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Sample records for eu tm yb

  1. Facile synthesis and luminescence properties of Y2O3:Ln(3+) (Ln(3+) = Eu(3+), Tb(3+), Dy(3+), Sm(3+), Er(3+), Ho(3+), Tm(3+), Yb(3+)/Er(3+), Yb(3+)/Tm(3+), Yb(3+)/Ho(3+)) microspheres.

    PubMed

    Xu, Zhenhe; Zhao, Qian; Ren, Baoyi; You, Lixin; Sun, Yaguang

    2014-08-01

    Multicolor and monodisperse Y2O3:Ln(3+) (Ln(3+) = Eu(3+), Tb(3+), Dy(3+), Sm(3+), Er(3+), Ho(3+), Tm(3+), Yb(3+)/Er(3+), Yb(3+)/Ho(3+)) microspheres were prepared through a facile urea-assisted homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrum (EDS), Fourier transformed infrared (FT-IR), thermogravimetric analysis (TGA), photoluminescence (PL) and cathodoluminescence (CL) spectra were employed to characterize the samples. The XRD results reveal that the as-prepared spheres can be well indexed to cubic Y2O3 phase with high purity. The SEM and TEM images show the obtained Y2O3:Ln(3+) samples consist of regular nanospheres with the mean diameter of 350 nm. And the possible formation mechanism is also proposed. Upon ultraviolet and low-voltage electron beams excitation, Y2O3:Ln(3+) (Ln(3+) = Eu(3+), Tb(3+), Dy(3+), Sm(3+), Er(3+), Ho(3+), Tm(3+)) samples exhibit respective bright red (Eu(3+), (5)D0 --> (7)F2), green (Tb(3+), (5)D4 --> (7)F5), blue (Dy(3+), (4)F9/2 --> (6)H13/2), yellow (Sm(3+), (4)G5/2 --> (6)H7/2), green (Er(3+), (4)S3/2 --> (4)I15/2), green (Ho(3+), (5)S2 --> (5)I8), blue (Tm(3+), (1)D2 --> (3)F4) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Y2O3:Ln(3+) (Ln(3+) = Yb(3+)/Er(3+), Yb(3+)/Tm(3+) and Yb(3+)/Ho(3+)) exhibit characteristic up-conversion (UC) emissions of green (Er(3+), (2)H11/2, (4)S3/2, (2)H11/2 --> (4)I5/2), blue (Tm(3+), (1)G4 --> (3)H6) and green (Ho(3+), (5)F4, (5)S2 --> (5)I8), respectively. These merits of multicolor emissions in the visible region endow this kind of material with potential applications in the field of light display systems, lasers, and optoelectronic devices. PMID:25936002

  2. Large-scale synthesis of Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+}, Tb{sup 3+}, Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) microspheres and their photoluminescence properties

    SciTech Connect

    Gao, Yu; Gong, Jian; Fan, Miaomiao; Fang, Qinghong; Wang, Na; Han, Wenchi; Xu, Zhenhe

    2012-12-15

    Graphical abstract: In this work, multicolor and monodisperse Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+}, Tb{sup 3+}, Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) microspheres were prepared by a homogeneous precipitation method followed by a subsequent calcination process. Display Omitted Highlights: ? Lu{sub 2}O{sub 3}:Ln{sup 3+} microspheres were prepared by a precipitation followed by a calcination process. ? Lu{sub 2}O{sub 3}:Eu{sup 3+}/Tb{sup 3+} samples exhibit respective red or green emissions. ? Lu{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+}/Tm{sup 3+}/Ho{sup 3+} exhibit emissions of green, blue, yellow-green, respectively. ? These finding may find potential applications in bioanalysis and field emission displays. -- Abstract: In this work, multicolor and monodisperse Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+}, Tb{sup 3+}, Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) microspheres were prepared by a homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), Fourier transformed infrared (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra, and cathodoluminescence (CL) spectra were employed to characterize the samples. Upon ultraviolet and low-voltage electron beams excitation, Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+} and Tb{sup 3+}) samples exhibit respective bright red (Eu{sup 3+}, {sup 5}D{sub 0} ? {sup 7}F{sub 2}) and green (Tb{sup 3+}, {sup 5}D{sub 4} ? {sup 7}F{sub 5}) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) exhibit characteristic up-conversion (UC) emissions of green (Er{sup 3+}, {sup 4}S{sub 3/2}, {sup 2}H{sub 11/2} ? {sup 4}I{sub 15/2}), blue (Tm{sup 3+}, {sup 1}G{sub 4} ? {sup 3}H{sub 6}) and yellow-green (Ho{sup 3+}, {sup 5}F{sub 4}, {sup 5}S{sub 2} ? {sup 5}I{sub 8}), respectively. These finding may find potential applications in bioanalysis, optoelectronic and nanoscale devices, field emission displays, and so on.

  3. Controlled synthesis and luminescence properties of Ca0.5Y1-x(MoO4)2:xRE3+ (RE = Eu, Pr, Sm, Tb, Dy, Yb/Er, Yb/Tm, and Yb/Ho) phosphors by hydrothermal method versus pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Mahalingam, Venkatakrishnan; Thirumalai, Jagannathan; Krishnan, Rajagopalan; Chandramohan, Rathinam

    2016-01-01

    Herein, we report on rare-earth (RE) activated Ca0.5Y1-x(MoO4)2:xRE3+ (RE = Eu, Pr, Sm, Tb, Dy, Yb/Er, Yb/Ho, and Yb/Tm) phosphors synthesized using a surfactant-mediated hydrothermal route. Timedependent experiments were performed, and the morphological evolution of the phosphors was studied. From prepared powder samples of Ca0.5Y1-x(MoO4)2:xRE3+ (RE = Eu and Yb/Er), nano-sized thin phosphor films were grown using pulsed laser deposition (PLD). The surface topography of the as-grown thin phosphor films was analyzed. The asprepared phosphors were characterized by structural and optical studies. The powder phosphor exhibited bi pyramid-like micro-architectures. Structural studies indicated that Ca0.5Y1-x(MoO4)2 possesses the scheelite tetragonal crystal structure. The down-conversion luminescence of Ca0.5Y1-x(MoO4)2:xRE3+ (RE = Eu, Pr, Sm, Tb, and Dy) as powder phosphors and Eu3+ doped Ca0.5Y1-x(MoO4)2 thin phosphor film were studied. Upon irradiation with a 980 nm laser, the Ca0.5Y1-x(MoO4)2: xRE3+ (RE = Yb/Er, Yb/Ho, and Yb/Tm) powder phosphors and Ca0.5Y1-x(MoO4)2:xRE3+ (RE = Yb/Er) thin phosphor film showed intense up-converted visible emissions in green, yellow, and blue regions. The fluorescence decay time and color co-ordinates were determined for all synthesized phosphors. From the obtained results, the prepared powder and thin film phosphors are suggested to be suitable candidates for display and electro-luminescence applications. [Figure not available: see fulltext.

  4. Experimental study of the 4fn ? 4fn and 4fn ? 4fn-15d1 transitions of the lanthanide diiodides LnI2 (Ln=Nd, Sm, Eu, Dy, Tm, Yb).

    PubMed

    Rogers, E; Dorenbos, P; de Haas, J T M; van der Kolk, E

    2012-07-11

    The diffuse reflectance and photoluminescence (PL) spectra of NdI(2), SmI(2), EuI(2), DyI(2), TmI(2) and YbI(2) were measured between 225 and 12500nm in order to determine their 4f(n)?4f(n-1)5d(1) optical bandgaps. The results were compared with those obtained using an empirical model of the electronic structure of LnI(2). The results can be used to explain the lanthanide valency and crystalline structure changes of other lanthanide diiodides such as PrI(2). PMID:22713248

  5. Syntheses, structure and rare earth metal photoluminescence of new and known isostructural A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Ce, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) compounds

    SciTech Connect

    Mohitkar, Shrikant A.; Kalpana, G.; Vidyasagar, K.

    2011-04-15

    Nine new A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Ce, Pr, Eu, Tb, Ho, Er, Tm, Yb, Lu) compounds have been synthesized by solid-state reactions. They are isostructural with six reported analogues of yttrium and other lanthanides and the monoclinic unit cell parameters of all fifteen of them vary linearly with the size of A{sup 3+} ion. Single crystal X-ray structures of eight A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Ce, Pr, Eu, Gd, Tb, Ho, Er, Tm) compounds have been determined. Neat A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Pr, Sm, Eu, Tb, Dy, Ho, Er, Tm) compounds exhibit characteristic rare earth metal photoluminescence. -- Graphical abstract: Among the fifteen isostructural A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=rare earth metal) molybdoantimonites, eight (A=Pr, Sm, Eu, Tb, Dy, Ho, Er, Tm) compounds exhibit neat characteristic lanthanide photoluminescence in the 200-800 nm range at room temperature. Display Omitted Research highlights: {yields} Syntheses of nine new A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Ce, Pr, Eu, Tb, Ho, Er, Tm, Yb, Lu) compounds. {yields} X-ray structures of eight A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Ce, Pr, Eu, Gd, Tb, Ho, Er, Tm) compounds. {yields} Photoluminescence of neat A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Pr, Sm, Eu, Tb, Dy, Ho, Er, Tm) compounds.

  6. Investigation of upconversion and downconversion fluorescence emissions from β-NaLn1F{sub 4}:Yb{sup 3+}, Ln2{sup 3+} (Ln1 = Y, Lu; Ln2 = Er, Ho, Tm, Eu) hexagonal disk system

    SciTech Connect

    He, Enjie; Zheng, Hairong; Gao, Wei; Tu, Yinxun; Lu, Ying; Li, Guian

    2013-09-01

    Graphical abstract: Well-defined β-NaLn1F4:Yb{sup 3+}, Ln2{sup 3+} (Ln1 = Y, Lu; Ln2 = Er, Ho, Tm, Eu) hexagonal thin disks with a simple and user-friendly hydrothermal approach by using sodium citrate as a shape modifier. Much stronger UC and DC fluorescence emissions were observed in NaLuF{sub 4}-based hexagonal disks than that for NaYF{sub 4} counterparts. The strength of hypersensitive transitions is mainly attributed to the decrease of local symmetry Ln-F bond lengths in β-NaLuF{sub 4}. It will show a great potential in improving near-infrared conversion efficiency of silicon solar cells and removable sub-micro luminescent platforms. - Highlights: • Regular hexagonal disks (NaLnF{sub 4}) were synthesized by a simple hydrothermal method. • Much stronger UC and DC emissions were observed in NaLuF{sub 4}-based disks. • Stronger fluorescence emissions in NaLuF{sub 4}-based disks were explained reasonably. • NaLuF{sub 4}-based disks can act as a removable luminescent platform for nano-assembly. • NaLuF{sub 4}-based disks can be applied in improving efficiency of solar cells. - Abstract: Uniform hexagonal β-NaLn1F{sub 4}:Yb{sup 3+}, Ln2{sup 3+} (Ln1 = Y, Lu; Ln2 = Er, Ho, Tm, Eu) disks were synthesized with hydrothermal method in which the sodium citrate was used as a shape modifier. The experimental observation indicated that both upconversion and downconversion fluorescence emissions were significantly stronger in β-NaLuF{sub 4} than that for β-NaYF{sub 4}. It was found that the stronger hypersensitive transitions were mainly due to the increase of J–O parameter (Ω{sub 2}) in β-NaLuF{sub 4} host, while the stronger insensitive transitions were mainly caused by the stronger overlap of electron cloud that was induced by the decrease of Ln-F bond lengths. Additionally, the larger absorption strength in the near-infrared region is another important factor for the stronger fluorescence emissions. The current research has a great potential in improving near-infrared conversion efficiency of silicon solar cells.

  7. Synthesis and upconversion luminescence in highly crystalline YOF:Yb3+/Er3+ and Yb3+/Tm3+ microboxes

    NASA Astrophysics Data System (ADS)

    Ding, Mingye; Lu, Chunhua; Cao, Linhai; Ni, Yaru; Xu, Zhongzi

    2013-04-01

    Highly crystalline YOF:Ln3+ (Ln = Yb, Er, Tm) microboxes were successfully synthesized for the first time by using a mixed NaNO3-KNO3 flux cooling method at a holding temperature of 600 C for 2 h in air. The results indicated that the as-obtained products belonged to tetragonal system and exhibited microboxes morphology with side lengths of 0.5-2 ?m. The upconversion luminescence properties of as-prepared YOF:Yb3+/Er3+ and YOF:Yb3+/Tm3+ were investigated in detail. Under 980 nm laser diode (LD) excitation, the emission intensity and the corresponding luminescence colors of YOF:Yb3+/Er3+ and YOF:Yb3+/Tm3+ could be precisely adjusted by changing the doping concentration of Yb3+ ions. Furthermore, the paper also offers a new alternative in synthesizing such materials and opens the possibility to meet the increasing commercial demand.

  8. Spectroscopic and laser characterization of Yb,Tm:KLu(WO4)2 crystal

    NASA Astrophysics Data System (ADS)

    Loiko, P. A.; Serres, J. M.; Mateos, X.; Demesh, M. P.; Yasukevich, A. S.; Yumashev, K. V.; Petrov, V.; Griebner, U.; Aguil, M.; Daz, F.

    2016-01-01

    We report on a comprehensive spectroscopic and laser characterization of monoclinic Yb,Tm:KLu(WO4)2 crystals. Stimulated-emission cross-section spectra corresponding to the 3F4 ? 3H6 transition of Tm3+ ions are determined. The radiative lifetime of the 3F4 state of Tm3+ ions is 0.82 ms. The maximum Yb3+ ? Tm3+ energy transfer efficiency is 83.9% for 5 at.% Yb - 8 at.% Tm doping. The fractional heat loading for Yb,Tm:KLu(WO4)2 is 0.45 0.05. Using a hemispherical cavity and 5 at.% Yb - 6 at.% Tm doped crystal, a maximum CW power of 227 mW is achieved at 1.983-2.011 ?m with a maximum slope efficiency ? = 14%. In the microchip laser set-up, the highest slope efficiency is 20% for a 5 at.% Yb- 8 at.% Tm doped crystal with a maximum output power of 201 mW at 1.99-2.007 ?m. Operation of Yb,Tm:KLu(WO4)2 as a vibronic laser emitting at 2.081-2.093 ?m is also demonstrated.

  9. Upconversion emission properties of CeO2: Tm3+, Yb3+ inverse opal photonic crystals

    NASA Astrophysics Data System (ADS)

    Cheng, Gong; Wu, Hangjun; Yang, Zhengwen; Liao, Jiayan; Lai, Shenfeng; Qiu, Jianbei; Song, Zhiguo

    2014-10-01

    The ordered and disordered templates were assembled by vertical deposition of polystyrene microspheres. The CeO2: Tm3+, Yb3+ precursor solution was used to infiltrate into the voids of the ordered and disordered templates, respectively. Then the ordered and disordered templates were calcined at 950C in an air furnace, and the CeO2: Tm3+, Yb3+ inverse opals were obtained. The upconversion emissions from CeO2: Tm3+, Yb3+ inverse opals were suppressed due to the photon trapping caused by Bragg reflection of lattice planes when the upconversion emission band was in the range of the photonic band gaps in the inverse opals.

  10. Possible undercompensation effect in the Kondo insulator (Yb,Tm)B12

    NASA Astrophysics Data System (ADS)

    Alekseev, P. A.; Nemkovski, K. S.; Mignot, J.-M.; Clementyev, E. S.; Ivanov, A. S.; Rols, S.; Bewley, R. I.; Filipov, V. B.; Shitsevalova, N. Yu.

    2014-03-01

    The effects of Tm substitution on the dynamical magnetic response of Yb1-xTmxB12 (x=0, 0.08, 0.15, and 0.75) and Lu0.92Tm0.08B12 compounds have been studied using time-of-flight inelastic neutron scattering. Major changes were observed in the spectral structure and temperature evolution of the Yb contribution to the inelastic response for a rather low content of magnetic Tm ions. A sizable influence of the RB12 host (YbB12, as compared to LuB12 or pure TmB12) on the crystal-field splitting of the Tm3+ ion is also reported. The results point to a specific effect of impurities carrying a magnetic moment (Tm, as compared to Lu or Zr) in a Kondo insulator, which is thought to reflect the "undercompensation" of Yb magnetic moments, originally Kondo screened in pure YbB12. A parallel is made with the strong effect of Tm substitution on the temperature dependence of the Seebeck coefficient in Yb1-xTmxB12, which was reported previously.

  11. Infrared luminescence of Tm{sup 3+}/Yb{sup 3+} codoped lanthanum aluminum germanate glasses

    SciTech Connect

    Zhang Qiang; Zhang Guang; Chen Guorong; Qiu Jianrong; Chen Danping

    2010-01-15

    Tm{sup 3+} doped and Tm{sup 3+}/Yb{sup 3+} codoped lanthanum aluminum germanate (LAG) glasses are prepared by melt-quenching method and characterized optically. Based on the measurement of absorption spectrum, Judd-Ofelt intensity parameters ({Omega}{sub 2},{Omega}{sub 4},{Omega}{sub 6}) are calculated. The radiation emission rates, branching ratios, and lifetimes of Tm{sup 3+} are calculated to evaluate the spectroscopic properties of Tm{sup 3+} in LAG glass. The infrared emission properties of the samples are investigated and the results show that the 1.8 {mu}m emission can be greatly enhanced by adding proper amount of Yb{sup 3+} under the excitation of 980 nm. The energy transfer processes of Yb{sup 3+}-Yb{sup 3+} and Yb{sup 3+}-Tm{sup 3+} are analyzed, and the results show that Yb{sup 3+} ions can transfer their energy to Tm{sup 3+} ions with high efficiency and large energy transfer coefficient.

  12. Evidence of Tm impact in low-photodarkening Yb-doped fibers.

    PubMed

    Jetschke, Sylvia; Unger, Sonja; Schwuchow, Anka; Leich, Martin; Fiebrandt, Julia; Jger, Matthias; Kirchhof, Johannes

    2013-03-25

    In contrast to Yb/Al-doped fibers, the influence of very low Tm(2)O(3) concentrations (? 0.1 mol-ppm) on photodarkening (PD) is clearly detectable in Yb/P-doped fibers that are known to show little degradation effects. For Tm(2)O(3) additions of more than 50 mol-ppm, the measured PD loss is even similar to Yb/Al-doped fibers with comparable rare earth concentrations. Our work reveals the risk of color center generation by pumping at wavelengths of 915 nm or 976 nm even in Al-free Yb-doped fibers and emphasizes the importance of high purity of raw materials for the preparation of Yb laser fibers with expected very low PD. PMID:23546142

  13. Yb3+ sensitized Tm3+ upconversion in tellurite lead oxide glass.

    PubMed

    Mohanty, Deepak Kumar; Rai, Vineet Kumar; Dwivedi, Y

    2012-04-01

    Triply ionized thulium/thulium--ytterbium doped/codoped TeO2-Pb3O4 (TPO) glasses have been fabricated by classical quenching method. The upconversion emission spectra in the Tm3+/Tm3+-Yb3+ doped/codoped glasses upon excitation with a diode laser lasing at ?980 nm has been studied. Effect of the addition of the Yb3+ on the upconversion emission intensity in the visible and near infrared regions of the Tm3+ doped in TPO glass has been studied and the processes involved explored. PMID:22265952

  14. Novel Y2O3-codoped Yb/Tm-doped picosecond fiber laser

    NASA Astrophysics Data System (ADS)

    Dvoyrin, Vladislav V.; Klimentov, Dmitry; Halder, Arindam; Paul, Mukul C.; Pal, Mrinmay; Bhadra, Shyamal K.; Kir'yanov, Alexander V.; Sorokina, Irina T.

    2013-02-01

    We demonstrate the novel picosecond mode-locked Y2O3-codoped Yb/Tm-doped fiber lasers, operating at 1950 nm and producing pulses of up to 1 nJ energy, using a SESAM and an Er-doped pump fiber laser operating at the wavelength 1590 nm or a semiconductor pump laser operating at the wavelength of 1560 nm. We also report on the spectroscopic characterization of these new fibers with various compositions, identifying the optimum one for the maximum Yb/Tm energy transfer, the latter increasing with the increase of the Y concentration. The observed energy transfer between Yb and Tm makes this laser promising also for direct diode-pumping with most advanced and low cost 975 nm diodes, making this laser attractive for compact low cost picosecond Tm-doped fiber laser systems.

  15. [Preparation and up-conversion luminescence properties of Yb3+/Tm3+ co-doped Sb2O4 powder].

    PubMed

    Li, Rui-Qin; Qiu, Jian-Bei; Yang, Zheng-Wen; Liao, Jia-Yan; Wu, Hang-Jun; Lai, Shen-Feng; Song, Zhi-Guo; Yang, Yong; Zhou, Da-Cheng; Wang, Rong-Fei

    2014-03-01

    The Sb2O4:Yb3+, Tm3+ up-conversion luminescence powder with excellent physical, chemical stability and relative low phonon energy was synthesized by the high temperature solid-state reaction and its up-conversion luminescence property was investigated. Under the 980 nm excitation, infrared and blue up-conversion emissions centered at 800 and 480 nm were observed, which were assigned to the 1G4-->3H6 and 3H4-->3 He transitions of Tm2+, respectively. The influence of Yb3+ and Tm3+ concentration on the up-conversion emission property was also obtained. The up-conversion luminescence increases with increasing of Yb3+ and Tm3+ concentration. Additionally, the up-conversion luminescence mechanism was discussed based on the dependence of Tm3+ up-conversion luminescence on pump power. It is interesting that two photon excitation processes for blue and infrared emission were observed in the Sb2O04: Yb3+, Tm3+ powder under a 980 nm excitation. Based on the energy level diagram of Tma3 and Yb2+ ions, we think that two photons blue emission is contributed to the cooperation energy transfer between Tm"+ and Yb3+ ions. We believe that the Sbz04 : Yb3 , Tm2+ up-conversion luminescence powder will have potential application for new optical devices in up-conversion color displays, sensors, detection of infrared radiation, and lasers. PMID:25208379

  16. Upconversion emission in antimony-germanate double-clad optical fiber co-doped with Yb3+/Tm3+ ions

    NASA Astrophysics Data System (ADS)

    Kochanowicz, M.; Dorosz, D.; Zmojda, J.; Miluski, P.; Dorosz, J.; Pisarska, J.; Pisarski, W. A.

    2015-03-01

    In the paper upconversion luminescence properties in Yb3+/Tm3+ co-doped antimony-germanate glass and double-clad optical fiber were studied. The concentration of lanthanides, which has shown the highest upconversion emission intensity at 478 nm (1G4 ? 3H6) and 650 nm (1G4 ? 3F4), is 1Yb2O3/0.1Tm2O3 (mol%) as a result of exciting with a laser diode (976 nm). The lifetime of 2F5/2 (Yb3+) level decreases from 781 ?s to 71 ?s in the presence of Tm3+ 0.1-0.75 mol% respectively. Luminescence decay curve of glass co-doped with 1Yb2O3/0.75Tm2O3 suggests donor-donor fast migration followed by Tm3+ ? Yb3+ energy transfer. Glass characterized by highest intensity of upconversion luminescence (1Yb2O3/0.1Tm2O3 mol%) was used as core of double-clad optical fiber made by modified rod-in-tube method. Mechanisms influencing differences in upconversion amplified spontaneous emission of the fabricated optical fiber and bulk glass were discussed. Reabsorption of the amplified spontaneous emission signal along the fibre resulting from Tm3+:3H6 ? 1G4, transition was observed.

  17. Multicolor upconversion emission and energy transfer mechanism in Er3+/Tm3+/Yb3+ codoped tellurite glasses

    NASA Astrophysics Data System (ADS)

    Peng, Shengxi; Yang, Fengjing; Wu, Libo; Qi, Yawei; Zheng, Shichao; Yin, Dandan; Wang, Xunsi; Zhou, Yaxun

    2014-11-01

    A novel Er3+, Tm3+ and Yb3+ codoped tellurite glasses with composition of TeO2-Bi2O3-ZnO-Na2O was prepared by conventional melt-quenching technique to realize the multicolor upconversion (UC) emissions. The absorption spectrum, UC emission spectrum, Raman spectrum, X-ray diffraction (XRD) and differential scanning calorimeter (DSC) curves were measured to characterize the prepared glass samples. Under the excitation of 980 nm laser diode (LD), bright multicolor luminescence composed of red, green and/or blue UC emissions corresponding to the transitions 4F9/2?4I15/2, 2H11/2(4S3/2)?4I15/2 of Er3+ and 1G4?3H6 of Tm3+ were observed in the Er3+/Yb3+, Tm3+/Yb3+ and Er3+/Tm3+/Yb3+ codoped glass samples, which were mainly attributed to the successive energy transfers from Yb3+ to Er3+ and Tm3+, respectively. The energy transfer mechanisms from the Yb3+:2F5/2 level to Er3+:4I11/2 and Tm3+:3H5 levels were further investigated by quantitatively calculating the energy transfer micro-parameters and phonon contribution ratios. Meanwhile, the difference (?T=Tx-Tg) between the glass crystallization onset temperature (Tx) and the transition temperature (Tg) which increase slightly with rare-earth (RE) doped concentration, was larger than 140 C for all glass samples. Furthermore, the amorphous nature of glass structure was demonstrated by the measured XRD curves. The excellent thermal stability and multicolor luminescent characteristic indicate that the present investigated Er3+/Tm3+/Yb3+ codoped tellurite glasses could be used in the fields of solid state multicolor displays and other luminescent devices.

  18. Synthesis, persistent luminescence, and thermoluminescence properties of yellow Sr3SiO5:Eu2+,RE3+ (RE=Ce, Nd, Dy, Ho, Er, Tm, Yb) and orange-red Sr(3-x)Ba(x)SiO5:Eu2+, Dy3+ phosphor.

    PubMed

    Li, Ye; Li, Baohong; Ni, Chenchen; Yuan, Shuxia; Wang, Jing; Tang, Qiang; Su, Qiang

    2014-02-01

    Sunlight-excitable orange or red persistent oxide phosphors with excellent performance are still in great need. Herein, an intense orange-red Sr3-xBaxSiO5:Eu(2+),Dy(3+) persistent luminescence phosphor was successfully developed by a two-step design strategy. The XRD patterns, photoluminescence excitation and emission spectra, and the thermoluminescence spectra were investigated in detail. By adding non-equivalent trivalent rare earth co-dopants to introduce foreign trapping centers, the persistent luminescence performance of Eu(2+) in Sr3SiO5 was significantly modified. The yellow persistent emission intensity of Eu(2+) was greatly enhanced by a factor of 4.5 in Sr3SiO5:Eu(2+),Nd(3+) compared with the previously reported Sr3SiO5:Eu(2+), Dy(3+). Furthermore, Sr ions were replaced with equivalent Ba to give Sr3-xBaxSiO5 :Eu(2+),Dy(3+) phosphor, which shows yellow-to-orange-red tunable persistent emissions from ?=570 to 591?nm as x is increased from 0 to 0.6. Additionally, the persistent emission intensity of Eu(2+) is significantly improved by a factor of 2.7 in Sr3-xBaxSiO5 :Eu(2+),Dy(3+) (x=0.2) compared with Sr3SiO5 :Eu(2+),Dy(3+). A possible mechanism for enhanced and tunable persistent luminescence behavior of Eu(2+) in Sr3-xBaxSiO5:Eu(2+),RE(3+) (RE=rare earth) is also proposed and discussed. PMID:24203579

  19. Eu3+, Yb3+ and Eu3+-Yb3+ complexes with salicylic acid and 1,10-phenanthroline: synthesis, photoluminescent properties and energy transfer.

    PubMed

    Sharma, Garima; Narula, Anudeep Kumar

    2015-03-01

    This paper reports the synthesis of mononuclear Eu(3+), Yb(3+) and binuclear Eu(3+)-Yb(3+) complexes by solution technique, maintaining the stoichiometric ratios of salicylic acid (sal) and 1,10-phenanthroline (phen) as ligands and their structural, optical and morphological properties were demonstrated. The FTIR absorption spectra indicates that sal and phen are coordinated to the rare earth ion through the chemical bonds formed between oxygen and nitrogen atoms of the ligands and rare earth ion. The UV-vis absorption spectra of the complexes reflect the absorption spectra of the ligands and there is no significant change in the wavelength and band profiles between the spectra of the ligands and that of complexes except a slight red shift. The photoluminescent emission spectra of the complexes in visible and near-infrared (NIR) region was recorded and indicated the emission quenching in complex (2) due to the energy transfer from Eu(3+) ion to Yb(3+) ion. The morphological properties of the complexes as characterized by SEM revealed different morphologies of mononuclear and binuclear complexes. PMID:25653135

  20. Trapping processes in CaS:Eu{sup 2+},Tm{sup 3+}

    SciTech Connect

    Jia, Dongdong; Jia, Weiyi; Evans, D. R.; Dennis, W. M.; Liu, Huimin; Zhu, Jing; Yen, W. M.

    2000-09-15

    CaS:Eu{sup 2+},Tm{sup 3+} is a persistent red phosphor. Thermoluminescence was measured under different excitation and thermal treatment conditions. The results reveal that the charge defects, created by substituting Tm{sup 3+} for Ca{sup 2+}, serve as hole traps for the afterglow at room temperature. Tm{sup 3+} plays the role of deep electron trapping centers, capturing electrons either through the conduction band or directly from the excited Eu{sup 2+} ions. These two processes, in which two different sites of Tm{sup 3+} are involved, correspond to two traps with different depths. (c) 2000 American Institute of Physics.

  1. Up-conversion luminescence properties and energy transfer of Tm3+/Yb3+ co-doped BaLa2ZnO5

    NASA Astrophysics Data System (ADS)

    Xie, Jing; Mei, Lefu; Deng, Junru; Liu, Haikun; Ma, Bin; Guan, Ming; Liao, Libing; Lv, Guocheng

    2015-11-01

    Tm3+/Yb3+ co-doped BaLa2ZnO5 up-conversion (UC) phosphors were successfully synthesized by high temperature solid-state reaction method. The X-ray diffraction (XRD) results show that synthesized phosphor co-doped with 0.75% Tm/10% Yb has the optimum pure phase of BaLa2ZnO5 among different co-doping concentrations. The structure of BaLa2ZnO5:0.75% Tm/10% Yb phosphor was refined by the Rietveld method and results show the decreased unit cell parameters and cell volume after doping Tm3+/Yb3+, indicating that Tm3+/Yb3+ have successfully replaced La3+. Under excitation at 980 nm, Tm3+/Yb3+ co-doped BaLa2ZnO5 phosphors present bright blue emission near 478 nm generated by the 1G4→3H6 transition and weak red emissions around 653 nm and 692 nm generated by the 1G4→3F4 and 3F3→3H6 transitions of Tm3+, respectively. The UC luminescence properties of BaLa2ZnO5 phosphors co-doped with different Tm3+/Yb3+ concentrations were investigated, and the related UC mechanisms of Tm3+/Yb3+ co-doped BaLa2ZnO5 depending on pump power were studied in detail.

  2. White Lighting Upconversion in Tm3+/Ho3+/Yb3+ Co-Doped CaWO4

    NASA Astrophysics Data System (ADS)

    Chung, Jun Ho; Yeop Lee, Sang; Shim, Kwang Bo; Ryu, Jeong Ho

    2012-05-01

    Controllable white upconversion (UC) luminescence was obtained from Tm3+/Ho3+/Yb3+-codoped CaWO4. Under the excitation of a 980 nm single wavelength laser diode, the Tm3+/Ho3+/Yb3+-codoped CaWO4 exhibited bright white UC luminescence composed of blue emission from Tm3+ and green and red emissions from Ho3+ visible to the naked eye. The intensity ratios of green, red, and blue UC emissions varied with Tm3+/Ho3+ concentrations, which can control white UC emission ranging from the cool to the warm region. Various white UC colors can be easily changed by adjusting the Tm3+/Ho3+ concentrations in the CaWO4 matrix.

  3. Growth, thermal, and spectroscopic properties of a Cr,Yb,Ho,Eu:YAP laser crystal

    NASA Astrophysics Data System (ADS)

    Zhang, Huili; Sun, Dunlu; Luo, Jianqiao; Chen, Jiakang; Yang, Huajun; Xiao, Jingzhong; Zhang, Qingli; Yin, Shaotang

    2014-06-01

    A new Cr,Yb,Ho,Eu:YAlO3(YAP) laser crystal was successfully grown by the Czochralski method. Thermal properties were investigated along the a, b, and c crystalline axes. Results indicate that the Cr,Yb,Ho,Eu:YAP crystal has large anisotropic thermal expansion and that the suitable crystal growth direction is the b axis. The Debye temperatures were fitted, and the lattice vibration frequencies were calculated. Spectroscopic measurements show that Cr3+ and Yb3+ can be used as sensitizers of Ho3+ ions, and Eu3+ ions can play a role of the deactivator in decreasing the lifetime of laser lower level 5I7 from 8.69 ms to 1.89 ms, which is beneficial in decreasing laser threshold and increasing laser conversion efficiency. All these findings suggest that the Cr,Yb,Ho,Eu:YAP crystal is a new potential candidate for realizing 2.8-3 ?m laser output pumped by a 970 nm laser diode or pulsed flash lamp.

  4. Visible to near-infrared downconversion in Tm3+/Yb3+ co-doped chalcohalide glasses for solar spectra converter

    NASA Astrophysics Data System (ADS)

    Huang, Fei; Chen, Liyan; Han, Ying; Tang, Junzhou; Nie, Qiuhua; Zhang, Peiqing; Xu, Yinsheng

    2015-07-01

    Near-infrared downconversion which can be used to improve the utilization of solar spectral has drawn much attention. In this work, chalcohalide glasses with compositions of 50GeS2-25Ga2S3-25CsCl (in mol.%): 0.1 wt.% Tm2 S3 - x wt.% Yb2S3 (x = 0, 0.1, 0.2, 0.3) were synthesized by vacuumed melt-quenching method. Absorption spectra, emission spectra, excitation spectra, and decay measurements were performed to prove the occurrence of cooperative energy transfer from the 1G4 level of Tm3+ ions to two Yb3+ ions. Quantum efficiency depends on Yb3+ concentration is calculated, and the highest is 114.1%. The photon energy of Yb3+ emission around 1 ?m well matched with the operation band gap of the crystalline Si, so the glasses could potentially be applied in Si-based solar cell.

  5. Specific features of magnetoresistance during the antiferromagnetparamagnet transition in Tm1 - x Yb x B12

    NASA Astrophysics Data System (ADS)

    Sluchanko, N. E.; Azarevich, A. N.; Bogach, A. V.; Glushkov, V. V.; Demishev, S. V.; Levchenko, A. V.; Filippov, V. B.; Shitsevalova, N. Yu.

    2013-05-01

    The transverse magnetoresistance ??/?( H, T) of Tm1 - x Yb x B12 single crystals is studied in the ytterbium concentration range corresponding to the antiferromagnet-paramagnet transition in a magnetic field up to 80 kOe at low temperatures. A magnetic H- T phase diagram is constructed for the antiferromagnetic state of substitutional Tm1 - x Yb x B12 solid solutions with x ? 0.1. The contributions to the magnetoresistance in the antiferromagnetic and paramagnetic phases of the dodecaborides under study are separated. Along with negative quadratic magnetoresistance -??/? ? H 2, the magnetically ordered phase of these compounds is found to have component ??/? ? H that linearly changes in a magnetic field. The negative contribution to the magnetoresistance of Tm1 - x Yb x B12 is analyzed in terms of the Yosida model for a local magnetic susceptibility.

  6. Effect of Metal Coating on NaYF4:Yb3+,Tm 3+ Upconversion Nanoparticles

    NASA Astrophysics Data System (ADS)

    Alazemi, Abdulrahman

    Upconversion is the process in which two or more low-energy photons are absorbed and emitted as one high-energy photon. This research reports on the effect of layer-by-layer polyelectrolytes and silver coating on hexagonal NaYF4:Yb3+,Tm3+ in an attempt to enhance the upconversion intensity. The synthesized upconversion nanoparticles were separated into two, 140 nm and a mixture of two populations, 250 nm and 25 nm. The former case observed enhancement, when silver coated on the upconversion nanoparticles using hydroquinone as the reducing agent, with no layers and with several layers (three, four and five) of polyelectrolytes. The size (140 nm) and morphology of the hexagonal NaYF4:Yb 3+,Tm3+ were similar. The enhancement was confirmed when sodium cyanide was added to remove the silver coating from the sample resulting in a decrease in the upconversion intensity. Quenching was observed in the latter case, when silver coating was unsuccessful and that there are two populations of upconversion nanoparticles (large 250 nm and small 25 nm).

  7. White upconversion emission in Li+/Yb3+/Tm3+/Er3+-doped Gd6MoO12 phosphors

    NASA Astrophysics Data System (ADS)

    Sun, Jiayue; Xue, Bing; Du, Haiyan

    2013-07-01

    The Yb3+/Er3+/Tm3+-doped Gd6MoO12 phosphors and Li+/Yb3+/Er3+/Tm3+-doped Gd6MoO12 phosphors were synthesized by the high-temperature solid-state method. Under 980 nm laser diode excitation, the Gd6MoO12:Li+/Yb3+/Er3+/Tm3+ phosphors show the white upconversion (UC) emission at the pump power of 200 mW/cm2, which is composed of the blue (1G4?3H6 of Tm3+), green (2H11/2, 4S3/2?4I15/2 of Er3+), and red (4F9/2?4I15/2 of Er3+) UC emissions. The calculated CIE color coordinates of Gd6MoO12:Tm3+/Er3+/Yb3+ phosphors changed from blue area to white area after the Li+ ion doping. Then, the effect of Li+ ions mixing on the emission was analysed. The relative UC mechanisms and properties were also investigated and proposed based on their spectral. The additional mixed Li+ ions enhanced the red and green upconversion emission largely in this phosphor and then formed the white UC emission, which indicated that the Li+ is a promising dopant for tuning white light luminescence in some case.

  8. Lasing in a Tm : Yb3Al5O12 crystal pumped at 1.678 ?m

    NASA Astrophysics Data System (ADS)

    Zavartsev, Yu D.; Zagumennyi, A. I.; Kalachev, Yu L.; Kutovoi, S. A.; Mikhailov, V. A.; Shcherbakov, I. A.

    2014-10-01

    The Yb3Al5O12 (YbAG) crystal is proposed as a matrix of Tm3+-doped laser elements for two-micron lasers. A Tm : YbAG crystal of high optical quality is grown by the Czochralski method and its spectral and luminescent characteristics are studied. The luminescence decay time for the upper laser level 3F4 is measured to be 4.7 ms. Lasing in this crystal pumped by a 1.678-?m fibre laser is obtained at a wavelength of 2.02 ?m for the first time. The total and slope efficiencies of the laser at room temperature and an output power up to 330 mW reach 33% and 41%, respectively.

  9. Quantum sized Ag nanocluster assisted fluorescence enhancement in Tm3+-Yb3+ doped optical fiber beyond plasmonics

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, Rik; Haldar, Arindam; Paul, Mukul C.; Das, Shyamal; Bhadra, Shyamal K.

    2015-12-01

    We report a process for enhancing fluorescence emission from conventional rare earth ions in optical fiber by metal nanocluster (MNC) in nonresonant indirect pumping. The process is completely different from formal metal enhanced fluorescence phenomenon as the MNCs are too small in size to support localized surface plasmon and the excitation wavelength is far from plasmon resonance frequency. We used an established theory of two coupled oscillators to explain the simultaneous enhancement of Ytterbium (Yb3+) and Thulium (Tm3+) emission by silver (Ag) NCs under nonresonant pumping in optical fiber. The fiber is pumped with a 980 nm fiber pigtailed laser diode with input power of 20-100 mW to excite the Yb3+. Four times enhancement of Yb3+ emission of 900-1100 nm and Tm3+ upconversion emission around 474 nm, 650 nm, and 790 nm is observed in the fiber with Ag NCs.

  10. White light upconversion emission in Yb3+/ Er3+/ Tm3+ codoped oxy-fluoride lithium tungsten tellurite glass ceramics

    NASA Astrophysics Data System (ADS)

    Ansari, Ghizal F.; Mahajan, S. K.

    2012-02-01

    The bright white upconversion emission ( tri-colour UC) is generated in Er/Tm/Yb tri -doped oxy-fluoride lithium tungsten tellurite (TWLOF)glass ceramics containing crystalline phase LiYbF4 under the excitation of 980nm laser diode. The most appropriate combination of rare-earth ions (2mol% YbF3 1mol% ErF3 and 1mol%TmF3 )of glass ceramic sample has been determined to tune the primary colour (RGB and generate white light emission. By varying the pump power, intense and weak blue (487nm, 437nm), green (525nm and 545nm) and red (662nm) emission are simultaneously observed at room temperature. The dependence of upconversion emission intensity suggest that a theephoton process is responsible for the blue emission of Tm3+ ions and red emission due to both Tm3+ and Er3+ ions , while green emission originated from two photon processes in Er3+ ions. Also tri colour upconvesion and energy transfer in this glass ceramics sample were studied under 808nm laser diode excitation. The Upconversion mechanisms and Tm3+ ions plays role of both emitter and activator (transfer energy to Er) were discussed.

  11. Size dependent ultraviolet upconversion in single YF3:Yb3+/Tm3+ particles.

    PubMed

    Liu, Zhenyu; Zheng, Kezhi; Zhao, Dan; Liu, Ning; Qin, Weiping

    2011-11-01

    Yb3+-Tm3+ codoped YF3 bulk material was synthesized through a facile high-temperature calcinations method. By grinding and selecting, the particles with different desired sizes in microns were obtained. Under 980 nm excitation, optical upconversion (UC) from near-infrared (NIR) to ultraviolet (UV) was studied for each group of particles for the effect of their size on UC. Comparing with the bulk sample, the micro-size particles exhibited strong ability for NIR-to-UV UC. With the particle size decreasing from 800 microm to 20 microm, their UV emission intensities increased rapidly. Two possible mechanisms were proposed and discussed for clarifying the small size effect (SSE). PMID:22413252

  12. Solvent extraction behaviour of calixarene-type cyclophanes towards trivalent La, Nd, Eu, Er and Yb

    SciTech Connect

    Ludwig, R.; Inoue, Katsutoshi; Yamato, Takehiko )

    1993-04-01

    In this paper we describe the solvent extraction behaviour of three calixarene-type cyclophanes towards trivalent lanthanides Ln[sup 3+] (Ln = La, Nd, Eu, Er and Yb). By using p-tert-butylcalix/6/arene hexacarboxylic acid (L1), the lanthanides were extracted from the aqueous phase at pH 2 to 3.5 into chloroform according to a cation exchange mechanism as 1:2 metal:ligand complexes. The extractability is: Nd, Eu > La > Er > Yb. In the presence of excess Na[sup +] in the aqueous phase, this order was not changed but the lanthanides were extracted as 1:1 complexes at low extractant concentration and their extractability decreased. The use of p-tert-butylcalix/4/arene tetracarboxylic acid (L2) with a smaller cavity size dissolved in chloroform or toluene results in lower distribution coefficients, D[sub Ln], compared with L1. The extraction constants of the 1:2 metal:extractant complexes for the water-toluene system follow the order Eu > Nd > Yb > Er > La. Upon addition of excess Na[sup +], both extractability and selectivity increased. The extraction behaviour of a third cyclophane (L3) with a cavity size similar to that of L1 containing four carboxylic acid groups was different from that of L1 with respect to extractability and order of extraction of the lanthanides. 21 refs., 12 figs.

  13. Thermal decomposition assisted synthesis and upconversion property of Fe3O4@YPO4:Tm/Yb hybrid nano-composite phosphor

    NASA Astrophysics Data System (ADS)

    Tiwari, S. P.; Kumar, K.; Rai, V. K.

    2015-06-01

    Hybrid nano-composite phosphor has been successfully synthesized through thermal decomposition method. The dual phase of samples assigned by XRD analysis shows the formation of nano-composite with crystallite size 20 nm and 12 nm for YPO4: Tm/Yb and Fe3O4@YPO4:Tm/Yb respectively. The FESEM images show the spherical shape and non agglomerated formation of nanoparticles. Three bands in upconversion emission mode were found in intense blue at 472 nm, red at 662 nm and NIR at 798 nm regions corresponding to1G4 ? 3H6, 1G4 ? 3F4 and 3H4 ? 3H6 transition states respectively. The lifetime for1G4 ? 3H6 level is found 1150 microsecond and 1400 microsecond for YPO4: Tm/Yb and Fe3O4@YPO4:Tm/Yb samples respectively.

  14. Mechanochemical preparation of nanocrystalline NaYF4:Gd3+/Yb3+/Tm3+: An efficient upconversion phosphor

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Riesen, Hans

    2015-11-01

    We report on a mechanochemical preparation route for NaYF4:Gd3+/Yb3+/Tm3+ nanoparticles by ball-milling NaF, YF3, GdF3, YbF3 and TmF3 at room temperature. An analysis by XRD and TEM demonstrates that the resulting materials are mainly (∼88% after 4 h ball-milling) in the hexagonal phase and are on the nanoscale with an average crystallite size of ∼20 nm. The prepared nanoparticles display efficient upconversion emission; upon excitation by a 980 nm laser diode, bright visible blue light emission can be observed. However, in accord with previous results, the strongest emission is observed in the NIR at 800 nm.

  15. Intrinsic optical bistability and frequency upconversion in Tm3+-Yb3+-codoped Y2WO6 phosphor.

    PubMed

    Soni, Abhishek Kumar; Rai, Vineet Kumar

    2014-09-28

    The phase and crystal structure of Tm(3+)-Yb(3+) codoped Y2WO6 phosphor synthesized via the solid state reaction method was analysed by X-ray diffraction. The surface morphology and impurity content of the phosphor were analysed by field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared (FTIR) spectroscopy, respectively. Upon excitation from a 980 nm diode laser, the developed phosphor shows three upconversion emission bands. Codoping with Yb(3+) ions in the Y2WO6:Tm(3+) phosphor significantly enhances the intensity of the frequency upconversion emission. The processes responsible for the UC emissions and their intensity variation upon codoping have been discussed with the help of pump power dependence, energy level diagrams and decay curve analysis. The intrinsic optical bistability and colour tunability are also reported for the developed phosphor. PMID:25091038

  16. Luminescence of YAG doped with Eu, Yb, and Mn ions under VUV excitation

    NASA Astrophysics Data System (ADS)

    Makhov, V. N.; Khaidukov, N. M.

    2014-05-01

    Hydrothermal synthesis has been successfully used to obtain fine-crystalline powders of yttrium aluminum garnet (YAG) doped with manganese ions and codoped with cerium and manganese ions. Using the method of high-temperature solid-state synthesis, ceramic specimens of YAG that contain europium and ytterbium ions have been obtained. In synthesized YAG:Eu and YAG:Yb ceramics, no luminescence that can be attributed to 5 d-4 f transitions in Eu2+ or Yb2+ ions has been detected, even though the scheme of energy levels of these ions constructed with respect to YAG energy bands indicates that there is a potential possibility of the occurrence of 5 d-4 f luminescence for Eu2+ ions in YAG. At room temperature, the luminescence spectrum of hydrothermally synthesized YAG doped with manganese ions consists of two broad bands with maxima at 600 and 750 nm and does not contain any narrow bands in the red or IR range. Therefore, the spectrum contradicts to the properties of the luminescence of Mn2+, Mn3+, or Mn4+ ions in YAG described in the literature, even though the obtained hydrothermal specimens can contain noticeable concentrations only of Mn3+ ions.

  17. Color tunability with temperature and pump intensity in Yb3+/Tm3+ codoped aluminosilicate glass under anti-Stokes excitation

    NASA Astrophysics Data System (ADS)

    Silva, W. F.; Eliel, G. S. N.; dos Santos, P. V.; de Araujo, M. T.; Vermelho, M. V. D.; Udo, P. T.; Astrath, N. G. C.; Baesso, M. L.; Jacinto, C.

    2010-07-01

    Pump and thermally induced color tunabilities were demonstrated in Yb3+/Tm3+ codoped low silica calcium aluminosilicate (LSCAS) glass under anti-Stokes excitation at 1.064 μm. The effects of pump intensity and sample's temperature on the upconversion emissions and mainly on the color tunabilities (from 800 to 480 nm) were investigated. The results revealed a 20- and a threefold reductions at 800/480 nm ratio as, respectively, the pump intensity and sample's temperature were increased from 27 to 700 kW/cm2 and from 296 to 577 K. These behaviors with pump intensity and temperature (a strong increase of the 480 nm emission in comparison with the 800 nm one) were attributed to the several efficient processes occurring in the LSCAS system (Yb3+→Tm3+ energy-transfer processes, easy saturations of the Yb3+ and Tm3+ excited states, and radiative emissions). Besides these assigns, the temperature dependence is mainly assigned to the temperature-dependent effective absorption cross section of the ytterbium sensitizer through the so-called multiphonon-assisted anti-Stokes excitation process. Theoretical analyses and fits of the experimental data provided quantitative information.

  18. Formation enthalpies of LaLn'O3 (Ln'=Ho, Er, Tm and Yb) interlanthanide perovskites

    NASA Astrophysics Data System (ADS)

    Qi, Jianqi; Guo, Xiaofeng; Mielewczyk-Gryn, Aleksandra; Navrotsky, Alexandra

    2015-07-01

    High-temperature oxide melt solution calorimetry using 3Na2OMoO3 at 802 C was performed for interlanthanide perovskites LaLn'O3 (Ln'=Ho, Er, Tm and Yb) and lanthanide oxides (La2O3, Ho2O3, Er2O3, Tm2O3 and Yb2O3). The enthalpies of formation of these interlanthanide perovskites from binary lanthanide oxides at room temperature (25 C) were determined to be -8.33.4 kJ/mol for LaHoO3, -9.93.0 kJ/mol for LaErO3, -10.82.7 kJ/mol for LaTmO3 and -12.32.9 kJ/mol for LaYbO3. There is a roughly linear relationships between these enthalpy values and the tolerance factor for these and for other LaM3+O3 (M=In, Sc, Ga, Al, Fe and Cr) perovskites, confirming that the distortion of the perovskites as results from ionic radius difference of A-site and B-site cations, is the main factor determining the stability of these compounds.

  19. Properties of single crystalline AZn2Sb2 (A=Ca,Eu,Yb)

    SciTech Connect

    May, Andrew F; McGuire, Michael A; Ma, Jie; Delaire, Olivier A; Huq, Ashfia; Custelcean, Radu

    2012-01-01

    Single crystals of CaZn{sub 2}Sb{sub 2}, EuZn{sub 2}Sb{sub 2}, and YbZn{sub 2}Sb{sub 2} were grown from melts of nominal composition AZn{sub 5}Sb{sub 5} (A = Ca,Eu,Yb) with the excess melt being removed at 1073 K. The electrical transport properties are consistent with those previously reported for polycrystalline samples. This confirms that the p-type carrier concentrations ranging from 2 x 10{sup 19} cm{sup -3} to -1 x 10{sup 20} cm{sup -3} are intrinsic to these materials. Also consistent with transport in polycrystalline materials, the carrier mobility is found to be lowest in CaZn{sub 2}Sb{sub 2}, suggesting the trends in mobility and thermoelectric efficiency within these compounds are inherent to the material systems and not due to inhomogeneity or impurities in polycrystalline samples. These results suggest CaZn{sub 2}Sb{sub 2} has the strongest coupling between the doping/defects and the electronic framework. Magnetization measurements reveal an antiferromagnetic transition near 13 K in EuZn{sub 2}Sb{sub 2}, and the observed magnetic anisotropy indicates the spins align parallel and anti-parallel to c in the trigonal lattice. Powder neutron diffraction on polycrystalline samples of CaZn{sub 2}Sb{sub 2} and YbZn{sub 2}Sb{sub 2} reveals smooth lattice expansion to 1000 K, with c expanding faster than a. The Debye temperatures calculated from specific heat capacity data and the isotropic displacement parameters are found to correlate with the carrier mobility, with the CaZn{sub 2}Sb{sub 2} displaying the largest Debye temperature and smallest mobility.

  20. White light upconversion emissions in Er3+/Tm3+/Yb3+ tridoped oxyfluoride glass

    NASA Astrophysics Data System (ADS)

    Guan, Xiaoping; Xu, Wei; Zhu, Shuang; Song, Qiutong; Wu, Xijun; Liu, Hailong

    2015-10-01

    Rare earth ions doped glasses producing visible upconversion emissions are of great interest due to their potential applications in the photonics filed. In fact, practical application of upconversion emissions has been used to obtain color image displays and white light sources. However, there are few reports on the thermal effect on tuning the emission color of the RE doped materials. In this work, the Er3+/Tm3+/Yb3+ tridoped oxyfluoride glasses were prepared through high temperature solid-state method. Under a 980 nm diode laser excitation, the upconversion emissions from the samples were studied. At room-temperature, bright white luminescence, whose CIE chromaticity coordinate was about (0.28, 0.31), can be obtained when the excitation power was 120 mW. The emission color was changed by varying the intensity ratios between RGB bands, which are strongly dependent on the rare earth ions concentration. The temperature dependent color emissions were also investigated. As temperature increased, the intensities for the emission bands presented different decay rates, finally resulting in the changing of the CIE coordinate. When the temperature was 573 K, white light with color coordinate of (0.31, 0.33) was achieved, which matches well with the white reference (0.33, 0.33). The color tunability, high quality of white light and intense emission intensity make the transparent oxyfluoride glasses excellent candidates for applications in solid-state lighting.

  1. Red Eu,Yb:KY(WO4)2 laser at ~702?nm

    NASA Astrophysics Data System (ADS)

    Dashkevich, V. I.; Bagayev, S. N.; Orlovich, V. A.; Bui, A. A.; Loiko, P. A.; Yumashev, K. V.; Yasukevich, A. S.; Kuleshov, N. V.; Vatnik, S. M.; Pavlyuk, A. A.

    2015-08-01

    In this letter, laser operation is demonstrated with a Eu,Yb: KY(WO4)2 crystal on the 5D0?????7F4 transition of the Eu3+ ion. When pumping into the 7F1?????5D1 absorption band by a diode-pumped Nd3+:KGd(WO4)2/KTP laser power-scaled at 533.6?nm up to a watt-level, we achieved 2.5?mW of the continuous wave (CW) red output at ~702.1?nm. At quasi-CW pumping with a duty cycle of 10%, the peak power of the ms-long pulses arrived at ~19?mW, corresponding to a green-to-red conversion efficiency of 0.8%.

  2. Solvent extraction behavior of trivalent Nd, Eu, Ho, and Yb with dibenzoylmethane at 80{degree}C

    SciTech Connect

    Gao, J.; Choppin, G.R.

    1995-05-01

    The extraction behavior of trivalent lanthanide ions (Nd, Eu, Ho and Yb) has been studied with dibenzoylmethane (DBM) at 80{degree}C using molten paraffin wax as diluent. In the range of pH 7 to 8, the extraction of lanthanide cations is greater than 90%. The ratio of Ln:DBM in the extracted species was determined to be 1:3 by the slope analysis method. The pH{sub 1/2} values of extraction and the extraction constants of Nd(III), Eu(III), Ho(III) and Yb(III) are reported. 22 refs., 2 figs., 1 tab.

  3. Yb{sub 14?x}Tm{sub x}MnSb{sub 11} (0

    SciTech Connect

    Roudebush, John H.; Grebenkemper, Jason; Hu, Yufei; Kazem, Nasrin; Abdusalyamova, M.N.

    2014-03-15

    The compounds, Yb{sub 14?x}Tm{sub x}MnSb{sub 11} (0Tm was determined from wavelength dispersive microprobe analysis to be x=0.45 (1). Single crystal data are consistent with the Ca{sub 14}AlSb{sub 11} structure type and one formula unit can be described as consisting of 14 Yb{sup 2+} cations, MnSb{sub 4} tetrahedron, Sb{sub 3} linear anion and 4 Sb{sub 3}{sup -} anions. The site occupancy of the Tm atom was not determined because of the small amount and small difference in scattering between Tm and Yb. The difference in bond lengths or angles between the solid solution and pristine Yb{sub 14}MnSb{sub 11} is less than 1%. The magnetic susceptibility of samples prepared by Sn flux with the nominal composition of Yb{sub 14?x}Tm{sub x}MnSb{sub 11} (x=0.1, 0.2, 0.3, and 0.4), show that these phases are ferromagnetic at low temperature with the T{sub C} decreasing from 56 to 39 K with increasing x. Magnetic saturation for the x=0.4 composition at 5 K is consistent with Tm being present as Tm{sup 3+} and a negative magnetoresistance ratio (MR=[(?(H)??(0))/?(H)]100%) of 18% at 3 T is observed. -- Graphical abstract: Magnetic susceptibility (?) for Yb{sub 14?x}Tm{sub x}MnSb{sub 11} at H{sub a}=0.01 T as a function of temperature along with a view of the structure. Highlights: New rare earth containing transition metal Zintl phase. Control of magnetic properties through aliovalent substitution. Magnetic ordering due to both d and f electrons. Large magnetoresistance at low temperatures.

  4. Highly improved upconversion luminescence in NaGd(WO4)2:Yb3+/Tm3+ inverse opal photonic crystals

    NASA Astrophysics Data System (ADS)

    Wang, Yunfeng; Xu, Wen; Cui, Shaobo; Xu, Sai; Yin, Ze; Song, Hongwei; Zhou, Pingwei; Liu, Xiaoyan; Xu, Lin; Cui, Haining

    2015-01-01

    The upconversion luminescence (UCL) of rare earth (RE) ions doped nanomaterials has attracted extensive interest because of its wide and great potential applications. However, the lower UCL efficiency is still an obstacle for real applications. Photonic modulation is a novel way to improve the efficiency of UCL. In this work, NaGd(WO4)2:Yb3+/Tm3+ inverse opal photonic crystals (IOPCs) were fabricated through the polymethylmethacrylate (PMMA) template and the modification of the IOPC structure on the emission spectra and dynamics of Tm3+ ions was systemically studied. It is interesting to observe that in the IOPCs, the high-order UCL 1D2-3H6/3F4 was relatively enhanced. At the same time, the local thermal effect induced by laser irradiation was suppressed. Furthermore, the overall intensity ratio of visible UCL to near-infrared (NIR) down-conversion luminescence (DCL) was 2.8-8 times improved than that of the grinded reference (REF) and independent of the photonic stop band (PSB). The studies on UCL dynamics indicated that the nonradiative transition rate of Tm3+ was considerably suppressed. The facts above indicated that in the IOPCs the UCL efficiency of Tm3+ was largely improved due to the periodic macroporous structure.The upconversion luminescence (UCL) of rare earth (RE) ions doped nanomaterials has attracted extensive interest because of its wide and great potential applications. However, the lower UCL efficiency is still an obstacle for real applications. Photonic modulation is a novel way to improve the efficiency of UCL. In this work, NaGd(WO4)2:Yb3+/Tm3+ inverse opal photonic crystals (IOPCs) were fabricated through the polymethylmethacrylate (PMMA) template and the modification of the IOPC structure on the emission spectra and dynamics of Tm3+ ions was systemically studied. It is interesting to observe that in the IOPCs, the high-order UCL 1D2-3H6/3F4 was relatively enhanced. At the same time, the local thermal effect induced by laser irradiation was suppressed. Furthermore, the overall intensity ratio of visible UCL to near-infrared (NIR) down-conversion luminescence (DCL) was 2.8-8 times improved than that of the grinded reference (REF) and independent of the photonic stop band (PSB). The studies on UCL dynamics indicated that the nonradiative transition rate of Tm3+ was considerably suppressed. The facts above indicated that in the IOPCs the UCL efficiency of Tm3+ was largely improved due to the periodic macroporous structure. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05688d

  5. Upconversion white-light emission in Ho3+/Yb3+/Tm3+ tridoped LiNbO3 single crystal.

    PubMed

    Xing, Lili; Wu, Xiaohong; Wang, Rui; Xu, Wei; Qian, Yannan

    2012-09-01

    Ho3+/Yb3+/Tm3+ tridoped LiNbO3 single crystal exhibiting intense upconversion white light under 980 nm excitation has been successfully fabricated by the Czochralski method. The tridoped LiNbO3 single crystal offers power dependent color tuning properties by simply changing excitation power. Efficient three-photon blue upconversion emission and two-photon green and red upconversion emissions have been observed. In addition, the red emission of Ho3+ originates dominantly from the nonradiative decay of green emission. The LiNbO3 with upconversion white light will be a potential laser candidate material. PMID:22940941

  6. 2.7 μm emission properties of Er3+/Yb3+/Eu3+: SrGdGa3O7 and Er3+/Yb3+/Ho3+: SrGdGa3O7 crystals

    NASA Astrophysics Data System (ADS)

    Xia, Houping; Feng, Jianghe; Ji, Yuexia; Sun, Yijian; Wang, Yan; Jia, Zhitai; Tu, Chaoyang

    2016-04-01

    Er3+/Yb3+/Eu3+: SrGdGa3O7 and Er3+/Yb3+/Ho3+: SrGdGa3O7 crystals were grown by Czochralski technology and detailed spectroscopic analyses were carried out. It was found that the spectra of Er3+/Yb3+/Eu3+: SrGdGa3O7 crystal show weaker near-infrared emission and stronger mid-infrared emission as compared with Er3+/Yb3+: SrGdGa3O7 crystal. Furthermore, the lifetime of the 4I13/2 state decreases from 10.58 ms in Er3+/Yb3+: SrGdGa3O7 crystal to 6.87 ms in Er3+/Yb3+/Eu3+: SrGdGa3O7 crystal, that is, the self-saturation for 2.7 μm laser in Er3+/Yb3+/Eu3+: SrGdGa3O7 crystal is suppressed greatly. These results indicate that the doping of Eu3+ in Er3+/Yb3+: SrGdGa3O7 crystal is beneficial to improve the 2.7 μm laser. In contrast, introducing Ho3+ in Er3+/Yb3+: SrGdGa3O7 crystal is adverse to realize Er3+-activated MIR laser operation. So Er3+/Yb3+/Eu3+: SrGdGa3O7 crystal could be a potential MIR gain media for enhanced 2.7 μm laser.

  7. Enhanced NIR downconversion luminescence by precipitating nano Ca5(PO4)3F crystals in Eu2+-Yb3+ co-doped glass

    NASA Astrophysics Data System (ADS)

    Li, Chen; Song, Zhiguo; Li, Yongjin; Lou, Kai; Qiu, Jianbei; Yang, Zhengwen; Yin, Zhaoyi; Wang, Xue; Wang, Qi; Wan, Ronghua

    2013-10-01

    Eu2+-Yb3+ co-doped transparent glass-ceramic containing nano-Ca5(PO4)3F (FAP) was prepared in reducing atmosphere. XRD and TEM analysis indicated that nano-FAP about 40 nm precipitated homogeneously in glass matrix after heat treatment. Confirmed by spectroscopy measurements, the crystal-like absorption and emission of Eu2+ indicated the partition of Eu2+ into FAP nanocrystals in glass ceramic. NIR emission due to the transition 2F?2F of Yb3+ ions (about 980-1100 nm) was observed from glasses under ultraviolet excitation, ascribed to downconversion from Eu2+ to Yb3+, which can be enhanced by precipitating nano-FAP crystals. The results indicated that Eu2+-Yb3+ co-doped glass-ceramic embedding with nano-FAP is a promising candidate as downconversion materials for enhancing conversion efficiency of solar cells.

  8. Pure and almost pure NIR emission of Tm and Tm,Yb-CeO2 under UV, X-ray and NIR up-conversion excitation: key roles of level selective antenna sensitization and charge-compensation.

    PubMed

    Avram, Daniel; Cojocaru, Bogdan; Urda, Adriana; Tiseanu, Ion; Florea, Mihaela; Tiseanu, Carmen

    2015-11-18

    Herein, we report on the pure and almost pure near-infrared (NIR) emission at around 807 nm observed for Tm(Yb) (co)-doped CeO2 nanoparticles (NPs) under UV, X-ray and NIR up-conversion excitation. The optical responses are attributed to the low-lying charge-transfer of CeO2 that acts as a selective antenna sensitizer of the Tm (3)H4 emission and Yb doping that lowers the local symmetry at Tm sites and introduces additional phonon modes. Selective antenna sensitization is also observed for Er/Ho (Yb) (co)-doped CeO2 NPs. To the best of our knowledge, this is a first study which correlates the down- and up-conversion emission properties of lanthanide(s)-(co) dopants with the CeO2 structure highlighting also the outstanding potential of these NPs in high-penetration tissue imaging and therapy. PMID:26411533

  9. Upconversion luminescent property and EPR study of NaGdF4:Yb3+/Tm3+ synthesized by the hydrothermal method

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Zhang, Jing-Ying; Liu, Kai; Gao, Hong-Jian; Yu, Xiao-Long; Cao, Yang; Liu, Zhong-Xin

    2015-09-01

    Water soluble upconversion (UC) luminescence hexagonal-phase NaGdF4: Yb3+/Tm3+ nanoparticles have been successfully synthesized by the hydrothermal method. XRD, SEM, UC photoluminescence spectra and electron paramagnetic resonance (EPR) spectrum were used to characterize the nanoparticles. The intensity of UC emission region could be controlled through different sodium source and the fluorine source, 6PJ→8S7/2 emission of Gd3+ is also observed at 310 nm. A broad spectrum with a dominant resonance at g of about 2 was observed by the EPR spectrum of the NaGdF4:Yb3+/Tm3+ nanoparticles. The transparent NaGdF4:Yb3+/Tm3+ solution presented naked eye-visible violet-blue light under the 980 nm LD excitation. The current work paves the way for their potential application in infrared tomography and magnetic resonance imaging (MRI).

  10. Structural, electronic, mechanical and magnetic properties of rare earth nitrides REN (RE= Pm, Eu and Yb)

    NASA Astrophysics Data System (ADS)

    Murugan, A.; Rajeswarapalanichamy, R.; Santhosh, M.; Iyakutti, K.

    2015-07-01

    The structural, electronic and mechanical properties of rare earth nitrides REN (RE=Pm, Eu and Yb) are investigated in NaCl and CsCl, and zinc blende structures using first principles calculations based on density functional theory. The calculated lattice parameters are in good agreement with the available results. Among the considered structures, these nitrides are most stable in NaCl structure. A pressure induced structural phase transition from NaCl to CsCl phase is observed in all these nitrides. The electronic structure reveals that these rare earth nitrides are half metallic at normal pressure. These nitrides are found to be covalent and ionic in the stable phase. The computed elastic constants indicate that these nitrides are mechanically stable and elastically anisotropic. Our results confirm that these nitrides are ferromagnetic in nature. A ferromagnetic to non-magnetic phase transition is observed at the pressures of 21.5 GPa and 46.1 GPa in PmN and YbN respectively.

  11. Synthetic and spectroscopic studies of vanadate glaserites I: Upconversion studies of doubly co-doped (Er, Tm, or Ho):Yb:K3Y(VO4)2

    NASA Astrophysics Data System (ADS)

    Kimani, Martin M.; Chen, Hongyu; McMillen, Colin D.; Anker, Jeffery N.; Kolis, Joseph W.

    2015-03-01

    The synthesis and upconversion properties of trigonal glaserite-type K3Y(VO4)2 co-doped with Er3+/Yb3+, Ho3+/Yb3+, or Tm3+/Yb3+ were studied. Powder samples were synthesized by solid state reactions at 1000 C for 48 h, while well-formed hexagonal single crystals of the same were grown hydrothermally using 10 M K2CO3 at 560-650 C. Infrared-to-visible upconversion by Er3+/Yb3+, Ho3+/Yb3+, or Tm3+/Yb3+ codoped-K3Y(VO4)2 glaserite powder and single crystals was observed, and the upconversion spectral properties were studied as a function of different Er3+, Tm3+, Ho3+, and Yb3+ ion concentrations. The process is observed under 980 nm laser diode excitation and leads to strong green (552 nm) and red (659 nm) emission for Er3+/Yb3+, green (549 nm) and red (664 nm) emission for Ho3+/Yb3+, and blue (475 nm) and red (647 nm) emission for Tm3+/Yb3+. The main mechanism that allows for up-conversion is attributed the energy transfer among Yb3+ and the various Er3+/Ho3+/Tm3+ ions in excited states. These results illustrate the large potential of co-doped alkali double vanadates for photonic applications involving optoelectronics devices.

