations (SHG), and photoluminescence (PL) properties of Ca4Bi6-xLnxO13 (Ln=La and Eu) solid solutions

    NASA Astrophysics Data System (ADS)

    Jung, Hoyong; Jo, Hongil; Oh, Seung-Jin; Ok, Kang Min

    2017-08-01

    Noncentrosymmetric (NCS) Ca4Bi6-xLnxO13 (Ln=La and Eu; x=0, 0.06, and 0.12) solid solutions have been synthesized through conventional solid state reactions by using CaCO3, Bi2O3, and Ln2O3. Crystal structures of the reported materials have been determined by powder X-ray diffraction using Rietveld method. Ca4Bi6-xLnxO13 solid solutions crystallizing in the polar NCS space group, C2mm (No. 38), are composed of uni-dimensional bands with BiO3 and BiO5 polyhedra. Second-harmonic generation (SHG) measurements, using 1064 nm radiation, indicate that Ca4Bi6-xLnxO13 solid solutions are type-I phase-matchable and reveal moderate SHG efficiencies ranging from 30 to 80 times that of α-SiO2. Detailed structure-SHG property relationship analyses suggest that the net moment arising from the alignment of the asymmetric polyhedra of the lone pair cation, Bi3+ in Ca4Bi6-xLnxO13 solid solutions is critical for the observed SHG phenomena. Photoluminescence (PL) properties measurements on Ca4Bi6-xEuxO13 solid solutions reveal the characteristic narrow emission lines attributable to 5D0→7Fj (j=4, …, 0) transitions and confirm the unsymmetrical coordination environment of the doped-Eu3+ cation sites. Further PL measurements at different temperatures suggest that while Ca4Bi6-xEuxO13 exhibit the nonradiative emissions at high temperatures, the solid solutions show the radiative emissions with strong intensities at low temperatures.

  12. Gap Analysis of Material Properties Data for Ferritic/Martensitic HT-9 Steel

    SciTech Connect

    Brown, Neil R.; Serrano De Caro, Magdalena; Rodriguez, Edward A.

    2012-08-28

    The US Department of Energy (DOE), Office of Nuclear Energy (NE), is supporting the development of an ASME Code Case for adoption of 12Cr-1Mo-VW ferritic/martensitic (F/M) steel, commonly known as HT-9, primarily for use in elevated temperature design of liquid-metal fast reactors (LMFR) and components. In 2011, Los Alamos National Laboratory (LANL) nuclear engineering staff began assisting in the development of a small modular reactor (SMR) design concept, previously known as the Hyperion Module, now called the Gen4 Module. LANL staff immediately proposed HT-9 for the reactor vessel and components, as well as fuel clad and ducting, due to its superior thermal qualities. Although the ASME material Code Case, for adoption of HT-9 as an approved elevated temperature material for LMFR service, is the ultimate goal of this project, there are several key deliverables that must first be successfully accomplished. The most important key deliverable is the research, accumulation, and documentation of specific material parameters; physical, mechanical, and environmental, which becomes the basis for an ASME Code Case. Time-independent tensile and ductility data and time-dependent creep and creep-rupture behavior are some of the material properties required for a successful ASME Code case. Although this report provides a cursory review of the available data, a much more comprehensive study of open-source data would be necessary. This report serves three purposes: (a) provides a list of already existing material data information that could ultimately be made available to the ASME Code, (b) determines the HT-9 material properties data missing from available sources that would be required and (c) estimates the necessary material testing required to close the gap. Ultimately, the gap analysis demonstrates that certain material properties testing will be required to fulfill the necessary information package for an ASME Code Case.

  13. Giant photoluminescence enhancement in tungsten-diselenide-gold plasmonic hybrid structures

    NASA Astrophysics Data System (ADS)

    Wang, Zhuo; Dong, Zhaogang; Gu, Yinghong; Chang, Yung-Huang; Zhang, Lei; Li, Lain-Jong; Zhao, Weijie; Eda, Goki; Zhang, Wenjing; Grinblat, Gustavo; Maier, Stefan A.; Yang, Joel K. W.; Qiu, Cheng-Wei; Wee, Andrew T. S.

    2016-05-01

    Impressive properties arise from the atomically thin nature of transition metal dichalcogenide two-dimensional materials. However, being atomically thin limits their optical absorption or emission. Hence, enhancing their photoluminescence by plasmonic nanostructures is critical for integrating these materials in optoelectronic and photonic devices. Typical photoluminescence enhancement from transition metal dichalcogenides is 100-fold, with recent enhancement of 1,000-fold achieved by simultaneously enhancing absorption, emission and directionality of the system. By suspending WSe2 flakes onto sub-20-nm-wide trenches in gold substrate, we report a giant photoluminescence enhancement of ~20,000-fold. It is attributed to an enhanced absorption of the pump laser due to the lateral gap plasmons confined in the trenches and the enhanced Purcell factor by the plasmonic nanostructure. This work demonstrates the feasibility of giant photoluminescence enhancement in WSe2 with judiciously designed plasmonic nanostructures and paves a way towards the implementation of plasmon-enhanced transition metal dichalcogenide photodetectors, sensors and emitters.

  14. Giant photoluminescence enhancement in tungsten-diselenide-gold plasmonic hybrid structures.

    PubMed

    Wang, Zhuo; Dong, Zhaogang; Gu, Yinghong; Chang, Yung-Huang; Zhang, Lei; Li, Lain-Jong; Zhao, Weijie; Eda, Goki; Zhang, Wenjing; Grinblat, Gustavo; Maier, Stefan A; Yang, Joel K W; Qiu, Cheng-Wei; Wee, Andrew T S

    2016-05-06

    Impressive properties arise from the atomically thin nature of transition metal dichalcogenide two-dimensional materials. However, being atomically thin limits their optical absorption or emission. Hence, enhancing their photoluminescence by plasmonic nanostructures is critical for integrating these materials in optoelectronic and photonic devices. Typical photoluminescence enhancement from transition metal dichalcogenides is 100-fold, with recent enhancement of 1,000-fold achieved by simultaneously enhancing absorption, emission and directionality of the system. By suspending WSe2 flakes onto sub-20-nm-wide trenches in gold substrate, we report a giant photoluminescence enhancement of ∼20,000-fold. It is attributed to an enhanced absorption of the pump laser due to the lateral gap plasmons confined in the trenches and the enhanced Purcell factor by the plasmonic nanostructure. This work demonstrates the feasibility of giant photoluminescence enhancement in WSe2 with judiciously designed plasmonic nanostructures and paves a way towards the implementation of plasmon-enhanced transition metal dichalcogenide photodetectors, sensors and emitters.

  15. Giant photoluminescence enhancement in tungsten-diselenide–gold plasmonic hybrid structures

    PubMed Central

    Wang, Zhuo; Dong, Zhaogang; Gu, Yinghong; Chang, Yung-Huang; Zhang, Lei; Li, Lain-Jong; Zhao, Weijie; Eda, Goki; Zhang, Wenjing; Grinblat, Gustavo; Maier, Stefan A.; Yang, Joel K. W.; Qiu, Cheng-Wei; Wee, Andrew T. S.

    2016-01-01

    Impressive properties arise from the atomically thin nature of transition metal dichalcogenide two-dimensional materials. However, being atomically thin limits their optical absorption or emission. Hence, enhancing their photoluminescence by plasmonic nanostructures is critical for integrating these materials in optoelectronic and photonic devices. Typical photoluminescence enhancement from transition metal dichalcogenides is 100-fold, with recent enhancement of 1,000-fold achieved by simultaneously enhancing absorption, emission and directionality of the system. By suspending WSe2 flakes onto sub-20-nm-wide trenches in gold substrate, we report a giant photoluminescence enhancement of ∼20,000-fold. It is attributed to an enhanced absorption of the pump laser due to the lateral gap plasmons confined in the trenches and the enhanced Purcell factor by the plasmonic nanostructure. This work demonstrates the feasibility of giant photoluminescence enhancement in WSe2 with judiciously designed plasmonic nanostructures and paves a way towards the implementation of plasmon-enhanced transition metal dichalcogenide photodetectors, sensors and emitters. PMID:27150276

  16. Influence of acidic pH on the formulation of TiO2 nanocrystalline powders with enhanced photoluminescence property.

    PubMed

    Tsega, Moges; Dejene, F B

    2017-02-01

    Titanium dioxide (TiO2) nanoparticles were prepared by the sol-gel method at different pH values (3.2-6.8) with a hydrochloric acid (HCl) solution. Raw samples were calcined at 500 °C for 2 h. The effects of pH on the structural, morphological and optical properties of TiO2 nanoparticles were investigated. At pH 4.4-6.8, only the anatase phase of TiO2 was observed. Under strong acidic condition at pH 3.2 rutile, brookite and anatase co-exist, but rutile is the predominant phase. The strain value increased and the crystallite size decreased as the HCl content increased. The increased crystallite sizes in the range 21-24 nm and enhanced blue emission intensity around 432 nm was obtained for the sample at pH 5.0. Experimental results showed that TiO2 nanoparticles synthesized at pH 5.0 exhibited the best luminescence property with pure anatase phase.

  17. Transition metal coordination polymers based on tetrabromoterephthalic and bis(imidazole) ligands: Syntheses, structures, topological analysis and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaowei; Xing, Peiqi; Geng, Xiujuan; Sun, Daofeng; Xiao, Zhenyu; Wang, Lei

    2015-09-01

    Eight new coordination polymers (CPs), namely, [Zn(1,2-mbix)(tbtpa)]n (1), [Co(1,2-mbix)(tbtpa)]n (2), [CdCl(1,2-mbix)(tbtpa)0.5]n (3), {[Cd(1,2-bix)(tbtpa)]·H2O}n (4), {[Cd0.5(1,2-bix)(tbtpa)0.5]·H2O}n (5), {[Co0.5(1,2-bix)(tbtpa)0.5]·2H2O}n (6), {[Co(1,2-bix)(tbtpa)]·H2O}n (7) and {[Co(1,2-bix)(tbtpa)]·Diox·2H2O}n (8), were synthesized under solvothermal conditions based on mix-ligand strategy (H2tbtpa=tetrabromoterephthalic acid and 1,2-mbix=1,2-bis((2-methyl-1H-imidazol-1-yl)methyl)benzene, 1,2-bix=1,2-bis(imidazol-1-ylmethyl)benzene). All of the CPs have been structurally characterized by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analyses (TGA). X-ray diffraction analyses show that 1 and 2 are isotypics which have 2D highly undulated networks with (4,4)-sql topology with the existence of C-H ⋯Br interactions; for 3, it has a 2D planar network with (4,4)-sql topology with the occurrence of C-H ⋯Cl interactions other than C-H ⋯Br interactions; 4 shows a 3D 2-fold interpenetrated nets with rare 65·8-mok topology which has a self-catention property. As the same case as 1 and 2, 5 and 6 are also isostructural with planar layers with 44-sql topology which further assembled into 3D supramolecular structure through the interdigitated stacking fashion and the C-Br ⋯Cph interactions. As for 7, it has a 2D slightly undulated networks with (4,4)-sql topology which has one dimension channel. While 8 has a 2-fold interpenetrated networks with (3,4)-connect jeb topology with point symbol {63}{65·8}. And their structures can be tuned by conformations of bis(imidazol) ligands and solvent mixture. Besides, the TGA properties for all compounds and the luminescent properties for 1, 3, 4, 5 are discussed in detail.

  18. Accurate prediction of band gaps and optical properties of HfO2

    NASA Astrophysics Data System (ADS)

    Ondračka, Pavel; Holec, David; Nečas, David; Zajíčková, Lenka

    2016-10-01

    We report on optical properties of various polymorphs of hafnia predicted within the framework of density functional theory. The full potential linearised augmented plane wave method was employed together with the Tran-Blaha modified Becke-Johnson potential (TB-mBJ) for exchange and local density approximation for correlation. Unit cells of monoclinic, cubic and tetragonal crystalline, and a simulated annealing-based model of amorphous hafnia were fully relaxed with respect to internal positions and lattice parameters. Electronic structures and band gaps for monoclinic, cubic, tetragonal and amorphous hafnia were calculated using three different TB-mBJ parametrisations and the results were critically compared with the available experimental and theoretical reports. Conceptual differences between a straightforward comparison of experimental measurements to a calculated band gap on the one hand and to a whole electronic structure (density of electronic states) on the other hand, were pointed out, suggesting the latter should be used whenever possible. Finally, dielectric functions were calculated at two levels, using the random phase approximation without local field effects and with a more accurate Bethe-Salpether equation (BSE) to account for excitonic effects. We conclude that a satisfactory agreement with experimental data for HfO2 was obtained only in the latter case.

  19. Ferromagnetic Mn-Implanted GaP: Microstructures vs Magnetic Properties.

    PubMed

    Yuan, Ye; Hübner, René; Liu, Fang; Sawicki, Maciej; Gordan, Ovidiu; Salvan, G; Zahn, D R T; Banerjee, D; Baehtz, Carsten; Helm, Manfred; Zhou, Shengqiang

    2016-02-17

    Ferromagnetic GaMnP layers were prepared by ion implantation and pulsed laser annealing (PLA). We present a systematic investigation on the evolution of microstructure and magnetic properties depending on the pulsed laser annealing energy. The sample microstructure was analyzed by high-resolution X-ray diffraction (HR-XRD), transmission electron microscopy (TEM), Rutherford backscattering spectrometry (RBS), ultraviolet Raman spectroscopy (UV-RS), and extended X-ray absorption fine structure (EXAFS) spectroscopy. The presence of X-ray Pendellösung fringes around GaP (004) and RBS channeling prove the epitaxial structure of the GaMnP layer annealed at the optimized laser energy density (0.40 J/cm(2)). However, a forbidden TO vibrational mode of GaP appears and increases with annealing energy, suggesting the formation of defective domains inside the layer. These domains mainly appear in the sample surface region and extend to almost the whole layer with increasing annealing energy. The reduction of the Curie temperature (TC) and of the uniaxial magnetic anisotropy gradually happens when more defects and the domains appear as increasing the annealing energy density. This fact univocally points to the decisive role of the PLA parameters on the resulting magnetic characteristics in the processed layers, which eventually determine the magnetic (or spintronics) figure of merit.

  20. Pentamodal property and acoustic band gaps of pentamode metamaterials with different cross-section shapes

    NASA Astrophysics Data System (ADS)

    Huang, Yan; Lu, Xuegang; Liang, Gongying; Xu, Zhuo

    2016-03-01

    Pentamodal property and acoustic band gaps of pentamode metamaterials with different cross-section shapes, including regular triangle, square, pentagon, hexagon and circle, have been comparatively studied by finite-element method. Results show that for the varying diameters of circumcircles in thick and thin ends of unit (D and d), the ratio of bulk modulus to shear modulus (B / G) and bandgaps of these five structures perform similar changing tendency. With the increasing d, B / G decreases and the single-mode bandgap moves toward high-frequency direction with the decreasing normalized bandwidth (Δω /ωg). With the increasing D, B / G keeps around the respective average value, and the single-mode bandgap firstly moves to high-frequency then to low-frequency direction with the firstly increasing and then decreasing Δω /ωg. Complete bandgap appears as D reaching to critical value for each given d, then moves to high-frequency direction. For same parameters the triangle case has highest B / G and acoustic band gaps with lower frequency and broader bandwidth.

  1. Effect of cell gap on electro-optical properties of polymer dispersed liquid crystal lens for smart electronic glasses

    NASA Astrophysics Data System (ADS)

    Kim, Jaeyong; Han, Jeong In

    2014-07-01

    Polymer dispersed liquid crystal (PDLC) lenses with a cell gap of 11 μm and 30 μm were made from a uniformly dispersed mixture of 40% prepolymer (NOA 65, Norland optical adhesive 65) and 60% E7 liquid crystal. PDLC's mixture between two ITO coated glasses was polymerized by UV (ultraviolet) curing in the polymerization induced phase separation (PIPS) process. Decline of cell gap is a physical approach to improve the electrooptical properties, while cooling or doping of SiO2 nanoparticles is the microstructural approach to enhance the properties, because the electric field applied to the liquid crystal molecules in LC droplets is inversely proportional to the cell gap. A smaller cell gap significantly and effectively increases the electric field applied to PDLCD devices. The driving voltages and slope for the sample with a cell gap of 11 μm and 30 μm were drastically improved. The driving voltage and the slope of the linear region of PDLC lens with narrow cell gap of 11 μm were drastically enhanced compared to those of the samples with 30 μm cell gap and the cooled and doped samples. These improvements were due to the increase of the applied electric field. However, the response time and contrast ratio were deteriorated. It seems that this deterioration was caused by the sticking or fixing of liquid crystal molecules in LC (liquid crystal) droplets by the intensive electric field applied to the PDLC device.