  12. Tunable multicolor and white-light upconversion luminescence in Yb3+/Tm3+/Ho3+ tri-doped NaYF4 micro-crystals.

    PubMed

    Lin, Hao; Xu, Dekang; Teng, Dongdong; Yang, Shenghong; Zhang, Yueli

    2015-09-01

    NaYF4 micro-crystals with various concentrations of Yb(3+) /Tm(3+) /Ho(3+) were prepared successfully via a simple and reproducible hydrothermal route using EDTA as the chelating agent. Their phase structure and surface morphology were studied using powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD patterns revealed that all the samples were pure hexagonal phase NaYF4. SEM images showed that Yb(3+)/Tm(3+)/Ho(3+) tri-doped NaYF4 were hexagonal micro-prisms. Upconversion photoluminescence spectra of Yb(3+)/Tm(3+)/Ho(3+) tri-doped NaYF4 micro-crystals with various dopant concentrations under 980 nm excitation with a 665 mW pump power were studied. Tunable multicolor (purple, purplish blue, yellowish green, green) and white light were achieved by simply adjusting the Ho(3+) concentration in 20%Yb(3+)/1%Tm(3+)/xHo(3+) tri-doped NaYF4 micro-crystals. Furthermore, white-light emissions could be obtained using different pump powers in 20%Yb(3+)/1%Tm(3+)/1%Ho(3+) tri-doped NaYF4 micro-crystals at 980 nm excitation. The pump power-dependent intensity relationship was studied and relevant energy transfer processes were discussed in detail. The results suggest that Yb(3+)/Tm(3+) Ho(3+) tri-doped NaYF4 micro-crystals have potential applications in optoelectronic devices such as photovoltaic, plasma display panel and white-light-emitting diodes. PMID:25377774

  13. Simultaneous size and luminescence control of NaYF4:Yb3+/RE3+ (RE = Tm, Ho) microcrystals via Li+ doping

    NASA Astrophysics Data System (ADS)

    Lin, Hao; Xu, Dekang; Teng, Dongdong; Yang, Shenghong; Zhang, Yueli

    2015-07-01

    Enhancement of upconversion (UC) luminescence is imperative for the applications of UC microcrystals (MCs). In this work, NaYF4:Yb3+/RE3+ (RE = Tm, Ho) MCs via Li+ doping were successfully prepared by a simple hydrothermal process with the assistance of citric acid. The UC luminescence intensities of NaYF4:Yb3+/RE3+ (RE = Tm, Ho) are significantly enhanced via Li+ doping at different concentrations. Compared to Li+-absent sample, UC luminescence intensities of blue emission (477 nm) and red emission (649 nm) in NaYF4:Yb3+/Tm3+ MCs via 15 mol% Li+ doping are improved by 10 and 9 times, respectively; UC luminescence intensities of green emission (538 nm) and red emission (644 nm) in NaYF4:Yb3+/Ho3+ MCs via 15 mol% Li+ doping are improved by 12 and 3 times, respectively. The mechanism of the enhancement via Li+ doping is discussed in details, which may be attributed to the fact that Li+ doping can cause the distortion of the local symmetry around RE ions. Our results indicate that the enhanced UC luminescence of NaYF4:Yb3+/RE3+ (RE = Tm, Ho) MCs via Li+ doping may have potential applications in optoelectronic devices such as solar cells and plasma display panel.

  14. Enhancement of near-infrared to near-infrared upconversion emission in the CeO?: Er?, Tm?, Yb? inverse opals.

    PubMed

    Wu, Hangjun; Yang, Zhengwen; Liao, Jiayan; Lai, Shenfeng; Qiu, Jianbei; Song, Zhiguo; Yang, Yong; Zhou, Dacheng

    2014-02-15

    In this Letter, CeO?: Er?, Tm?, Yb? inverse opal with near-infrared to near-infrared upconversion emission was prepared by polystyrene colloidal crystal templates, and the influence of photonic bandgap on the upconversion emission was investigated. Comparing with the reference sample, suppression of the blue or red upconversion luminescence was observed in the inverse opals. It is interesting that the near-infrared upconversion emission located at about 803 nm was enhanced due to the inhibition of visible upconversion emission in the inverse opals. Additionally, the variety of upconversion emission mechanisms was observed and discussed in the CeO?: Er?, Tm?, Yb? inverse opals. PMID:24562241

  15. Hydrothermal synthesis of Yb3+, Tm3+ co-doped Gd6MoO12 and its upconversion properties

    NASA Astrophysics Data System (ADS)

    Di, Qiu-Mei; Sun, Yu-Mei; Xu, Qi-Guang; Han, Liu; Xue, Bing; Sun, Jia-Yue

    2015-06-01

    Yb3+, Tm3+ co-doped Gd6MoO12 phosphors with different morphologies are prepared by the hydrothermal method. The dendrites present different morphologies (including hexagonal prisms, spindles, and spheres) after changing the pH value and edetate disodium (EDTA) usage. It is found that each of the two factors plays a crucial role in forming different morphologies. The up-conversion (UC) luminescence is studied. Under 980-nm semiconductor laser excitation, relatively strong blue emission and weak red emission are observed. Finally, the effect of pumping power on the UC luminescence properties and the level diagram mechanism of Gd6MoO12:Yb3+/Tm3+ phosphor are also discussed. Project supported by the National Natural Science Foundation of China (Grant No. 20976002), the Beijing Natural Science Foundation, China (Grant No. 2122012), the Key Projects for Science and Technology of Beijing Education Commission, China (Grant No. KZ201310011013), and the Education and Research Fund of Guangdong Province, China (Grant No. 2011B090400100).

  16. Uniform NaYF{sub 4}:Yb, Tm hexagonal submicroplates: Controlled synthesis and enhanced UV and blue upconversion luminescence

    SciTech Connect

    Huang, Wenjuan; Ding, Mingye; Huang, Hengming; Jiang, Chenfei; Song, Yan; Ni, Yaru; Lu, Chunhua; Xu, Zhongzi

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ? ?-NaYF{sub 4} phosphors as an excellent upconversion materials. ? Oleic acid can promote the transformation of ? ? ? phase NaYF{sub 4}. ? The shape and size of ?-NaYF{sub 4} submicroplate can be tuned by reactant concentration. ? Enhanced UV and blue peaks can be obtained by varying Yb{sup 3+} and Tm{sup 3+} concentration. -- Abstract: We reported the preparation of cubic (?-) and hexagonal (?-) NaYF{sub 4} particles in high boiling organic solvents 1-octadecene (ODE) and oleic acid (OA), through a thermal decomposition synthesis route. The as-prepared products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence (PL) spectra. By tuning the OA/ODE volume ratio and reactant concentration, we could manipulate the morphology, size, and crystal structure of the products. Highly uniform ?-NaYF{sub 4} submicroplates were obtained from ?-NaYF{sub 4} nanoparticles by increasing the OA/ODE volume ratio, while the phase kept unchanged with the increasing of reactant concentration. Upconversion emissions from UV to NIR emissions were observed in ?-NaYF{sub 4} hexagonal submicroplates under 980 nm laser diode excitation. In addition, the enhanced UV and blue upconversion emissions were obtained by varying Tm{sup 3+} and Yb{sup 3+} ion concentration.

  17. Determination of the refractive index of ?-NaYF4/Yb3+/Er3+/Tm3+ nanocrystals using spectroscopic refractometry

    NASA Astrophysics Data System (ADS)

    Sokolov, V. I.; Zvyagin, A. V.; Igumnov, S. M.; Molchanova, S. I.; Nazarov, M. M.; Nechaev, A. V.; Savelyev, A. G.; Tyutyunov, A. A.; Khaydukov, E. V.; Panchenko, V. Ya.

    2015-04-01

    A method for measuring refractive index n of nanosize particles in the visible and near-IR spectral ranges is proposed. The method is based on comparing refractive index n colloid of a colloid solution of nanoparticles in several solvents with refractive indices n solvent of corresponding pure solvents and has an accuracy of 2 10-4. Upconversion nanosize phosphors (UCNPs) are synthesized in the form of a ?-NaYF4 crystalline matrix doped with Yb3+, Er3+, and Tm3+ rare earth ions. UCNPs have a doped core with a diameter of 40 5 nm and undoped shell with a thickness of 3-5 nm. Synthesized nanocrystals possess intense photoluminescence in the blue, green, and red spectral ranges upon excitation by IR radiation with a wavelength of 977 nm. Using a spectroscopic refractometer, the dispersion of the refractive index of ?-NaYF4/Yb3+/Er3+/Tm3+ nanocrystals was measured for the first time in the spectral range of 450-1000 nm with an accuracy of 2 10-4.

  18. Hall and transverse even effects in the vicinity of a quantum critical point in Tm{sub 1-x}Yb{sub x}B{sub 12}

    SciTech Connect

    Sluchanko, N. E. Azarevich, A. N.; Bogach, A. V.; Glushkov, V. V.; Demishev, S. V.; Anisimov, M. A.; Levchenko, A. V.; Filipov, V. B.; Shitsevalova, N. Yu.

    2012-09-15

    The angular, temperature, and magnetic field dependences of the resistance recorded in the Hall effect geometry are studied for the rare-earth dodecaboride Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions where the metal-insulator and antiferromagnetic-paramagnetic phase transitions are observed in the vicinity of the quantum critical point x{sub c} Almost-Equal-To 0.3. The measurements performed on high-quality single crystals in the temperature range 1.9-300 K for the first time have revealed the appearance of the second harmonic contribution, a transverse even effect in these fcc compounds near the quantum critical point. This contribution a is found to increase drastically both under the Tm-to-ytterbium substitution in the range x > x{sub c} and with an increase in the external magnetic field. Moreover, as the Yb concentration x increases, a negative peak of a significant amplitude appears on the temperature dependences of the Hall coefficient R{sub H}(T) for the Tm{sup 1-x}Yb{sub x}B{sub 12} compounds, in contrast to the invariable behavior R{sub H}(T) Almost-Equal-To const found for TmB{sub 12}. The complicated activation-type behavior of the Hall coefficient is observed at intermediate temperatures for x {>=} 0.5 with activation energies E{sub g}/k{sub B} Almost-Equal-To 200 K and E{sub a}/k{sub B} 55-75 K, and the sign inversion of R{sub H}(T) is detected at liquid-helium temperatures in the coherent regime. Renormalization effects in the electron density of states induced by variation of the Yb concentration are analyzed. The anomalies of the charge transport in Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions in various regimes (charge gap formation, intra-gap many-body resonance, and coherent regime) are discussed in detail and the results are interpreted in terms of the electron phase separation effects in combination with the formation of nanosize clusters of rare earth ions in the cage-glass state of the studied dodecaborides. The data obtained allow concluding that the emergence of Yb-Yb dimers in the Tm{sub 1-x}Yb{sub x}B{sub 12} cage-glass matrix is the origin of the metal-insulator transition observed in the achetypal strongly correlated electron system of YbB{sub 12}.

  19. Hall and transverse even effects in the vicinity of a quantum critical point in Tm1 - x Yb x B12

    NASA Astrophysics Data System (ADS)

    Sluchanko, N. E.; Azarevich, A. N.; Bogach, A. V.; Glushkov, V. V.; Demishev, S. V.; Anisimov, M. A.; Levchenko, A. V.; Filipov, V. B.; Shitsevalova, N. Yu.

    2012-09-01

    The angular, temperature, and magnetic field dependences of the resistance recorded in the Hall effect geometry are studied for the rare-earth dodecaboride Tm1 - x Yb x B12 solid solutions where the metal-insulator and antiferromagnetic-paramagnetic phase transitions are observed in the vicinity of the quantum critical point x c ? 0.3. The measurements performed on high-quality single crystals in the temperature range 1.9-300 K for the first time have revealed the appearance of the second harmonic contribution, a transverse even effect in these fcc compounds near the quantum critical point. This contribution a is found to increase drastically both under the Tm-to-ytterbium substitution in the range x > x c and with an increase in the external magnetic field. Moreover, as the Yb concentration x increases, a negative peak of a significant amplitude appears on the temperature dependences of the Hall coefficient R H( T) for the Tm1 - x Yb x B12 compounds, in contrast to the invariable behavior R H( T) ? const found for TmB12. The complicated activation-type behavior of the Hall coefficient is observed at intermediate temperatures for x ? 0.5 with activation energies E g / k B ? 200 K and E a/ k B = 55-75 K, and the sign inversion of R H( T) is detected at liquid-helium temperatures in the coherent regime. Renormalization effects in the electron density of states induced by variation of the Yb concentration are analyzed. The anomalies of the charge transport in Tm1 - x Yb x B12 solid solutions in various regimes (charge gap formation, intra-gap many-body resonance, and coherent regime) are discussed in detail and the results are interpreted in terms of the electron phase separation effects in combination with the formation of nanosize clusters of rare earth ions in the cage-glass state of the studied dodecaborides. The data obtained allow concluding that the emergence of Yb-Yb dimers in the Tm1 - x Yb x B12 cage-glass matrix is the origin of the metal-insulator transition observed in the achetypal strongly correlated electron system of YbB12.

  20. Upconversion-luminescent/magnetic dual-functional sub-20 nm core-shell SrF2:Yb,Tm@CaF2:Gd heteronanoparticles.

    PubMed

    Li, Ai-Hua; Lü, Mengyun; Yang, Jun; Chen, Lin; Cui, Xiaohong; Sun, Zhijun

    2016-04-01

    Sub-20 nm core-shell and water-soluble SrF2:Yb,Tm@CaF2:Gd heteronanoparticles with both upconversion luminescence (UCL) and magnetic resonance imaging (MRI) capabilities were designed and synthesized via a two-step hydrothermal method. In the design of the heteronanoparticles, SrF2:Yb,Tm nanoparticles with high UCL efficiency are chosen as the core material for strong UCL output; and by epitaxially coating the SrF2:Yb,Tm core particles with inert and biocompatible shells of CaF2:Gd, the core-shell heteronanoparticles are endowed with a magnetic capability (longitudinal relaxivity of 2.4 mM(-1) s(-1)) for MRI, as well as an enhancement of the near infrared (NIR) UCL by 9.2 times. The aqueous dispersion of SrF2:Yb,Tm@CaF2:Gd heteronanoparticles with a concentration of 2.6 wt% can emit NIR UCL so as to be easily detected with a fiber optical spectrometer under illumination of a 975 nm laser diode with a power density of 8.8 W cm(-2). Such a dispersion with a Gd(3+) concentration of 0.0143 mM in the shell region of the heteronanoparticles can also generate the detectable quickening of longitudinal relaxation. The results promise the strong potential of this nanomaterial for applications in bioimaging as a dual-functional probe. PMID:26934836

  1. Features of the formation of magnetic moments of Tm3+ and Yb3+ rare-earth ions in LuB12 cage glass

    NASA Astrophysics Data System (ADS)

    Sluchanko, N. E.; Azarevich, A. N.; Anisimov, M. A.; Bogach, A. V.; Voronov, V. V.; Gavrilkin, S. Yu.; Glushkov, V. V.; Demishev, S. V.; Kuznetsov, A. V.; Mitsen, K. V.; Filippov, V. B.; Shitsevalova, N. Yu.; Gabani, S.; Flachbart, K.

    2014-12-01

    The features of the formation of the magnetic moments of Tm3+ and Yb3+ ions in a metallic matrix of LuB12 cage glass have been studied in measurements of the magnetization and specific heat in the temperature range of 1.9-300 K in magnetic fields up to 90 kOe. It has been shown that a paramagnetic response from the localized moments of isolated ions Tm3+ (7.6?B) and Yb3+ (4.5?B) is observed at temperatures of 150-300 K. A transition to the cage glass phase at low temperatures ( T ? T* 60 K) is accompanied by disordering in the system of rare-earth ions and by formation of many-body states near Tm3+ and Yb3+ ions. At low temperatures near T m in low magnetic fields, the appearance of an additional spin polarization, which is suppressed with an increase in the field, has been observed. The effective moments and g-factors of Tm and Yb obtained in high fields imply both the binding of a small fraction of magnetic ions to antiferromagnetic dimers and the ?6 ground state of the 2 F 7/2 multiplet of the ytterbium ion. A scenario alternative to the Kondo-type behavior has been proposed to explain the nature of many-body states and the appearance of the spin polarization in rare-earth dodecaborides.

  2. The action mechanism of TiO2:NaYF4:Yb3+,Tm3+ cathode buffer layer in highly efficient inverted organic solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Chunyu; Chen, Huan; Zhao, Dan; Shen, Liang; He, Yeyuan; Guo, Wenbin; Chen, Weiyou

    2014-08-01

    We report the fabrication and characteristics of organic solar cells with 6.86% power conversion efficiency (PCE) by doping NaYF4:Yb3+,Tm3+ into TiO2 cathode buffer layer. The dependence of devices performance on doping concentration of NaYF4:Yb3+,Tm3+ is investigated. Results indicate that short-circuit current density (Jsc) has an apparent improvement, leading to an enhancement of 22.7% in PCE for the optimized doping concentration of 0.05 mmol ml-1 compared to the control devices. NaYF4:Yb3+,Tm3+ nanoparticles (NPs) can play threefold roles, one is that the incident light in visible region can be scattered by NaYF4 NPs, the second is that solar irradiation in infrared region can be better utilized by Up-conversion effect of Yb3+ and Tm3+ ions, the third is that electron transport property in TiO2 thin film can be greatly improved.

  3. Pulsed-laser-assisted synthesis of a Tm3+/Yb3+ co-doped CaMoO4 colloidal nanocrystal and its upconversion luminescence

    NASA Astrophysics Data System (ADS)

    Cho, Kyoungwon; Choi, Jaeha; Lee, Jung-Il; Ryu, Jeong Ho

    2016-01-01

    We report a novel synthetic route for the synthesis of Tm3+/Yb3+ co-doped calcium molybdate (CaMoO4) nanoparticles by using pulsed laser ablation in ethanol. The crystalline phase, particle morphology, particle size distribution, laser ablation mechanism, and upconversion (UC) luminescent properties are investigated. Stable colloidal suspensions consisting of well-dispersed Tm3+/Yb3+ co-doped CaMoO4 nanoparticles with a narrow size distribution could be obtained without any surfactant. Under 980-nm excitation, a Tm3+/Yb3+ co-doped nanocolloidal CaMoO4 suspension showed bright blue emission at a wavelength near 475 nm, which was generated by the 1G4 → 3H6 transition, and a weak red emission at a wavelength near 650 nm due to the 3F2 → 3H6 transition. The Tm3+/Yb3+ co-doped nanocrystalline CaMoO4 suspension exhibited a strong blue emission visible to the naked eyes, and a possible UC mechanism that depends on the pump-power dependence is discussed in detail.

  4. Observation of multi-mode: Upconversion, downshifting and quantum-cutting emission in Tm3+/Yb3+ co-doped Y2O3 phosphor

    NASA Astrophysics Data System (ADS)

    Yadav, Ranvijay; Singh, S. K.; Verma, R. K.; Rai, S. B.

    2014-04-01

    Micro-crystalline Y2O3 phosphor co-doped with Yb3+/Tm3+ has been synthesized and characterized. The phosphor material gives efficient multimodal emission via downshifting (DS), upconversion (UC), and downconversion (DC)/quantum cutting (QC) luminescence processes. Cross relaxation and co-operative energy transfer (CET) have been ascribed as the possible mechanism for QC; as result of which a UV/blue photon absorbed by Tm3+ splits into two near infrared photons (wavelength range 950-1050 nm) emitted by Yb3+. The Yb3+ concentration dependent ET efficiency and QC efficiency has also been evaluated. Such multi-mode emitting phosphors could have potential applications in increasing the conversion efficiency of solar cells via spectral modification.

  5. Lasing in a Tm : Yb{sub 3}Al{sub 5}O{sub 12} crystal pumped at 1.678 ?m

    SciTech Connect

    Zavartsev, Yu D; Zagumennyi, A I; Kalachev, Yu L; Kutovoi, S A; Mikhailov, V A; Shcherbakov, I A

    2014-10-31

    The Yb{sub 3}Al{sub 5}O{sub 12} (YbAG) crystal is proposed as a matrix of Tm{sup 3+}-doped laser elements for two-micron lasers. A Tm : YbAG crystal of high optical quality is grown by the Czochralski method and its spectral and luminescent characteristics are studied. The luminescence decay time for the upper laser level {sup 3}F{sub 4} is measured to be 4.7 ms. Lasing in this crystal pumped by a 1.678-?m fibre laser is obtained at a wavelength of 2.02 ?m for the first time. The total and slope efficiencies of the laser at room temperature and an output power up to 330 mW reach 33% and 41%, respectively. (lasers)

  6. Are the carbon monoxide complexes of Cp(2)M (M = Ca, Eu, or Yb) carbon or oxygen bonded? An answer from DFT calculations.

    PubMed

    Maron, L; Perrin, L; Eisenstein, O; Andersen, R A

    2002-05-22

    DFT calculations have been performed on the CO adducts of the bivalent lanthanides, Cp(2)M(CO)(x), where M is Eu or Yb and x is 1 or 2, the alkaline earth metallocene Cp(2)Ca(CO), and the methylisocyanide adducts of Yb. The calculated nu(CO) values are in agreement with experiment for Cp(2)M(CO) when M is Ca or Eu, but in striking disagreement when the CO is bound to the metal by way of the carbon atom in CO in the case of Yb. The calculated nu(CO) values for M = Yb are brought into agreement with experiment when the CO is allowed to bond to Cp(2)Yb by way of the oxygen atom. PMID:12010015

  7. Doxorubicin conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles for therapy and sensing of drug delivery by luminescence resonance energy transfer.

    PubMed

    Dai, Yunlu; Yang, Dongmei; Ma, Ping'an; Kang, Xiaojiao; Zhang, Xiao; Li, Chunxia; Hou, Zhiyao; Cheng, Ziyong; Lin, Jun

    2012-11-01

    In this study, we report an anticancer drug delivery system based on doxorubicin (DOX)-conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles. The as-synthesized nanoparticles consist of uniform spherical nanoparticles with an average diameter of 25 nm. The drug delivery system demonstrates the ability to release DOX by cleavage of the hydrazone bond in mildly acidic environments. The spectra overlap between emission of donor NaYF(4):Yb(3+)/Tm(3+) nanoparticles at 452 nm ((1)D(2)→(3)F(4)) and 477 nm ((1)G(4)→(3)H(6)) and the broad absorbance of acceptor DOX centered at around 480 nm enables energy transfer to occur between the nanoparticles and DOX. The quenching and recovery of the up-conversion luminescence of NaYF(4):Yb(3+)/Tm(3+) by DOX due to luminescence resonance energy transfer (LRET) mechanism are applied as optical probe to confirm the DOX conjunction and monitor the release of DOX. The DOX-conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles exhibit an obvious cytotoxic effect on SKOV3 ovarian cancer cells via MTT assay. Meanwhile, the endocytosis process of DOX-conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles by SKVO3 cells was demonstrated through confocal laser scanning microscopy (CLSM), flow cytometry and ICP-OES. Such drug delivery system, which combines pH-triggered drug-release and up-converting nanoparticles-based LRET property, has excellent potential applications in cancer therapy and smart imaging. PMID:22938822

  8. Frequency upconversion luminescence from Yb{sup +3}-Tm{sup +3} codoped PbO-GeO{sub 2} glasses containing silver nanoparticles

    SciTech Connect

    Assumpcao, Thiago A. A.; Silva, Davinson M. da; Kassab, Luciana R. P.

    2009-09-15

    Infrared-to-visible and infrared-to-infrared frequency upconversion processes in Yb{sup 3+}-Tm{sup 3+} doped PbO-GeO{sub 2} glasses containing silver nanoparticles (NPs) were investigated. The experiments were performed by exciting the samples with a diode laser operating at 980 nm (in resonance with the Yb{sup 3+} transition {sup 2}F{sub 7/2}->{sup 2}F{sub 5/2}) and observing the photoluminescence (PL) in the visible and infrared regions due to energy transfer from Yb{sup 3+} to Tm{sup 3+} ions followed by excited state absorption in the Tm{sup 3+} ions. The intensified local field in the vicinity of the metallic NPs contributes for enhancement in the PL intensity at 480 nm (Tm{sup 3+}:{sup 1}G{sub 4}->{sup 3}H{sub 6}) and at 800 nm (Tm{sup 3+}:{sup 3}H{sub 4}->{sup 3}H{sub 6}).

  9. van der Waals interactions and dipole polarizabilities of lanthanides: Tm(2F)-He and Yb(1S)-He potentials

    NASA Astrophysics Data System (ADS)

    Buchachenko, Alexei A.; Szcz??niak, Ma?gorzata M.; Cha?asi?ski, Grzegorz

    2006-03-01

    Anisotropic dipole polarizabilities of Tm(F2),Tm+2(F2), and Yb(S1) are calculated using the finite-field multireference averaged quadratic coupled cluster (MR-AQCC) (Tm and Tm+2) and RCCSD(T) (Yb) methods with small-core relativistic pseudopotentials ECP28MWB combined with the augmented ANO basis sets. The lanthanide atoms are strongly polarizable with the scalar part originating from the 6s electrons and the tensorial part from the open 4f shells. The adiabatic interaction potentials ?+2,?2,?2, and ?2 of Tm(F2)-He and Tm+2(F2)-He were examined by the multireference approaches, multireference configuration interaction and MR-AQCC, using the basis sets designed in the polarizability calculations. A closed-shell lanthanide system Yb(S1)-He was included for comparison. The Tm-He ?+2,?2,?2, and ?2 interaction potentials are very shallow and nearly degenerate (within 0.01cm-1), with the well depths in the range of 2.35-2.36cm-1 at R =6.17. The basis-set saturated well depths are expected to be larger by ca. 25%, as estimated using the bond-function augmented basis set. The interactions of lanthanide atoms with He are one order of magnitude less anisotropic than those involving first-row transition metal atoms. The suppression of anisotropy is chiefly attributed to the screening effected by the 6s shell. When these electrons are removed as in the di-cation complex Tm+2(F2)-He, the potentials deepen to a thousand wave number range and their anisotropy is enhanced 500-fold.

  10. Photoemission study of reactive rare-earth/semiconductor interfaces: Tm/GaAs(110) and Yb/GaAs(110)

    SciTech Connect

    Prietsch, M.; Laubschat, C.; Domke, M.; Kaindl, G.

    1988-11-15

    The behavior of interfaces formed by growing thin Tm and Yb films on p- and n-type GaAs(110) substrates at room temperature was investigated by photoemission from As 3d, Ga 3d, and metal 4f core levels. At metal coverages THETA<1 A, the core-level binding energies of substrate atoms are found to be shifted to higher and lower values, respectively, for p- and n-type GaAs; this observation is interpreted as a consequence of band bending due to defect states. In addition, photoemission signals from chemically reacted products at the interface are observed, which grow in intensity with metal coverage. In the coverage range 2Tm and 2.5Yb, a further change in band bending occurs, as reflected in additional shifts of all core levels towards lower binding energies. This observation, together with the strongly increasing density of states at the Fermi level around this coverage, indicates that the Schottky barrier is not established until the overlayer assumes metallic character. These observations are interpreted within the concept of metal-induced gap states defining the final Fermi-level position. From the observed variations with metal coverage of binding energies and relative intensities of photoemission signals from the reacted layer, a structure model is proposed for rare-earth/GaAs(110) interfaces that includes a separation of As and Ga atoms into As-rich and Ga-rich rare-earth compounds in the reacted zone.

  11. Hydrothermal synthesis and upconversion luminescence properties of ?-NaGdF4:Yb3+/Tm3+ and ?-NaGdF4:Yb3+/Ho3+ submicron crystals with regular morphologies.

    PubMed

    Li, Jing; Hao, Zhendong; Zhang, Xia; Luo, Yongshi; Zhao, Jihong; L, Shaozhe; Cao, Jian; Zhang, Jiahua

    2013-02-15

    Single phase ?-NaGdF(4):Yb(3+)/Tm(3+) and ?-NaGdF(4):Yb(3+)/Ho(3+) submicron crystals with various morphologies including hexagonal prisms, spindles, and spheres were synthesized via the one-step hydrothermal method by controlling the pH values and sort of chelators (EDTA and citric acid). The prepared products showed intense up-converted luminescence (UCL) pumped by infrared laser at 980 nm. The hexagonal prisms that meaning high degree crystallinity demonstrated strong UCL in comparison with other morphologies such as spindles and spheres. In ?-NaGdF(4):Yb(3+)/Tm(3+), UCL not only appeared transitions from (1)G(4), (1)D(2), and (1)I(6) states to the lower lying states of Tm(3+), but also (6)P(J)?(8)S(7/2) transition (310 nm) of Gd(3+). These UCL were responsible for three, five, and six photons processes determined by pump power dependence of UCL intensities. The observation of UCL of Gd(3+) implied occurrence of energy transfer from Tm(3+):(1)I(6) to Gd(3+):(6)P(J). PMID:23141700

  12. Synthesis, structure, magnetism, and optical properties of theordered mixed-lanthanide sulfides gamma-LnLn'S3 (Ln=La, Ce; Ln'=Er, Tm,Yb)

    SciTech Connect

    Jin, G.B.; Choi, E.S.; Guertin, R.P.; Brooks, J.S.; Bray, T.H.; Booth, C.H.; Albrecht-Schmitt, T.E.

    2006-12-12

    {gamma}-LnLn{prime}S{sub 3} (Ln = La, Ce; Ln{prime} = Er, Tm, Yb) have been prepared as dark red to black single crystals by the reaction of the respective lanthanides with sulfur in a Sb{sub 2}S{sub 3} flux at 1000 C. This isotypic series of compounds adopts a layered structure that consists of the smaller lanthanides (Er, Tm, and Yb) bound by sulfide in six- and seven-coordinate environments that are connected together by the larger lanthanides (La and Ce) in eight- and nine-coordinate environments. The layers can be broken down into three distinct one-dimensional substructures containing three crystallographically unique Ln{prime} centers. The first of these is constructed from one-dimensional chains of edge-sharing [Ln{prime}S{sub 7}] monocapped trigonal prisms that are joined to equivalent chains via edge-sharing to yield ribbons. There are parallel chains of [Ln{prime}S{sub 6}] distorted octahedra that are linked to the first ribbons through corner-sharing. These latter units also share corners with a one-dimensional ribbon composed of parallel chains of [Ln{prime}S{sub 6}] polyhedra that edge-share both in the direction of chain propagation and with adjacent identical chains. Magnetic susceptibility measurements show Curie-Weiss behavior from 2 to 300 K with antiferromagnetic coupling, and no evidence for magnetic ordering. The {theta}{sub p} values range from -0.4 to -37.5 K, and spin-frustration may be indicated for the Yb-containing compounds. All compounds show magnetic moments substantially reduced from those calculated for the free ions. The optical band gaps for {gamma}-LaLn{prime}S{sub 3} (Ln{prime} = Er, Tm, Yb) are approximately 1.6 eV, whereas {gamma}-CeLn{prime}S{sub 3} (Ln{prime} = Er, Tm, Yb) are approximately 1.3 eV.

  13. Colour emission tunability in Ho3+-Tm3+-Yb3+ co-doped Y2O3 upconverted phosphor

    NASA Astrophysics Data System (ADS)

    Pandey, Anurag; Rai, Vineet Kumar

    2012-12-01

    The frequency upconversion (UC) emission throughout the visible region from the Y2O3:Ho3+-Tm3+-Yb3+ co-doped phosphors synthesized by using low temperature combustion process upon excitation with a diode laser operating at 980 nm have been presented. The colour emission tunability in co-doped phosphor has been observed on increasing the pump power and seen by the naked eyes. The tunability in colour emission has also been visualized by CIE chromaticity diagram. The variation in UC emission intensity of the 1G4 ? 3H6 (Tm3+) and 5F3 ? 5I8 (Ho3+) transitions lying in the blue region has been monitored with increase in the pump power and marked that their ratio can be used to determine the temperature. The developed phosphor has been used to record fingerprints. The observed most intense visible colour emission from the developed material may be used for photodynamic therapy and as an alternative of traditional fluorescent biolabels.

  14. Enhanced Near-Infrared Upconversion Emission of Yb3+-Tm3+ Co-doped Gd2O3 Sub-microrods

    NASA Astrophysics Data System (ADS)

    Xu, D. K.; Liu, C. F.; Yan, J. W.; Ouyang, H. Q.; Yang, S. H.; Zhang, Y. L.

    Lanthanide-doped rare-earth oxides have aroused great interest in display and bio-probe technology due to their excellent luminescent and magnetic performance. In this paper, Gd2O3 sub-microrods (SMRs) with cubic structure are obtained via heat-treatment from gadolinium hydroxides precursor. Upconversion (UC) spectra show intense near-infrared (NIR) emission which is assigned to 3H4 ? 3H6 transition of Tm3+. From the double logarithmic plot of emission intensity versus pump powers, it was seen that typical two photons were involved in the NIR UC process. Moreover, a series of Gd2O3:18%Yb3+,x%Tm3+ (x = 0.1, 0.5, 1, 2, 5) and Gd2O3:y%Yb3+,0.5%Tm3+ (y = 1, 5, 10, 40, 80) SMRs were prepared and characterized to explore their NIR emission properties. Finally, the enhanced NIR emission property was found in Gd2O3:Yb3+,Tm3+ SMRs from the reduced NaOH concentration and the reduced calcinations temperatures.

  15. Study on upconversion luminescence and luminescent dynamics of 20%Yb3+, 0.5%Tm3+ co-doped YF3 and GdF3 nanocrystals.

    PubMed

    Cao, Chunyan; Qin, Weiping; Zhang, Jisen

    2010-03-01

    20%Yb3+, 0.5%Tm3+ co-doped YF3 and GdF3 were synthesized through a facile hydrothermal method. After annealing under an argon atmosphere, the sizes and morphologies of the two samples were characterized by field emission scanning electron microscopy, and the phase and crystallization were analyzed by X-ray diffraction. With a 980 nm continuous wave laser diode as the excitation source, blue and ultraviolet upconversion emissions in the wavelength range of 260-510 nm of Tm3+ and Gd3+/Tm3+ ions were recorded. Under the same excitation conditions, the upconversion emission spectra of the two nanocrystals were compared and analyzed. Gd3+ in the ground state cannot absorb 980 nm photons directly because of the large energy gap between the ground state 8S7/2 and the first excited state 6P7/2. In the 20%Yb3+, 0.5%Tm3+ co-doped GdF3 nanocrystals, the excited states 6I(J) of Gd3+ can be populated through the energy transfer 3P2 --> 3H6 (Tm3+): 8S7/2 --> 6I(J)(Gd3+), meaning that Yb3+ acted as primary sensitizers and Tm3+ acted as secondary sensitizers, transferred energies to host material Gd3+ and resulted in the ultraviolet upconversion emission of the host ions. In this article, the upconversion luminescent dynamics were studied at the onset of a 980 nm pulsed laser from an optical parametric oscillator pumped by a 10 ns pulsed Nd:YAG laser, too. PMID:20355596

  16. Tuning upconversion luminescence of LiYF4:Yb3+,Er3+/Tm3+/Ho3+ microcrystals synthesized through a molten salt process.

    PubMed

    Niu, Na; He, Fei; Wang, Liuzhen; Wang, Lin; Wang, Yan; Gai, Shili; Yang, Piaoping

    2014-05-01

    In this paper, well-defined tetragonal-phase LiYF4:Yb3+,Er3+/Tm3+/Ho3+ micro-crystals with octahedral morphology were successfully prepared through a surfactant-free molten salt process for the first time. By gradually increasing the LiF content in the NaNO3-KNO3 reaction medium, the crystal phase transforms from a mixture of YF3 and LiYF4 to pure tetragonal-phase LiYF4. The possible formation process for the phase and morphology evolution is also presented. Moreover, upon 980 nm laser diode (LD) excitation, the lanthanide ions (Yb3+, Er3+/Tm3+/Ho3+) doped LiYF4 crystals exhibit intense upconversion emission lights. By tuning the sensitizer concentrations of Yb3+ ions in LiYF4:Yb3+,Er3+, the relative intensities of green and red emissions can be precisely adjusted under single wavelength excitation. Consequently, multicolor upconversion emissions can be obtained. On the other hand, UC mechanisms were also given based on the emission spectra and the plot of luminescence intensity to pump power. PMID:24734579

  17. Activation of SO2 with [(?(5) -C5 Me5 )2 Ln(THF)2 ] (Ln=Eu, Yb) leading to dithionite and sulfinate complexes.

    PubMed

    Klementyeva, Svetlana V; Gamer, Michael T; Schmidt, Anna-Corina; Meyer, Karsten; Konchenko, Sergey N; Roesky, Peter W

    2014-10-13

    The reaction of decamethylytterbocene [(?(5) -C5 Me5 )2 Yb(THF)2 ] with SO2 at low temperature gave two new compounds, namely, the Yb(III) dithionite/sulfinate complex [{(?(5) -C5 Me5 )2 Yb(?3 ,1?(2) O(1,3) ,2?(3) O(2,2',4) -S2 O4 )}2 {(?(5) -C5 Me5 )Yb(?,1?O,2?O'-C5 Me5 SO2 )}2 ] (1) and the Yb(III) dithionite complex [{(?(5) -C5 Me5 )2 Yb}2 (?,1?(2) O(1,3) ,2?(2) O(2,4) -S2 O4 )] (2). After extraction of 1, the mixture was heated to give the dinuclear tetrasulfinate complex [{(?(5) -C5 Me5 )Yb}2 (?,?O,?O'-C5 Me5 SO2 )4 ] (3?a). In contrast, from the reaction of [(?(5) -C5 Me5 )2 Eu(THF)2 ] with SO2 only the tetrasulfinate complex [{(?(5) -C5 Me5 )Eu}2 (?,?O,?O'-C5 Me5 SO2 )4 ] (3?b) was isolated. Two major reaction pathways were observed: 1)?reductive coupling of two SO2 molecules to form the dithionite anion S2 O4 (2-) ; and 2)?nucleophilic attack of one metallocene C5 Me5 ligand on the sulfur atom of SO2 . The compounds presented are the first dithionite and sulfinate complexes of the f-elements. PMID:25196130

  18. Spectroscopic analysis of Eu{sup 3+} -and Eu{sup 3+}:Yb{sup 3+}-doped yttrium silicate crystalline powders prepared by combustion synthesis

    SciTech Connect

    Rakov, Nikifor; Amaral, Dayanne F.; Guimaraes, Renato B.; Maciel, Glauco S.

    2010-10-15

    Yttrium silicate powders doped with Eu{sup 3+} and codoped with Eu{sup 3+} and Yb{sup 3+} were prepared by combustion synthesis. The x-ray powder diffraction data showed the presence of Y{sub 2}SiO{sub 5} and Y{sub 2}Si{sub 2}O{sub 7} crystalline phases. Singly doped (1 wt %) sample illuminated with ultraviolet light ({lambda}=256 nm) showed the characteristic red luminescence corresponding to {sup 5}D{sub 0}{yields}{sup 7}F{sub J} transitions of Eu{sup 3+}. The Judd-Ofelt intensity parameters were calculated from experimental data and the radiative and nonradiative relaxation rates were estimated. The results showed that the nonradiative relaxation rate is smaller in yttrium silicate compared to yttrium oxide powder, a reference material, prepared under similar conditions. Codoped samples were exposed to near-infrared laser excitation ({lambda}=975 nm) and the red luminescence of Eu{sup 3+} was also observed. In this case, the luminescence is achieved due to a cooperative upconversion (CUC) process involving energy transfer (ET) from pairs of ytterbium ions to europium ions. The ET rate was estimated by fitting a rate equation model with the dynamics of CUC red emission.

  19. White upconversion emission in Y{sub 2}O{sub 3}:Er{sup 3+}Tm{sup 3+}Yb{sup 3+}phosphor

    SciTech Connect

    Rai, Vineet Kumar; Dey, Riya; Kumar, Kaushal

    2013-06-01

    Graphical abstract: Schematic energy level diagram of Er{sup 3+}Yb{sup 3+}Tm{sup 3+} system upon excitation at 980 nm. Highlights: ? Prepared the Er{sup 3+}Tm{sup 3+}Yb{sup 3+} codoped Y{sub 2}O{sub 3} phosphor. ? Excitation of the sample by 980 nm diode laser is studied. ? Explored the possibility of getting white light emission from the synthesized phosphor. ? Colour tunability of the prepared phosphor is studied. ? Temperature sensing behaviour is investigated using FIR studied. - Abstract: Er{sup 3+}Tm{sup 3+}Yb{sup 3+} codoped Y{sub 2}O{sub 3} phosphor has been synthesized by optimized combustion synthesis process and its white light upconversion emission property is investigated using cheap 980 nm diode laser excitation. Efficient red, green and blue light emission bands, necessary for attaining white light emission, are observed in the codoped sample. The concentration of each rare earth ion is adjusted to get the required emission. In this phosphor, interestingly, emission colour coordinates are found to almost independent on the excitation power density. The temperature sensing behaviour of the prepared samples has also been studied using fluorescence intensity ratio (FIR) technique.

  20. Effect of Li{sup +} ions on enhancement of near-infrared upconversion emission in Y{sub 2}O{sub 3}:Tm{sup 3+}/Yb{sup 3+} nanocrystals

    SciTech Connect

    Li Dongyu; Wang Yuxiao; Zhang Xueru; Dong Hongxing; Shi Guang; Liu Lu; Song Yinglin

    2012-11-01

    Near-infrared (NIR) to NIR upconversion emission is investigated in Tm{sup 3+}/Yb{sup 3+}/Li{sup +} triply doped Y{sub 2}O{sub 3} nanocrystals. Li{sup +} ions doped in Y{sub 2}O{sub 3}:Tm{sup 3+}/Yb{sup 3+} nanocrystals can greatly enhance the NIR upconversion emission intensity of Tm{sup 3+} ions. The abnormal shift of the (222) diffraction peak position determined from x-ray diffraction measurements is discussed, by introducing Li{sup +} ions in the Y{sub 2}O{sub 3}:Tm{sup 3+}/Yb{sup 3+} nanocrystals. The cause of the enhancement is the modification of the local symmetry induced by the Li{sup +} ions, which increases the intra-4f transitions of Tm{sup 3+} ion. Li{sup +} ions doped in Y{sub 2}O{sub 3}:Tm{sup 3+}/Yb{sup 3+} nanocrystals also can reduce the OH groups, dissociate the Yb{sup 3+} and Tm{sup 3+} ion clusters, and create the oxygen vacancies, which are the other reasons for enhancing the upconversion emission intensities. This material may be promising for in vitro and in vivo bioimaging probes.

  1. Eu/sup 2 +/, Yb/sup 2 +/, and Es/sup 2 +/ coordination with sodium tetraphenylborate in water-ethanol solutions

    SciTech Connect

    Mikheev, N.B.; Kulyukhin, S.A.; Rumer, I.A.; Kamenskaya, A.N.

    1988-11-01

    Measurements have been made on the coordination of divalent lanthanoid s and actinoids with sodium tetraphenylborate (NaTPB) in water-ethanol solutions. Ln/sup 2 +/ and An/sup 2 +/ form cationic and neutral complexes. The coordination constants ..beta../sub 1/ and ..beta../sub 2/ have been determine: 6.5 and 25.7 for Yb/sup 2 +/, 1.7 and 52.7 for Eu/sup 2 +/, and 6.2 and 106.4 for Es/sup 2 +/. The trend indicates that the hydrated Es/sup 2 +/ is smaller than Yb/sup 2 +/ and Eu/sup 2 +/.

  2. Plasmonic enhanced emissions from cubic NaYF4:Yb: Er/Tm nanophosphors

    PubMed Central

    Sudheendra, L.; Ortalan, Volkan; Dey, Sanchita; Browning, Nigel D.; Kennedy, I.M.

    2011-01-01

    A metal shell was used in this study to provide significant enhancement of the up-converted emission from cubic NaYF4 nanoparticles, creating a valuable composite material for labeling in biology and other applications use of the cubic form of the material obviates the need to undertake a high temperature transformation to the naturally more efficient hexagonal phase. The NaYF4 matrix contained ytterbium sensitizer and an Erbium (Er) or Thulium (Tm) activator. The particle sizes of the as-synthesized nanoparticles were in the range of 2040 nm with a gold shell thickness of 48 nm. The gold shell was macroscopically amorphous. The synthesis method was based on a citrate chelation. In this approach, we exploited the ability of the citrate ion to act as a reductant and stabilizer. Confining the citrate ion reductant on the nanophosphor surface rather than in the solution was critical to the gold shell formation. The plasmonic shell enhanced the up-conversion emission of Tm from visible and near-infrared regions by up to a factor of 8, in addition to imparting a visible color arising from the plasmon absorption of the gold shell. The up-conversion enhancement observed with Tm and Er were different for similar gold coverages, with local crystal field changes as a possible route to enhance up-conversion emission from high symmetry structural hosts. These novel up-converting nanophosphor particles combine the phosphor and features of a gold shell, providing a unique platform for many biological imaging and labeling applications. PMID:21709812

  3. Influence of the Synthesis Parameters on the Properties of NaYF4:Yb3+,Tm3+ Nanoparticles.

    PubMed

    Plohl, Olivija; Majaron, Boris; Ponikvar-Svet, Maja; Makovec, Darko; Lisjak, Darja

    2015-01-01

    Fluorescent nanoparticles, especially fluorides, have received a great deal of interest due to their optical properties, making them suitable for applications in bio-imaging. For this reason they need to exhibit a superior chemical stability in aqueous media. We have studied the influence of the synthesis parameters on the chemical stability of NaYF(4) nanoparticles co-doped with Yb(3+) and Tm(3+). These nanoparticles have different crystal structures, and were synthesized hydrothermally or with thermal decomposition. The samples were characterized with X-ray diffraction and transmission electron microscopy. The up-conversion fluorescence of nanoparticles dispersed in water was measured at 400-900 nm. The partial dissolution of the fluorine in water was detected with an ion-selective electrode for all the samples. The dissolution of the other constituent ions was analysed with an optical emission spectrometer using inductively coupled plasma. The nanoparticles with a hexagonal crystal structure and sizes of around 20 nm that were synthesized with thermal decomposition showed a superior chemical stability in water together with a superior up-conversion fluorescence yield. PMID:26680706

  4. NIR to blue light upconversion in Tm3+/Yb3+ codoped BaTiO3 tellurite glass

    NASA Astrophysics Data System (ADS)

    Kumari, Astha; Rai, Vineet Kumar

    2015-05-01

    Upconversion is an interesting optical property, generally shown by rare-earth doped materials. This unusual optical behavior shown by these rare-earths doped materials are due to their peculiar atomic configuration and electronic transitions. Here, the Tm3+-Yb3+ codoped BaTiO3 glass with TeO2 as former has been prepared by conventional melt and quench technique and the upconversion property has been investigated with the help of near infrared (NIR) to Visible UC study. The generation of the visible UC bands around ˜ 476 nm, ˜ 653 nm, ˜ 702 nm and one NIR UC band at ˜795 nm are assigned due to the 1G4→ 3H6, 1G4→ 3F4, 3F2→ 3H6 and 3H4→ 3H6 transitions respectively. The generations of these upconversion bands have been discussed in detail with the help of energy level diagram. The colour coordinates corresponding to the prepared material have been shown with the help of CIE chromaticity diagram. These glasses can be very appropriately used in the fabrication of solid state laser and as NIR to blue light upconverter.

  5. Yellow-orange upconversion emission in Eu(3+)-Yb(3+) codoped BaTiO(3) phosphor.

    PubMed

    Kumari, Astha; Rai, Vineet Kumar; Kumar, Kaushal

    2014-06-01

    The Eu(3+)-Yb(3+) codoped BaTiO3 phosphor is prepared via co-precipitation method and its upconversion emission is studied by 980nm diode laser excitation. The X-ray diffraction pattern of the prepared sample showed the tetragonal BaTiO3 phase. The co-doped phosphor showed sharp upconversion emission bands peaking at ?592, ?614, ? 654, ?704 and ?796nm due to the (5)D0?(7)F1, (5)D0?(7)F2, (5)D0?(7)F3, (5)D0?(7)F4 and (5)D0?(7)F6 transitions, respectively of Eu(3+) ions. The sharp band at 489nm is assigned to the (2)F5/2?(2)F7/2 transition of Yb(3+) ion while the broad band around 505nm is assigned to the defect states present in the sample. Based on the available experimental data, the process involved in the UC emissions has been explored and elaborated. PMID:24632162

  6. Multifunctional Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles synthesized by reverse micelle method

    PubMed Central

    Gavrilovi?, Tamara V.; Jovanovi?, Dragana J.; Lojpur, Vesna; Drami?anin, Miroslav D.

    2014-01-01

    Synthesis of Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles in reverse micelles and their multifunctional luminescence properties are presented. Using cyclohexane, Triton X-100, and n-pentanol as the oil, surfactant, and co-surfactant, respectively, crystalline nanoparticles with ~4?nm diameter are prepared at low temperatures. The particle size assessed using transmission electron microscopy is similar to the crystallite size obtained from X-ray diffraction measurements, suggesting that each particle comprises a single crystallite. Eu3+-doped GdVO4 nanoparticles emit red light through downconversion upon UV excitation. Er3+/Yb3+-doped GdVO4 nanoparticles exhibit several functions; apart from the downconversion of UV radiation into visible green light, they act as upconvertors, transforming near-infrared excitation (980?nm) into visible green light. The ratio of green emissions from 2H11/2 ? 2I15/2 and 4S3/2 ? 4I15/2 transitions is temperature dependent and can be used for nanoscale temperature sensing with near-infrared excitation. The relative sensor sensitivity is 1.11%K?1, which is among the highest sensitivities recorded for upconversion-luminescence-based thermometers. PMID:24572638

  7. Multifunctional Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles synthesized by reverse micelle method.

    PubMed

    Gavrilovi?, Tamara V; Jovanovi?, Dragana J; Lojpur, Vesna; Drami?anin, Miroslav D

    2014-01-01

    Synthesis of Eu(3+)- and Er(3+)/Yb(3+)-doped GdVO4 nanoparticles in reverse micelles and their multifunctional luminescence properties are presented. Using cyclohexane, Triton X-100, and n-pentanol as the oil, surfactant, and co-surfactant, respectively, crystalline nanoparticles with ~4?nm diameter are prepared at low temperatures. The particle size assessed using transmission electron microscopy is similar to the crystallite size obtained from X-ray diffraction measurements, suggesting that each particle comprises a single crystallite. Eu(3+)-doped GdVO4 nanoparticles emit red light through downconversion upon UV excitation. Er(3+)/Yb(3+)-doped GdVO4 nanoparticles exhibit several functions; apart from the downconversion of UV radiation into visible green light, they act as upconvertors, transforming near-infrared excitation (980?nm) into visible green light. The ratio of green emissions from (2)H11/2 ? (2)I15/2 and (4)S3/2 ? (4)I15/2 transitions is temperature dependent and can be used for nanoscale temperature sensing with near-infrared excitation. The relative sensor sensitivity is 1.11%K(-1), which is among the highest sensitivities recorded for upconversion-luminescence-based thermometers. PMID:24572638

  8. Multifunctional Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles synthesized by reverse micelle method

    NASA Astrophysics Data System (ADS)

    Gavrilovi?, Tamara V.; Jovanovi?, Dragana J.; Lojpur, Vesna; Drami?anin, Miroslav D.

    2014-02-01

    Synthesis of Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles in reverse micelles and their multifunctional luminescence properties are presented. Using cyclohexane, Triton X-100, and n-pentanol as the oil, surfactant, and co-surfactant, respectively, crystalline nanoparticles with ~4 nm diameter are prepared at low temperatures. The particle size assessed using transmission electron microscopy is similar to the crystallite size obtained from X-ray diffraction measurements, suggesting that each particle comprises a single crystallite. Eu3+-doped GdVO4 nanoparticles emit red light through downconversion upon UV excitation. Er3+/Yb3+-doped GdVO4 nanoparticles exhibit several functions; apart from the downconversion of UV radiation into visible green light, they act as upconvertors, transforming near-infrared excitation (980 nm) into visible green light. The ratio of green emissions from 2H11/2 --> 2I15/2 and 4S3/2 --> 4I15/2 transitions is temperature dependent and can be used for nanoscale temperature sensing with near-infrared excitation. The relative sensor sensitivity is 1.11%K-1, which is among the highest sensitivities recorded for upconversion-luminescence-based thermometers.

  9. Upconversion luminescence and blackbody radiation in tetragonal YSZ co-doped with Tm(3+) and Yb(3+).

    PubMed

    Soares, M R N; Ferro, M; Costa, F M; Monteiro, T

    2015-12-21

    Lanthanide doped inorganic nanoparticles with upconversion luminescence are of utmost importance for biomedical applications, solid state lighting and photovoltaics. In this work we studied the downshifted luminescence, upconversion luminescence (UCL) and blackbody radiation of tetragonal yttrium stabilized zirconia co-doped with Tm(3+) and Yb(3+) single crystals and nanoparticles produced by laser floating zone and laser ablation in liquids, respectively. The photoluminescence (PL) and PL excitation (PLE) were investigated at room temperature (RT). PL spectra exhibit the characteristic lines in UV, blue/green, red and NIR regions of the Tm(3+) (4f(12)) under resonant excitation into the high energy (2S+1)LJ multiplets. Under NIR excitation (980 nm), the samples placed in air display an intense NIR at ∼800 nm due to the (1)G4→(3)H5/(3)H4→(3)H6 transitions. Additionally, red, blue/green and ultraviolet UCL is observed arising from higher excited (1)G4 and (1)D2 multiplets. The power excitation dependence of the UCL intensity indicated that 2-3 low energy absorbed photons are involved in the UCL for low power levels, while for high powers, the identified saturation is dependent on the material size with a enhanced effect on the NPs. The temperature dependence of the UCL was investigated for single crystals and targets used in the ablation. An overall increase of the integrated intensity was found to occur between 12 K and the RT. The thermally activated process is described by activation energies of 10 meV and 30 meV for single crystals and targets, respectively. For the NPs, the UCL was found to be strongly sensitive to pressure conditions. Under vacuum conditions, instead of the narrow lines of the Tm(3+), a wide blackbody radiation was detected, responsible for the change in the emission colour from blue to orange. This phenomenon is totally reversible when the NPs are placed at ambient pressure. The UCL/blackbody radiation in the nanosized material exhibits non-contact pressure colour-based sensor characteristics. Moreover, tuning the color of the blackbody radiation in the nanoparticles by harvesting the low energy photons into the visible spectral region was found to be possible by adjusting the excitation power, paving the way for further developments of these nanoparticles for lighting and photovoltaic applications. PMID:26469333

  10. Upconversion luminescence and blackbody radiation in tetragonal YSZ co-doped with Tm3+ and Yb3+

    NASA Astrophysics Data System (ADS)

    Soares, M. R. N.; Ferro, M.; Costa, F. M.; Monteiro, T.

    2015-11-01

    Lanthanide doped inorganic nanoparticles with upconversion luminescence are of utmost importance for biomedical applications, solid state lighting and photovoltaics. In this work we studied the downshifted luminescence, upconversion luminescence (UCL) and blackbody radiation of tetragonal yttrium stabilized zirconia co-doped with Tm3+ and Yb3+ single crystals and nanoparticles produced by laser floating zone and laser ablation in liquids, respectively. The photoluminescence (PL) and PL excitation (PLE) were investigated at room temperature (RT). PL spectra exhibit the characteristic lines in UV, blue/green, red and NIR regions of the Tm3+ (4f12) under resonant excitation into the high energy 2S+1LJ multiplets. Under NIR excitation (980 nm), the samples placed in air display an intense NIR at ~800 nm due to the 1G4 --> 3H5/3H4 --> 3H6 transitions. Additionally, red, blue/green and ultraviolet UCL is observed arising from higher excited 1G4 and 1D2 multiplets. The power excitation dependence of the UCL intensity indicated that 2-3 low energy absorbed photons are involved in the UCL for low power levels, while for high powers, the identified saturation is dependent on the material size with a enhanced effect on the NPs. The temperature dependence of the UCL was investigated for single crystals and targets used in the ablation. An overall increase of the integrated intensity was found to occur between 12 K and the RT. The thermally activated process is described by activation energies of 10 meV and 30 meV for single crystals and targets, respectively. For the NPs, the UCL was found to be strongly sensitive to pressure conditions. Under vacuum conditions, instead of the narrow lines of the Tm3+, a wide blackbody radiation was detected, responsible for the change in the emission colour from blue to orange. This phenomenon is totally reversible when the NPs are placed at ambient pressure. The UCL/blackbody radiation in the nanosized material exhibits non-contact pressure colour-based sensor characteristics. Moreover, tuning the color of the blackbody radiation in the nanoparticles by harvesting the low energy photons into the visible spectral region was found to be possible by adjusting the excitation power, paving the way for further developments of these nanoparticles for lighting and photovoltaic applications.

  11. "White" phosphor on the basis of Gd2(MoO4)3: Tm,Tb,Eu single crystal

    NASA Astrophysics Data System (ADS)

    Sinitsyn, V. V.; Redkin, B. S.; Kiselev, A. P.; Shmurak, S. Z.; Kolesnikov, N. N.; Kveder, V. V.; Ponyatovsky, E. G.

    2015-08-01

    A single-crystal sample of Gd2(MoO4)3 simultaneously doped with europium, terbium and thulium is grown. The Tm, Tb and Eu dopants are employed as the luminescent centers emitting light in the red, green and blue ranges. Spectroscopy investigation reveals that simultaneous luminescence of the centers of all three types to produce white light occurs only under the sample excitation with ultraviolet (UV) light within the wavelength range 350 < ? < 370 nm. A commercial UV light-emitting diode (LED) with ?LED = 365 nm is applied in order to show that the Gd2(MoO4)3:Tm,Tb,Eu crystal converts its UV flux into white light. So, it is demonstrated that white light may be produced using one matrix with luminous centers of three types.

  12. Cross-relaxation induced tunable emissions from the Tm(3+)/Er(3+)/Eu(3+) ions activated BaGd2O4 nanoneedles.

    PubMed

    Seeta Rama Raju, G; Pavitra, E; Yu, Jae Su

    2014-07-01

    Tm(3+), Er(3+), Tm(3+)/Er(3+), Tm(3+)/Er(3+)/Eu(3+) single, double and triple activator ion/ions doped nanocrystalline BaGd2O4 (BG) phosphors were prepared by a Pechini type sol-gel process. After annealing at 1300 C, X-ray diffraction patterns confirmed their orthorhombic structure. Field-emission transmission electron microscope images of the BG sample indicated a nanoneedle-type morphology. Photoluminescence (PL) and cathodoluminescence (CL) measurements were utilized to establish the emission properties of rare-earth ions doped nanocrystalline BG host lattice. Under near-ultraviolet (NUV) excitations, BG:Tm(3+) and BG:Er(3+) exhibited their characteristic emissions in the blue and green regions, respectively, while BG:Tm(3+)/Er(3+) and BG:Tm(3+)/Er(3+)/Eu(3+) showed cyan and white light emissions, respectively, when doped with appropriate amounts of activator ions. In the PL, the cross-relaxation process is dominant rather than the energy transfer process. Due to the different mechanism from PL, the CL spectra showed different emission features of BG:Tm(3+)/Er(3+)/Eu(3+) phosphor. The CL spectra of BG:Tm(3+) and BG:Er(3+) established the high purity blue and green emissions, respectively. From the PL and CL investigations, the white-light emission was realized from the single-phase BG:Tm(3+)/Er(3+)/Eu(3+) phosphor under NUV and low voltage electron beam excitations. PMID:24846293

  13. Lanthanide stannate pyrochlores Ln{sub 2}Sn{sub 2}O{sub 7} (Ln = Nd, Sm, Eu, Gd, Er, Yb) nanocrystals: Synthesis, characterization, and photocatalytic properties

    SciTech Connect

    Wang, Wanjun; Liang, Shijing; Bi, Jinhong; Yu, Jimmy C.; Wong, Po Keung; Wu, Ling

    2014-08-15

    Highlights: Ln{sub 2}Sn{sub 2}O{sub 7} (Ln = Nd, Sm, Eu, Gd, Er, Yb) are synthesized by hydrothermal method. Light absorption edge shows red shift with decreasing Ln{sup 3+} radius from Nd{sup 3+} to Yb{sup 3+}. Ln{sub 2}Sn{sub 2}O{sub 7} shows increasing photocatalytic activity with the decease of Ln{sup 3+} radius. Electronic configuration reaches 4f{sup 14} under light irradiation may decrease photocatalytic activity. Hydroxyl radicals are detected to be the major reactive species. - Abstract: A series of lanthanide stannate pyrochlores Ln{sub 2}Sn{sub 2}O{sub 7} (Ln = Nd, Sm, Eu, Gd, Er, Yb) nanocrystals have been successfully synthesized via a facile hydrothermal route. With the decrease of Ln{sup 3+} radius, the light absorption edge of the as-prepared Ln{sub 2}Sn{sub 2}O{sub 7} shows a red shift from Nd{sup 3+} to Yb{sup 3+}. Their photocatalytic activities are found to be improved with the decrease of Ln{sup 3+} radius. However, the photocatalytic activity of Yb{sub 2}Sn{sub 2}O{sub 7} is a little lower than Er{sub 2}Sn{sub 2}O{sub 7}, although the Yb{sup 3+} radius is smaller than Er{sup 3+}, which may be attributed to the full-filled electronic configuration (4f{sup 14}) of surface Yb{sup 2+} intermediates (formed by Yb{sup 3+} trapping a photo-excited electron). The crystallite size and surface area play the most important role in determining the activities. Furthermore, hydroxyl radicals are detected to be the major reactive species during the photo-degradation process. Our findings provide insights in the fabrication of highly efficient stannate photocatalysts, thus enlarging the family of photocatalysts available.

  14. Cooperative reduction by Ln(2+) and Cp*(-) ions: synthesis and properties of Sm, Eu, and Yb complexes with 3,6-di-tert-butyl-o-benzoquinone.

    PubMed

    Pushkarevsky, Nikolay A; Ogienko, Mikhail A; Smolentsev, Anton I; Novozhilov, Igor N; Witt, Alexander; Khusniyarov, Marat M; Cherkasov, Vladimir K; Konchenko, Sergey N

    2016-01-01

    The first examples of samarium, europium, and ytterbium complexes with 3,6-di-tert-butyl-o-benzoquinone (3,6-dbbq) in the form of catecholate have been obtained by reactions of the quinone with the corresponding lanthanocenes, (n = 1 or 2) in solution. In the course of the reactions lanthanide ions lose one or two Cp* ligands, which take part in reduction of a quinone molecule into a catecholate anion (dbcat, 2-). As a result of the reactions, Sm and Yb clearly yield dimeric complexes [(LnCp*)2(dbcat)2], where each Ln ion loses one Cp* ligand. Eu forms a trimeric complex [(EuCp*)(Eu·thf)2(dbcat)3], in which one Eu ion is coordinated by one Cp* ligand, while two Eu ions have lost all Cp* ligands and are coordinated by THF molecules instead. Magnetic properties corroborate the assignment of oxidation states made on the basis of single-crystal X-ray diffraction: all the quinone ligands are present in the catecholate state; both Sm/Yb ions in the dimers are in the +3 oxidation state, whereas the Eu trimer contains two Eu(ii) and one Eu(iii) ions. Cyclovoltammetry studies show the presence of two reversible oxidation waves for all complexes, presumably concerned with the redox transitions of the dbcat ligands. PMID:26674171

  15. Investigation on up-conversion luminescence properties of novel transparent Ho3+-Tm3+-Yb3+ co-doped oxyfluoride glass ceramics

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-bo; Han, Wan-lei; Xu, Fang; Song, Ying-lin

    2011-06-01

    In the present letter, the transparent oxyfluoride glass ceramics containing Ho3+-Tm3+-Yb3+:NaYF4 were successfully prepared by melt-quenching at 1400C and subsequent heating at 650-680C for 1~2 hours . X-ray diffraction (XRD) with Cu K? radiation (?=0.154nm) investigation revealed that NaYF4 nano-crystals in the glass ceramics was fabricated. Their sizes were determined by Sherrer's equation. The emission spectra red green and blue up-conversion (UC) under 980nm laser diode (LD) pumping and absorption spectra were measured. Luminescence measurements confirmed the partition of RE ions in nano-crystals NaYF4. The blue red and green UC radiations correspond to the transitions 1G4-3H6, 1G4-3H4 of Tm3+, 5F4, 5S2-5I8, 5F5-5I8, of Ho3+ ions, respectively. This is similar to that in Tm3+-Yb3+ and/or Ho3+-Yb3+ co-doped glass ceramics. To obtain upconversion fluorescence mechanisms, upconversion fluorescence intensity versus LD pump power were analyzed in view of energy levels of rare earth. Up-conversion mechanisms were discussed and the ratio between red, green and blue UC emission bands was found to be varied as a function of temperature of heat treatment and pump power. This result could be mainly attributed to the cross-relaxation between Ho3+ ions. The excellent optical properties and its convenient, low-cost synthesis of the present glass ceramic imply that it is an excellent substitution material for the unobtainable bulk NaYF4 crystal and may have potentially applications in tunable visible laser or many other fields.

  16. Optical properties of trigonal single crystals (Yb,Tm)Al{sub 3}(BO{sub 3}){sub 4} grown from fluxes based on the bismuth and lithium molybdates

    SciTech Connect

    Temerov, V. L. Sokolov, A. E.; Sukhachev, A. L.; Bovina, A. F.; Edel'man, I. S.; Malakhovskii, A. V.

    2008-12-15

    The conditions for synthesis of Yb{sub x}Tm{sub 1-x}Al{sub 3}(BO{sub 3}){sub 4} (x = 0, 0.1, 0.2, 1.0) single crystals from fluxes based on bismuth trimolybdate Bi{sub 2}Mo{sub 3}O{sub 12} and lithium molybdate Li{sub 2}MoO{sub 4} are investigated. It is proposed to grow them by the group method on seeds. The polarized optical absorption spectra are measured for two mutually orthogonal linear polarizations at temperatures of 100 and 300 K.

  17. Depositing CdS nanoclusters on carbon-modified NaYF4:Yb,Tm upconversion nanocrystals for NIR-light enhanced photocatalysis

    NASA Astrophysics Data System (ADS)

    Tou, Meijie; Mei, Yuanyuan; Bai, Song; Luo, Zhenguo; Zhang, Yong; Li, Zhengquan

    2015-12-01

    High-quality hexagonal NaYF4:Yb,Tm upconversion nanocrystals (UCNs) prepared in organic solutions display uniform sizes and strong UC emissions, but they possess a hydrophobic surface which hinders combining them with various semiconductor nanocrystals (NCs) to form a hybrid NIR-activated photocatalyst. Herein we present a facile approach to modify hydrophobic UCNs with a uniform carbon layer and enable them with hydrophilicity and surface functionalization. The carbon shell provides a good substrate for enriching with metal ions and in situ generation of CdS nanoclusters on the particle surface which can utilize both the upconverted UV and visible emissions. The developed NaYF4:Yb,Tm@C@CdS nanoparticles are characterized with TEM, SEM, XRD, PL and UV-Vis spectra and their formation mechanism is elucidated. The products display good photocatalytic activity under visible light and obviously enhanced performance under Vis-NIR light, due to the efficient utilization of UC emissions and the strong adsorption capacity of the carbon shell. The working mechanism of the hybrid photocatalysts is also proposed.High-quality hexagonal NaYF4:Yb,Tm upconversion nanocrystals (UCNs) prepared in organic solutions display uniform sizes and strong UC emissions, but they possess a hydrophobic surface which hinders combining them with various semiconductor nanocrystals (NCs) to form a hybrid NIR-activated photocatalyst. Herein we present a facile approach to modify hydrophobic UCNs with a uniform carbon layer and enable them with hydrophilicity and surface functionalization. The carbon shell provides a good substrate for enriching with metal ions and in situ generation of CdS nanoclusters on the particle surface which can utilize both the upconverted UV and visible emissions. The developed NaYF4:Yb,Tm@C@CdS nanoparticles are characterized with TEM, SEM, XRD, PL and UV-Vis spectra and their formation mechanism is elucidated. The products display good photocatalytic activity under visible light and obviously enhanced performance under Vis-NIR light, due to the efficient utilization of UC emissions and the strong adsorption capacity of the carbon shell. The working mechanism of the hybrid photocatalysts is also proposed. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06806a

  18. Broadband down-conversion based near infrared quantum cutting in Eu2+-Yb3+ co-doped SrAl2O4 for crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Tai, Yuping; Zheng, Guojun; Wang, Hui; Bai, Jintao

    2015-03-01

    Near infrared (NIR) quantum cutting involving the down conversion of an absorbed visible photon to emission of two NIR photons was achieved in SrAl2O4:0.01Eu2+, xYb3+ (x=0, 1, 2, 5, 10, 20, 30 mol%) samples. The photoluminescence properties of samples in visible and NIR regions were measured to verify the energy transfer (ET) from Eu2+ to Yb3+. The results demonstrated that Eu2+ was an efficient sensitizer for Yb3+ in the SrAl2O4 host lattice. According to Gaussian fitting analysis and temperature-dependent luminescence experiments, the conclusion was drawn that the cooperative energy transfer (CET) process dominated the ET process and the influence of charge transfer state (CTS) of Yb3+ could be negligible. As a result, the high energy transfer efficiency (ETE) and quantum yield (QY) have been acquired, the maximum value approached 73.68% and 147.36%, respectively. Therefore, this down-conversion material has potential application in crystalline silicon solar cells to improve conversion efficiency.

  19. Influence of surfactants on the morphology, upconversion emission, and magnetic properties of ?-NaGdF4:Yb3+,Ln3+ (Ln = Er, Tm, Ho).

    PubMed

    He, Fei; Niu, Na; Wang, Lin; Xu, Jie; Wang, Yan; Yang, Guixin; Gai, Shili; Yang, Piaoping

    2013-07-21

    In this article, rare earth (RE) ion doped ?-NaGdF4 crystals with multicolor up-conversion (UC) emissions and paramagnetic properties were synthesized via a simple one-step precipitation method at room-temperature for the first time. Different surfactants, including Na2EDTA, PVP, SDS, and Na2tar, were introduced to control the crystal size and morphology. It was found that the organic additive can strongly control the size and structure of as-prepared ?-NaGdF4:Yb(3+),Ln(3+) samples through absorbing on the surface of primary particles and/or coordinating with RE(3+) ions. Most interestingly, the UC and magnetic properties of the NaGdF4 crystals were also greatly influenced by those additives, which exhibit great distinction. The red emission of (4)F(9/2)?(4)I(15/2) (655 nm) in ?-NaGdF4:20%Yb(3+),2%Er(3+), (5)F5?(5)I8 (648 nm) in ?-NaGdF4:20%Yb(3+),2%Ho(3+), and NIR emission of (3)H4?(3)H6 (797 nm) in ?-NaGdF4:20%Yb(3+),2%Tm(3+) were all markedly enhanced due to abundant organic groups that affect the nonradiative processes. The magnetic properties of ?-NaGdF4:Yb(3+),Er(3+) crystals prepared with different surfactants exhibit typical paramagnetic behavior with different intensities due to the different crystal shape anisotropy. PMID:23715476

  20. High Contrast In vitro and In vivo Photoluminescence Bioimaging Using Near Infrared to Near Infrared Up-Conversion in Tm3+ and Yb3+ Doped Fluoride Nanophosphors

    PubMed Central

    Nyk, Marcin; Kumar, Rajiv; Ohulchanskyy, Tymish Y.; Bergey, Earl J.; Prasad, Paras N.

    2012-01-01

    A new approach for photoluminescence imaging in vitro and in vivo has been shown, utilizing near infrared to near infrared (NIR-to-NIR) up-conversion in nanophosphors. This NIR-to-NIR up-conversion process provides deeper light penetration into biological specimen and results in high contrast optical imaging due to absence of an autofluorescence background and decreased light scattering. Aqueous dispersible fluoride (NaYF4) nanocrystals (2030 nm size) co-doped with the rare earth ions, Tm3+ and Yb3+, were synthesized and characterized by TEM, XRD and photoluminescence (PL) spectroscopy. In vitro cellular uptake was shown by the PL microscopy visualizing the characteristic emission of Tm3+ at ~ 800 nm excited with 975 nm. No apparent cytotoxicity was observed. Subsequent animal imaging studies were performed using Balb-c mice injected intravenously with up-converting nanophosphors, demonstrating the high contrast PL imaging in vivo. PMID:18928324

  1. High contrast in vitro and in vivo photoluminescence bioimaging using near infrared to near infrared up-conversion in Tm3+ and Yb3+ doped fluoride nanophosphors.

    PubMed

    Nyk, Marcin; Kumar, Rajiv; Ohulchanskyy, Tymish Y; Bergey, Earl J; Prasad, Paras N

    2008-11-01

    A new approach for photoluminescence imaging in vitro and in vivo has been shown utilizing near infrared to near infrared (NIR-to-NIR) up-conversion in nanophosphors. This NIR-to-NIR up-conversion process provides deeper light penetration into biological specimen and results in high contrast optical imaging due to absence of an autofluorescence background and decreased light scattering. Aqueous dispersible fluoride (NaYF4) nanocrystals (20-30 nm size) co-doped with the rare earth ions, Tm(3+) and Yb(3+), were synthesized and characterized by TEM, XRD, and photoluminescence (PL) spectroscopy. In vitro cellular uptake was shown by the PL microscopy visualizing the characteristic emission of Tm(3+) at approximately 800 nm excited with 975 nm. No apparent cytotoxicity was observed. Subsequent animal imaging studies were performed using Balb-c mice injected intravenously with up-converting nanophosphors, demonstrating the high contrast PL imaging in vivo. PMID:18928324

  2. Multicolour upconversion emission from Ho{sup 3+}-Tm{sup 3+}-Yb{sup 3+} codoped CaMoO{sub 4} phosphor

    SciTech Connect

    Dey, Riya; Rai, Vineet Kumar

    2015-05-15

    The Ho{sup 3+}-Tm{sup 3+}-Yb{sup 3+} codoped CaMoO4 phosphor powder has been synthesized by chemical coprecipitation technique. For the structural investigation the X-ray diffraction analysis has been done. Multicolour upconversion (UC) emission in the visible region from the prepared material has been observed under the 980?nm near infrared (NIR) excitation. The UC emission bands ? 474?nm (blue), ? 541?nm (green) and ? 661?nm (red) region have been assigned as {sup 1}G{sub 4}?{sup 3}H{sub 6} (Tm{sup 3+}), {sup 5}F{sub 4}{sup 5}S{sub 2}?{sup 5}I{sub 8} (Ho{sup 3+}) and {sup 5}F{sub 5}?{sup 5}I{sub 8} (Ho{sup 3+}) transitions respectively.

  3. Enhancing upconverted white light in Tm3+/Yb3+/Ho3+-doped GdVO4 nanocrystals via incorporation of Li+ ions.

    PubMed

    Mahalingam, Venkataramanan; Naccache, Rafik; Vetrone, Fiorenzo; Capobianco, John A

    2012-01-01

    The white light emission of Tm3+/Yb3+/Ho3+-doped GdVO4 nanocrystals, following excitation with near-infrared light (?exc = 980 nm), via a multiphoton upconversion process is presented. Upconverted blue emission from the Tm3+ ions as well as green/red emissions from the Ho3+ ions contributes to the observed white light. The calculated Commission internationale de l'clairage (CIE) color coordinates were calculated to be x = 0.34; y = 0.32 and lie at the center of the white region. Furthermore, the intensity of the upconverted white light was enhanced by the incorporation of monovalent Li+ ions into the GdVO4 matrix. An explanation for this enhancement is proposed based on X-ray diffraction and fluorescence lifetime measurements. PMID:22274334

  4. An experimental design approach for hydrothermal synthesis of NaYF4: Yb3+, Tm3+ upconversion microcrystal: UV emission optimization

    NASA Astrophysics Data System (ADS)

    Kaviani Darani, Masoume; Bastani, Saeed; Ghahari, Mehdi; Kardar, Pooneh

    2015-11-01

    Ultraviolet (UV) emissions of hydrothermally synthesized NaYF4: Yb3+, Tm3+ upconversion crystals were optimized using the response surface methodology experimental design. In these experimental designs, 9 runs, two factors namely (1) Tm3+ ion concentration, and (2) pH value were investigated using 3 different ligands. Introducing UV upconversion emissions as responses, their intensity were separately maximized. Analytical methods such as XRD, SEM, and FTIR could be used to study crystal structure, morphology, and fluorescent spectroscopy in order to obtain luminescence properties. From the photo-luminescence spectra, emissions centered at 347, 364, 452, 478, 648 and 803 nm were observed. Some results show that increasing each DOE factor up to an optimum value resulted in an increase in emission intensity, followed by reduction. To optimize UV emission, as a final result to the UV emission optimization, each design had a suggestion.

  5. Facile fabrication and upconversion luminescence enhancement of LaF3:Yb3+/Ln3+@SiO2 (Ln = Er, Tm) nanostructures decorated with Ag nanoparticles.

    PubMed

    He, Enjie; Zheng, Hairong; Dong, Jun; Gao, Wei; Han, Qingyan; Li, Junna; Hui, Le; Lu, Ying; Tian, Huani

    2014-01-31

    A novel hybrid nanostructure, that is a Ag nanoparticle decorated LaF(3):Yb(3+)/Ln(3+)@SiO(2) nanosphere (Ln=Er, Tm), was constructed by a facile strategy, and characterized by XRD, TEM, FTIR, XPS and UV-vis-NIR absorption. Obvious spectral broadening and red-shift on the surface plasmon resonance were obtained by adjusting the size and configuration of Ag nanoparticles. Effective upconversion luminescence enhancements for Er(3+) and Tm(3+) containing samples were obtained. It is suggested that the luminescence enhancement results from both the excitation and emission processes, and the configuration of the studied hybrid nanostructure is an efficient system to enhance the luminescence emission of rare earth doped nanomaterials. It is believed that the enhancement from the hybrid nanostructure will find great potential in the development of photovoltaic solar cells. PMID:24398901

  6. Intense upconversion luminescence and effect of local environment for Tm3+/Yb3+ co-doped novel TeO2-BiCl3 glass system.

    PubMed

    Wang, Guonian; Dai, Shixun; Zhang, Junjie; Wen, Lei; Yang, Jianhu; Jiang, Zhonghong

    2006-05-15

    We present the results of a study that uses theoretical and experimental methods to investigate the characteristics of the upconversion luminescence of Tm3+/Yb3+ codoped TeO2-BiCl3 glass system as a function of the BiCl3 fraction. These glasses are potentially important in the design of upconversion fiber lasers. Effect of local environment around Tm3+ on upconversion fluorescence intensity was analyzed by theoretical calculations. The structure and spectroscopic properties were investigated in the experiments by measuring the Raman spectra, IR transmission spectra, and absorption and fluorescence intensities at room temperature. The results indicate that blue luminescence quantum efficiency increases with increasing BiCl3 content from 10 to 60 mol%, which were interpreted by the increase of asymmetry of glass structure, decrease of phonon energy and removing of OH- groups. PMID:16378753

  7. Synthesis, crystal structures, magnetic and electric transport properties of Eu{sub 11}InSb{sub 9} and Yb{sub 11}InSb{sub 9}

    SciTech Connect

    Xia Shengqing; Hullmann, Jonathan; Bobev, Svilen Ozbay, Arif; Nowak, Edmund R.; Fritsch, Veronika

    2007-07-15

    Two new rare-earth metal containing Zintl phases, Eu{sub 11}InSb{sub 9} and Yb{sub 11}InSb{sub 9} have been synthesized by reactions of the corresponding elements in molten In metal to serve as a self-flux. Their crystal structures have been determined by single crystal X-ray diffraction-both compounds are isostructural and crystallize in the orthorhombic space group Iba2 (No. 45), Z=4 with unit cell parameters a=12.224(2) A, b=12.874(2) A, c=17.315(3) A for Eu{sub 11}InSb{sub 9}, and a=11.7886(11) A, b=12.4151(12) A, c=16.6743(15) A for Yb{sub 11}InSb{sub 9}, respectively (Ca{sub 11}InSb{sub 9}-type, Pearson's code oI84). Both structures can be rationalized using the classic Zintl rules, and are best described in terms of discrete In-centered tetrahedra of Sb, [InSb{sub 4}]{sup 9-}, isolated Sb dimers, [Sb{sub 2}]{sup 4-}, and isolated Sb anions, Sb{sup 3-}. These anionic species are separated by Eu{sup 2+} and Yb{sup 2+} cations, which occupy the empty space between them and counterbalance the formal charges. Temperature-dependent magnetic susceptibility and resistivity measurements corroborate such analysis and indicate divalent Eu and Yb, as well as poorly metallic behavior for both Eu{sub 11}InSb{sub 9} and Yb{sub 11}InSb{sub 9}. The close relationships between these structures and those of the monoclinic {alpha}-Ca{sub 21}Mn{sub 4}Sb{sub 18} and Ca{sub 21}Mn{sub 4}Bi{sub 18} are also discussed. - Graphical abstract: Reported are the synthesis, the structure and the magnetic and electronic properties of two new rare-earth Zintl phases, Eu{sub 11}InSb{sub 9} and Yb{sub 11}InSb{sub 9}. The close relationships between these structures and those of the monoclinic {alpha}-Ca{sub 21}Mn{sub 4}Sb{sub 18} and Ca{sub 21}Mn{sub 4}Bi{sub 18} are also discussed.

  8. Enhanced near-infrared response of CdS/CdTe solar cell using Tm3+ and Yb3+ co-doped upconverting glass phosphors

    NASA Astrophysics Data System (ADS)

    Pan, Z.; Whyte, D.; Morgan, S. H.; Li, J.; Alaswad, A.; Beach, J. D.; Ohno, T. R.; Wolden, C. A.

    2014-10-01

    Tm3+ and Yb3+ co-doped upconverting (UC) glass phosphors were used to converting near-infrared to visible light and input to a CdS/CdTe solar cell, therefore to enhance solar cell's response in the near-infrared of the sub-bandgap region. Current-voltage measurements were performed on the solar cell with a UC glass phosphor. A short-circuit photocurrent enhancement of 31 ?A was obtained using a Tm3+and Yb3+ co-doped glass UC phosphor, illuminated by a 980 nm diode laser at 100 mW. This photocurrent response corresponds to external quantum efficiency (EQE) of 0.04 % at 980 nm. For full collection of the UC light in 4? solid angle, the EQE value is expected to reach 1.6 %. The photo-current observed was proportional to the effective UC light intensity from glass UC phosphor. A non-linear relation between the output photo-current and the incident power of the infrared light was observed, similar to the relation between UC intensity and the incident power. UC efficiency of the glass phosphor was calculated using EQE values at both UC wavelengths and at 980 nm.

  9. Depositing CdS nanoclusters on carbon-modified NaYF4:Yb,Tm upconversion nanocrystals for NIR-light enhanced photocatalysis.

    PubMed

    Tou, Meijie; Mei, Yuanyuan; Bai, Song; Luo, Zhenguo; Zhang, Yong; Li, Zhengquan

    2015-12-17

    High-quality hexagonal NaYF4:Yb,Tm upconversion nanocrystals (UCNs) prepared in organic solutions display uniform sizes and strong UC emissions, but they possess a hydrophobic surface which hinders combining them with various semiconductor nanocrystals (NCs) to form a hybrid NIR-activated photocatalyst. Herein we present a facile approach to modify hydrophobic UCNs with a uniform carbon layer and enable them with hydrophilicity and surface functionalization. The carbon shell provides a good substrate for enriching with metal ions and in situ generation of CdS nanoclusters on the particle surface which can utilize both the upconverted UV and visible emissions. The developed NaYF4:Yb,Tm@C@CdS nanoparticles are characterized with TEM, SEM, XRD, PL and UV-Vis spectra and their formation mechanism is elucidated. The products display good photocatalytic activity under visible light and obviously enhanced performance under Vis-NIR light, due to the efficient utilization of UC emissions and the strong adsorption capacity of the carbon shell. The working mechanism of the hybrid photocatalysts is also proposed. PMID:26647306

  10. Effect of temperature on luminescent properties of an antimony-silicate glass co-doped with Yb3+ and Tm3+

    NASA Astrophysics Data System (ADS)

    Czajkowski, Karol; Kochanowicz, Marcin; Zmojda, Jacek; Dorosz, Dominik; Ragin, Tomasz; Miluski, Piotr

    2013-10-01

    In the article effect of temperature on luminescent properties of antimony - silicate glass co - doped with 1.0mol%Yb3+/1mol%0.2Tm3+ under 976 nm was investigated. As a result of optical excitation with radiation with the wavelength of 976 nm three luminescence bands were obtained: 477 nm for 1G4?3H6 quantum transition, 650 nm for 1G4?3F4 and 698 nm for 3F2,3?3H6 in thulium ions, formed by the efficient Yb3+ ? Tm3+ energy transfer. It has been found that the increase in temperature of a glass leads to higher probability of phonon transitions from the 1G4 to the 3F2,3 level leading to quenching of luminescence band with the wavelength within the band of 650 nm. The maximum sensitivity to temperature change is 0.02139 [K-1] at 250C. The nature of a change over a range of studied temperature from 5 to 250C is linear. The results of the research indicate that the fabricated glass can be used to construct luminescence temperature sensors.

  11. Hydrothermal synthesis of NaLuF4:153Sm,Yb,Tm nanoparticles and their application in dual-modality upconversion luminescence and SPECT bioimaging.

    PubMed

    Yang, Yang; Sun, Yun; Cao, Tianye; Peng, Juanjuan; Liu, Ying; Wu, Yongquan; Feng, Wei; Zhang, Yingjian; Li, Fuyou

    2013-01-01

    Upconversion luminescence (UCL) properties and radioactivity have been integrated into NaLuF(4):(153)Sm,Yb,Tm nanoparticles by a facile one-step hydrothermal method, making these nanoparticles potential candidates for UCL and single-photon emission computed tomography (SPECT) dual-modal bioimaging invivo. The introduction of small amount of radioactive (153)Sm(3+) can hardly vary the upconversion luminescence properties of the nanoparticles. The as-designed nanoparticles showed very low cytotoxicity, no obvious tissue damage in 7 days, and excellent invitro and invivo performances in dual-modal bioimaging. By means of a combination of UCL and SPECT imaging invivo, the distribution of the nanoparticles in living animals has been studied, and the results indicated that these particles were mainly accumulated in the liver and spleen. Therefore, the concept of (153)Sm(3+)/Yb(3+)/Tm(3+) co-doped NaLuF(4) nanoparticles for UCL and SPECT dual-modality imaging invivo of whole-body animals may serve as a platform for next-generation probes for ultra-sensitive molecular imaging from the cellular scale to whole-body evaluation. It also introduces an easy methodology to quantify invivo biodistribution of nanomaterials which still needs further understanding as a community. PMID:23117216

  12. Enhanced photocatalytic activities of the heterostructured upconversion photocatalysts with cotton mediated on TiO2/ZnWO4:Yb3+,Tm3.

    PubMed

    Feng, Kaili; Huang, Shouqiang; Lou, Ziyang; Zhu, Nanwen; Yuan, Haiping

    2015-08-14

    To improve the photocatalytic efficiency and make full use of solar energy, ZnWO(4):Yb(3+),Tm(3+) (ZYT) was introduced as the upconversion luminescence agent on TiO(2) with a cotton template, and novel upconversion photocatalysts of TiO(2)/ZnWO(4):Yb(3+),Tm(3+) (TZYT-C) were synthesized and optimized with 5%-30% of ZYT. The heterostructure between ZYT and TiO(2) was formed in the TZYT-C composites with the presence of tube-like morphologies due to the addition of the cotton template. UV (364 nm) and blue (484 nm) light was emitted from ZYT upon 980 nm NIR irradiation. The BET specific surface areas of all the TZYT-C composites increased from 37 m(2) g(-1) (TiO(2)-C) to the maximum value of 75 m(2) g(-1) on 5%TZYT-C. The photocatalytic activities of the TZYT-C composites were tested using the degradation process of methyl orange (MO). 5%TZYT-C showed the highest degradation efficiency, with a value of 55.6% under sun-like irradiation for 210 min. The same performance was observed on 5%TZYT-C under NIR (? ? 780 nm) irradiation, with a maximum removal rate of 9.02%, since 5%TZYT-C showed the most efficient electron-hole (e(-)/h(+)) pair separation, compared to ZYT and other TZYT-C composites. PMID:26150279

  13. Toward NIR driven photocatalyst: Fabrication, characterization, and photocatalytic activity of ?-NaYF4:Yb(3+),Tm(3+)/g-C3N4 nanocomposite.

    PubMed

    Huang, Min-Zhong; Yuan, Baoling; Dai, Leyang; Fu, Ming-Lai

    2015-12-15

    The ?-NaYF4:Yb(3+),Tm(3+)/g-C3N4 (NYT/C3N4) photocatalyst has been successfully fabricated by a stepwise method. Firstly, the advanced near-infrared (NIR) driven photocatalyst was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV-Vis-NIR diffuse reflectance spectroscopy. It was found that NYT/C3N4 photocatalyst consisted of uniform hexagonal phase NaYF4 nanocrystals with about 20nm diameter distributed on surface of g-C3N4 sheets, and the NYT/C3N4 composite exhibited strong near-infrared light absorption and the energy transfer from ?-NaYF4:Yb(3+),Tm(3+) to g-C3N4 was confirmed. Secondly, the photocatalytic activities of the catalysts were evaluated by the degradation of methyl blue dye and colorless phenol under the irradiation of 980nm laser. The results suggested that NYT/C3N4 nanocomposite is an advanced NIR-driven photocatalyst. Moreover the NYT/C3N4 photocatalyst showed good stability for photocatalytic decoloration of dye in the recycled tests. This study suggested a promising system to utilize the NIR energy of sunlight for photochemical and photoelectrical applications based on g-C3N4, which will contribute to the utilization of solar energy in the future. PMID:26343979

  14. Honeycombs of triangles and magnetic frustration in SrL{sub 2}O{sub 4} (L=Gd, Dy, Ho, Er, Tm, and Yb)

    SciTech Connect

    Karunadasa, H.; Regan, K.A.; Cava, R.J.; Huang, Q.; Lynn, J.W.; Ueland, B.G.; Schiffer, P.

    2005-04-01

    The crystal structures, magnetic order, and susceptibility have been investigated for magnetically frustrated SrDy{sub 2}O{sub 4}, SrHo{sub 2}O{sub 4}, SrEr{sub 2}O{sub 4}, SrTm{sub 2}O{sub 4}, and SrYb{sub 2}O{sub 4}. Powder neutron-diffraction structural refinements reveal columns of LO{sub 6} octahedra that run along one crystallographic direction, with Sr-O polyhedra in the interstices. The lanthanide sublattice displays multiple triangular interconnections: one-dimensional strings form the backbones of four types of chains of lanthanide triangles sharing edges arranged in a honeycomb pattern. This crystal structure produces strong geometric frustration for the magnetic system that is evidenced in both magnetic susceptibility and neutron-scattering data at low temperatures. The susceptibility measurements for the series, including SrGd{sub 2}O{sub 4} for which data are also reported, lack the sharp features characteristic of three-dimensional long-range magnetic ordering. Metamagnetic behavior is observed in the magnetization vs applied field data at 1.8 K for the cases of L=Dy, Er, and Ho. Magnetic neutron-scattering studies for the Dy and Er materials show only very broad magnetic scattering at low temperatures, while the Ho system exhibits long-range two-dimensional order. Any magnetic scattering in the Tm and Yb compounds, if present, was too weak to be detected in these measurements.

  15. Structural Characterization and Polymorphism of R2BaNiO 5 ( R = Nd, Gd, Dy, Y, Ho, Er, Tm, Yb) Studied by Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Garca-Matres, E.; Martnez, J. L.; Rodrguez-Carvajal, J.; Alonso, J. A.; Salinas-Snchez, A.; Saez-Puche, R.

    1993-04-01

    The family of compounds R2BaNiO 5 ( R = Nd, Dy, Y, Ho, Er, Tm, Yb) has been studied by neutron powder diffraction at room temperature. All of them present, orthorhombic symmetry (space group Immm , Z = 2). The main feature of these materials is the existence of one-dimesional chains of vertex-sharing NiO 6 octahedra along the a-axis. The present research has revealed the effect of the size of the rare earth ions on the structural parameters, which plays a role nearly equivalent to a hydrostatic "chemical pressure" in the geometric distortion of the structure. The volume or the Ni and Ba polyhedra varies linearly vs the ionic radius of the rare earth. The overall agreement between the valence bond sums and formal charges is very poor. This fact indicates that the present structure is under very high internal stress and may be metastable. We speculate that there may exist a dimorphism in the other members of this family of oxides, similar to that already found for the Tm, Yb, and Lu compounds.

  16. Separation of the contributions to the magnetization of Tm1 - x Yb x B12 solid solutions in steady and pulsed magnetic fields

    NASA Astrophysics Data System (ADS)

    Bogach, A. V.; Sluchanko, N. E.; Glushkov, V. V.; Demishev, S. V.; Azarevich, A. N.; Filippov, V. B.; Shitsevalova, N. Yu.; Levchenko, A. V.; Vanacken, J.; Moshchalkov, V. V.; Gabani, S.; Flachbart, K.

    2013-05-01

    The magnetization of substitutional Tm1 - x Yb x B12 solid solutions is studied in the composition range 0 < x ? 0.81. The measurements are performed at low temperatures (1.9-300 K) in steady (up to 11 T) and pulsed (up to 50 T, pulse duration of 20-100 ms) magnetic fields. An analysis of the experimental data allowed the contributions to the magnetization of the paramagnetic phase of the Tm1 - x Yb x B12 compounds to be separated. These contributions include a Pauli component, which corresponds to the response of the heavy-fermion manybody states that appears in the energy gap in the vicinity of the Fermi level (density of states (3-4) 1021 cm-3 meV-1), and a contribution with saturation in high magnetic fields attributed to the localized magnetic moments ((0.8-3.7)?B per unit cell) of the nanoclusters formed by rare-earth ions with an antiferromagnetic interaction.

  17. Effect of C6+ Ion Irradiation on structural and electrical properties of Yb and Eu doped Bi1.5 Zn0.92 Nb1.5 O6.92 pyrochlores

    NASA Astrophysics Data System (ADS)

    Yumak, Mehmet; Mergen, Ayhan; Qureshi, Anjum; Singh, N. L.

    2015-03-01

    Pyrochlore general formula of A2B2X7 where A and B are cations and X is an anion Pyrochlore compounds exhibit semiconductor, metallic or ionic conduction properties, depending on the doping, compositions/ substituting variety of cations and oxygen partial pressure. Ion beam irradiation can induce the structural disordering by mixing the cation and anion sublattices, therefore we aim to inevestigate effects of irradiation in pyrochlore compounds. In this study, Eu and Yb-doped Bi1.5Zn0.92Nb1.5O6.92 (Eu-BZN, Yb-BZN) Doping effect and single phase formation of Eu-BZN, Yb-BZN was characterized by X-ray diffraction technique (XRD). Radiation-induced effect of 85 MeV C6+ ions on Eu-BZN, Yb-BZN was studied by XRD, scanning electron microscopy (SEM) and temperature dependent dielectric measurements at different fluences. XRD results revealed that the ion beam-induced structural amorphization processes in Eu-BZN and Yb-BZN structures. Our results suggested that the ion beam irradiation induced the significant change in the temprature depndent dielectric properties of Eu-BZN and Yb-BZN pyrochlores due to the increased oxygen vacancies as a result of cation and anion disordering. Department of Metallurgical and Materials Eng., Marmara University, Istanbul-81040, Turkey.

  18. Enhancement of near-infrared to near-infrared upconversion luminescence in sub-10-nm ultra-small LaF3:Yb3+/Tm3+ nanoparticles through lanthanide doping.

    PubMed

    Huang, Xiaoyong

    2015-11-15

    In this Letter, I present a versatile strategy to enhance the near-infrared to near-infrared (NIR-to-NIR) upconversion luminescence from sub-10-nm ultra-small LaF3:Yb3+/Tm3+ colloidal nanoparticles through lanthanide doping under 980nm laser excitation. It is interesting that the NIR-to-NIR upconversion emission at 801nm of LaF3:Yb3+/Tm3+ nanoparticles can be improved by increasing the Tm3+ doping concentration or by introducing another lanthanide activator (Er3+ or Ho3+) as a sensitizer. The luminescence enhancement effect showed a strong dependence on the doping concentrations of activator ions (Tm3+, Er3+, or Ho3+). Particularly, adding 1mol. % Ho3+ ions into LaF3:Yb3+/Tm3+ nanoparticles induced a 2.85-fold enhancement in NIR 801nm emission of Tm3+ ions. The related upconversion emission mechanisms were investigated and discussed. PMID:26565842

  19. The action mechanism of TiO{sub 2}:NaYF{sub 4}:Yb{sup 3+},Tm{sup 3+} cathode buffer layer in highly efficient inverted organic solar cells

    SciTech Connect

    Liu, Chunyu; Chen, Huan; Zhao, Dan; Shen, Liang; He, Yeyuan; Guo, Wenbin E-mail: chenwy@jlu.edu.cn; Chen, Weiyou E-mail: chenwy@jlu.edu.cn

    2014-08-04

    We report the fabrication and characteristics of organic solar cells with 6.86% power conversion efficiency (PCE) by doping NaYF{sub 4}:Yb{sup 3+},Tm{sup 3+} into TiO{sub 2} cathode buffer layer. The dependence of devices performance on doping concentration of NaYF{sub 4}:Yb{sup 3+},Tm{sup 3+} is investigated. Results indicate that short-circuit current density (J{sub sc}) has an apparent improvement, leading to an enhancement of 22.7% in PCE for the optimized doping concentration of 0.05 mmol ml{sup −1} compared to the control devices. NaYF{sub 4}:Yb{sup 3+},Tm{sup 3+} nanoparticles (NPs) can play threefold roles, one is that the incident light in visible region can be scattered by NaYF{sub 4} NPs, the second is that solar irradiation in infrared region can be better utilized by Up-conversion effect of Yb{sup 3+} and Tm{sup 3+} ions, the third is that electron transport property in TiO{sub 2} thin film can be greatly improved.

  20. Vacuum ultraviolet and near-infrared excited luminescence properties of Ca{sub 3}(PO{sub 4}){sub 2}:RE{sup 3+}, Na{sup +} (RE=Tb, Yb, Er, Tm, and Ho)

    SciTech Connect

    Zhang Jia; Wang Yuhua; Guo Linna; Zhang Feng; Wen Yan; Liu Bitao; Huang Yan

    2011-08-15

    Tb{sup 3+}, Yb{sup 3+}, Tm{sup 3+}, Er{sup 3+}, and Ho{sup 3+} doped Ca{sub 3}(PO{sub 4}){sub 2} were synthesized by solid-state reaction, and their luminescence properties were studied by spectra techniques. Tb{sup 3+}-doped samples can exhibit intense green emission under VUV excitation, and the brightness for the optimal Tb{sup 3+} content is comparable with that of the commercial Zn{sub 2}SiO{sub 4}:Mn{sup 2+} green phosphor. Under near-infrared laser excitation, the upconversion luminescence spectra of Yb{sup 3+}, Tm{sup 3+}, Er{sup 3+}, and Ho{sup 3+} doped samples demonstrate that the red, green, and blue tricolored fluorescence could be obtained by codoping Yb{sup 3+}-Ho{sup 3+}, Yb{sup 3+}-Er{sup 3+}, and Yb{sup 3+}-Tm{sup 3+} in Ca{sub 3}(PO{sub 4}){sub 2}, respectively. Good white upconversion emission with CIE chromaticity coordinates (0.358, 0.362) is achieved by quadri-doping Yb{sup 3+}-Tm{sup 3+}-Er{sup 3+}-Ho{sup 3+} in Ca{sub 3}(PO{sub 4}){sub 2}, in which the cross-relaxation process between Er{sup 3+} and Tm{sup 3+}, producing the {sup 1}D{sub 2}-{sup 3}F{sub 4} transition of Tm{sup 3+}, is found. The upconversion mechanisms are elucidated through the laser power dependence of the upconverted emissions and the energy level diagrams. - Graphical abstract: The CPO:0.25Tb{sup 3+}, 0.25Na{sup +} exhibits a comparable brightness to the commercial Zn{sub 2}SiO{sub 4}:Mn{sup 2+} upon 147 nm excitation. Good white light color is achieved in CPO:Yb{sup 3+}-Tm{sup 3+}-Er{sup 3+}-Ho{sup 3+} under 980 nm excitation. Highlights: > Ca{sub 3}(PO{sub 4}){sub 2}:Tb{sup 3+},Na{sup +} exhibits a comparable brightness with commercial Zn{sub 2}SiO{sub 4}:Mn{sup 2+}. > Red, green and blue colors are achieved in Yb{sup 3+}, Ho{sup 3+}, Er{sup 3+}, Tm{sup 3+} doped Ca{sub 3}(PO{sub 4}){sub 2}. > Good white emission is obtained in Yb{sup 3+}-Ho{sup 3+}-Er{sup 3+}-Tm{sup 3+} quadri-doped Ca{sub 3}(PO{sub 4}){sub 2}. > Ca{sub 3}(PO{sub 4}){sub 2}:Tb{sup 3+}, Yb{sup 3+}, Ho{sup 3+}, Er{sup 3+}, Tm{sup 3+} could be potential phosphors.

  1. Size-Tunable and Monodisperse Tm3+/Gd3+-Doped Hexagonal NaYbF4 Nanoparticles with Engineered Efficient Near Infrared-to-Near Infrared Upconversion for In Vivo Imaging

    PubMed Central

    2015-01-01

    Hexagonal NaYbF4:Tm3+ upconversion nanoparticles hold promise for use in high contrast near-infrared-to-near-infrared (NIR-to-NIR) in vitro and in vivo bioimaging. However, significant hurdles remain in their preparation and control of their morphology and size, as well as in enhancement of their upconversion efficiency. Here, we describe a systematic approach to produce highly controlled hexagonal NaYbF4:Tm3+ nanoparticles with superior upconversion. We found that doping appropriate concentrations of trivalent gadolinium (Gd3+) can convert NaYbF4:Tm3+ 0.5% nanoparticles with cubic phase and irregular shape into highly monodisperse NaYbF4:Tm3+ 0.5% nanoplates or nanospheres in a pure hexagonal-phase and of tunable size. The intensity and the lifetime of the upconverted NIR luminescence at 800 nm exhibit a direct dependence on the size distribution of the resulting nanoparticles, being ascribed to the varied surface-to-volume ratios determined by the different nanoparticle size. Epitaxial growth of a thin NaYF4 shell layer of ∼2 nm on the ∼22 nm core of hexagonal NaYbF4:Gd3+ 30%/Tm3+ 0.5% nanoparticles resulted in a dramatic 350 fold NIR upconversion efficiency enhancement, because of effective suppression of surface-related quenching mechanisms. In vivo NIR-to-NIR upconversion imaging was demonstrated using a dispersion of phospholipid-polyethylene glycol (DSPE-PEG)-coated core/shell nanoparticles in phosphate buffered saline. PMID:25027118

  2. Controlled growth, intense upconversion emissions and concentration induced luminescence switching of bifunctional Tm3+ doped hexagonal NaYb0.55Gd0.45F4 nanorods

    NASA Astrophysics Data System (ADS)

    Qu, Xilong; Li, Yongchang; Yu, Suixi; Yang, Liwen

    2013-11-01

    Bifunctional hexagonal Tm3+ doped NaYb0.55Gd0.45F4 nanorods with tunable size are prepared via in situ cation-exchange reaction using hydrothermal method. The measured field dependence of magnetization of the NaYb0.55Gd0.45F4 nanorods shows typical paramagnetic characteristics that can be ascribed to the non-interacting localized nature of the magnetic moment of rare-earth ions. When excited by a 980 nm laser, these nanorods exhibit intense multi-color up-conversion (UC) emissions in infrared, red, blue and especially ultraviolet. In addition, luminescent switching between different UC emission wavelengths of 480 nm and 450 nm is observed by adjusting Tm3+ doping concentration. Based on power-dependent spectral analyses, it is found that with the increase of Tm3+ doping concentration, due to the suppressed saturation effect, the dominative UC process redistribute the populations at 1G4 and 1D2(Tm3+) states of Tm3+ ion resulting in the above luminescent switching. Our results indicate that bifunctional hexagonal NaYb1-xGdxF4 nanocrystals have potential applications in miniaturized solid-state light sources, optical processing sensors and fluorescent biolabels.

  3. Wideband saturable absorption in few-layer molybdenum diselenide (MoSe_2) for Q-switching Yb-, Er- and Tm-doped fiber lasers

    NASA Astrophysics Data System (ADS)

    Woodward, R. I.; Howe, R. C. T.; Runcorn, T. H.; Hu, G.; Torrisi, F.; Kelleher, E. J. R.; Hasan, T.

    2015-07-01

    We fabricate a free-standing molybdenum diselenide (MoSe2) saturable absorber by embedding liquid-phase exfoliated few-layer MoSe2 flakes into a polymer film. The MoSe2-polymer composite is used to Q-switch fiber lasers based on ytterbium (Yb), erbium (Er) and thulium (Tm) gain fiber, producing trains of microsecond-duration pulses with kilohertz repetition rates at 1060 nm, 1566 nm and 1924 nm, respectively. Such operating wavelengths correspond to sub-bandgap saturable absorption in MoSe2, which is explained in the context of edge-states, building upon studies of other semiconducting transition metal dichalcogenide (TMD)-based saturable absorbers. Our work adds few-layer MoSe2 to the growing catalog of TMDs with remarkable optical properties, which offer new opportunities for photonic devices.

  4. Wideband saturable absorption in few-layer molybdenum diselenide (MoSe?) for Q-switching Yb-, Er- and Tm-doped fiber lasers.

    PubMed

    Woodward, R I; Howe, R C T; Runcorn, T H; Hu, G; Torrisi, F; Kelleher, E J R; Hasan, T

    2015-07-27

    We fabricate a free-standing molybdenum diselenide (MoSe2) saturable absorber by embedding liquid-phase exfoliated few-layer MoSe2 flakes into a polymer film. The MoSe2-polymer composite is used to Q-switch fiber lasers based on ytterbium (Yb), erbium (Er) and thulium (Tm) gain fiber, producing trains of microsecond-duration pulses with kilohertz repetition rates at 1060 nm, 1566 nm and 1924 nm, respectively. Such operating wavelengths correspond to sub-bandgap saturable absorption in MoSe2, which is explained in the context of edge-states, building upon studies of other semiconducting transition metal dichalcogenide (TMD)-based saturable absorbers. Our work adds few-layer MoSe2 to the growing catalog of TMDs with remarkable optical properties, which offer new opportunities for photonic devices. PMID:26367663

  5. Triple-doped KMnF3:Yb3+/Er3+/Tm3+ nanocubes: four-color upconversion emissions with strong red and near-infrared bands

    PubMed Central

    Wang, Hao; Hong, Xiaodong; Han, Renlu; Shi, Junhui; Liu, Zongjun; Liu, Shujuan; Wang, You; Gan, Yang

    2015-01-01

    Triple-doped (Yb3+/Er3+/Tm3+) KMnF3 nanocubes with uniform sizes of 250?nm were synthesized by a facile hydrothermal route using the oleic acid as the capping agent. It was found that these nanocubes can simultaneously exhibited four-color (blue, green, red and NIR) upconversion emissions under a single 980?nm near-infrared (NIR) laser excitation, which should have potential multicolor in vivo imaging applications. Specifically, the red (660?nm) and NIR (800?nm) peaks, known as two optical windows for imaging biological tissues, were strong. The spectral and pump analyses indicated the two-photon processes were responsible for the both red and NIR emissions. PMID:26608870

  6. Triple-doped KMnF3:Yb3+/Er3+/Tm3+ nanocubes: four-color upconversion emissions with strong red and near-infrared bands

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Hong, Xiaodong; Han, Renlu; Shi, Junhui; Liu, Zongjun; Liu, Shujuan; Wang, You; Gan, Yang

    2015-11-01

    Triple-doped (Yb3+/Er3+/Tm3+) KMnF3 nanocubes with uniform sizes of 250?nm were synthesized by a facile hydrothermal route using the oleic acid as the capping agent. It was found that these nanocubes can simultaneously exhibited four-color (blue, green, red and NIR) upconversion emissions under a single 980?nm near-infrared (NIR) laser excitation, which should have potential multicolor in vivo imaging applications. Specifically, the red (660?nm) and NIR (800?nm) peaks, known as two optical windows for imaging biological tissues, were strong. The spectral and pump analyses indicated the two-photon processes were responsible for the both red and NIR emissions.

  7. Triple-doped KMnF3:Yb(3+)/Er(3+)/Tm(3+) nanocubes: four-color upconversion emissions with strong red and near-infrared bands.

    PubMed

    Wang, Hao; Hong, Xiaodong; Han, Renlu; Shi, Junhui; Liu, Zongjun; Liu, Shujuan; Wang, You; Gan, Yang

    2015-01-01

    Triple-doped (Yb(3+)/Er(3+)/Tm(3+)) KMnF3 nanocubes with uniform sizes of 250?nm were synthesized by a facile hydrothermal route using the oleic acid as the capping agent. It was found that these nanocubes can simultaneously exhibited four-color (blue, green, red and NIR) upconversion emissions under a single 980?nm near-infrared (NIR) laser excitation, which should have potential multicolor in vivo imaging applications. Specifically, the red (660?nm) and NIR (800?nm) peaks, known as two "optical windows" for imaging biological tissues, were strong. The spectral and pump analyses indicated the two-photon processes were responsible for the both red and NIR emissions. PMID:26608870

  8. [Effect of bivalent alkaline earth fluorides introduction on thermal stability and spectroscopic properties of Er3+/Tm3+ /Yb3+ co-doped oxyfluorogermanate glasses].

    PubMed

    Hu, Yue-bo; Zhang, Xin-na; Zhou, Da-li; Jiao, Qing; Wang, Rong-fei; Huang, Jin-feng; Long, Xiao-bo; Qiu, Jian-bei

    2012-01-01

    Transparent Er3+/Tm3+ /Yb3+ co-doped oxyfluorogermanate glasses alone containing MgF2, CaF2, SrF2 or BaF2 and nano-glass-ceramics only containing BaF2 were prepared. The thermal stabilities and the up-conversion emission properties of the samples were investigated. Analyses of absorbance spectra reveal that the UV cutoff band moves slightly to shortwave band with the doping bivalent cation mass increasing. The results show that the emission color can be adjusted by changing the alkaline earth cation species in the glass matrixes, especially as Mg2+ is concerned, and the emission intensity can increase notably by heating the glass containing alkaline-earth fluoride into glass ceramic containing alkaline-earth fluoride nanocrystals or increasing the content of bivalent alkaline earth fluorides. PMID:22497127

  9. Rational morphology control of ?-NaYF4:Yb,Er/Tm upconversion nanophosphors using a ligand, an additive, and lanthanide doping

    NASA Astrophysics Data System (ADS)

    Na, Hyejin; Woo, Kyoungja; Lim, Kipil; Jang, Ho Seong

    2013-05-01

    We report the systematic control of the morphology of ?-NaYF4:Yb,Er/Tm upconversion nanophosphors (UCNPs) from large spheres (37.9 nm) to rods (length = 60.1 nm, width = 21.5 nm) and from rods to hexagonal prisms (length = 48.8 nm, width = 44.0 nm) or small spheres (14.0 nm) by the use of a surfactant, an additive, and lanthanide doping. Increasing the ratio of oleic acid (OA) to 1-octadecene (ODE) caused a decrease in the size of the UCNPs, and increasing the OA/ODE ratio above a critical value caused the particle shape to change from a sphere to a rod. The length-to-width aspect ratio (AR) of upconversion nanorods (UCNRs) was finely manipulated from 1.28 to 2.80. The rounded tips of the UCNRs were flattened by adding Cl- ions, and the UCNRs changed to hexagonal prisms with a controllable AR depending on the quantity of Cl- ions. Additionally, the morphology of the ?-NaYF4-based UCNPs was controlled by lanthanide doping. The size and AR of the UCNRs decreased with Gd3+ doping, and the UCNRs ultimately transformed into small spheres (14.0 nm) with high monodispersity. Doping with Ce3+ ions also decreased the AR of the UCNRs from 2.80 to 1.27. In addition, highly transparent polymer composites for 3D volumetric displays were fabricated by blending high-AR ?-NaYF4:Yb,Er/Tm UCNRs with polydimethylsiloxane. These composites exhibited bright green and blue upconversion light during excitation with 980 nm light.We report the systematic control of the morphology of ?-NaYF4:Yb,Er/Tm upconversion nanophosphors (UCNPs) from large spheres (37.9 nm) to rods (length = 60.1 nm, width = 21.5 nm) and from rods to hexagonal prisms (length = 48.8 nm, width = 44.0 nm) or small spheres (14.0 nm) by the use of a surfactant, an additive, and lanthanide doping. Increasing the ratio of oleic acid (OA) to 1-octadecene (ODE) caused a decrease in the size of the UCNPs, and increasing the OA/ODE ratio above a critical value caused the particle shape to change from a sphere to a rod. The length-to-width aspect ratio (AR) of upconversion nanorods (UCNRs) was finely manipulated from 1.28 to 2.80. The rounded tips of the UCNRs were flattened by adding Cl- ions, and the UCNRs changed to hexagonal prisms with a controllable AR depending on the quantity of Cl- ions. Additionally, the morphology of the ?-NaYF4-based UCNPs was controlled by lanthanide doping. The size and AR of the UCNRs decreased with Gd3+ doping, and the UCNRs ultimately transformed into small spheres (14.0 nm) with high monodispersity. Doping with Ce3+ ions also decreased the AR of the UCNRs from 2.80 to 1.27. In addition, highly transparent polymer composites for 3D volumetric displays were fabricated by blending high-AR ?-NaYF4:Yb,Er/Tm UCNRs with polydimethylsiloxane. These composites exhibited bright green and blue upconversion light during excitation with 980 nm light. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00080j

  10. Charge disproportionation in RNiO3 (R= Tm, Yb) perovskites observed in situ by neutron diffraction and 57Fe probe Mssbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Alonso, J. A.; Martnez-Lope, M. J.; Presniakov, I. A.; Sobolev, A. V.; Rusakov, V. S.; Gapochka, A. M.; Demazeau, G.; Fernndez-Daz, M. T.

    2013-05-01

    An in-situ investigation from high-resolution neutron powder diffraction data on the structural evolution of TmNiO3 and YbNiO3 perovskites across the metal-insulator transition, with TMI = 596 K and 598 K, respectively, allowed the charge disproportionation effect that these perovskites experience upon electronic localization below TMI to be followed. In the insulating (semiconducting) regime, the perovskites are monoclinic, space group P21/n, containing two inequivalent Ni1(3+?)+ and Ni2(3-?)+ cations; above TMI, the samples become orthorhombic, space group Pbnm, with a single site for Ni3+. The 57Fe Mssbauer spectra of iron-doped (at 1.5%) RNiO3 (R = Tm, Yb) samples recorded below TMI exhibit for Fe1 and Fe2 (replacing Ni1 and Ni2 sites) hyperfine parameters corresponding to large (Ni1O6) and small (Ni2O6) octahedra. The remarkable difference between the quadrupole splittings (?1 ? 0.3 mm/s and ?2 ? 0.07 mm/s) of Fe1 and Fe2 sites in RNi0.985Fe0.015O3 is analyzed. We calculate the lattice contribution to the electric field gradient (EFG) at 57Fe ions, and estimate, by using the experimental ?1 and ?2 values, the contributions of the 3d, 3p, and 2p electrons (overlap distortion and covalence effects). Above TMI, a unique state for iron atoms is observed, upon metallization of the sample.

  11. Real-time, non-invasive monitoring of hydrogel degradation using LiYF4:Yb(3+)/Tm(3+) NIR-to-NIR upconverting nanoparticles.

    PubMed

    Jalani, Ghulam; Naccache, Rafik; Rosenzweig, Derek H; Lerouge, Sophie; Haglund, Lisbet; Vetrone, Fiorenzo; Cerruti, Marta

    2015-07-14

    To design a biodegradable hydrogel as cell support, one should know its in vivo degradation rate. A technique commonly used to track gel degradation is fluorescence spectroscopy. However, the fluorescence from conventional fluorophores quickly decays, and the fluorophores are often moderately cytotoxic. Most importantly, they require ultraviolet or visible (UV-Vis) light as the excitation source, which cannot penetrate deeply through biological tissues. Lanthanide-doped upconverting nanoparticles (UCNPs) are exciting alternatives to conventional fluorophores because they can convert near-infrared (NIR) to UV-Vis-NIR light via a sequential multiphoton absorption process referred to as upconversion. NIR light can penetrate up to few cm inside tissues, thus making these UCNPs much better probes than conventional fluorophores for in vivo monitoring. Also, UCNPs have narrow emission bands, high photoluminescence (PL) signal-to-noise ratio, low cytotoxicity and good physical and chemical stability. Here, we show a nanocomposite system consisting of a biodegradable, in situ thermogelling injectable hydrogel made of chitosan and hyaluronic acid encapsulating silica-coated LiYF4:Yb(3+)/Tm(3+) UCNPs. We use these UCNPs as photoluminescent tags to monitor the gel degradation inside live, cultured intervertebral discs (IVDs) over a period of 3 weeks. PL spectroscopy and NIR imaging show that NIR-to-NIR upconversion of LiYF4:Yb(3+)/Tm(3+)@SiO2 UCNPs allows for tracking of the gel degradation in living tissues. Both in vitro and ex vivo release of UCNPs follow a similar trend during the first 5 days; after this time, ex vivo release becomes faster than in vitro, indicating a faster gel degradation ex vivo. Also, the amount of released UCNPs in vitro increases continuously up to 3 weeks, while it plateaus after 15 days inside the IVDs showing a homogenous distribution of UCNPs throughout the IVD tissue. This non-invasive optical method for real time, live tissue imaging holds great potential for tissue analysis, biomapping and bioimaging applications. PMID:26067274

  12. Incorporation of computed tomography and magnetic resonance imaging function into NaYF4:Yb/Tm upconversion nanoparticles for in vivo trimodal bioimaging.

    PubMed

    Shen, Ji-Wei; Yang, Cheng-Xiong; Dong, Lu-Xi; Sun, Hao-Ran; Gao, Kai; Yan, Xiu-Ping

    2013-12-17

    Rational design and fabrication of multimodal imaging nanoprobes are of great significance for in vivo imaging. Here we report the fabrication of a multishell structured NaYF4:Yb/Tm@NaLuF4@NaYF4@NaGdF4 nanoprobe via a seed-mediated epitaxial growth strategy for upconversion luminescence (UCL), X-ray computed tomography (CT), and magnetic resonance (MR) trimodal imaging. Hexagonal phase NaYF4:Yb/Tm is used as the core to provide UCL, while the shell of NaLuF4 is epitaxially grown on the core not only to provide an optically inert layer for enhancing the UCL but also to serve as a contrast agent for CT. The outermost NaGdF4 shell is fabricated as a thin layer to give the high longitudinal relaxivity (r1) desired for MR imaging. The transition shell layer of NaYF4 not only provides an interface to facilitate the formation of NaGdF4 shell but also inhibits the energy transfer from inner upconversion activator to surface paramagnetic Gd(3+) ions. The fabricated multishell structured nanoprobe shows intense near-infrared UCL, high r1 value of 3.76 mM(-1) s(-1), and in vitro CT contrast effect. The multishell structured nanoprobe offers great potential for in vivo UCL/CT/MR trimodal imaging. Further covalent bonding of folic acid makes the multishell structured nanoprobe promising for in vivo targeted UCL imaging of tumor-bearing mice. PMID:24237132

  13. Impact of codopant ions on 2.5-3.0 ?m emission of Er3+:4I11/2?4I13/2 transition in Yb,Er,Eu:LaYSGG crystal

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Li, Jianfu; Zhu, Zhaojie; You, Zhenyu; Xu, Jinlong; Tu, Chaoyang

    2015-12-01

    The crystal of 1 at% Yb3+, 10 at% Er3+ and 0.1 at% Eu3+ triply doped La0.3Y2.7Sc2Ga3O12 (abbr. as Yb,Er,Eu:LaYSGG) was grown for the first time by using a Czochralski technique. Its absorption, near-infrared and mid-infrared fluorescence spectra, as well as the fluorescence decay curves of Er:4I13/2 and 4I11/2 levels were measured at room temperature. The spectroscopic properties including the absorption and emission cross-sections as well as the fluorescence lifetimes of the title crystal were revealed and compared with 10 at% Er3+:Y3Sc2Ga3O12 crystal. Spectral analyses show that the sensitization of Yb3+ ion leads to an enhanced 2.5-3.0 ?m emission corresponding to Er3+:4I11/2?4I13/2 transition in the grown crystal, meanwhile, the depopulation of Eu3+ ion from Er3+ inhibits the self-termination effect successfully. The energy transfer mechanism was discussed; the energy transfer efficiencies of Yb3+?Er3+ (ET1) and Er3+?Eu3+ (ET2) were estimated to be 94.8% and 93.9%, respectively. The results indicates that Yb,Er,Eu:LaYSGG crystal is a good candidate for LD pumped mid-infrared laser.

  14. Synthesis, characterisation and properties of rare earth oxyselenides A4O4Se3 (A = Eu, Gd, Tb, Dy, Ho, Er, Yb and Y).

    PubMed

    Tuxworth, Andrew J; Wang, Chun-Hai; Evans, John S O

    2015-02-21

    Rare earth oxyselenides A4O4Se3 (A = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Y) were synthesised using solid state reactions and three new structure types (β, γ, and δ) were observed. A4O4Se3 materials adopt either the α (A = Nd, Sm), β (A = Eu), γ (A = Gd, Tb) or δ (A = Dy, Ho, Er, Yb, Y) structure depending on the rare earth radius. Each structure type contains alternating [A2O2](2+) and Se(2-)/Se2(2-) layers. Different ordered and disordered arrangements of Se(2-) and [Se-Se](2-) give the Se layer flexibility and lead to the four different structure types observed. The volume coefficients of expansion for A4O4Se3 ranged from +1.746(9) × 10(-5) to +2.237(3) × 10(-5) K(-1) from 12 to 300 K; no structural phase transitions were observed in this temperature range. Diffuse reflection spectra show A4O4Se3 are semiconductors with band gap Eg 1.02-1.46 eV. Gd4O4Se3, Dy4O4Se3, and Tb4O4Se3 samples show antiferromagnetic ordering with Néel temperature, TN, of 7-9 K. DFT calculations confirm the two different valence states of Se(2-) and Se2(2-) in Eu4O4Se3. PMID:25581725

  15. Multi-modal luminescence properties of RE3+ (Tm3+, Yb3+) and Bi3+ activated GdNbO4 phosphorsupconversion, downshifting and quantum cutting for spectral conversion

    NASA Astrophysics Data System (ADS)

    Dwivedi, A.; Mishra, Kavita; Rai, S. B.

    2015-11-01

    This work investigates the promising multi-modal luminescence (upconversion (UC), downshifting (DS) and quantum cutting (QC)) properties of RE3+ (Tm3+, Yb3+) and Bi3+ activated GdNbO4 phosphors synthesized using the well-known solid state reaction method. Structural characterization using x-ray diffraction measurements confirms the formation of the pure phase of the GdNbO4 host with no impurities. The optical band gap (E g) of GdNbO4 (with and without RE3+ ions) calculated from UV-Vis-near-infrared (NIR) measurements was found to be the same ~4.44?eV which indicates that GdNbO4 is a wide band gap material. Further, Bi3+ doping presents an interesting E g tuning of the GdNbO4 phosphor, i.e. E g increases up to 5.38?eV. In terms of luminescence, this material produces intense blue and NIR emission via multi-modal optical processes. On NIR excitation (? exc??=??980?nm), Gd0.94Tm0.01Yb0.05NbO4 produces intense upconverted blue and NIR and relatively weak red emission. In addition to the UC process, Gd0.94Tm0.01Yb0.05NbO4 also exhibits pump power dependent variation in fluorescence intensity ratio for I 472/I 477 showing the applicability of this material as an optical heater. On UV excitation (? exc??=??265?nm), Gd0.99Tm0.01NbO4 produces intense DS blue emission due to the Tm3+ ion, overlapped with the emission of the (NbO4)3- ion through strong energy transfer (ET) from (NbO4)3- to Tm3+ ions. Interestingly, NIR QC has also been successfully observed in Gd0.9Yb0.1NbO4, Gd0.89Bi0.01Yb0.1NbO4 and Gd0.79Tm0.01Yb0.2NbO4 phosphors through cooperative ET from the (NbO4)3- group to the Yb3+ ion, Bi(6s)-Nb(4d) to the Yb3+ ion and the Tm3+ ion to the Yb3+ ion, respectively. The mechanisms involved in these processes are explained in detail in this work. The QC efficiency in this work has been found to be ~177%. Thus, the multi-modal luminescence (UC, DS and QC) property of this material makes it a promising candidate for display devices, spectral converters for enhancing the efficiency of silicon solar cells, etc.

  16. Effects of water on Eu/sup 2 +/, Yb/sup 2 +/, and Es/sup 2 +/ cocrystallization in the Sr(Sm)SO/sub 4/-ethanol system

    SciTech Connect

    Mikheev, N.B.; Kamenskaya, A.N.; Kulyukhin, S.A.

    1988-11-01

    Measurements have been made on the effects of water on the cocrystallization of divalent europium, ytterbium, and einsteinium in the Sr(Sm)SO/sub 4/-ethanol system. Water levels from 3 to 6 M affect the Eu/sup 2 +/ and Yb/sup 2 +/ cocrystallization coefficients, while above 6 M, they do not alter. With divalent einsteinium, there are changes in the coefficient up to (H/sub 2/O) = 10 M. The effects of the water concentration on the solubility have been examined for the sulfates of these three elements.

  17. Structural and Magnetothermal Properties of Compounds: Yb5SixGe4-x,Sm5SixGe4-x, EuO, and Eu3O4

    SciTech Connect

    Kyunghan Ahn

    2007-05-09

    The family of R{sub 5}Si{sub x}Ge{sub 4-x} alloys demonstrates a variety of unique physical phenomena related to magneto-structural transitions associated with reversible breaking and reforming of specific bonds that can be controlled by numerous external parameters such as chemical composition, magnetic field, temperature, and pressure. Therefore, R{sub 5}Si{sub x}Ge{sub 4-x} systems have been extensively studied to uncover the mechanism of the extraordinary magneto-responsive properties including the giant magnetoresistance (GMR) and colossal magnetostriction, as well as giant magnetocaloric effect (GMCE). Until now, more than a half of possible R{sub 5}Si{sub x}Ge{sub 4-x} pseudobinary systems have been completely or partially investigated with respect to their crystallography and phase relationships (R = La, Pr, Nd, Gd, Tb, Dy, Er, Lu, Y). Still, there are other R{sub 5}Si{sub x}Ge{sub 4-x} systems (R = Ce, Sm, Ho, Tm, and Yb) that are not studied yet. Here, we report on phase relationships and structural, magnetic, and thermodynamic properties in the Yb{sub 5}Si{sub x}Ge{sub 4-x} and Sm{sub 5}Si{sub x}Ge{sub 4-x} pseudobinary systems, which may exhibit mixed valence states. The crystallography, phase relationships, and physical properties of Yb{sub 5}Si{sub x}Ge{sub 4-x} alloys with 0 {le} x {le} 4 have been examined by using single crystal and powder x-ray diffraction at room temperature, and dc magnetization and heat capacity measurements between 1.8 K and 400 K in magnetic fields ranging from 0 to 7 T. Unlike the majority of R{sub 5}Si{sub x}Ge{sub 4-x} systems studied to date, where R is the rare earth metal, all Yb-based germanide-silicides with the 5:4 stoichiometry crystallize in the same Gd{sub 5}Si{sub 4}-type structure. The magnetic properties of Yb{sub 5}Si{sub x}Ge{sub 4-x} materials are nearly composition-independent, reflecting the persistence of the same crystal structure over the whole range of x from 0 to 4. Both the crystallographic and magnetic property data indicate that Yb{sub 5}Si{sub x}Ge{sub 4-x} alloys are mixed valence systems, in which the majority (60%) of Yb atoms is divalent, while the minority (40%) is trivalent. This finding is supported by recent Moessbauer spectroscopy data.

  18. Controllable red, green, blue (RGB) and bright white upconversion luminescence of Lu2O3:Yb3+/Er3+/Tm3+ nanocrystals through single laser excitation at 980 nm.

    PubMed

    Yang, Jun; Zhang, Cuimiao; Peng, Chong; Li, Chunxia; Wang, Lili; Chai, Ruitao; Lin, Jun

    2009-01-01

    Light fantastic! Lu(2)O(3):Yb(3+)/Er(3+)/Tm(3+) nanocrystals with controllable red, green, blue (RGB) and bright white upconversion luminescence by a single laser excitation of 980 nm have been successfully synthesized (see picture). Due to abundant UC PL colors, it can potentially be used as fluorophores in the field of color displays, back light, UC lasers, photonics, and biomedicine.Lu(2)O(3):Yb(3+)/Er(3+)/Tm(3+) nanocrystals have been successfully synthesized by a solvothermal process followed by a subsequent heat treatment at 800 degrees C. Powder X-ray diffraction, transmission electron microscopy, upconversion photoluminescence spectra, and kinetic decay were used to characterize the samples. Under single-wavelength diode laser excitation of 980 nm, the bright blue emissions of Lu(2)O(3):Yb(3+), Tm(3+) nanocrystals near 477 and 490 nm were observed due to the (1)G(4)-->(3)H(6) transition of Tm(3+). The bright green UC emissions of Lu(2)O(3):Er(3+) nanocrystals appeared near 540 and 565 nm were observed and assigned to the (2)H(11/2)-->(4)I(15/2) and (4)S(3/2)-->(4)I(15/2) transitions, respectively, of Er(3+). The ratio of the intensity of green luminescence to that of red luminescence decreases with an increase of concentration of Yb(3+) in Lu(2)O(3):Er(3+) nanocrystals. In sufficient quantities of Yb(3+) with resprct to Er(3+), the bright red UC emission of Lu(2)O(3):Yb(3+)/Er(3+) centered at 662 nm was predominant, due to the (4)F(9/2)-->(4)I(15/2) transition of Er(3+). Based on the generation of red, green, and blue emissions in the different doped Lu(2)O(3):RE(3+) nanocrystals, it is possible to produce the luminescence with a wide spectrum of colors, including white, by the appropriate doping of Yb(3+), Tm(3+), and Er(3+) in the present Lu(2)O(3) nanocrystals. Namely, Lu(2)O(3):3 %Yb(3+)/0.2 %Tm(3+)/0.4 %Er(3+) nanocrystals show suitable intensities of blue, green, and red (RGB) emission, resulting in the production of perfect and bright white light with CIE-x=0.3456 and CIE-y=0.3179, which is very close to the standard equal energy white light illuminate (x=0.33, y=0.33). Because of abundant luminescent colors from RGB to white in Lu(2)O(3):Yb(3+)/Er(3+)/Tm(3+) nanocrystals under 980 nm laser diode (LD) excitation, they can potentially be used as fluorophores in the field of color displays, back light, UC lasers, photonics, and biomedicine. PMID:19296483

  19. Neutron spectroscopic study of crystal-field excitations and the effect of the crystal field on dipolar magnetism in Li R F4 (R =Gd , Ho, Er, Tm, and Yb)

    NASA Astrophysics Data System (ADS)

    Babkevich, P.; Finco, A.; Jeong, M.; Dalla Piazza, B.; Kovacevic, I.; Klughertz, G.; Krmer, K. W.; Kraemer, C.; Adroja, D. T.; Goremychkin, E.; Unruh, T.; Strssle, T.; Di Lieto, A.; Jensen, J.; Rnnow, H. M.

    2015-10-01

    We present a systematic study of the crystal-field interactions in the Li R F4 (R = Gd , Ho, Er, Tm, and Yb) family of rare-earth magnets. Using detailed inelastic neutron scattering measurements, we have been able to quantify the transition energies and wave functions for each system. This allows us to quantitatively describe the high-temperature susceptibility measurements for the series of materials and make predictions based on a mean-field approach for the low-temperature thermal and quantum phase transitions. We show that coupling between crystal field and phonon states leads to line-shape broadening in LiTmF4 and level splitting in LiYbF4. Furthermore, using high-resolution neutron scattering from LiHoF4, we find anomalous broadening of crystal-field excitations which we attribute to magnetoelastic coupling.

  20. Near-infrared photocatalysts of BiVO4/CaF2:Er3+, Tm3+, Yb3+ with enhanced upconversion properties

    NASA Astrophysics Data System (ADS)

    Huang, Shouqiang; Zhu, Nanwen; Lou, Ziyang; Gu, Lin; Miao, Chen; Yuan, Haiping; Shan, Aidang

    2014-01-01

    Upconversion photocatalysts have the potential to absorb the near-infrared (NIR) light in solar energy and improve the photocatalytic performance. A hierarchical upconversion photocatalyst of BiVO4 (BVO)/CaF2:Er3+, Tm3+, Yb3+ (CF) combined with the narrow-band semiconductor of BVO and the luminescence agent of CF to enhance upconversion properties was synthesized via the hydrothermal method. The CF particles were deposited homogeneously on the surface of the BVO/CF composite with regular dendritic structure, which led to efficient upconversion emissions. The upconversion emission intensity of the BVO/CF composite was 8 times higher than that of pure CF, through tailoring the crystal symmetry of lanthanide ions by Bi3+ ions. The upconverted ultraviolet (361 and 379 nm), violet (408 nm), and blue (485 nm) light was able to excite BVO for photocatalysis in BVO/CF under NIR irradiation, which improved the degradation rate of methyl orange (MO).Upconversion photocatalysts have the potential to absorb the near-infrared (NIR) light in solar energy and improve the photocatalytic performance. A hierarchical upconversion photocatalyst of BiVO4 (BVO)/CaF2:Er3+, Tm3+, Yb3+ (CF) combined with the narrow-band semiconductor of BVO and the luminescence agent of CF to enhance upconversion properties was synthesized via the hydrothermal method. The CF particles were deposited homogeneously on the surface of the BVO/CF composite with regular dendritic structure, which led to efficient upconversion emissions. The upconversion emission intensity of the BVO/CF composite was 8 times higher than that of pure CF, through tailoring the crystal symmetry of lanthanide ions by Bi3+ ions. The upconverted ultraviolet (361 and 379 nm), violet (408 nm), and blue (485 nm) light was able to excite BVO for photocatalysis in BVO/CF under NIR irradiation, which improved the degradation rate of methyl orange (MO). Electronic supplementary information (ESI) available: Additional tables and figures. See DOI: 10.1039/c3nr05266d

  1. Synchrotron X-Ray Topography Study of Structural Defects and Strain in Epitaxial Structures of Yb- and Tm-Doped Potassium Rare-Earth Double Tungstates and Their Influence on Laser Performance.

    SciTech Connect

    Raghothamachar, B.; Carvajal, J; Pujol, M; Mateos, X; Sole, R; Aguilo, M; Diaz, F; Dudley, M

    2010-01-01

    Monoclinic potassium rare-earth double tungstates [KRE(WO{sub 4}){sub 2}, RE = Y, Lu, Yb; KREW] are well suited as hosts for active lanthanide ion (Ln{sup 3+}) dopants for diode-pumped solid-state lasers, with particular interest in thin-disk laser configurations when they are grown as thin films. Using synchrotron white-beam x-ray topography, we have imaged defects and strain in top-seeded solution-grown (TSSG) bulk substrates of different rare-earth tungstates as well as within Yb{sup 3+}- and Tm{sup 3+}-doped epitaxies for thin-disk laser applications grown on these substrates by liquid-phase epitaxy. Higher structural stress in Yb:KYW/KYW epitaxies compared with Yb:KLuW/KLuW epitaxies is found to lower efficiency in laser operation. The quality of Tm:KLuW/KLuW epitaxial films is sensitive to doping level, film thickness, and growth rate. Inhomogeneous stresses within the layers are dominated by lattice-mismatch effects rather than by crystallographic anisotropy.

  2. Synchrotron X-Ray Topography Study of Structural Defects and Strain in Epitaxial Structures of Yb- and Tm-Doped Potassium Rare-Earth Double Tungstates and Their Influence on Laser Performance

    NASA Astrophysics Data System (ADS)

    Raghothamachar, B.; Carvajal, J. J.; Pujol, M. C.; Mateos, X.; Sol, R.; Aguil, M.; Daz, F.; Dudley, M.

    2010-06-01

    Monoclinic potassium rare-earth double tungstates [KRE(WO4)2, RE = Y, Lu, Yb; KREW] are well suited as hosts for active lanthanide ion (Ln3+) dopants for diode-pumped solid-state lasers, with particular interest in thin-disk laser configurations when they are grown as thin films. Using synchrotron white-beam x-ray topography, we have imaged defects and strain in top-seeded solution-grown (TSSG) bulk substrates of different rare-earth tungstates as well as within Yb3+- and Tm3+-doped epitaxies for thin-disk laser applications grown on these substrates by liquid-phase epitaxy. Higher structural stress in Yb:KYW/KYW epitaxies compared with Yb:KLuW/KLuW epitaxies is found to lower efficiency in laser operation. The quality of Tm:KLuW/KLuW epitaxial films is sensitive to doping level, film thickness, and growth rate. Inhomogeneous stresses within the layers are dominated by lattice-mismatch effects rather than by crystallographic anisotropy.

  3. High-temperature electrical and thermal transport properties of fully filled skutterudites RFe4Sb12 (R = Ca, Sr, Ba, La, Ce, Pr, Nd, Eu, and Yb)

    NASA Astrophysics Data System (ADS)

    Qiu, P. F.; Yang, J.; Liu, R. H.; Shi, X.; Huang, X. Y.; Snyder, G. J.; Zhang, W.; Chen, L. D.