  2. Structural, electronic and photoluminescence properties of Eu3+-doped CaYAlO4 obtained by using citric acid complexes as precursors

    NASA Astrophysics Data System (ADS)

    Perrella, R. V.; Júnior, C. S. Nascimento; Góes, M. S.; Pecoraro, E.; Schiavon, M. A.; Paiva-Santos, C. O.; Lima, H.; Couto dos Santos, M. A.; Ribeiro, S. J. L.; Ferrari, J. L.

    2016-07-01

    The search for new materials that meet the current technological demands for photonic applications, make the Rare Earth ions embedded in inorganic oxides as excellent candidates for several technological devices. This work presents the synthesis of Eu3+-doped CaYAlO4 using citric acid as ligand to form a complex precursor. The methodology used has big draw due to its easy handling and low cost of the materials. The thermal analysis of viscous solutions was evaluated and the obtained compounds show the formation of a polycrystalline tetragonal phase. Rietveld refinement was used to understand the structural and the cell parameters of the crystalline phase as a function of temperature of heat-treatment. Crystallite size and microstrain were determined and were shown to have a direct relationship with the temperature of the heat-treatment. The band-gap of the CaYAlO4 doped with 1 and 10 mol% of Eu3+ showed values close to 4.30 eV, resulting in their transparency in the visible region between 330 and 750 nm. Besides the intense photoluminescence from Eu3+, a study was conducted to evaluate the possible position of the Eu3+ in the CaYAlO4 as host lattice. Lifetime of the emission decay from Eu3+ excited state 5D0 show that CaYAlO4 is a good host to rare earth ions, once it can avoid clustering of these ions in concentration as high as 10 mol%. The predictions of the sublevels of the 7F1 crystal field level are discussed through the method of equivalent nearest neighbours (MENN). The intensity parameters (Ωλ, λ = 2 and 4) are reproduced with physically reasonable values of average polarizabilities. The set of charge factors used in both calculations are in good agreement with the charge of the europium ion described by the Batista-Longo improved model (BLIM). The quantum efficiencies of the materials were calculated based on Judd-Ofelt theory. Based on the results obtained in this work, the materials have potential use in photonic devices such as lasers and solid

  3. Low Band Gap Thiophene-Perylene Diimide Systems with Tunable Charge Transport Properties

    SciTech Connect

    Balaji, Ganapathy; Kale, Tejaswini S.; Keerthi, Ashok; Della Pelle, Andrea M.; Thayumanavan, S.; Vallyaveettil, Surech

    2010-11-30

    Perylenediimide-pentathiophene systems with varied architecture of thiophene units were synthesized. The photophysical, electrochemical, and charge transport behavior of the synthesized compounds were studied. Both molecules showed a low band gap of ~1.4 eV. Surprisingly, the molecule with pentathiophene attached via β-position to the PDI unit upon annealing showed a predominant hole mobility of 1 × 10-4 cm2 V-1 s-1 whereas the compound with branched pentathiophene attached via β-position showed an electron mobility of 9.8 × 10-7 cm2 V-1 s-1. This suggests that charge transport properties can be tuned by simply varying the architecture of pentathiophene units.

  4. Self-assembled multilayers and photoluminescence properties of a new water-soluble poly(para-phenylene)

    SciTech Connect

    Shi, X.; Li, D.; Luett, M.; Fitzsimmons, M.R.; Van Patten, G.P.

    1998-07-01

    This paper reports the synthesis and characterizations of a new water-soluble poly(paraphenylene) (PPP) and its applications in preparing self-assembled multi-layer films. This new water-soluble conducting polymer was prepared through the sulfonation reaction of poly(p-quarterphenylene-2,2{prime}-dicarboxylic acid). The incorporation of sulfonate groups has dramatically improved PPP's solubility in water at a wide pH range, whereas previous PPP is only slightly soluble in basic solutions. Dilute aqueous solutions of this polymer with acidic, neutral or basic pH emit brilliant blue light while irradiated with UV light. The sulfonated PPP emits from 350 nm to 455 nm with a maximum intensity at 380 nm. Self-assembled multilayers of this sulfonated PPP were constructed with a positively charged polymer poly(diallyl dimethyl ammonium chloride) and characterized with various surface analyses. Conductive (RuO{sub 2} and ITO), semiconductive (Si wafer), and non-conductive (SiO{sub 2}) substrates were used in the preparation of self-assembled multilayers. Electrical, optical and structural properties of these novel self-assembled thin films will be discussed.

  5. Self-assembled multilayers and photoluminescence properties of a new water-soluble poly(para-phenylene)

    SciTech Connect

    Shi, X.; Li, D.Q.; Luett, M.; Fitzsimmons, M.R.; Van Patten, G.P.

    1998-03-01

    This paper reports the synthesis and characterizations of a new water-soluble poly(para-phenylene) (PPP) and its applications in preparing self-assembled multilayer films. This new water-soluble conducting polymer was prepared through the sulfonation reaction of poly(p-quarterphenylene-2,2{prime}-dicarboxylic acid). The incorporation of sulfonate groups has dramatically improved PPP`s solubility in water at a wide pH range, whereas previous PPP is only slightly soluble in basic solutions. Dilute aqueous solutions of this polymer with acidic, neutral or basic pH emit brilliant blue light while irradiated with UV light. The sulfonated PPP emits from 350 nm to 455 nm with a maximum intensity at 380 nm. Self-assembled multilayers of this sulfonated PPP were constructed with a positively charged polymer poly(diallyl dimethyl ammonium chloride) and characterized with various surface analyses. Conductive (RuO{sub 2} and ITO), semiconductive (Si wafer), and non-conductive (SiO{sub 2}) substrates were used in the preparation of self-assembled multilayers. Electrical, optical and structural properties of these novel self-assembled thin films will be discussed.

  6. Photoluminescence properties of Bi3+-doped YInGe2O7 phosphors under an ultraviolet irradiation

    NASA Astrophysics Data System (ADS)

    Tsai, Yeou-Yih; Chen, Hao-Long; Chai, Yin-Lai; Chang, Yee-Shin

    2013-01-01

    Yttrium indium germanate (YInGe2O7) doped with different concentrations of Bi3+ ion was synthesized using a vibrating milled solid-sate reaction. The compound was characterized and its optical properties were investigated. The precursor powders were heated at 1300 °C for 10 h to obtain good crystallinity with better luminescence. The XRD results show that all peaks can be attributed to the monoclinic YInGe2O7 phase when the Bi3+ ion concentration is increased up to 5 mol%. Furthermore, the 0.5 mol% of Bi3+ ion doping lead to obvious improvements in the surface morphology of the YInGe2O7 powder, because the Bi2O3 also acts as a flux reagent. In the PL studies, excitation under an ultraviolet (302 nm) irradiation shows that the (Y1-xBix)InGe2O7 phosphors display luminescence belonging to the 3P1 → 1S0 transition from 457 to 496 nm, and the CIE color coordinates changed from a blue to blueish region as the Bi3+ ion concentration increased from 0.2 mol% to 5 mol%. The time-resolved of the 3P1 → 1S0 transition presents a non-single exponential decay behavior, and the decay time decreases from 8 ms to 1 ms.

  7. Judd-Ofelt analysis and photoluminescence properties of RE3+ (RE = Er & Nd): Cadmium lithium boro tellurite glasses

    NASA Astrophysics Data System (ADS)

    Raju, K. Vemasevana; Raju, C. Nageswara; Sailaja, S.; Reddy, B. Sudhakar

    2013-01-01

    Rare earth (Er3+ and Nd3+) ions doped cadmium lithium boro tellurite (CLiBT) glasses were prepared by melt quenching method. The vis-NIR absorption spectra of these glasses have been analyzed systematically. Judd-Ofelt intensity parameters Ωλ (λ = 2, 4, 6) have been evaluated and used to compute the radiative properties of emission transitions of Er3+ and Nd3+: CLiBT glasses. From the NIR emission spectra of Er3+: CLiBT glasses a broad emission band centered at 1538 nm (4I13/2 → 4I15/2) is observed and from Nd3+: CLiBT glasses, three NIR emission bands at 898 nm (4F3/2 → 4I9/2), 1070 nm (4F3/2 → 4I11/2) and 1338 nm (4F3/2 → 4I13/2) are observed with an excitation wavelength λexci = 514.5 nm (Ar+ Laser). The FWHM and stimulated emission cross-section values are calculated for Er3+ and Nd3+: CLiBT glasses. FWHM × σeP values are also calculated for Er3+: CLiBT glasses.

  8. Three complexes of Cu(I) cluster with flexible and rigid ligands: Synthesis, characterization and photoluminescent properties

    NASA Astrophysics Data System (ADS)

    Sun, Shu; Liu, Li-Juan; Ma, Wang-Yang; Zhou, Wei-Xia; Li, Jun; Zhang, Feng-Xing

    2015-05-01

    Three new Cu(I) cluster complexes, viz. [(Cu4I4)(Cu2I2)(dimb)3]n (1; dimb=1,4-diimidazol-1-ylbutane), [(Cu3I2)(dimb)(dmtz)]n (2; dmtz=3,5-dimethyl-1,2,4-triazole), and [Cu6(mbt)6] (3; mbt=2-mercaptobenzothiazole), have been solvothermally synthesized and structurally characterized. In 1, a Cu4I4 cubane core as a 4-connecting node, connects the neighboring nodes either through single dimb or μ2-[(Cu2I2)(dimb)2] linkers, affording an undulated 2D (4,4) net. Parallel interpenetration occurs between the adjacent nets and thus the overall 2D→3D network is formed. Complex 2 is constructed by 2D (4,4) topological plane grid layers of AB stacking. The core, a distorted triangular bipyramidal Cu3I2 cluster, is acted as a 4-connecting node and connected with dimb and μ3-dmtz to form the layer. Complex 3 contains a (Cu6S6) core in discrete paddle-wheel molecule, which serves as a 4-connecting node to link equivalent ones via π···π interaction, forming 2D (4,4) layers. Solid-state luminescence properties and thermogravimetric analyses of 1, 2 and 3 were investigated.

  9. Synthesis, photoluminescence and thermoluminescence properties of LiNa3P2O7:Tb3+ green emitting phosphor

    NASA Astrophysics Data System (ADS)

    Munirathnam, K.; Dillip, G. R.; Ramesh, B.; Joo, S. W.; Prasad Raju, B. Deva

    2015-11-01

    The alkaline phosphate based LiNa3P2O7:Tb3+ phosphors are prepared by solid state reaction method. X-ray diffraction (XRD) analysis shows that all the powders possess orthorhombic structure. Fourier transform infrared (FTIR) spectroscopy studies suggest that the phosphor belong to the diphosphate family. The morphology of the phosphors is identified by scanning electron microscopy (SEM). Upon 378 nm excitation, the LiNa3P2O7:Tb3+ phosphors shown emission bands at 482, 545, 588 and 620 nm corresponding to the transitions 5D4→7F6, 5D4→7F5, 5D4→7F4 and 5D4→7F3, respectively. The optimized concentration of Tb3+ in LiNa3P2O7 phosphor is found to be 9 mol%. The concentration quenching mechanism was proved to be the exchange interaction between two nearest Tb3+ ions with the critical distance (Rc) of 1.18 nm. The Commission International de l'Eclairage (CIE) coordinates evidence that the phosphors emit in the green light region. Thermoluminescence properties of the prepared phosphors are studied by pre-irradiating the powders with different doses of UV irradiation. The kinetic parameters of TL glow curves are calculated using Chen's peak shape method.

  10. Photoluminescence properties of BaMoO4:RE3+ (RE = Eu, Sm, Dy, Tb, Tm) phosphors

    NASA Astrophysics Data System (ADS)

    Cho, Shinho

    2016-11-01

    Rare-earth (RE)-activated barium molybdate phosphors for multicolor display applications were synthesized with different activator ions via a solid-state reaction. The effects of the activator ions on the structural, morphological, and optical properties of barium molybdate phosphors were investigated. The XRD spectra of all the phosphors, regardless of the activator ion, exhibited that the main peak of the phosphors occurred at the (112) plane, indicating the tetragonal BaMoO4 structure. The crystalline particles exhibited a tendency to agglomerate with irregular shapes and sizes. The emission spectra of RE-ion-doped BaMoO4 phosphors under ultraviolet excitation consisted of multicolor emissions: blue for Tm3+ activator ions, green for Tb3+ activator ions, yellow for Dy3+ activator ions, reddish orange for Eu3+ activator ions, and red for Sm3+ activator ions. These results suggest that multicolor emission can be realized by incorporating appropriate activator ions into the BaMoO4 host lattice.

  11. Synthesis and photoluminescent properties of geometrically hindered cis-tris(diphenylaminofluorene) as precursors to light-emitting devices.

    PubMed

    Kang, Nam-Goo; Kokubo, Ken; Jeon, Seaho; Wang, Min; Lee, Chang-Lyoul; Canteenwala, Taizoon; Tan, Loon-Seng; Chiang, Long Y

    2015-03-13

    A novel highly luminescent tris-fluorenyl ring-interconnected chromophore tris(DPAF-C9) was synthesized using a C3 symmetrical triaminobenzene core as the synthon. This structure bears three light-harvesting 2-diphenylamino-9,9-dialkylfluorenyl (DPAF) ring moieties with each attached by two branched 3',5',5'-trimethylhexyl (C9) arms. A major stereoisomer was chromatographically isolated and characterized to possess a 3D structural configuration of cis-conformer in a cup-form. Molecular calculation at B3LYP/6-31G* level revealed the unexpected stability of this cis-cup-conformer of tris(DPAF-C9) better than that of the stereoisomer in a propeller-form and the trans-conformer. The structural geometry is proposed to be capable of minimizing the aggregation related self-quenching effect in the condensed phase. Fluorescence emission wavelength of tris(DPAF-C9) was found to be in a close range to that of PVK that led to its potential uses as the secondary blue hole-transporting material for enhancing the device property toward the modulation of PLED performance.

  12. Branch-shaped NaGdF{sub 4}:Eu{sup 3+} nanocrystals: Selective synthesis, and photoluminescence properties

    SciTech Connect

    Wang Shangbing; Li Qing; Pei Lizhai; Zhang Qianfeng

    2010-08-15

    The branch-shaped NaGdF{sub 4}:Eu{sup 3+} nanocrystals (NCs) were synthesized by using polyvinylpyrrolidone (PVP) as a capping agent in ethylene glycol (EG) solution. The NCs were readily dispersed into water or ethanol to form a relatively stable suspension, which may facilitate their applications in biological fields. Meanwhile, the crystal structures of the NCs were tunable from the mixture of the {alpha}-(cubic) and {beta}-(hexagonal) phases to the pure {beta}-phase by varying the F{sup -}/Ln{sup 3+} molar ratio or the reaction temperature. The pure {beta}-phase NCs were obtained at relatively high F{sup -}/Ln{sup 3+} molar ratio and reaction temperature. In addition, the Eu{sup 3+}-doping concentration-dependent optical properties of the NaGdF{sub 4}:Eu{sup 3+} NCs were investigated in detail. The result shows that the emissions from high energy level transitions (e.g., {sup 5}D{sub 1}, {sup 5}D{sub 2}, and {sup 5}D{sub 3}) are significantly impaired with increasing the Eu{sup 3+}-doping concentration due to the cross-relaxation process, and the emission at 612 nm is predominant since the doped Eu{sup 3+} ions locate in the crystal fields without inversion center.