    2011-03-01

    Fully filled skutterudites RFe4Sb12 (R = Ca, Sr, Ba, La, Ce, Pr, Nd, Eu, and Yb) have been prepared and the high-temperature electrical and thermal transport properties are investigated systematically. Lattice constants of RFe4Sb12 increase almost linearly with increasing the ionic radii of the fillers, while the lattice expansion in filled structure is weakly influenced by the filler valence charge states. Using simple charge counting, the hole concentration in RFe4Sb12 with divalent fillers (R = Ca, Sr, Ba, Eu, and Yb) is much higher than that in RFe4Sb12 with trivalent fillers (R = La, Ce, Pr, and Nd), resulting in relatively high electrical conductivity and low Seebeck coefficient. It is also found that RFe4Sb12 filled skutterudites having similar filler valence charge states exhibit comparable electrical conductivity and Seebeck coefficient, and the behavior of the temperature dependence, thereby leading to comparable power factor values in the temperature range from 300 to 800 K. All RFe4Sb12 samples possess low lattice thermal conductivity. The correlation between the lattice thermal resistivity WL and ionic radii of the fillers is discussed and a good relationship of WL (rcage-rion)3 is observed in lanthanide metal filled skutterudites. CeFe4Sb12, PrFe4Sb12, and NdFe4Sb12 show the highest thermoelectric figure of merit around 0.87 at 750 K among all the filled skutterudites studied in this work.

  4. Ultraviolet-driven white light generation from oxyfluoride glass co-doped with Tm{sup 3+}-Tb{sup 3+}-Eu{sup 3+}

    SciTech Connect

    Kuznetsov, A. S.; Nikitin, A.; Tikhomirov, V. K.; Shestakov, M. V.; Moshchalkov, V. V.

    2013-04-22

    Tm{sup 3+}-Tb{sup 3+}-Eu{sup 3+} co-doped oxyfluoride glasses, doped with about 3.0 mol. % TmF{sub 3}, 0.25 mol. % TbF{sub 3}, and 0.25 mol. % EuF{sub 3}, have been prepared by melt quenching technique. Under excitation at commercial 365 nm, the rare-earth co-dopants are all directly excited and emit in the blue, green, and red, respectively, without appreciable energy transfer amongst the co-dopants. Tint of the white luminescence can be adjusted by changing the ratio of the co-dopants. Properties of the glass host promote excellent dissolution of the co-dopants and low non-radiative decay rate. The white emission at 365 nm excitation is suitable for light emitting diodes applications.

  5. Measurement of Quantum Yield and Upconversion Brightness in Red, Blue and Green on NIR Excited M2O2S:Yb/Er/Ho/Tm Phosphors

    NASA Astrophysics Data System (ADS)

    Beeks, Ivan; Kumar, Ajith G.; Sardar, Dhiraj K.

    2015-03-01

    A series of broadly color tunable upconversion phosphors were synthesized from M2O2S (M=Y,Gd,La) using a flux fusion method. We investigate their upconversion properties as a function of the dopant concentrations and excitation power density. The phosphor compositions were determined for their upconversion characteristics under 800, 980 and 1550 nm excitations. By measuring the quantum yield and luminous brightness, we investigate their potential applications in biomedical imaging as well as NIR display applications. Results are compared with the well-known upconversion phosphor NaYF4:Yb/Er/Ho/Tm and found that the M2O2S phosphor systems are more efficient compared to NaYF4. By adopting various synthesis protocols, we were able to examine M2O2S in the size range of 10 nm to 10 ?m. This research is supported by the National Science Foundation Partnerships for Research and Education in Materials (NSF-PREM) Grant N0-DMR-0934218.

  6. Infrared-active optical phonons and magnetic excitations in the hexagonal manganites RMnO3 (R =Ho, Er, Tm, Yb, and Lu)

    NASA Astrophysics Data System (ADS)

    Basistyy, R.; Stanislavchuk, T. N.; Sirenko, A. A.; Litvinchuk, A. P.; Kotelyanskii, M.; Carr, G. L.; Lee, N.; Wang, X.; Cheong, S.-W.

    2014-07-01

    Optical properties of hexagonal multiferroic oxides RMnO3, where R=Ho, Er, Tm, Yb, and Lu, have been studied in the far-infrared spectral range between 100 and 2000 cm-1 and temperatures between 1.5 and 300 K by means of several experimental techniques: Mueller matrix spectroscopic ellipsometry, rotating analyzer ellipsometry, and optical transmission spectroscopy. Spectra of the optical phonons are described in terms of the temperature dependencies of their frequency, damping, and oscillator strength. For all studies, oxide materials' clear signatures of the spin-phonon interaction have been found below the temperature of the antiferromagnetic phase transition TN due to magnetic ordering of Mn3+ spins. A decrease of the ionic radius for R3+ ions between Ho3+ and Lu3+ in the corresponding RMnO3 compounds resulted in systematic variation of the frequency for several optical phonons. A magnetic excitation at 190 cm-1 was observed at low temperatures below TN and interpreted as resulting from two-magnon absorption.

  7. NIR to blue light upconversion in Tm{sup 3+}/Yb{sup 3+} codoped BaTiO{sub 3} tellurite glass

    SciTech Connect

    Kumari, Astha Rai, Vineet Kumar

    2015-05-15

    Upconversion is an interesting optical property, generally shown by rare-earth doped materials. This unusual optical behavior shown by these rare-earths doped materials are due to their peculiar atomic configuration and electronic transitions. Here, the Tm{sup 3+}-Yb{sup 3+} codoped BaTiO{sub 3} glass with TeO{sub 2} as former has been prepared by conventional melt and quench technique and the upconversion property has been investigated with the help of near infrared (NIR) to Visible UC study. The generation of the visible UC bands around ∼ 476 nm, ∼ 653 nm, ∼ 702 nm and one NIR UC band at ∼795 nm are assigned due to the {sup 1}G{sub 4}→ {sup 3}H{sub 6}, {sup 1}G{sub 4}→ {sup 3}F{sub 4}, {sup 3}F{sub 2}→ {sup 3}H{sub 6} and {sup 3}H{sub 4}→ {sup 3}H{sub 6} transitions respectively. The generations of these upconversion bands have been discussed in detail with the help of energy level diagram. The colour coordinates corresponding to the prepared material have been shown with the help of CIE chromaticity diagram. These glasses can be very appropriately used in the fabrication of solid state laser and as NIR to blue light upconverter.

  8. ?-NaYb(Mn)F4:Er(3+)/Tm(3+)@NaYF4 UCNPs as "Band-Shape" Luminescent Nanothermometers over a Wide Temperature Range.

    PubMed

    Xu, Xia; Wang, Zhuo; Lei, Pengpeng; Yu, Yingning; Yao, Shuang; Song, Shuyan; Liu, Xiuling; Su, Yue; Dong, Lile; Feng, Jing; Zhang, Hongjie

    2015-09-23

    Novel flower-like ?-NaYb(Mn)F4:Er(3+)/Tm(3+)@NaYF4 upconversion nanoparticles (UCNPs) as luminescent nanothermometers have been developed by combining liquid-solid solution hydrothermal strategy with thermal decomposition strategy. Under 980 nm excitation, they exhibit intense upconversion luminescence and temperature-dependent upconversion luminescence over a wide temperature range. The influence of temperature on "band-shape" upconversion luminescence (UCL) spectra and the intensity of emission bands are analyzed and discussed in detail. We further successfully test and verify that intensity ratios REr of (2)H11/2 ? (4)I15/2 and (4)S3/2 ? (4)I15/2 and RTm of (1)G4 ? (3)H5 and (3)H4 ? (3)H6 are sensitive to temperature, and the population of active ions follows Boltzmann-type population distribution very well. These luminescent nanothermometers could be applied over a wide temperature range from 123 to 423 K with high sensitivity, which enable them to be excellent candidates for temperature sensors. PMID:26312746

  9. Core-shell Fe3O4@NaLuF4:Yb,Er/Tm nanostructure for MRI, CT and upconversion luminescence tri-modality imaging.

    PubMed

    Zhu, Xingjun; Zhou, Jing; Chen, Min; Shi, Mei; Feng, Wei; Li, Fuyou

    2012-06-01

    Core-shell Fe(3)O(4)@NaLuF(4):Yb,Er/Tm nanostructure (MUCNP) with multifunctional properties has been developed using a step-wise synthetic method. The successful fabrication of MUCNP has been confirmed by transmission electron microscopy, powder X-ray diffraction, energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy. The MUCNP exhibits superparamagnetic property with saturation magnetization of 15 emu g(-1), and T(2)-enhanced magnetic resonance (MR) effect with an r(2) value of 21.63 s(-1) mM(-1) at 0.5 T, resulting from the Fe(3)O(4) cores. Moreover, the NaLuF(4)-based MUCNP provides excellent X-ray attenuation and upconversion luminescence (UCL) emission under excitation at 980 nm. In vivo MR, computed tomography (CT) and UCL images of tumor-bearing mice show that the MUCNP can be successfully used in multimodal imaging. In vitro tests reveal that the MUCNP is non-cytotoxic. These results suggest that the developed MUCNP could be served as an MR, CT and UCL probe for tri-modality imaging. PMID:22444645

  10. Structural and thermoelectric properties of BaRCo{sub 4}O{sub 7} (R = Dy, Ho, Er, Tm, Yb, and Lu)

    SciTech Connect

    Wong-Ng, W.; Yan, Y.; Liu, G.; Xie, W.; Tritt, T.; Kaduk, J.; Thomas, E.

    2011-12-01

    The structure and thermoelectric properties of a series of barium lanthanide cobaltites, BaRCo{sub 4}O{sub 7} (R = Dy, Ho, Er, Tm, Yb, and Lu), which were prepared using the spark plasma synthesis technique, have been investigated. The space group of these compounds was re-determined and confirmed to be P31c instead of the reported P6{sub 3}mc. The lattice parameters a and c range from 6.26279(2) Angst to 6.31181(6) Angst , and from 10.22468(6) Angst to 10.24446(15) Angst for R = Lu to Dy, respectively. The crystal structure of BaRCo{sub 4}O{sub 7} is built up from Kagome sheets of CoO{sub 4} tetrahedra, linked by triangular layers of CoO{sub 4} tetrahedra. The values of figure of merit (ZT) of the BaRCo{sub 4}O{sub 7} samples were determined to be around 0.02 at 800 K. X-ray diffraction patterns of these samples have been determined and submitted to the Powder Diffraction File.

  11. Solvothermal synthesis and characterization of blue, green and red emitting Y2O3:Ln3+ (Ln3+ = Tm3+, Tb3+ and Eu3+) nanocrystals

    NASA Astrophysics Data System (ADS)

    Devaraju, M. K.; Yin, S.; Sato, T.

    2009-02-01

    Lanthanide ions (Tm3+, Tb3+ and Eu3+) doped Y2O3 nanocrystals were prepared via solvothermal refluxing calcination method. Yttrium chloride hexahydrate and rare earth chloride (TmCl3, TbCl3 and EuCl3) were used as starting materials for the preparation of co-precipitated gel. The organic solvents such as ethylene glycol and polyethylene glycol (200#) were used to reflux co-precipitated gel and solvothermal refluxing reaction was carried out at 180C (ethylene glycol) and 240C (polyethylene glycol 200#) for 4 h. The samples were calcined at 800C and 1000C for 5 h to convert precursor materials into Y2O3 nanocrystals. The structure, morphology and thermal stability were characterized by XRD, TEM, FESEM, and TG-DTA analysis. The as prepared materials exhibited agglomerated and sphere like morphology with 20-30 nm in diameter depending on refluxing solvents used in the synthesis. The calcined samples after solvothermal reaction in polyethylene glycol exhibited sphere morphology with 30-80 nm in diameter. The photoluminescence results of Tm3+, Tb3+ and Eu3+ doped Y2O3 nanocrystals showed strong blue, green and red emission around 450, 540 and 610 nm under the excitation wavelength of 360, 304 and 254 nm respectively. The PL results were compared with reference sample prepared via co-precipitated calcination method.

  12. Synthesis, Characterization, and Application of Core-Shell Co0.16Fe2.84O4@NaYF4(Yb, Er) and Fe3O4@NaYF4(Yb, Tm) Nanoparticle as Trimodal (MRI, PET/SPECT, and Optical) Imaging Agents.

    PubMed

    Cui, Xianjin; Mathe, Domokos; Kovcs, Nomi; Horvth, Ildik; Jauregui-Osoro, Maite; Torres Martin de Rosales, Rafael; Mullen, Gregory E D; Wong, Wilson; Yan, Yong; Krger, Dirk; Khlobystov, Andrei N; Gimenez-Lopez, Maria; Semjeni, Mariann; Szigeti, Krisztin; Veres, Dniel S; Lu, Haizhou; Hernndez, Ignacio; Gillin, William P; Protti, Andrea; Petik, Katalin Kis; Green, Mark A; Blower, Philip J

    2016-02-17

    Multimodal nanoparticulate materials are described, offering magnetic, radionuclide, and fluorescent imaging capabilities to exploit the complementary advantages of magnetic resonance imaging (MRI), positron emission tomography/single-photon emission commuted tomography (PET/SPECT), and optical imaging. They comprise Fe3O4@NaYF4 core/shell nanoparticles (NPs) with different cation dopants in the shell or core, including Co0.16Fe2.84O4@NaYF4(Yb, Er) and Fe3O4@NaYF4(Yb, Tm). These NPs are stabilized by bisphosphonate polyethylene glycol conjugates (BP-PEG), and then show a high transverse relaxivity (r2) up to 326 mM(-1) s(-1) at 3T, a high affinity to [(18)F]-fluoride or radiometal-bisphosphonate conjugates (e.g., (64)Cu and (99m)Tc), and fluorescent emissions from 500 to 800 nm under excitation at 980 nm. The biodistribution of intravenously administered particles determined by PET/MR imaging suggests that negatively charged Co0.16Fe2.84O4@NaYF4(Yb, Er)-BP-PEG (10K) NPs cleared from the blood pool more slowly than positively charged NPs Fe3O4@NaYF4(Yb, Tm)-BP-PEG (2K). Preliminary results in sentinel lymph node imaging in mice indicate the advantages of multimodal imaging. PMID:26172432

  13. Synthesis, Characterization, and Application of Core–Shell Co0.16Fe2.84O4@NaYF4(Yb, Er) and Fe3O4@NaYF4(Yb, Tm) Nanoparticle as Trimodal (MRI, PET/SPECT, and Optical) Imaging Agents

    PubMed Central

    2015-01-01

    Multimodal nanoparticulate materials are described, offering magnetic, radionuclide, and fluorescent imaging capabilities to exploit the complementary advantages of magnetic resonance imaging (MRI), positron emission tomography/single-photon emission commuted tomography (PET/SPECT), and optical imaging. They comprise Fe3O4@NaYF4 core/shell nanoparticles (NPs) with different cation dopants in the shell or core, including Co0.16Fe2.84O4@NaYF4(Yb, Er) and Fe3O4@NaYF4(Yb, Tm). These NPs are stabilized by bisphosphonate polyethylene glycol conjugates (BP-PEG), and then show a high transverse relaxivity (r2) up to 326 mM–1 s–1 at 3T, a high affinity to [18F]-fluoride or radiometal-bisphosphonate conjugates (e.g., 64Cu and 99mTc), and fluorescent emissions from 500 to 800 nm under excitation at 980 nm. The biodistribution of intravenously administered particles determined by PET/MR imaging suggests that negatively charged Co0.16Fe2.84O4@NaYF4(Yb, Er)-BP-PEG (10K) NPs cleared from the blood pool more slowly than positively charged NPs Fe3O4@NaYF4(Yb, Tm)-BP-PEG (2K). Preliminary results in sentinel lymph node imaging in mice indicate the advantages of multimodal imaging. PMID:26172432

  14. Ce2AgYb5/3Se6, La2CuErTe5, and Ce2CuTmTe5: Three new quaternary interlanthanide chalcogenides

    NASA Astrophysics Data System (ADS)

    Babo, Jean-Marie; Albrecht-Schmitt, Thomas E.

    2013-01-01

    Three new ordered quaternary interlanthanide chalcogenides, Ce2AgYb5/3Se6, La2CuErTe5, and Ce2CuTmTe5, have been prepared by direct reaction of the elements in molten NaBr at 900 C. Each compound forms a new structure-type. The Ce2AgYb5/3Se6 structure consists of ?2{[} layers intercalated by Ce3+ cations. These layers are composed of ?1{[} quadruplet ribbons of [YbSe6]9- octahedra and infinite ?1{[} double chains of [AgSe5]9-. The La2CuErTe5 structure is made of one-dimensional ?1{[} ribbons separated by La3+ cations. These ribbons are formed by cis-edge sharing ?1{[} tetrahedral chains and trans-edge sharing ?1{[} chains. While La2CuErTe5 crystallizes in the orthorhombic space group Pnma, Ce2CuTmTe5 crystallizes in the monoclinic space group C2/m. The latter crystal structure is assembled from ?2{[} layers intercalated by Ce3+ cations. These layers consist of single ?1{[} chains connected to each other through dimers or pseudo-double chains.

  15. Rare-Earths Centers (Sm{sup 3+}, Eu{sup 3+}, Yb{sup 3+}) in MeF{sub 2}(Me = Ca, Sr, Ba, Cd) Crystals

    SciTech Connect

    Nikiforov, A. E.; Chernyshev, V. A.; Volodin, V. P.; Avram, N. M.; Avram, C. N.; Vaida, M.

    2010-08-04

    Rare-earth elements RE{sup 3+}(RE = Sm, Eu, Yb) form impurity centers in fluorite-like crystals MeF{sub 2}(Me = Ca, Sr, Ba, Cd). The crystal structure of cubic, trigonal and tetragonal centers in MeF{sub 2} has been investigated in the framework of shell model and pair potential approximation. The crystal field parameters were calculated with the exchange charges model, using the optimized geometry of the doped host matrix. With these parameters we have been calculated the optical spectra and spin-Hamiltonian (g-factors) of RE{sup 3+} in MeF{sub 2}, for some combination of R{sup 3+} and MeF{sup 2}. The obtained results were discussed and comparison with experimental data was made. A good agreement confirms the method and model of calculations.

  16. Tunnel-diode Resonator Spectroscopy of Quantum Levels in Cr12 Ln 4 (Ln=Y,Eu,Gd,Tb,Dy,Ho,Yb) Magnetic Molecules

    NASA Astrophysics Data System (ADS)

    Yeninas, Steven; Luban, Marshall; Prozorov, Ruslan; Coniglio, William A.; Agosta, Charles C.; Engelhardt, Larry; Timco, Grigore A.; Winnpenny, Richard E. P.

    2011-03-01

    The differential magnetic susceptibility for a series of Cr 12 Ln 4 (Ln=Y,Eu,Gd,Tb,Dy,Ho,Yb) magnetic molecules was measured in static (up to 16 T) and pulsed (up to 45 T) magnetic fields using a rf tunnel-diode resonator (TDR). At low temperatures, the behavior of these finite spin systems is governed by discrete energy spectra of the individual molecules. In magnetic field, low-energy quantum levels Zeeman-split, crossing at field values where magnetization exhibits a step corresponding to switching between different spin states. In high fields, we detect multiple level crossings which allow for a detailed mapping of the energy diagram. We then perform quantum Monte Carlo (QMC) using a Heisenberg Hamiltonian with three adjustable exchange constants whose values are chosen so as to optimize agreement with the experimental energy spectrum. The variations in results for the studied molecules are correlated to the magnetic properties of the lanthanide ions.

  17. Heterobinuclear Zn-Ln (Ln = La, Nd, Eu, Gd, Tb, Er and Yb) complexes based on asymmetric Schiff-base ligand: synthesis, characterization and photophysical properties.

    PubMed

    Zhao, Shunsheng; Liu, Xiangrong; Lü, Xingqiang; Wong, Wai-Kwok

    2013-01-01

    With a novel asymmetric Schiff-base zinc complex ZnL (H2 L = N-(3-methoxysalicylidene)-N'-(5-bromo-3-methoxysalicylidene)phenylene-1,2-diamine), obtained from phenylene-1,2-diamine, 3-methoxysalicylaldehyde and 5-bromo-3-methoxysalicylaldehyde, as the precursor, a series of heterobinuclear Zn-Ln complexes [ZnLnL(NO3 )3 (CH3 CN)] (Ln = La, 1; Ln = Nd, 2; Ln = Eu, 3; Ln = Gd, 4; Ln = Tb, 5; Ln = Er, 6; Ln = Yb, 7) were synthesized by the further reaction with Ln(NO3 )3 ·6H2 O, and characterized by Fourier transform-infrared, fast atom bombardment mass spectroscopy and elemental analysis. Photophysical studies of these complexes show that the strong and characteristic near-infrared luminescence of Nd(3+) , Yb(3+) and Er(3+) with emissive lifetimes in the microsecond range has been sensitized from the excited state of the asymmetric Schiff-base ligand due to effective intramolecular energy transfer; the other complexes do not show characteristic emission due to the energy gap between the chromophore and lanthanide ions. PMID:23001932

  18. Up-conversion emission tuning in triply-doped Yb3+/Tm3+/Er3+ novel fluoro-phosphate glass and glass-ceramics

    NASA Astrophysics Data System (ADS)

    Ledemi, Yannick; Trudel, Andrée.-Anne; Rivera, Victor A. G.; Messaddeq, Younes

    2014-03-01

    New Yb3+, Er3+ and Tm3+ triply doped fluoro-phosphate glasses belonging to the system NaPO3-YF3-BaF2-CaF2 have been prepared by the classical melt-casting technique. Glasses containing up to 10 wt.% of rare-earth ions fluorides have been obtained and characterized by using differential scanning calorimetry (DSC), UV-visible-near-infrared spectroscopy and up-conversion emission spectroscopy under excitation with a 975 nm laser diode. Transparent and optically homogeneous glass-ceramics have been reproducibly obtained by appropriate heat treatment in view to manage the red, green and blue emissions upon 975 nm laser excitation. According to the applied thermal heat-treatment, a large enhancement of intensity of the up-conversion emission - from 10 to 160 times higher - has been achieved in the glassceramics compared to that of glasses, suggesting incorporation of the rare-earth ions into the crystalline phase. Furthermore, a large range of color rendering has been observed in these materials by controlling the laser excitation power and material crystallization rate. Time-resolved luminescence experiments as well as X-ray diffractometry and scanning electron microscopy techniques have been employed in order to understand and correlate the multicolor emission changes to the crystallization behavior of this material. A progressive phase transformation of the fluorite-type CaF2-based nanocrystals initially generated was observed along with increasing heat-treatment time, thus modifying the rare earth ions spectroscopic features.

  19. New high pressure rare earth tantalates RExTa2O5+1.5x (RE=La, Eu, Yb)

    NASA Astrophysics Data System (ADS)

    Zibrov, Igor P.; Filonenko, Vladimir P.; Zakharov, Nikolai D.; Werner, Peter; Drobot, Dmitrii V.; Nikishina, Elena E.; Lebedeva, Elena N.

    2013-07-01

    Rare earth tantalates La0.075Ta2O5.113, Eu0.089Ta2O5.134 and Yb0.051Ta2O5.077 have been prepared by solid state reaction at P=7.0 GPa and T=1050-1100 C and studied by X-ray diffraction, thermal analysis and electron microscopy. Low hydrated amorphous tantalum, lanthanum, europium and ytterbium hydroxides were used as starting materials. Aqueous as well as anhydrous compounds were obtained. Title tantalates are crystallized in the structure type of F-Ta2O5 [Zibrov et al. Russ. J. Inorg. Chem. 48 (2003) 464-471] [5]. The structure was refined by the Rietveld method from X-ray powder diffractometer data: La0.075Ta2O5.113, a=10.5099(2), b=7.2679(1), c=6.9765(1) , V=532.90(1) 3, Z=6, space group Ibam; Eu0.089Ta2O5.134, a=10.4182(3), b=7.2685(1), c=6.9832(1) , V=528.80(2) 3, Z=6, space group Ibam; Yb0.051Ta2O5.077, a=10.4557(2), b=7.3853(1), c=6.8923(1) , V=532.21(1) 3, Z=6, space group Ibam. RE atoms do not replace the tantalum in its positions but the only water in the channels of the structure. Highly charged cations RE+3 compress the unit cell so that its volume becomes less than that of F-Ta2O5. Significant decrease of the unit cell volume after water removal from the structure is possible due to the puckering of pentagonal bipyramid layers and change of the corrugation angle in the layer.

  20. Single-component and warm-white-emitting phosphor NaGd(WO4)2:Tm3+, Dy3+, Eu3+: synthesis, luminescence, energy transfer, and tunable color.

    PubMed

    Liu, Yan; Liu, Guixia; Wang, Jinxian; Dong, Xiangting; Yu, Wensheng

    2014-11-01

    Tm(3+), Dy(3+), and Eu(3+) codoped NaGd(WO4)2 phosphors were prepared by a facile hydrothermal process; they were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy-dispersive X-ray spectrometer (EDS), photoluminescence spectra, and fluorescence lifetime. The results show that the novel octahedral microcrystals with a mean side length of 2 ?m are obtained. Under the excitation of ultraviolet, individual RE(3+) ion (Tm(3+), Dy(3+), and Eu(3+)) activated NaGd(WO4)2 phosphors exhibit excellent emission properties in their respective regions. Moreover, when codoping Dy(3+) and Eu(3+)/Tm(3+) in the single component, the energy migration from Dy(3+) to Eu(3+) has been demonstrated to be a resonant type via a dipole-quadrupole mechanism as well as that from Tm(3+) to Dy(3+) ions, of which the critical distance (R(Dy-Eu)) is calculated to be 11.08 . More significantly, in the Tm(3+), Dy(3+), and Eu(3+) tridoped NaGd(WO4)2 phosphors, the energy migration of Tm(3+)-Dy(3+)-Eu(3+), utilized for sensitizing Eu(3+) ions besides compensating the red component at low Eu(3+) doping concentration, has been discussed first. In addition, under 365 nm near-ultraviolet radiation (nUV), the color-tunable emissions in octahedral NaGd(WO4)2 microcrystals are realized by giving abundant blue, green, white, yellow, and red emissions, especially warm white emission, and could be favorable candidates in full-color phosphors for nUV-LEDs. PMID:25303406

  1. Spatial distribution of defects and the kinetics of nonequilibrium charge carriers in GaN wurtzite crystals doped with Sm, Eu, Er, Tm, and supplementary Zn impurities

    SciTech Connect

    Mezdrogina, M. M. Krivolapchuk, V. V.; Kozhanova, Yu. V.

    2008-02-15

    By analyzing time-resolved and steady-state photoluminescence spectra, it is established that the spatial distribution of rare-earth ion dopants in wurtzite GaN crystals doped with Sm, Eu, Er, or Tm is governed by the type and concentration of defects in the initial semiconductor matrix as well as by the type of the impurity (its capacity for segregation). Doping with multicharged rare-earth impurities and additionally introduced Zn impurity leads to an intensification of emission. The effect of intensification of emission in the case of n-and p-GaN crystals is considered with the use of the model of isoelectronic traps.

  2. Electric field gradient in bixbyite rare-earth oxides R2O3 (R=Tl, Eu, Lu, Tm) measured by perturbed angular correlation

    NASA Astrophysics Data System (ADS)

    Carbonari, A. W.; Mestnik-Filho, J.; Attili, R. N.; Moralles, M.; Saxena, R. N.

    1999-09-01

    The electric field gradient (EFG) at 111Cd nuclei dilutely substituting the cation site in bixbyite rare-earth oxides Tl2O3, Eu2O3, Lu2O3 and Tm2O3 has been measured using perturbed angular correlation technique. The 111In(EC) 111Cd probe nuclei were introduced into the samples by thermal diffusion. The experimental EFG values are compared with those calculated using the point charge model (PCM). The results are discussed in terms of a correlation between the electric field gradient and cation oxygen bond length in metal oxides.

  3. Chemical bond parameters and photoluminescence of a natural-white-light Ca9La(VO4)7:Tm3+,Eu3+ with one O2-?V5+ charge transfer and dual f-f transition emission centers

    NASA Astrophysics Data System (ADS)

    Li, Ling; Liu, Xiao Guang; Noh, Hyeon Mi; Jeong, Jung Hyun

    2015-01-01

    The relationship between the photoluminescence properties and the crystal structure of undoped, Eu3+ or/ and Tm3+ singly or codoped Ca9La(VO4)7 (CLaVO) samples was discussed. Under the excitation of UV light, CLaVO:Tm3+, CLaVO, and CLaVO:Eu3+ exhibit the characteristic emissions of Tm3+ (1G4?3H6, blue), O2-?V5+ charge transfer (CT), and Eu3+ (5D0?7F2, red), respectively. By adjusting the doping concentration of Tm3+ and Eu3+ ions in CLaVO, a natural white emission in a single composition with the color temperature at 6181 K was obtained. Based on the dielectric theory of complex crystal, the chemical bond parameters of La-O and V-O bonds were quantitatively calculated. The standard deviation of environmental factor of every bond (EFSD), which can be expressed as ? (hei) =?{ (1 / N) ? i = 1 N(hei - ?) 2 } (hei =(fci?bi) 1 / 2QBi and ? = (1 / N) ? i = 1 Nhei), was proposed to quantitatively express the distortion degree of VO43- from that of an ideal tetrahedron. The maximum change of EFSD comes from the [VO4]- tetrahedra in CLaVO sample by comparison with that of EFSD of isostructural Ca9Gd(VO4)7. This is possible the key reason that the undoped CLaVO sample has self-activated emission while the self-activated emission of its isostructural Ca9Gd(VO4)7 sample cannot be found. The quantitative calculation also demonstrated that the broad excitation bands at 319 nm in CLaVO:Tm and at 335 nm in CLaVO:Eu were due to the O-V2 and O-V3 (overlap with O-V2) CT, not the CT energy of O2--Eu13+ (O2--Tm13+), O2--Eu23+ (O2--Tm23+), and O2--Eu33+ (O2--Tm33+). The environmental factors surrounding the atoms V1, V2 and V3 were calculated to be 1.577, 1.6379 and 1.7554, respectively. It can be demonstrated that the excitation spectra at 319 nm for CLaVO:Tm and 335 nm for CLaVO:Eu came from the O-V2 and O-V3 CT, respectively.

  4. Photoluminescence properties of rare earths (Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+} and Tm{sup 3+}) activated NaInW{sub 2}O{sub 8} wolframite host lattice

    SciTech Connect

    Asiri Naidu, S.; Boudin, S.; Varadaraju, U.V.; Raveau, B.

    2012-01-15

    The photoluminescence (PL) studies on NaIn{sub 1-x}RE{sub x}W{sub 2}O{sub 8}, with RE=Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+} and Tm{sup 3+} phases have shown that the relative contribution of the host lattice and of the intra-f-f emission of the activators to the PL varies with the nature of the rare earth cation. In the case of Dy{sup 3+} and Tm{sup 3+} activators, with yellow and blue emission, respectively, the energy transfer from host to the activator plays a major role. In contrast for Eu{sup 3+}, with intense red emission, the host absorption is less pronounced and the intra-f-f transitions of the Eu{sup 3+} ions play a major role, whereas for Tb{sup 3+} intra-f-f transitions are only observed, giving rise to green emission. - Graphical abstract: NaInW{sub 2}O{sub 8} double tungstate doped with Eu{sup 3+}, Dy{sup 3+}, Tb{sup 3+}and Tm{sup 3+} shows characteristic emission of intense red for Eu{sup 3+}, yellow for Dy{sup 3+}, green for Tb{sup 3+} and blue for Tm{sup 3+}. Highlights: Black-Right-Pointing-Pointer Characteristic emissions of rare earths (Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+} and Tm{sup 3+}) are observed NaInW{sub 2}O{sub 8} wolframite. Black-Right-Pointing-Pointer Energy transfer from host to the activators (Eu{sup 3+} Dy{sup 3+} Tm{sup 3+} is observed. Black-Right-Pointing-Pointer PL properties of rare earth ions depend on minor structural variations in the host lattice.

  5. Preparation of a novel nanocomposite NaLuF4:Gd,Yb,Tm@SiO2@Ag@TiO2 with high photocatalytic activity driven by simulated solar light.

    PubMed

    Yin, Dongguang; Zhang, Lu; Cao, Xianzhang; Chen, Zhiwen; Tang, Jingxiu; Liu, Yumin; Zhang, Tingting; Wu, Minghong

    2016-01-28

    A novel nanocomposite photocatalyst NaLuF4:Gd,Yb,Tm@SiO2@Ag@TiO2 was developed for the first time. This composite material has a sandwich structure, including a NaLuF4:Gd,Yb,Tm upconversion nanocrystals (UCNCs) core, a media shell of amorphous SiO2 decorated with Ag nanoparticles, and an outer shell of anatase TiO2. The designed new structure takes advantage of the synergetic effect of UCNCs, Ag nanoparticles and TiO2. The UCNCs absorb near-infrared (NIR) light and transfer energy to TiO2, which extends the light responsive range of TiO2 to the NIR region. Ag nanoparticles not only enhance upconversion luminescence of the UCNCs but also enhance light harvesting and improve charge separation of TiO2. The results of photocatalytic applications show that the as-prepared catalyst has high photocatalytic activity. This study provides new insights into the fabrication of TiO2-based nanocomposite photocatalysts with high catalytic efficiency through effective integration of upconversion material, noble metal and TiO2 into a hetero-composite nanostructure. PMID:26673742

  6. Lattice dynamics of rare-earth titanates with the structure of pyrochlore R 2Ti2O7 ( R = Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu): Ab initio calculation

    NASA Astrophysics Data System (ADS)

    Chernyshev, V. A.; Petrov, V. P.; Nikiforov, A. E.

    2015-05-01

    The ab initio calculation has been performed for the crystal structure and the phonon spectrum of titanates with the structure of pyrochlore R 2Ti2O7 ( R = Gd-Lu). The frequencies and types of fundamental vibrations have been found. For R = Tb, Tm, and Yb, this calculation has been carried out for the first time; furthermore, there is no available information on experimental studies of the phonon spectrum for Tm and Yb. The influence of hydrostatic pressure to 35 GPa on the structure, dynamics, and elastic properties of the Gd2Ti2O7 lattice has been investigated. The dependence of the phonon frequencies on the pressure has been obtained. The calculations have predicted that the relative change in the pyrochlore structure volume during compression at pressures to 35 GPa is well described by the third-order Birch-Murnaghan equation of states. The results of the calculations agree with the available experimental data. It has been shown that the structural, dynamic, and elastic properties of the R 2Ti2O7 crystal lattice can be adequately described in the case where the inner shells of the RE ion up to 4 f are replaced by the pseudopotential.

  7. Highly uniform and monodisperse GdOF:Ln3+ (Ln = Eu, Tb, Tm, Dy, Ho, Sm) microspheres: hydrothermal synthesis and tunable-luminescence properties.

    PubMed

    Zhang, Yang; Kang, Xiaojiao; Geng, Dongling; Shang, Mengmeng; Wu, Yuan; Li, Xuejiao; Lian, Hongzhou; Cheng, Ziyong; Lin, Jun

    2013-10-21

    GdOF:Ln(3+) (Ln = Eu, Tb, Tm, Dy, Ho and Sm) microspheres (1.5 ?m) with high uniformity and monodispersity have been synthesized via a facile hydrothermal method followed by heat treatment (600 C). X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), as well as photoluminescence (PL) and cathodoluminescence (CL) spectra are used to characterize the resulting samples. A series of controlled experiments indicate that sodium citrate (Cit(3-)) as a shape modifier introduced into the reaction system plays a critical role in the shape evolution of the final products. Furthermore, the shape and size of the products can be further manipulated by adjusting the dosage of Cit(3-) and pH values in the initial solution. The possible formation mechanism for these microspheres has been presented. Under UV light and low-voltage electron beam excitation, GdOF:Ln(3+) microspheres show the characteristic f-f transitions of Ln(3+) (Eu, Tb/Ho, Tm, Dy and Sm) ions and give bright red, green, blue, yellow and yellowish-orange emission, respectively. In addition, multicolored luminescence containing white emission have been successfully confected for co-doped GdOF:Ln(3+) phosphors by changing the doped Ln(3+) ions and adjusting their doping concentrations due to the simultaneous luminescence of Ln(3+) in the GdOF host, making these materials have potential applications in field-emission display devices. PMID:23942823

  8. EPR study of the ground state of Mn2+ impurity ions in alumoborates MAl3(BO3)4 (M = Y, Eu, Tm)

    NASA Astrophysics Data System (ADS)

    Prokhorov, ? ?; Prokhorov, A. D.; Chernush, L. F.; Dyakonov, V. P.; Szymczak, H.; Dejneka, A.

    2015-06-01

    New data about the ground state of the Mn2+ impurity ions in a series of single crystals of alumbrados MAl3(BO3)4, where M = Y,Eu,Tm were obtained. The electron paramagnetic resonance (EPR) spectra of the Mn2+ spectra were studied, the parameters of the spin Hamiltonian describing the angular dependence of the spectrum were defined. It was shown that Mn2+ ions substitute trivalent ions of rare earth metals without changing the symmetry of the substitution site. The charge compensation process was found to be a nonlocal one. The cooling of the crystals leads to the increase of the splitting of the ground state, which is associated with the anisotropy of the thermal expansion coefficient. It was shown that an application of the superposition model to explain the distortions induced by an impurity Mn2+ ion has some limitations. The EPR linewidth of the Mn2+ ion in the TmAl3(BO3)4 crystal increases with increasing temperature as a result of the dipole-dipole and exchange interactions with the excited states of the host lattice Tm3+ ion.

  9. Observation of superconductivity at 30~46 K in A(x)Fe₂Se₂(A = Li, Na, Ba, Sr, Ca, Yb, and Eu).

    PubMed

    Ying, T P; Chen, X L; Wang, G; Jin, S F; Zhou, T T; Lai, X F; Zhang, H; Wang, W Y

    2012-01-01

    New iron selenide superconductors by intercalating smaller-sized alkali metals (Li, Na) and alkaline earths using high-temperature routes have been pursued ever since the discovery of superconductivity at about 30 K in KFe₂Se₂, but all have failed so far. Here we demonstrate that a series of superconductors with enhanced T(c) = 30∼46 K can be obtained by intercalating metals, Li, Na, Ba, Sr, Ca, Yb, and Eu in between FeSe layers by the ammonothermal method at room temperature. Analysis on their powder X-ray diffraction patterns reveals that all the main phases can be indexed based on body-centered tetragonal lattices with a∼3.755-3.831 Å while c∼15.99-20.54 Å. Resistivities show the corresponding sharp transitions at 45 K and 39 K for NaFe₂Se₂ and Ba₀.₈Fe₂Se₂, respectively, confirming their bulk superconductivity. These findings provide a new starting point for studying the properties of these superconductors and an effective synthetic route for the exploration of new superconductors as well. PMID:22645642

  10. Observation of superconductivity at 30∼46K in AxFe2Se2 (A = Li, Na, Ba, Sr, Ca, Yb, and Eu)

    PubMed Central

    Ying, T. P.; Chen, X. L.; Wang, G.; Jin, S. F.; Zhou, T. T.; Lai, X. F.; Zhang, H.; Wang, W. Y.

    2012-01-01

    New iron selenide superconductors by intercalating smaller-sized alkali metals (Li, Na) and alkaline earths using high-temperature routes have been pursued ever since the discovery of superconductivity at about 30 K in KFe2Se2, but all have failed so far. Here we demonstrate that a series of superconductors with enhanced Tc = 30∼46 K can be obtained by intercalating metals, Li, Na, Ba, Sr, Ca, Yb, and Eu in between FeSe layers by the ammonothermal method at room temperature. Analysis on their powder X-ray diffraction patterns reveals that all the main phases can be indexed based on body-centered tetragonal lattices with a∼3.755–3.831 Å while c∼15.99–20.54 Å. Resistivities show the corresponding sharp transitions at 45 K and 39 K for NaFe2Se2 and Ba0.8Fe2Se2, respectively, confirming their bulk superconductivity. These findings provide a new starting point for studying the properties of these superconductors and an effective synthetic route for the exploration of new superconductors as well. PMID:22645642

  11. Crystal structures of RPt{sub 3-x}Si{sub 1-y}(R=Y, Tb, Dy, Ho, Er, Tm, Yb) studied by single crystal X-ray diffraction

    SciTech Connect

    Gribanov, Alexander; Grytsiv, Andriy; Rogl, Peter; Seropegin, Yurii; Giester, Gerald

    2009-07-15

    The crystal structures of ternary compounds RPt{sub 3-x}Si{sub 1-y}(R=Y, Tb, Dy, Ho, Er, Tm, Yb) have been elucidated from X-ray single crystal CCD data. All compounds are isotypic and crystallize in the tetragonal space group P4/mbm. The general formula RPt{sub 3-x}Si{sub 1-y} arises from defects: x{approx}0.20, y{approx}0.14. The crystal structure of RPt{sub 3-x}Si{sub 1-y} can be considered as a packing of four types of building blocks which derive from the CePt{sub 3}B-type unit cell by various degrees of distortion and Pt, Si-defects. - Graphical Abstract: Electron density in RPt{sub 3-x}Si{sub 1-y} at 0, 1/2 , 0.

  12. Doxorubicin-loaded NaYF4:Yb/Tm-TiO2 inorganic photosensitizers for NIR-triggered photodynamic therapy and enhanced chemotherapy in drug-resistant breast cancers.

    PubMed

    Zeng, Leyong; Pan, Yuanwei; Tian, Ying; Wang, Xin; Ren, Wenzhi; Wang, Shouju; Lu, Guangming; Wu, Aiguo

    2015-07-01

    The combination therapy has exhibited important potential for the treatment of cancers, especially for drug-resistant cancers. In this report, bi-functional nanoprobes based on doxorubicin (DOX)-loaded NaYF4:Yb/Tm-TiO2 inorganic photosensitizers (FA-NPs-DOX) were synthesized for invivo near infrared (NIR)-triggered inorganic photodynamic therapy (PDT) and enhanced chemotherapy to overcome the multidrug resistance (MDR) in breast cancers. Using the up-conversion luminescence (UCL) performance of NaYF4:Yb/Tm converting near-infrared (NIR) into ultraviolent (UV) lights, reactive oxygen species (ROS) were triggered from TiO2 inorganic photosensitizers for PDT under the irradiation of a 980nm laser, by which the deep-penetration and low photo-damage could be reached. Moreover, nanocarrier delivery and folic acid (FA) targeting promoted the cellular uptake, and accelerated the release of DOX in drug-sensitive MCF-7 and resistant MCF-7/ADR cells. The toxicity assessment invitro and invivo revealed the good biocompatibility of the as-prepared FA-NPs-DOX nanocomposites. By the combination of enhanced chemotherapy and NIR-triggered inorganic PDT, the viability of MCF-7/ADR cells could decrease by 53.5%, and the inhibition rate of MCF-7/ADR tumors could increase up to 90.33%, compared with free DOX. Therefore, the MDR of breast cancers could be obviously overcome by enhanced chemotherapy and NIR-triggered inorganic PDT of FA-NPs-DOX nanocomposites under the excitation of a 980nm laser. PMID:25913254

  13. One-pot solvothermal synthesis of uniform layer-by-layer self-assembled ultrathin hexagonal Gd2O2S nanoplates and luminescent properties from single doped Eu3+ and codoped Er3+, Yb3+.

    PubMed

    Liu, Jie; Luo, Hongde; Liu, Pujun; Han, Lixian; Zheng, Xiao; Xu, Bo; Yu, Xibin

    2012-12-01

    Uniform Gd(2)O(2)S flower-like nano-assemblies were prepared through one-pot mild solvothermal synthesis. The parallel nanoplates are the building blocks, ?3 nm in thickness and 20-30 in diameter. Ethanediamine, the main solvent, plays an important role in dissolving a large amount of sulphur and producing active S(2-) ions, which results in the direct formation of Gd(2)O(2)S. Oleylamine, the capping agent, controls the growth of the plate-like structure. Under UV excitation, the Gd(2)O(2)S:Eu(3+) nano-phosphor shows good red luminescence with a main emission peak at 627 nm. Under 980 nm laser excitation, Gd(2)O(2)S:xYb(3+),1%Er(3+) nano-phosphors exhibit a tuneable emission, shifting from greenish-yellow to orange-yellow, with increasing Yb(3+) content. PMID:23033159

  14. New high pressure rare earth tantalates RE{sub x}Ta{sub 2}O{sub 5+1.5x} (RE=La, Eu, Yb)

    SciTech Connect

    Zibrov, Igor P.; Filonenko, Vladimir P.; Zakharov, Nikolai D.; Nikishina, Elena E.; Lebedeva, Elena N.

    2013-07-15

    Rare earth tantalates La{sub 0.075}Ta{sub 2}O{sub 5.113}, Eu{sub 0.089}Ta{sub 2}O{sub 5.134} and Yb{sub 0.051}Ta{sub 2}O{sub 5.077} have been prepared by solid state reaction at P=7.0 GPa and T=1050–1100 °C and studied by X-ray diffraction, thermal analysis and electron microscopy. Low hydrated amorphous tantalum, lanthanum, europium and ytterbium hydroxides were used as starting materials. Aqueous as well as anhydrous compounds were obtained. Title tantalates are crystallized in the structure type of F–Ta{sub 2}O{sub 5} [Zibrov et al. Russ. J. Inorg. Chem. 48 (2003) 464–471] [5]. The structure was refined by the Rietveld method from X-ray powder diffractometer data: La{sub 0.075}Ta{sub 2}O{sub 5.113}, a=10.5099(2), b=7.2679(1), c=6.9765(1) Å, V=532.90(1) Å{sup 3}, Z=6, space group Ibam; Eu{sub 0.089}Ta{sub 2}O{sub 5.134}, a=10.4182(3), b=7.2685(1), c=6.9832(1) Å, V=528.80(2) Å{sup 3}, Z=6, space group Ibam; Yb{sub 0.051}Ta{sub 2}O{sub 5.077}, a=10.4557(2), b=7.3853(1), c=6.8923(1) Å, V=532.21(1) Å{sup 3}, Z=6, space group Ibam. RE atoms do not replace the tantalum in its positions but the only water in the channels of the structure. Highly charged cations RE{sup +3} compress the unit cell so that its volume becomes less than that of F–Ta{sub 2}O{sub 5}. Significant decrease of the unit cell volume after water removal from the structure is possible due to the puckering of pentagonal bipyramid layers and change of the corrugation angle in the layer. - Graphical abstract: The structure of RE{sub x}Ta{sub 2}O{sub 5+1.5x} and its HRTEM image (“A” arrows show empty channel, “B” arrows show filled channel). - Highlights: • We synthesized new tantalates of RE under high pressure high temperature conditions. • RE atoms replace water molecules in the channels of the structure. • Aqueous as well as anhydrous tantalates were obtained. • Highly charged cations RE{sup +3} compress the unit cell decreasing RE–O distances.

  15. NaYF4:Yb,Tm nanocrystals and TiO2 inverse opal composite films: a novel device for upconversion enhancement and solid-based sensing of avidin

    NASA Astrophysics Data System (ADS)

    Xu, Sai; Xu, Wen; Wang, Yunfeng; Zhang, Shuang; Zhu, Yongsheng; Tao, Li; Xia, Lei; Zhou, Pingwei; Song, Hongwei

    2014-05-01

    Upconversion luminescence (UCL) detection based on rare-earth doped upconversion nanocrystals (UCNCs) as probes has been proved to exhibit a large anti-Stokes shift, no autofluorescence from biological samples, and no photobleaching. However, it is still a challenge to achieve a stable, reproducible solid-based UCL biosensor because of ineffective UCL of the UCNCs. In this work, we fabricated TiO2 inverse opal photonic crystals (IOPCs)/NaYF4:Yb3+,Tm3+ (Er3+) UCNC composite films, which can tremendously improve the overall UCL of Tm3+ as high as 43-fold. Based on the fluorescence resonance energy transfer (FRET) and the specific interaction between biotin and avidin, a novel solid-based UC biosensor is presented for sensing avidin. This solid-based detection system is convenient for detection, and also can offer two parameters for detecting trace amounts of avidin, namely, the emission intensity and the fluorescence decay time. The sensor has a high sensitivity of 34 pmol-1, a good linear relationship of 0.996 and a low detection limit of 48 pmol. It also exhibits excellent long-time photostability, and the absence of autofluorescence, and thus may have great potential for versatile applications in biodetection.

  16. Low-temperature superstructures of a series of Cd6M (M = Ca, Y, Sr, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) crystalline approximants.

    PubMed

    Nishimoto, Kazue; Sato, Takeru; Tamura, Ryuji

    2013-06-12

    The low-temperature (LT) superstructure and the phase transition temperature have been investigated for a series of Cd6M crystalline approximants by transmission electron microscopy as well as electrical resistivity measurements. Except for M = Lu, Cd6M is found to undergo a phase transition to a monoclinic phase at a low temperature and the transition temperature (Tc) scales well with the size of the M atom. For M = Ca, Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Tm the LT superstructure is explained by a ?2a a ?2a lattice with the space group C2/c, and for M = Sr and Yb a ?2a 2a ?2a monoclinic lattice with P2/m. On the other hand, no phase transition is observed for M = Lu, indicating that a Cd4 tetrahedron at the cluster center remains disordered down to the lowest temperature, i.e. 16 K. It is shown that the volume inside the Cd20 dodecahedron plays a crucial role in the occurrence of the phase transition, and long-term aging in particular promotes the phase transition for late rare-earth elements such as Ho, Er and Tm, suggesting that the transition is sensitive to and is even hindered by disorder such as atomic vacancies. The absence of the transition for M = Lu is attributed to the highest activation energy for the transition due to the smallest volume inside the Cd20 dodecahedron. PMID:23685563

  17. Laser-diode-excited blue upconversion in Tm3+/Yb3+ -codoped TeO2-Ga2O3-R2O (R=Li, Na, K) glasses.

    PubMed

    Zhao, Chun; Zhang, Qinyuan; Yang, Gangfeng; Jiang, Zhonghong

    2008-01-01

    This paper reports on intense blue upconversion in Tm(3+)/Yb(3+) codoped TeO(2)-Ga(2)O(3)-R(2)O(R=Li, Na, K) glasses upon excitation with commercial available laser diode (LD). Effects of alkali ions on the Raman spectra, thermal stability and spectroscopic properties of the tellurite-gallium glasses have also been investigated. Energy transfer and the involved upconversion mechanisms have been discussed. Intense blue upconversion emission centered at 476 nm along with a weak red emission at 650 nm has been observed upon excitation of 977 nm LD, assigned to the transitions of 1G4-->3H6, and 1G4-->3H4 and/or 3F(2,3)-->3H6 of Tm(3+), respectively. The blue upconversion intensity has a cubelike dependence on incident pump laser power, indicating a three-photon process. However, a quadratic dependence of the 476 nm upconversion intensity on the incident pump laser power has been observed when samples under excitation of 808 nm LD due to a two-photon absorption process. Enhanced upconversion luminescence have been observed with replacing K(+) for Na(+) and Li(+). PMID:17823854

  18. Ag{sub 2}O dependent up-conversion luminescence properties in Tm{sup 3+}/Er{sup 3+}/Yb{sup 3+} co-doped oxyfluorogermanate glasses

    SciTech Connect

    Hu, Yuebo; Qiu, Jianbei Song, Zhiguo; Zhou, Dacheng

    2014-02-28

    Up-conversion (UC) luminescence properties of Ag/Tm{sup 3+}/Er{sup 3+}/Yb{sup 3+} co-doped oxyfluorogermanate glasses have been studied to assess the effective role of silver nanoparticles as a sensitizer for Tm{sup 3+} and Er{sup 3+} ions. The X-ray diffraction patterns obtained in this work do not reveal any crystalline phase in the glass. However, the absorption spectra reveal that surface plasmons resonance band of Ag undergoes a distinct split with two maxima and a very broad absorption peak with a background that extends toward the near infrared (NIR) with the increasing of Ag{sub 2}O added concentration. Transmission electron microscope images confirm that silver nanoparticles have been precipitated from matrix glasses and show their distribution, size, and shapes. In addition, changes in UC luminescence intensity of four emission bands 476, 524, 546, and 658 nm corresponding to {sup 1}G{sub 4} → {sup 3}H{sub 6} (Tm{sup 3+}), ({sup 2}H{sub 11/2}, {sup 4}S{sub 3/2}) → {sup 4}I{sub 15/2} (Er{sup 3+}), and {sup 4}F{sub 9/2} → {sup 4}I{sub 15/2} (Er{sup 3+}) transitions, respectively, as a function of silver addition to the base composition have been measured under 980 nm excitation. It is confirmed that Ag{sub 2}O added concentration plays an important role in increasing the UC luminescence intensity; however, further increase in Ag{sub 2}O added concentration reduces the intensity.

  19. Up/down conversion luminescence and charge compensation investigation of Ca0.5Y1-x(WO4)2:xLn3+ (Ln = Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors

    NASA Astrophysics Data System (ADS)

    Mahalingam, Venkatakrishnan; Thirumalai, Jagannathan; Krishnan, Rajagopalan; Mantha, Srinivas

    2016-01-01

    Microstructures of Ca0.5Y(1-x)(WO4)2:xLn3+ (Ln = Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors were prepared via the solid-state reaction method. X-ray diffraction, scanning electron microscopy and photoluminescence were used to characterize the prepared phosphor samples. The results reveal that the phosphor samples have single phase scheelite structures with tetragonal symmetry of I41/a. The down/up conversion photoluminescence of the Ca0.5Y(1-x)(WO4)2:xLn3+ (Ln = Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors properties reveal characteristic visible emissions. The energy transfer process, fluorescence lifetime and color coordinates are discussed in detail. Furthermore, the phosphor Ca0.5Y(1-x)(WO4)2:xPr3+ co-doped with alkali chlorides shows the enhancement of luminescence, which was found in the sodium chloride co-doped powder phosphor. The photometric characteristics indicate the suitability of the inorganic powder phosphors for solid-state lighting and display applications.

  20. Up/down conversion luminescence and charge compensation investigation of Ca0.5Y1-x(WO4)2:xLn(3+) (Ln=Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors.

    PubMed

    Mahalingam, Venkatakrishnan; Thirumalai, Jagannathan; Krishnan, Rajagopalan; Mantha, Srinivas

    2016-01-01

    Microstructures of Ca0.5Y(1-x)(WO4)2:xLn(3+) (Ln=Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors were prepared via the solid-state reaction method. X-ray diffraction, scanning electron microscopy and photoluminescence were used to characterize the prepared phosphor samples. The results reveal that the phosphor samples have single phase scheelite structures with tetragonal symmetry of I41/a. The down/up conversion photoluminescence of the Ca0.5Y(1-x)(WO4)2:xLn(3+) (Ln=Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors properties reveal characteristic visible emissions. The energy transfer process, fluorescence lifetime and color coordinates are discussed in detail. Furthermore, the phosphor Ca0.5Y(1-x)(WO4)2:xPr(3+) co-doped with alkali chlorides shows the enhancement of luminescence, which was found in the sodium chloride co-doped powder phosphor. The photometric characteristics indicate the suitability of the inorganic powder phosphors for solid-state lighting and display applications. PMID:26208272

  1. Low-temperature superstructures of a series of Cd6M (M = Ca, Y, Sr, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) crystalline approximants

    NASA Astrophysics Data System (ADS)

    Nishimoto, Kazue; Sato, Takeru; Tamura, Ryuji

    2013-06-01

    The low-temperature (LT) superstructure and the phase transition temperature have been investigated for a series of Cd6M crystalline approximants by transmission electron microscopy as well as electrical resistivity measurements. Except for M = Lu, Cd6M is found to undergo a phase transition to a monoclinic phase at a low temperature and the transition temperature (Tc) scales well with the size of the M atom. For M = Ca, Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Tm the LT superstructure is explained by a \\sqrt{2}a\\times a\\times \\sqrt{2}a lattice with the space group C2/c, and for M = Sr and Yb a \\sqrt{2}a\\times 2 a\\times \\sqrt{2}a monoclinic lattice with P2/m. On the other hand, no phase transition is observed for M = Lu, indicating that a Cd4 tetrahedron at the cluster center remains disordered down to the lowest temperature, i.e. 16 K. It is shown that the volume inside the Cd20 dodecahedron plays a crucial role in the occurrence of the phase transition, and long-term aging in particular promotes the phase transition for late rare-earth elements such as Ho, Er and Tm, suggesting that the transition is sensitive to and is even hindered by disorder such as atomic vacancies. The absence of the transition for M = Lu is attributed to the highest activation energy for the transition due to the smallest volume inside the Cd20 dodecahedron.

  2. Magnetic properties of the RPO 4(MoO 3) 12 30H 2O compounds, R = Ce, Pr, Nd, Tb, Ho, Tm, and Yb

    NASA Astrophysics Data System (ADS)

    Corruccini, L. R.; van der Noordaa, J. T.; White, Steven J.; Hope, Hkon

    1997-09-01

    Magnetic susceptibilities of a number of the rare earth ( R) phosphomolybdates, RPO 4(MoO 3) 12 30H 2O, have been measured from 300 K down to ? 10 mK. These materials are cubic, with space group Fd overline3, and are characterized by weak crystalline field splittings. Most can be explained in terms of a lowest order theory for a crystal field with T d ( overline43 m) symmetry, but those of Tb, Ho, and Tm disagree. The discrepancy appears to be due to disorder in the position of the cations about the 8 a sites.

  3. Electronic states of R F e2O4(R =Lu ,Yb ,Tm ,Y ) mixed-valence compounds determined by soft x-ray absorption spectroscopy and x-ray magnetic circular dichroism

    NASA Astrophysics Data System (ADS)

    Lafuerza, Sara; Garca, Joaqun; Subas, Gloria; Blasco, Javier; Herrero-Martn, Javier; Pascarelli, Sakura

    2014-12-01

    We here report an investigation of the electronic states in the R F e2O4(R =Lu ,Yb ,Tm ,Y ) mixed-valence ferrites by means of soft x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements together with ab initio theoretical calculations. The presence of Fe+2 and Fe+3 pure ionic species is discarded in the XAS spectra at the O K edge in both experimental data and simulations based on the multiple scattering theory. Similarly, no trace of F e+2/F e+3 contributions is detected in the XMCD spectra at the Fe K edge. On the other hand, the XAS and XMCD spectra at the Fe L2 ,3 edges can be well described in terms of F e+2/F e+3 contributions, and are also supported by multiplet calculations. This finding can be interpreted as the existence of a mixture of 3 d5/3 d6 configurations at the Fe atoms. Alternative ferrimagnetic spin orderings based on a trimodal Fe valence distribution are also proposed and discussed. Finally, a possible explanation for the strong dependence of the Fe L2 ,3 edges XMCD signal magnitude on both the sample surface preparation and detection method is presented.

  4. Enhanced dual contrast agent, Co(2+)-doped NaYF4:Yb(3+),Tm(3+) nanorods, for near infrared-to-near infrared upconversion luminescence and magnetic resonance imaging.

    PubMed

    Xia, Ao; Zhang, Xiaofeng; Zhang, Jun; Deng, Yunyun; Chen, Qiang; Wu, Shishan; Huang, Xiaohua; Shen, Jian

    2014-11-01

    Dual-modality imaging with magnetic resonance (MR) and upconversion luminescence (UCL) is a promising technique for molecular imaging in biomedical research. Multifunctional lanthanide-based nanoparticles have been widely investigated as agents for contrast enhanced MR and fluorescence imaging. However, the use of rare earth fluoride nanoparticles for dual-modality imaging of T2-weighted MR and UCL is rarely reported. We find that NaYF4:Yb(3+),Tm(3+),Co(2+) (MUC) nanorods can be applied as a high-performance dual contrast agent for both T2-weighted MR and UCL dual-modality imaging. After modification with 6-O-carboxymethyl chitosan (OCC), MUC nanorods can be endocytosed by cells without showing signs of cytotoxicity. High-quality UCL images of living cells incubated with MUC-OCC nanorods were acquired on a near-infrared (NIR) confocal microscopy under the excitation at 980nm. Moreover, MUC-OCC nanorods display high transverse (r2) relaxivities invitro. The application of low-dose MUC-OCC nanorods for NIR-to-NIR UCL and MR dual-modality invivo imaging was also carried out successfully. In addition, the toxicity of MUC-OCC nanorods was evaluated by MTT assay, serological tests and histological analysis of visceral organs. PMID:25108318

  5. Structure determination of KScS?, RbScS? and KLnS? (Ln = Nd, Sm, Tb, Dy, Ho, Er, Tm and Yb) and crystal-chemical discussion.

    PubMed

    Havlk, Lubomr; Fbry, Jan; Henriques, Margarida; Duek, Michal

    2015-07-01

    The title structures of KScS2 (potassium scandium sulfide), RbScS2 (rubidium scandium sulfide) and KLnS2 [Ln = Nd (potassium neodymium sufide), Sm (potassium samarium sulfide), Tb (potassium terbium sulfide), Dy (potassium dysprosium sulfide), Ho (potassium holmium sulfide), Er (potassium erbium sulfide), Tm (potassium thulium sulfide) and Yb (potassium ytterbium sulfide)] are either newly determined (KScS2, RbScS2 and KTbS2) or redetermined. All of them belong to the ?-NaFeO2 structure type in agreement with the ratio of the ionic radii r(3+)/r(+). KScS2, the member of this structural family with the smallest trivalent cation, is an extreme representative of these structures with rare earth trivalent cations. The title structures are compared with isostructural alkali rare earth sulfides in plots showing the dependence of several relevant parameters on the trivalent cation crystal radius; the parameters thus compared are c, a and c/a, the thicknesses of the S-S layers which contain the respective constituent cations, the sulfur fractional coordinates z(S(2-)) and the bond-valence sums. PMID:26146403

  6. (α-NaYbF4:Tm3+)/CaF2 Core/Shell Nanoparticles with Efficient Near-Infrared to Near-Infrared Upconversion for High-Contrast Deep Tissue Bioimaging

    PubMed Central

    Chen, Guanying; Shen, Jie; Ohulchanskyy, Tymish Y.; Patel, Nayan J.; Kutikov, Artem; Li, Zhipeng; Song, Jie; Pandey, Ravindra K.; Ågren, Hans; Prasad, Paras N.; Han, Gang

    2012-01-01

    We describe the development of novel and biocompatible core/shell (α-NaYbF4:Tm3+)/CaF2 nanoparticles which exhibit highly efficient NIRin-NIRout upconversion (UC) for high contrast and deep bioimaging. When excited at ~980 nm, these nanoparticles emit photoluminescence (PL) peaked at ~800 nm. The quantum yield of this UC PL under low power density excitation (~0.3 W/cm2) is 0.6±0.1%. This high UC PL efficiency is realized by suppressing surface quenching effects via hetero-epitaxial growth of a biocompatible CaF2 shell which results in a 35-fold increase in the intensity of UC PL from the core. Small animal whole-body UC PL imaging with exceptional contrast (signal-to-background ratio of 310) is shown using BALB/c mice intravenously injected with aqueously dispersed nanoparticles (700 pmol/kg). High-contrast UC PL imaging of deep tissues is also demonstrated, using a nanoparticle-loaded synthetic fibrous mesh wrapped around rat femoral bone, and a cuvette with nanoparticle aqueous dispersion - covered with a 3.2-cm thick animal tissue (pork). PMID:22928629

  7. The high-pressure synthesis and characterization of some praseodymium-substituted rare-earth-based R{sub 2}Ba{sub 4}Cu{sub 7}O{sub 14-{delta}} (R = Nd, Eu, Tm)

    SciTech Connect

    Teng-Ming Chen; Kao, F.S.

    1997-08-01

    The formation of phases in the (R{sub 1-x}Pr{sub x}){sub 2}Ba{sub 4}Cu{sub 7}O{sub 14+{delta}} (Pr-doped R247; R = Nd, Eu, Tm) system with x = 0-1.0 was investigated. Samples of the title series were synthesized at 980-990{degree}C at 25 bar O{sub 2}, followed by annealing at 300{degree}C under 130 bar O{sub 2} for 30 hr. Oxygen content of the samples has been determined by iodometric titration. Single-phased samples has been determined by iodometric titration. Single-phased samples were obtained with x smaller than or equal to 0.3, 0.4, and 0.4 for R = Nd, Eu, and Tm, respectively, as indicated by X-ray diffraction measurements. With increasing amount of Pr substituting for R, the cell dimensions of the Pr-doped R247 phases were found to expand steadily, whereas the corresponding structural orthorhombicity was observed to decrease systematically. Superconducting transition temperatures (T{sub c}`s) of the title phases were found to be significantly suppressed upon Pr doping, as indicated by field-cooled temperature-dependent magnetization studies. The effect of Pr substitution on T{sub c}`s of R247 (R = Y, Eu, Er, Tm, Nd, Dy) phases was investigated and compared as a function of R{sup 3+} radii, but no size dependence effect was observed. In addition, field-dependent magnetization studies for a series of (Eu{sub 1-x}Pr{sub x}){sub 2}Ba{sub 4}Cu{sub 7}O{sub 14+{delta}} samples with x = 0, 0.2, and 0.4, respectively, are also reported.

  8. Novel light-conversion hybrids of SBA-16 functionalized with rare earth (Eu3+, Nd3+, Yb3+) complexes of modified 2-methyl-9-hydroxyphenalenone and 1,10-phenanthroline

    NASA Astrophysics Data System (ADS)

    Gu, Yan-Jing; Yan, Bing; Qiao, Xiao-Fei

    2013-03-01

    Novel rare earth complex-functionalized mesoporous SBA-16-type hybrid materials are synthesized by the co-condensation of modified 2-methyl-9-hydroxyphenalenone (MHPOSi), from modified 3-(triethoxysilyl)-propyl isocyanate (TEPIC), and tetraethoxysilane (TEOS) in the presence of Pluronic F127 as a template. These inorganic-organic mesoporous hybrids are characterized by FT-IR spectra, small-angle X-ray diffraction (SAXRD), N2 adsorption-desorption measurements, thermal analysis and spectroscopy. Their photophysical properties, which show novel light conversion properties, are discussed in detail. The Eu3+ hybrid system shows ultraviolet excitation and visible emission, and the Nd+ and Yb3+ hybrids exhibit visible excitation and NIR emission.

  9. Ce{sub 2}AgYb{sub 5/3}Se{sub 6}, La{sub 2}CuErTe{sub 5}, and Ce{sub 2}CuTmTe{sub 5}: Three new quaternary interlanthanide chalcogenides

    SciTech Connect

    Babo, Jean-Marie; Albrecht-Schmitt, Thomas E.

    2013-01-15

    Three new ordered quaternary interlanthanide chalcogenides, Ce{sub 2}AgYb{sub 5/3}Se{sub 6}, La{sub 2}CuErTe{sub 5}, and Ce{sub 2}CuTmTe{sub 5}, have been prepared by direct reaction of the elements in molten NaBr at 900 Degree-Sign C. Each compound forms a new structure-type. The Ce{sub 2}AgYb{sub 5/3}Se{sub 6} structure consists of {infinity}{sup 2}{l_brace} [AgYb{sub 5/6}Se{sub 6}]{sup 6-}{r_brace} layers intercalated by Ce{sup 3+} cations. These layers are composed of {infinity}{sup 1}{l_brace} [Yb{sub 5/3}Se{sub 6}]{sup 7-}{r_brace} quadruplet ribbons of [YbSe{sub 6}]{sup 9-} octahedra and infinite {infinity}{sup 1}{l_brace} [AgSe{sub 6}]{sup 11-}{r_brace} double chains of [AgSe{sub 5}]{sup 9-}. The La{sub 2}CuErTe{sub 5} structure is made of one-dimensional {infinity}{sup 1}{l_brace} [CuErTe{sub 5}]{sup 6-}{r_brace} ribbons separated by La{sup 3+} cations. These ribbons are formed by cis-edge sharing {infinity}{sup 1}{l_brace} [CuTe{sub 2}]{sup 3-}{r_brace} tetrahedral chains and trans-edge sharing {infinity}{sup 1}{l_brace} [ErTe{sub 4}]{sup 5-}{r_brace} chains. While La{sub 2}CuErTe{sub 5} crystallizes in the orthorhombic space group Pnma, Ce{sub 2}CuTmTe{sub 5} crystallizes in the monoclinic space group C2/m. The latter crystal structure is assembled from {infinity}{sup 2}{l_brace} [CuTmTe{sub 5}]{sup 6-}{r_brace} layers intercalated by Ce{sup 3+} cations. These layers consist of single {infinity}{sup 1}{l_brace} [TmTe{sub 4}]{sup 5-}{r_brace} chains connected to each other through dimers or pseudo-double chains. - Graphical abstract: [CuTe{sub 4}]{sup 7-} tetrahedra sharing cis-edges to yield chains in the La{sub 2}CuErTe{sub 5}. Highlights: Black-Right-Pointing-Pointer New ordered interlanthanide tellurides. Black-Right-Pointing-Pointer New quaternary chalcogenides. Black-Right-Pointing-Pointer Low-dimensional lanthanide chalcogenide substructures. Black-Right-Pointing-Pointer Flux synthesis of new chalcogenides.

  10. Preparation and spectroscopic properties of rare-earth (RE) (RE = Sm, Eu, Tb, Dy, Tm)-activated K{sub 2}LnZr(PO{sub 4}){sub 3} (Ln = Y, La, Gd and Lu) phosphate in vacuum ultraviolet region

    SciTech Connect

    Zhang, Zhi-Jun; Lin, Xiao; Graduate School of Chinese Academy of Science, Beijing, 100039 ; Zhao, Jing-Tai; Zhang, Guo-Bin

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ? We report the VUV spectroscopic properties of rare-earth ions in K{sub 2}LnZr(PO{sub 4}){sub 3}. ? The O{sup 2?}-Eu{sup 3+} charge transfer bands at about 220 nm have been observed. ? The 4f5d spin-allowed and spin-forbidden transitions of Tb{sup 3+} have been observed. ? There is energy transfer between the host and rare-earth activators. -- Abstract: Rare earth (RE = Sm, Eu, Tb, Dy and Tm)-activated K{sub 2}LnZr(PO{sub 4}){sub 3} (Ln = Y, La, Gd and Lu) have been synthesized by solid-state reaction method, and their vacuum ultraviolet (VUV) excitation luminescent characteristics have been investigated. The band in the wavelength range of 130157 nm and the other one range from 155 to 216 nm with the maximum at about 187 nm in the VUV excitation spectra of these compounds are attributed to the host lattice absorption and OZr charge transfer transition, respectively. The charge transfer bands (CTB) of O{sup 2?}-Sm{sup 3+}, O{sup 2?}-Dy{sup 3+} and O{sup 2?}-Tm{sup 3+}, in Sm{sup 3+}, Dy{sup 3+} and Tm{sup 3+}-activated samples, have not been obviously observed probably because the 2p electrons of oxygen are tightly bound to the zirconium ion in the host lattice. For Eu{sup 3+}-activated samples, the relatively weak O{sup 2?}-Eu{sup 3+} CTB at about 220 nm is observed. And for Tb{sup 3+}-activated samples, the bands at 223 and 258 nm are related to the 4f-5d spin-allowed and spin-forbidden transitions of Tb{sup 3+}, respectively. It is observed that there is energy transfer between the host lattice and the luminescent activators (e.g. Eu{sup 3+}, Tb{sup 3+}). From the standpoint of luminescent efficiency, color purity and chemical stability, K{sub 2}GdZr(PO{sub 4}){sub 3}:Sm{sup 3+}, Eu{sup 3+}, Tb{sup 3+} are attractive candidates for novel yellow, red, green-emitting PDP phosphors.

  11. Multitemperature crystal structures and physical properties of the partially filled thermoelectric skutterudites M0.1Co4Sb12(M=La,Ce,Nd,Sm,Yb,andEu)

    NASA Astrophysics Data System (ADS)

    Mi, Jian-Li; Christensen, Mogens; Nishibori, Eiji; Iversen, Bo Brummerstedt

    2011-08-01

    Partially filled skutterudites with nominal compositions of M0.1Co4Sb12 (M = La, Ce, Nd, Sm, Yb; and Eu) were investigated by multitemperature (90-700 K) synchrotron radiation powder x-ray diffraction (SR-PXRD), and electrical and thermal transport property, heat capacity, and Hall effect measurements were also taken. The filling fractions, i.e., the occupancy factors of the guest atoms, were obtained from structure refinement of the SR-PXRD data, and they reflect the capacity for the individual guest atom species to fill the voids of the CoSb3 structure. The filling fraction of the lanthanide guest ions correlates with their effective ionic radii and valences, and the larger the ionic radii or the lower the charge state, the larger is the occupancy. Due to the different guest atom occupancies, the doping levels vary among the samples, and they are in a good agreement with the measured charge carrier concentrations, except for the magnetic samples (Sm, Eu). Anomalously large atomic displacement parameters (ADPs) are observed for the weakly bonded guest atoms, in agreement with the rattling concept, but no correlation is observed between the magnitude of the ADP and the ionic radius of the guest atom. Einstein and Debye temperatures were derived from analysis of the multitemperature ADPs of guest atoms and the framework atoms, respectively, and this analysis also shows that neither the guest atoms nor the host structure atoms contain large disorder contributions to their ADPs. In ternary skutterudites without host structure substitution or disorder, partial guest filling can affect the lattice thermal conductivity (?L) either by direct phonon-phonon interaction or through the inherent structural disorder introduced with the partial occupancy of the voids. The present data suggest that the magnitude of the guest atom ADPs correlates with ?L, and the larger the ADP, the lower is the ?L.

  12. Two new ternary lanthanide antimony chalcogenides: Yb{sub 4}Sb{sub 2}S{sub 11.25} and Tm{sub 4}Sb{sub 2}Se{sub 11.68} containing chalcogenide Q{sup 2-} and dichalcogenide (Q{sub 2}){sup 2-} anions

    SciTech Connect

    Babo, Jean-Marie; Albrecht-Schmitt, Thomas E.

    2012-03-15

    Dark red and dark brown crystals of Yb{sub 4}Sb{sub 2}S{sub 11.25} and Tm{sub 8}Sb{sub 4}Se{sub 11.68}, respectively, were obtained from the reaction of the elements in Sb{sub 2}Q{sub 3} (Q=S, Se) fluxes. Both non-stoichiometric compounds are orthorhombic and crystallize in the same space group Pnnm, with two formula units per unit cell (a=12.446(2), b=5.341(1), c=12.058(2) for sulfide and a=13.126(2), b=5.623(1), c=12.499(2) for the selenide). Their crystal structures are dominated by lanthanide-chalcogenide polyhedra (CN=7 and 8), which share corners, edges, triangular- and square-faces to form a three-dimensional framework embedding antinomy cations. The latter are coordinated by three sulfide anions with 5(1+2+2) secondary contacts forming basically infinite chains running along [0 1 0]. The chalcogens in both compounds form chalcogenide Q{sup 2-} and dichalcogenide (Q{sub 2}){sup 2-} anionic units. The optical analysis made on those compounds shows that both are semiconductors with band gap of 1.71 and 1.22 eV for Yb{sub 4}Sb{sub 2}S{sub 11.25} and Tm{sub 4}Sb{sub 2}Se{sub 11.75,} respectively. - Graphical Abstract: The crystal structure of Yb{sub 4}Sb{sub 2}S{sub 11} viewed along the [0 1 0]. Highlights: Black-Right-Pointing-Pointer Lanthanide chalcogenides. Black-Right-Pointing-Pointer Semiconductors. Black-Right-Pointing-Pointer Tunnel structures. Black-Right-Pointing-Pointer Lone-pair effects.

  13. Terpyridine-based heteroditopic ligand for Ru(II)Ln3(III) metallostar architectures (Ln = Gd, Eu, Nd, Yb) with MRI/optical or dual-optical responses.

    PubMed

    Boulay, Alexandre; Deraeve, Cline; Vander Elst, Luce; Leygue, Nadine; Maury, Olivier; Laurent, Sophie; Muller, Robert N; Mestre-Voegtl, Batrice; Picard, Claude

    2015-02-16

    A new ditopic ligand (L) based on a 2,2':5',4?-terpyridine unit substituted in the 2?,6? positions with iminodiacetate arms has been designed and synthesized for the construction of Ru(II)L3Ln3(III) supramolecular architectures. The two components of this system, a 2,2'-bipyridine unit for Ru(II) coordination and a pyridine-bis(iminodiacetate) core for Ln(III) coordination, are tightly connected via a covalent Carom(py)-Carom(py) bond. The paramagnetic and photophysical properties of the corresponding tetrametallic Ru(II)L3Gd3(III) complex have been evaluated, highlighting the potential of this metallostar structure to act as a bimodal MRI/optical imaging agent. Variable-temperature (17)O NMR and proton nuclear magnetic relaxation dispersion (NMRD) measurements showed that this complex exhibits (i) a remarkable relaxivity per metallostar molecule, particularly at clinical and high magnetic fields (r1(310K) = 51.0 and 36.0 mM(-1) s(-1) at 20 and 300 MHz, respectively) and (ii) a near-optimal residence lifetime of Gd(III) coordinated water molecule (?M(310K) = 77.5 ns). This is the result of the presence of two inner-sphere water molecules in the Gd(III) components of the metallostar and a slow tumbling rate of the molecule (?R(310K) = 252 ps). Upon excitation in the visible domain (?exc = 472 nm), the Ru(II) component of the complex exhibits a bright-red luminescence centered at 660 nm with a quantum yield of 2.6% in aqueous solutions at pH 7.4. Moreover, this Ru(II)L3Gd3(III) assembly is also characterized by a high kinetic inertness in biological media (PBS and human serum solutions) and a high photostability (photobleaching). Finally, preliminary photophysical studies on RuL3Nd3 and RuL3Yb3 assemblies revealed that the Ru(II) center acts as an effective sensitizer for Ln(III)-based luminescence in the near-IR region. The Nd(III) species was found to be the most effective at quenching the (3)MLCT luminescence of the Ru center. PMID:25594876

  14. Green upconversion in Y2O3:Yb nanopowder

    NASA Astrophysics Data System (ADS)

    Horvat, Darja; Lazar, Dušan; Možina, Janez; Križan, Janez; Diaci, Janez; Terzić, Mira

    2015-01-01

    Green emission lines, in addition to the blue and the red, were observed upon 980 nm excitation in yttrium oxide (Y2O3) nanopowder codoped with Yb and Tm, synthesized by the chemical combustion method. Upconversion emission studies suggest that the number and characteristics of the green lines are influenced by the annealing temperature as well as by the Yb/Tm concentration ratio, opening possibilities for new customized applications. The chromaticity properties of the upconversion spectra were quantified by the Commission Internationale de l'éclairage coordinate analysis.

  15. tmRDB (tmRNA database)

    PubMed Central

    Zwieb, Christian; Gorodkin, Jan; Knudsen, Bjarne; Burks, Jody; Wower, Jacek

    2003-01-01

    Maintained at the University of Texas Health Science Center at Tyler, Texas, the tmRNA database (tmRDB) is accessible at the URL http://psyche.uthct.edu/dbs/tmRDB/tmRDB.html with mirror sites located at Auburn University, Auburn, Alabama (http://www.ag.auburn.edu/mirror/tmRDB/) and the Bioinformatics Research Center, Aarhus, Denmark (http://www.bioinf.au.dk/tmRDB/). The tmRDB collects and distributes information relevant to the study of tmRNA. In trans-translation, this molecule combines properties of tRNA and mRNA and binds several proteins to form the tmRNP. Related RNPs are likely to be functional in all bacteria. In this release of tmRDB, 186 new entries from 10 bacterial groups for a total of 274 tmRNA sequences have been added. Lists of the tmRNAs and the corresponding tmRNA-encoded tag-peptides are presented in alphabetical and phylogenetic order. The tmRNA sequences are aligned manually, assisted by computational tools, to determine base pairs supported by comparative sequence analysis. The tmRNA alignment, available in a variety of formats, provides the basis for the secondary and tertiary structure of each tmRNA molecule. Three-dimensional models of the tmRNAs and their associated proteins in PDB format give evidence for the recent progress that has been made in the understanding of tmRNP structure and function. PMID:12520048

  16. Elastic anomalies of YbIrGe in magnetic fields

    NASA Astrophysics Data System (ADS)

    Suzuki, T.; Noguchi, Y.; Ishii, I.; Goto, H.; Kamikawa, S.; Fujita, T. K.; Katoh, K.

    2015-03-01

    The Yb-based heavy-fermion compound YbIrGe, which has the orthorhombic structure, shows the crystal electric field effect at high temperatures and antiferromagnetic orderings at TN = 2.4 K and Tm = 1.4 K. We previously found anomalous elastic softening in zero magnetic field originating from an indirect quadrupole interaction between the ground doublet and the excited doublets, and determined the crystal electric field level scheme: the ground doublet and an excited doublet at 138 K. To investigate the antiferromagnetic orderings at TN and Tm, we performed ultrasonic measurements under magnetic fields along the a-axis on YbIrGe single crystals. Temperature dependence of elastic modulus C11 exhibits elastic hardening below both TN and Tm at 0 T. As increasing the magnetic field along the a-axis, both TN and Tm decrease monotonically, suggesting that both transitions are antiferromagnetic ordering. TN closes around 2 T, and Tm disappears above 1 T. We clarified the magnetic field- temperature phase diagram along the a-axis.

  17. Triaxial strongly deformed bands in {sup 160,161}Tm

    SciTech Connect

    Teal, C.; Lagergren, K.; Aguilar, A.; Riley, M. A.; Hartley, D. J.; Simpson, J.; Joss, D. T.; Carpenter, M. P.; Janssens, R. V. F.; Lauritsen, T.; Lister, C. J.; Zhu, S.; Garg, U.; Kondev, F. G.; Wang, X.; Ragnarsson, I.

    2008-07-15

    High-spin states in {sup 160,161}Tm were populated using the {sup 128}Te({sup 37}Cl, 5n and 4n) reactions at a beam energy of 170 MeV. Emitted {gamma} rays were detected in the Gammasphere spectrometer. Two rotational bands with high moments of inertia were discovered, one assigned to {sup 160}Tm, while the other tentatively assigned to {sup 161}Tm. These sequences display features similar to bands observed in neighboring Er, Tm, Yb, and Lu nuclei which have been discussed in terms of triaxial strongly deformed structures. Cranked Nilsson Strutinsky calculations have been performed that predict well-deformed triaxial shapes at high spin in {sup 160,161}Tm.

  18. Resonant photo-ionization of Yb+ to Yb2+

    NASA Astrophysics Data System (ADS)

    Heugel, Simon; Fischer, Martin; Elman, Vladimir; Maiwald, Robert; Sondermann, Markus; Leuchs, Gerd

    2016-01-01

    We demonstrate the controlled creation of a {}174{{Yb}}2+ ion by photo-ionizing {}174{{Yb}}+ with weak continuous-wave lasers at ultraviolet wavelengths. The photo-ionization is performed by resonantly exciting transitions of the {}174{{Yb}}+ ion in three steps. Starting from an ion crystal of two laser-cooled {}174{{Yb}}+ ions localized in a radio-frequency trap, the verification of the ionization process is performed by characterizing the properties of the resulting mixed-species ion-crystal. The obtained results facilitate fundamental studies of physics involving {{Yb}}2+ ions.

  19. OncoLogicTM

    EPA Science Inventory

    OncoLogicTM - A Computer System to Evaluate the Carcinogenic Potential of Chemicals
    OncoLogicTM is a software program that evaluates the likelihood that a chemical may cause cancer. OncoLogicTM has been peer reviewed and is being rele...

  20. High Magnetic Transition Temperature and Semiconductor like Transport Properties of Mn-doped ?-YbAlB4

    NASA Astrophysics Data System (ADS)

    Suzuki, S.; Tomita, T.; Shimura, Y.; Kuga, K.; Matsumoto, Y.; Nakatsuji, S.

    2016-02-01

    We succeeded in growing single crystals of ?-YbAl1xMnxB4 by the substitution of Mn for the Al site in the intermediate-valence rare-earth heavy fermion system ?-YbAlB4. We performed specific heat and resistivity measurement on single crystals of ?-YbAl1xMnxB4 (x = 40). In the specific heat measurement on ?-YbAl0.60Mn0.40B4, a sharp peak was observed at magnetic transition temperature TM = 9.7(6) K. The resistivity measurements on x = 0.40 also show a semiconductor-like behavior in the entire temperature range from 2 - 300 K. An inclination change was also observed at 10(1) K in resistivity measurement. These results indicate a magnetic order. The magnetic transition temperature is quite high compared to its temperatures observed in the other Yb-based heavy fermion compounds.

  1. Ultraviolet upconversion luminescence of Gd{sup 3+} and Eu{sup 3+} in nano-structured glass ceramics

    SciTech Connect

    Lin, Hang; Chen, Daqin; Yu, Yunlong; Yang, Anping; Zhang, Rui; Wang, Yuansheng

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Ultraviolet upconversion emissions of Eu{sup 3+} and Gd{sup 3+} are rarely studied. Black-Right-Pointing-Pointer Nanostructured glass ceramic is developed as a host for ultraviolet upconversion. Black-Right-Pointing-Pointer Ultraviolet upconversion signal are found greatly enhanced after crystallization. Black-Right-Pointing-Pointer It is promising for fabricating novel ultraviolet upconversion lasers. -- Abstract: Ultraviolet multiphoton upconversion emissions of Eu{sup 3+} ({sup 5}H{sub 3-7}, {sup 5}G{sub 2-6}, {sup 5}L{sub 6} {yields} {sup 7}F{sub 0}) and Gd{sup 3+} ({sup 6}I{sub J}, {sup 6}P{sub J} {yields} {sup 8}S{sub 7/2}) are studied in the Eu{sup 3+} (or Gd{sup 3+}) doped SiO{sub 2}-Al{sub 2}O{sub 3}-NaF-YF{sub 3} precursor glasses and glass ceramics containing {beta}-YF{sub 3} nanocrystals, under continuous-wavelength 976 nm laser pumping. It is experimentally demonstrated that energy transfer from Yb{sup 3+} to Tm{sup 3+}, then further to Eu{sup 3+} or Gd{sup 3+} is responsible for the upconversion process. Compared to those in the precursor glasses, the upconversion emission intensities in the glass ceramics are greatly enhanced, owing to the participation of rare earth ions into the low-phonon-energy environment of {beta}-YF{sub 3} nanocrystals. Hopefully, the studied glass ceramics may find potential applications in the field of ultraviolet solid-state lasers.

  2. Continuous wave diode pumped Yb:LLF and Yb:NYF lasers

    NASA Astrophysics Data System (ADS)

    Yasukevich, A. S.; Kisel, V. E.; Kurilchik, S. V.; Grigoriev, S. V.; Kuleshov, N. V.; Gordeev, E. Yu.; Korableva, S. L.; Naumov, A. K.; Semashko, V. V.

    2009-11-01

    Experimental and theoretical results of investigation of CW Yb:LiLuF 4 (Yb:LLF) and Yb:Na 4Y 6F 22 (Yb:NYF) lasers under longitudinal diode laser pump are reported. Slope efficiencies of 41%, 58% with 0.21, 0.53 W of output powers were obtained for the Yb:LLF and Yb:NYF lasers, correspondingly. The Yb:NYF laser demonstrated tunability in the region from 1005 to 1061 nm. The mathematical modelling of CW laser operation predicts under optimized laser parameters optical to optical efficiencies of about 55% and 51% for Yb:LLF and Yb:NYF lasers, respectively.

  3. MOP03TM (HDF)

    Atmospheric Science Data Center

    2015-10-07

    ... MOP03TM MOPITT CO gridded monthly means (Thermal Infrared Radiances) News:  MOPITT Science Team ... CO (on a latitude/longitude/pressure grid) derived from Thermal Infrared Radiances, version 6, Hampton, VA, USA:NASA Atmospheric ...

  4. CLOMP_TM

    Energy Science and Technology Software Center (ESTSC)

    2012-06-01

    The CLOMP_TM benchmark was developed to measure the overheads of various mechanisms used to guarantee the generation of correct results in threaded code even when multiple threads might be accessing and/or updating the same memory location at the same time. This includes widely supported mechanisms like OpenMP Atomic and Open MP Critical as well as new mechanisms like Transactional Memory (TM) and Speculative Execution (SE) of threads. The CLOMP_TM benchmark is highly configurable to allowmore » a variety of problem sizes, atomic update region sizes, and potential race condition opportunities to be studied. A wide variety of checks are done on the results to verify the expected answer was actuallyl generated. Thus CLOMP_TM can be used both to measure the overhead for various mechanisms and to check the correctness of their implementation.« less

  5. CLOMP_TM

    SciTech Connect

    2012-06-01

    The CLOMP_TM benchmark was developed to measure the overheads of various mechanisms used to guarantee the generation of correct results in threaded code even when multiple threads might be accessing and/or updating the same memory location at the same time. This includes widely supported mechanisms like OpenMP Atomic and Open MP Critical as well as new mechanisms like Transactional Memory (TM) and Speculative Execution (SE) of threads. The CLOMP_TM benchmark is highly configurable to allow a variety of problem sizes, atomic update region sizes, and potential race condition opportunities to be studied. A wide variety of checks are done on the results to verify the expected answer was actuallyl generated. Thus CLOMP_TM can be used both to measure the overhead for various mechanisms and to check the correctness of their implementation.

  6. Phase and Size Controllable Synthesis of NaYbF4 Nanocrystals in Oleic Acid/ Ionic Liquid Two-Phase System for Targeted Fluorescent Imaging of Gastric Cancer

    PubMed Central

    Pan, Liyuan; He, Meng; Ma, Jiebing; Tang, Wei; Gao, Guo; He, Rong; Su, Haichuan; Cui, Daxiang

    2013-01-01

    Upconversion nanocrystals with small size and strong fluorescent signals own great potential in applications such as biomolecule-labeling, in vivo tracking and molecular imaging. Herein we reported that NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals with small size and strong fluorescent signals were controllably synthesized by oleic acid (OA)/ ionic liquid (IL) two-phase system for targeted fluorescent imaging of gastric cancer in vivo. The optimal synthesis condition of NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals by OA/IL two-phase system was established, adding more metal ion such as Na+ ion could facilitate the size control and crystal-phase transition, more importantly, markedly enhancing fluorescent intensity of beta-phase nanocrystals compared with traditional methods. Alpha-phase NaYbF4, 2%Tm upconversion nanocrystals with less than 10nm in diameter and beta-phase NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals with 30 nm or so in diameter and strong fluorescent signals were obtained, these synthesized nanocrystals exhibited very low cytotoxicity. Folic acid-conjugated silica-modified beta-phase NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals were prepared, could actively target gastric cancer tissues implanted into nude mice in vivo, and realized targeted fluorescent imaging. Folic acid-conjugated silica-modified NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals show great potential in applications such as targeted near infared radiation fluorescent imaging, magnetic resonance imaging and targeted therapy of gastric cancer in the near future. PMID:23471455

  7. A broadening temperature sensitivity range with a core-shell YbEr@YbNd double ratiometric optical nanothermometer

    NASA Astrophysics Data System (ADS)

    Marciniak, L.; Prorok, K.; Francés-Soriano, L.; Pérez-Prieto, J.; Bednarkiewicz, A.

    2016-02-01

    The chemical architecture of lanthanide doped core-shell up-converting nanoparticles can be engineered to purposely design the properties of luminescent nanomaterials, which are typically inaccessible to their homogeneous counterparts. Such an approach allowed to shift the up-conversion excitation wavelength from ~980 to the more relevant ~808 nm or enable Tb or Eu up-conversion emission, which was previously impossible to obtain or inefficient. Here, we address the issue of limited temperature sensitivity range of optical lanthanide based nano-thermometers. By covering Yb-Er co-doped core nanoparticles with the Yb-Nd co-doped shell, we have intentionally combined temperature dependent Er up-conversion together with temperature dependent Nd --> Yb energy transfer, and thus have expanded the temperature response range ΔT of a single nanoparticle based optical nano-thermometer under single ~808 nm wavelength photo-excitation from around ΔT = 150 K to over ΔT = 300 K (150-450 K). Such engineered nanocrystals are suitable for remote optical temperature measurements in technology and biotechnology at the sub-micron scale.The chemical architecture of lanthanide doped core-shell up-converting nanoparticles can be engineered to purposely design the properties of luminescent nanomaterials, which are typically inaccessible to their homogeneous counterparts. Such an approach allowed to shift the up-conversion excitation wavelength from ~980 to the more relevant ~808 nm or enable Tb or Eu up-conversion emission, which was previously impossible to obtain or inefficient. Here, we address the issue of limited temperature sensitivity range of optical lanthanide based nano-thermometers. By covering Yb-Er co-doped core nanoparticles with the Yb-Nd co-doped shell, we have intentionally combined temperature dependent Er up-conversion together with temperature dependent Nd --> Yb energy transfer, and thus have expanded the temperature response range ΔT of a single nanoparticle based optical nano-thermometer under single ~808 nm wavelength photo-excitation from around ΔT = 150 K to over ΔT = 300 K (150-450 K). Such engineered nanocrystals are suitable for remote optical temperature measurements in technology and biotechnology at the sub-micron scale. Electronic supplementary information (ESI) available: Characterization, structural and morphological characterization of nanocrystals, the measurement setup. See DOI: 10.1039/c5nr08223d

  8. Yb:S-FAP lasers

    NASA Astrophysics Data System (ADS)

    Schaffers, Kathleen I.

    2004-09-01

    It has recently been reported that several high power, diode-pumped laser systems have been developed based on crystals of Yb:S-FAP [Yb 3+:Sr 5(PO 4) 3F]. The mercury laser, at Lawrence Livermore National Laboratory, is the most prominent system using Yb:S-FAP and is currently producing 23 J at 5 Hz in a 15 nsec pulse, based on partial activation of the system. In addition, a regenerative amplifier is being developed at Waseda University in Japan and has produced greater than 12 mJ with high beam quality at 50 Hz repetition rate. Q-Peak has demonstrated 16 mJ of maximum energy/output pulse in a multi-pass, diode side-pumped amplifier and ELSA in France is implementing Yb:S-FAP in a 985 nm pump for an EDFA, producing 250 mW. Growth of high optical quality crystals of Yb:S-FAP is a challenge due to multiple crystalline defects. However, at this time, a growth process has been developed to produce high quality 3.5 cm diameter Yb:S-FAP crystals and a process is under development for producing 6.5 cm diameter crystals.

  9. High power ytterbium (Yb(3+))-doped fibre laser operating in the 1.12 micron region

    NASA Astrophysics Data System (ADS)

    Mackechnie, C. J.; Barnes, W. L.; Hanna, D. C.; Townsend, J. E.

    1993-01-01

    Results are presented for high power (greater than 0.5 W) Yb(3+) fiber lasers operating at a wavelength of around 1120 nm pumped either by Nd:YAG (1.064 micron) or Nd:YLF (1.047 micron) lasers. The use of this laser as a single-wavelength pump for a Tm(3+) ZBLAN upconversion fiber laser is also demonstrated.

  10. TM: Torus Mapper

    NASA Astrophysics Data System (ADS)

    Binney, James; McMillan, Paul J.

    2015-12-01

    TM (Torus Mapper) produces models for orbits in action-angle coordinates in axisymmetric potentials using torus mapping, a non-perturbative technique for creating orbital tori for specified values of the action integrals. It can compute a star's position at any time given an orbital torus and a star's position at a reference time, and also provides a way to choose initial conditions for N-body simulations of realistic disc galaxies that start in perfect equilibrium. TM provides some advantages over use of a standard time-stepper to create orbits.

  11. Structure and Properties of YbZnSn, YbAgSn, and Yb 2Pt 2Pb

    NASA Astrophysics Data System (ADS)

    Pttgen, Rainer; Arpe, Petra E.; Felser, Claudia; Kumann, Dirk; Mllmann, Ralf; Mosel, Bernd D.; Knnen, Bernd; Kotzyba, Gunter

    1999-07-01

    YbZnSn, YbAgSn, and Yb2Pt2Pb were synthesized by reacting the elements in sealed tantalum tubes in a high-frequency furnace. The structures of YbAgSn and Yb2Pt2Pb were refined from single crystal X-ray data: YbAgPb type, Poverline6m2, a=479.2(2) pm, c=1087.3(3) pm, wR2=0.050, BASF=0.34(8), 509 F2 values, 18 variables for YbAgSn and Er2Au2Sn type, a=776.0(1) pm, c=701.8(2) pm, wR2=0.072, 426 F2 values, 18 variables for Yb2Pt2Pb. The lattice constants of YbZnSn are confirmed: NdPtSb type, P63mc, a=464.7(1) pm, c=747.7(2) pm. The stannides YbZnSn and YbAgSn crystallize with superstructures of the AlB2 type. The zinc (silver) and tin atoms form ordered Zn3Sn3 and Ag3Sn3 hexagons, respectively. The stacking sequences for the differently oriented hexagons are AB, AB for YbZnSn and ABC, ABC for YbAgSn. While exclusively Zn-Sn intralayer interactions were observed in YbZnSn, intralayer Ag-Sn and significant Sn-Sn interlayer interactions at 318 pm occur in YbAgSn. The [ZnSn] and [AgSn] polyanions in YbZnSn and YbAgSn, respectively, have a pronounced two-dimensional character. This picture of chemical bonding in YbAgSn is confirmed by TB-LMTO-ASA band structure calculations. The partial densities-of-states and the valence charge densities are discussed. The magnetic (no long-range ordering, Yb2+) and the resistivity measurements (metallic behavior) are in excellent agreement with the electronic structure calculations. Yb2Pt2Pb crystallizes with the Er2Au2Sn structure, a ternary derivative of the Zr3Al2 type. This structure is composed of distorted AlB2 and CsCl related slabs of compositions YbPt2 and YbPb. Yb2Pt2Pb shows paramagnetic behavior (4.30.4 ?B/Yb) indicating trivalent ytterbium. Magnetic susceptibility measurements on YbZnSn and YbAgSn show Pauli paramagnetism with room temperature susceptibilities of 2.5(1)10-9 and 4.6(1)10-9 m3/mol. Electrical resistivity measurements indicate metallic conductivity with specific resistivities of 44040 ??cm (YbZnSn) and 49040 ??cm (YbAgSn) at 300 K. 119Sn Mssbauer spectra of YbZnSn show a single signal at room temperature with an isomer shift of ?=1.85(1) mm/s. YbAgSn shows two superimposed signals at 78 K: a singlet at ?=1.94(1) mm/s and a second signal at ?=1.99(1) mm/s subjected to quadrupole splitting of ?EQ=1.35(1) mm/s, in agreement with the two crystallographically different tin sites.

  12. Thermal expansion of a Au-Al-Yb intermediate valence quasicrystal

    NASA Astrophysics Data System (ADS)

    Watanuki, T.; Kashimoto, S.; Ishimasa, T.; Machida, A.; Yamamoto, S.; Tanaka, Y.; Mizumaki, M.; Kawamura, N.; Watanabe, S.

    2015-06-01

    The thermal expansion of a Au-Al-Yb intermediate-valence quasicrystal has been studied. X-ray diffraction measurements showed zero thermal expansion below 50 K. By comparison with an isostructural Au-Al-Tm quasicrystal, the contribution of the Yb valence variation was extracted, and it was shown that its negative thermal expansion component compensated for the positive thermal expansion of the original lattice. On cooling, the Yb contribution grew steeply below approximately 155 K down to the lowest experimental temperature of 5 K, due to enlargement of the Yb atomic radius, which was caused by the valence shift toward the divalent state. Additionally, a larger Yb contribution to the thermal expansion was demonstrated in a crystalline approximant to this quasicrystal. The magnitude of this contribution was approximately 1.4 times larger than in the case of the quasicrystal itself, resulting in a slight negative thermal expansion below 50 K. A heterogeneous valence model for the quasicrystal that we proposed previously accounts for this magnitude difference.

  13. A broadening temperature sensitivity range with a core-shell YbEr@YbNd double ratiometric optical nanothermometer.

    PubMed

    Marciniak, L; Prorok, K; Francés-Soriano, L; Pérez-Prieto, J; Bednarkiewicz, A

    2016-02-25

    The chemical architecture of lanthanide doped core-shell up-converting nanoparticles can be engineered to purposely design the properties of luminescent nanomaterials, which are typically inaccessible to their homogeneous counterparts. Such an approach allowed to shift the up-conversion excitation wavelength from ∼980 to the more relevant ∼808 nm or enable Tb or Eu up-conversion emission, which was previously impossible to obtain or inefficient. Here, we address the issue of limited temperature sensitivity range of optical lanthanide based nano-thermometers. By covering Yb-Er co-doped core nanoparticles with the Yb-Nd co-doped shell, we have intentionally combined temperature dependent Er up-conversion together with temperature dependent Nd → Yb energy transfer, and thus have expanded the temperature response range ΔT of a single nanoparticle based optical nano-thermometer under single ∼808 nm wavelength photo-excitation from around ΔT = 150 K to over ΔT = 300 K (150-450 K). Such engineered nanocrystals are suitable for remote optical temperature measurements in technology and biotechnology at the sub-micron scale. PMID:26865210

  14. GEOMAG[TM] Paradoxes

    ERIC Educational Resources Information Center

    Defrancesco, Silvia; Logiurato, Fabrizio; Karwasz, Grzegorz

    2007-01-01

    As often happens, a lot of physics can come out of a toy. What we found interesting is the observation of the magnetic field produced by different configurations built with GEOMAG[TM]. This toy provides small magnetic bars and steel spheres to play with. Amusing 3-D structures can be built; nevertheless, this possibility is not so obvious. Indeed,

  15. GEOMAG[TM] Paradoxes

    ERIC Educational Resources Information Center

    Defrancesco, Silvia; Logiurato, Fabrizio; Karwasz, Grzegorz

    2007-01-01

    As often happens, a lot of physics can come out of a toy. What we found interesting is the observation of the magnetic field produced by different configurations built with GEOMAG[TM]. This toy provides small magnetic bars and steel spheres to play with. Amusing 3-D structures can be built; nevertheless, this possibility is not so obvious. Indeed,…

  16. 1 W single-frequency Tm-doped ZBLAN fiber MOPA around 810 nm.

    PubMed

    Kohno, Kenta; Takeuchi, Yu-ichi; Kitamura, Toshiyuki; Nakagawa, Ken'ichi; Ueda, Ken-ichi; Musha, Mitsuru

    2014-04-01

    We demonstrate a tunable narrow-linewidth fiber MOPA system around 810 nm for the light source of the Sr optical lattice clock. The coherent cw light source with a wavelength of 813.42 nm was generated by a combination of a narrow linewidth external-cavity laser diode and a Tm-doped ZBLAN fiber amplifier, which was upconversion-pumped by an Yb-doped fiber laser at 1064 nm. The maximum output power of 1.1 W was obtained with the launched power of 17 W, which is the highest power obtained from a Tm-doped fiber amplifier ever reported. PMID:24686708

  17. Fabrication of Yb-123 Tapes

    SciTech Connect

    Athur, S.; Balachandran, U.; Salama, K.

    2000-11-15

    While Bi-2223 tapes have been the workhorses of the superconductor industry, their poor performance in applied magnetic fields restrict their use to below 30 K. Melt-processing of Ag-clad Yb-123 PIT tapes offers a simple and scalable technique for fabricating long-length HTS conductors capable of being used at 77 K. Under reduced oxygen partial pressure, the peritectic temperature of Yb-123 is below the melting point of Ag, and this facilitates the adaptation of melt-texturing methods for fabricating these tapes. The effect of melt-processing temperature on current density was also explored; a temperature of 965 C yielded optimal critical current values. The critical current density achieved at 4.2 K was 20,000 A/cm{sup 2}, corresponding to a critical current of 52 A. Based on the above results, an optimal processing zone for melt-processing of Ag-clad Yb-123 tapes was determined. These results hold promise for melt-processing of Ag-clad Yb-123 tapes as an alternative to Bi-2223 PIT technology.

  18. [Study on ultraviolet upconversion emissions of Gd3+ induced by Tm3+ under 980 nm excitation].

    PubMed

    Cao, Chun-Yan; Yu, Xiao-Guang; Qin, Wei-Ping; Zhang, Ji-Sen

    2010-03-01

    Series of Tm3+/Yb3+ co-doped GdF3 powders were synthesized through an easy and mild hydrothermal method. The phase and purity of powders were characterized by powder X-ray diffraction (XRD) (Rigaku RU-200b). The morphologies of the samples were characterized by field emission scanning electron microscopy (FE SEM) (Hitachi S-4800). The ultraviolet (UV) up-conversion (UC)emission spectra were recorded by a fluorescence spectrophotometer (Hitachi F-4500) with a 980 nm semiconductor continuous wave laser diode as the excitation source. And the luminescent dynamics was measured by excitation with 980 nm using an optical parameter oscillator (OPO) laser pumped by a pulsed Nd : YAG laser with a pulse duration of 10 ns, repetition frequency of 10 Hz, and the signal was recorded by using a monochromator and an oscillograph. Under 980 nm excitation, Gd3+, acting as a kind of host ion in the studied system, and its UV UC emissions were observed and studied. The luminescent dynamics of the characteristic emission of Gd3+ (311.6 nm, 6P7/2 --> 8S7/2) was explored and studied. The luminescent dynamics analysis results indicated that, on UV UC emissions of Gd3+, Yb3+ ions served as primary sensitizer ions successively transferring energy to Tm3+ to populate the 3P2 level. Then, Tm3+ ions served as secondary sensitizer ions transferring energy to populate the multiple 6 I(J) states of Gd3+ 3P2 --> 3H6 (Tm3+): 8S7/2 --> 6 I(J) (Gd3+). Further, 6D(J) levels were populated through other energy transfer processes between Gd3+ and Yb3+ or Tm3+. Finally, UV UC emissions from the excited 6D9/2, 6 I(J), 6P5/2, and 6P7/2 states to the ground state 8S7/2 were observed. Meanwhile, Tm3+ acted as activator in its own UC emissions, and the article did not put emphasis on those except the 3P2 and 1 I6 levels to the ground state 3 H6 transitions. Especially, the dependences of UV UC emissions of Gd3+ on the Yb3+ concentrations, the Tm3+ concentrations, the annealing temperatures, and the excitation power densities of the 980 nm semiconductor continuous wave laser diode were studied, too. PMID:20496672

  19. Phase and size controllable synthesis of NaYbF4 nanocrystals in oleic acid/ionic liquid two-phase system for targeted fluorescent imaging of gastric cancer.

    PubMed

    Pan, Liyuan; He, Meng; Ma, Jiebing; Tang, Wei; Gao, Guo; He, Rong; Su, Haichuan; Cui, Daxiang

    2013-01-01

    Upconversion nanocrystals with small size and strong fluorescent signals own great potential in applications such as biomolecule-labeling, in vivo tracking and molecular imaging. Herein we reported that NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals with small size and strong fluorescent signals were controllably synthesized by oleic acid (OA)/ ionic liquid (IL) two-phase system for targeted fluorescent imaging of gastric cancer in vivo. The optimal synthesis condition of NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals by OA/IL two-phase system was established, adding more metal ion such as Na(+) ion could facilitate the size control and crystal-phase transition, more importantly, markedly enhancing fluorescent intensity of beta-phase nanocrystals compared with traditional methods. Alpha-phase NaYbF4, 2%Tm upconversion nanocrystals with less than 10nm in diameter and beta-phase NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals with 30 nm or so in diameter and strong fluorescent signals were obtained, these synthesized nanocrystals exhibited very low cytotoxicity. Folic acid-conjugated silica-modified beta-phase NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals were prepared, could actively target gastric cancer tissues implanted into nude mice in vivo, and realized targeted fluorescent imaging. Folic acid-conjugated silica-modified NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals show great potential in applications such as targeted near infared radiation fluorescent imaging, magnetic resonance imaging and targeted therapy of gastric cancer in the near future. PMID:23471455

  20. Structure and properties of RELiGe2 (RE = La-Nd, Sm-Gd, Yb) compounds

    NASA Astrophysics Data System (ADS)

    Iyer, Abishek K.; Subbarao, Udumula; Peter, Sebastian C.

    2013-02-01

    Single phase samples of RELiGe2 (RE = La-Nd, Sm-Gd, Yb) were synthesized in niobium tubes by high-frequency (HF) heating method. RELiGe2 compounds crystallize in the CaLiSi2 type structure, space group Pnma. LaLiGe2 is diamagnetic, while PrLiGe2, NdLiGe2, EuLiGe2, GdLiGe2 and YbLiGe2 follow Curie-Weiss behavior above 50 K. All compounds are metallic conductors with a specific resistivity at room temperature within the range of 250-900 ??cm.

  1. Effects of Yb concentration on the spectroscopic properties of Yb: Y3Al5O12.

    PubMed

    Wang, Xiaodan; Xu, Xiaodong; Zeng, Xionghui; Zhao, Zhiwei; Jiang, Benxue; He, Xiaoming; Xu, Jun

    2006-01-01

    Yb:YAG single crystals with Yb doping concentration 5.4, 16.3, 27.1, 53.6, and 100 at.% were grown by the Czochralski process. The effects of Yb concentration on the absorption spectra (190-1100 nm), fluorescence spectra under 940 nm and X-ray excitation were studied. The concentration quenching of fluorescence was observed when the Yb doping concentration reaches to as high as 27.1at.% for Yb:YAG. Under 940 nm excitation, the influence of the self-absorption at 969 and 1029 nm on the fluorescence spectra is not evident when the Yb doping concentration is as high as 27.1at.%. However, it can greatly change the shape of fluorescence spectra of Yb:YAG when the Yb doping concentration reaches to above 53.6 at.%. PMID:16344242

  2. YB48 the metal rich boundary of YB66; crystal growth and thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Hossain, M. Anwar; Tanaka, Isao; Tanaka, Takaho; Khan, A. Ullah; Mori, Takao

    2015-12-01

    It was discovered that the well-known higher boride YB66, one of the first reported phonon glass electron crystals (PGEC), could be obtained in a much more metal-rich composition than previously thought possible. Using the floating zone growth method, YB48 single crystals with YB66 crystal structure could be obtained, and their thermoelectric properties measured. This expansion of the homogeneity range of the well-known YB66 compound is surprising and a new Y atomic site was discovered. YB48 exhibits much higher power factors than YB66 which increase rapidly with increasing temperature. The obtained dimensionless figure of merit of this compound at 990 K is approximately 30 times higher than that of previously reported YB66 samples, and higher than any other pristine higher boride. This discovery reveals YB48 as a promising high temperature thermoelectric material.

  3. Mode instability thresholds for Tm-doped fiber amplifiers pumped at 790 nm.

    PubMed

    Smith, Arlee V; Smith, Jesse J

    2016-01-25

    We use a detailed numerical model of stimulated thermal Rayleigh scattering to compute mode instability thresholds in Tm3+-doped fiber amplifiers. The fiber amplifies 2040 nm light using a 790 nm pump. The cross-relaxation process is strong, permitting power efficiencies of 60%. The predicted instability thresholds are compared with those in similar Yb3+-doped fiber amplifiers with 976 nm pump and 1060 nm signal, and are found to be higher, even though the heat load is much higher in Tm-doped amplifiers. The higher threshold in the Tm-doped fiber is attributed to its longer signal wavelength, and to stronger gain saturation, due in part to cross-relaxation heating. PMID:26832480

  4. Thermoluminescence responses of the Yb- and Yb-Tb-doped SiO2 optical fibers to 6-MV photons.

    PubMed

    Sahini, M H; Hossain, I; Wagiran, H; Saeed, M A; Ali, H

    2014-09-01

    Characteristics of the thermoluminescence (TL) responses of Yb- and Yb-Tb-doped optical fibers irradiated with 6MV photons are reported. The concentration of Yb in the Yb-doped optical fiber was 0.26mol%; the concentrations of Yb and Tb in the Yb-Tb-doped optical fiber were 0.62 and 0.2mol%, respectively. The TL dose responses are linear in the dose range 0.5-4Gy. The radiation sensitivity of the Yb-Tb material is almost two orders of magnitude higher than the sensitivity of the material doped with Yb alone. PMID:24973463

  5. 75 FR 5068 - Lock + TM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-01

    ... Energy Regulatory Commission Lock + \\TM\\ Hydro Friends Fund XXXIII, LLC; Notice of Preliminary Permit... January 22, 2010. On January 8, 2010, Lock + \\TM\\ Hydro Friends Fund XXXIII, LLC (Lock + Hydro) filed an... the Green Lantern Project No. 13651, to be located on the Mississippi River, in Pike County,...

  6. 75 FR 5071 - Lock + TM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-01

    ... Energy Regulatory Commission Lock + \\TM\\ Hydro Friends Fund XXXI, LLC; Notice of Preliminary Permit... January 22, 2010. On January 8, 2010, Lock + \\TM\\ Hydro Friends Fund XXXI, LLC (Lock + Hydro) filed an... the Kermit Project No. 13649, to be located on the Mississippi River, in Adams County, Illinois,...

  7. The tmRNA website

    SciTech Connect

    Hudson, C. M.; Williams, K. P.

    2014-11-05

    The transfer-messenger RNA (tmRNA) and its partner protein SmpB act together in resolving problems arising when translating bacterial ribosomes reach the end of mRNA with no stop codon. Their genes have been found in nearly all bacterial genomes and in some organelles. The tmRNA Website serves tmRNA sequences, alignments and feature annotations, and has recently moved to http: //bioinformatics.sandia.gov/tmrna/. New features include software used to find the sequences, an update raising the number of unique tmRNA sequences from 492 to 1716, and a database of SmpB sequences which are served along with the tmRNA sequence from the same organism.

  8. Probing dual mode emission of Eu3+ in garnet phosphor

    NASA Astrophysics Data System (ADS)

    Singh, S. K.; Gi Lee, Dong; Soo Yi, Soung; Jang, Kiwan; Shin, Dong-Soo; Hyun Jeong, Jung

    2013-05-01

    Eu3+ doped and Eu3+, Yb3+ co-doped Gd3Ga5O12 phosphors have been developed by facile solid state reaction method which can be easily scaled-up in large quantity. The synthesis has been optimized to get a single phase material at 1300 C. The phase and crystal parameters have been analyzed by using X-ray diffraction measurement. Photoluminescence excitation (monitored for the 5D0 ? 7F1 transition of Eu3+) depicts that the active ion (Eu3+) can be excited through direct excitation into 4f band of Eu3+, through charge transfer band (Eu3+-O2-) excitation and also through the excitation into 8S7/2 ? 6IJ intra f-f transition of Gd3+ ion, which significantly all together cover a broad excitation region in 200-420 nm. In addition, in the presence of Yb3+ ions, the emission is also achieved by near infrared excitation (976 nm), through a typical upconversion (UC) process. Thus, the material efficiently behaves as a dual mode emitting phosphor (emission is achieved both through normal fluorescence and through UC process). The conversion efficiency of silicon solar cells is only 15% of terrestrial solar energy for 200-400 nm region and also the sub-band gap energy (in infrared region) is lost as heat; therefore, this kind of dual mode phosphors may be used to overcome the above mentioned incomplete utilization of the solar spectrum and can open realm of new possibilities for energy harvesting.

  9. Thermoelectric properties of the Zintl phases Yb5M2Sb6 (M = Al, Ga, In).

    PubMed

    Aydemir, Umut; Zevalkink, Alex; Ormeci, Alim; Wang, Heng; Ohno, Saneyuki; Bux, Sabah; Snyder, G Jeffrey

    2015-04-21

    Zintl compounds with chemical formula Yb5M2Sb6 (M = Al, Ga, and In) form one of two known A5M2Pn6 structure types characterized by double chains of corner-linked MPn4 tetrahedra bridged by Pn2 dumbbells. High temperature electronic and thermal transport measurements were used to characterize the thermoelectric properties of Yb5M2Sb6 compounds. All samples were found to exhibit similar high p-type carrier concentrations, low resistivity and low Seebeck coefficients in agreement with the band structure calculations. These results, combined with previous studies, suggest that Yb5M2Sb6 compounds are semimetals (i.e., they lack an energy gap between the valence and conduction bands), in contrast to the semiconducting alkaline earth (Ca, Sr, Ba) and Eu based A5M2Sb6 compounds. Yb5M2Sb6 compounds have very low lattice thermal conductivity, comparable to other closely related A5M2Sb6 and A3MSb3 phases. However, due to the semimetallic behaviour, the figure of merit of investigated samples remains low (zT < 0.15). PMID:25670617

  10. Definition of an intramolecular Eu-to-Eu energy transfer within a discrete [Eu2L] complex in solution.

    PubMed

    Nonat, Aline; Regueiro-Figueroa, Martín; Esteban-Gómez, David; de Blas, Andrés; Rodríguez-Blas, Teresa; Platas-Iglesias, Carlos; Charbonnière, Loïc J

    2012-06-25

    Ligand L, based on two do3a moieties linked by the methylene groups of 6,6'-dimethyl-2,2'-bipyridine, was synthesized and characterized. The addition of Ln salts to an aqueous solution of L (0.01 M Tris-HCl, pH 7.4) led to the successive formation of [LnL] and [Ln(2)L] complexes, as evidenced by UV/Vis and fluorescence titration experiments. Homodinuclear [Ln(2)L] complexes (Ln = Eu, Gd, Tb, Yb, and Lu) were prepared and characterized. The (1)H and (13)C NMR spectra of the Lu and Yb complexes in D(2)O solution (pD = 7.0) showed C(1) symmetry of these species in solution, pointing to two different chemical environments for the two lanthanide cations. The analysis of the chemical shifts of the Yb complex indicated that the two coordination sites present square antiprismatic (SAP) coordination environments around the metal ions. The spectroscopic properties of the [Tb(2)L] complex upon ligand excitation revealed conventional behavior with τ(H2O) = 2.05(1) ms and ϕ(H2O) = 51%, except for the calculation of the hydration number obtained from the luminescent lifetimes in H(2)O and D(2)O, which pointed to a non-integer value of 0.6 water molecules per Tb(III) ion. In contrast, the Eu complex revealed surprising features such as: 1) the presence of two and up to five components in the (5)D(0)→(7)F(0) and (5)D(0)→(7)F(1) emission bands, respectively; 2) marked differences between the normalized spectra obtained in H(2)O and D(2)O solutions; and 3) unconventional temporal evolution of the luminescence intensity at certain wavelengths, the intensity profile first displaying a rising step before the occurrence of the expected decay. Additional spectroscopic experiments performed on [Gd(2-x)Eu(x)L] complexes (x = 0.1 and 1.9) confirmed the presence of two distinct Eu sites with hydration numbers of 0 (site I) and 2 (site II), and showed that the unconventional temporal evolution of the emission intensity is the result of an unprecedented intramolecular Eu-to-Eu energy-transfer process. A mathematical model was developed to interpret the experimental data, leading to energy-transfer rates of 0.98 ms(-1) for the transfer from the site with q=0 to that with q=2 and vice versa. Hartree-Fock (HF) and density functional theory (DFT) calculations performed at the B3LYP level were used to investigate the conformation of the complex in solution, and to estimate the intermetallic distance, which provided Förster radii (R(0)) values of 8.1 Å for the energy transfer from site I to site II, and 6.8 Å for the reverse energy transfer. These results represent the first evidence of an intramolecular energy-transfer equilibrium between two identical lanthanide cations within a discrete molecular complex in solution. PMID:22614945

  11. Optical waveguides in Yb:SBN crystals fabricated by swift C3+ ion irradiation

    NASA Astrophysics Data System (ADS)

    Liu, Guiyuan; Dong, Ningning; Wang, Jun; Akhmadaliev, Shavkat; Zhou, Shengqiang; Chen, Feng

    2016-01-01

    We report on the fabrication of optical planar waveguides supporting both the TE and TM confinements in Yb:SBN crystal by swift C3+ ions irradiation. A combination of the micro-photoluminescence and micro-Raman investigations have evidenced the presence of lattice distortion, damage and disordering of the SBN network along the ion irradiation path, with these effects being at the basis of the refractive index modification. The enhanced micro-photoluminescence and micro-Raman intensity in the waveguide volumes show the potential application of the obtained waveguides as active laser gain media.

  12. Phase equilibrium and intermediate phases in the Eu-Sb system

    SciTech Connect

    Abdusalyamova, M.N.

    2011-10-15

    Rapid heating rate thermal analysis, X-ray diffraction, fluorescence spectrometry, and differential dissolution method were used to study the high-temperature phase equilibrium in the Eu-Sb system within the composition range between 37 and 96 at% Sb. The techniques were effective in determination of the vapor-solid-liquid equilibrium since intermediate phases except Eu{sub 4}Sb{sub 3} evaporated incongruently after melting. A thermal procedure was developed to determine the liquidus and solidus lines of the T-x diagram. Six stable phases were identified: two phases, EuSb{sub 2} and Eu{sub 4}Sb{sub 3}, melt congruently at 1045{+-}10 deg. C and 1600{+-}15 deg. C, the Eu{sub 2}Sb{sub 3}, Eu{sub 11}Sb{sub 10}, Eu{sub 5}Sb{sub 4}, and Eu{sub 5}Sb{sub 3} phases melt incongruently at 850{+-}8 deg. C, 950{+-}10 deg. C, 1350{+-}15 deg. C, and 1445{+-}15 deg. C, respectively. The exact composition shifting of Sb-rich decomposable phases towards Eu{sub 4}Sb{sub 3}, the most refractory compound, was determined. The topology of the Eu-Sb phase diagram was considered together with that of the Yb-Sb system. - Graphical abstract: The high-temperature range of the T-x phase diagram for the Eu-Sb system. Highlights: > The phase relations in the Eu-Sb system were studied over a large composition and temperature scale. > The liquidus and solidus lines of the T-x diagram were well established using effective techniques. > In the system, six binary phases are stable and they melt incongruently except EuSb{sub 2} and Eu{sub 4}Sb{sub 3}. > Incongruent evaporation was found to be typical of all the phases besides Eu{sub 4}Sb{sub 3}.

  13. Localized Electron Magnetism in the Icosahedral Au-Al-Tm Quasicrystal and Crystalline Approximant

    NASA Astrophysics Data System (ADS)

    Nakayama, Mika; Tanaka, Katsumasa; Matsukawa, Shuya; Deguchi, Kazuhiko; Imura, Keiichiro; Ishimasa, Tsutomu; Sato, Noriaki K.

    2015-02-01

    We report the magnetic, thermal, and transport properties of the Au-Al-Tm quasicrystal, which is isostructural to the first and only quasicrystal Au-Al-Yb that shows a novel quantum critical behavior. The Tm-based quasicrystal undergoes a spin-glass-like freezing below Tf 0.4 K. We also synthesize the Au-Al-Tm approximant to the quasicrystal and find that it shows a similar spin-glass-like freezing below Tf 0.3 K. Both the quasicrystal and the approximant follow the Curie-Weiss law in a wide temperature range above Tf, indicating that the 4f electrons are well localized on the vertices of the icosahedron. The interspin interaction is antiferromagnetic and its magnitude is as small as 1 K. The spin-glass-like freezing is presumably driven by the combined effect of the chemical disorder of Au/Al ions and the frustrated nature of the icosahedron. On the basis of these results, we discuss a possible origin of the unusual quantum criticality observed in the Yb-based system.

  14. Growth of YbF 3-doped CaF 2 crystals and characterization of Yb 3+/Yb 2+ conversion

    NASA Astrophysics Data System (ADS)

    Nicoara, Irina; Stef, Marius; Pruna, Andreea

    2008-04-01

    Calcium fluoride crystals doped with YbF 3 and PbF 2-, NaF- and LiF-codoped were grown using the vertical Bridgman method. Transparent, high quality, with various high Yb 2+ contents in the as-grown crystals has been obtained using a special procedure. The optical absorption spectra reveal the characteristic ultraviolet (UV) absorption bands of the divalent Yb ions. Influence of the codoping with Pb 2+, Li + and Na + ions on the absorption spectra and on the Yb 2+ ions content has been studied. High-intensity emission bands in the near-UV spectral region, not reported before, have been observed for excitation by 230 nm. A comparison of our results with those obtained by other authors is also given.

  15. Anomalies in the Young modulus at structural phase transitions in rare-earth cobaltites RBaCo{sub 4}O{sub 7} (R = Y, Tm-Lu)

    SciTech Connect

    Kazei, Z. A. Snegirev, V. V.; Andreenko, A. S.; Kozeeva, L. P.

    2011-08-15

    The elastic properties of rare-earth cobaltites RBaCo{sub 4}O{sub 7} (R = Y, Tm-Lu) have been experimentally studied in the temperature range of 80-300 K. The strong softening of the Young modulus {Delta}E(T)/E{sub 0} Almost-Equal-To -(0.1-0.2) of cobaltites with Lu and Yb ions has been revealed, which is due to the instability of the crystal structure upon cooling and is accompanied by an inverse jump at the second-order structural phase transition. The softening of the Young modulus and the jump at the phase transition decrease by an order of magnitude and the transition temperature T{sub s} and hysteresis {Delta}T{sub s} increase from a compound with Lu to that with Tm. A large softening of the Young modulus at the structural transition in Lu- and Yb cobaltites indicates that the corresponding elastic constant goes to zero, whereas this constant in Tm cobaltite is not a 'soft' mode of the phase transition. It has been found that the structural phase transition in Lu- and Yb cobaltites is accompanied by a large absorption maximum at the phase transition point and an additional maximum in the low-temperature phase and absorption anomalies in Tm cobaltite is an order of magnitude smaller.

  16. Monodisperse lanthanide oxyfluorides LnOF (Ln = Y, La, Pr-Tm): morphology controlled synthesis, up-conversion luminescence and in vitro cell imaging

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Li, Xuejiao; Hou, Zhiyao; Lin, Jun

    2014-05-01

    Lanthanide oxyfluorides LnOF (Ln = Y, La, Pr-Tm) nano/micro-materials with a variety of well-defined morphologies including nanorods, nanospindles, nanorod-bundles and nanospheres, have been successfully synthesized via a facile precipitation technique followed by a heating treatment. It is found that the pH values, fluoride sources and dosage of urea in the initial reaction systems play critical roles in the morphology determination of the LnOF products and the possible formation mechanism for these diverse architectures has been presented. XRD, FT-IR, TG-DTA, SEM, TEM, as well as up-conversion (UC) luminescence spectra are used to characterize the synthesized samples. Under 980 nm NIR laser excitation, red, green and blue UC luminescence are observed from Yb3+/Er3+, Yb3+/Ho3+ and Yb3+/Tm3+ co-doped YOF nanospheres. The MTT assay indicates that YOF nanospheres exhibit good biocompatibility. Especially, the emission spectrum of YOF: 0.20Yb3+, 0.04Er3+ nanospheres is dominated by a single red emission at 660 nm, which falls into the ``optical window'' of biological tissues. The application of YOF: 0.20Yb3+, 0.04Er3+ nanospheres in the cell imaging is also investigated, which shows a bright-red emission without background noise.Lanthanide oxyfluorides LnOF (Ln = Y, La, Pr-Tm) nano/micro-materials with a variety of well-defined morphologies including nanorods, nanospindles, nanorod-bundles and nanospheres, have been successfully synthesized via a facile precipitation technique followed by a heating treatment. It is found that the pH values, fluoride sources and dosage of urea in the initial reaction systems play critical roles in the morphology determination of the LnOF products and the possible formation mechanism for these diverse architectures has been presented. XRD, FT-IR, TG-DTA, SEM, TEM, as well as up-conversion (UC) luminescence spectra are used to characterize the synthesized samples. Under 980 nm NIR laser excitation, red, green and blue UC luminescence are observed from Yb3+/Er3+, Yb3+/Ho3+ and Yb3+/Tm3+ co-doped YOF nanospheres. The MTT assay indicates that YOF nanospheres exhibit good biocompatibility. Especially, the emission spectrum of YOF: 0.20Yb3+, 0.04Er3+ nanospheres is dominated by a single red emission at 660 nm, which falls into the ``optical window'' of biological tissues. The application of YOF: 0.20Yb3+, 0.04Er3+ nanospheres in the cell imaging is also investigated, which shows a bright-red emission without background noise. Electronic supplementary information (ESI) available: The XRD patterns of GdOF, ErOF, Tm(OF)1.93 and YOF obtained after calcinations at 800 C for 3 h and the corresponding standard data of GdOF, ErOF, Tm(OF)1.93 and YOF. The accurate amounts of Ln3+ and F- for LaOF, GdOF, ErOF and YOF: 0.20Yb3+, 0.04Er3+, respectively. SEM images of the ErOF precursor under different experimental conditions (a) pH = 2, urea/Ln3+ = 66, with LiF; (b) pH = 2, urea/Ln3+ = 66, with KF; (c) pH = 6, urea/Ln3+ = 66, with NaF; (d) pH = 10, urea/Ln3+ = 66, with NaF; (e) pH = 2, urea/Ln3+ = 80, with NaF and (f) pH = 2, urea/Ln3+ = 100, with NaF. See DOI: 10.1039/c4nr00384e

  17. Near infrared activation of an anticancer Pt(IV) complex by Tm-doped upconversion nanoparticles.

    PubMed

    Ruggiero, Emmanuel; Hernndez-Gil, Javier; Mareque-Rivas, Juan C; Salassa, Luca

    2015-02-01

    The Pt(IV) complex cis,cis,trans-[Pt(NH3)2(Cl)2(O2CCH2CH2CO2H)2] is photoactivated by near infrared light (980 nm) using NaYF4:Yb(3+)/Tm(3+)@NaYF4 core-shell upconversion nanoparticles. Coupling of this cisplatin precursor with the biocompatible PEGylated phospholipid DSPE-PEG(2000)-NH2 affords a valuable approach to decorate the surface of the nanoparticles, providing novel photoactivatable nanomaterials capable of releasing Pt(II) species upon NIR light excitation. PMID:25536114

  18. Band structure calculations of heavy fermion YbSbPd and YbSbNi

    NASA Astrophysics Data System (ADS)

    Solanki, A. K.; Kashyap, Arti; Auluck, S.; Brooks, M. S. S.

    1994-05-01

    Dhar et al. [J. Phys. F 18, L41 (1988); and Proceedings of the International Conference on Strongly Correlated Electron Systems Sendai, Japan, 1992 (Plenum, New York, 1987)] have recently measured the low-temperature specific heat of YbSbPd and YbSbNi. Their measurements yield large values for the specific heat coefficient (1384 states/Ry cell for YbSbPd and 865 states/Ry cell for YbSbNi), and suggest a magnetic transition at low temperature. With a view to understand the ground state of these compounds, we have performed self-consistent scalar relativistic linear muffin-tin orbital band structure calculations. Our paramagnetic calculations for YbSbPd and YbSbNi give the density of the states at Fermi level to be 82.94 and 27.96 states/Ry cell, respectively. These give enhancement factors of 16.7 and 30.1 for YbSbPd and YbSbNi. We present results of our calculations of the band structure as well as the Stoner I parameter for these compounds.

  19. Lattice dynamics in the thermoelectric Zintl compound Yb[subscript 14]MnSb[subscript 11

    SciTech Connect

    Mchel, A.; Sergueev, I.; Wille, H.-C.; Juranyi, F.; Schober, H.; Schweika, W.; Brown, S.R.; Kauzlarich, S.M.; Hermann, R.P.

    2012-04-02

    The density of phonon states in the thermoelectric material Yb{sub 14}MnSb{sub 11} has been studied first by inelastic neutron scattering and second in an element-specific way by nuclear inelastic x-ray scattering. The low sound velocity of 1880(50) m/s as obtained from the density of phonon states can be identified as an important reason for the low heat transport in this system. The high melting temperature of Yb{sub 14}MnSb{sub 11} contrasts with the low energy of all phonons (<25 meV) and relates to an unusual lack of softening of phonon modes with temperature, when comparing the phonon density of states observed at ambient temperatures and at 1200 K. We have also measured the density of phonon states of the related Eu{sub 14}MnSb{sub 11} compound and of the thermoelectric Zintl phase Zn{sub 4}Sb{sub 3} in order to compare with related thermodynamic properties of Yb{sub 14}MnSb{sub 11} and to elucidate the different mechanisms of the heat conductivity reduction in Zintl phases.

  20. Listening and Legos[TM

    ERIC Educational Resources Information Center

    Morris, Pamela

    2012-01-01

    This simple exercise, performed in teams, gives students practice in listening to instructions, particularly when there are restrictions for the communication. The teams compete in a limited amount of time to build a Lego[TM] structure based on the instructions of one team member. Which team listens the best and is most successful?

  1. Resonantly pumped amplification in a Tm-doped large mode-area photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Sincore, Alex; Shah, Lawrence; Wysmolek, Mateusz; Ryan, Robert; Abdulfattah, Ali; Richardson, Martin

    2015-03-01

    Ultra-large mode area thulium-doped photonic crystal fibers (Tm:PCF) have enabled the highest peak powers in 2 micron fiber laser systems to date. However, Tm:PCFs are limited by slope efficiencies of <50% when pumped with 790 nm laser diodes. A well-known alternative is pumping at 1550 nm with erbium/ytterbium-doped fiber (Er/Yb:fiber) lasers for efficiencies approaching ~70%. However, these 1550 nm pump lasers are also relatively inefficient themselves. A recently demonstrated and more attractive approach to enable slope efficiencies over 90% in thuliumdoped step-index fibers is resonant pumping (or in-band pumping). This utilizes a high power thulium fiber laser operating at a shorter wavelength as the pump. In this manuscript, we describe an initial demonstration of resonant pumping in Tm:PCF. While the extracted power was still in the exponential regime due to pump power limitations, slope efficiencies in excess of ~64 have been observed, and there is still room for improvement. These initial results show promise for applying resonant pumping in Tm:PCF to improve efficiencies and facilitate high power scaling in ultralarge mode area systems.

  2. Semiconducting properties of Tm doped Yb-ZnO films by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Chaki, Imane; Belayachi, Azzam; El Bahraoui, Toufik; Regragui, Mohamed; Abd-Lefdil, Mohamed

    2014-12-01

    In this work, we have investigated the structural, optical and electrical properties of rare earth co-doped zinc oxide thin films prepared by spray pyrolysis technique. X-ray diffraction has shown that the films are polycrystalline and textured with the c-axis of the wurtzite structure along the growth direction. Scanning electronic microscopy and transmission electronic microscopy were used to study the films composition and morphology. Photoluminescence measurements showed that all the films have a strong emission band at around 380 nm. Layers with electrical resistivity values as low as 5.7 × 10-2 Ω cm were obtained.

  3. Eu 3F 4S 2: Synthesis, crystal structure, and magnetic properties of the mixed-valent europium(II,III) fluoride sulfide EuF 2(EuFS) 2

    NASA Astrophysics Data System (ADS)

    Grossholz, Hagen; Hartenbach, Ingo; Kotzyba, Gunter; Pttgen, Rainer; Trill, Henning; Mosel, Bernd D.; Schleid, Thomas

    2009-11-01

    Using the method to synthesize rare-earth metal(III) fluoride sulfides MFS ( M=Y, La, Ce-Lu), in some cases we were able to obtain mixed-valent compounds such as Yb 3F 4S 2 instead. With Eu 3F 4S 2 another isotypic representative has now been synthesized. Eu 3F 4S 2 (tetragonal, I4 /mmm, a=400.34(2), c=1928.17(9) pm, Z=2) is obtained from the reaction of metallic europium, elemental sulfur, and europium trifluoride in a molar ratio of 5:6:4 within seven days at 850 C in silica-jacketed gas-tightly sealed platinum ampoules. The single-phase product consists of black plate-shaped single crystals with a square cross section, which can be obtained from a flux using equimolar amounts of NaCl as fluxing agent. The crystal structure is best described as an intergrowth structure, in which one layer of CaF 2-type EuF 2 is followed by two layers of PbFCl-type EuFS when sheeted parallel to the (001) plane. Accordingly there are two chemically and crystallographically different europium cations present. One of them (Eu 2+) is coordinated by eight fluoride anions in a cubic fashion, the other one (Eu 3+) exhibits a monocapped square antiprismatic coordination sphere with four F - and five S 2- anions. Although the structural ordering of the different charged europium cations is plausible, a certain amount of charge delocalization with some polaron activity has to take place, which is suggested by the black color of the title compound. Temperature dependent magnetic susceptibility measurements of Eu 3F 4S 2 show Curie-Weiss behavior with an experimental magnetic moment of 8.19(5) ? B per formula unit and a paramagnetic Curie temperature of 0.3(2) K. No magnetic ordering is observed down to 4.2 K. In accordance with an ionic formula splitting like (Eu II)(Eu III) 2F 4S 2 only one third of the europium centers in Eu 3F 4S 2 carry permanent magnetic moments. 151Eu-Mssbauer spectroscopic experiments at 4.2 K show one signal at an isomer shift of -12.4(1) mm/s and a second one at 0.42(4) mm/s. These signals occur in a ratio of 1:2 and correspond to Eu 2+ and Eu 3+, respectively. The spectra at 78 and 298 K are similar, thus no change in the Eu 2+/Eu 3+ fraction can be detected.

  4. 75 FR 2129 - Lock+TM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-14

    ... Energy Regulatory Commission Lock+ TM Hydro Friends Fund XXX, LLC; Notice of Preliminary Permit... January 6, 2010. On November 13, 2009, Lock+ TM Hydro Friends Fund XXX, LLC filed an application, pursuant...,018 megawatt-hours. Applicant Contact: Wayne F. Krouse, Lock+ TM Hydro Friends Fund XXX, LLC,...