  13. Synthesis, characterization, photoluminescent properties and antimicrobial activities of two novel polymeric silver(I) complexes with diclofenac

    NASA Astrophysics Data System (ADS)

    Hamamci Alisir, Sevim; Sariboga, Bahtiyar; Caglar, Sema; Buyukgungor, Orhan

    2017-02-01

    Two novel silver(I) complexes with diclofenac, ({2-(2,6-dicholoroanilino)phenylacetic acid} = dicl) namely [Ag(dicl)]n (1) and [Ag(dicl)(bipy)]n (2) (bipy: 4,4'-bipyridine), have been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis and single-crystal X-ray diffraction. X-ray crystallographic data of 1 revealed that dicl anion adopts a μ3-η1,η2 coordinated mode link three Ag atoms generate 1D infinite chain structure. In 2, dicl ligand plays crucial role to form double-ladder chain structure, clamping two neighboring [Ag(μ-bipy)]∞ chains by using carboxylate oxygen atoms (O1, O2). The most interesting structural feature of 2 is the presence of strong π···π interactions between aromatic phenyl rings of dicl placed in the adjacent 1D chains, leads to forming 2D slab structure. The coordination modes of dicl in the title complexes are supported by using IR spectroscopy. Thermal stabilities of 1 and 2 have been determined by TG/DTA/DTG techniques. The luminescent properties of complex 1 and 2 have been investigated in the solid state at room temperature. Furthermore, the title complexes have been tested for their in vitro antibacterial activities and are determined to be highly effective for antibacterial activity against Gram(+) and Gram(-) pathogenic bacteria cells. 1 and 2 showed activity on Fungi, as well.

  14. Cd(II)-coordination polymers based on tetracarboxylic acid and diverse bis(imidazole) ligands: Synthesis, structural diversity and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Arıcı, Mürsel; Yeşilel, Okan Zafer; Taş, Murat

    2017-01-01

    Three new Cd(II)-coordination polymers, namely, {[Cd2(μ6-ao2btc)(μ-1,5-bipe)2]·2H2O}n (1), {[Cd2(μ6-ao2btc)(μ-1,4-bix)2]n·2DMF} (2) and {[Cd2(μ8-abtc)(μ-1,4-betix)]·DMF·H2O}n (3) (ao2btc=di-oxygenated form of 3,3‧,5,5‧-azobenzenetetracarboxylate, 1,5-bipe: 1,5-bis(imidazol-1yl)pentane, 1,4-bix=1,4-bis(imidazol-1ylmethyl)benzene, 1,4-betix=1,4-bis(2-ethylimidazol-1ylmethyl)benzene) were synthesized with 3,3‧,5,5‧-azobenzenetetracarboxylic acid and flexible, semi-flexible and semi-flexible substituted bis(imidazole) linkers. They were characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, powder X-ray diffractions (PXRD) and thermal analyses (TG/DTA). Complexes 1-3 exhibited structural diversities depending on flexible, semi-flexible and semi-flexible substituted bis(imidazole) ligands. Complex 1 was 2D structure with 3,6L18 topology. Complex 2 had a 3D pillar-layered framework with the rare sqc27 topology. When semi-flexible substituted bis(imidazole) linker was used, 3D framework of complex 3 was obtained with the paddlewheel Cd2(CO2)4-type binuclear SBU. Moreover, thermal and photoluminescence properties of the complexes were determined in detailed.

  15. Microwave sol-gel synthesis and upconversion photoluminescence properties of CaGd2(WO4)4:Er3+/Yb3+ phosphors with incommensurately modulated structure

    NASA Astrophysics Data System (ADS)

    Lim, Chang Sung; Aleksandrovsky, Aleksandr; Molokeev, Maxim; Oreshonkov, Aleksandr; Atuchin, Victor

    2015-08-01

    CaGd2-x(WO4)4:Er3+/Yb3+ phosphors with the doping concentrations of Er3+ and Yb3+ (x=Er3++Yb3+, Er3+=0.05, 0.1, 0.2 and Yb3+=0.2, 0.45) have been successfully synthesized by the microwave sol-gel method. The crystal structure of CaGd2-x(WO4)4:Er3+/Yb3+ tungstates have been refined, and upconversion photoluminescence properties have been investigated. The synthesized particles, being formed after the heat-treatment at 900 °C for 16 h, showed a well crystallized morphology. Under the excitation at 980 nm, CaGd2(WO4)4:Er3+/Yb3+ particles exhibited a strong 525-nm and a weak 550-nm emission bands in the green region and a very weak 655-nm emission band in the red region. The Raman spectrum of undoped CaGd2(WO4)4 revealed about 12 narrow lines. The strongest band observed at 903 cm-1 was assigned to the ν1 symmetric stretching vibration of WO4 tetrahedrons. The spectra of the samples doped with Er and Yb obtained under the 514.5 nm excitation were dominated by Er3+ luminescence preventing the recording of these samples Raman spectra. Concentration quenching of the erbium luminescence at 2H11/2→4I15/2 transition is weak in the range of erbium doping level xEr=0.05-0.2, while, for transition 4S3/2→4I15/2, the signs of concentration quenching become pronounced at xEr=0.2.

  16. Coherent effect of Er 3+-Yb 3+ co-doping on enhanced photoluminescence properties of Al 2O 3 powders by the sol-gel method

    NASA Astrophysics Data System (ADS)

    Wang, X. J.; Lei, M. K.; Yang, T.; Cao, B. S.

    2004-08-01

    The Er 3+-Yb 3+ co-doped Al 2O 3 powders have been prepared by the sol-gel method, using the aluminium isopropoxide [Al(OC 3H 7) 3]-derived Al 2O 3 sols with the addition of erbium nitrate [Er(NO 3) 3 · 5H 2O] and ytterbium nitrate [Yb(NO 3) 3 · 5H 2O]. The phase structure, including only two crystalline types of Al 2O 3 phases, γ and θ, was obtained for the 0-1 mol% Er 3+ and 0-2 mol% Yb 3+ co-doped Al 2O 3 powders at the different sintering temperature of 800-1000 °C. The evidence for indirect pumping of Er 3+ through transfer of energy from Yb 3+ was found in the Al 2O 3 matrix material. For the 0.5 mol% Er 3+ and 0.5 mol% Yb 3+, the 1.0 mol% Er 3+ and 1.0 mol% Yb 3+ co-doped Al 2O 3 powders, the photoluminescence (PL) peak intensity at 1.533 μm in the spectra increased by a factor of about 2, and the corresponding full widths at half maximum (FWHM) was increased to about 59 nm, compared with that of the 0.5 and 1 mol% Er 3+-doped Al 2O 3 powders, respectively. At the same Er 3+-Yb 3+ co-doping concentration, the PL intensity increased with increasing the sintering temperature from 800 to 1000 °C. Coherent effect of Er 3+-Yb 3+ co-doping on enhanced PL properties of Al 2O 3 powders was observed. A proper molar ratio of 1:1 for Yb 3+ and Er 3+ led to the maximum PL intensity at the same sintering temperature.

  17. Preparation, structure and photoluminescence properties of Eu{sup 2+} and Ce{sup 3+}-doped SrYSi{sub 4}N{sub 7}

    SciTech Connect

    Li, Y.Q. . E-mail: y.q.li@tue.nl; Fang, C.M.; With, G. de; Hintzen, H.T. . E-mail: h.t.hintzen@tue.nl

    2004-12-01

    Undoped and Eu{sup 2+} or Ce{sup 3+}-doped SrYSi{sub 4}N{sub 7} were synthesized by solid-state reaction method at 1400-1660{sup o}C under nitrogen/hydrogen atmosphere. The crystal structure was refined from the X-ray powder diffraction data by the Rietveld method. SrYSi{sub 4}N{sub 7} and EuYSi{sub 4}N{sub 7}, being isotypic with the family of compounds MYbSi{sub 4}N{sub 7} (M=Sr, Eu, Ba) and BaYSi{sub 4}N{sub 7,} crystallize with the hexagonal symmetry: space group P6{sub 3}mc (No. 186), Z=2, a=6.0160 (1)A, c=9.7894 (1)A, V=306.83(3)A{sup 3}; and a=6.0123 (1)A, c=9.7869 (1)A, V=306.37(1)A{sup 3}, respectively. Photoluminescence properties have been studied for Sr{sub 1-x}Eu{sub x}YSi{sub 4}N{sub 7} (x=0-1) and SrY{sub 1-x}Ce{sub x}Si{sub 4}N{sub 7} (x=0-0.03) at room temperature. Eu{sup 2+}-doped SrYSi{sub 4}N{sub 7} shows a broad yellow emission band peaking around 548-570nm, while Ce{sup 3+}-doped SrYSi{sub 4}N{sub 7} exhibits a blue emission band with a maximum at about 450nm. SrYSi{sub 4}N{sub 7}:Eu{sup 2+} can be very well excited by 390nm radiation, which makes this material attractive as conversion phosphor for LED lighting applications.

  18. Rare earth (Eu{sup 3+}, Tb{sup 3+}) mesoporous hybrids with calix[4]arene derivative covalently linking MCM-41: Physical characterization and photoluminescence property

    SciTech Connect

    Li Yajuan; Yan Bing; Wang Li

    2011-09-15

    MCM-41 mesoporous silica has been functionalized with two kinds of macrocylic calixarene derivatives Calix[4] and Calix[4]Br (Calix[4]=P-tert-butylcalix[4]arene, Calix[4]Br=5.11,17.23-tetra-tert-butyl-25.27-bihydroxy- 26.28-bibromopropoxycalix[4]arene) through condensation approach of tetraethoxysilane (TEOS) in the presence of the cetyltrimethylammonium bromide (CTAB) surfactant as a template. Novel organic-inorganic mesoporous luminescent hybrid containing RE{sup 3+} (Eu{sup 3+}, Tb{sup 3+}) complexes covalently attached to the functionalized ordered mesoporous MCM-41, which are designated as RE-Calix[4]-MCM-41 and RE-Calix[4]Br-MCM-41, respectively, are obtained by sol-gel process. It is found that they all have high surface area, uniform in the mesostructure and good crystallinity. Measurement of the photoluminescence properties show the mesoporous material covalently bonded Tb{sup 3+} complexes (Tb-Calix[4]-MCM-41 and Tb-Calix[4]Br-MCM-41) exhibit the stronger characteristic emission of Tb{sup 3+} and longer lifetime than the corresponding Eu-containing materials Eu-Calix[4]-MCM-41 and Eu-Calix[4]Br-MCM-41 due to the triplet state energy of modified organic ligands Calix[4]-Si and Calix[4]Br-Si match with the emissive energy level of Tb{sup 3+} very well. - Graphical abstract: MCM-41 mesoporous silica is functionalized with two kinds of macrocylic calixarene derivatives and luminescent organic-inorganic mesoporous hybrids containing Ln{sup 3+} complexes covalently attached to the functionalized ordered mesoporous MCM-41. Highlights: > Novel linkages of functionalized calixarene derivative. > New rare earth mesoporous hybrids. > Luminescence in visible region.

  19. Synthesis and photoluminescence properties of silver(I) complexes based on N-benzoyl-L-glutamic acid and N-donor ligands with different flexibility

    NASA Astrophysics Data System (ADS)

    Yan, Ming-Jie; Feng, Qi; Song, Hui-Hua

    2016-05-01

    By changing the N-donor ancillary ligand, three novel silver (I) complexes {[Ag(HbzgluO) (4,4‧-bipy)]·H2O}n (1), {[Ag2(HbzgluO)2 (bpe)2]·2H2O}n (2) and {[Ag(HbzgluO)(bpp)]·2H2O}n (3) (H2bzgluO = N-benzoyl-L-glutamic acid, 4,4‧-bipy = 4,4ˊ-bipyridine, bpe = 1,2-di(4-pyridyl)ethane, bpp = 1,3-di(4-pyridyl)propane) were synthesized. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric analyses (TGA). In this study, the N-donor ligands are changed from rigidity (4,4‧-bipy), quasi-flexibility (bpe) to flexibility (bpp), the structures of complexes also change. Complex 1 features a 1D chain structure which is further linked together to construct a 2D supramolecular structure through hydrogen bonds. Complex 2 is a 1D double-chains configuration which eventually forms a 3D supramolecular network via hydrogen bonding interactions. Whereas, complex 3 exhibits a 2D pleated grid structure which is linked by hydrogen bonding interactions into a 3D supramolecular network. The present observations demonstrate that the modulation of coordination polymers with different structures can accomplish by changing the spacer length of N-donor ligands. In addition, the solid-state circular dichroism (CD) spectra indicated that compound 2 exhibited negative cotton effect which originated from the chiral ligands H2bzgluO and the solid-state fluorescence spectra of the three complexes demonstrated the auxiliary ligands have influence on the photoluminescence properties of the complexes.

  20. Heteronuclear, mixed-metal Ag(I)-Mn(II) coordination polymers with bridging N-pyridinylisonicotinohydrazide ligands: synthesis, crystal structures, magnetic and photoluminescence properties.

    PubMed

    Bikas, Rahman; Hosseini-Monfared, Hassan; Vasylyeva, Vera; Sanchiz, Joaquín; Alonso, Javier; Barandiaran, Jose Manuel; Janiak, Christoph

    2014-08-21

    Mixed-metal dicyanoargentate-bridged coordination polymers of Ag(i)-Mn(ii) have been prepared and their structure and magnetic properties were determined. Reaction of manganese(ii) chloride and potassium dicyanoargentate(i) with (X)(pyridin-2-ylmethylene)isonicotinohydrazide ligands (HL(1) X = Ph, HL(2) X = Me, HL(3) X = H) produced the coordination polymer 2D-[Mn(μ-L(1))(Cl)(μ-NCAgCN)Mn0.5(CH3OH)]n (), 1D-{[Mn(L(2))(Cl)(μ-NCAgCN)Mn0.5(CH3OH)]CH3OH}n () and [Mn(L(3))(Cl)(μ-NCAgCN)Mn0.5(CH3OH)]n () in good yields. Trinuclear {Mn(μ-L(1))Mn(μ-L(1))Mn} and [Ag(CN)2](-) building units form a two-dimensional slab in and 1D strands in . Variable temperature magnetic susceptibility measurements showed that despite the long distance among the high spin Mn(ii) ions [10.4676(12) Å and 10.522(1) Å, for and , respectively], weak antiferromagnetic coupling takes place through the long NC-Ag-CN bridge. The best fit parameters to the model led to the magnetic coupling constant of J = -0.1 and J = -0.47 cm(-1) for and , respectively. The photoluminescence behaviour of compounds and was studied. The spectrum of compound shows a broad emission centered at about 450 nm and two excitation maxima at 270 and 310 nm.

  1. Synthesis and Photoluminescent Properties of Nanorod Bundle Ln4O(OH)9NO3:Eu(Ln = Y, Lu) Prepared by Hydrothermal Method.

    PubMed

    Li, Ling; Noh, Hyeon Mi; Liu, Xiaoguang; Moon, Byung Kee; Choi, Byung Chun; Jeong, Jung Hyun

    2015-07-01

    Well-crystallized nanorod bundles Ln4O(OH)9NO3:1%Eu(Ln = Y, Lu) have been successfully prepared by hydrothermal method. The crystalline phase, size and optical properties were characterized using powder X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), infrared (IR) spectrograph and photoluminescent (PL) spectra. Site occupations of Eu3+ in crystals Ln4O(OH)9NO3:Eu(Ln = Y, Lu) were discussed based on excitation spectra and the empirical relationship formula between the charge transfer (CT) energy and the environmental factor. The emission spectra exhibited that the strongest emission peaks with an excitation wavelength of 395 nm were at 617 and 626 nm in crystal Lu4O(OH)9NO3:1%Eu and Y4O(OH)9NO3:1%Eu, respectively, both of which come from 5D0-7F2 transition of the Eu3+ ions. The broad excitation peaks at about 254 and 255 nm were found when monitored at 617 and 628 nm in crystal Lu4O(OH)9NO3:1%Eu and Y4O(OH)9NO3:1%Eu, respectively, which were due to O-Eu CT transition. Based on the dielectric theory of complex crystal, the CT bands at about 254 and 255 nm in Ln4O(OH)9NO3:1%Eu(Ln = Y, Lu) were assigned to the transition of O-Eu at Ln3(Ln = Y, Lu) site, from which we can conclude that Eu3+ ions occupied the site of Ln3(Ln = Y, Lu) in crystal Ln4O(OH)9NO3:1%Eu(Ln = Y, Lu). It put forward a new route to investigate site occupation of luminescent center ions in rare earth doped complex inorganic luminescence materials.