  5. Intermetallic germanides with non-centrosymmetric structures derived from the Yb3Rh4Sn13 type.

    PubMed

    Gumeniuk, R; Schneich, M; Kvashnina, K O; Akselrud, L; Tsirlin, A A; Nicklas, M; Schnelle, W; Janson, O; Zheng, Q; Curfs, C; Burkhardt, U; Schwarz, U; Leithe-Jasper, A

    2015-03-28

    New germanides with composition RE3Pt4Ge13 (RE = Y, Pr, Sm, Gd, Tb, Tm) have been prepared by high-pressure, high-temperature synthesis. Their crystal structures have been refined, and the relationship of this new rhombohedral and monoclinic structure types with the primitive cubic Yb3Rh4Sn13 prototype is discussed. Band structure calculations within density functional theory confirm the distorted rhombohedral and monoclinic structural arrangements to be energetically more favorable than the simple cubic one. X-ray absorption spectroscopy and magnetic susceptibility measurements indicate that the RE-atoms are in the +3 oxidation state in all studied compounds. PMID:25705863

  6. Evidence from Tm anomalies for non-CI refractory lithophile element proportions in terrestrial planets and achondrites

    NASA Astrophysics Data System (ADS)

    Barrat, J. A.; Dauphas, N.; Gillet, P.; Bollinger, C.; Etoubleau, J.; Bischoff, A.; Yamaguchi, A.

    2016-03-01

    Thulium is a heavy rare earth element (REE) whose geochemical behavior is intermediate between Er and Yb, and that is not expected to be decoupled from these elements during accretion of planetary bodies and geological processes. However, irregularities in REE volatilities at higher temperature could have decoupled the REEs relative to one another during the early stages of condensation of the solar nebula. Indeed, positive Tm anomalies are found in some refractory inclusions from carbonaceous chondrites, and it is possible that large scale nebular reservoirs displaying positive or negative Tm anomalies were formed during the early history of the solar system. We analyzed a series of meteorites and terrestrial rocks in order to evaluate the existence of Tm anomalies in planetary materials. Relative to CIs (Ivuna-type carbonaceous chondrites), carbonaceous chondrites display unresolved or positive Tm anomalies, while most of the noncarbonaceous chondrites show slightly negative Tm anomalies. Quantification of these anomalies in terrestrial samples is complicated when samples display fractionated heavy REE patterns. Taking this effect into account, we show that the Earth, Mars, Vesta, the aubrite and ureilite parent bodies display small negative anomalies (Tm/Tm∗ ≈ 0.975), very similar to those found in ordinary and enstatite chondrites. We suggest that a slight negative Tm anomaly relative to CI is a widespread feature of the materials from the inner solar system. This finding suggests that CI chondrites may not be appropriate for normalizing REE abundances of most planetary materials as they may be enriched in a high-temperature refractory component with non-solar composition. The presence of Tm anomalies at a bulk planetary scale is, to this day, the strongest piece of evidence that refractory lithophile elements are not present in constant CI proportions in planetary bodies.

  7. An Yb-Raman cascaded fiber laser with temporal stability

    NASA Astrophysics Data System (ADS)

    Wenliang, Wang; Jinyong, Leng; Yang, Gao; Shaofeng, Guo; Zongfu, Jiang

    2015-07-01

    We report a new structure of fiber laser, which has the advantages of temporal stability and wavelength agility. An Yb-Raman cascaded fiber oscillator generating 168 mW 1137 nm stable CW signal with 18.2% slope efficiency is demonstrated. In this fiber oscillator, the gain from both Yb ion and SRS effect is utilized. By comparison, the characteristics of the 1137 nm Yb-doped fiber laser are studied. The results show that the serious self-pulsation effect in the Yb-doped fiber laser is suppressed in the Yb-Raman cascaded fiber oscillator.

  8. Synthesis and Thermoelectric Properties of the YbTe-YbSb System

    NASA Astrophysics Data System (ADS)

    Kawamura, Airi; Hu, Yufei; Kauzlarich, Susan M.

    2016-01-01

    The syntheses of YbTe1- x Sb x ( x = 0, 0.05, 0.2, 0.5, 0.8, 1) were investigated by solid state reactions and formed into dense pellets by spark plasma sintering. X-ray powder diffraction and microprobe analysis indicated no solubility of Sb in YbTe, and these phases are better described as composite phases (YbTe)1- x (YbSb) x ( x = 0, 0.05, 0.2, 0.5, 0.8, 1). Thermal conductivity, electrical resistivity, and Seebeck coefficients were acquired for the larger values of x ( x = 0.2, 0.5, 0.8, 1) from room temperature to 773 K, and the figure of merit was calculated. Thermal conductivities for x = 0, 0.05 are also reported; however, measurements of Seebeck coefficients and electrical resistivity were not possible due to large resistivity. The figure of merit for all samples was low, and the maximum zT measured was zT 791K = 0.018 for YbSb. Low figures of merit were primarily the result of very high resistivity in YbTe rich samples, and high thermal conductivity, and a small Seebeck coefficient in all samples.

  9. Stability, structural, and electronic properties of atomic chains on Yb/Ge(111)32 studied by STM and STS

    NASA Astrophysics Data System (ADS)

    Kuzmin, M.; Laukkanen, P.; Perl, R. E.; Punkkinen, M. P. J.; Ahola-Tuomi, M.; Lng, J.; Vyrynen, I. J.

    2010-04-01

    By means of scanning tunneling microscopy and spectroscopy (STM/STS), we have investigated the stability and the structure of atomic chains on Yb/Ge(111)32 . STM allows the identification of different building blocks of this reconstruction, depending on the bias polarity and voltage, and validates the honeycomb chain-channel (HCC) structure with the Ge?Ge double bond and metal coverage of 1/6 ML for Yb/Ge(111)32 , in agreement with the recent photoemission study [Kuzmin , Phys. Rev. B 75, 165305 (2007)]. The Yb atoms are found to be adsorbed on similar sites in the well-defined 2 rows. Locally, such rows are distorted, leading to the 4 periodicity, where the Yb atoms are adsorbed on two different sites that are well consistent with T4 and H3 sites. It is also assumed that Yb atoms can fluctuate rapidly between the neighboring T4 and H3 sites, leading to continuous rows observed together with the 2 rows in STM images. The stability of Ge honeycomb chain is controlled by the presence of Yb atom per two (31) surface units in average, which results in the donation of one electron from Yb to the surface per (31) unit. When this density is locally changed, the Ge honeycomb chain is found to be broken. The inner structure of the Ge honeycomb chain is visualized in STM and shows dimerized features without any apparent buckling. The STM observations also account for why the double periodicity is missing in the low-energy electron diffraction pattern from Yb/Ge(111)32 . The local electronic structure of this reconstruction, namely the Yb rows and Ge honeycomb chains, is studied by STS. The results support the HCC structure with the Ge?Ge double bond. It is believed that the present study elucidates the difference between the (32) reconstructions of Yb and Eu on Ge(111) and those of alkaline-earth and rare-earth metals on Si(111).

  10. Rare earth-copper-magnesium compounds RECu{sub 9}Mg{sub 2} (RE=Y, La-Nd, Sm-Ho, Yb) with ordered CeNi{sub 3}-type structure

    SciTech Connect

    Solokha, P. . E-mail: solokha_pavlo@yahoo.com; Pavlyuk, V.; De Negri, S.; Prochwicz, W.

    2006-10-15

    A series of ternary compounds RECu{sub 9}Mg{sub 2} (RE=Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Yb) have been synthesized via induction melting of elemental metal ingots followed by annealing at 400 deg. C for 4 weeks. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDXS) was used for examining microstructure and phase composition. These phases crystallize with an ordered version of the binary hexagonal structure type first reported for CeNi{sub 3}. The crystal structure was solved for TbCu{sub 9}Mg{sub 2} from single crystal X-ray counter data (TbCu{sub 9}Mg{sub 2}-structure type, P6{sub 3} /mmc-space group, hP24-Pearson symbol, a=0.49886 (7) nm, c=1.61646 (3) nm, R {sub F}=0.0474 for 190 unique reflections). The Rietveld refinement of the X-ray powder diffraction patterns of RECu{sub 9}Mg{sub 2} confirmed the same crystal structure for the reported rare earth metals. The unit cell volumes for RECu{sub 9}Mg{sub 2} smoothly follow the lanthanide contraction. The existence of a RECu{sub 9}Mg{sub 2} phase was excluded for RE=Er Tm under the investigated experimental conditions. - Graphical abstract: The perspective view of the arrangement of the icosahedrons and anti-cubooctahedrons in the structure of TbCu{sub 9}Mg{sub 2}.

  11. Tunability of Yb:glass laser

    NASA Astrophysics Data System (ADS)

    ulc, Jan; Krivosudsk, Ondrej; Jelnkov, Helena; Stepien, Ryszard

    2013-03-01

    Ytterbium doped phosphate glass (5 mol% of Yb2O3, thickness 1 and 2 mm, uncoated), developed for fibre laser, was tested in bulk form as a laser active medium. For Yb:glass pumping a fibre coupled (fibre core diameter 100 ?m, NA = 0.22) laser diode with emission at wavelength 975nm was used. The laser diode was operating in pulsed regime (pulse length 1.5 ms, repetition rate 5 Hz, maximum pulse energy 22 mJ) with low duty cycle to reduce a heat accumulation inside the active medium (Yb:glass was only air-cooled). Longitudinally pumped Yb:glass samples were placed inside the 145mm long semi-hemispherical resonator formed by a flat pumping mirror (HR @ 1.0 - 1.1 ?m, HT @ 0.97 ?m) and by curved output coupler (r = 150 mm). Set of output couplers with reflectivity 91 - 97% @ 1.0 - 1.1 ?m was used. Tuning of the Yb:glass laser was accomplished by using a birefringent filter (single 1.5mm thick quartz plate) placed inside the optical resonator at the Brewster angle between the output coupler (reflectivity 97%) and laser active medium. In untuned regime the energy up to 2.4mJ was obtained at wavelength 1050 nm. Slope efficiency up to 17% in respect to absorbed pumping was reached with the 2mm sample. In tuned regime the smooth laser tuning curve, limited by used Lyot filter, extended from 1005nm up to 1080nm (FWHM 48 nm). The maximum output energy of 1.65mJ was obtained at 1060nm for the absorbed energy 16 mJ.

  12. [YB-1 as a potential target in cancer therapy].

    PubMed

    Lage, H; Surowiak, P; Holm, P S

    2008-11-01

    The 42-kDa multifunctional cellular protein Y-box protein 1 (YB-1) is expressed in various cancers. It is localized in the cytoplasm as well as in the nucleus. In particular, YB-1 is localized in the nuclear compartment following cellular stress, such as radiation, drug treatment, hyperthermia, or viral infection. Within the nucleus, YB-1 can act as a transcription factor, and it is involved in the regulation of important cancer-associated genes. For example, YB-1 triggers the expression of Her-2 and estrogen receptor alpha (ERalpha) in breast cancer. Thus, nuclear YB-1 appears to be a potential target for the inhibition of Her-2- and ERalpha-dependent proliferation signals, particularly with regard to resistance to Her-2-targeting drugs such as trastuzumab. In some cancers, YB-1 may be involved in regulating MDR1/P-glycoprotein, mediating classical multidrug resistance (MDR). Furthermore, YB-1 is involved in the replication of adenovirus type 5, a commonly used vector in gene therapy. Thus, YB-1 can trigger an "oncolytic" effect in YB-1 nuclear positive cancer cells treated with adenoviruses. Besides its impact as a prognostic factor, in the future the diagnostics of cellular YB-1 status may provide the basis for a virotherapy or a gene therapy incorporating adenoviruses. PMID:18773210

  13. Influence of rare earth cation size on the crystal structure in rare earth silicates, Na2RESiO4(OH) (RE = Sc, Yb) and NaRESiO4 (RE = La, Yb)

    NASA Astrophysics Data System (ADS)

    Latshaw, Allison M.; Wilkins, Branford O.; Chance, W. Michael; Smith, Mark D.; zur Loye, Hans-Conrad

    2016-01-01

    Crystals of Na2ScSiO4(OH) and Na2YbSiO4(OH) were synthesized at low temperatures using a sodium hydroxide based hydroflux, while crystals of NaLaSiO4 and NaYbSiO4 were grown at high temperatures using a sodium fluoride/sodium chloride eutectic flux. Both structure types were crystallized under reaction conditions that, when used for medium sized rare earths (RE = Pr, Nd, Sm - Tm) yield the Na5RE4X[SiO4]4 structure type, where X is OH in the hydroflux conditions and F in the eutectic flux conditions. Herein, we report the synthesis, structure, size effect, and magnetic properties of these compositions and introduce the new structure type of Na2RESiO4(OH), which crystallizes in the orthorhombic space group Pca21, of NaLaSiO4, which crystallizes in the orthorhombic space group Pna21, and of NaYbSiO4, which crystallizes in the orthorhombic space group Pnma, where both NaRESiO4 compounds have one silicon structural analog.

  14. The tmRNA ribosome rescue system

    PubMed Central

    Janssen, Brian D.; Hayes, Christopher S.

    2012-01-01

    The bacterial tmRNA quality control system monitors protein synthesis and recycles stalled translation complexes in a process termed ribosome rescue. During rescue, tmRNA acts first as a transfer RNA to bind stalled ribosomes, then as a messenger RNA to add the ssrA peptide tag to the C-terminus of the nascent polypeptide chain. The ssrA peptide targets tagged peptides for proteolysis, ensuring rapid degradation of potentially deleterious truncated polypeptides. Ribosome rescue also facilitates turnover of the damaged messages responsible for translational arrest. Thus, tmRNA increases the fidelity of gene expression by promoting the synthesis of full-length proteins. In addition to serving as a global quality control system, tmRNA also plays important roles in bacterial development, pathogenesis and environmental stress responses. This review focuses on the mechanism of tmRNA-mediated ribosome rescue and the role of tmRNA in bacterial physiology. PMID:22243584

  15. Magnetic properties of EuLn{sub 2}O{sub 4} (Ln=rare earths)

    SciTech Connect

    Hirose, Keiichi; Doi, Yoshihiro; Hinatsu, Yukio

    2009-07-15

    Ternary rare earth oxides EuLn{sub 2}O{sub 4} (Ln=Gd, Dy-Lu) were prepared. They crystallized in an orthorhombic CaFe{sub 2}O{sub 4}-type structure with space group Pnma. {sup 151}Eu Moessbauer spectroscopic measurements show that the Eu ions are in the divalent state. All these compounds show an antiferromagnetic transition at 4.2-6.3 K. From the positive Weiss constant and the saturation of magnetization for EuLu{sub 2}O{sub 4}, it is considered that ferromagnetic chains of Eu{sup 2+} are aligned along the b-axis of the orthorhombic unit cell, with neighboring Eu{sup 2+} chains antiparallel. When Ln=Gd-Tm, ferromagnetically aligned Eu{sup 2+} ions interact with the Ln{sup 3+} ions, which would overcome the magnetic frustration of triangularly aligned Ln{sup 3+} ions and the EuLn{sub 2}O{sub 4} compounds show a simple antiferromagnetic behavior. - Graphical abstract: Ternary rare earth oxides EuLn{sub 2}O{sub 4} (Ln=Gd, Dy-Lu) crystallized in an orthorhombic CaFe{sub 2}O{sub 4}-type structure with space group Pnma. Moessbauer spectroscopic measurements show that the Eu ions are in the divalent state. All these compounds show an antiferromagnetic transition at 4.2-6.3 K. It is considered that ferromagnetic chains of Eu{sup 2+} are aligned along the b-axis of the orthorhombic unit cell, with neighboring Eu{sup 2+} chains antiparallel.

  16. Dysfunction of Rice Mitochondrial Membrane Induced by Yb3+.

    PubMed

    Gao, Jia-Ling; Wu, Man; Liu, Wen; Feng, Zhi-Jiang; Zhang, Ye-Zhong; Jiang, Feng-Lei; Liu, Yi; Dai, Jie

    2015-12-01

    Ytterbium (Yb), a widely used rare earth element, is treated as highly toxic to human being and adverseness to plant. Mitochondria play a significant role in plant growth and development, and are proposed as a potential target for ytterbium toxicity. In this paper, the biological effect of Yb(3+) on isolated rice mitochondria was investigated. We found that Yb(3+) with high concentrations (200 ~ 600 ?M) not only induced mitochondrial membrane permeability transition (mtMPT), but also disturbed the mitochondrial ultrastructure. Moreover, Yb(3+) caused the respiratory chain damage, ROS formation, membrane potential decrease, and mitochondrial complex II activity reverse. The results above suggested that Yb(3+) with high concentrations could induce mitochondrial membrane dysfunction. These findings will support some valuable information to the safe application of Yb-based agents. PMID:26305923

  17. Harmonic mode-locking in a Tm-doped fiber laser: Characterization of its timing jitter and ultralong starting dynamics

    NASA Astrophysics Data System (ADS)

    Bao, Chengying; Yang, Changxi

    2015-12-01

    We report an experimental characterization on harmonic mode-locking in a Tm-doped fiber laser, which exhibits pump related timing jitter and ultralong mode-locking starting dynamics. The laser is pumped by a laser diode seeded EDFA. Harmonic mode-locking is initiated by nonlinear polarization rotation and showed a good long term stability. Timing jitter is found to be significantly influenced by the properties of laser diode seed for the EDFA. When switching the seed from a Fabry-Perot cavity laser diode to a distributed feedback (DFB) laser diode, timing jitter decreases from 16 ps to 6 ps. It also takes the laser an ultralong self-starting time (> 100 s), 3 order of magnitude longer than typical Er-doped or Yb-doped fiber lasers, to reach a steady harmonic mode-locking in some cases. These experimental evidences can contribute to a better understanding of Tm-doped fiber lasers.

  18. Diode-pumped regenerative Yb:SrF2 amplifier

    NASA Astrophysics Data System (ADS)

    Ricaud, S.; Georges, P.; Camy, P.; Doualan, J.-L.; Moncorgé, R.; Courjaud, A.; Mottay, E.; Druon, F.

    2012-03-01

    We report what we believe to be the first Yb:SrF2 regenerative femtosecond amplifier. The regenerative amplifier produces 325-fs pulses at 100-Hz repetition rate with an energy before compression of 1.4 mJ. The interest of Yb:SrF2 in such regenerative amplifiers and its complementarity to its well-known isotype Yb:CaF2 is also discussed.

  19. Microwave-assisted hydrothermal synthesis and temperature sensing application of Er3+/Yb3+ doped NaY(WO4)2 microstructures.

    PubMed

    Zheng, Hui; Chen, Baojiu; Yu, Hongquan; Zhang, Jinsu; Sun, Jiashi; Li, Xiangping; Sun, Min; Tian, Bining; Fu, Shaobo; Zhong, Hua; Dong, Bin; Hua, Ruinian; Xia, Haiping

    2014-04-15

    Laurustinus shaped NaY(WO4)2 micro-particles assembled by nanosheets were synthesized via a microwave-assisted hydrothermal (MH) route. The growing mechanisms for the obtained resultants with various morphologies were proposed based on the observation of scanning electron microscopic (SEM) images. It was found that Na3Cit added into the reaction solution greatly influenced the formation and size dimension of the nano-sheets, furthermore determined assembling of the laurustinus shaped micro-particles. The temperature sensing performance of NaY(WO4)2:Er(3+)/Yb(3+) was evaluated. Thermal effect induced by the 980nm laser irradiation in laurustinus-shaped NaY(WO4)2:Er(3+)/Yb(3+) phosphor was studied. It was found that the green upconversion luminescence intensity increased in the first stage of laser irradiation, and then decreased after reaching a maximum. Based on the thermal sensing technology the laurustinus NaY(WO4)2:Er(3+)/Yb(3+) microparticles were used as thermal probe to discover thermal effect of upconversion luminescence in laurustinus NaY(WO4)2:Tm(3+)/Yb(3+) micro-particles. PMID:24559696

  20. Cryogenic Yb:YAG thin-disk laser

    NASA Astrophysics Data System (ADS)

    Vretenar, N.; Carson, T.; Lucas, T.; Newell, T.; Latham, W. P.; Peterson, P.; Bostanci, H.; Lindauer, J. J.; Saarloos, B. A.; Rini, D. P.

    2011-11-01

    At cryogenic temperatures, Yb:YAG behaves as a 4-level laser. Its absorption and emission cross-sections increase, and its thermal conductivity improves. Yb:YAG thin disk laser performance at room and cryogenic (80K) temperatures will be presented. The Yb:YAG gain media is cooled using either a pressurized R134A refrigerant system or by a two-phase liquid nitrogen spray boiler. Interchangeable mounting caps allow the same Yb:YAG media to be switched between the two systems. This allows direct comparison of lasing, amplified spontaneous emission, and temperature performance between 20C and -200C.

  1. Crystal growth and properties of Yb:FAP laser crystal

    NASA Astrophysics Data System (ADS)

    Song, Pingxin; Zhao, Zhiwei; Xu, Xiaodong; Deng, Peizhen; Xu, Jun

    2005-04-01

    A large and transparent Yb:FAP crystal with dimensions up to ?30 mm85 mm has been grown by the Czochralski method. The preparation of the raw material has been investigated. X-ray power diffraction studies of Yb:FAP crystal confirm that the as-grown crystal is isostructural with the FAP crystal. The crystalline quality has been studied using X-ray rocking curve analysis. The segregation coefficient of Yb 3+ in the Yb:FAP crystal has been also determined. Linear thermal expansion coefficients in [0 0 1] and [1 0 0] directions have been measured in the 30-800 C temperature range.

  2. Power scaling of cryogenic Yb:LiYF(4) lasers.

    PubMed

    Zapata, Luis E; Ripin, Daniel J; Fan, Tso Yee

    2010-06-01

    We demonstrate a cryogenically cooled Yb:LiYF(4) (Yb:YLF) laser with 224W linearly polarized output power (pump-power limited) and a slope efficiency of 68%. The beam quality is characterized by an M(2) approximately 1.1 at 60W output and M(2) approximately 2.6 at 180W output. This level of average laser power is approximately 2 orders of magnitude higher than demonstrated previously in cryogenic Yb:YLF. Yb:YLF is attractive for femtosecond pulse generation because of its wide gain bandwidth, and this demonstration shows the potential for high-average-power subpicosecond pulse lasers. PMID:20517440

  3. Scaling of Yb-Fiber Frequency Combs

    NASA Astrophysics Data System (ADS)

    Ruehl, Axel; Marcinkevicius, Andrius; Fermann, Martin E.; Hartl, Ingmar

    2010-06-01

    Immediately after their introduction in 1999, femtosecond laser frequency combs revolutionized the field of precision optical frequency metrology and are key elements in many experiments. Frequency combs based on femtosecond Er-fiber lasers based were demonstrated in 2005, allowing additionally rugged, compact set-ups and reliable unattended long-term operation. The introduction of Yb-fiber technology led to an dramatic improvement in fiber-comb performance in various aspects. Low-noise Yb-fiber femtosecond oscillators enabled a reduction of relative comb tooth linewidth to the sub-Hz level as well as scaling of the fundamental comb spacings up to 1 GHz. This is beneficial for any frequency-domain comb application due to the higher power per comb-mode. Many spectroscopic applications require, however, frequency combs way beyond the wavelength range accessible with broad band laser materials, so nonlinear conversion and hence higher peak intensity is required. We demonstrated power scaling of Yb-fiber frequency combs up to 80 W average power in a strictly linear chirped-pulse amplification schemes compatible with low-noise phase control. These high-power Yb-fiber-frequency combs facilitated not only the extension to the mid-IR spectral region. When coupled to a passive enhancement cavity, the average power can be further scaled to the kW-level opening new capabilities for XUV frequency combs via high-harmonic generation. All these advances of fiber-based frequency combs will trigger many novel applications both in fundamental and applied sciences. Schibli et al., Nature Photonics 2 355 (2008). Hartl et al., MF9 in Advanced Solid-State Photonics. 2009, Optical Society of America. Ruehl et al., AWC7 in Advanced Solid-State Photonics. 2010, Optical Society of America. Adler et al., Optics Letters 34 1330 (2009). Yost et al., Nature Physics 5 815 (2009).

  4. Monodisperse and core-shell structured SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln=Eu, Tb, Dy, Sm, Er, Ho, and Tm) spherical particles: A facile synthesis and luminescent properties

    SciTech Connect

    Xu, Zhenhe; Feng, Bin; Bian, Shasha; Liu, Tao; Wang, Mingli; Gao, Yu; Sun, Di; Gao, Xin; Sun, Yaguang

    2012-12-15

    The core-shell structured SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+} particles were realized by coating the Lu{sub 2}O{sub 3}:Ln{sup 3+} phosphors onto the surface of non-aggregated, monodisperse and spherical SiO{sub 2} particles by the Pechini sol-gel method. The as-synthesized products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray (EDX) spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photolumiminescence (PL), and low-voltage cathodoluminescence (CL). The results indicate that the 800 Degree-Sign C annealed sample consists of crystalline Lu{sub 2}O{sub 3} shells and amorphous SiO{sub 2} cores, in spherical shape with a narrow size distribution. The as-obtained particles show strong light emission with different colors corresponding to different Ln{sup 3+} ions under ultraviolet-visible light excitation and low-voltage electron beams excitation, which have potential applications in fluorescent lamps and field emission displays. - Graphical Abstract: Representative SEM and TEM images of the core-shell structured SiO{sub 2}-Lu{sub 2}O{sub 3}:Eu{sup 3+} particles; CIE chromaticity diagram showing the emission colors for SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+}; Multicolor emissions of SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+} particles. Highlights: Black-Right-Pointing-Pointer The core-shell particles were realized by coating the phosphors onto the surface of SiO{sub 2} particles. Black-Right-Pointing-Pointer The sample consists of crystalline Lu{sub 2}O{sub 3} shells and amorphous SiO{sub 2} cores. Black-Right-Pointing-Pointer The particles show different light emission colors corresponding to Ln{sup 3+} ions. Black-Right-Pointing-Pointer They have potential applications in fluorescent lamps and field emission displays.

  5. 78 FR 72922 - TSA Pre✓TM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-04

    ...The Transportation Security Administration (TSA) announces the establishment of a fee for applicants of the TSA Pre[check]TM Application Program. Members of the public may apply to this TSA program by voluntarily providing biometric and biographic information and paying a fee. TSA will use these fees from applicants to fund selected activities of the TSA Pre[check]TM......

  6. A Review of "Integrity[TM]"

    ERIC Educational Resources Information Center

    Veldkamp, Bernard P.

    2008-01-01

    Integrity[TM], an online application for testing both the statistical integrity of the test and the academic integrity of the examinees, was evaluated for this review. Program features and the program output are described. An overview of the statistics in Integrity[TM] is provided, and the application is illustrated with a small simulation study.

  7. Anisotropic magnetization and transport properties of RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm)

    SciTech Connect

    Myers, Kenneth D.

    1999-11-08

    This study of the RAgSb{sub 2} series of compounds arose as part of an investigation of rare earth intermetallic compounds containing antimony with the rare earth in a position with tetragonal point symmetry. Materials with the rare earth in a position with tetragonal point symmetry frequently manifest strong anisotropies and rich complexity in the magnetic properties, and yet are simple enough to analyze. Antimony containing intermetallic compounds commonly possess low carrier densities and have only recently been the subject of study. Large single grain crystals were grown of the RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm) series of compounds out of a high temperature solution. This method of crystal growth, commonly known as flux growth is a versatile method which takes advantage of the decreasing solubility of the target compound with decreasing temperature. Overall, the results of the crystal growth were impressive with the synthesis of single crystals of LaAgSb{sub 2} approaching one gram. However, the sample yield diminishes as the rare earth elements become smaller and heavier. Consequently, no crystals could be grown with R=Yb or Lu. Furthermore, EuAgSb{sub 2} could not be synthesized, likely due to the divalency of the Eu ion. For most of the RAgSb{sub 2} compounds, strong magnetic anisotropies are created by the crystal electric field splitting of the Hund's rule ground state. This splitting confines the local moments to lie in the basal plane (easy plane) for the majority of the members of the series. Exceptions to this include ErAgSb{sub 2} and TmAgSb{sub 2}, which have moments along the c-axis (easy axis) and CeAgSb{sub 2}, which at intermediate temperatures has an easy plane, but exchange coupling at low temperatures is anisotropic with an easy axis. Additional anisotropy is also observed within the basal plane of DyAgSb{sub 2}, where the moments are restricted to align along one of the {l_angle}110{r_angle} axes. Most of the RAgSb{sub 2} compounds containing magnetic rare earths, antiferromagnetically ordered at low temperatures. The ordering temperatures of these compounds are approximately proportional to the de Gennes factor, which suggests that the RKKY interaction is the dominant exchange interaction between local moments. Although metamagnetic transitions were observed in many members of the series, the series of sharp step-like transitions in DyAgSb{sub 2} are impressive. In this compound, up to 11 different magnetic states are stable depending on the magnitude and direction of the applied field. The saturated magnetization of these states and the critical fields needed to induce a phase transition vary with the direction of the applied field. Through detailed study of the angular dependence of the magnetization and critical fields, the net distribution of magnetic moments was determined for most, of the metamagnetic states. In DyAgSb{sub 2}, the crystal electric field (CEF) splitting of the Hund's rule ground state creates a strong anisotropy where the local Dy{sup 3+} magnetic moments are constrained to one of the equivalent {l_angle}110{r_angle} directions within the basal plane. The four position clock model was introduced to account for this rich metamagnetic system. Within this model, the magnetic moments are constrained to one of four equivalent orientations within the basal plane and interactions are calculated for up third nearest neighbors. The theoretical phase diagram, generated from the coupling constants is in excellent agreement with the experimental phase diagram. Further investigation of this compound using magnetic X-ray or neutron diffraction would be extremely useful to verify the net distributions of moments and determine the wave vectors of each of the ordered states.

  8. Constitutive and functional expression of YB-1 in microglial cells.

    PubMed

    Keilhoff, G; Titze, M; Esser, T; Langnaese, K; Ebmeyer, U

    2015-08-20

    Y-box-binding protein (YB-1) is a member of the cold-shock protein family and participates in a wide variety of DNA/RNA-dependent cellular processes including DNA repair, transcription, mRNA splicing, packaging, and translation. At the cellular level, YB-1 is involved in cell proliferation and differentiation, stress responses, and malignant cell transformation. A general role for YB-1 during inflammation has also been well described; however, there are minimal data concerning YB-1 expression in microglia, which are the immune cells of the brain. Therefore, we studied the expression of YB-1 in a clinically relevant global ischemia model for neurological injury following cardiac arrest. This model is characterized by massive neurodegeneration of the hippocampal CA1 region and the subsequent long-lasting activation of microglia. In addition, we studied YB-1 expression in BV-2 cells, which are an accepted microglia culture model. BV-2 cells were stressed by oxygen/glucose deprivation (OGD), OGD-relevant mediators, lipopolysaccharide (LPS), and phagocytosis-inducing cell debris and nanoparticles. Using quantitative polymerase chain reaction (PCR), we show constitutive expression of YB-1 transcripts in unstressed BV-2 cells. The functional upregulation of the YB-1 protein was demonstrated in microglia in vivo and in BV-2 cells in vitro. All stressors except for LPS were potent enhancers of the level of YB-1 protein, which appears to be regulated primarily by proteasomal degradation and, to a lesser extent, by the activation (phosphorylation) of the translation initiation factor eIF4E. The proteasome of BV-2 cells is impaired by OGD, which results in decreased protein degradation and therefore increased levels of YB-1 protein. LPS induces proteasome activity, which enables the level of YB-1 protein to remain at control levels despite enhanced protein ubiquitination. The proteasome inhibitor MG-132 was able to increase YB-1 protein levels in control and LPS-treated cultures. YB-1 upregulation was not accompanied by its translocation from the cytoplasm to the nucleus. YB-1 induction appeared to be related to microglial proliferation because it was partially co-regulated with Ki67. In addition, YB-1 protein levels correlated with microglia phagocytic activity because its upregulation could also be induced by inert NPs. PMID:26102006

  9. Yb 3Cu 6Sn 5, Yb 5Cu 11Sn 8 and Yb 3Cu 8Sn 4: crystal structure of three ordered compounds

    NASA Astrophysics Data System (ADS)

    Fornasini, M. L.; Manfrinetti, P.; Mazzone, D.; Riani, P.; Zanicchi, G.

    2004-06-01

    Yb 3Cu 6Sn 5, Yb 5Cu 11Sn 8 and Yb 3Cu 8Sn 4 compounds were prepared in sealed Ta crucibles by induction melting and subsequent annealing. The crystal structures of Yb 3Cu 6Sn 5 and Yb 5Cu 11Sn 8 were determined from single crystal diffractometer data: Yb 3Cu 6Sn 5, isotypic with Dy 3Co 6Sn 5, orthorhombic, Immm, oI28, a=4.365(1) , b=9.834(3) , c=12.827(3) , Z=2, R=0.019, 490 independent reflections, 28 parameters; Yb 5Cu 11Sn 8 with its own structure, orthorhombic, Pmmn, oP48, a=4.4267(6) , b=22.657(8) , c=9.321(4) , Z=2, R=0.047, 1553 independent reflections, 78 parameters. Both compounds belong to the BaAl 4-derived defective structures, and are closely related to Ce 3Pd 6Sb 5 ( oP28, Pmmn). The crystal structure of Yb 3Cu 8Sn 4, isotypic with Nd 3Co 8Sn 4, was refined from powder data by the Rietveld method: hexagonal, P6 3mc, hP30, a=9.080(1) , c=7.685(1) , Z=2, Rwp=0.040. It is an ordered substitution derivative of the BaLi 4 type ( hP30, P6 3/ mmc). All compounds show strong Cu-Sn bonds with a length reaching 2.553(3) in Yb 5Cu 11Sn 8.

  10. Composition and temperature dependence of the Yb valence in YbMn6Ge6-xSnx studied by RIXS

    NASA Astrophysics Data System (ADS)

    Mazet, T.; Malterre, D.; Franois, M.; Eichenberger, L.; Grioni, M.; Dallera, C.; Monaco, G.

    2015-08-01

    We investigate the composition and temperature (10-450 K) dependence of the Yb valence in YbMn6Ge6 -xSnx (x =0.0 , 3.8, 4.2, 4.4, and 5.5) using resonant inelastic x-ray scattering (RIXS). The observed change in the Yb valence with composition (from ? 3 for x =0 to ? 2.7 for x =5.5 ) is likely driven by negative chemical pressure effects due to the Sn for Ge substitution. While Yb is nonmagnetic in YbMn6Ge0.5Sn5.5 , intermediate valent Yb magnetically orders at unexpectedly high temperature (up to 90 K) in the alloys with x =3.8 , 4.2, and 4.4. The three latter alloys further exhibit an increase in the Yb valence upon cooling, which is opposite to the usual behavior. Interactions with the magnetically ordered Mn sublattice are invoked to account for these unprecedented phenomena through a simplified model based on an Anderson Hamiltonian with a Zeeman term mimicking the Mn-Yb exchange interactions. We further show that the Yb magnetic behavior in this series can be interpreted based on Doniach's picture. Compared with standard intermediate valent materials where Yb is embedded in a nonmagnetic matrix, the strong Mn-Yb exchange interaction enhances the intermediate valent Yb magnetic ordering temperature and allows for extending the stability domain of the Yb magnetic order towards lower Yb valence.

  11. Level structure of /sup 174/Yb from the /sup 173/Yb(n,. gamma. ) reaction

    SciTech Connect

    Greenwood, R.C.; Reich, C.W.

    1981-01-01

    The level structure of /sup 174/Yb has been studied using the /sup 173/Yb(n,..gamma..) reaction with both thermal and 2-keV neutrons. Measurements of ..gamma..-ray energies and intensities were made using Ge(Li) detectors. From these data a neutron separation energy of 7464.8 +- 0.5 keV has been determined for /sup 174/Yb. A level scheme is proposed for /sup 174/Yb which contains 47 excited states, with identified de-excitation modes, below 2.35 MeV. Features of the proposed level scheme include: the K/sup ..pi../=2/sup -/, 0/sup -/, and 3/sup -/ octupole-vibrational bands with band-head energies of 1318, 1710, and 1851 keV, respectively; the ..gamma..-vibrational band at 1634 keV; three excited K/sup ..pi../=0/sup +/ bands with band-head energies of 1487, 1885, and 2100 keV; and, several two-quasiparticle bands with band-head energies in keV (and K/sup ..pi../ assignments) of 1606(3/sup +/), 1624(1/sup +/), 2016(3/sup +/), and 2049(3/sup -/). Configuration assignments for these two-quasiparticle bands are discussed. The available data for the K/sup ..pi../=3/sup +/ band at 1606 keV are not inconsistent with the assumption that it has collective character; and it is suggested that it, together with the lowest-lying 3/sup +/ band in /sup 172/Yb (at 1172 keV), might represent, in the framework of the interacting boson approximation model, examples of g-boson excitations.

  12. Eu{sub 3}F{sub 4}S{sub 2}: Synthesis, crystal structure, and magnetic properties of the mixed-valent europium(II,III) fluoride sulfide EuF{sub 2}.(EuFS){sub 2}

    SciTech Connect

    Grossholz, Hagen; Hartenbach, Ingo; Kotzyba, Gunter; Poettgen, Rainer; Trill, Henning; Mosel, Bernd D.; Schleid, Thomas

    2009-11-15

    Using the method to synthesize rare-earth metal(III) fluoride sulfides MFS (M=Y, La, Ce-Lu), in some cases we were able to obtain mixed-valent compounds such as Yb{sub 3}F{sub 4}S{sub 2} instead. With Eu{sub 3}F{sub 4}S{sub 2} another isotypic representative has now been synthesized. Eu{sub 3}F{sub 4}S{sub 2} (tetragonal, I4/mmm, a=400.34(2), c=1928.17(9) pm, Z=2) is obtained from the reaction of metallic europium, elemental sulfur, and europium trifluoride in a molar ratio of 5:6:4 within seven days at 850 deg. C in silica-jacketed gas-tightly sealed platinum ampoules. The single-phase product consists of black plate-shaped single crystals with a square cross section, which can be obtained from a flux using equimolar amounts of NaCl as fluxing agent. The crystal structure is best described as an intergrowth structure, in which one layer of CaF{sub 2}-type EuF{sub 2} is followed by two layers of PbFCl-type EuFS when sheeted parallel to the (001) plane. Accordingly there are two chemically and crystallographically different europium cations present. One of them (Eu{sup 2+}) is coordinated by eight fluoride anions in a cubic fashion, the other one (Eu{sup 3+}) exhibits a monocapped square antiprismatic coordination sphere with four F{sup -} and five S{sup 2-} anions. Although the structural ordering of the different charged europium cations is plausible, a certain amount of charge delocalization with some polaron activity has to take place, which is suggested by the black color of the title compound. Temperature dependent magnetic susceptibility measurements of Eu{sub 3}F{sub 4}S{sub 2} show Curie-Weiss behavior with an experimental magnetic moment of 8.19(5) mu{sub B} per formula unit and a paramagnetic Curie temperature of 0.3(2) K. No magnetic ordering is observed down to 4.2 K. In accordance with an ionic formula splitting like (Eu{sup II})(Eu{sup III}){sub 2}F{sub 4}S{sub 2} only one third of the europium centers in Eu{sub 3}F{sub 4}S{sub 2} carry permanent magnetic moments. {sup 151}Eu-Moessbauer spectroscopic experiments at 4.2 K show one signal at an isomer shift of -12.4(1) mm/s and a second one at 0.42(4) mm/s. These signals occur in a ratio of 1:2 and correspond to Eu{sup 2+} and Eu{sup 3+}, respectively. The spectra at 78 and 298 K are similar, thus no change in the Eu{sup 2+}/Eu{sup 3+} fraction can be detected. - Graphical abstract: Crystal structure and {sup 151}Eu-Moessbauer spectra of mixed-valent Eu{sub 3}F{sub 4}S{sub 2}.

  13. Ternary rare earth-lanthanide sulfides. [Re = Eu, Sm or Yb

    DOEpatents

    Takeshita, Takuo; Gschneidner, K.A. Jr.; Beaudry, B.J.

    1986-03-06

    Disclosed is a new ternary rare earth sulfur compound having the formula La/sub 3-x/M/sub x/S/sub 4/, where M is europium, samarium, or ytterbium, with x = 0.15 to 0.8. The compound has good high-temperature thermoelectric properties and exhibits long-term structural stability up to 1000/sup 0/C.

  14. Materials Data on EuYbSi4N7 (SG:186) by Materials Project

    SciTech Connect

    Kristin Persson

    2015-01-27

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  15. Magnetic behavior of YbNiSb

    SciTech Connect

    Dhar, S.K.; Ramakrishnan, S.; Vijayaraghavan, R.; Chandra, G. ); Satoh, K.; Itoh, J.; Onuki, Y. ); Gschneidner, K.A. Jr. )

    1994-01-01

    From low-temperature heat capacity and ac susceptibility data it is inferred that YbNiSb orders magnetically at 0.8 K. An unusually large magnetic-field dependence of the heat capacity measured up to 20 K, and also a large decrease in the electrical resistivity ([similar to]1200 [mu][Omega] cm) below 150 K are observed. These data suggest an appreciable dynamical mass renormalization of the quasiparticles due to a 4[ital f] conduction-band mixing effect.

  16. Nanosecond cryogenic Yb:YAG disk laser

    SciTech Connect

    Perevezentsev, E A; Mukhin, I B; Kuznetsov, I I; Vadimova, O L; Palashov, O V

    2014-05-30

    A cryogenic Yb:YAG disk laser is modernised to increase its average and peak power. The master oscillator unit of the laser is considerably modified so that the pulse duration decreases to several nanoseconds with the same pulse energy. A cryogenic disk laser head with a flow-through cooling system is developed. Based on two such laser heads, a new main amplifier is assembled according to an active multipass cell scheme. The total small-signal gain of cryogenic cascades is ∼10{sup 8}. (lasers)

  17. NIR and CT luminescence spectra of [Yb(TFN)(S-BINAPO)] and [Yb(HFA)(S-BINAPO)] complexes.

    PubMed

    Subhan, Md Abdus; Nakata, Hiroyasu

    2014-09-15

    The complexes [Yb(TFN)3(S-BINAPO)](TFN=4,4,4-trifluoro-1(2-napthyl)-1,3-butanedione) (complex 1) and [Yb(HFA)3(S-BINAPO)](HFA=hexafluoroacetylacetonate) (complex 2) were synthesized, characterized. The absorption as well as PL spectra have been studied. The complex [Yb(TFN)3(S-BINAPO)] showed narrowed emission peak (half width ?6 nm) at around 981 nm in addition to several emission peaks in NIR (near infrared) region. The complex [Yb(HFA)3(S-BINAPO)] showed strong emission peak at around 985 nm. The charge transfer luminescence of [Yb(TFN)3(S-BINAPO)] was also observed at 412-463 nm. PMID:24762571

  18. Tightly focused, ultrafast TM01 laser pulses

    NASA Astrophysics Data System (ADS)

    April, Alexandre

    2009-06-01

    Nowadays, the generation of laser pulses focused to a spot size comparable to the wavelength and whose duration is only a few optical cycles of the electric field is achievable. Moreover, TM01 laser pulses are of considerable interest, among other things, because of their remarkable focusing properties. In order to describe theoretically the spatiotemporal behaviour of such nonparaxial, ultrashort TM01 pulses, one needs expressions of their electromagnetic fields. To obtain these expressions, Maxwell's equations must be solved rigorously. The method of the Hertz potential, the complex-source/sink model, and the use of a Poisson-like spectrum are exploited to solve the vectorial wave equation. Closed-form expressions for the electric and the magnetic fields of an isodiffracting TM01 pulse are presented and they can be used to study the behaviour of tightly focused, ultrafast TM pulses.

  19. New ternary phosphides and arsenides. Syntheses, crystal structures, physical properties of Eu{sub 2}ZnP{sub 2}, Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}

    SciTech Connect

    Wang, Jian; Xia, Sheng-Qing; Tao, Xu-Tang; Schäfer, Marion C.; Bobev, Svilen

    2013-09-15

    Three new europium pnictides Eu{sub 2}ZnP{sub 2}, Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3} have been synthesized and their structures were determined by single-crystal X-ray diffraction. Eu{sub 2}ZnP{sub 2} is isotypic with Yb{sub 2}CdSb{sub 2} (Cmc2{sub 1} (No. 36); cell parameters a=4.1777(7) Å, b=15.925(3) Å, c=7.3008(12) Å), while the latter two compounds crystallize with the Ba{sub 2}Cd{sub 2}Sb{sub 3} structure type (C2/m (No. 12); cell parameters a=15.653(5)/16.402(1) Å, b=4.127(1)/4.445(4) Å, c=11.552(4)/12.311(1) Å and β=126.647(4)/126.515(7)° for Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}, respectively). Magnetic susceptibility measurements in the interval 5–300 K confirm paramagnetic behavior and effective magnetic moments characteristic of Eu{sup 2+} ([Xe] 4f{sup 7}) ground states. Temperature-dependent electrical conductivity measurements also prove that Eu{sub 2}Cd{sub 2}As{sub 3} is a semiconducting compound with a narrow band gap of 0.059 eV below 100 K. According to TG/DSC analyses, Eu{sub 2}Cd{sub 2}As{sub 3} starts to decompose at about 950 K. - Graphical abstract: A polyhedral view of the crystal structure of new pnictides Eu{sub 2}T{sub 2}Pn{sub 3} (T=Zn or Cd; Pn=P or As). Display Omitted - Highlights: • Three new ternary pnictide Zintl compounds, Eu{sub 2}ZnP{sub 2}, Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}, have been synthesized and characterized. • The europium cations are divalent and ferromagnetically coupled in both Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}. • Eu{sub 2}Cd{sub 2}As{sub 3} has a very small band gap of 0.06 eV and starts to decompose over 950 K.

  20. Synthesis and structure of nanocrystalline mixed CeYb silicates

    SciTech Connect

    Ma?ecka, Ma?gorzata A. K?pi?ski, Leszek

    2013-07-15

    Graphical abstract: - Highlights: New method of synthesis of nanocrystalline mixed lanthanide silicates is proposed. Formation of A-type (Ce{sub 1?y}Yb{sub y}){sub 2}Si{sub 2}O{sub 7} in well dispersed Ce{sub 1?x}Yb{sub x}O{sub 2?(x/2)}SiO{sub 2} system. Formation of Yb{sub y}Ce{sub 9.33?y}(SiO{sub 4}){sub 6}O{sub 2} in agglomerated Ce{sub 1?x}Yb{sub x}O{sub 2?(x/2)}SiO{sub 2} system. - Abstract: This work presents results of studies on synthesis and structure of mixed, nanocrystalline CeYb silicates. Using TEM, XRD and FTIR we showed that heat treatment of nanocrystalline Ce{sub 1?x}Yb{sub x}O{sub 2?(x/2)} (x = 0.3, 0.5) mixed oxide supported on amorphous silica in reducing atmosphere, results in formation of CeYb mixed silicates. Dispersion of the oxide on the silica surface and thus a local lanthanide/Si atomic ratio determines the stoichiometry of the silicate. Oxide crystallites uniformly dispersed on the silica surface transformed into A-(Ce{sub 1?y}Yb{sub y}){sub 2}Si{sub 2}O{sub 7} disilicate, while the agglomerated nanoparticles converted into Yb{sub y}Ce{sub 9.33?y}(SiO{sub 4}){sub 6}O{sub 2} oxyapatite silicate as an intermediate phase.

  1. Optical properties of Yb ions in GaN epilayer

    NASA Astrophysics Data System (ADS)

    Jadwisienczak, W. M.; Lozykowski, H. J.

    2003-07-01

    In recent years, an important effort in semiconductor materials research has been devoted to III-nitrides semiconductors doped with rare earth ions due to the high potential of these materials in light-emitting device applications. Ytterbium (Yb 3+) is one of a few lanthanide ions which have not been investigated as an optically active center in these materials yet. In this paper we report the observation of luminescence from GaN films grown on sapphire (0 0 0 1) substrate by metal organic chemical vapor deposition and doped by implantation with Yb 3+ ions. The high resolution photo- and cathodoluminescence spectra of GaN:Yb 3+ were studied at different excitation conditions in temperatures ranging from 8 to 330 K and revealed weak thermal quenching. The luminescence emission lines are assigned to transitions between the spin-orbit levels 2F 5/2 ? 2F 7/2 of Yb 3+ (4f 13). The analysis of the Yb luminescence spectra allowed us to suggest the energy level diagram of the crystal-field-split 4f 13 levels for the Yb ion center. The most probable lattice location of Yb in GaN is the substitutional Ga site. Furthermore, the luminescence kinetics of internal transitions of Yb 3+ incorporated in GaN was investigated by means of decay and time-resolved luminescence measurements. It was found that the ytterbium decay is non-exponential with dominant exponential term of 100 ?s with little dependence on the ambient temperature. The results indicate that Yb-doped GaN epilayer may be suitable as a material for near infrared optoelectronic devices.

  2. Field-induced quantum criticality in YbAgGe

    SciTech Connect

    Bud'ko, S.; Canfield, P.

    2008-01-01

    YbAgGe is one of the very few stoichiometric, Yb-based, heavy fermion materials that exhibit field-induced quantum criticality. We will present an overview of thermodynamic and transport measurements in YbAgGe single crystals. Moderate magnetic field (45-90 kOe, depending on orientation) suppresses long range magnetic order, giving rise to non-Fermi-liquid behavior followed at higher field by a crossover to a heavy Fermi-liquid. Given the more accessible temperature and field scales, a non-Fermi liquid region rather than point for T {yields} 0 K may be detected.

  3. From the ternary Eu(Au/In)2 and EuAu4(Au/In)2 with remarkable Au/In distributions to a new structure type: The gold-rich Eu5Au16(Au/In)6 structure

    DOE PAGESBeta

    Steinberg, Simon; Card, Nathan; Mudring, Anja -Verena

    2015-08-13

    The ternary Eu(Au/In)2 (EuAu0.46In1.54(2)) (I), EuAu4(Au/In)2 (EuAu4+xIn2–x with x = 0.75(2) (II), 0.93(2), and 1.03(2)), and Eu5Au16(Au/In)6 (Eu5Au17.29In4.71(3)) (III) have been synthesized, and their structures were characterized by single-crystal X-ray diffraction. I and II crystallize with the CeCu2-type (Pearson Symbol oI12; Imma; Z = 4; a = 4.9018(4) Å; b = 7.8237(5) Å; c = 8.4457(5) Å) and the YbAl4Mo2-type (tI14; I4/mmm; Z = 2; a = 7.1612(7) Å; c = 5.5268(7) Å) and exhibit significant Au/In disorder. I is composed of an Au/In-mixed diamond-related host lattice encapsulating Eu atoms, while the structure of II features ribbons of distorted, squaredmore » Au8 prisms enclosing Eu, Au, and In atoms. Combination of these structural motifs leads to a new structure type as observed for Eu5Au16(Au/In)6 (Eu5Au17.29In4.71(3)) (oS108; Cmcm; Z = 4; a = 7.2283(4) Å; b = 9.0499(6) Å; c = 34.619(2) Å), which formally represents a one-dimensional intergrowth of the series EuAu2–“EuAu4In2”. The site preferences of the disordered Au/In positions in II were investigated for different hypothetical “EuAu4(Au/In)2” models using the projector-augmented wave method and indicate that these structures attempt to optimize the frequencies of the heteroatomic Au–In contacts. Furthermore, a chemical bonding analysis on two “EuAu5In” and “EuAu4In2” models employed the TB-LMTO-ASA method and reveals that the subtle interplay between the local atomic environments and the bond energies determines the structural and site preferences for these systems.« less

  4. From the Ternary Eu(Au/In)2 and EuAu4(Au/In)2 with Remarkable Au/In Distributions to a New Structure Type: The Gold-Rich Eu5Au16(Au/In)6 Structure.

    PubMed

    Steinberg, Simon; Card, Nathan; Mudring, Anja-Verena

    2015-09-01

    The ternary Eu(Au/In)2 (EuAu(0.46)In(1.54(2))) (I), EuAu4(Au/In)2 (EuAu(4+x)In(2-x) with x = 0.75(2) (II), 0.93(2), and 1.03(2)), and Eu5Au16(Au/In)6 (Eu5Au(17.29)In(4.71(3))) (III) have been synthesized, and their structures were characterized by single-crystal X-ray diffraction. I and II crystallize with the CeCu2-type (Pearson Symbol oI12; Imma; Z = 4; a = 4.9018(4) Å; b = 7.8237(5) Å; c = 8.4457(5) Å) and the YbAl4Mo2-type (tI14; I4/mmm; Z = 2; a = 7.1612(7) Å; c = 5.5268(7) Å) and exhibit significant Au/In disorder. I is composed of an Au/In-mixed diamond-related host lattice encapsulating Eu atoms, while the structure of II features ribbons of distorted, squared Au8 prisms enclosing Eu, Au, and In atoms. Combination of these structural motifs leads to a new structure type as observed for Eu5Au16(Au/In)6 (Eu5Au(17.29)In(4.71(3))) (oS108; Cmcm; Z = 4; a = 7.2283(4) Å; b = 9.0499(6) Å; c = 34.619(2) Å), which formally represents a one-dimensional intergrowth of the series EuAu2-"EuAu4In2". The site preferences of the disordered Au/In positions in II were investigated for different hypothetical "EuAu4(Au/In)2" models using the projector-augmented wave method and indicate that these structures attempt to optimize the frequencies of the heteroatomic Au-In contacts. A chemical bonding analysis on two "EuAu5In" and "EuAu4In2" models employed the TB-LMTO-ASA method and reveals that the subtle interplay between the local atomic environments and the bond energies determines the structural and site preferences for these systems. PMID:26270622

  5. Magnetic structure of the ferromagnetic Kondo-lattice compounds YbPtGe and YbPdGe

    NASA Astrophysics Data System (ADS)

    Tsujii, Naohito; Katoh, Kenichi; Keller, Lukas; Dnni, Andreas; Terada, Noriki; Kitazawa, Hideaki

    2015-08-01

    YbPtGe and YbPdGe exhibit ferromagnetic ordering below {{T}\\text{C}}=5.4 and 11.4 K with enhanced electronic specific heat coefficients of ? =209 and 150 mJ K-2 mol, respectively. In order to shed light on the origin of the coexistence of a ferromagnetic state and heavy-fermion behavior, we studied the powder neutron diffraction of YbPtGe and YbPdGe at low temperatures. Weak reflections due to magnetic ordering have been resolved. The data were analyzed using the Rietveld method together with group theory analysis. It has been found that YbPtGe exhibits a non-collinear ferromagnetic structure, with a spontaneous moment along the c-axis and a weak antiferromagnetic component along the a-axis. The presence of this antiferromagnetic component explains the origin of the observed metamagnetic-like behavior. In the case of YbPdGe, magnetization measurements confirmed the ferromagnetic moment along the b-axis and revealed a metamagnetic transition at 0.2 T for a field parallel to the c-axis. The neutron diffraction results indicate that the magnetic structure of YbPdGe is also of a non-collinear type, with ferromagnetic moments parallel to the b-axis and weak antiferromagnetic components along the c-axis, which is consistent with the magnetization data. A comparison of the results for YbPtGe and YbPdGe has been made. It is suggested that both the Kondo screening effect of ferromagnetic moments and the fluctuation of antiferromagnetic components can contribute to the enhanced mass in the ferromagnetic state.

  6. QCD For Intel(R) Xeon Phi(tm) and Xeon(tm) processors

    SciTech Connect

    2014-09-11

    This library provides a library containing highly optimized Wilson-Dslash, Wilson Clover operator and Krylov subspace solvers for Lattice QCD simulations. The library is targeted at Intel(R) Xeon Phi(tm), and Intel(R) Xeon(tm) processors.

  7. Modeling Cr-to-Tm and Cr-to-Tm-to-Ho energy transfer in YAG crystals

    NASA Technical Reports Server (NTRS)

    Swetits, John J.

    1991-01-01

    A systematic analysis of energy transfer processes in crystals of YAG doped with varying concentrations of Cr and Tm is described. Both spectral measurements and measurements of the temporal response to pulsed excitation are used to give independent determinations of the microscopic interaction parameter for Cr to Tm transfer. The different factors in influencing the temperature dependence of the Cr to Tm transfer are discussed. The dependence of the Tm cross-relaxation rate on Tm concentration is determined.

  8. 151Eu Mssbauer study of luminescent Y2O3:Eu3 + core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Kuzmann, E.; Vrtes, A.; Bohus, G.; Hornok, V.; Oszk, A.; Dkny, I.

    2013-04-01

    151Eu Mssbauer spectroscopy was applied to distinguish among different Eu microenvironments and phases in spherical Y2O3:Eu3 + and core-shell Y2O3@Eu3 + phosphor nanoparticles prepared by using homogeneous precipitation method. 151Eu isomer shift revealed that Eu atoms exist only in oxidation state Eu3 + in all spherical and core-shell phosphors. Significant differences have been found between the Mssbauer parameters (isomer shift, principal component of EFG and linewidth) characteristic of spherical Y2O3:Eu3 + and core-shell Y2O3@Eu3 + phosphor nanoparticles. The Mssbauer parameters of spherical Y2O3:Eu3 + were associated with Eu substituting Y in the Y2O3, while Mssbauer parameters of core-shell Y2O3@Eu3 + phosphor were attributed to Eu being in the Eu2O3 shell, proving the structural model and the successful preparation of these phosphors.

  9. The tmRDB and SRPDB resources

    PubMed Central

    Andersen, Ebbe Sloth; Rosenblad, Magnus Alm; Larsen, Niels; Westergaard, Jesper Cairo; Burks, Jody; Wower, Iwona K.; Wower, Jacek; Gorodkin, Jan; Samuelsson, Tore; Zwieb, Christian

    2006-01-01

    Maintained at the University of Texas Health Science Center at Tyler, Texas, the tmRNA database (tmRDB) is accessible at the URL with mirror sites located at Auburn University, Auburn, Alabama () and the Royal Veterinary and Agricultural University, Denmark (). The signal recognition particle database (SRPDB) at is mirrored at and the University of Goteborg (). The databases assist in investigations of the tmRNP (a ribonucleoprotein complex which liberates stalled bacterial ribosomes) and the SRP (a particle which recognizes signal sequences and directs secretory proteins to cell membranes). The curated tmRNA and SRP RNA alignments consider base pairs supported by comparative sequence analysis. Also shown are alignments of the tmRNA-associated proteins SmpB, ribosomal protein S1, alanyl-tRNA synthetase and Elongation Factor Tu, as well as the SRP proteins SRP9, SRP14, SRP19, SRP21, SRP54 (Ffh), SRP68, SRP72, cpSRP43, Flhf, SRP receptor (alpha) and SRP receptor (beta). All alignments can be easily examined using a new exploratory browser. The databases provide links to high-resolution structures and serve as depositories for structures obtained by molecular modeling. PMID:16381838

  10. Bulk and surface valence in YbPd/sub x/ compounds

    SciTech Connect

    Domke, M.; Laubschat, C.; Sampathkumaran, E.V.; Prietsch, M.; Mandel, T.; Kaindl, G.; Middelmann, H.U.

    1985-12-15

    The bulk and surface valence v-bar of Yb is investigated for YbPd/sub x/ intermetallic compounds (with x = 1,1.33,3) by photoemission using synchrotron radiation. YbPd is found to be of intermediate valence (v-barapprox. =2.75), while Yb/sub 3/Pd/sub 4/ and YbPd/sub 3/ are identified as bulk trivalent systems. The outermost atomic surface layer of both YbPd and Yb/sub 3/Pd/sub 4/ is found to be divalent, while only a fraction of Yb surface atoms turns divalent in YbPd/sub 3/. The results are compared with bremsstrahlung isochromat spectroscopy measurements and predictions based on Miedema's scheme.

  11. Growth and spectral properties of Yb:FAP single crystal

    NASA Astrophysics Data System (ADS)

    Song, Pingxin; Zhao, Zhiwei; Xu, Xiaodong; Deng, Peizhen; Xu, Jun

    2007-01-01

    In this paper, single crystal of ytterbium (Yb) doped Ca 5(PO 4) 3F (FAP) has been grown along the c-axis by using the Czochralski method. The segregation coefficients of Yb 3+ in the Yb:FAP crystal has been determined by ICP-AES method. The absorption spectrum, fluorescence spectrum and fluorescence lifetime of the Yb:FAP crystal has been also measured at room temperature. In the absorption spectra, there are two absorption bands at 904 and 982 nm, respectively, which are suitable for InGaAs diode laser pumping. The absorption cross-section ( ?abs) is 5.117 10 -20 cm 2 with an FWHM of 4 nm at 982 nm. The emission cross-section ( ?em) is 3.678 10 -20 cm 2 at 1042 nm. Favorable values of the absorption cross-section at about 982 nm are promising candidates for laser diode (LD) pumping.

  12. Indirect excitation of Eu3+ in GaN codoped with Mg and Eu

    NASA Astrophysics Data System (ADS)

    Yamaga, M.; Watanabe, H.; Kurahashi, M.; O'Donnell, K. P.; Lorenz, K.; Boćkowski, M.

    2015-06-01

    Temperature-dependent Eu3+ luminescence spectra in GaN(Mg):Eu can be assigned to, at least, two distinct Eu3+ centres, denoted by Eu0 and Eu1. The splitting energy levels of the 7FJ (J=1,2) multiplets for the Eu0 and Eu1 centres have been calculated using the equivalent operator Hamiltonian for C3v crystal field with the addition of an odd parity distortion.

  13. Multimodal bioimaging using rare earth doped Gd2O2S: Yb/Er phosphor with upconversion luminescence and magnetic resonance properties

    PubMed Central

    Ajithkumar, G.; Yoo, Benjamin; Goral, Dara E.; Hornsby, Peter J.; Lin, Ai-Ling; Ladiwala, Uma; Dravid, Vinayak P.; Sardar, Dhiraj K

    2013-01-01

    While infrared upconversion imaging using halide nanoparticles are so common the search for a very efficient halide free upconverting phosphors is still lacking. In this article we report Gd2O2S:Yb/Er,YbHo,YbTm systems as a very efficient alternative phosphors that show upconversion efficiency comparable or even higher than existing halide phosphors. While the majority of rare earth dopants provide the necessary features for optical imaging, the paramagnetic Gd ion also contributes to the magnetic imaging,thereby resulting in a system with bimodal imaging features. Results from imaging of the nanoparticles together with aggregates of cultured cells have suggested that imaging of the particles in living animals may be possible. In vitro tests revealed no signficant toxicity because no cell death was observed when the nanoparticles were in the presence of growing cells in culture. Measurement of the magnetization of the phosphor shows that the particles are strongly magnetic, thus making them suitable as an MRI agent. PMID:25191618

  14. Materials Data on EuTmCuS3 (SG:63) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  15. g factor of the first 2+ state in 164Yb

    SciTech Connect

    Z. Berant; A. Wolf et al.

    2004-03-17

    The g factor of the first excited 2+ state of 164Yb was measured by perturbed gamma-gamma angular correlation in an external static magnetic field of 5.55T. The result g(2+)=0.32(5), extends the systematics for Yb isotopes down to N=94. The behavior of known experimental values of g(2+) vs N for all isotopic chains Ba to Pt is discussed.

  16. Application of Yb:YAG short pulse laser system

    DOEpatents

    Erbert, Gaylen V.; Biswal, Subrat; Bartolick, Joseph M.; Stuart, Brent C.; Crane, John K.; Telford, Steve; Perry, Michael D.

    2004-07-06

    A diode pumped, high power (at least 20W), short pulse (up to 2 ps), chirped pulse amplified laser using Yb:YAG as the gain material is employed for material processing. Yb:YAG is used as the gain medium for both a regenerative amplifier and a high power 4-pass amplifier. A single common reflective grating optical device is used to both stretch pulses for amplification purposes and to recompress amplified pulses before being directed to a workpiece.

  17. Spectroscopic properties and laser performances of Yb:YCOB and potential of the Yb:LaCOB material

    NASA Astrophysics Data System (ADS)

    Aron, A.; Aka, G.; Viana, B.; Kahn-Harari, A.; Vivien, D.; Druon, F.; Balembois, F.; Georges, P.; Brun, A.; Lenain, N.; Jacquet, M.

    2001-02-01

    In order to increase the compacity of the Yb-doped lasers, YCOB (Ca 4Y(BO 3) 3) materials with high ytterbium concentration have been characterized. Large 15 at.% and 35 at.% ytterbium-doped single crystals were grown by the Czochralski pulling method. Spectroscopic and laser properties have been investigated and laser tests performed under titanium sapphire and diode pumping at 976 nm. Low thresholds under Ti:Sa pumping (50 mW) and high slope efficiency under diode pumping (66%) have been obtained. The optical quality and the distribution of Yb 3+ dopant through the highly doped crystals is discussed. First results on the Yb:LaCOB crystals grown by the Czochralski process, containing 46Yb 3+ at.%, are also presented.

  18. Optical and scintillation properties of transparent ceramic Yb:Lu2O3 with different Yb concentrations

    NASA Astrophysics Data System (ADS)

    Yanagida, Takayuki; Fujimoto, Yutaka; Yagi, Hideki; Yanagitani, Takagimi

    2014-04-01

    Yb 0.1-100% doped Lu2O3 transparent ceramic scintillators were prepared by Konoshima Chemical. They had 60-80% transparency at wavelength longer than 240 nm and absorption bands around 970 nm due to 4f-4f transition of Yb3+ were observed. In photoluminescence and X-ray induced radioluminescence, Yb3+ charge transfer luminescence appeared at 330 and 490 nm. Photoluminescence and scintillation decay times of the charge transfer luminescence resulted 0.5-1.5 ns. 137Cs excited pulse height spectrum was evaluated to determine the light yield of the fast component and Yb 0.3% doped sample exhibited the highest light yield of 500 ph/MeV.

  19. Biosimilar regulation in the EU.

    PubMed

    Kurki, Pekka; Ekman, Niklas

    2015-01-01

    In the EU, the EMA has been working with biosimilars since 1998. This experience is crystallized in the extensive set of guidelines, which range from basic principles to details of clinical trials. While the guidance may appear complicated, it has enabled the development of biosimilars, of which 21 have managed to get marketing authorization. Currently marketed biosimilars in the EU have a good track record in safety and traceability. No biosimilars have been withdrawn from the market because of safety concerns. The most controversial issues with biosimilars are immunogenicity and extrapolation of therapeutic indications. The available data for these topics do not raise concerns among EU regulators. Interchangeability and substitution are regulated by individual EU member states. PMID:26294076

  20. Beta-Decay Study of ^{150}Er, ^{152}Yb, and ^{156}Yb: Candidates for a Monoenergetic Neutrino Beam Facility

    SciTech Connect

    Estevez Aguado, M. E.; Algora, A.; Rubio, B.; Bernabeu, J.; Nacher, E.; Tain, J. L.; Gadea, A.; Agramunt, J.; Burkard, K.; Hueller, W.; Doring, J.; Kirchner, R.; Mukha, I.; Plettner, C.; Roeckl, E.; Grawe, H.; Collatz, R.; Hellstrom, M.; Cano-Ott, D.; Karny, M.; Janas, Z.; Gierlik, M.; Plochocki, A.; Rykaczewski, Krzysztof Piotr; Batist, L.; Moroz, F.; Wittman, V.; Blazhev, A.; Valiente, J. J.; Espinoza, C.

    2011-01-01

    The beta decays of ^{150}Er, ^{152}Yb, and ^{156}Yb nuclei are investigated using the total absorption spectroscopy technique. These nuclei can be considered possible candidates for forming the beam of a monoenergetic neutrino beam facility based on the electron capture (EC) decay of radioactive nuclei. Our measurements confirm that for the cases studied, the EC decay proceeds mainly to a single state in the daughter nucleus.

  1. Variation in luminescence behavior of Yb3+ doped GdAlO3 phosphor with gradual increase in Yb3+ concentration

    NASA Astrophysics Data System (ADS)

    Tamrakar, Raunak Kumar; Upadhyay, Kanchan; Bisen, D. P.

    2016-03-01

    The present paper reports the combustion synthesis of Yb3+ doped GdAlO3 phosphors. The structural characterization and luminescence spectra of Yb3+ doped GdAlO3 phosphors have been discussed. The effects of variable concentration of Yb3+ on Photoluminescence (PL) behavior were studied. The structural characterization was done by X-ray diffraction (XRD) and Transmission electron microscope technique (TEM). The good connectivity with grains and the semi-sphere line structure was found by TEM. The functional group analysis was carried out by Fourier transform infrared (FTIR) spectroscopic techniques. The prepared phosphor gives emission spectra in visible as well as NIR region. Both emissions were studied as a function of Yb3+ concentration. The emission intensity variation with Yb3+ ion concentration for visible and NIR region were discussed separately. The NIR emission luminescence of GdAlO3:Yb3+ phosphor luminescence continuously increases with increasing Yb3+ ion concentration.