  2. Crystal structure, thermally stability and photoluminescence properties of novel Sr{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+} phosphors

    SciTech Connect

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

    2015-03-15

    A series of novel luminescent phosphors Sr{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+} 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 Sr{sub 9.97}(PO{sub 4}){sub 6}O:0.03Eu{sup 2+} phosphor exhibits strong thermal quenching resistance, retaining the luminance of 88.73% at 150 °C. The quenching concentration of Eu{sup 2+} in Sr{sub 10}(PO{sub 4}){sub 6}O was about 0.03 attributing to the dipole–quadrupole interaction. The Sr{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+} phosphor exhibited a broad-band blue emission at 439 nm upon excitation at 346 nm. The results indicate that Sr{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+} phosphors have potential applications as near UV-convertible phosphors for white-light UV LEDs. - Graphical abstract: Sr{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+} phosphors have potential applications as near UV-convertible phosphors for white-light UV LEDs. - Highlights: • Sr{sub 9.97}(PO{sub 4}){sub 6}O:0.03Eu{sup 2+} phosphor exhibits strong thermal quenching resistance. • Two different Eu{sup 2+} emission centers exists in Sr{sub 10}(PO{sub 4}){sub 6}O. • The activation energy was also estimated for the Eu{sup 2+} luminescence center.

  3. Synthesis, photoluminescence and biological properties of terbium(III) complexes with hydroxyketone and nitrogen containing heterocyclic ligands

    NASA Astrophysics Data System (ADS)

    Poonam; Kumar, Rajesh; Boora, Priti; Khatkar, Anurag; Khatkar, S. P.; Taxak, V. B.

    2016-01-01

    The ternary terbium(III) complexes [Tb(HDAP)3ṡbiq], [Tb(HDAP)3ṡdmph] and [Tb(HDAP)3ṡbathophen] were prepared by using methoxy substituted hydroxyketone ligand HDAP (2-hydroxy-4,6-dimethoxyacetophenone) and an ancillary ligand 2,2-biquinoline or 5,6-dimethyl-1,10-phenanthroline or bathophenanthroline respectively. The ligand and synthesized complexes were characterised based on elemental analysis, FT-IR and 1H NMR. Thermal behaviour of the synthesized complexes illustrates the general decomposition patterns of the complexes by thermogravimetric analysis. Photophysical properties such as excitation spectra, emission spectra and luminescence decay curves of the complexes were investigated in detail. The main green emitting peak at 548 nm can be attributed to 5D4 → 7F5 of Tb3+ ion. Thus, these complexes might be used to make a bright green light-emitting diode for display purpose. In addition the in vitro antibacterial activities of HDAP and its Tb(III) complexes against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and antifungal activities against Candida albicans and Aspergillus niger are reported. The Tb3+ complexes were found to be more potent antimicrobial agent as compared to the ligand. Among all these complexes, [Tb(HDAP)3ṡbathophen] exhibited excellent antimicrobial activity which proves its potential usefulness as an antimicrobial agent. Furthermore, in vitro antioxidant activity tests were carried out by using DPPH method which indicates that the complexes have considerable antioxidant activity when compared with the standard ascorbic acid.

  4. Synthesis, photoluminescence and biological properties of terbium(III) complexes with hydroxyketone and nitrogen containing heterocyclic ligands.

    PubMed

    Poonam; Kumar, Rajesh; Boora, Priti; Khatkar, Anurag; Khatkar, S P; Taxak, V B

    2016-01-05

    The ternary terbium(III) complexes [Tb(HDAP)3⋅biq], [Tb(HDAP)3⋅dmph] and [Tb(HDAP)3⋅bathophen] were prepared by using methoxy substituted hydroxyketone ligand HDAP (2-hydroxy-4,6-dimethoxyacetophenone) and an ancillary ligand 2,2-biquinoline or 5,6-dimethyl-1,10-phenanthroline or bathophenanthroline respectively. The ligand and synthesized complexes were characterised based on elemental analysis, FT-IR and (1)H NMR. Thermal behaviour of the synthesized complexes illustrates the general decomposition patterns of the complexes by thermogravimetric analysis. Photophysical properties such as excitation spectra, emission spectra and luminescence decay curves of the complexes were investigated in detail. The main green emitting peak at 548nm can be attributed to (5)D4→(7)F5 of Tb(3+) ion. Thus, these complexes might be used to make a bright green light-emitting diode for display purpose. In addition the in vitro antibacterial activities of HDAP and its Tb(III) complexes against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and antifungal activities against Candida albicans and Aspergillus niger are reported. The Tb(3+) complexes were found to be more potent antimicrobial agent as compared to the ligand. Among all these complexes, [Tb(HDAP)3⋅bathophen] exhibited excellent antimicrobial activity which proves its potential usefulness as an antimicrobial agent. Furthermore, in vitro antioxidant activity tests were carried out by using DPPH method which indicates that the complexes have considerable antioxidant activity when compared with the standard ascorbic acid. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Electrically tuned photoluminescence in large pitch cholesteric liquid crystal

    NASA Astrophysics Data System (ADS)

    Middha, Manju; Kumar, Rishi; Raina, K. K.

    2014-04-01

    Cholesteric liquid crystals are known as 1-D photonic band gap materials due to their periodic helical supramolecular structure and larger birefringence. Depending upon the helical twisted pitch length, they give the characteristic contrast due to selective Bragg reflections when viewed through the polarizing optical microscope and hence affect the electro-optic properties. So the optimization of chiral dopant concentration in nematic liquid crystal leads to control the transmission of polarized light through the microscope. Hence transmission based polarizing optical microscope is used for the characterization of helical pitch length in the optical texture. The unwinding of helical pitch was observed with the application of electric field which affects the intensity of photoluminescence.

  6. Electrically tuned photoluminescence in large pitch cholesteric liquid crystal

    SciTech Connect

    Middha, Manju Kumar, Rishi Raina, K. K.

    2014-04-24

    Cholesteric liquid crystals are known as 1-D photonic band gap materials due to their periodic helical supramolecular structure and larger birefringence. Depending upon the helical twisted pitch length, they give the characteristic contrast due to selective Bragg reflections when viewed through the polarizing optical microscope and hence affect the electro-optic properties. So the optimization of chiral dopant concentration in nematic liquid crystal leads to control the transmission of polarized light through the microscope. Hence transmission based polarizing optical microscope is used for the characterization of helical pitch length in the optical texture. The unwinding of helical pitch was observed with the application of electric field which affects the intensity of photoluminescence.

  7. A series of transition metal-organic frameworks based on a bipyridinium carboxylate ligand: Syntheses, structures and photoluminescent properties

    NASA Astrophysics Data System (ADS)

    Pei, Ru-Bo; Cao, Ming-Yang; Li, Lin-Ke; Dong, Xi-Yan; Zang, Shuang-Quan

    2017-09-01

    Based on a bipyridinium carboxylate ligand 1-(3,5-dicarboxy)-benzyl-1,2-di(pyridine-4-yl)ethylene chloride (H2L+Cl-), eight transition metal coordination polymers, namely, {[Zn(L)Cl]ṡ4H2O}n (1), {[Zn(L)H2O]ṡNO3ṡ2H2O}n (2), {[Zn(L) (H2O)]ṡ(NO3)0.5ṡ(Cl)0.5ṡ2H2O}n (3), {[Cd(L)(H2O)(NO3)]ṡ2H2O}n (4), {[Cd1.5(L) (Cl)2]ṡ2H2O}n (5), {[Cu(L)(H2O)]ṡNO3ṡH2O}n (6), {[Cu(HL)2(H2O)2]·Cl2·6H2O}n (7) and {[Ni(L)(H2O)Cl]ṡ4H2O}n (8) have been synthesized and characterized by single-crystal X-ray diffraction analyses. Complexes 1 and 8 display 2D wave-like layer structures with a 3-connected 63 topology. Complexes 2 and 6 demonstrate 3D 2-fold interpenetrating frameworks with uninodal, 3-connected (10,3)-d utp-topology. Another pair of 3D 2-fold interpenetrating frameworks 3 and 4 possess 3-connected, uninodal 103ThSi2 (ths)-topology. Complex 5 shows a 2D layer structure based on the extending of trinuclear Cd(II) subunits. Complex 7 presents 1D double-chain structure, in which the central Cu(II) ions are connected by the partially deprotonated ligand HL. Additionally, powder X-ray diffractions (PXRD) and thermogravimetric analyses of complexes 1-8, as well as the solid-state luminescent properties of d10 metal complexes 1-4 at room temperature have also been discussed.

  8. Three complexes of Cu(I) cluster with flexible and rigid ligands: Synthesis, characterization and photoluminescent properties

    SciTech Connect

    Sun, Shu; Liu, Li-Juan; Ma, Wang-Yang; Zhou, Wei-Xia; Li, Jun; Zhang, Feng-Xing

    2015-05-15

    Three new Cu(I) cluster complexes, viz. [(Cu{sub 4}I{sub 4})(Cu{sub 2}I{sub 2})(dimb){sub 3}]{sub n} (1; dimb=1,4-diimidazol-1-ylbutane), [(Cu{sub 3}I{sub 2})(dimb)(dmtz)]{sub n} (2; dmtz=3,5-dimethyl-1,2,4-triazole), and [Cu{sub 6}(mbt){sub 6}] (3; mbt=2-mercaptobenzothiazole), have been solvothermally synthesized and structurally characterized. In 1, a Cu{sub 4}I{sub 4} cubane core as a 4-connecting node, connects the neighboring nodes either through single dimb or μ{sub 2}-[(Cu{sub 2}I{sub 2})(dimb){sub 2}] linkers, affording an undulated 2D (4,4) net. Parallel interpenetration occurs between the adjacent nets and thus the overall 2D→3D network is formed. Complex 2 is constructed by 2D (4,4) topological plane grid layers of AB stacking. The core, a distorted triangular bipyramidal Cu{sub 3}I{sub 2} cluster, is acted as a 4-connecting node and connected with dimb and μ{sub 3}-dmtz to form the layer. Complex 3 contains a (Cu{sub 6}S{sub 6}) core in discrete paddle-wheel molecule, which serves as a 4-connecting node to link equivalent ones via π···π interaction, forming 2D (4,4) layers. Solid-state luminescence properties and thermogravimetric analyses of 1, 2 and 3 were investigated. - Graphical abstract: Complexes based on Cu(I) clusters possess two-fold 2D→3D parallel interpenetrating (1), triple emissions (2) and near-infrared emission (3). - Highlights: • Complex 1 represents two-fold 2D→3D parallel interpenetrating framework. • Complex 2 shows triple emissions. • Complex 3 displays a quite intense near-infrared (NIR) emission. • These complexes have good thermal stability.

  9. Photoluminescence of Conjugated Star Polymers

    NASA Astrophysics Data System (ADS)

    Ferguson, J. B.; Prigodin, N. V.; Epstein, A. J.; Wang, F.

    2000-10-01

    Higher dimensionality "star" polymers provide new properties beyond those found in their linear analogs. They have been used to improving electronic properties for nonlinear optics through exciton transfer and molecular antenna structures for example (M. Kawa, J. M. J. Frechet, Chem. Mater. 10, 286 (1998).). We report on photoluminescence properties of star polymers with a hyperbranched core (both hyperbranched phenlyene and hyperbranched triphenylamine) and polyhexylthiophene arms. The arm is a conjugated oligomer of polythiophene that has been investigated extensively for metallic like conductivity when doped as well as utilized in field effect transistors in its undoped form (A. Tsumara, H. Koezuka, T. Ando, Appl. Phys. Lett. 49, 1210 (1986).). The cores are respectively, a nonconjugated polymer in the case of hyperbranched phenlyene and a conjugated polymer in the case of hyperbranched triphenylamine. The photoluminesce spectrum (λ_max at 575 nm) is identical for both star polymers with the two electronically different hyperbranched cores and for linear polythiophene alone. We conclude the wave functions of the core and arms do not strongly interact to form states different from their individual states and excitons formed on the hyperbranched cores migrate to the lower bandgap polythiophene before recombining.

  10. Electronic properties of graphene nano-flakes: Energy gap, permanent dipole, termination effect, and Raman spectroscopy

    SciTech Connect

    Singh, Sandeep Kumar Peeters, F. M.; Neek-Amal, M.

    2014-02-21

    The electronic properties of graphene nano-flakes (GNFs) with different edge passivation are investigated by using density functional theory. Passivation with F and H atoms is considered: C{sub N{sub c}} X{sub N{sub x}} (X = F or H). We studied GNFs with 10 < N{sub c} < 56 and limit ourselves to the lowest energy configurations. We found that: (i) the energy difference Δ between the highest occupied molecular orbital and the lowest unoccupied molecular orbital decreases with N{sub c}, (ii) topological defects (pentagon and heptagon) break the symmetry of the GNFs and enhance the electric polarization, (iii) the mutual interaction of bilayer GNFs can be understood by dipole-dipole interaction which were found sensitive to the relative orientation of the GNFs, (iv) the permanent dipoles depend on the edge terminated atom, while the energy gap is independent of it, and (v) the presence of heptagon and pentagon defects in the GNFs results in the largest difference between the energy of the spin-up and spin-down electrons which is larger for the H-passivated GNFs as compared to F-passivated GNFs. Our study shows clearly the effect of geometry, size, termination, and bilayer on the electronic properties of small GNFs. This study reveals important features of graphene nano-flakes which can be detected using Raman spectroscopy.

  11. Investigation of energy band gap and optical properties of cubic CdS epilayers

    NASA Astrophysics Data System (ADS)

    Kim, D. J.; Yu, Y.-M.; Lee, J. W.; Choi, Y. D.

    2008-09-01

    High quality cubic CdS epilayers were grown on GaAs (1 0 0) substrates by the hot-wall epitaxy method. The crystal structure of the grown epilayers was confirmed to be the cubic structure by X-ray diffraction patterns. The optical properties of the epilayers were investigated in a wide photon energy range between 2.0 and 8.5 eV using spectroscopic ellipsometry (SE) and were studied in the transmittance spectra at a wavelength range of 400-700 nm at room temperature. The data obtained by SE were analyzed to find the critical points of the pseudodielectric function spectra, < ɛ( E)> = < ɛ1( E)> + i< ɛ2( E)>, such as E0, E1, E2, E0, and E1 structures. In addition, the optical properties related to the pseudodielectric function of CdS, such as the absorption coefficient α( E), were investigated. All the critical point structures were observed, for the first time, at 300 K by ellipsometric measurements for the cubic CdS epilayers. Also, the energy band gap was determined by the transmittance spectra of the free-standing film, and the results were compared with the E0 structure obtained by SE measurement.

  12. Effect of ZnO on the physical properties and optical band gap of soda lime silicate glass.

    PubMed

    Zaid, Mohd Hafiz Mohd; Matori, Khamirul Amin; Aziz, Sidek Hj Abdul; Zakaria, Azmi; Ghazali, Mohd Sabri Mohd

    2012-01-01

    This manuscript reports on the physical properties and optical band gap of five samples of soda lime silicate (SLS) glass combined with zinc oxide (ZnO) that were prepared by a melting and quenching process. To understand the role of ZnO in this glass structure, the density, molar volume and optical band gaps were investigated. The density and absorption spectra in the Ultra-Violet-Visible (UV-Visible) region were recorded at room temperature. The results show that the densities of the glass samples increased as the ZnO weight percentage increased. The molar volume of the glasses shows the same trend as the density: the molar volume increased as the ZnO content increased. The optical band gaps were calculated from the absorption edge, and it was found that the optical band gap decreased from 3.20 to 2.32 eV as the ZnO concentration increased.

  13. Photoluminescence properties of a new orange–red emitting Sm{sup 3+}-doped Y{sub 2}Mo{sub 4}O{sub 15} phosphor

    SciTech Connect

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

    2015-08-15

    A series of novel Y{sub 2}Mo{sub 4}O{sub 15}:xSm{sup 3+} ( (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 Y{sub 2}Mo{sub 4}O{sub 15}:Sm{sup 3+} phosphors consisted of some sharp emission peaks of Sm{sup 3+} ions centered at 565 nm, 605 nm, 650 nm, and 712 nm. The strongest one is located at 605 nm due to {sup 4}G{sub 5/2}–{sup 6}H{sub 7/2} transition of Sm{sup 3+}, generating bright orange–red light. The optimum dopant concentration of Sm{sup 3+} ions in Y{sub 2}Mo{sub 4}O{sub 15}:xSm{sup 3+} is around 5 mol% and the critical transfer distance of Sm{sup 3+} is calculated as 23.32 Å. The CIE chromaticity coordinates of the Y{sub 2}Mo{sub 4}O{sub 15}:0.05Sm{sup 3+} phosphors were located in the orange reddish region. The Y{sub 2}Mo{sub 4}O{sub 15}:Sm{sup 3+} phosphors may be potentially used as red phosphors for white light-emitting diodes. - Graphical abstract: The excitation spectrum of Y{sub 2}Mo{sub 4}O{sub 15}:Sm{sup 3+} is composed of a broad band and some sharp f–f transitions. Under 407 nm excitation, the phosphor presents some sharp emission peaks of Sm{sup 3+} ions. - Highlights: • An orange–red emitting Y{sub 2}Mo{sub 4}O{sub 15}:Sm{sup 3+} phosphor has been firstly synthesized. • Their structures, luminescent properties have also been investigated. • The optical absorption edge for the molybdate lies around 325 nm. • The CIE chromaticity coordinates were located in the orange reddish region.

  14. Photonic band gaps structure properties of two-dimensional function photonic crystals

    NASA Astrophysics Data System (ADS)

    Ma, Ji; Wang, Zhi-Guo; Liu, Xiao-Jing; Zhang, Si-Qi; Liang, Yu; Wu, Xiang-Yao

    2017-05-01

    The tunable two-dimensional photonic crystals band gap, absolute photonic band gap and semi-Dirac point are beneficial to designing the novel optical devices. In this paper, tunable photonic band gaps structure was realized by a new type two-dimensional function photonic crystals, which dielectric constants of medium columns are functions of space coordinates. However for the two-dimensional conventional photonic crystals the dielectric constant does not change with space coordinates. As the parameter adjustment, we found that the photonic band gaps structures are dielectric constant function coefficient, medium columns radius, dielectric constant function form period number and pump light intensity dependent, namely, the photonic band gaps position and width can be tuned. we also obtained absolute photonic band gaps and semi-Dirac point in the photonic band gaps structures of two-dimensional function photonic crystals. These results provide an important theoretical foundation for design novel optical devices.

  15. Photoluminescence and compositional-structural properties of ion-beam sputter deposited Er-doped TiO2-xNx films: Their potential as a temperature sensor

    NASA Astrophysics Data System (ADS)

    Scoca, D.; Morales, M.; Merlo, R.; Alvarez, F.; Zanatta, A. R.

    2015-05-01

    Er-doped TiO2-xNx films were grown by Ar+ ion-beam sputtering a Ti + Er target under different N2 + O2 high-purity atmospheres. The compositional-structural properties of the samples were investigated after thermal annealing the films up to 1000 °C under a flow of oxygen. Sample characterization included x-ray photoelectron spectroscopy, grazing incidence x-ray diffraction, Raman scattering, and photoluminescence experiments. According to the experimental data, both composition and atomic structure of the samples were very sensitive to the growth conditions and annealing temperature. In the as-deposited form, the N-rich TiO2-xNx films presented TiN crystallites and no photoluminescence. As the thermal treatments proceed, the films were transformed into TiO2 and Er3+-related light emission were observed in the visible and near-infrared ranges at room-temperature. Whereas the development of TiO2 occurred due to the insertion-diffusion of oxygen in the films, light emission originated because of optical bandgap widening and/or structural-chemical variations in the vicinity of the Er3+ ions. Finally, the photoluminescence results in the visible range suggested the potential of the present samples in producing an optically based temperature sensor in the ˜150-500 K range.

  16. Evidence for adduct formation at the semiconductor-solution interface. Photoluminescent properties of cadmium selenide in the presence of lanthanide. beta. -diketonate complexes

    SciTech Connect

    Murphy, C.J.; Ellis, A.B. )

    1990-04-05

    Photoluminescence (PL) measurements of etched, single-crystal n-CdSe demonstrate that the semiconductor surface engages in adduct formation with a family of lanthanide {beta}-diketonate complexes, Ln(fod){sub 3} (Ln = lanthanide; fod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato anion), in isooctane ambient.

  17. Photoluminescent conductor polymer holograms

    NASA Astrophysics Data System (ADS)

    Ruiz-Limón, B.; Olivares-Pérez, A.; Ponce-Lee, E. L.; Hernández-Garay, M. P.; Páez-Trujillo, G.; Fuentes-Tapia, I.

    2007-02-01

    An organic conductor polymer was doped with benzalkonium chloride to get a photoluminescent effect at 560 nm and it was used as holographic material. We used a digital image to generate a hologram in a computer and it was transferred by microlithography techniques to our polymer to get a phase hologram. The transference is successful by rubbing, the heat increment produce temperature gradients and the information in the mask is transferred to the material by the refraction index changes, thus the film is recorded. We recorded some gratings to observe the behavior of photoluminescent light with different frequencies when it is radiated with a green laser beam at 532 nm.

  18. New 1-D and 3-D thiocyanatocadmates modified by various amine molecules and Cl(-)/CH3COO(-) ions: synthesis, structural characterization, thermal behavior and photoluminescence properties.

    PubMed

    Guo, Bing; Zhang, Xiao; Wang, Yan-Ning; Huang, Jing-Jing; Yu, Jie-Hui; Xu, Ji-Qing

    2015-03-21

    Under ambient conditions, reactions of CdCl2/Cd(CH3COO)2, SCN(-) and various organic amine molecules in strongly acidic solutions afforded the five new thiocyanatocadmates [H2(abpy)][CdCl2(SCN)2] (abpy = azobispyridine) 1, [H(apy)][Cd(SCN)3] (apy = 4-aminopyridine) 2, [H(ba)]2[CdCl2(SCN)2] (ba = tert-butylamine) 3, [H2(tmen)][Cd3Cl6(SCN)2] (tmen = N,N,N',N'-tetramethylethylenediamine) 4, and [H(dba)]2[Cd2(CH3COO)2(SCN)4] (dba = dibutylamine) 5. In compound 2 only, the CH3COO(-) ions in Cd(CH3COO)2 were completely displaced by SCN(-), producing a chained thiocyanatocadmate [Cd(SCN)3](-). In the other four compounds, the Cl(-) or CH3COO(-) ions appeared in the final inorganic anion frameworks. In compound 1, the Cl(-) ions doubly bridge the Cd(2+) centers, forming a one-dimensional (1-D) infinite chain, and the SCN(-) group exists in a terminal form, whereas in compound 3, the reverse situation is observed. Due to a trans-mode arrangement for two terminal Cl(-) or SCN(-) ions around each Cd(2+) center, the inorganic anion chains in compounds 1 and 3 both show a linear shape. In compound 4, Cd(2+) and Cl(-) first aggregate to form a 1-D endless chain with a composition of Cd3Cl6, which can be described as a linear arrangement of the open double cubanes. SCN(-) serves as the second connector, propagating the Cd3Cl6 chain into a three-dimensional (3-D) network with the occluded H2(tmen)(2+) cations. In compound 5, the SCN(-) groups doubly bridge the Cd(2+) centers, forming a 1-D zigzag-shape chain. The formation of the zigzag chain likely derives from chelation of the CH3COO(-) group to the Cd(2+) center. The thermal behavior and the photoluminescence properties of the title compounds were also investigated.

  19. Phase structure and photoluminescence properties of Er 3+-doped Al 2O 3 powders prepared by the sol-gel method

    NASA Astrophysics Data System (ADS)

    Wang, X. J.; Lei, M. K.; Yang, T.; Wang, H.

    2004-08-01

    The Er 3+-doped Al 2O 3 powders have been prepared by the sol-gel method, using the aluminium isopropoxide [Al(OC 3H 7) 3]-derived Al 2O 3 sols with addition of the erbium nitrate [Er(NO 3) 3 · 5H 2O]. The different phase structure, including three crystalline types of (Al,Er) 2O 3 phases, γ, θ, α, and two Er-Al-O phases, ErAlO 3 and Al 10Er 6O 24, was obtained with the 0-5 mol% Er 3+-doped Al 2O 3 powders at the different sintering temperature of 600-1200 °C. The phase structure has an evident influence on the photoluminescence (PL) properties for the Er 3+-doped Al 2O 3 powders. For the phase mixture of γ-(Al,Er) 2O 3 and θ-(Al,Er) 2O 3 in minor amounts with the different Er 3+ doping concentration sintered at 900 °C, the PL spectra of the full widths at half maximum (FWHM) of about 55 nm were observed with a main peak at λ=1.533 μm and a side peak at λ=1.549 μm. The stronger PL intensity was detected with the 0.5 and 1 mol% Er 3+ doping concentration, and decreased with further increasing the Er 3+ doping concentration. The dramatic concentration quenching effect took place above the 1.5 mol% Er 3+ doping concentration. At the 1 mol% Er 3+ doping concentration, the PL intensity of the Er 3+-doped Al 2O 3 powders increased with the phase structure changed from γ-(Al,Er) 2O 3 → θ-(Al,Er) 2O 3 → α-(Al,Er) 2O 3, corresponding to the increase of sintering temperature from 600 to 1200 °C. The PL spectrum was observed with the main sharp peak at λ=1.533 μm and many sharp side peaks at the different wavelengths for the α-(Al,Er) 2 O 3, ErAlO 3 and Al 10Er 6O 24 phases prepared at 1200 °C.

  20. Topological evolution and photoluminescent properties of a series of divalent zinc-based metal–organic frameworks tuned via ancillary ligating spacers

    SciTech Connect

    Lian, Xiao-Min; Zhao, Wen; Zhao, Xiao-Li

    2013-04-15

    The combination of divalent zinc ions, 4-(4-carboxybenzamido)benzoic acid and exo-bidendate bipyridine ligands gave rise to a series of new MOFs: [ZnL(bipy)]·DMF·H{sub 2}O (1), [ZnL(bpe)]·1.5H{sub 2}O (2), [ZnL(bpa)]·4H{sub 2}O (3) and [ZnL(bpp)]·1.75H{sub 2}O (4) (MOF=metal-organic framework, bipy=4,4′-bipyridine, bpe=trans-1,2-bis(4-pyridyl)ethylene, bpa=1,2-bis(4-pyridinyl)ethane, bpp=1,3-bis(4-pyridinyl)propane, H{sub 2}L=4,4′-(carbonylimino)dibenzoic acid). Fine tune over the topology of the MOFs was achieved via systematically varying the geometric length of the second ligating bipyridine ligands. Single-crystal X-ray analysis reveals that complex 1 has a triply interpenetrated three-dimensional (3D) framework with elongated primitive cubic topology, whereas isostructural complexes 2 and 3 each possesses a 6-fold interpenetrated diamondiod 3D framework. Further expansion of the length of the bipyridine ligand to bpp leads to the formation of 4, which features an interesting entangled architecture of 2D→3D parallel polycatenation. In addition, the thermogravimetric analyses and solid-state photoluminescent properties of the selected complexes are investigated. - Graphical abstract: The incorporation of exo-bidendate bipyridine spacers into the Zn–H{sub 2}L system has yielded a series of new MOFs exhibiting topological evolution from 3-fold interpenetration to 6-fold interpenetration and 2D→3D parallel polycatenation. Highlights: ► The effect of the pyridyl-based spacers on the formation of MOFs was explored. ► Fine tune over the topology of the MOFs was achieved. ► An interesting structure of 2D→3D parallel polycatenation is reported.

  1. Effects of Ca Content on Formation and Photoluminescence Properties of CaAlSiN3:Eu2+ Phosphor by Combustion Synthesis

    PubMed Central

    Chung, Shyan-Lung; Huang, Shu-Chi

    2016-01-01

    Effects of Ca content (in the reactant mixture) on the formation and the photoluminescence properties of CaAlSiN3:Eu2+ phosphor (CASIN) were investigated by a combustion synthesis method. Ca, Al, Si, Eu2O3, NaN3, NH4Cl and Si3N4 powders were used as the starting materials and they were mixed and pressed into a compact which was then wrapped up with an igniting agent (i.e., Mg + Fe3O4). The compact was ignited by electrical heating under a N2 pressure of ≤1.0 MPa. By keeping the molar ratios of Al and Si (including the Si powder and the Si in Si3N4 powder) both at 1.00 and that of Eu2O3 at 0.02, XRD (X-ray diffraction) coupled with TEM-EDS (transmission electron microscope equipped with an energy-dispersive X-ray spectroscope) and SAED (selected area electron diffraction) measurements show that AlN:Eu2+ and Ca-α-SiAlON:Eu2+ are formed as the major phosphor products when the Ca molar ratio (denoted by Y) is equal to 0.25 and AlN:Eu2+ and Ca-α-SiAlON:Eu2+ could not be detected at Y ≥ 0.75 and ≥1.00, respectively. CASIN (i.e., CaAlSiN3:Eu2+) becomes the only phosphor product as Y is increased to 1.00 and higher. The extent of formation of CASIN increases with increasing Y up to 1.50 and begins to decrease as Y is further increased to 1.68. While the excitation wavelength regions are similar at various Y, the emission wavelength regions vary significantly as Y is increased from 0.25 to 1.00 due to different combinations of phosphor phases formed at different Y. The emission intensity of CASIN was found to vary with Y in a similar trend to its extent of formation. The Ca and Eu contents (expressed as molar ratios) in the synthesized products were found to increase roughly with increasing Y but were both lower than the respective Ca and Eu contents in the reactant mixtures. PMID:28773303

  2. Influence of particle size on band gap and dielectric properties of TiO2 nanomaterials

    NASA Astrophysics Data System (ADS)

    Avinash B., S.; Chathurmukha V., S.; Naveen C., S.; Rajeeva M., P.; Jayanna H., S.; Lamani, Ashok R.

    2016-05-01

    In this work TiO2 nanomaterial of different particle size were synthesized by varying the pH of the solution by hydrolysis and peptization method. These samples were characterized by XRD, UV and SEM. The XRD reveals the formation of anatase phase form of TiO2 nanoparticles having the particle size in the range 15 nm to 35 nm. The calculated band gap values by Tauc plot for the prepared samples increases with decrease in particle size. These samples are pelletized to study the dielectric properties using Impedence Analyzer Interface in the frequency range from 1 Hz to 1 M Hz. From the dielectric studies it was observed that dielectric constant, tanδ and dielectric loss were maximum in lower frequency range, as the frequency increases these dielectric parameters decreases rapidly at low frequency region and almost constant values were recorded at higher frequencies. At lower frequencies, the dielectric parameters (dielectric constant, loss, and tanδ) increases with increase of pH up to pH 8 due to space charge polarization. The value of dielectric constant recorded at pH 10 is almost same as that of pH 8, for slight decrease in the values were recorded for dielectric loss and tan δ at pH 10 due to space charge polarization with the particle size.