  2. HSP60 interacts with YB-1 and affects its polysome association and subcellular localization

    SciTech Connect

    Ohashi, Sachiyo; Atsumi, Megumi; Kobayashi, Shunsuke

    2009-08-07

    YB-1 is a DNA/RNA-binding protein which, in the cytoplasm, associates with polysomes and regulates translation. However, YB-1 has a novel nuclear localization signal, and its nuclear accumulation is correlated with cancer induction. Here we designated the amino-acid sequence as YB-NLS and demonstrated that YB-NLS is necessary for the nuclear translocation of overexpressed YB-1 in NG108-15 cells. In addition, we found that a heat shock protein, HSP60, binds to YB-NLS in the cytoplasm. Interestingly, when HSP60 expression was repressed, an increase of polysome-associated YB-1 was observed in heavy-sedimenting fractions on a sucrose gradient. Overexpression of HSP60 resulted in a decrease of YB-1 in the heavy-sedimenting fractions and suppression of YB-NLS activity. Furthermore, the NLS-deleted YB-1 was apparently associated with the heavy-sedimenting polysomes. These results suggest that HSP60 interacts with YB-1 at the YB-NLS region and acts as a regulator of polysome association and the subcellular distribution of YB-1.

  3. Doors to Discovery [TM]. WWC Intervention Report

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2009

    2009-01-01

    Doors to Discovery[TM], an early childhood curriculum, focuses on the development of children's vocabulary and expressive and receptive language through a learning process called "shared literacy," where adults and children work together to develop literacy-related skills. Literacy activities, organized into thematic units, encourage children's

  4. The Neuroscience of PowerPoint[TM

    ERIC Educational Resources Information Center

    Horvath, Jared Cooney

    2014-01-01

    Many concepts have been published relevant to improving the design of PowerPoint[TM] (PP) presentations for didactic purposes, including the redundancy, modality, and signaling principles of multimedia learning. In this article, we review the recent neuroimaging findings that have emerged elucidating the neural structures involved in many of these

  5. Associations with Minspeak[TM] Icons

    ERIC Educational Resources Information Center

    van der Merwe, Elmarie; Alant, Erna

    2004-01-01

    Although the Minspeak[TM] approach is used on communication devices worldwide, little research has been conducted on its applicability within specific cultural contexts. The impact that users' familiarity of symbols and associations can have on learnability necessitates more systematic research. This study was an investigation into the

  6. 75 FR 78234 - Lock+TM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-15

    ... Allegheny Lock and Dam 2 on the Allegheny River near the town of Sharpsburg, in Allegheny County...-foot-long prefabricated concrete wall attached to pilings in the river to support the lock frame module... Energy Regulatory Commission Lock+ TM Hydro Friends Fund XXXVIII, FFP Missouri 12, LLC, et al.; Notice...

  7. 75 FR 78233 - Lock+TM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-15

    ... Energy Regulatory Commission Lock+\\TM\\ Hydro Friends Fund XXXVII; FFP Missouri 6, LLC; Solia 1... Comments, and Motions To Intervene December 8, 2010. On May 18, 2010, Lock+ Hydro Friends Fund XXXVII, FFP... Emsworth Back Channel Dam on the Ohio River in Allegheny County, Pennsylvania. The sole purpose of...

  8. 75 FR 78234 - Lock+TM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-15

    ...; Project No. 13786-000] Lock+ TM Hydro Friends Fund XXXIV; FFP Missouri 5, LLC; Solia 2 Hydroelectric, LLC... Comments, and Motions to Intervene December 8, 2010. On May 18, 2010, Lock+ Hydro Friends Fund XXXIV, FFP... the town of Emsworth, in Allegheny County, Pennsylvania. The sole purpose of a preliminary permit,...

  9. 75 FR 78236 - Lock+TM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-15

    ... Opekiska Lock and Dam on the Monongahela River in Monongahela County, West Virginia. The sole purpose of a... pilings in the river to support the lock frame module; (3) a 25- foot-long, 50-foot-wide switchyard... Energy Regulatory Commission Lock+\\TM\\ Hydro Friends Fund XLVII, FFP Missouri 16, LLC, et al.; Notice...

  10. Defying Gravity Using Jenga[TM] Blocks

    ERIC Educational Resources Information Center

    Tan, Yin-Soo; Yap, Kueh-Chin

    2007-01-01

    This paper describes how Jenga[TM] blocks can be used to demonstrate the physics of an overhanging tower that appears to defy gravity. We also propose ideas for how this demonstration can be adapted for the A-level physics curriculum. (Contains 8 figures and 1 table.)

  11. The Neuroscience of PowerPoint[TM

    ERIC Educational Resources Information Center

    Horvath, Jared Cooney

    2014-01-01

    Many concepts have been published relevant to improving the design of PowerPoint[TM] (PP) presentations for didactic purposes, including the redundancy, modality, and signaling principles of multimedia learning. In this article, we review the recent neuroimaging findings that have emerged elucidating the neural structures involved in many of these…

  12. Laser action in Yb3+: Ycob (Yb3+:YCa4O(BO3)3)

    NASA Astrophysics Data System (ADS)

    Hammons, Dennis A.; Eichenholz, Jason M.; Shah, Lawrence; Ye, Q.; Peale, Robert E.; Chai, Bruce H. T.; Richardson, Martin C.; Chin, Aland K.

    1999-05-01

    Progress in the growth of the rare earth calcium oxyborate crystals has now generated a new class of laser materials that can be used as both a laser host and a nonlinear frequency converter. Laser action and self-frequency doubling (SFD) has been observed with both 10% and 20% Yb3+-doped YCOB crystals. Laser operation was obtained in a hemispherical linear cavity, end-pumped with a tunable cw Ti:Sapphire or a 980 nm laser diode pump source. Under Ti:Sapphire pumping at 900 nm, an output power of 230 mW and a slope efficiency of 29% was obtained using the 10% doped sample. Laser action was seen at 1050 nm. Laser operation of the 20% sample had a maximum output power of approximately 300 mW with a slope efficiency of 35.8% at 1088 nm. Laser action was not obtained at the peak of the fluorescence emission (approximately 1030 nm) in this crystal as a consequence of self-absorption on the short- wavelength side of the emission band. Diode-pumped operation at the narrow absorption peak of 977 nm was achieved and early results show an improved slope efficiency of 34% in comparison to the 10% doped crystal under Ti:Sapphire pumping. We have also observed self-frequency doubling in Yb3+:YCOB. The 20% Yb3+:YCOB crystal used for this test was cut with a phase-matching angle of 36.22 degree(s). The self-frequency doubling efficiency was low due to the absence of any frequency selective elements in the cavity to narrow the linewidth of the fundamental emission. The SFD emission occurred at 543 nm.

  13. Calibration of TM data from ground-based measurements

    NASA Technical Reports Server (NTRS)

    Rasool, S. I.; Deschamps, P. Y.

    1984-01-01

    Methods of calibrating Thematic Mapper (TM) data by the use of ground based measurements are presented. Applications of the TM remote sensing data are discussed in addition to the ground truth measurement equipment and techniques.

  14. CCRS proposal for evaluating LANDSAT-4 MSS and TM data

    NASA Technical Reports Server (NTRS)

    Strome, W. M.; Cihlar, J.; Goodenough, D. G.; Guertin, F. E. (principal investigators); Guindon, B.; Murphy, J.; Butlin, J. M.; Duff, P.; Fitzgerald, A.; Grieve, G.

    1984-01-01

    The measurement of registration errors in LANDSAT MSS data is discussed as well as the development of a revised algorithm for the radiometric calibration of TM data and the production of a geocoded TM image.

  15. Photoemission Studies of Kondo Lattice Compounds YbNi3(Ga1-xAlx)9

    NASA Astrophysics Data System (ADS)

    Utsumi, Yuki; Sato, Hitoshi; Nagata, Heisuke; Kodama, Junichi; Ohara, Shigeo; Yamashita, Tetsuro; Mimura, Kojiro; Motonami, Satoru; Arita, Masashi; Ueda, Shigenori; Shimada, Kenya; Namatame, Hirofumi; Taniguchi, Masaki

    We have investigated the electronic structure of YbNi3 (Ga1-xAlx)9 (x = 0, 0.05, 0.10, 0.15) by means of hard x-ray (h? 6 keV) and low energy (h? 7 eV) photoemission spectroscopies (HAXPES and LEPES). Both Yb2+ and Yb3+ components are observed in the Yb 3d HAXPES spectra, which is an evidence of the valence fluctuation in YbNi3(Ga1-xAlx)9. A substitution of an Al ion for a Ga ion in YbNi3Ga9 changes the Yb ion into a trivalent state. The LEPES spectra of YbNi3Ga9 clearly exhibit the Kondo peak near the Fermi level (EF) and the Kondo temperature is estimated to be TK 550 K. With the Al substitution, the Kondo peak is shifted toward EF, indicating the decrease of TK

  16. High-pressure synthesis, crystal structure, and structural relationship of the first ytterbium fluoride borate Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9}

    SciTech Connect

    Haberer, Almut; Huppertz, Hubert

    2009-04-15

    Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} was synthesized under high-pressure/high-temperature conditions in a Walker-type multianvil apparatus at 7.5 GPa and 1100 deg. C, representing the first known ytterbium fluoride borate. The compound exhibits isolated BO{sub 3}-groups next to ytterbium cations and fluoride anions, showing a structure closely related to the other known rare-earth fluoride borates RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}. Monoclinic Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} crystallizes in space group C2/c with the lattice parameters a=2028.2(4) pm, b=602.5(2) pm, c=820.4(2) pm, and beta=100.63(3){sup o} (Z=4). Three different ytterbium cations can be identified in the crystal structure, each coordinated by nine fluoride and oxygen anions. None of the five crystallographically independent fluoride ions is coordinated by boron atoms, solely by trigonally-planar arranged ytterbium cations. In close proximity to the above mentioned compounds RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}, Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} can be described via alternating layers with the formal compositions 'YbBO{sub 3}' and 'YbF{sub 3}' in the bc-plane. - Graphical abstract: High-pressure/high-temperature synthesis (multianvil technique) led to the first ytterbium fluoride borate Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9}, built up from isolated BO{sub 3}-groups. The compound shows structural relations to the known rare-earth fluoride borates RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}.

  17. Investigation of loss processes of Tm and Tm,Ho in YAG

    NASA Technical Reports Server (NTRS)

    Armagan, G.; Buoncristiani, A. M.; Bair, C. H.; Inge, A. T.; Hess, R. V.

    1991-01-01

    The loss of excitation from various manifolds of Tm and Tm,Ho in YAG as a function of temperature and concentration is studied. Two probable loss mechanisms - a Tm up-conversion and a Ho up-conversion - are identified. A 785-nm CW diode laser with 400-nW peak power was focused to a small spot on the sample. The emission from the sample observed at 90 deg was monitored through a monochromator with slits open to 3 mm. Intensity of emission was measured by varying the power of the excitation source using a set of neutral density filters. Power is reported as the percentage of the peak power, and the intensity curves were normalized below 20 percent of transmission. The fact that there is emission above the pump energy indicates an up-conversion from excited manifolds. Nonlinear changes in the intensity of the emission from the Tm 3F4 manifold with the pump power reveals a loss of excitation from this manifold. The linear dependence of the 5I7 manifold emission with pump power at low Tm and high Ho concentrations and the gain of energy in the 5I6 manifold of Ho indicate that the 5I7 manifold loss is due to the coupling of Tm and Ho ions.

  18. Pioneers--The "Engineering byDesign[TM]" Network

    ERIC Educational Resources Information Center

    Burke, Barry N.

    2006-01-01

    This article discusses the standards-based instruction model, Engineering byDesign[TM] (EbD), and a network of teachers called the Engineering byDesign[TM] Network. Engineering byDesign[TM] is the only standards-based national model for Grades K-12 that delivers technological literacy which was developed by the International Technology Education

  19. Radiative lifetime measurements of some Tm I and Tm II levels by time-resolved laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Tian, Yanshan; Wang, Xinghao; Yu, Qi; Li, Yongfan; Gao, Yang; Dai, Zhenwen

    2016-04-01

    Radiative lifetimes of 88 levels of Tm I in the energy range 22 791.176-48 547.98 cm-1 and 29 levels of Tm II in the range 27 294.79-65 612.85 cm-1 were measured by time-resolved laser-induced fluorescence spectroscopy in laser-ablation plasma. The lifetime values obtained are in the range from 15.4 to 7900 ns for Tm I and from 36.5 to 1000 ns for Tm II. To the best of our knowledge, 77 lifetimes of Tm I and 22 lifetimes of Tm II are reported for the first time. Good agreements between the present results and the previous experimental values were achieved for both Tm I and Tm II.

  20. Near-IR photoactivation using mesoporous silica-coated NaYF4:Yb,Er/Tm upconversion nanoparticles.

    PubMed

    Gnanasammandhan, Muthu Kumara; Idris, Niagara Muhammad; Bansal, Akshaya; Huang, Kai; Zhang, Yong

    2016-04-01

    Photoactivation is a process in which light is used to 'activate' photolabile therapeutics. As a therapeutic strategy, its advantages are that it is noninvasive and that a high degree of spatial and temporal control is possible. However, conventional photoactivation techniques are hampered by the limited penetration depth of the UV and visible lights to which the photosensitive compounds are responsive. Here we describe a protocol for the use of upconversion nanoparticles (UCNs) as light transducers to convert deeply penetrating near-infrared (NIR) light to UV-visible wavelengths matching that of the absorption spectrum of photosensitive therapeutics. This allows the use of deep-penetrating and biologically friendly NIR light instead of low-penetrating and/or toxic visible or UV lights for photoactivation. In this protocol, we focus on two photoactivation applications: photodynamic therapy (PDT) and photoactivated control of gene expression. We describe how to prepare and characterize the UCNs, as well as how to check their function in biochemical assays and in cells. For both applications, the UCNs are coated with mesoporous silica for easy loading of the therapeutics. For PDT, the UCNs are coated with polyethylene glycol (PEG) for stabilization and folic acid for tumor targeting and then loaded with photosensitizers that would be expected to kill cells by singlet oxygen production; the nanoparticles are injected intravenously. For photoactivated control of gene expression, knockdown of essential tumor genes is achieved using UCNs loaded with caged nucleic acids, which are injected intratumorally. The whole process from nanoparticle synthesis to animal studies takes ∼36 d. PMID:26963631

  1. Ultrasensitive polarized up-conversion of Tm(3+)-Yb3+ doped ?-NaYF4 single nanorod.

    PubMed

    Zhou, Jiajia; Chen, Gengxu; Wu, E; Bi, Gang; Wu, Botao; Teng, Yu; Zhou, Shifeng; Qiu, Jianrong

    2013-05-01

    Up-conversion luminescence in rare earth ions (REs) doped nanoparticles has attracted considerable research attention for the promising applications in solid-state lasers, three-dimensional displays, solar cells, biological imaging, and so forth. However, there have been no reports on REs doped nanoparticles to investigate their polarized energy transfer up-conversion, especially for single particle. Herein, the polarized energy transfer up-conversion from REs doped fluoride nanorods is demonstrated in a single particle spectroscopy mode for the first time. Unique luminescent phenomena, for example, sharp energy level split and singlet-to-triplet transitions at room temperature, multiple discrete luminescence intensity periodic variation with polarization direction, are observed upon excitation with 980 nm linearly polarized laser. Furthermore, nanorods with the controllable aspect ratio and symmetry are fabricated for analysis of the mechanism of polarization anisotropy. The comparative experiments suggest that intraions transition properties and crystal local symmetry dominate the polarization anisotropy, which is also confirmed by density functional theory calculations. Taking advantage of the REs based up-conversion, potential application in polarized microscopic multi-information transportation is suggested for the polarization anisotropy from REs doped fluoride single nanorod or nanorod array. PMID:23611309

  2. Interactions of CT DNA with hexagonal NaYF4 co-doped with Yb(3+)/Tm(3+) upconversion particles.

    PubMed

    Yuan, Xiuxue; Gu, Wenchao; Xiao, Mengsi; Xie, Wenli; Wei, Shaohua; Zhou, Lin; Zhou, Jiahong; Shen, Jian

    2015-02-25

    The interaction of UCPs with CT DNA are studied in detail by zeta potential, Energy dispersive spectrometer (EDS) spectroscopy, Thermogravimetric (TGA) analysis, DNA melting determination and various spectroscopic techniques including Ultraviolet-Visible (UV-Vis) absorption, fluorescence, circular dichroism (CD), Fourier transform infrared (FTIR) and Raman spectroscopy. The results indicate that CT DNA can assemble on the surface of UCPs mainly by relative stronger hydrophobic force and electrostatic binding, and the predominant interaction site is the deoxyribosyl phosphate backbone of CT DNA. Moreover, after interacting with UCPs, the double helix structure of DNA is undamaged. PMID:25305602

  3. Interactions of CT DNA with hexagonal NaYF4 co-doped with Yb3+/Tm3+ upconversion particles

    NASA Astrophysics Data System (ADS)

    Yuan, Xiuxue; Gu, Wenchao; Xiao, Mengsi; Xie, Wenli; Wei, Shaohua; Zhou, Lin; Zhou, Jiahong; Shen, Jian

    2015-02-01

    The interaction of UCPs with CT DNA are studied in detail by zeta potential, Energy dispersive spectrometer (EDS) spectroscopy, Thermogravimetric (TGA) analysis, DNA melting determination and various spectroscopic techniques including Ultraviolet-Visible (UV-Vis) absorption, fluorescence, circular dichroism (CD), Fourier transform infrared (FTIR) and Raman spectroscopy. The results indicate that CT DNA can assemble on the surface of UCPs mainly by relative stronger hydrophobic force and electrostatic binding, and the predominant interaction site is the deoxyribosyl phosphate backbone of CT DNA. Moreover, after interacting with UCPs, the double helix structure of DNA is undamaged.

  4. Determination of the 151Eu(n,γ)152Eu and 153Eu(n,γ)154Eu Reaction Cross Sections at Thermal Neutron Energy

    NASA Astrophysics Data System (ADS)

    Basunia, M. S.; Firestone, R. B.; Révay, Zs.; Choi, H. D.; Belgya, T.; Escher, J. E.; Hurst, A. M.; Krtička, M.; Szentmiklósi, L.; Sleaford, B.; Summers, N. C.

    2014-05-01

    We have measured partial γ-ray cross sections following neutron capture in enriched 151Eu and 153Eu targets at the cold-neutron-beam facility of the Budapest Research Reactor. The cross sections were standardized using a stoichiometric natEuCl3 target with the well-known 1951-keV γ-ray cross section from the 35Cl(n,γ)36Cl reaction at the cold-neutron-beam facility of the Garching Research Reactor. The γ-ray cross sections were corrected for effective g-factors. These data were combined with the structural information of 152Eu and 154Eu given in the Evaluated Nuclear Structure Data File to produce capture γ-ray level schemes. The total radiative capture cross sections of the 151Eu(n,γ)152Eu and 153Eu(n,γ)154Eu reactions were determined by summing the experimental transition intensities from known levels with simulated intensities of transitions from higher excitations to the ground- or metastable-state. The individual 151Eu(n,γ)152Eu and 151Eu(n,γ)152gEu reaction cross sections disagree with values in the literature. However, the total cross section of the 151Eu(n,γ)152Eu reaction does agree with those values. Also, our deduced cross section for the 153Eu(n,γ)154Eu reaction closely follows the data in the literature. These results are supported by an earlier standardization experiment done at the Budapest Research Reactor using a target of Eu2O3 solution in H2SO4.

  5. Use of Yb(III) Centered Near Infra-Red (NIR) Luminescence to Determine the Hydration State of a 3,2-HOPO based MRI-Contrast Agent

    SciTech Connect

    Moore, Evan G.; Seitz, Michael; Raymond, Kenneth N.

    2008-06-09

    It has been more than a decade since the first reports of [Gd(Tren-Me-3,2-HOPO)(H{sub 2}O){sub 2}] as a potential new class of magnetic resonance imaging contrast agent (MRI-CA). The defining feature of these 1-methyl-3-hydroxypyridin-2-one (Me-3,2-HOPO) based compounds has been the use of a hexadentate ligand design, and hence an increase in the number of metal bound water molecules, without sacrificing complex stability compared to the typically octadentate contrast agents used commercially. Since that time, significant advances in the properties of these chelates have been steadily reported, including improvements in relaxivity, incorporation into macromolecular architectures and, recently, the first direct verification of solution structure using the discovery of Eu(III) centered luminescence with the isomeric 1-hydroxypyridin-2-one (1,2-HOPO) chelate as a sensitizing chromophore. Nonetheless, it has remained frustrating that direct measurements of the inner sphere hydration state, q, using luminescence techniques with the parent Me-3,2-HOPO compounds have remained elusive, even when direct laser excitation of weakly absorbing f-f transitions were employed (eg. for Eu(III) complexes). This failing can likely be traced to the presence of a low lying LMCT state which efficiently quenches metal based emission. Instead, estimates of the q and hence solution structure have relied on the fitting of relaxivity data to the Solomon-Bloembergen-Morgan equations or, where sufficiently soluble in aqueous solution, studies on the temperature dependence of the paramagnetic contribution to the water {sup 17}O NMR transverse relaxation rate. Recently, Beeby et al reported on a qualitative equation to determine inner sphere hydration based on the change in lifetimes for Yb(III) in going from H{sub 2}O to D{sub 2}O solution, and we reasoned that the lower energy accepting state of Yb(III) may lie below the LMCT state which quenches Eu(III) emission, and hence may facilitate sensitized emission from Yb(III). This hypothesis was borne out experimentally, and herein we describe for the first time sensitized luminescence in the Near Infra-Red (NIR) region from a [Yb(Tren-Me-3,2-HOPO)(H{sub 2}O){sub 2}] complex, and hence the direct measurement of q for the archetypical member of this family of compounds.

  6. Reliability and Validity of the Zephyr[TM] BioHarness[TM] to Measure Respiratory Responses to Exercise

    ERIC Educational Resources Information Center

    Hailstone, Jono; Kilding, Andrew E.

    2011-01-01

    The Zephyr[TM] BioHarness[TM] (Zephyr Technology, Auckland, New Zealand) is a wireless physiological monitoring system that has the ability to measure respiratory rate unobtrusively. However, the ability of the BioHarness[TM] to accurately and reproducibly determine respiratory rate across a range of intensities is currently unknown. The aim of…

  7. Reliability and Validity of the Zephyr[TM] BioHarness[TM] to Measure Respiratory Responses to Exercise

    ERIC Educational Resources Information Center

    Hailstone, Jono; Kilding, Andrew E.

    2011-01-01

    The Zephyr[TM] BioHarness[TM] (Zephyr Technology, Auckland, New Zealand) is a wireless physiological monitoring system that has the ability to measure respiratory rate unobtrusively. However, the ability of the BioHarness[TM] to accurately and reproducibly determine respiratory rate across a range of intensities is currently unknown. The aim of

  8. EU Space Awareness: Initial implemenation

    NASA Astrophysics Data System (ADS)

    Russo, Pedro

    2015-08-01

    EU Space Awareness uses the excitement of space to attract young people into science and technology and stimulate European and global citizenship. The project will show children and teenagers the opportunities offered by space science and engineering and inspire primary-school children when their curiosity is high and their value systems are being formed. EU Space Awareness, a 3-year project, has started in March 2015 with 10 partner organisations and 15 network nodes in 17 European countries and the IAU Office of Astronomy for Development. During this talk we will give a update about the intial implementation of the project and its relevant for astronomy for development.

  9. Tertiary phosphine complexes of the f-block metals. Preparation of pentamethylcyclopentadienyl-tertiary phosphine complexes of ytterbium(II), ytterbium(III), and europium(II). Crystal structure of Yb(Me/sub 5/C/sub 5/)/sub 2/Cl(Me/sub 2/PCH/sub 2/PMe/sub 2/)

    SciTech Connect

    Tilley, T.D.; Andersen, R.A.; Zalkin, A.

    1983-03-16

    The diphosphine, Me/sub 2/PCH/sub 2/CH/sub 2/PMe/sub 2/, reacts with M(Me/sub 5/C/sub 5/)/sub 2/(OEt/sub 2/) to give insoluble M(Me/sub 5/C/sub 5/)/sub 2/(Me/sub 2/PCH/sub 2/CH/sub 2/PMe/sub 2/), where M is Eu or Yb. In contrast, Me/sub 2/PCH/sub 2/PMe/sub 2/ gives the hydrocarbon-soluble complexes M(Me/sub 5/C/sub 5/)/sub 2/(Me/sub 2/PCH/sub 2/PMe/sub 2/), where M is Eu or Yb. The ytterbium complex reacts with YbCl/sub 3/ in toluene to give Yb(Me/sub 5/C/sub 5/)/sub 2/Cl(Me/sub 2/PCH/sub 2/PMe/sub 2/), and the crystal structure shows that the phosphine is acting as a monodentate ligand. Yb(Me/sub 5/C/sub 5/)/sub 2/Cl(Me/sub 2/PCH/sub 2/PMe/sub 2/) crystallizes in the monoclinic space group P2/sub 1//c with a = 16.358 (6) A, b = 8.595 (4) A, c - 20.712 (7) A, ..beta.. = 104.75 (4)/sup 0/, V = 2816 A/sup 3/, and d(calcd) = 1.45 g cm/sup -3/ for Z = 4 and mol wt = 615.15. Diffraction data were collected with a CAD-4 automated diffractometer, and the structure was refined to R = 0.054 for 3309 reflections with 4/sup 0/ < 2theta < 45/sup 0/ (Mo K..cap alpha.. radiation). The Yb is coordinated to the two Me/sub 5/C/sub 5/ groups, to the chlorine atom, and to one phosphorus atom of the bis(dimethylphosphino)methane ligand. The Yb-P and Yb-Cl distances are 2.94 and 2.53 A, respectively. The centroids of the C/sub 5/Me/sub 5/ ligands and the Cl and P atoms are in an approximate tetrahedral arrangement about the Yb atom.

  10. Sequential growth of sandwiched NaYF4:Yb/Er@NaYF4:Yb@NaNdF4:Yb core-shell-shell nanoparticles for photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Peng, Huang-Yong; Ding, Bin-Bin; Ma, Yin-Chu; Sun, Shi-Qi; Tao, Wei; Guo, Yan-Chuan; Guo, Hui-Chen; Yang, Xian-Zhu; Qian, Hai-Sheng

    2015-12-01

    Upconversion (UC) nanostructures have attracted much interest for their extensive biological applications. In this work, we describe a sequential synthetic route to prepare sandwiched NaYF4:Yb/Er@NaYF4:Yb@NaNdF4:Yb core-shell upconversion nanoparticles. The as-prepared products were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM, JEM 2100F), respectively. The as-prepared core-shell nanoparticles of NaYF4:Yb/Er@NaYF4:Yb@NaNdF4:Yb are composed of elliptical nanoparticles with a length of 80 nm and width of 42 nm, which show efficient upconversion fluorescence excited at 808 nm indicating the formation of core-shell-shell sandwiched nanostructures. In addition, the as-prepared sandwiched NaYF4:Yb/Er@NaYF4:Yb@NaNdF4:Yb core-shell upconversion nanoparticles also show strong upconversion fluorescence excited at 980 nm. Amphiphilic mPEG2k-b-PEBEP6K copolymers (denoted as PPE) were chosen to transfer these hydrophobic UCNPs into the aqueous phase for biological application. In vitro photodynamic therapy of cancer cells show that the viability of cells incubated with the nanoparticles loaded with MC 540 was significantly lower as compared to the nanoparticles without photosensitizers exposed to NIR laser.

  11. Preparation and characterization of Yb-doped YAG ceramics

    NASA Astrophysics Data System (ADS)

    Hostaa, Jan; Esposito, Laura; Alderighi, Daniele; Pirri, Angela

    2013-02-01

    This work presents the results of the preparation of polycrystalline Yb:YAG ceramics for laser sources with dopant concentration from 0 up to 20 at.% via solid state reactive sintering. Samples were prepared via cold isostatic pressing of spray dried mixture of pure oxide powders with TEOS as a sintering aid. Sintering was conducted under high vacuum and clean atmosphere. Various sintering cycles were tested, so that optimum conditions could be selected in dependence on Yb concentration. Samples with optical transmittance higher than 80% were prepared and their laser performance was examined. Slope efficiency as high as 73% and a maximum output power of 6 W were obtained for the sample doped with 10% Yb. Final microstructure of prepared samples was analyzed via optical microscopy, scanning and transmission electron microscopy, and EDS.

  12. Yb:YAG Lasers for Space Based Remote Sensing

    NASA Technical Reports Server (NTRS)

    Ewing, J.J.; Fan, T. Y.

    1998-01-01

    Diode pumped solid state lasers will play a prominent role in future remote sensing missions because of their intrinsic high efficiency and low mass. Applications including altimetry, cloud and aerosol measurement, wind velocity measurement by both coherent and incoherent methods, and species measurements, with appropriate frequency converters, all will benefit from a diode pumped primary laser. To date the "gold standard" diode pumped Nd laser has been the laser of choice for most of these concepts. This paper discusses an alternate 1 micron laser, the YB:YAG laser, and its potential relevance for lidar applications. Conceptual design analysis and, to the extent possible at the time of the conference, preliminary experimental data on the performance of a bread board YB:YAG oscillator will be presented. The paper centers on application of YB:YAG for altimetry, but extension to other applications will be discussed.

  13. TE/TM decomposition of electromagnetic sources

    NASA Technical Reports Server (NTRS)

    Lindell, Ismo V.

    1988-01-01

    Three methods are given by which bounded EM sources can be decomposed into two parts radiating transverse electric (TE) and transverse magnetic (TM) fields with respect to a given constant direction in space. The theory applies source equivalence and nonradiating source concepts, which lead to decomposition methods based on a recursive formula or two differential equations for the determination of the TE and TM components of the original source. Decompositions for a dipole in terms of point, line, and plane sources are studied in detail. The planar decomposition is seen to match to an earlier result given by Clemmow (1963). As an application of the point decomposition method, it is demonstrated that the general exact image expression for the Sommerfeld half-space problem, previously derived through heuristic reasoning, can be more straightforwardly obtained through the present decomposition method.

  14. Identification and characterization of NF-YB family genes in tung tree.

    PubMed

    Yang, Susu; Wang, Yangdong; Yin, Hengfu; Guo, Haobo; Gao, Ming; Zhu, Huiping; Chen, Yicun

    2015-12-01

    The NF-YB transcription factor gene family encodes a subunit of the CCAAT box-binding factor (CBF), a highly conserved trimeric activator that strongly binds to the CCAAT box promoter element. Studies on model plants have shown that NF-YB proteins participate in important developmental and physiological processes, but little is known about NF-YB proteins in trees. Here, we identified seven NF-YB transcription factor-encoding genes in Vernicia fordii, an important oilseed tree in China. A phylogenetic analysis separated the genes into two groups; non-LEC1 type (VfNF-YB1, 5, 7, 9, 11, 13) and LEC1-type (VfNF-YB 14). A gene structure analysis showed that VfNF-YB 5 has three introns and the other genes have no introns. The seven VfNF-YB sequences contain highly conserved domains, a disordered region at the N terminus, and two long helix structures at the C terminus. Phylogenetic analyses showed that VfNF-YB family genes are highly homologous to GmNF-YB genes, and many of them are closely related to functionally characterized NF-YBs. In expression analyses of various tissues (root, stem, leaf, and kernel) and the root during pathogen infection, VfNF-YB1, 5, and 11 were dominantly expressed in kernels, and VfNF-YB7 and 9 were expressed only in the root. Different VfNF-YB family genes showed different responses to pathogen infection, suggesting that they play different roles in the pathogen response. Together, these findings represent the first extensive evaluation of the NF-YB family in tung tree and provide a foundation for dissecting the functions of VfNF-YB genes in seed development, stress adaption, fatty acid synthesis, and pathogen response. PMID:26037219

  15. Evaluating LANDSAT-4 MSS and TM data

    NASA Technical Reports Server (NTRS)

    Strome, W. M.; Cihlar, J.; Goodenough, D. G.; Guertin, F. E. (principal investigator); Murphy, J. M.; Grieve, G.; Simard, R.; Horler, D.; Ahern, F. J.

    1984-01-01

    Interband line pixel misregistrations were determined for the four MSS bands of the Mistassini, Ontario scene and multitemporal registration of LANDSAT-4 products were tested for two different geocoded scenes. Line and pixel misregistrations are tabulated as determined by the manual ground control points and the digital band to band correlation techniques. A method was developed for determining the spectral information content of TM images for forestry applications.

  16. Magnetic ordering and hybridisation in YbAuCu{4}

    NASA Astrophysics Data System (ADS)

    Bonville, P.; Canaud, B.; Hammann, J.; Hodges, J. A.; Imbert, P.; Jhanno, G.; Severing, A.; Fisk, Z.

    1992-04-01

    We report on a ^{170}Yb Mssabauer spectroscopy investigation of the low temperature magnetic properties of the cubic heavy electron material YbAuCu4. In the antiferromagnetically ordered phase (T_N=1 K), we measure a 20 % reduction of the Yb^{+3} saturated spontaneous moment with respect to that of the crystal field ?_7 ground state and we evidence a sizeable anisotropy of the interionic magnetic interaction. We interpret these features in terms of 4f electron - conduction electron hybridisation, which accounts for the heavy electron properties. The energy scale k_BT_0 of hybridisation is estimated to be 0.3 K. The Mssbauer spectra in the ordered and paramagnetic phases show inhomogeneous line broadenings which are interpreted as arising from a distribution of local strains along the <~ngle111rangle crystal axes, of mean magneto-elastic energy 0.2 0.4 K. Nous prsentons une tude par spectroscopie Mssbauer sur ^{170}Yb des proprits basse temprature du compos cubique lectrons lourds YbAuCu4. Dans la phase antiferromagntique (T_N=1 K), nous mesurons une rduction de 20 % du moment spontan saturation de Yb^{+3} par rapport au moment de l'tat fondamental ?_7 de champ cristallin, et nous mettons en vidence une anisotropie notable de l'interaction magntique entre les ions. Nous interprtons ce comportement en termes d'hybridation entre les lectrons 4f et les lectrons de conduction, qui rend compte des proprits de type lectron lourd. L'chelle d'nergie k_BT_0 de l'hybridation est estime de l'ordre de 0,3 K. Les spectres Mssbauer dans les phases ordonne et paramagntique prsentent des largissements de raie inhomognes qui sont interprts en termes de distribution de contraintes locales suivant les axes <111> du cristal, d'nergie magnto-lastique moyenne 0,2 0,4 K.

  17. Thermal analysis on grad-doped active-mirror Yb:YAG ceramic lasers

    NASA Astrophysics Data System (ADS)

    Cheng, Xiaojin; Wang, Jianlei; Jiang, Benxue

    2015-11-01

    Heat conduction, temperature distribution, thermal stress, and thermally induced refractive index of a diode-pumped active-mirror grad-doped Yb:YAG ceramic laser are analyzed and compared to a uniform-doped Yb:YAG ceramic laser. It is found that a rationally designed grad-doped Yb:YAG ceramic has a smaller temperature gradient than a uniform-doped Yb:YAG ceramic with the same absorption pump power, which results in higher output energy in the grad-doped Yb:YAG ceramic laser.

  18. Absolute calibration accuracy of L4 TM and L5 TM sensor image pairs

    USGS Publications Warehouse

    Chander, G.; Micijevic, E.

    2006-01-01

    The Landsat suite of satellites has collected the longest continuous archive of multispectral data of any land-observing space program. From the Landsat program's inception in 1972 to the present, the Earth science user community has benefited from a historical record of remotely sensed data. However, little attention has been paid to ensuring that the data are calibrated and comparable from mission to mission, Launched in 1982 and 1984 respectively, the Landsat 4 (L4) and Landsat 5 (L5) Thematic Mappers (TM) are the backbone of an extensive archive of moderate resolution Earth imagery. To evaluate the "current" absolute accuracy of these two sensors, image pairs from the L5 TM and L4 TM sensors were compared. The approach involves comparing image statistics derived from large common areas observed eight days apart by the two sensors. The average percent differences in reflectance estimates obtained from the L4 TM agree with those from the L5 TM to within 15 percent. Additional work to characterize the absolute differences between the two sensors over the entire mission is in progress.

  19. High pressure synthesis of a new phase of YbAg2: Structure, valence of Yb and properties

    DOE PAGESBeta

    Tsvyashchenko, A. V.; Menushenkov, A. P.; Sidorov, V. A.; Petrova, A. E.; Fomicheva, L. N.; Chernysheva, O. V.; Lebed, Yu. B.; Axenov, S. N.; Bud’ko, S. L.; Sun, Liling; et al

    2015-08-05

    The new phase of YbAg2 was obtained using high-pressure and high-temperature reaction. YbAg2 crystallizes in the MgZn2 structure (the space group P63/mmc space group, No 194) with a = 5.68153(3) Å and c = 9.31995(7) Å and the unit cell volume V = 260.54(3) Å3. The XANES analysis showed that the valence state of Yb is +2.8. The low-temperature dependences of the electrical resistivity and magnetic susceptibility can be adequately described by a T2 term that supports the Fermi-liquid picture. Furthermore, the Kadowaki–Woods relation gives a low value of the degeneracy (N = 2).

  20. High pressure synthesis of a new phase of YbAg2: Structure, valence of Yb and properties

    SciTech Connect

    Tsvyashchenko, A. V.; Menushenkov, A. P.; Sidorov, V. A.; Petrova, A. E.; Fomicheva, L. N.; Chernysheva, O. V.; Lebed, Yu. B.; Axenov, S. N.; Bud’ko, S. L.; Sun, Liling; Zhao, Zhongxian

    2015-08-05

    The new phase of YbAg2 was obtained using high-pressure and high-temperature reaction. YbAg2 crystallizes in the MgZn2 structure (the space group P63/mmc space group, No 194) with a = 5.68153(3) Å and c = 9.31995(7) Å and the unit cell volume V = 260.54(3) Å3. The XANES analysis showed that the valence state of Yb is +2.8. The low-temperature dependences of the electrical resistivity and magnetic susceptibility can be adequately described by a T2 term that supports the Fermi-liquid picture. Furthermore, the Kadowaki–Woods relation gives a low value of the degeneracy (N = 2).

  1. Measurement of thermal neutron cross-section and resonance integral for the 174Yb(n,γ) 175Yb reaction by the cadmium ratio method

    NASA Astrophysics Data System (ADS)

    Karadag, Mustafa; Yücel, Haluk

    2008-06-01

    The thermal-neutron cross-section and the resonance integral for the 174Yb(n,γ)175Yb reaction were measured by the activation method using a 55Mn monitor as single comparator. Analytical grade MnO2 and Yb2O3 powder samples with and without a cylindrical 1 mm Cd shield box were irradiated in an isotropic neutron field obtained from three 241Am-Be neutron sources. The gamma-ray spectra from the activated samples were measured with a calibrated n-type high-purity Ge detector. The experimental results were corrected for the correction factors calculated for thermal and epithermal neutron self-shielding effects, epithermal neutron spectrum shape and gamma-ray self attenuation. Thus, the thermal neutron cross-section for the 174Yb(n,γ)175Yb reaction is found to be 126.5 ± 6.6 b, relative to that of the 55Mn monitor. The resonance integral value for the 174Yb(n,γ)175Yb reaction is found to be 59.6 ± 8.5 b, at cadmium cut-off energy of a 0.55 eV. Using the measured cadmium ratios of 55Mn and 174Yb, the result for resonance integral of the 174Yb(n,γ)175Yb reaction has also been obtained relative to the reference value of the 55Mn monitor. The present results for the 174Yb(n,γ)175Yb reaction agree well only with the recent experimental ones obtained by Kafala et al. [1] and De Corte and Simonits [2] within uncertainty limits. However, the previously reported experimental data for the thermal neutron cross-section for this reaction are distributed between 24 and 141 b, and similarly the experimental values for the resonance integral value also show a large scatter in the range of 30-69 b.

  2. The polygallides: Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub2}.

    SciTech Connect

    Peter, S. C.; Malliakas, C. D.; Nakotte, H.; Kothapilli, K.; Rayaprol, S.; Schultz, A. J.; Kanatzidis, M. G.

    2012-03-01

    Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} were obtained from reactions of Yb and Ge in excess liquid gallium. The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was refined using X-ray and neutron diffraction data on selected single crystals. Yb{sub 3}Ga{sub 7}Ge{sub 3} crystallizes in the monoclinic space group C2/c with lattice constants a = 12.2261(20) {angstrom}, b = 10.7447(20) {angstrom}, c = 8.4754(17) {angstrom} and {beta} = 110.288(30){sup o} (neutron diffraction data). The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} is an intergrowth of planar layers of YbGa{sub x}Ge{sub y} and puckered layers of (Ge)n. YbGa{sub 4}Ge{sub 2} crystallizes in a modified PuGa{sub 6} structure type in the tetragonal polar space group I4cm with lattice constants a = b = 5.9874(6) {angstrom} and c = 15.1178(19) {angstrom}. The structure of YbGa{sub 4}Ge{sub 2} is an intergrowth of puckered Ga layers and puckered Ga{sub x}Ge{sub y} layers with Yb atoms residing within the channels formed by the connection of the two layers. Physical properties, resistivity ({rho}), magnetic susceptibility ({chi}) and specific heat (C) were measured for Yb{sub 3}Ga{sub 7}Ge{sub 3}. No magnetic ordering was observed. It was found that at low temperatures, {rho} varied as T{sup 2} and C{alpha}T, indicating Fermi-liquid regime in Yb{sub 3}Ga{sub 7}Ge{sub 3} at low temperatures.

  3. NMR, high frequency EPR and magnetization studies of YF3:Tm3+ and TmF3

    NASA Astrophysics Data System (ADS)

    Savinkov, A. V.; Shakurov, G. S.; Korableva, S. L.; Dooglav, A. V.; Tagirov, M. S.; Suzuki, H.; Matsumoto, K.; Abe, S.

    2011-10-01

    Magnetic properties of single crystal and powder samples of thulium fluoride, TmF3 (orthorhombic Pnma space group), and single crystals of YF3 doped with the Tm3+ ions are studied by NMR, high-frequency EPR and dc-magnetometry. It is shown that TmF3 is a Van Vleck paramagnet. Zero field splitting between two lowest ground state energy levels (ground 3H6 multiplet) of Tm3+ ion in TmF3 crystal lattice is found to be ~6.5 cm-1. The 19F nuclear spin-lattice relaxation in TmF3 at liquid helium temperatures is driven by the fluctuating magnetic fields created by Tm3+ ions occupying the lowest excited singlet.

  4. Comparative study of optical and scintillation properties of Tm3+:YAG, and Tm3+:LuAG single crystals

    NASA Astrophysics Data System (ADS)

    Fujimoto, Yutaka; Sugiyama, Makoto; Yanagida, Takayuki; Wakahara, Shingo; Suzuki, Shotaro; Kurosawa, Shunsuke; Chani, Valery; Yoshikawa, Akira

    2013-09-01

    The optical and scintillation properties of Tm3+-doped yttrium aluminum garnet Y3Al5O12 (YAG) and Tm3+-doped lutetium aluminum garnet Lu3Al5O12 (LuAG) are compared. The Tm3+-doped single crystals were grown by the micro-pulling down (?-PD) technique. Both crystals demonstrated some emission peaks originated from 4f-4f forbidden transition of Tm3+ under 241Am alpha-ray excitation. The scintillation decay time of Tm3+-doped YAG was similar to that of LuAG. When irradiated by the gamma-rays from a 137Cs source, the relative scintillation light yields of Tm:YAG was 90% greater than that of Tm:LuAG.

  5. Thermoelectric properties of Yb-filled CoSb3 skutterudites

    NASA Astrophysics Data System (ADS)

    Park, Kwan-Ho; Seo, Won-Seon; Shin, Dong-Kil; Kim, Il-Ho

    2014-08-01

    Yb-filled skutterudites Yb z Co4Sb12 (z = 0, 0.1, 0.2, 0.3, 0.4) were prepared by encapsulated melting and hot pressing. The filling effects of Yb on the transport and the thermoelectric properties of the skutterudites were examined. In the case of z ? 0.3, a secondary phase (YbSb2) was formed, indicating that the filling fraction limit of Yb was z = 0.2 - 0.3. The intrinsic CoSb3 had a high positive Seebeck coefficient, but Yb-filled CoSb3 exhibited a negative Seebeck coefficient. In the case of z ? 0.1, the maximum absolute value of the Seebeck coefficient was | -231| ?VK-1, and in the case of z ? 0.2, the absolute value of the Seebeck coefficient increased with increasing temperature. The electrical conductivity increased and the Seebeck coefficient decreased with increasing Yb filling content due to the increased carrier concentration. The thermal conductivity was reduced significantly by Yb filling, mainly due to a decrease in the lattice thermal conductivity. Also, the lattice thermal conductivity decreased with increasing Yb filling content, indicating that the phonon scattering was caused by the rattling of Yb fillers in the voids of the skutterudite structure. Yb0.2Co4Sb12 showed the highest figure of merit of 1.0 at 823 K.

  6. High pulse energy multiwatt Yb:CaAlGdO4 and Yb:CaF2 regenerative amplifiers.

    PubMed

    Caracciolo, E; Kemnitzer, M; Guandalini, A; Pirzio, F; Agnesi, A; Aus der Au, J

    2014-08-25

    We investigated and compared Yb:CaAlGdO4 and Yb:CaF2 regenerative amplifiers at repetition rates 5-10 kHz, a frequency range interesting for industrial applications requiring relatively high pulse energy. Both materials allow for pulse energies close to 1 mJ with sub-400-fs pulses. The two laser materials offer comparable performance in the pump power range investigated. The same regenerative amplifiers can be run up to 500 kHz for much faster material processing, with maximum output power of up to 9.4 W. PMID:25321201

  7. Growth of Yb: S-FAP [Yb 3+:Sr 5(PO 4) 3F] crystals for the Mercury laser

    NASA Astrophysics Data System (ADS)

    Schaffers, K. I.; Tassano, J. B.; Bayramian, A. B.; Morris, R. C.

    2003-06-01

    Crystals of Yb:S-FAP [Yb 3+:Sr 5(PO 4) 3F] will be used as the gain medium for the Mercury Laser, a gas-cooled amplifier system intended to yield 100 J, 10 Hz and 10% efficiency in 3 ns when completed, for inertial fusion energy. Growing high optical quality crystals is a challenge due to a number of growth issues, including: cloudiness, bubble core defects, anomalous absorption, low-angle grain boundaries, cracking, and crystal inclusions. At this time, a growth process has been developed to simultaneously eliminate or diminish each of the defects.

  8. Laser brackets debonding: Tm:YAP and ClarityTM SL self-ligating appliance system

    NASA Astrophysics Data System (ADS)

    Dostálová, Tatjana; Jelínková, Helena; Šulc, Jan; Koranda, Petr; Němec, Michal; Jelínek, Michal; Fibrich, Martin; Michalik, Pavel; Miyagi, Mitsunobu

    2010-02-01

    The study demonstrates the possibility of using Tm:YAP laser radiation for the removing ceramic brackets. The amount of enamel loss and residual resin on teeth has been evaluated. A diode-pumped Tm:YAP microchip laser generating at wavelength 1.9 μm was used for the debonding process. The transmission and absorption measurement of the basic elements - bracket, adhesive resin, and enamel was analyzed to explain the source of the heat and bracket debonding. Quantitative measurements are made for visualizing enamel surface before and after a self-ligating bonding technique. Temperature rise observation during the debonding procedure - from 0.5 to 2 W power - has improved the accuracy of assessment. The results were evaluated by CCD camera and scanning electron microscope. From the measurements it is possible to conclude that continuously running small diode pumped Tm:YAP microchip laser having output power 1W can remove the ceramic bracket without enamel iatrogenic damage.

  9. Fiber amplifiers and lasers in Yb:silica

    SciTech Connect

    Wilcox, R.B.; Browning, D.F.; Feit, M.D.; Nyman, B.

    1996-11-15

    We have measured gain and saturation in sing;e mode Yb:silica fiber, and developed fiber lasers and amplifiers at 1053 nm. The lasers are tunable over 10`s of nanometers, with amplifier gain flattened by fiber gratings or dielectric filters.

  10. Ionizing radiation detection by Yb-doped silica optical fibers

    NASA Astrophysics Data System (ADS)

    De Mattia, Cristina; Veronese, Ivan; Fasoli, Mauro; Chiodini, Norberto; Mones, Eleonora; Cantone, Marie Claire; Cialdi, Simone; Gargano, Marco; Ludwig, Nicola; Bonizzoni, Letizia; Vedda, Anna

    2015-08-01

    Rare earths-doped silica optical fibers have shown promising results for ionizing radiation monitoring, thanks to their radio-luminescence (RL) properties. However, the use of these systems for accurate and precise dosimetric measurements in radiation fields above the Cerenkov energy threshold, like those employed in radiation therapy, is still challenging, since a spurious luminescence, namely the "stem effect," is also generated in the passive fiber portion exposed to radiation. The spurious signal mainly occurs in the UV-VIS region, therefore a dopant emitting in the near infrared may be suitable for an optical discrimination of the stem effect. In this work, the RL and dosimetric properties of Yb-doped silica optical fibers, produced by sol-gel technique, are studied, together with the methods and instruments to achieve an efficient optical detection of the Yb3+ emission, characterized by a sharp line at about 975 nm. The results demonstrate that the RL of Yb3+ is free from any spectral superposition with the spurious luminescence. This aspect, in addition with the suitable linearity, reproducibility, and sensitivity properties of the Yb-doped fibers, paves the way to their use in applications where an efficient stem effect removal is required.

  11. Unusual Yb magnetic properties in YbMn6Ge1.8-xSn4.2Gax and YbMn6Ge1.8Sn4.2-yGay

    NASA Astrophysics Data System (ADS)

    Eichenberger, L.; Malaman, B.; Mazet, T.

    2016-05-01

    We investigate the magnetic properties of the new HfFe6Ge6-type (P6/mmm) YbMn6Ge1.8-xSn4.2Gax (x=0.05, 0.4 and 0.9) and YbMn6Ge1.8Sn4.2-yGay (y=0.05, 0.5 and 1.0) alloys from DC magnetization and powder neutron diffraction experiments. The electronic structure modifications induced by the Ga substitution are found to promote the ferromagnetic order of the Mn sublattice, to enhance the Yb ordering temperature (up to TYb?170 K) and to strongly increase the low-temperature coercive field (up to ?0Hc?1 T). By contrast, the changes in the Yb magnetic moment magnitude upon Ga substitution are analyzed to be mainly driven by chemical pressure effects. The reduced Yb magnetic moment (1.0 ?BYb<1.8 ?B) compared with the free ion value (4 ?B) is interpreted as resulting from Kondo screening. There are strong indirect indications that the high temperature Yb magnetic ordering likely involves intermediate valent Yb.

  12. Gibbs energy of formation of Cu{sub 2}Yb{sub 2}O{sub 5} and thermodynamic stability of Cu{sub 2}R{sub 2}O{sub 5} (R = Tb-Lu)

    SciTech Connect

    Kale, G.M.

    1996-08-01

    The electromotive force (emf) of the solid oxide electrochemical cell, (-)Pt/Cu{sub 2}O + Yb{sub 2}O{sub 3} + Cu{sub 2}Yb{sub 2}O{sub 5}//(CaO)ZrO{sub 2}//O{sub 2}(P = 0.0212 MPa)/Pt(+), has been measured between 960 and 1320 K. Based on the measured emf of the above cell as a function of temperature, the Gibbs energy change for the reaction 2Cu{sub 2}O(s) + 2Yb{sub 2}O{sub 3}(s) + O{sub 2}(g) {yields} 2Cu{sub 2}Yb{sub 2}O{sub 5}(s) is obtained as {Delta}G{degrees} = {minus}231,225 + 151.847T ({plus_minus}200) J mol{sup {minus}1}. The Gibbs energy change for the above reaction when combined with that for Cu{sub 2}O + CuO equilibrium from the literature gives, for the reaction 2CuO(s) + Yb{sub 2}O{sub 3}(s) + Yb{sub 2}O{sub 3}(s) {yields} Cu{sub 2}Yb{sub 2}O{sub 5}(s), {Delta}G{degrees} = 17,128 {minus} 20.07T ({plus_minus}100) J mol{sup {minus}1}. It can be seen that the formation of Cu{sub 2}Yb{sub 2}O{sub 5} from the component oxides is endothermic. Since Cu{sub 2}Yb{sub 2}O{sub 5} is an entropy stabilized compound and its formation is endothermic from component oxides, Cu{sub 2}Yb{sub 2}O{sub 5} is thermodynamically unstable relative to its component oxides below 853 K. Earlier we reported the Gibbs energy of formation of Cu{sub 2}Dy{sub 2}O{sub 5}, Cu{sub 2}Ho{sub 2}O{sub 5}, and Cu{sub 2}Er{sub 2}O{sub 5} from CuO and R{sub 2}O{sub 3}(R = Dy, Ho, Er). Since Cu{sub 2}Yb{sub 2}O{sub 5} is also a member of the Cu{sub 2}R{sub 2}O{sub 5} family of compounds whose crystal structure belongs to a noncentrosymmetric space group P2{sub 1}nb, an attempt has been made to correlate their thermodynamic properties such as enthalpy and entropy of formation with the ionic radius of the trivalent rare-earth cation present in octahedral coordination. Based on this correlation, {Delta}H, {Delta}S, and {Delta}G for the formation of Cu{sub 2}Tb{sub 2}O{sub 5}, Cu{sub 2}Tm{sub 2}O{sub 5}, and Cu{sub 2}Lu{sub 2}O{sub 5} from the component oxides have been estimated.

  13. TE/TM Simulations of Interferometric Measurements

    NASA Technical Reports Server (NTRS)

    Houshmand, Bijan

    2000-01-01

    Interferometric synthetic aperture radar (IFSAR) measurements at X-, C-, L-, and P-band are used to derive ground topography at meter level resolution. Interpretation of the derived topography requires attention due to the complex interaction of the radar signal with ground cover. The presence of penetrable surfaces such as vegetation, and tree canopies poses a challenge since the depth of penetration depends on a number of parameters such as the operating radar frequency, polarization, incident angle, as well as terrain structure. The dependence of the reconstructed topography on polarization may lead to the characterization of the ground cover. Simulation of interferometric measurements is useful for interpretation of the derived topography (B. Houshmand, Proceedings of URSI, 314, 1997). In this talk , time domain simulations for interferometric measurement for TE- and TM- polarization are presented. Time domain simulation includes the effects of the surface material property as well geometry comparable the radar signal wavelength (B. Houshmand, Proceedings of the URSI, 25, 1998). The IFSAR simulation is carried out in two steps. First, the forward scattering data is generated based on full wave analysis. Next, the electromagnetic information is inverted to generate surface topography. This inversion is based on the well known IFSAR processing technique which is composed of signal compression, and formation of an interferogram. The full wave forward scattering data is generated by the scattered-field formulation of the FDTD algorithm. The simulation is carried out by exciting the computational domain by a radar signal. The scattered field is then computed and translated to the receiving interferometric antennas using the time-domain Huygen's principle. The inversion process starts by compressing the time-domain data. The range compressed data from both receivers are then coregistered to form an interferogram. The resulting interferogram is then related to the ground topography using the radar imaging geometry. In this talk, the simulation results are compared with the C-band TM IFSAR derived topography, and the TE/TM SAR images at L-Band.

  14. Strong Eu2+ light emission in Eu silicate through Eu3+ reduction in Eu2O3/Si multilayer deposited on Si substrates

    PubMed Central

    2013-01-01

    Eu2O3/Si multilayer nanostructured films are deposited on Si substrates by magnetron sputtering. Transmission electron microscopy and X-ray diffraction measurements demonstrate that multicrystalline Eu silicate is homogeneously distributed in the film after high-temperature treatment in N2. The Eu2+ silicate is formed by the reaction of Eu2O3 and Si layers, showing an intense and broad room-temperature photoluminescence peak centered at 610 nm. It is found that the Si layer thickness in nanostructures has great influence on Eu ion optical behavior by forming different Eu silicate crystalline phases. These findings open a promising way to prepare efficient Eu2+ materials for photonic application. PMID:23618344

  15. Nanocrystallization in Yb3+-doped oxyfluoride glasses for laser cooling

    NASA Astrophysics Data System (ADS)

    Kummara, Venkata Krishaniah; Ledemi, Yannick; Soares de Lima Filho, Elton; Messaddeq, Younes; Kashyap, Raman

    2015-03-01

    Glass-ceramics are composite materials consisting of crystals which are controllably grown within a glass matrix usually by applying an appropriate heat treatment. They possess outstanding optical properties with applications in solid state lasers, optical amplifiers, and now, laser induced cooling. For laser cooling, the material should exhibit specific properties like low phonon energy environment around the lanthanide ions, low background losses, high transparency and high photoluminescence quantum yield. In the present study, oxyfluoride glasses and ultra-transparent nano glassceramics doped with different concentrations (2, 5, 8, 12, 16 and 20 mol %) of Yb 3+ ions have been prepared by conventional melt-quenching and subsequent thermal treatments at different temperatures, respectively. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements have been performed to characterize the thermal properties of the glass and the structural changes in the glass-ceramics, respectively. The XRD patterns confirm the growth of β-PbF2 nanocrystals as well as progressive incorporation of Yb 3+ ions. This enhances the Yb 3+ ion emission intensity which depends on the doping concentration and ceramization temperatures. The size (20 nm) of the nanocrystallites was estimated from the Sherrer's formula and found to increase with increasing ceramization temperature, small enough to avoid scattering losses and ensure an excellent transparency of the glass-ceramics comparable with that of the parent glass. An enhancement of the luminescence properties of Yb 3+ ions surrounded by a crystalline low phonon environment is observed. Finally, the utilization of these heavily Yb 3+-doped ultra-transparent materials for laser cooling and solid state laser applications is discussed.

  16. Post-adsorption process of Yb phosphate nano-particle formation by Saccharomyces cerevisiae

    NASA Astrophysics Data System (ADS)

    Jiang, MingYu; Ohnuki, Toshihiko; Tanaka, Kazuya; Kozai, Naofumi; Kamiishi, Eigo; Utsunomiya, Satoshi

    2012-09-01

    In this study, we have investigated the post-adsorption process of ytterbium (Yb) phosphate nano-particle formation by Saccharomyces cerevisiae (yeast). The yeast grown in P-rich medium were exposed to 1.44 10-4 mol/L Yb(III) solution for 2-120 h, and 2 months at 25 1 C at an initial pH of 3, 4, or 5, respectively. Ytterbium concentrations in solutions decreased as a function of exposure time. Field-emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (FESEM), transmission electron microscopy (TEM), and synchrotron-based extended X-ray absorption fine structure (EXAFS) analyses revealed that nano-sized blocky Yb phosphate with an amorphous phase formed on the yeast cells surfaces in the solutions with Yb. These nano-sized precipitates that formed on the cell surfaces remained stable even after 2 months of exposure at 25 1 C around neutral pHs. The EXAFS data revealed that the chemical state of the accumulated Yb on the cell surfaces changed from the adsorption on both phosphate and carboxyl sites at 30 min to Yb phosphate precipitates at 5 days, indicating the Yb-phosphate precipitation as a major post-adsorption process. In addition, the precipitation of Yb phosphate occurred on cell surfaces during 7 days of exposure in Yb-free solution after 2 h of exposure (short-term Yb adsorption) in Yb solution. These results suggest that the released P from the inside of yeast cells reacted with adsorbed Yb on cell surfaces, resulting in the formation of Yb precipitates, even though no P was added to the exposure solution. In an abiotic system, the EXAFS data showed that the speciation of sorbed Yb on the reference materials, carboxymethyl cellulose and Ln resin, did not change even when the Yb was exposed to P solution, without forming Yb phosphate precipitates. This result strongly suggests that the cell surface of the yeast plays an important role in the Yb-phosphate precipitation process, not only as a carrier of the functional groups but also as a substrate inducing the nucleation of phosphate nanoparticles. Stable nano-sized Yb phosphate precipitates formed on yeast cell surfaces in the present study, which implies that this post-adsorption nano-particle formation process caused by microbial cells should be one of the important processes governing the long-term migration of heavy rare earth elements and presumably trivalent actinides in geological repository.

  17. Optical Properties of Tm(3+) Ions in Alkali Germanate Glass

    NASA Technical Reports Server (NTRS)

    Walsh, Brian M.; Barnes, Norman P.; Reichle, Donald J.; Jiang, Shibin

    2006-01-01

    Tm-doped alkali germanate glass is investigated for use as a laser material. Spectroscopic investigations of bulk Tm-doped germanate glass are reported for the absorption, emission and luminescence decay. Tm:germanate shows promise as a fiber laser when pumped with 0.792 m diodes because of low phonon energies. Spectroscopic analysis indicates low nonradiative quenching and pulsed laser performance studies confirm this prediction by showing a quantum efficiency of 1.69.

  18. Graphing Calculators, the CBL2[TM] and TI-Interactive[TM] in High School Science.

    ERIC Educational Resources Information Center

    Molnar, Bill

    This collection of activities is designed to show how TI-Interactive[TM] and Calculator-based Laboratories (CBL) can be used to explore topics in high school science. The activities address such topics as specific heat, Boyle's Law, Newton's Law of Cooling, and Antarctic Ozone Levels. Teaching notes and calculator instructions are included as are

  19. High-efficiency wavelength and polarization selective grating-waveguide structures for Yb:YAG thin-disk lasers

    NASA Astrophysics Data System (ADS)

    Rumpel, Martin; Abdou Ahmed, Marwan; Voss, Andreas; Graf, Thomas

    2012-06-01

    We report on Grating Waveguide Structures (GWS) with a high diffraction efficiency used in Littrow configuration to select (and tune) the wavelength of an Yb:YAG thin-disk laser. The structures are composed of a multilayer HR coating, on which an additional low index layer (SiO2) and high index layer (Ta2O5) was deposited. A binary grating with a period of 580 nm is etched on top of the structure with a groove depth of 87 nm for GWS 1 and 72 nm for GWS 2. The simulation results show that the diffraction efficiency in the -1st order can reach a value of 99.99% for TE polarization, whereas it is only about 20% for TM polarization at 1030 nm. The grating was fabricated by standard interference lithography followed by a dry etching process to the desired groove depth. The spectroscopic measurement exhibited a diffraction efficiency of 99.6% for GWS 1 at 1030 nm and 99.7% for GWS 2 at 1048 nm. The devices were placed as end-mirror into the resonator of a Yb:YAG thin-disk laser. An output power of up to 110 W could be obtained from the laser in fundamental-mode operation (M2 ~ 1.2) with GWS 1, corresponding to an optical efficiency of ?oo = 36.2%. In multi-mode operation (M2 ~ 6) a power of 325 W with ?oo = 53.2% could be extracted. The spectral bandwidth of the emitted beam was measured using an Optical Spectrum Analyzer (OSA) to be less than 20 pm in fundamental-mode. We also showed a continuous wavelength tuning range of 46 nm for GWS 1 and of 38 nm for GWS 2. With a commercially available Stokes polarimeter the degree of linear polarization (DOLP) was measured to be higher than 98.6% over the whole power and wavelength tuning range.

  20. Novel fluorescent chelate for Eu

    NASA Astrophysics Data System (ADS)

    Savitsky, Alexander P.; Chydinov, Alexander V.; Krilova, Svetlana M.

    1995-05-01

    Novel high efficient fluorescent chelate for Eu based on diethylenethriaminepentaacetic acid and amino (beta) -diketones is proposed for time-resolved fluorescence immunoassay. The label surpasses all known chelates for europium in major spectral and luminescent characteristics. The proposed label has number of advantages over the well-known europium chelates. The assays with new fluorescent chelate do not require enhancement solution, but the sensitivity of Eu determination is the same as for DELFIA enhancement solution. The assay with new fluorescent chelate is insensitive to contamination of solutions and samples with ions of heavy metals, because the concentration of fluorescent chelate is measured and high excess of Eu prevents dissociation of fluorescent chelate complex. Techniques have been developed for covalent labeling of proteins with the new fluorescent chelate. The labelling proteins can be stored in the lyophilized state or in stabilized solution rather long and retain their immunological properties. Application of the new fluorescent chelate enables the washing step to be avoided and to develop the express non-separation assay.

  1. YB-1, a new biomarker of glioma progression, is associated with the prognosis of glioma patients.

    PubMed

    Zheng, Jin; Dong, Weijiang; Zhang, Jiangwei; Li, Guangyue; Gong, Huilin

    2016-04-01

    Y box protein 1 (YB-1) is a multifunctional cellular protein expressed in various cancers, and is a potential target in cancer therapy. Although there is evidence showing that YB-1 plays a role in human cancers, the clinical significance of YB-1 expression in glioma has not been established. In the present study, we investigated the YB-1 level in glioma tumors and analyzed the relationship between the YB-1 level and the grade of malignant glioma, with the aim of providing new ideas for the diagnosis and treatment of gliomas in clinical and basic research settings. A total of 108 patients, comprising 14, 31, 30, and 33 with gliomas of Grades I, II, III, and IV, respectively, were included in this study. The mRNA and protein levels of YB-1 were found to be significantly different between Grade IV and lower-grade tumors. The YB-1 levels in cerebrospinal fluid were significantly higher in Grades III and IV glioma patients than in Grades I and II patients. Immunofluorescence staining was used to detect the levels of YB-1 in the cytoplasm and the nucleus, and results indicated that the intracellular distribution was significantly associated with the pathological grade of glioma. A higher level of YB-1 was associated with shortened survival, suggesting that YB-1 plays a role in the progression of human glioma. PMID:26936129

  2. Role of electron transfer in Ce3+ sensitized Yb3+ luminescence in borate glass

    NASA Astrophysics Data System (ADS)

    Sontakke, Atul D.; Ueda, Jumpei; Katayama, Yumiko; Zhuang, Yixi; Dorenbos, Pieter; Tanabe, Setsuhisa

    2015-01-01

    In a Ce3+-Yb3+ system, two mechanisms are proposed so far namely, the quantum cutting mechanism and the electron transfer mechanism explaining Yb3+ infrared luminescence under Ce3+ excitation. Among them, the quantum cutting mechanism, where one Ce3+ photon (ultraviolet/blue) gives rise to two Yb3+ photons (near infrared) is widely sought for because of its huge potential in enhancing the solar cell efficiency. In present study on Ce3+-Yb3+ codoped borate glasses, Ce3+ sensitized Yb3+ luminescence at ˜1 μm have been observed on Ce3+ 5d state excitation. However, the intensity of sensitized Yb3+ luminescence is found to be very weak compared to the strong quenching occurred in Ce3+ luminescence in Yb3+ codoped glasses. Moreover, the absolute luminescence quantum yield also showed a decreasing trend with Yb3+ codoping in the glasses. The overall behavior of the luminescence properties and the quantum yield is strongly contradicting with the quantum cutting phenomenon. The results are attributed to the energetically favorable electron transfer interactions followed by Ce3+-Yb3+ ⇌ Ce4+-Yb2+ inter-valence charge transfer and successfully explained using the absolute electron binding energies of dopant ions in the studied borate glass. Finally, an attempt has been presented to generalize the electron transfer mechanism among opposite oxidation/reduction property dopant ions using the vacuum referred electron binding energy (VRBE) scheme for lanthanide series.

  3. Mechanism of tantalum adhesion on SiLK{sup TM}

    SciTech Connect

    Hu Yue; Yang Shuowang; Chen Xiantong; Lu Dong; Feng Yuanping; Wu Ping

    2005-09-19

    Tantalum adhesion on SiLK{sup TM} was investigated using first-principles method based on density functional theory. Phenylene groups were found to play a major role and the adjacent semi-benzene rings also contribute significantly to Ta adhesion on SiLK{sup TM}. In addition, the degradation effects of H{sub 2}/He reactive plasma clean on Ta adhesion on SiLK{sup TM} was investigated. Based on our findings, argon plasma treatment was suggested and implemented after reactive plasma cleaning process, which resulted in integration of SiLK{sup TM} with Cu up to seven metal layers.

  4. Three Long Lived Excited States of Tm^-

    NASA Astrophysics Data System (ADS)

    O'Malley, Steven M.; Beck, Donald R.

    2004-05-01

    Recent measurements(V. T. Davis and J. S. Thompson, Phys. Rev. A 65), 010501 (2001). have yielded 2 Tm^- states with lifetimes >50 ?s [2] with estimated electron affinities of 1 eV. Theory does not support a 4f attachment to the ground state(D. Datta and D. R. Beck, Phys. Rev. A 47), 5198 (1993)., and at most only a weak (<100 meV) 6p attachment(J. A. Chevary and S. H. Vosko, J. Phys. B 27), 657 (1994).. Our more accurate calculations for 4f, 5d, and 6p attachment to the ground state find no evidence of any bound state associated with these attachments. We then turned to attachment to ``low lying'' Tm I excited states. Candidates must have lifetimes >50 ?s, unusually long for simpler species except for He^-, Be^-, and Ba^- (T. Andersen et al., J. Phys. Chem. Ref. Data 28), 1511 (1999).. Using a relativistic configuration interaction in the continuum methodology (Z. Cai, D. R. Beck, and W. F. Perger, Phys. Rev. A 43), 4660 (1991)., we have found 3 states, 4f^125d6s^26p (J=8,9,10), with lifetimes of 10 ?s, 5 ms, and 3 ms, respectively. These are bound to their natural thresholds by 254, 258, and 173 meV and may represent what is being observed [2].