  3. Hole-transport properties of a low-band gap alternating polyfluorene

    NASA Astrophysics Data System (ADS)

    Debebe, Siraye E.; Mammo, Wendimagegn; Yohannes, Teketel; Tinti, Francesca; Martelli, Alessandro; Camaioni, Nadia

    2010-07-01

    The bulk transport properties of positive carriers in thin films of a low band-gap conjugated polymer, called APFO-Green5, have been investigated in the ac regime. The frequency-dependent impedance of an ITO/PEDOT:PSS/APFO-Green5/Al structure (where ITO is indium tin oxide and PEDOT:PSS is poly(3,4-ethylenedioxythiophene)/polystyrene sulphonic acid) was measured as a function of the dc applied bias. The capacitance response at low frequency gave indication of a combination of trapping and double-injection effects, while in the intermediate-high frequency range was determined by the transit time of injected holes. Hole mobility in APFO-Green5 thin films exhibited a Frenkel-like dependence on the applied electric field, with a field-dependent coefficient of around 8×10-3 (V cm-1)-1/2. A hole mobility close to 2×10-5 cm2 V-1 s-1 was achieved at the field of 3.5×105 V cm-1, in excellent agreement with that already reported by using a different bulk investigation technique.

  4. Study of structural and optical properties of chemically synthesized nanostructured cadmium zinc sulphide films for band gap tunability

    NASA Astrophysics Data System (ADS)

    Mochahari, P. K.; Sarma, K. C.

    2016-01-01

    Nanostructured cadmium zinc sulphide films have been deposited onto cleaned glass substrates by chemical bath deposition method at room temperature using polyvinyl alcohol as capping agent. X-ray diffraction analysis confirms the formation of cubic-phase cadmium zinc sulphide films. Crystallite size obtained from the calculation of Scherrer's formula and Williamson-Hall plot as well as size-strain plot is found to decrease with the increase in zinc concentration. The films have very high dislocation density of the order of 1016 m-2, whereas the strain is of the order of 10-3. Scanning electron microscopic image reveals that the particles are agglomerated to form nanoclusters and energy-dispersive X-ray analysis confirms that films are composed of cadmium, zinc and sulphur. High-resolution transmission electron microscopic image reveals that the shape of the particles is nearly spherical, uniformly distributed. Selected-area electron diffraction pattern supports the formation of cubic phase of the film. Optical absorption peaks of the films shift towards lower wavelength side and their optical band gap increases with the increase in zinc concentration. The increase in zinc concentration enhances the photoluminescence emission intensity, whose emission is in the green region of visible spectrum.

  5. Magneto photoluminescence measurements of tungsten disulphide monolayers

    NASA Astrophysics Data System (ADS)

    Kuhnert, Jan; Rahimi-Iman, Arash; Heimbrodt, Wolfram

    2017-03-01

    Layered transition-metal dichalcogenides have attracted great interest in the last few years. Thinned down to the monolayer limit they change from an indirect band structure to a direct band gap in the visible region. Due to the monolayer thickness the inversion symmetry of the crystal is broken and spin and valley are coupled to each other. The degeneracy between the two equivalent valleys, K and K‧, respectively, can be lifted by applying an external magnetic field. Here, we present photoluminescence measurements of CVD-grown tungsten disulphide (WS2) monolayers at temperatures of 2 K. By applying magnetic fields up to 7 T in Faraday geometry, a splitting of the photoluminescence peaks can be observed. The magnetic field dependence of the A-exciton, the trion and three bound exciton states is discussed and the corresponding g-factors are determined.

  6. Structural and photoluminescent properties of nanowires formed by the metal-assisted chemical etching of monocrystalline silicon with different doping level

    SciTech Connect

    Georgobiani, V. A. Gonchar, K. A.; Osminkina, L. A.; Timoshenko, V. Yu.

    2015-08-15

    Silicon-nanowire layers grown by the metal-assisted chemical etching of (100)-oriented p-type monocrystalline silicon substrates with a resistivity of 10 and 0.001 Ω · cm are studied by electron microscopy, Raman scattering, and photoluminescence measurements. It is established that nanowires grown on lightly doped substrates are structurally nonporous and formed as crystalline cores covered by nanocrystals 3–5 nm in dimensions. Nanowires grown on heavily doped substrates are structurally porous and contain both small nanocrystals and coarser crystallites with equilibrium charge carriers that influence interband radiative recombination. It is found that the photoluminescence intensity of nanowires in the spectral range 1.3–2.0 eV depends on the presence of molecular oxygen.

  7. Two-dimensional molybdenum tungsten diselenide alloys: photoluminescence, Raman scattering, and electrical transport.

    PubMed

    Zhang, Mei; Wu, Juanxia; Zhu, Yiming; Dumcenco, Dumitru O; Hong, Jinhua; Mao, Nannan; Deng, Shibin; Chen, Yanfeng; Yang, Yanlian; Jin, Chuanhong; Chaki, Sunil H; Huang, Ying-Sheng; Zhang, Jin; Xie, Liming

    2014-07-22

    Two-dimensional transition-metal dichalcogenide alloys have attracted intense attention due to their tunable band gaps. In the present work, photoluminescence, Raman scattering, and electrical transport properties of monolayer and few-layer molybdenum tungsten diselenide alloys (Mo1-xWxSe2, 0 ≤ x ≤ 1) are systematically investigated. The strong photoluminescence emissions from Mo1-xWxSe2 monolayers indicate composition-tunable direct band gaps (from 1.56 to 1.65 eV), while weak and broad emissions from the bilayers indicate indirect band gaps. The first-order Raman modes are assigned by polarized Raman spectroscopy. Second-order Raman modes are assigned according to its frequencies. As composition changes in Mo1-xWxSe2 monolayers and few layers, the out-of-plane A1g mode showed one-mode behavior, while B2g(1) (only observed in few layers), in-plane E2g(1), and all observed second-order Raman modes showed two-mode behaviors. Electrical transport measurement revealed n-type semiconducting transport behavior with a high on/off ratio (>10(5)) for Mo1-xWxSe2 monolayers.

  8. Comparative Photoluminescence Properties and Judd-Ofelt Analysis of Eu3+ Ion-Activated Metal Molybdate Phosphors A2MoO6:Eu3+ (A = La, Y, Gd and Bi)

    NASA Astrophysics Data System (ADS)

    Han, Bing; Liu, Bingkun; Zhang, Jie; Li, Pengju; Shi, Hengzhen

    2017-07-01

    A class of red-emitting Eu3+ ion-activated metal molybdate A2MoO6:Eu3+ (A = La, Y, Gd and Bi) phosphors were synthesized by a conventional high-temperature solid-state reaction method. The x-ray diffraction patterns, scanning electron microscope images, Fourier transform infrared spectra, ultraviolet-visible diffuse reflection spectra as well as photoluminescence properties were measured to characterize the as-prepared samples. The photoluminescence properties including excitation/emission spectra, decay curves, Commission Internationale de L'Eclairage chromaticity coordinates and quantum efficiency were comparatively investigated in detail. The Judd-Ofelt theory was also applied to understand the radiative properties of f-f transitions of Eu3+ ions in this system for the first time. The as-prepared phosphors can be effectively excited with near-ultraviolet and/or blue light, and exhibit red emission belonging to the prevailing 5D0 → 7F2 transitions of Eu3+ with short decay time (millisecond level). The results demonstrated that A2MoO6:Eu3+ (A = La, Y, Gd and Bi) phosphors could have potential application as red-emitting phosphors in white light-emitting diodes based on near-ultraviolet and/or blue light-emitting diode chips.

  9. Comparative Photoluminescence Properties and Judd-Ofelt Analysis of Eu3+ Ion-Activated Metal Molybdate Phosphors A2MoO6:Eu3+ (A = La, Y, Gd and Bi)

    NASA Astrophysics Data System (ADS)

    Han, Bing; Liu, Bingkun; Zhang, Jie; Li, Pengju; Shi, Hengzhen

    2017-03-01

    A class of red-emitting Eu3+ ion-activated metal molybdate A2MoO6:Eu3+ (A = La, Y, Gd and Bi) phosphors were synthesized by a conventional high-temperature solid-state reaction method. The x-ray diffraction patterns, scanning electron microscope images, Fourier transform infrared spectra, ultraviolet-visible diffuse reflection spectra as well as photoluminescence properties were measured to characterize the as-prepared samples. The photoluminescence properties including excitation/emission spectra, decay curves, Commission Internationale de L'Eclairage chromaticity coordinates and quantum efficiency were comparatively investigated in detail. The Judd-Ofelt theory was also applied to understand the radiative properties of f-f transitions of Eu3+ ions in this system for the first time. The as-prepared phosphors can be effectively excited with near-ultraviolet and/or blue light, and exhibit red emission belonging to the prevailing 5D0 → 7F2 transitions of Eu3+ with short decay time (millisecond level). The results demonstrated that A2MoO6:Eu3+ (A = La, Y, Gd and Bi) phosphors could have potential application as red-emitting phosphors in white light-emitting diodes based on near-ultraviolet and/or blue light-emitting diode chips.

  10. Photoluminescence and thermoluminescence properties of Eu(2)(+) doped and Eu(2+) ,Dy(3)(+) co-doped Ba2 MgSi2 O7 phosphors.

    PubMed

    Sao, Sanjay Kumar; Brahme, Nameeta; Bisen, D P; Tiwari, Geetanjali

    2016-11-01

    In this work, we report the preparation, characterization, comparison and luminescence mechanisms of Eu(2)(+) -doped and Eu(2)(+) ,Dy(3)(+) -co-doped Ba2 MgSi2 O7 (BMSO) phosphors. Prepared phosphors were synthesized via a high temperature solid-state reaction method. All prepared phosphors appeared white. The phase structure, particle size, and elemental analysis were analyzed using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) analysis. The luminescence properties of the phosphors were investigated by thermoluminescence (TL) and photoluminescence (PL). The PL excitation and emission spectra of Ba2 MgSi2 O7 :Eu(2)(+) showed the peak to be around 381 nm and 490 nm respectively. The PL excitation spectrum of Ba2 MgSi2 O7 :Eu(2)(+) Dy(3)(+) showed the peak to be around 341 nm and 388 nm, and the emission spectrum had a broad band around 488 nm. These emissions originated from the 4f(6) 5d(1) to 4f(7) transition of Eu(2)(+) . TL analysis revealed that the maximum TL intensity was found at 5 mol% of Eu(2)(+) doping in Ba2 MgSi2 O7 phosphors after 15 min of ultraviolet (UV) light exposure. TL intensity was increased when Dy(3)(+) ions were co-doped in Ba2 MgSi2 O7 :Eu(2)(+) and maximum TL intensity was observed for 2 mol% of Dy(3)(+) . TL emission spectra of Ba1.95 MgSi2 O7 :0.05Eu(2)(+) and Ba1.93 MgSi2 O7 :0.05Eu(2)(+) ,0.02Dy(3)(+) phosphors were found at 500 nm. TL intensity increased with UV exposure time up to 15 min, then decreased for the higher UV radiation dose for both Eu doping and Eu,Dy co-doping. The trap depths were calculated to be 0.54 eV for Ba1.95 MgSi2 O7 :0.05Eu(2)(+) and 0.54 eV and 0.75 eV for Ba1.93 MgSi2 O7 :0.05Eu(2)(+) ,0.02Dy(3)(+) phosphors. It was observed that co-doping with small amounts of Dy(3)(+) enhanced the thermoluminescence properties of Ba2 MgSi2 O7 phosphor. Copyright © 2016 John Wiley & Sons, Ltd. [Correction added on 5 April 2016, after first online publication

  11. Enhanced photoluminescence and thermal properties of size mismatch in Sr(2.97-x-y)Eu0.03Mg(x)Ba(y)SiO5 for high-power white light-emitting diodes.

    PubMed

    Ci, Zhipeng; Que, Meidan; Shi, Yurong; Zhu, Ge; Wang, Yuhua

    2014-02-17

    In this Study, Mg(2+) and Ba(2+) act to enhance the maximum emission of Sr2.97SiO5:0.03Eu(2+) significantly and redshift the emission band to the orange-red region in Sr(2.97-x-y)Mg(x)Ba(y)SiO5:0.03Eu(2+). Size mismatch between the host and the doped cations tunes the photoluminescence spectra shift systematically. A slight blue shift when increasing the amount of Mg(2+) occurs in the Sr(2.97-x)Eu0.03Mg(x)SiO5 lattices, and a rapid red shift occurs when Ba(2+) is codoped in the Sr(2.57-y)Eu0.03Mg0.4Ba(y)SiO5 lattices. The emission spectra were tuned from 585 to 601 nm by changing the concentration of Ba(2+). Accordingly, we propose the underlying mechanisms of the changes in the photoluminescence properties by adjusting the cation composition of phosphors. The influence of the size mismatch on the thermal quenching is also observed. This mechanism could be widely applied to oxide materials and could be useful in tuning the photoluminescence properties, which are sensitive to local coordination environment. The emission bands of Sr(2.97-x-y)Eu0.03Mg(x)Ba(y)SiO5 show the blue shift with increasing temperature, which could be described in terms of back tunneling of the excited electrons from the low-energy excited state to the high-energy excited state. Thus, the Sr(2.97-x-y)Eu0.03Mg(x)Ba(y)SiO5 phosphors could have potential applications in the daylight LEDs or warm white LEDs.

  12. Photoluminescence properties and energy transfer in Ce(3+) /Dy(3+) co-doped Sr(3) MgSi(2) O(8) phosphors for potential application in ultraviolet white light-emitting diodes.

    PubMed

    Yu, Hong; Zi, Wenwen; Lan, Shi; Gan, Shucai; Zou, Haifeng; Xu, Xuechun; Hong, Guangyan

    2013-01-01

    Sr(3) MgSi(2) O(8) :Ce(3+) , Dy(3+) phosphors were prepared by a solid-state reaction technique and the photoluminescence properties were investigated. The emission spectra show not only a band due to Ce(3+) ions (403 nm) but also as a band due to Dy(3+) ions (480, 575 nm) (UV light excitation). The photoluminescence properties reveal that effective energy transfer occurs in Ce(3+) /Dy(3+) co-doped Sr(3) MgSi(2) O(8)phosphors, and the co-doping of Ce(3+) could enhance the emission intensity of Dy(3+) to a certain extent by transferring its energy to Dy(3+) . The Ce(3+) /Dy(3+) energy transfer was investigated by emission/excitation spectra, and photoluminescence decay behaviors. In Sr2.94 MgSi2 O8 :0.01Ce(3+) , 0.05Dy(3+) phosphors, the fluorescence lifetime of Dy(3+) (from 3.35 to 27.59 ns) is increased whereas that of Ce(3+) is greatly decreased (from 43.59 to 13.55 ns), and this provides indirect evidence of the Ce(3+) to Dy(3+) energy transfer. The varied emitted color of Sr(3) MgSi(2) O(8):Ce(3+) , Dy(3+) phosphors from blue to white were achieved by altering the concentration ratio of Ce(3+) and Dy(3+) . These results indicate Sr(3) MgSi(2) O(8):Ce(3+) , Dy(3+) may be as a candidate phosphor for white light-emitting diodes. Copyright © 2012 John Wiley & Sons, Ltd.

  13. The dual roles of functional groups in the photoluminescence of graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Wang, Shujun; Cole, Ivan S.; Zhao, Dongyuan; Li, Qin

    2016-03-01

    The photoluminescent properties of graphene nanoparticle (named graphene quantum dots) have attracted significant research attention in recent years owing to their profound application potential. However, the photoluminescence (PL) origin of this class of nanocarbons is still unclear. In this paper, combining direct experimental evidence enabled by a facile size-tunable oxygenated graphene quantum dots (GQDs) synthesis method and theoretical calculations, the roles of the aromatic core, functional groups and disordered structures (i.e. defects and sp3 carbon) in the PL of oxygenated GQDs are elucidated in detail. In particular, we found that the functional groups on GQDs play dual roles in the overall emission: (1) they enable π* --> n and σ* --> n transitions, resulting in a molecular type of PL, spectrally invariable with change of particle size or excitation energy; (2) similar to defects and sp3 carbon, functional groups also induce structural deformation to the aromatic core, leading to mid-gap states or, in other words, energy traps, causing π* --> mid-gap states --> π transitions. Therefore, functional groups contribute to both the blue edge and the red shoulder of GQDs' PL spectra. The new insights on the role of functional groups in PL of fluorescent nanocarbons will enable better designs of this new class of materials.The photoluminescent properties of graphene nanoparticle (named graphene quantum dots) have attracted significant research attention in recent years owing to their profound application potential. However, the photoluminescence (PL) origin of this class of nanocarbons is still unclear. In this paper, combining direct experimental evidence enabled by a facile size-tunable oxygenated graphene quantum dots (GQDs) synthesis method and theoretical calculations, the roles of the aromatic core, functional groups and disordered structures (i.e. defects and sp3 carbon) in the PL of oxygenated GQDs are elucidated in detail. In particular, we found

  14. Microstructure and Mechanical Properties of Narrow Gap Laser-Arc Hybrid Welded 40 mm Thick Mild Steel

    PubMed Central

    Zhang, Chen; Li, Geng; Gao, Ming; Zeng, XiaoYan

    2017-01-01

    Both laser-arc hybrid welding and narrow gap welding have potential for the fabrication of thick sections, but their combination has been seldom studied. In this research, 40 mm thick mild steel was welded by narrow gap laser-arc hybrid welding. A weld with smooth layer transition, free of visible defects, was obtained by nine passes at a 6 mm width narrow gap. The lower part of the weld has the lowest mechanical properties because of the lowest amount of acicular ferrite, but its ultimate tensile strength and impact absorbing energy is still 49% and 60% higher than those of base metal, respectively. The microhardness deviation of all filler layers along weld thickness direction is no more than 15 HV0.2, indicating that no temper softening appeared during multiple heat cycles. The results provide an alternative technique for improving the efficiency and quality of welding thick sections. PMID:28772469

  15. Structural characterization, absorption and photoluminescence study of symmetrical azomethines with long aliphatic chains

    NASA Astrophysics Data System (ADS)

    Iwan, Agnieszka; Schab-Balcerzak, Ewa; Grucela-Zajac, Marzena; Skorka, Lukasz

    2014-01-01

    In this study, we investigated structural and optical properties of three symmetrical azomethines bis(4-(4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 11-heptadecafluoroundecyloxy)benzylidene)benzene-1,4-diamine (SAz1), bis(4-(4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 11-heptadecafluoroundecyloxy)benzylidene)biphenyl-4,4‧-diamine (SAz2) and 4,4‧-methylenebis(N-(4-(octadecyloxy)benzylidene)benzenamine (SAz3). Electronic properties, such as orbital energies and resulting energy gap of the three symmetrical azomethines were calculated theoretically by density functional theory (DFT). The photoluminescence (PL) and absorption UV-vis properties of the azomethines were investigated in chloroform solution. The effect of excitation wavelength and concentration on the PL properties was detected as well. Azomethines emitted violet, blue or green light. The highest PL intensity was found for SAz1.

  16. Anisotropic magnetic properties and superzone gap formation in CeGe single crystal.

    PubMed

    Das, Pranab Kumar; Kumar, Neeraj; Kulkarni, R; Dhar, S K; Thamizhavel, A

    2012-04-11

    Single crystals of CeGe and its non-magnetic analog LaGe have been grown by the Czochralski method. The CeGe compound crystallizes in the orthorhombic FeB-type crystal structure with the space group Pnma (#62). The anisotropic magnetic properties have been investigated for well oriented single crystals by measuring the magnetic susceptibility, electrical resistivity and heat capacity. It has been found that CeGe orders antiferromagnetically at 10.5 K. Both transport and magnetic studies have revealed large anisotropy, reflecting the orthorhombic crystal structure. The magnetization data at 1.8 K reveal metamagnetic transitions along the [010] direction at 4.8 and 6.4 T and along the [100] direction at a critical field of 10.7 T, while the magnetization along the [001] direction increases linearly without any anomaly up to a field of 16 T. From the magnetic susceptibility and the magnetization measurements it has been found that the [010] direction is the easy axis of magnetization. The electrical resistivity along the three crystallographic directions exhibits an upturn at T(N), indicating superzone gap formation below T(N) in this compound. We have performed crystal electric field analysis on the magnetic susceptibility and the heat capacity data and found that the ground state is a doublet, and the energies of splitting from the ground state to the first and second excited doublet states were estimated to be 39 and 111 K, respectively.

  17. Transport, thermal, and magnetic properties of the narrow-gap semiconductor CrSb2

    NASA Astrophysics Data System (ADS)

    Sales, Brian C.; May, Andrew F.; McGuire, Michael A.; Stone, Matthew B.; Singh, David J.; Mandrus, David

    2012-12-01

    Resistivity, the Hall effect, the Seebeck coefficient, thermal conductivity, heat capacity, and magnetic susceptibility data are reported for CrSb2 single crystals. In spite of some unusual features in electrical transport and Hall measurements below 100 K, only one phase transition is found in the temperature range from 2 to 750 K corresponding to long-range antiferromagnetic order below TN ≈ 273 K. Many of the low-temperature properties can be explained by the thermal depopulation of carriers from the conduction band into a low-mobility band located approximately 16 meV below the conduction-band edge, as deduced from the Hall effect data. In analogy with what occurs in Ge, the low-mobility band is likely an impurity band. The Seebeck coefficient, S, is large and negative for temperatures from 2 to 300 K ranging from ≈-70μV/K at 300 K to -4500μV/K at 18 K. A large maximum in |S| at 18 K is likely due to phonon drag, with the abrupt drop in |S| below 18 K due to the thermal depopulation of the high-mobility conduction band. The large thermal conductivity between 10 and 20 K (≈350 W/m K) is consistent with this interpretation, as are detailed calculations of the Seebeck coefficient made using the complete calculated electronic structure. These data are compared to data reported for FeSb2, which crystallizes in the same marcasite structure, and FeSi, another unusual narrow-gap semiconductor.

  18. Investigation on the properties of omnidirectional photonic band gaps in two-dimensional plasma photonic crystals

    SciTech Connect

    Zhang, Hai-Feng; Liu, Shao-Bin; Li, Bing-Xiang

    2016-01-15

    The properties of omnidirectional photonic band gaps (OBGs) in two-dimensional plasma photonic crystals (2D PPCs) are theoretically investigated by the modified plane wave expansion method. In the simulation, we consider the off-plane incident wave vector. The configuration of 2D PPCs is the triangular lattices filled with the nonmagnetized plasma cylinders in the homogeneous and isotropic dielectric background. The calculated results show that the proposed 2D PPCs possess a flatbands region and the OBGs. Compared with the OBGs in the conventional 2D dielectric-air PCs, it can be obtained more easily and enlarged in the 2D PPCs with a similar structure. The effects of configurational parameters of the PPCs on the OBGs also are studied. The simulated results demonstrate that the locations of OBGs can be tuned easily by manipulating those parameters except for changing plasma collision frequency. The achieved OBGs can be enlarged by optimizations. The OBGs of two novel configurations of PPCs with different cross sections are computed for a comparison. Both configurations have the advantages of obtaining the larger OBGs compared with the conventional configuration, since the symmetry of 2D PPCs is broken by different sizes of periodically inserted plasma cylinders or connected by the embedded plasma cylinders with thin veins. The analysis of the results shows that the bandwidths of OBGs can be tuned by changing geometric and physical parameters of such two PPCs structures. The theoretical results may open a new scope for designing the omnidirectional reflectors or mirrors based on the 2D PPCs.

  19. Highly Photoluminescent Molybdenum Oxide Quantum Dots: One-Pot Synthesis and Application in 2,4,6-Trinitrotoluene Determination.

    PubMed

    Xiao, Sai Jin; Zhao, Xiao Jing; Hu, Ping Ping; Chu, Zhao Jun; Huang, Cheng Zhi; Zhang, Li

    2016-03-01

    As a well-studied transition-metal semiconductor material, MoOx has a wider band gap than molybdenum disulfide (MoS2), and its property varies dramatically for the existence of several different allotropes and suboxide phases of molybdenum oxides (MoOx, x < 3). In this manuscript, a one-pot method possessing the advantages of one pot, easily prepared, rapid, and environmentally friendly, has been developed for facile synthesis of highly photoluminescent MoOx quantum dots (MoOx QDs), in which commercial molybdenum disulfide (MoS2) powder and hydrogen peroxide (H2O2) are employed as the precursor and oxidant, respectively. The obtained MoOx QDs can be further utilized as an efficient photoluminescent probe, and a new turn-off sensor is developed for 2,4,6-trinitrotoluene (TNT) determination based on the fact that the photoluminescence of MoOx QDs can be quenched by the Meisenheimer complexes formed in the strong alkali solution through the inner filter effect (IFE). Under the optimal conditions, the decreased photoluminescence of MoOx QDs shows a good linear relationship to the concentration of TNT ranging from 0.5 to 240.0 μM, and the limit of detection was 0.12 μM (3σ/k). With the present turn-off sensor, TNT in river water samples can be rapidly and selectively detected without tedious sample pretreatment processes.

  20. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Localized electronic states in gaps on hole-net structures of silicon

    NASA Astrophysics Data System (ADS)

    Huang, Wei-Qi; Lü, Quan; Zhang, Rong-Tao; Wang, Xiao-Yun; Yu, Shi-Qiang

    2009-11-01

    Hole-net structure silicon is fabricated by laser irradiation and annealing, on which a photoluminescence (PL) band in a the region of 650-750 nm is pinned and its intensity increases obviously after oxidation. It is found that the PL intensity changes with both laser irradiation time and annealing time. Calculations show that some localized states appear in the band gap of the smaller nanocrystal when Si = O bonds or Si-O-Si bonds are passivated on the surface. It is discovered that the density and the number of Si = O bonds or Si-O-Si bonds related to both the irradiation time and the annealing time obviously affect the generation of the localized gap states of hole-net silicon, by which the production of stimulated emission through controlling oxidation time can be explained.

  1. Growth and Optical Properties of Direct Band Gap Ge/Ge0.87Sn0.13 Core/Shell Nanowire Arrays.

    PubMed

    Assali, S; Dijkstra, A; Li, A; Koelling, S; Verheijen, M A; Gagliano, L; von den Driesch, N; Buca, D; Koenraad, P M; Haverkort, J E M; Bakkers, E P A M

    2017-03-08

    Group IV semiconductor optoelectronic devices are now possible by using strain-free direct band gap GeSn alloys grown on a Ge/Si virtual substrate with Sn contents above 9%. Here, we demonstrate the growth of Ge/GeSn core/shell nanowire arrays with Sn incorporation up to 13% and without the formation of Sn clusters. The nanowire geometry promotes strain relaxation in the Ge0.87Sn0.13 shell and limits the formation of structural defects. This results in room-temperature photoluminescence centered at 0.465 eV and enhanced absorption above 98%. Therefore, direct band gap GeSn grown in a nanowire geometry holds promise as a low-cost and high-efficiency material for photodetectors operating in the short-wave infrared and thermal imaging devices.

  2. Photoluminescence of Diamondoid Crystals

    SciTech Connect

    Clay, William; Sasagawa, Takao; Iwasa, Akio; Liu, Zhi; Dahl, Jeremy E.; Carlson, Robert M.K.; Kelly, Michael; Melos, Nicholas; Shen, Zhi-Xun; /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept. /Stanford U., Geballe Lab. /SIMES, Stanford

    2012-04-03

    The photoluminescence of diamondoids in the solid state is examined. All of the diamondoids are found to photoluminesce readily with initial excitation wavelengths ranging from 233 nm to 240 nm (5.3 eV). These excitation energies are more than 1 eV lower than any previously studied saturated hydrocarbon material. The emission is found to be heavily shifted from the absorption, with emission wavelengths of roughly 295 nm (4.2 eV) in all cases. In the dissolved state, however, no uorescence is observed for excitation wavelengths as short as 200 nm. We also discuss predictions and measurements of the quantum yield. Our predictions indicate that the maximum yield may be as high as 25%. Our measurement of one species, diamantane, gives a yield of 11%, the highest ever reported for a saturated hydrocarbon, even though it was likely not at the optimal excitation wavelength.

  3. Crystal structure and photoluminescence properties of a new monomeric copper(II) complex: bis(3-{[(3-hydroxypropyl)imino]methyl}-4-nitrophenolato-κ(3)O,N,O')copper(II).

    PubMed

    Kocak, Cagdas; Oylumluoglu, Gorkem; Donmez, Adem; Coban, M Burak; Erkarslan, Ugur; Aygun, Muhittin; Kara, Hulya

    2017-05-01

    Copper(II)-Schiff base complexes have attracted extensive interest due to their structural, electronic, magnetic and luminescence properties. The title novel monomeric Cu(II) complex, [Cu(C10H11N2O4)2], has been synthesized by the reaction of 3-{[(3-hydroxypropyl)imino]methyl}-4-nitrophenol (H2L) and copper(II) acetate monohydrate in methanol, and was characterized by elemental analysis, UV and IR spectroscopies, single-crystal X-ray diffraction analysis and a photoluminescence study. The Cu(II) atom is located on a centre of inversion and is coordinated by two imine N atoms, two phenoxy O atoms in a mutual trans disposition and two hydroxy O atoms in axial positions, forming an elongated octahedral geometry. In the crystal, intermolecular O-H...O hydrogen bonds link the molecules to form a one-dimensional chain structure and π-π contacts also connect the molecules to form a three-dimensional structure. The solid-state photoluminescence properties of the complex and free H2L have been investigated at room temperature in the visible region. When the complex and H2L are excited under UV light at 349 nm, the complex displays a strong green emission at 520 nm and H2L displays a blue emission at 480 nm.

  4. Optical properties of Ge-rich G e1 -xS ix alloys: Compositional dependence of the lowest direct and indirect gaps

    NASA Astrophysics Data System (ADS)

    Xu, Chi; Gallagher, J. D.; Senaratne, C. L.; Menéndez, J.; Kouvetakis, J.

    2016-03-01

    Ge-rich G e1 -xS ix alloys have been investigated using spectroscopic ellipsometry and photoluminescence at room temperature. Special emphasis was placed on the compositional dependence of the lowest-energy interband transitions. For x ≤0.05 , a compositional range of particular interest for modern applications, we find E0=0.799 (1 ) +3.214 (45 ) x +0.080 (44 ) x2 (in eV) for the lowest direct gap. The compositional dependence of the indirect gap is obtained from photoluminescence as Eind=0.659 (4 ) +1.18 (17 ) x (in eV). We find no significant discrepancies between these results and the extrapolations from measurements at higher Si concentrations. Such discrepancies had been suggested by recent work on G e1 -xS ix films on Si. Accurate knowledge of the interband transition energies is an important requirement for the design of devices incorporating Ge-rich G e1 -xS ix alloys and for the understanding of more complex systems, such as ternary G e1 -x -yS ixS ny alloys, in terms of its binary constituents.

  5. Mechanisms behind blue, green, and red photoluminescence emissions in CaWO4 and CaMoO4 powders

    NASA Astrophysics Data System (ADS)

    Campos, A. B.; Simões, A. Z.; Longo, E.; Varela, J. A.; Longo, V. M.; de Figueiredo, A. T.; De Vicente, F. S.; Hernandes, A. C.

    2007-07-01

    A combined experimental and theoretical study was conducted to analyze the photoluminescence (PL) properties of ordered and disordered CaWO4 (CW) and CaMoO4 (CM) powders. Two mechanisms were found to be responsible for photoluminescence emission in CW and CM powders. The first one, in the disordered powders, was caused by oxygen complex vacancies [MO3•VOx], [MO3•VO•] and [MO3•VO••], where M =W or Mo, which leads to additional levels in the band gap. The second mechanism, in ordered powders, was caused by an intrinsic slight distortion of the [WO4] or [MoO4] tetrahedral in the short range.

  6. Photoluminescence and compositional-structural properties of ion-beam sputter deposited Er-doped TiO{sub 2−x}N{sub x} films: Their potential as a temperature sensor

    SciTech Connect

    Scoca, D. Morales, M.; Merlo, R.; Alvarez, F.; Zanatta, A. R.

    2015-05-28

    Er-doped TiO{sub 2−x}N{sub x} films were grown by Ar{sup +} ion-beam sputtering a Ti + Er target under different N{sub 2} + O{sub 2} high-purity atmospheres. The compositional-structural properties of the samples were investigated after thermal annealing the films up to 1000 °C under a flow of oxygen. Sample characterization included x-ray photoelectron spectroscopy, grazing incidence x-ray diffraction, Raman scattering, and photoluminescence experiments. According to the experimental data, both composition and atomic structure of the samples were very sensitive to the growth conditions and annealing temperature. In the as-deposited form, the N-rich TiO{sub 2−x}N{sub x} films presented TiN crystallites and no photoluminescence. As the thermal treatments proceed, the films were transformed into TiO{sub 2} and Er{sup 3+}-related light emission were observed in the visible and near-infrared ranges at room-temperature. Whereas the development of TiO{sub 2} occurred due to the insertion-diffusion of oxygen in the films, light emission originated because of optical bandgap widening and/or structural-chemical variations in the vicinity of the Er{sup 3+} ions. Finally, the photoluminescence results in the visible range suggested the potential of the present samples in producing an optically based temperature sensor in the ∼150–500 K range.

  7. Structural, vibrational and photoluminescence properties of Sr{sub (1-x)}Pb{sub x}MoO{sub 4} solid solution synthesized by solid state reaction

    SciTech Connect

    Hallaoui, A.; Taoufyq, A.; Arab, M.; Bakiz, B.; Benlhachemi, A.; Bazzi, L.; Valmalette, J-C.; Villain, S.; Guinneton, F.; Gavarri, J-R.

    2016-07-15

    Highlights: • The solid solution Sr{sub (1-x)}Pb{sub (x)}MoO{sub 4} is characterized by X-ray diffraction. • Raman spectroscopy confirm that the solid solution is disordered. • Photoluminescence experiments are carried out under X-ray excitation. • Emission bands can be decomposed into four components between 2.1 and 2.9 eV. • The intensities of emission bands reach a maximum for 0.1 < x < 0.4. - Abstract: In this paper, strontium lead molybdate Sr{sub 1-x}Pb{sub x}MoO{sub 4} polycrystalline samples with 0 ≤ x ≤ 1 were prepared by solid state preparation method at 1000 °C. These materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and micro-Raman spectroscopy. Their photoluminescence responses were analyzed under X-ray excitation. Rietveld refinements indicate that all the materials present a scheelite-type tetragonal structure. Micro-Raman spectra confirmed the formation of the solid solution with a specific effect due to Sr-O-Mo and Pb-O-Mo links in the scheelite structure. SEM images showed modifications in the shapes and grain sizes as x increased. Broad photoluminescent emission bands were observed in the energy range 2.1–2.9 eV. The emission bands were decomposed into four gaussian components. The intensities of all components presented a strong maximum in the composition range 0.1 < x < 0.4.

  8. Structural and optical properties of size controlled Si nanocrystals in Si{sub 3}N{sub 4} matrix: The nature of photoluminescence peak shift

    SciTech Connect

    Zelenina, A. Hiller, D.; Gutsch, S.; Zacharias, M.; Dyakov, S. A.; Trouillet, V.; Bruns, M.; Mirabella, S.; Löper, P.; López-Conesa, L.; López-Vidrier, J.; Peiró, F.; Garrido, B. [MIND-IN2UB, Departament d’Electrònica, Universitat de Barcelona, C Estradé, S. [MIND-IN2UB, Departament d’Electrònica, Universitat de Barcelona, C CCiT, Scientific and Technical Centers, Universitat de Barcelona, C and others

    2013-11-14

    Superlattices of Si{sub 3}N{sub 4} and Si-rich silicon nitride thin layers with varying thickness were prepared by plasma enhanced chemical vapor deposition. After high temperature annealing, Si nanocrystals were formed in the former Si-rich nitride layers. The control of the Si quantum dots size via the SiN{sub x} layer thickness was confirmed by transmission electron microscopy. The size of the nanocrystals was well in agreement with the former thickness of the respective Si-rich silicon nitride layers. In addition X-ray diffraction evidenced that the Si quantum dots are crystalline whereas the Si{sub 3}N{sub 4} matrix remains amorphous even after annealing at 1200 °C. Despite the proven Si nanocrystals formation with controlled sizes, the photoluminescence was 2 orders of magnitude weaker than for Si nanocrystals in SiO{sub 2} matrix. Also, a systematic peak shift was not found. The SiN{sub x}/Si{sub 3}N{sub 4} superlattices showed photoluminescence peak positions in the range of 540–660 nm (2.3–1.9 eV), thus quite similar to the bulk Si{sub 3}N{sub 4} film having peak position at 577 nm (2.15 eV). These rather weak shifts and scattering around the position observed for stoichiometric Si{sub 3}N{sub 4} are not in agreement with quantum confinement theory. Therefore theoretical calculations coupled with the experimental results of different barrier thicknesses were performed. As a result the commonly observed photoluminescence red shift, which was previously often attributed to quantum-confinement effect for silicon nanocrystals, was well described by the interference effect of Si{sub 3}N{sub 4} surrounding matrix luminescence.

  9. Gap junctions.

    PubMed

    Nielsen, Morten Schak; Axelsen, Lene Nygaard; Sorgen, Paul L; Verma, Vandana; Delmar, Mario; Holstein-Rathlou, Niels-Henrik

    2012-07-01

    Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease. © 2012 American Physiological Society. Compr Physiol 2:1853-1872, 2012.

  10. Gap Junctions

    PubMed Central

    Nielsen, Morten Schak; Axelsen, Lene Nygaard; Sorgen, Paul L.; Verma, Vandana; Delmar, Mario; Holstein-Rathlou, Niels-Henrik

    2013-01-01

    Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease. © 2012 American Physiological Society. Compr Physiol 2:1981-2035, 2012. PMID:23723031

  11. Modifying the band gap and optical properties of Germanium nanowires by surface termination

    NASA Astrophysics Data System (ADS)

    Legesse, Merid; Fagas, Giorgos; Nolan, Michael

    2017-02-01

    Semiconductor nanowires, based on silicon (Si) or germanium (Ge) are leading candidates for many ICT applications, including next generation transistors, optoelectronics, gas and biosensing and photovoltaics. Key to these applications is the possibility to tune the band gap by changing the diameter of the nanowire. Ge nanowires of different diameter have been studied with H termination, but, using ideas from chemistry, changing the surface terminating group can be used to modulate the band gap. In this paper we apply the generalised gradient approximation of density functional theory (GGA-DFT) and hybrid DFT to study the effect of diameter and surface termination using -H, -NH2 and -OH groups on the band gap of (001), (110) and (111) oriented germanium nanowires. We show that the surface terminating group allows both the magnitude and the nature of the band gap to be changed. We further show that the absorption edge shifts to longer wavelength with the -NH2 and -OH terminations compared to the -H termination and we trace the origin of this effect to valence band modifications upon modifying the nanowire with -NH2 or -OH. These results show that it is possible to tune the band gap of small diameter Ge nanowires over a range of ca. 1.1 eV by simple surface chemistry.

  12. Studies on surface plasmon resonance and photoluminescence of silver nanoparticles.

    PubMed

    Smitha, S L; Nissamudeen, K M; Philip, Daizy; Gopchandran, K G

    2008-11-01

    Silver nanoparticles of different sizes were prepared by citrate reduction and characterized by UV-vis absorbance spectra, TEM images and photoluminescence spectra. The morphology of the colloids obtained consists of a mixture of nanorods and spheres. The surface plasmon resonance (SPR) and photoemission properties of Ag nanoparticles are found to be sensitive to citrate concentration. A blue shift in SPR and an enhancement in photoluminescence intensity are observed with increase in citrate concentration. Effect of addition of KCl and variation of pH in photoluminescence was also studied.

  13. A new silicon phase with direct band gap and novel optoelectronic properties

    DOE PAGES

    Guo, Yaguang; Wang, Qian; Kawazoe, Yoshiyuki; ...

    2015-09-23

    Due to the compatibility with the well-developed Si-based semiconductor industry, there is considerable interest in developing silicon structures with direct energy band gaps for effective sunlight harvesting. In this paper, using silicon triangles as the building block, we propose a new silicon allotrope with a direct band gap of 0.61 eV, which is dynamically, thermally and mechanically stable. Symmetry group analysis further suggests that dipole transition at the direct band gap is allowed. Additionally, this new allotrope displays large carrier mobility (~104 cm/V · s) at room temperature and a low mass density (1.71 g/cm3), making it a promising materialmore » for optoelectronic applications.« less

  14. A new silicon phase with direct band gap and novel optoelectronic properties

    SciTech Connect

    Guo, Yaguang; Wang, Qian; Kawazoe, Yoshiyuki; Jena, Puru

    2015-09-23

    Due to the compatibility with the well-developed Si-based semiconductor industry, there is considerable interest in developing silicon structures with direct energy band gaps for effective sunlight harvesting. In this paper, using silicon triangles as the building block, we propose a new silicon allotrope with a direct band gap of 0.61 eV, which is dynamically, thermally and mechanically stable. Symmetry group analysis further suggests that dipole transition at the direct band gap is allowed. Additionally, this new allotrope displays large carrier mobility (~104 cm/V · s) at room temperature and a low mass density (1.71 g/cm3), making it a promising material for optoelectronic applications.

  15. A New Silicon Phase with Direct Band Gap and Novel Optoelectronic Properties

    PubMed Central

    Guo, Yaguang; Wang, Qian; Kawazoe, Yoshiyuki; Jena, Puru

    2015-01-01

    Due to the compatibility with the well-developed Si-based semiconductor industry, there is considerable interest in developing silicon structures with direct energy band gaps for effective sunlight harvesting. In this paper, using silicon triangles as the building block, we propose a new silicon allotrope with a direct band gap of 0.61 eV, which is dynamically, thermally and mechanically stable. Symmetry group analysis further suggests that dipole transition at the direct band gap is allowed. In addition, this new allotrope displays large carrier mobility (~104 cm/V · s) at room temperature and a low mass density (1.71 g/cm3), making it a promising material for optoelectronic applications. PMID:26395926

  16. Synthesis, characterization and photoluminescence properties of Bi³⁺ co-doped CaSiO₃:Eu³⁺ nanophosphor.

    PubMed

    Kumar, M Madesh; Krishna, R Hari; Nagabhushana, B M; Shivakumara, C

    2015-03-15

    Ceramic luminescent powders with the composition Ca(0.96-x)Eu0.04Bi(x)SiO3 (x=0.01-0.05) were prepared by solution combustion method. The nanopowders are characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and photoluminescence (PL) techniques. PXRD patterns of calcined (950°C for 3h) Ca(0.96-x)Eu0.04Bi(x)SiO3 powders exhibit monoclinic phase with mean crystallite sizes ranging from 28 to 48 nm. SEM micrographs show the products are foamy, agglomerated and fluffy in nature due to the large amount of gases liberated during combustion reaction. TEM micrograph shows the crystalline characteristics of the nanoparticles. Upon 280 nm excitation, the photoluminescence of the Ca(0.96-x)Eu0.04Bi(x)SiO3 particles show red emission at 611 nm corresponding to 5D0→7F2 transition. It is observed that PL intensity increases with Bi(3+) concentration. Our work demonstrates very interesting energy transfer from Bi(3+) to Eu(3+) in CaSiO3 host. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Synthesis of NaLuF4:Er3+, Yb3+, Ce3+ nanoparticles and study of photoluminescent properties in C - band

    NASA Astrophysics Data System (ADS)

    Khaydukov, K. V.; Rocheva, V. V.; Savelyev, A. G.; Sarycheva, M. E.; Asharchuk, I. M.

    2016-12-01

    The novel core@shell nanocrystals β-NaLuF4@NaLuF4 co-doped with rare-earth ions Er3+, Yb3+, Ce3+ have been synthesized. The nano-particles indicate the intensive lines of anti-Stokes luminescence in the telecommunication C - band of spectrum when pumped at 970-980 nm. The nanoparticles have been characterized by transmission electron microscopy and spectrofluorimetry. The nanoparticles have a size 40-80 nm and possess the intensive photo-luminescence 73 nm bandwidth centered around 1530 nm. The photo-luminescence kinetics of β-NaLuF4: Er3+/ Yb3+/ Ce3+ has been studied in IR range of spectrum. We have demonstrated that doping with cerium ions prevents serial stepwise excitation of erbium ions. Consequently, the lifetime of transition in erbium 4I13/2→4I15/2 has risen up to 6.9 ms. Intensity of 1530 nm line in Er3+ ions excited at 980 nm has been increased up to 6 times. Therefore, the nanoparticles are applicable to fabrication of compact waveguide amplifiers for C - band.

  18. Characterization and photoluminescence properties of ultrafine copper molybdate (α-CuMoO4) powders prepared via a combustion-like process

    NASA Astrophysics Data System (ADS)

    Benchikhi, Mohamed; El Ouatib, Rachida; Guillemet-Fritsch, Sophie; Er-Rakho, Lahcen; Durand, Bernard

    2016-11-01

    We report a simple method for preparing copper(II) molybdate (CuMoO4) powders via a combustion-like process. A gel was first prepared by the polymerizable complex method, where citric acid was used as a complexing and polymerizing agent and nitric acid was used as an oxidizing agent. The thermal decomposition behavior of the (CuMo)-precursor gel was studied by thermogravimetry-differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). We observed that the crystallization of CuMoO4 powder was completed at 450°C. The obtained homogeneous powder was composed of grains with sizes in the range from 150 to 500 nm and exhibited a specific surface area of approximately 5 m2/g. The average grain size increased with increasing annealing temperature. The as-prepared CuMoO4 crystals showed a strong green photoluminescence emission at room temperature under excitation at 290 nm, which we mainly interpreted on the basis of the Jahn-Teller effect on [MoO 4 2- ] complex anions. We also observed that the photoluminescence intensity increased with increasing crystallite size.

  19. Photoluminescence of Mn+ doped GaAs

    NASA Astrophysics Data System (ADS)

    Zhou, Huiying; Qu, Shengchun; Liao, Shuzhi; Zhang, Fasheng; Liu, Junpeng; Wang, Zhanguo

    2010-10-01

    Photoluminescence is one of the most useful techniques to obtain information about optoelectronic properties and defect structures of materials. In this work, the room-temperature and low temperature photoluminescence of Mn-doped GaAs were investigated, respectively. Mn-doped GaAs structure materials were prepared by Mn+ ion implantation at room temperature into GaAs. The implanted samples were subsequently annealed at various temperatures under N2 atmosphere to recrystallize the samples and remove implant damage. A strong peak was found for the sample annealed at 950 °C for 5 s. Transitions near 0.989 eV (1254 nm), 1.155 eV (1074 nm) and 1.329 eV (933 nm) were identified and formation of these emissions was analyzed for all prepared samples. This structure material could have myriad applications, including information storage, magnet-optical properties and energy level engineering.

  20. Wide-band excited Y6(WMo)(0.5)O12:Eu red phosphor for white light emitting diode: structure evolution, photoluminescence properties, and energy transfer mechanisms involved.

    PubMed

    Li, Huaiyong; Noh, Hyeon Mi; Moon, Byung Kee; Choi, Byung Chun; Jeong, Jung Hyun; Jang, Kiwan; Lee, Ho Sueb; Yi, Soung Soo

    2013-10-07

    Y6(WMo)(0.5)O12 activated with Eu(3+) ions was investigated as a red-emitting conversion phosphor for white light emitting diodes (WLEDs). The phosphors were synthesized by calcining a citrate-complexation precursor at different temperatures. The photoluminescence properties of the phosphors and the energy transfer mechanisms involved were studied as a function of structure evolution. It was found that the host lattices were crystallized in a cubic or a hexagonal phase depending on the synthesis conditions. Although all the phosphors showed intensive red emission under an excitation of near-UV or blue light due to energy transfer from the host lattices to Eu(3+) ions, the photoluminescence spectra and temporal decay features were found to vary significantly with the structure and crystallinity of the host lattice. The mechanisms of the energy transfer from the host lattices to Eu(3+) ions and energy quenching among Eu(3+) ions were discussed on the basis of structure evolution of the host lattice. Phosphors calcined at 800 and 1300 °C were suggested to be promising candidates for blue and near-UV light excited WLEDs, respectively.