  5. TM Digital Image Products for Applications

    NASA Technical Reports Server (NTRS)

    Barker, J. L.; Gunther, F. J.; Abrams, R. B.; Ball, D. L.

    1984-01-01

    LANDSAT-4 Thematic Mapper (TM) digital image products recorded onto computer compatible tapes (CCTs), which were available for internal research purposes prior to August, 1983, are reviewed. The SCROUNGE image processing system at Goddard Space Flight Centr generated in tape formats: (1) raw band-sequential data (CCT-BT), generally used for internal transportation of digital data from one ground processing system to another; (2) calibrated data (CCT-AT), useful for reseachers doing radiometric characterization; and (3) geometrically resampled data (CCT-PT), the final product. The formats represent different steps in the process of producing fully-corrected TM data. The CCT-BT images are re-sequenced from telemetry format to image format, but are uncorrected radiometrically and geometrically. The CCT-AT images had data from two faulty data channels replaced and all data radiometrically calibrated. The CCT-PT images were resampled by cubic convolution procedures to provide a geometrically corrected image using satellite ephemeris and altitude data and scan-mirror correction data. The final product, the CCT-PT, is the one to which all of the radiometric and geometric corrections were applied.

  6. Impurity-trapped excitons and electron traps in CaF2:Yb2+ and SrF2:Yb2+ probed by transient photoluminescence enhancement

    NASA Astrophysics Data System (ADS)

    Senanayake, P. S.; Wells, J. P. R.; Reid, M. F.; Berden, G.; Meijerink, A.; Reeves, R. J.

    2013-01-01

    CaF$_2$:Yb$^{2+}$ and SrF$_2$:Yb$^{2+}$ crystals have been investigated by a two-color UV + IR transient photoluminescence enhancement technique. The enhancement gives information about both changes in internal energy levels of the excitons and liberation of electrons from traps in the crystals.

  7. YB-1 overexpression promotes a TGF-β1-induced epithelial–mesenchymal transition via Akt activation

    SciTech Connect

    Ha, Bin; Lee, Eun Byul; Cui, Jun; Kim, Yosup; Jang, Ho Hee

    2015-03-06

    The Y-box binding protein-1 (YB-1) is a transcription/translation regulatory protein, and the expression thereof is associated with cancer aggressiveness. In the present study, we explored the regulatory effects of YB-1 during the transforming growth factor-β1 (TGF-β1)-induced epithelial-to-mesenchymal transition (EMT) in lung adenocarcinoma cells. Downregulation of YB-1 increased E-cadherin promoter activity, and upregulation of YB-1 decreased promoter activity, suggesting that the YB-1 level may be correlated with the EMT. TGF-β1 induced YB-1 expression, and TGF-β1 translocated cytosolic YB-1 into the nucleus. YB-1 overexpression promoted TGF-β1-induced downregulation of epithelial markers, upregulation of mesenchymal markers, and cell migration. Moreover, YB-1 overexpression enhanced the expression of E-cadherin transcriptional repressors via TGF-β1-induced Akt activation. Our findings afford new insights into the role played by YB-1 in the TGF-β1 signaling pathway. - Highlights: • YB-1 regulates E-cadherin expression in A549 cells. • TGF-β1 induces upregulating and nuclear localization of YB-1. • YB-1 overexpression accelerates TGF-β1-induced EMT and cell migration. • YB-1 regulates Snail and Slug expression via Akt activation.

  8. Electronic structure and x-ray magnetic circular dichroism in YbAgCu4 and YbInCu4

    SciTech Connect

    Antonov, V N; Bekenov, L V; Antropov, V P

    2014-04-01

    X-ray absorption and magnetic circular dichroism spectra at the L3 edge of Yb have been studied theoretically in the mixed-valent compounds YbAgCu4 and YbInCu4 using the fully relativistic Dirac linear muffin-tin orbital band structure method. The effect of the spin-orbit (SO) interaction and Coulomb repulsion U on the electronic structure of YbAgCu4 and YbInCu4 is examined in the frame of the local spin-density approximation (LSDA)+SO+U method. The core-hole effect in the final states as well as the effect of the electric quadrupole E2 and magnetic dipole M1 transitions have been investigated. The calculated results are compared with available experimental data.

  9. Electronic structure and x-ray magnetic circular dichroism in YbAgCu4 and YbInCu4

    SciTech Connect

    Antonov, VN; Bekenov, LV; Antropov, VP

    2014-04-08

    X-ray absorption and magnetic circular dichroism spectra at the L-3 edge of Yb have been studied theoretically in the mixed-valent compounds YbAgCu4 and YbInCu4 using the fully relativistic Dirac linear muffin-tin orbital band structure method. The effect of the spin-orbit (SO) interaction and Coulomb repulsion U on the electronic structure of YbAgCu4 and YbInCu4 is examined in the frame of the local spin-density approximation (LSDA)+SO+U method. The core-hole effect in the final states as well as the effect of the electric quadrupole E-2 and magnetic dipole M-1 transitions have been investigated. The calculated results are compared with available experimental data.

  10. Electronic structure and f-orbital occupancy in Yb-substituted CeCoIn5

    SciTech Connect

    Booth, C. H.; Durakiewicz, T.; Capan, C.; Hurt, D.; Bianchi, A. D.; Joyce, J.J.; Fisk, Z.

    2011-05-03

    The local structure and 4f orbital occupancy have been investigated in Ce{sub 1−x}Yb{sub x}CoIn{sub 5} via Yb L{sub III}-edge extended x-ray absorption fine structure (EXAFS), Ce and Yb L{sub III}-edge x-ray absorption near-edge structure (XANES), and angle-resolved photoemission spectroscopy (ARPES) measurements. Yb(III) (4f{sup 13}) is the hole analog of Ce(III) (4f{sup 1}). Yb is found to be strongly intermediate-valent in Ce{sub 1−x}Yb{sub x}CoIn{sub 5} throughout the entire doping range, including pure YbCoIn{sub 5}, with an f-hole occupancy for Yb of n{sub f} ≃ 0.3 (i.e. Yb{sup 2.3+}), independent of Yb concentration and independent of temperature down to T = 20 K. In contrast, the f-electron orbital occupancy for Ce remains close to 1 for all Yb concentrations, suggesting that there is no mutual influence on n{sub f} between neighboring Ce and Yb sites. Likewise, ARPES measurements at 12 K have found that the electronic structure along {Gamma} − X is not sensitive to the Yb substitution, suggesting that the Kondo hybridization of Ce f electrons with the conduction band is not affected by the presence of Yb impurities in the lattice. The emerging picture is that in Ce{sub 1−x}Yb{sub x}CoIn{sub 5} there are two networks, interlaced but independent, that couple to the conduction band: one network of Ce ions in the heavy-fermion limit, one network of Yb ions in the strongly intermediate-valent limit. The robustness of the local and electronic structure to doping suggests the absence of charge transfer between the Ce and Yb ions, and may explain the relative robustness of superconductivity for this Ce-site substitution as compared to the In-site substitution.

  11. Comparative 3-D Modeling of tmRNA

    PubMed Central

    Burks, Jody; Zwieb, Christian; Mller, Florian; Wower, Iwona; Wower, Jacek

    2005-01-01

    Background Trans-translation releases stalled ribosomes from truncated mRNAs and tags defective proteins for proteolytic degradation using transfer-messenger RNA (tmRNA). This small stable RNA represents a hybrid of tRNA- and mRNA-like domains connected by a variable number of pseudoknots. Comparative sequence analysis of tmRNAs found in bacteria, plastids, and mitochondria provides considerable insights into their secondary structures. Progress toward understanding the molecular mechanism of template switching, which constitutes an essential step in trans-translation, is hampered by our limited knowledge about the three-dimensional folding of tmRNA. Results To facilitate experimental testing of the molecular intricacies of trans-translation, which often require appropriately modified tmRNA derivatives, we developed a procedure for building three-dimensional models of tmRNA. Using comparative sequence analysis, phylogenetically-supported 2-D structures were obtained to serve as input for the program ERNA-3D. Motifs containing loops and turns were extracted from the known structures of other RNAs and used to improve the tmRNA models. Biologically feasible 3-D models for the entire tmRNA molecule could be obtained. The models were characterized by a functionally significant close proximity between the tRNA-like domain and the resume codon. Potential conformational changes which might lead to a more open structure of tmRNA upon binding to the ribosome are discussed. The method, described in detail for the tmRNAs of Escherichia coli, Bacillus anthracis, and Caulobacter crescentus, is applicable to every tmRNA. Conclusion Improved molecular models of biological significance were obtained. These models will guide in the design of experiments and provide a better understanding of trans-translation. The comparative procedure described here for tmRNA is easily adopted for the modeling the members of other RNA families. PMID:15958166

  12. Synthesis and characterization of Er:Yb3Al5O12 nanopowder

    NASA Astrophysics Data System (ADS)

    Li, Chun; Xu, Jialin; Liu, Wang; Lin, Hai; Liu, Yu; Wang, Dan; Zhai, Jian; Fu, Tiehan; Zhou, Hu; Li, Yusheng; Liu, Jinghe; Zeng, Fanming

    2015-12-01

    Er:Yb1Al5O12 (Er:YbAG) nanopowder was prepared by carbonate coprecipitation method. Highpurity Er:YbAG powder was obtained after calcination at as low as 1000°C with an average particle size of 70 nm. The Al-O-Yb phonon vibrations were investigated and the absorption band arisen from interaction between lattice vibration and photon in YbAG is located around 610 cm-1. A strong emission peak of powder was observed at 1.53 µm with 980 nm laser excitation. An energy transfer mechanism between Yb3+ and Er3+ states responsible for the peak emission was proposed. An optimum Er3+ dopant concentration was determined.

  13. Cryogenically-cooled Yb:YGAG ceramic mode-locked laser.

    PubMed

    Muk, J; Jelnek, M; Jambunathan, V; Miura, T; Smr, M; Endo, A; Mocek, T; Kube?ek, V

    2016-01-25

    This work reports on a liquid-nitrogen-cooled, SESAM mode-locked Yb:YGAG (Yb:Y3Ga2Al3O12) ceramic laser. The Yb:YGAG has a similar structure to Yb:YAG, but its emission spectrum at low temperature remains much broader, which is suitable for ultrashort pulse generation and amplification. A stable pulse train with 119-MHz repetition rate was obtained at a wavelength of 1026 nm. The measured pulse duration is 2.4 ps, which is more than four times shorter than that achieved with a cryogenically-cooled Yb:YAG. Furthermore, laser performance of the Yb:YGAG ceramics in continuous-wave operation and wavelength tunability at 80 K was investigated. PMID:26832521

  14. Spectrum and energy levels of the Yb4+ free ion (Yb V)

    NASA Astrophysics Data System (ADS)

    Meftah, Ali; Wyart, Jean-François; Tchang-Brillet, Wan-Ü. Lydia; Blaess, Christophe; Champion, Norbert

    2013-10-01

    The spectrum of ionized ytterbium produced by a sliding spark source was recorded on the 10 m high resolution vacuum ultraviolet normal-incidence spectrograph of the Meudon Observatory. About 1080 lines attributed to Yb V, hitherto unknown, have been identified. The analysis of this spectrum established all the energy levels of the ground configuration 4f12 and, respectively 174, 12 and 43 levels of the excited configurations 4f115d,4f116s and 4f116p. The theoretical calculations by means of the Cowan codes included a least-squares optimization of the relevant radial parameters by minimizing the differences between calculated and experimental level energies, which led to mean errors of 55 cm-1 for the 56 even parity levels and 51 cm-1 for the 186 odd parity ones. Interactions with the unknown core-excited configurations 5p54f13, 5p54f126p, 5p54f125d and 5p54f126s were taken into account.

  15. Laser oscillation in hot pressed 10% Yb 3+:Lu 2O 3 ceramic

    NASA Astrophysics Data System (ADS)

    Sanghera, Jasbinder; Kim, Woohong; Baker, Colin; Villalobos, Guillermo; Frantz, Jesse; Shaw, Brandon; Lutz, Austin; Sadowski, Bryan; Miklos, Robert; Hunt, Michael; Kung, Frederic; Aggarwal, Ishwar

    2011-03-01

    We report the first demonstration of laser oscillation at 1081 nm using a 10% Yb 3+ doped Lu 2O 3 ceramic made by hot pressing of high purity co-precipitated powder. Approximately 2.5 W of output power was obtained with an optical-to-optical efficiency of 10%. This represents the highest output power obtained and the highest concentration of Yb 3+ used thus far in a Yb 3+ doped Lu 2O 3 ceramic.

  16. Laser-induced bulk damage in Yb:S-FAP crystals

    NASA Astrophysics Data System (ADS)

    Liao, Zhi M.; Adams, John J.; Jarboe, Jeff; Menapace, Joe; Nielsen, Norm; Schrauth, Sam; Wolfe, Justin; Erlandson, Al; Schaffers, Kathleen; Stolz, Christopher; Bayramian, Andy; Carid, John

    2007-01-01

    The Mercury laser uses ytterbium-doped strontium fluorapatite (Yb:S-FAP) crystals as the gain medium with a nominal clear aperture of 4 x 6 cm. Recent damage test data have indicated the existence of bulk precursors in Yb:S-FAP that initiate damage starting at approximately 10 J/cm2 at 9 ns under 1064 nm irradiation. In this paper, we report on preliminary results on bulk damage studies on Yb:S-FAP crystals.

  17. Links between the Oncoprotein YB-1 and Small Non-Coding RNAs in Breast Cancer

    PubMed Central

    Blenkiron, Cherie; Hurley, Daniel G.; Fitzgerald, Sandra; Print, Cristin G.; Lasham, Annette

    2013-01-01

    Background The nucleic acid-binding protein YB-1, a member of the cold-shock domain protein family, has been implicated in the progression of breast cancer and is associated with poor patient survival. YB-1 has sequence similarity to LIN28, another cold-shock protein family member, which has a role in the regulation of small noncoding RNAs (sncRNAs) including microRNAs (miRNAs). Therefore, to investigate whether there is an association between YB-1 and sncRNAs in breast cancer, we investigated whether sncRNAs were bound by YB-1 in two breast cancer cell lines (luminal A-like and basal cell-like), and whether the abundance of sncRNAs and mRNAs changed in response to experimental reduction of YB-1 expression. Results RNA-immunoprecipitation with an anti-YB-1 antibody showed that several sncRNAs are bound by YB-1. Some of these were bound by YB-1 in both breast cancer cell lines; others were cell-line specific. The small RNAs bound by YB-1 were derived from various sncRNA families including miRNAs such as let-7 and miR-320, transfer RNAs, ribosomal RNAs and small nucleolar RNAs (snoRNA). Reducing YB-1 expression altered the abundance of a number of transcripts encoding miRNA biogenesis and processing proteins but did not alter the abundance of mature or precursor miRNAs. Conclusions YB-1 binds to specific miRNAs, snoRNAs and tRNA-derived fragments and appears to regulate the expression of miRNA biogenesis and processing machinery. We propose that some of the oncogenic effects of YB-1 in breast cancer may be mediated through its interactions with sncRNAs. PMID:24260353

  18. SpellRead[TM]. What Works Clearinghouse Intervention Report

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2013

    2013-01-01

    "SpellRead"[TM], formerly known as "SpellRead Phonological Auditory Training"[R], is a small-group literacy program for struggling readers in grades 2-12. "SpellRead"[TM] integrates the auditory and visual aspects of the reading process and emphasizes specific skill mastery through systematic and explicit instruction. Students are taught to

  19. Full Immersive Virtual Environment Cave[TM] in Chemistry Education

    ERIC Educational Resources Information Center

    Limniou, M.; Roberts, D.; Papadopoulos, N.

    2008-01-01

    By comparing two-dimensional (2D) chemical animations designed for computer's desktop with three-dimensional (3D) chemical animations designed for the full immersive virtual reality environment CAVE[TM] we studied how virtual reality environments could raise student's interest and motivation for learning. By using the 3ds max[TM], we can visualize

  20. Notes from ERIC/TM: Educational Measurement Productivity.

    ERIC Educational Resources Information Center

    Rudner, Lawrence M.; And Others

    1991-01-01

    During a 28-month period beginning in January 1988, the ERIC Clearinghouse on Tests, Measurement, and Evaluation (ERIC/TM) selected documents submitted by over 800 organizations for entry into the ERIC database. Twenty-three organizations, which submitted 595 (31 percent) of the 1,904 documents accepted by ERIC/TM during that period, are

  1. Relative radiometric calibration of LANDSAT TM reflective bands

    NASA Technical Reports Server (NTRS)

    Barker, J. L.

    1984-01-01

    A common scientific methodology and terminology is outlined for characterizing the radiometry of both TM sensors. The magnitude of the most significant sources of radiometric variability are discussed and methods are recommended for achieving the exceptional potential inherent in the radiometric precision and accuracy of the TM sensors.

  2. Doors to Discovery[TM]. What Works Clearinghouse Intervention Report

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2007

    2007-01-01

    "Doors to Discovery"[TM] is an early childhood curriculum that uses thematic units to engage young children and support them as they build an understanding of their world. "Doors to Discovery"[TM] literacy activities are used to encourage children's development in a number of areas identified by research as the foundation for early literacy

  3. Inside Linden Lab: Second Life [TM] for Educators

    ERIC Educational Resources Information Center

    Atkinson, Tom

    2008-01-01

    A new culture called Second Life [TM] has emerged that promises innovative strategies for everything from social interactions to business. Some educators believe it may hold new and unique opportunities for teaching and learning. Second Life [TM] (SL) is the creation of Linden Labs, a San Francisco-based corporation defined by its creators as "an

  4. Utilising eduroam[TM] Architecture in Building Wireless Community Networks

    ERIC Educational Resources Information Center

    Huhtanen, Karri; Vatiainen, Heikki; Keski-Kasari, Sami; Harju, Jarmo

    2008-01-01

    Purpose: eduroam[TM] has already been proved to be a scalable, secure and feasible way for universities and research institutions to connect their wireless networks into a WLAN roaming community, but the advantages of eduroam[TM] have not yet been fully discovered in the wireless community networks aimed at regular consumers. This aim of this

  5. 75 FR 61480 - Cobscook Bay OCGenTM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-05

    ... Energy Regulatory Commission Cobscook Bay OCGen\\TM\\ Power; Notice of Preliminary Permit Application..., pursuant to section 4(f) of the Federal Power Act, proposing to study the feasibility of the Cobscook Bay OCGen\\TM\\ Power Project, located in the Cobscook Bay, near the City of Eastport, Washington...

  6. 75 FR 61479 - Western Passage OCGenTM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-05

    ... Energy Regulatory Commission Western Passage OCGen\\TM\\ Power Project; Notice of Preliminary Permit... permit, pursuant to section 4(f) of the Federal Power Act, proposing to study the feasibility of the Western Passage OCGen\\TM\\ Power Project, located in Western Passage, in the vicinity of the City...

  7. Accelerated Math[TM]. What Works Clearinghouse Intervention Report

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2011

    2011-01-01

    "Accelerated Math"[TM], published by Renaissance Learning, is a software tool used to customize assignments and monitor progress in math for students in grades 1-12. The "Accelerated Math"[TM] software creates individualized assignments aligned with state standards and national guidelines, scores student work, and generates reports on student

  8. Full Immersive Virtual Environment Cave[TM] in Chemistry Education

    ERIC Educational Resources Information Center

    Limniou, M.; Roberts, D.; Papadopoulos, N.

    2008-01-01

    By comparing two-dimensional (2D) chemical animations designed for computer's desktop with three-dimensional (3D) chemical animations designed for the full immersive virtual reality environment CAVE[TM] we studied how virtual reality environments could raise student's interest and motivation for learning. By using the 3ds max[TM], we can visualize…

  9. The valence of Ru, Ce and Eu ions in the magneto-superconductor Eu 1.5Ce 0.5RuSr 2Cu 2O 10

    NASA Astrophysics Data System (ADS)

    Felner, I.; Asaf, U.; Godart, C.; Alleno, E.

    1999-01-01

    The superconducting (T c?32 K) Eu 1.5Ce 0.5RuSr 2Cu 2O 10 (Ru-2122) material is also magnetically ordered (T M?122 K) with TM? Tc. Superconductivity (SC) is confined to the CuO 2 planes, whereas magnetism is due to the Ru sublattice. Mossbauer spectroscopy performed at 90 and 300 K on 151Eu shows a single narrow line with an isomer shift=0.69(2) and a quadrupole splitting of 1.84 mm/s, indicating that the Eu ions are trivalent with a nonmagnetic J=0 ground state. This is in agreement with X-ray-absorption spectroscopy (XAS) taken at L III edges of Eu, Ce which shows that Eu is trivalent and Ce is tetravalent. XAS experiments at the K edge of Ru indicate that Ru is pentavalent. This indicates, that in the M-2122 system, SC exists only for pentavalent M ions such as Ta, Nb and Ru.

  10. LaVo4: Eu Phosphor Films with Enhanced Eu Solubility

    SciTech Connect

    Hwang, Harold

    2011-08-11

    Eu doped rare-earth orthovanadates are known to be good red phosphor materials. In particular, LaVO{sub 4}:Eu is a promising candidate due to the low Eu-site point symmetry, and thus high dipole transition probability within Judd-Ofelt theory. However, the low solubility limit (< 3 mol %) of Eu in LaVO{sub 4} prevents its efficient use as a phosphor. We present optical evidence of enhanced Eu solubility as high as 10 mol % in LaVO{sub 4}:Eu thin films grown by pulsed laser deposition and postannealing. The photoluminescent intensity exceeded that of YVO{sub 4}:Eu thin films when excited below the host bandgap, indicating stronger direct emission of Eu in LaVO{sub 4}.

  11. High efficiency Yb:YAG crystalline fiber-waveguide lasers.

    PubMed

    Mu, Xiaodong; Meissner, Stephanie; Meissner, Helmuth; Yu, Anthony W

    2014-11-01

    A laser diode (LD) cladding pumped single-mode 1030 nm laser has been demonstrated, in an adhesive-free bonded 40 ?m core Yb:YAG crystalline fiber waveguide (CFW). A laser output power of 13.2 W at a wavelength of 1.03 ?m has been achieved, for an input pump power of 39.5 W. The corresponded laser efficiency is 33.4%. The laser beam quality is confirmed to be near diffraction-limited, with a measured M2 = 1.02. A LD core pumped single-clad Yb:YAG CFW laser has also been demonstrated with a top-hat laser beam profile, with a laser output power of 28 W and a slope efficiency of 78%. PMID:25361347

  12. Charge Fluctuations and the Valence Transition in Yb under Pressure

    SciTech Connect

    Ylvisaker, E R; Kunes, J; McMahan, A K; Pickett, W E

    2009-04-21

    We present a dynamical mean field theory study of the valence transition (f{sup 14} {yields} f{sup 13}) in elemental, metallic Yb under pressure. Our calculations reproduce the observed valence transition as reflected in the volume dependence of the 4f occupation. The transition is accelerated by heating, and suggests quasiparticle or Kondo-like structure in the spectra of the trivalent end state, consistent with the early lanthanides. Results for the local charge fluctuations and susceptibility, however, show novel signatures uniquely associated with the valence transition itself, indicating that Yb is a fluctuating valence material in contrast to the intermediate valence behavior seen in the early trivalent lanthanides Ce, Pr, and Nd.

  13. Quantum Critical Behavior in YbRh_2Si_2

    NASA Astrophysics Data System (ADS)

    Steglich, F.

    2002-03-01

    Single crystals of the ``heavy-fermion'' metal YbRh_2Si2 show pronounced non-Fermi-liquid (NFL) phenomena at p = 0 and B = 0. These are related to a weak antiferromagnetic (AF) transition at TN ≈ 70 mK. By doping with 5at% Ge, the Néel temperature is depressed to below T = 10 mK, i.e., the system is pushed toward the quantum critical point (TN arrow 0). For the YbRh_2(Si_0.95Ge_0.05)2 single crystal the resistivity ρ is found to depend linearly on T over more than three decades for T >= 10 mK, reminiscent of the prediction for the frequently adopted spin-density-wave scenario (assuming 2D AF spinfluctuations). Recent results of magnetic and thermodynamic measurements are in striking conflict with this scenario.

  14. Compact nanosecond pulsed single stage Yb-doped fiber amplifier

    NASA Astrophysics Data System (ADS)

    Balliu, E.; Engholm, M.; Hellstrm, J.; Elgcrona, G.; Karlsson, H.

    2014-02-01

    In this work we present a compact, nanosecond pulsed, single frequency, single stage Yb-doped fiber amplifier by using an overall fiber core diameter of 20 ?m. The key component is a custom made, compact, ultra-low noise, single frequency ring-cavity solid state laser (SSL) at 1064 nm used as a master oscillator. The SSL can be designed to provide nanosecond pulses with pulse energies in the sub-mJ range. Our ultimate goal is to develop a compact linearly polarized, single frequency, nanosecond pulsed laser source in an all-fiber format. Short (less than 1m), highly Yb-doped fibers have been used in order to suppress non-linear effects.

  15. Registratiom of TM data to digital elevation models

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Several problems arise when attempting to register LANDSAT thematic mapper data to U.S. B Geological Survey digital elevation models (DEMs). The TM data are currently available only in a rotated variant of the Space Oblique Mercator (SOM) map projection. Geometric transforms are thus; required to access TM data in the geodetic coordinates used by the DEMs. Due to positional errors in the TM data, these transforms require some sort of external control. The spatial resolution of TM data exceeds that of the most commonly DEM data. Oversampling DEM data to TM resolution introduces systematic noise. Common terrain processing algorithms (e.g., close computation) compound this problem by acting as high-pass filters.

  16. Interfacial effects in Fe/4d TM multilayers (abstract)

    SciTech Connect

    Tomaz, M.A.; Antel, W.J., Jr.; Harp, G.R.; OBrien, W.L.

    1997-04-01

    We have studied Fe/TM multilayers (TM=Mo, Nb, Ru, Rh, Pd) using x-ray magnetic circular dischroism, magneto-optical Kerr effect, and x-ray diffraction. A diverse set of magnetic behaviors emerges from the analysis. We focus on the behavior which can be attributed to the existence of a physical interface between different chemical species. In particular, we have measured an enhanced Fe moment in some cases (TM=Ru, Mo, Rh, Pd) yet not in others (TM=Nb). These results will be discussed, including the relative orbital and spin moments and the effects of alloying at the interface. The measured induced moments in the TM layer will be presented as well where applicable. {copyright} {ital 1997 American Institute of Physics.}

  17. Water quality mapping using Landsat TM imagery

    NASA Astrophysics Data System (ADS)

    Lim, H. S.; MatJafri, M. Z.; Abdullah, K.; Alias, A. N.; Wong, C. J.; Mustapha-Rosli, M. R.; Mohd Saleh, N.

    2009-05-01

    Environmental monitoring through the method of traditional ship sampling is time consuming and requires a high survey cost. The objective of this study is to evaluate the feasibility of Landsat TM imagery for total suspended solids (TSS) mapping using a newly developed algorithm over Penang Island. The study area is the seawater region around Penang Island, Malaysia. Water samples were collected during a 3-hour period simultaneously with the satellite image acquisition and later analyzed in the laboratory above the study area. The samples locations were determined using a handheld GPS. The satellite image was geometrically corrected using the second order polynomial transformation. The satellite image also was atmospheric corrected by using ATCOR2 image processing software. The digital numbers for each band corresponding to the sea-truth locations were extracted and then converted into reflectance values for calibration of the water quality algorithm. The proposed algorithm is based on the reflectance model that is a function of the inherent optical properties of water, which can be related to its constituent's concentrations. The generated algorithm was developed for three visible wavelenghts, red, green and blue for this study. Results indicate that the proposed developed algorithm was superior based on the correlation coefficient (R) and root-mean-square deviation (RMS) values. Finally the proposed algorithm was used for TSS mapping at Penang Island, Malaysia. The generated TSS map was colour-coded for visual interpretation and image smoothing was performed on the map to remove random noise. This preliminary study has produced a promising result. This study indicates that the empirical algorithm is suitable for TSS mapping around Penang Island by using satellite Landsat TM data.

  18. X-RAY ABSORPTION SPECTROSCOPY OF YB3+-DOPED OPTICAL FIBERS

    SciTech Connect

    Citron, Robert; Kropf, A.J.

    2008-01-01

    Optical fibers doped with Ytterbium-3+ have become increasingly common in fiber lasers and amplifiers. Yb-doped fibers provide the capability to produce high power and short pulses at specific wavelengths, resulting in highly effective gain media. However, little is known about the local structure, distribution, and chemical coordination of Yb3+ in the fibers. This information is necessary to improve the manufacturing process and optical qualities of the fibers. Five fibers doped with Yb3+ were studied using Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy and X-ray Absorption Near Edge Spectroscopy (XANES), in addition to Yb3+ mapping. The Yb3+ distribution in each fiber core was mapped with 2D and 1D intensity scans, which measured X-ray fluorescence over the scan areas. Two of the five fibers examined showed highly irregular Yb3+ distributions in the core center. In four of the five fibers Yb3+ was detected outside of the given fiber core dimensions, suggesting possible Yb3+ diffusion from the core, manufacturing error, or both. X-ray absorption spectroscopy (XAS) analysis has so far proven inconclusive, but did show that the fibers had differing EXAFS spectra. The Yb3+ distribution mapping proved highly useful, but additional modeling and examination of fiber preforms must be conducted to improve XAS analysis, which has been shown to have great potential for the study of similar optical fi bers.

  19. Thermoluminescence properties of ZnO and ZnO:Yb nanophosphors

    SciTech Connect

    Pal, U.; Melendrez, R.; Chernov, V.; Barboza-Flores, M.

    2006-10-30

    ZnO and ZnO:Yb thermoluminescence nanophosphors have been developed and tested under beta radiation. Spherical nanoparticles of sizes ranging from 130 to 1200 nm were prepared through a glycol mediated chemical synthesis. The Yb doping had a thermoluminescence quenching effect compared to undoped ZnO. The 5% Yb concentration produced a low fading, a single thermoluminescence glow peak structure, and a dose linearity behavior adequate for thermoluminescence dosimetry applications. The ZnO:Yb nanophosphor has a great potential as a dosimeter for monitoring in ionizing radiation fields.

  20. Yb-based heavy fermion compounds and field tuned quantum chemistry

    SciTech Connect

    Mun, Eundeok

    2010-07-23

    The motivation of this dissertation was to advance the study of Yb-based heavy fermion (HF) compounds especially ones related to quantum phase transitions. One of the topics of this work was the investigation of the interaction between the Kondo and crystalline electric field (CEF) energy scales in Yb-based HF systems by means of thermoelectric power (TEP) measurements. In these systems, the Kondo interaction and CEF excitations generally give rise to large anomalies such as maxima in {rho}(T) and as minima in S(T). The TEP data were use to determine the evolution of Kondo and CEF energy scales upon varying transition metals for YbT{sub 2}Zn{sub 20} (T = Fe, Ru, Os, Ir, Rh, and Co) compounds and applying magnetic fields for YbAgGe and YbPtBi. For YbT{sub 2}Zn{sub 20} and YbPtBi, the Kondo and CEF energy scales could not be well separated in S(T), presumably because of small CEF level splittings. A similar effect was observed for the magnetic contribution to the resistivity. For YbAgGe, S(T) has been successfully applied to determine the Kondo and CEF energy scales due to the clear separation between the ground state and thermally excited CEF states. The Kondo temperature, T{sub K}, inferred from the local maximum in S(T), remains finite as magnetic field increases up to 140 kOe. In this dissertation we have examined the heavy quasi-particle behavior, found near the field tuned AFM quantum critical point (QCP), with YbAgGe and YbPtBi. Although the observed nFL behaviors in the vicinity of the QCP are different between YbAgGe and YbPtBi, the constructed H-T phase diagram including the two crossovers are similar. For both YbAgGe and YbPtBi, the details of the quantum criticality turn out to be complicated. We expect that YbPtBi will provide an additional example of field tuned quantum criticality, but clearly there are further experimental investigations left and more ideas needed to understand the basic physics of field-induced quantum criticality in Yb-based systems.

  1. YbPtGe2: A multivalent charge-ordered system with an unusual spin pseudogap

    NASA Astrophysics Data System (ADS)

    Gumeniuk, Roman; Sarkar, Rajib; Geibel, Christoph; Schnelle, Walter; Paulmann, Carsten; Baenitz, Michael; Tsirlin, Alexander A.; Guritanu, Violeta; Sichelschmidt, Jrg; Grin, Yuri; Leithe-Jasper, Andreas

    2012-12-01

    We performed a study of the structural and physical properties of YbPtGe2. This compound is a multivalent charge-ordered system presenting an unusual spin pseudogap below 200 K. The crystal structure of YbPtGe2 is refined from single-crystal and powder high-resolution synchrotron x-ray diffraction data at different temperatures. Analysis of the structural features of YbPtGe2, together with a combined study of Yb LIII x-ray absorption spectroscopy, magnetic susceptibility ?(T), thermopower S(T), and 171Yb and 195Pt NMR indicate half of the Yb atoms to be in an intermediate valence state with an electronic configuration close to 4f13 (Yb3+), while for the remaining Yb atoms the 4f14 (Yb2+) configuration with almost no valence fluctuations is most likely. A drastic drop of the magnetic susceptibility and a decrease of the isotropic shift 195Kiso(T) with decreasing temperature in the temperature range of 50-200 K evidence the opening of a spin pseudogap with an activation energy of ?/kB 200 K. Surprisingly, transport properties do not show clear evidence for the opening of a charge gap, thus excluding a standard Kondo-insulator scenario. Possible origins for this unusual electronic (valence) behavior are discussed.

  2. The Cold Shock Domain of YB-1 Segregates RNA from DNA by Non-Bonded Interactions

    PubMed Central

    Kljashtorny, Vladislav; Nikonov, Stanislav; Ovchinnikov, Lev; Lyabin, Dmitry; Vodovar, Nicolas; Curmi, Patrick; Manivet, Philippe

    2015-01-01

    The human YB-1 protein plays multiple cellular roles, of which many are dictated by its binding to RNA and DNA through its Cold Shock Domain (CSD). Using molecular dynamics simulation approaches validated by experimental assays, the YB1 CSD was found to interact with nucleic acids in a sequence-dependent manner and with a higher affinity for RNA than DNA. The binding properties of the YB1 CSD were close to those observed for the related bacterial Cold Shock Proteins (CSP), albeit some differences in sequence specificity. The results provide insights in the molecular mechanisms whereby YB-1 interacts with nucleic acids. PMID:26147853

  3. Valence state change and defect centers induced by infrared femtosecond laser in Yb:YAG crystals

    SciTech Connect

    Wang, Xinshun Liu, Yang; Zhao, Panjuan; Guo, Zhongyi; Li, Yan; Qu, Shiliang

    2015-04-21

    The broad band upconversion luminescence in Yb{sup 3+}:YAG crystal has been observed in experiments under the irradiation of focused infrared femtosecond laser. The dependence of the fluorescence intensity on the pump power shows that the upconversion luminescence is due to simultaneous two-photon absorption process, which indicates that the broad emission bands at 365 and 463?nm could be assigned to the 5d ? 4f transitions of Yb{sup 2+} ions and the one at 692?nm could be attributed to the electron-hole recombination process on (Yb{sup 2+}-F{sup +}) centers. The absorption spectra of the Yb:YAG crystal samples before and after femtosecond laser irradiation, and after further annealing reveal that permanent valence state change of Yb ions from Yb{sup 3+} to Yb{sup 2+} and (Yb{sup 2+}-F{sup +}) centers have been induced by infrared femtosecond laser irradiation in Yb{sup 3+}:YAG crystal.

  4. The Yb-doped aluminosilicate fibers photodarkening mechanism based on the charge-transfer state excitation

    NASA Astrophysics Data System (ADS)

    Rybaltovsky, A. A.; Bobkov, K. K.; Velmiskin, V. V.; Umnikov, A. A.; Shestakova, I. A.; Guryanov, A. N.; Likhachev, M. E.; Bubnov, M. M.; Dianov, E. M.

    2014-03-01

    We have studied the photodarkening effect in fiber preforms with an ytterbium-doped aluminosilicate glass core. The room-temperature stable Yb2+ ions formation in the glass matrix under both UV- and NIR-pumping irradiation was revealed by the method of absorption spectra analysis and the fluorescence spectroscopy technique. Comparative studies of preforms and crystals samples luminescence spectra, obtained under UV-excitation, were performed. A general mechanism of Yb2+ ions and aluminium oxygen-hole centers (Al-OHC) formation as a result of photoinduced process of Yb3+ ions excitation to "charge-transfer state" (CTS) was found for both Yb:YAG crystal and aluminosilicate glass.

  5. Interplay between YB-1 and IL-6 promotes the metastatic phenotype in breast cancer cells

    PubMed Central

    Castellana, Bàrbara; Aasen, Trond; Moreno-Bueno, Gema; Dunn, Sandra E.; Ramón y Cajal, Santiago

    2015-01-01

    Epithelial to mesenchymal transition (EMT) induces cell plasticity and promotes metastasis. The multifunctional oncoprotein Y-box binding protein-1 (YB-1) and the pleiotropic cytokine interleukin 6 (IL-6) have both been implicated in tumor cell metastasis and EMT, but via distinct pathways. Here, we show that direct interplay between YB-1 and IL-6 regulates breast cancer metastasis. Overexpression of YB-1 in breast cancer cell lines induced IL-6 production while stimulation with IL-6 increased YB-1 expression and YB-1 phosphorylation. Either approach was sufficient to induce EMT features, including increased cell migration and invasion. Silencing of YB-1 partially reverted the EMT and blocked the effect of IL-6 while inhibition of IL-6 signaling blocked the phenotype induced by YB-1 overexpression, demonstrating a clear YB-1/IL-6 interdependence. Our findings describe a novel signaling network in which YB-1 regulates IL-6, and vice versa, creating a positive feed-forward loop driving EMT-like metastatic features during breast cancer progression. Identification of signaling partners or pathways underlying this co-dependence may uncover novel therapeutic opportunities. PMID:26512918

  6. Broadband infrared luminescence in Yb-doped Bi2O3-GeO2 glasses

    NASA Astrophysics Data System (ADS)

    Yu, Pingsheng; Su, Liangbi; Cheng, Junhua; Xu, Jun

    2016-01-01

    The Yb-doped Bi2O3-GeO2 glasses were prepared by the conventional melt quenching technique. Near-infrared (NIR) broadband emission was found at about 1024 nm, and 1330 nm (under 785 nm excitation), and the measured fluorescent lifetime was about several hundred microseconds. The emission intensity of Yb-doped Bi2O3-GeO2 glasses increased with increasing of Yb dopant in our experiments. The NIR emission should be related to Yb3+ and lower valence Bi ions.

  7. Efficient lasing in Yb:(YLa)2O3 ceramics

    NASA Astrophysics Data System (ADS)

    Snetkov, I. L.; Mukhin, I. B.; Balabanov, S. S.; Permin, D. A.; Palashov, O. V.

    2015-02-01

    A high-optical-quality sample of Yb0.1Y1.7La0.2O3 ceramics is prepared using a recently developed technique of selfpropagating high-temperature synthesis of rare-earth-doped yttrium oxide nanopowder from acetate - nitrates of metals. Its optical and spectral characteristics are studied, and quasi-cw lasing at a wavelength of 1033 nm is achieved with a power of 7 W and a slope efficiency of 25%.

  8. NUCLEAR PHYSICS: Formation Mechanism of Triaxial Superdeformed Nucleus 160Yb

    NASA Astrophysics Data System (ADS)

    Dong, Yong-Sheng; Yu, Shao-Ying; Shen, Cai-Wan; Liu, Yan-Xin

    2009-10-01

    By using Total Routhian Surface (TRS) method the deformation of the nucleus 160Yb is studied. The result shows that the triaxial superdeformed state exists with deformation parameters in2 = 0.38 and γ = 21°, where proton shell correction energy plays a key role, and the sum of two quasi-proton particle energies gives an additional driving effect. The rotational energy also has an additional role in the formation of triaxial superdeformed.

  9. Synthesis and spectral characterization of EuPO4 and LaPO4:Eu nanorods.

    PubMed

    De-Hui, Sun; Ji-Lin, Zhang; De-Xin, Sun

    2010-03-01

    Monoclinic monazite-type EuPO4 and LaPO4:Eu nanorods were synthesized by a microemulsion-assisted solvothermal method. Their morphologies, structures, and fluorescent properties were characterized by SEM, XRD, and photoluminescence (PL) modern analytic means, respectively. The aspect ratios of EuPO4 and LaPO4:Eu nanorods have a decreasing tendency with increasing carbon chain length of assisted surfactants. When the assisted surfactant was n-butyl alcohol, the EuPO4 exhibited nanorod morphology with diameters from 20 to 30 nm and lengths from 100 to 150 nm. When the assisted surfactant was n-pentanol, the EuPO4 nanorods had lengths between 200 and 300 nm and a diameter range similar to that of the n-butyl alcohol nanorods. When the assisted surfactant was n-hexanol and n-octyl alcohol, only elliptical EuPO4 products were obtained. The LaPO4:Eu nanorods synthesized in the presence of different assisted-surfactants exhibited elliptical morphologies with diameters of 40-60 nm and lengths of 70-110 nm. The LaPO4:Eu and EuPO4 nanorods showed a orange prominent emission peak from magnetic-dipole transition 5D0 --> F1 (593 nm) of Eu3+ ions whose sites in the EuPO4 and LaPO4:Eu nanorods have C1 symmetry. Compared with bulk LaPO4:Eu, the fine structure of the Eu-O charge transfer band has very small red shift resulting from the slight increase of the length of Eu-O bond due to nanoscale size effect. PMID:20355574

  10. Contribution of Eu 4f states to the magnetic anisotropy of EuO

    SciTech Connect

    Arenholz, E.; Schmehl, A.; Schlom, D.G.; van der Laan, G.

    2008-09-11

    Anisotropic x-ray magnetic linear dichroism (AXMLD) provides a novel element-, site-, shell-, and symmetry-selective techniques to study the magnetic anisotropy induced by a crystalline electric field. The weak Eu2+ M4,5 AXMLD observed in EuO(001) indicates that the Eu 4f states are not rotationally invariant and hence contribute weakly to the magnetic anisotropy of EuO. The results are contrasted with those obtained for 3d transition metal oxides.

  11. Structure of Tm2 and Tm2C2 encapsulated in low-symmetry C82(Cs(6)) fullerene cage by single crystal X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Sado, Yuki; Aoyagi, Shinobu; Izumi, Noriko; Kitaura, Ryo; Kowalczyk, Tim; Wang, Jian; Irle, Stephan; Nishibori, Eiji; Sugimoto, Kunihisa; Shinohara, Hisanori

    2014-04-01

    The molecular structures of Tm2@C82(Cs(6)) and Tm2C2@C82(Cs(6)) are determined by means of single crystal X-ray diffraction using the co-crystals with nickel octaethylporphyrin (Ni(OEP)). The molecular orientations and Tm positions of Tm2@C82(Cs(6)) and Tm2C2@C82(Cs(6)) are basically the same each other. One of the two Tm positions is very close to the Tm position of Tm@C82(Cs(6)). These facts demonstrate that the stable endohedral Tm positions are not fundamentally affected by the addition of the other Tm atoms but dependent on the kind of the fullerene cage structure.

  12. 76 FR 38618 - Proposed Information Collection; Comment Request; StormReadyTM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-01

    ...Ready\\TM\\, TsunamiReady\\TM\\ and StormReady/TsunamiReady\\TM\\ Application Forms AGENCY: National Oceanic... TsunamiReady and StormReady/TsunamiReady programs also in this information collection, is a...

  13. Thermoelectric nanocrystalline YbCoSb laser prepared layers

    NASA Astrophysics Data System (ADS)

    Jelínek, Miroslav; Zeipl, Radek; Kocourek, Tomáš; Remsa, Jan; Navrátil, Jiří

    2016-03-01

    Filled thermoelectric Yb x Co4Sb12 layers were prepared by pulsed laser deposition method. The Yb0.19Co4Sb12 target was fabricated by hot pressing. Various deposition conditions were tested: target—substrate distance d T-S (4 or 6 cm), ambient argon pressure (from 0.5 to 13 Pa), laser repetition rate (from 3 to 10 Hz), substrate temperature (from 250 to 400 °C) and laser fluence (in region from 0.8 to 5 J cm-2). Film roughness was determined by mechanical profilometer and by AFM. For d T-S = 4 cm we observed a deficit of Yb and surplus of Co. Sb was transferred from target to film roughly stoichiometrically (as measured by EDX). Films created at 0.8 J cm-2 exhibited generally poor stoichiometry and mechanical properties. Optimal conditions and stoichiometric transport were found for d T-S = 6 cm and 13 Pa of Ar. XRD shows that the films were nanocrystalline with CoSb3 structure. Grain size was in the range of ~50-80 nm. Temperature dependence of Seebeck coefficient and power factor was measured. Thermoelectric efficiency ZT ~ 0.04-0.05 was measured at room temperature using Harman method. In dependence on layers quality, we calculated thermal conductivity λ ~ 0.4-1.3 W K-1 m-1.

  14. Magnetic properties of nanocrystalline mechanically alloyed Fe?TM?C powder (TM = Ta, Hf, W, Mo, Nb, Zr, and Ti)

    NASA Astrophysics Data System (ADS)

    Kuhrt, C.

    1996-05-01

    Two-phase nanocomposites of ?-Fe and a transition metal (TM) carbide were prepared by mechanical alloying and annealing of elemental Fe80TM10C10 powder blends. The soft magnetic properties remain generally limited (coercivity ? 300 A/m), presumably caused by a 'coarse' grain fraction (> 20 nm) originating from inhomogeneities in the mechanically alloyed precursor.

  15. Temperature-dependent lasing and spectroscopy of Yb:Y 2O 3 and Yb:Sc 2O 3

    NASA Astrophysics Data System (ADS)

    Merkle, Larry D.; Alex Newburgh, G.; Ter-Gabrielyan, Nikolay; Michael, Arockiasamy; Dubinskii, Mark

    2008-12-01

    Spectroscopic and laser properties of Yb 3+ in ceramic Y 2O 3 have been studied at room and cryogenic temperatures. Laser performance is very substantially improved by cooling to liquid nitrogen temperature, primarily due to the great reduction in ground state absorption that permits laser operation on the much stronger 1030-nm emission line rather than the 1077-nm line. The 976-nm "zero line" is observed to become much weaker as the temperature is reduced. Several models for this behavior are considered, but none adequately explains this surprising result. Spectroscopy of Yb:Sc 2O 3 indicates that it is likely to be an even better cryogenic gain material, given samples of comparable optical quality.

  16. Diode-pumped multilayer Yb:YAG composite ceramic laser Diode-pumped multilayer Yb:YAG composite ceramic laser

    NASA Astrophysics Data System (ADS)

    Tang, F.; Cao, Y. G.; Huang, J. Q.; Guo, W.; Liu, H. G.; Wang, W. C.; Huang, Q. F.; Li, J. T.

    2012-08-01

    All-ceramic multilayer composite ytterbium doped yttrium aluminum garnet (Yb:YAG) laser gain medium with doping concentration distribution of 0-5-10-15-20-15-10-5-0 at.% Yb ions was successfully fabrication by the technique of tape casting and simple vacuum sintering process. Full dense microstructure is achieved, and excellent optical properties are gained. The obtained result shows that the optical transmittance of >80% is reached when the wavelength is larger than 500 nm. The emission cross section is 4.0310-20 cm2 at the wavelength of 1030 nm. Continuous wave (CW) laser performance is further demonstrated when the sample is pumped by 940 nm fiber-coupler diode laser. The threshold absorbed pump power is 5.9 W, and the slope efficiency attains to 27% with transmission of output coupler of 6%.

  17. First principle investigations on structural, mechanical, spin polarized electronic and magnetic properties of TmZn and TmCd

    NASA Astrophysics Data System (ADS)

    Chand, Satish; Singh, R. P.; Govindan, A.

    2015-09-01

    Structural, mechanical, spin polarized electronic and magnetic properties of TmZn and TmCd intermetallic compounds have been studied using the full-potential linearize augmented plane-wave plus local orbital method. The structural and mechanical properties have been studied in terms of lattice parameter ( a 0), bulk modulus ( B 0) and its first-order pressure derivative (B0^' }), elastic constants ( C ij ), Young's modulus ( Y), shear modulus ( G) and Poisson's ratio (\\upsilon) in equilibrium state which are found to be consistent with available experimental/theoretical values. Spin polarized electronic properties have been investigated in terms of band structure and density of state histograms for spin up and spin down channel. Electronic behavior of TmZn and TmCd shows that studied materials are metallic ferromagnets with high spin polarization in which Tm-f state electrons have dominant character.

  18. From the ternary Eu(Au/In)2 and EuAu4(Au/In)2 with remarkable Au/In distributions to a new structure type: The gold-rich Eu5Au16(Au/In)6 structure

    SciTech Connect

    Steinberg, Simon; Card, Nathan; Mudring, Anja -Verena

    2015-08-13

    The ternary Eu(Au/In)2 (EuAu0.46In1.54(2)) (I), EuAu4(Au/In)2 (EuAu4+xIn2–x with x = 0.75(2) (II), 0.93(2), and 1.03(2)), and Eu5Au16(Au/In)6 (Eu5Au17.29In4.71(3)) (III) have been synthesized, and their structures were characterized by single-crystal X-ray diffraction. I and II crystallize with the CeCu2-type (Pearson Symbol oI12; Imma; Z = 4; a = 4.9018(4) Å; b = 7.8237(5) Å; c = 8.4457(5) Å) and the YbAl4Mo2-type (tI14; I4/mmm; Z = 2; a = 7.1612(7) Å; c = 5.5268(7) Å) and exhibit significant Au/In disorder. I is composed of an Au/In-mixed diamond-related host lattice encapsulating Eu atoms, while the structure of II features ribbons of distorted, squared Au8 prisms enclosing Eu, Au, and In atoms. Combination of these structural motifs leads to a new structure type as observed for Eu5Au16(Au/In)6 (Eu5Au17.29In4.71(3)) (oS108; Cmcm; Z = 4; a = 7.2283(4) Å; b = 9.0499(6) Å; c = 34.619(2) Å), which formally represents a one-dimensional intergrowth of the series EuAu2–“EuAu4In2”. The site preferences of the disordered Au/In positions in II were investigated for different hypothetical “EuAu4(Au/In)2” models using the projector-augmented wave method and indicate that these structures attempt to optimize the frequencies of the heteroatomic Au–In contacts. Furthermore, a chemical bonding analysis on two “EuAu5In” and “EuAu4In2” models employed the TB-LMTO-ASA method and reveals that the subtle interplay between the local atomic environments and the bond energies determines the structural and site preferences for these systems.

  19. Intracellular distribution of TM4SF1 and internalization of TM4SF1-antibody complex in vascular endothelial cells

    SciTech Connect

    Sciuto, Tracey E.; Merley, Anne; Lin, Chi-Iou; Richardson, Douglas; Liu, Yu; Li, Dan; Dvorak, Ann M.; Dvorak, Harold F.; Jaminet, Shou-Ching S.

    2015-09-25

    Transmembrane-4 L-six family member-1 (TM4SF1) is a small plasma membrane-associated glycoprotein that is highly and selectively expressed on the plasma membranes of tumor cells, cultured endothelial cells, and, in vivo, on tumor-associated endothelium. Immunofluorescence microscopy also demonstrated TM4SF1 in cytoplasm and, tentatively, within nuclei. With monoclonal antibody 8G4, and the finer resolution afforded by immuno-nanogold transmission electron microscopy, we now demonstrate TM4SF1 in uncoated cytoplasmic vesicles, nuclear pores and nucleoplasm. Because of its prominent surface location on tumor cells and tumor-associated endothelium, TM4SF1 has potential as a dual therapeutic target using an antibody drug conjugate (ADC) approach. For ADC to be successful, antibodies reacting with cell surface antigens must be internalized for delivery of associated toxins to intracellular targets. We now report that 8G4 is efficiently taken up into cultured endothelial cells by uncoated vesicles in a dynamin-dependent, clathrin-independent manner. It is then transported along microtubules through the cytoplasm and passes through nuclear pores into the nucleus. These findings validate TM4SF1 as an attractive candidate for cancer therapy with antibody-bound toxins that have the capacity to react with either cytoplasmic or nuclear targets in tumor cells or tumor-associated vascular endothelium. - Highlights: • Anti-TM4SF1 antibody 8G4 was efficiently taken up by cultured endothelial cells. • TM4SF1–8G4 internalization is dynamin-dependent but clathrin-independent. • TM4SF1–8G4 complexes internalize along microtubules to reach the perinuclear region. • Internalized TM4SF1–8G4 complexes pass through nuclear pores into the nucleus. • TM4SF1 is an attractive candidate for ADC cancer therapy.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  1. Visible to infrared energy conversion in Pr3+-Yb3+ co-doped fluoroindate glasses

    NASA Astrophysics Data System (ADS)

    Borrero-Gonzlez, L. J.; Galleani, G.; Manzani, D.; Nunes, L. A. O.; Ribeiro, S. J. L.

    2013-10-01

    Processes involving visible to infrared energy conversion are presented for Pr3+-Yb3+ co-doped fluoroindate glasses. The emission in the visible and infrared regions, the luminescence decay time of the Pr3+:3P0 ? 3H4 (482 nm), Pr3+:1D2 ? 3H6 (800 nm), Yb3+:2F5/2 ? 2F7/2 (1044 nm) transitions and the photoluminescence excitation spectra were measured in Pr3+ samples and in Pr3+-Yb3+ samples as a function of the Yb3+ concentration. In addition, energy transfer efficiencies were estimated from Pr3+:3P0 and Pr3+:1D2 levels to Yb3+:2F7/2 level. Down-Conversion (DC) emission is observed due to a combination of two different processes: 1-a one-step cross relaxation (Pr3+:3P0 ? 1G4; Yb3+:2F7/2 ? 2F5/2) resulting in one photon emitted by Pr3+ (1G4 ? 3H5) and one photon emitted by Yb3+ (2F7/2 ? 2F5/2); 2-a resonant two-step first order energy transfer, where the first part of energy is transferred to Yb3+ neighbor through cross relaxation (Pr3+:3P0 ? 1G4; Yb3+:2F7/2 ? 2F5/2) followed by a second energy transfer step (Pr3+:1G4 ? 3H4; Yb3+:2F7/2 ? 2F5/2). A third process leading to one IR photon emission to each visible photon absorbed involves cross relaxation energy transfer (Pr3+:1D2 ? 3F4; Yb3+:2F7/2 ? 2F5/2).

  2. Single crystal growth of a new YB{sub 50} family compound: YB{sub 44}Si{sub 1.0}

    SciTech Connect

    Tanaka, Takaho; Ishizawa, Yoshio; Okada, Shigeru

    1997-10-01

    Single crystals of a new yttrium borosilicide of YB{sub 44}Si{sub 1.0} have been grown by the floating zone method using a xenon lamp image furnace. X-ray powder diffraction, precession photography, and chemical analyses showed that the crystal obtained is a new YB{sub 50} family yttrium borosilicide which has a composition of YB{sub 44.4}Si{sub 1.04} in the middle part of the crystal and an orthorhombic crystal structure with space group Pbam or Pba2.

  3. Identification of the tropomyosin (HL-Tm) in Haemaphysalis longicornis.

    PubMed

    Tian, Meiyuan; Tian, Zhancheng; Luo, Jin; Xie, Junren; Yin, Hong; Zeng, Qiaoying; Shen, Hui; Chai, Huiping; Yuan, Xiaosong; Wang, Fangfang; Liu, Guangyuan

    2015-01-30

    Haemaphysalis longicornis tropomyosin (HL-Tm) was amplified by RT-PCR. The cDNA contained a 825 bp open reading frame coding for 274 amino acids with a predicted theoretical isoelectric point (pI) of 4.55 and molecular weight of 31.7 kDa. Real-time RT-PCR analysis showed that the expression levels of the HL-Tm in the unfed-females were significantly higher than in other tested developmental stages (eggs, unfed-larvae and unfed-nymphs). Western blot analysis showed that rabbit anti-serum against H. longicornis unfed-adult ticks recognized the recombinant HL-Tm protein (rHL-Tm). Immunization of rabbits with the rHL-Tm resulted in a statistically significant reduction of female engorgement and oviposition. Silencing of HL-Tm by RNAi showed a decrease in tick engorgement and oviposition, which is consistent with the effect of recombinant protein vaccine on the adults. These results showed that tick HL-Tm might be involved in the regulation of ticks blood-feeding, growth and oviposition. PMID:25535026

  4. Laser excited long lasting luminescence in CaAl?O?: Eu?/Eu?+Nd? phosphor.

    PubMed

    Kumar, K; Singh, A K; Rai, S B

    2013-02-01

    The europium and neodymium oxides doped nano-structured calcium aluminate phosphor samples have prepared through combustion technique and their luminescence properties are studied using laser excitations. Samples prepared in open atmosphere showed the presence of both Eu(3+) and Eu(2+) states and their ratio changes with calcination temperature. Single Eu(3+)/Eu(2+) ions doped sample has found to give broad emission at 450 nm without the persistence glow while the Eu(3+)+Nd(3+) ions codoped sample has shown persistence glow at 450 nm (Eu(2+)) on 355 nm laser excitation. Wavelength selective excitations show that 266 nm excitation gives the intense emissions from both Eu(3+) and Eu(2+) states with no afterglow but 355 nm excitation gives negligible emission from Eu(3+) ions and a strong afterglow at 450 nm wavelength. The mechanism of wavelength dependent phosphorescence has been discussed. Studies on Stark splittings and their relative intensities in emission spectra of Eu(3+) ions have shown that Eu(3+) ion can be used as excellent probe of crystal structure. PMID:23220659

  5. Measurements of isotope shift in Eu II

    NASA Astrophysics Data System (ADS)

    Broström, Lars; Mannervik, Sven; Royen, Peder; Wännström, Anders

    1995-03-01

    The isotope shift between singly-charged 151Eu and 153Eu in the 4f7(8So)6s 9So4 - 4f7(8So)6p1/2 J = 4 transition at 4129 Å has been measured using fast ion beam-laser technique. This Eu line has attracted interest in connection with efforts of obtaining a cosmochronometer based on observed Th/Eu abundance ratios. Knowledge of the isotope shift is of importance in order to check that contaminations from line blends do not contribute to the line intensity of Eu II. The measured value of the isotope shift -0.1527 (2) cm-1 is consistent with the old spectroscopic value of Krebs and Winkler (-0.1503 (25)cm-1) using a Fabry-Perot interferometer, while the accuracy is improved substantially.

  6. Tm:germanate Fiber Laser: Tuning And Q-switching

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.; Walsh, Brian M.; Reichle, Donald J.; DeYoung, R. J.; Jiang, Shibin

    2007-01-01

    A Tm:germanate fiber laser produced >0.25 mJ/pulse in a 45 ns pulse. It is capable of producing multiple Q-switched pulses from a single p ump pulse. With the addition of a diffraction grating, Tm:germanate f iber lasers produced a wide, but length dependent, tuning range. By s electing the fiber length, the tuning range extends from 1.88 to 2.04 ?m. These traits make Tm:germanate lasers suitable for remote sensin g of water vapor.

  7. Quasi four-level Tm:LuAG laser

    NASA Technical Reports Server (NTRS)

    Jani, Mahendra G. (Inventor); Barnes, Norman P. (Inventor); Hutcheson, Ralph L. (Inventor); Rodriguez, Waldo J. (Inventor)

    1997-01-01

    A quasi four-level solid-state laser is provided. A laser crystal is disposed in a laser cavity. The laser crystal has a LuAG-based host material doped to a final concentration between about 2% and about 7% thulium (Tm) ions. For the more heavily doped final concentrations, the LuAG-based host material is a LuAG seed crystal doped with a small concentration of Tm ions. Laser diode arrays are disposed transversely to the laser crystal for energizing the Tm ions.

  8. Review of Tm and Ho Materials; Spectroscopy and Lasers

    NASA Technical Reports Server (NTRS)

    Walsh, Brian M.

    2008-01-01

    A review of Tm and Ho materials is presented, covering some fundamental aspects on the spectroscopy and laser dynamics in both single and co-doped systems. Following an introduction to 2- m lasers, applications and historical development, the physics of quasi-four level lasers, energy transfer and modeling are discussed in some detail. Recent developments in using Tm lasers to pump Ho lasers are discussed, and seen to offer some advantages over conventional Tm:Ho lasers. This article is not intended as a complete review, but as a primer for introducing concepts and a resource for further study.

  9. Stimulated Raman adiabatic passage in Tm{sup 3+}:YAG

    SciTech Connect

    Alexander, A. L.; Lauro, R.; Louchet, A.; Chaneliere, T.; Le Goueet, J. L.

    2008-10-01

    We report on the experimental demonstration of stimulated Raman adiabatic passage in a Tm{sup 3+}:YAG crystal. Tm{sup 3+}:YAG is a promising material for use in quantum information processing applications, but as yet there are few experimental investigations of coherent Raman processes in this material. We investigate the effect of inhomogeneous broadening and Rabi frequency on the transfer efficiency and the width of the two-photon spectrum. Simulations of the complete Tm{sup 3+}:YAG system are presented along with the corresponding experimental results.

  10. Optical in-situ study of the oxidation and reduction kinetics of Yb-substituted YAG epitaxial films

    NASA Astrophysics Data System (ADS)

    Martynyuk, N. V.; Ubizskii, S. B.; Buryy, O. A.; Becker, K. D.; Kreye, M.

    2005-01-01

    The optical spectra of the Yb-substituted Yb3Al5O12 (YAG) epitaxial films and the Yb ions recharging kinetics have been investigated by means of in-situ optical spectroscopy in the temperature range between 900 and 1100 C at oxidation and reduction condition. This work continues the studies of the spectral properties of Yb:YAG epitaxial films represented in [1] and optical in-situ study of the re-oxidation kinetics of Yb3Al5O12 (YbAG) crystal represented in [2] where the model of internal oxidation of ytterbium ions Yb2+ Yb3+ in the bulk crystal was developed and proofed. The changes of the absorption spectra of Yb:YAG film during oxidation and reduction were attributed to the recharging process Yb3+ Yb2+. It was found that the oxidation kinetics in epitaxial films do not agree to the model [2] and do not follow a parabolic rate law in contrary to bulk YbAG single crystal.

  11. Preparation, Biological Evaluation and Dosimetry Studies of 175Yb-Bis-Phosphonates for Palliative Treatment of Bone Pain

    PubMed Central

    Fakhari, Ashraf; Jalilian, Amir R.; Yousefnia, Hassan; Shanehsazzadeh, Saeed; Samani, Ali Bahrami; Daha, Fariba Johari; Ardestani, Mehdi Shafiee; Khalaj, Ali

    2015-01-01

    Objective: Optimized production and quality control of ytterbium-175 (Yb-175) labeled pamidronate and alendronate complexes as efficient agents for bone pain palliation has been presented. Methods: Yb-175 labeled pamidronate and alendronate (175Yb-PMD and 175Yb-ALN) complexes were prepared successfully at optimized conditions with acceptable radiochemical purity, stability and significant hydroxyapatite absorption. The biodistribution of complexes were evaluated up to 48 h, which demonstrated significant bone uptake ratios for 175Yb-PAM at all-time intervals. It was also detected that 175Yb-PAM mostly washed out and excreted through the kidneys. Results: The performance of 175Yb-PAM in an animal model was better or comparable to other 175Yb-bone seeking complexes previously reported. Conclusion: Based on calculations, the total body dose for 175Yb-ALN is 40% higher as compared to 175Yb-PAM (especially kidneys) indicating that 175Yb-PAM is probably a safer agent than 175Yb-ALN.

  12. Magnetic properties and 151Eu Mssbauer effect studied in Eu-Ga and Eu-Sn intermetallic compounds

    NASA Astrophysics Data System (ADS)

    De Vries, J. W. C.; Thiel, R. C.; Buschow, K. H. J.

    1985-04-01

    An investigation of the magnetic properties of various intermetallic Eu-Ga and Eu-Sn compounds is reported. It is shown that in the paramagnetic regime the magnetic properties behave in accordance with the Curie-Weiss law and the effective moments are close to the value expected for europium in the divalent state. All these compounds give rise to antiferromagnetic ordering at low temperatures. Metamagnetic behaviour was found in Eu 3Ga 8 and in the low-temperature phase of EuGa 2. From the lattice constants determined for all compounds investigated values were derived for the volume contraction associated with compound formation. These volume contractions are discussed in terms of Miedema's semi-empirical model. The values of the 151Eu isomer shift were analysed by means of the Miedema and Van der Woude model after applying a correction term related to the volume contraction. For all Eu-Ga compounds the 151Eu hyperfine fields at 4.2 K were determined.

  13. Coinage metals binding as main group elements: structure and bonding of the carbene complexes [TM(cAAC)2] and [TM(cAAC)2](+) (TM = Cu, Ag, Au).

    PubMed

    Jerabek, Paul; Roesky, Herbert W; Bertrand, Guy; Frenking, Gernot

    2014-12-10

    Quantum chemical calculations using density functional theory have been carried out for the cyclic (alkyl)(amino)carbene (cAAC) complexes of the group 11 atoms [TM(cAAC)2] (TM = Cu, Ag, Au) and their cations [TM(cAAC)2](+). The nature of the metal-ligand bonding was investigated with the charge and energy decomposition analysis EDA-NOCV. The calculations show that the TM-C bonds in the charged adducts [TM(cAAC)2](+) are significantly longer than in the neutral complexes [TM(cAAC)2], but the cations have much higher bond dissociation energies than the neutral molecules. The intrinsic interaction energies ?Eint in [TM(cAAC)2](+) take place between TM(+) in the (1)S electronic ground state and (cAAC)2. In contrast, the metal-ligand interactions in [TM(cAAC)2] involve the TM atoms in the excited (1)P state yielding strong TM p(?) ? (cAAC)2 ? backdonation, which is absent in the cations. The calculations suggest that the cAAC ligands in [TM(cAAC)2] are stronger ? acceptors than ? donors. The trends of the intrinsic interaction energies and the bond dissociation energies of the metal-ligand bonds in [TM(cAAC)2] and [TM(cAAC)2](+) give the order Au > Cu > Ag. Calculations at the nonrelativistic level give weaker TM-C bonds, particularly for the gold complexes. The trend for the bond strength in the neutral and charged adducts without relativistic effects becomes Cu > Ag > Au. The EDA-NOCV calculations suggest that the weaker bonds at the nonrelativistic level are mainly due to stronger Pauli repulsion and weaker orbital interactions. The NBO picture of the C-TM-C bonding situation does not correctly represent the nature of the metal-ligand interactions in [TM(cAAC)2]. PMID:25394669

  14. Effect of Yb3+ concentration on photoluminescence properties of cubic Gd2O3 phosphor

    NASA Astrophysics Data System (ADS)

    Tamrakar, Raunak Kumar; Bisen, D. P.; Brahme, Nameeta

    2015-01-01

    Yb3+ doped phosphor of Gd2O3 (Gd2O3:Yb3+) have been prepared by solid state reaction method. The structure and the particle size have been determined by X-ray powder diffraction measurements. The average particle size of the phosphor is in between 35 and 50 nm. The particle size and structure of the phosphor was further confirmed by TEM analysis. The visible and NIR luminescence spectra were recorded under the 980 nm laser excitation. The visible upconversion luminescence of Yb3+ ion was due to cooperative luminescence and the presence of rare earth impurity ions. The cooperative upconversion and NIR luminescence spectra as a function of Yb3+ ion concentration were measured and the emission intensity variation with Yb3+ ion concentration was discussed. Yb3+ energy migration quenched the cooperative luminescence of Gd2O3:Yb3+ phosphor with doping level over 5%, while the NIR emission luminescence continuously increases with increasing Yb3+ ion concentration.

  15. YB-1 ALTERS MT1-MMP TRAFFICKING AND STIMULATES MCF-7 BREAST TUMOR INVASION AND METASTASIS

    PubMed Central

    Lovett, David H.; Cheng, Sunfa; Cape, Leslie; Pollock, Allan S.; Mertens, Peter R.

    2010-01-01

    YB-1 is a member of the cold shock domain family, with complex roles in DNA structure, gene transcription and translation. YB-1 promotes chromosomal instability, and mammary gland transgenic expression induces tumors with 100% penetrance. YB-1 is linked to poor prognosis in breast carcinoma and is a strong predictor of relapse and disease-specific survival. Survival is directly tied to the extent of local invasion and distal metastasis, processes dependent upon the activity of the membrane type I-matrix metalloproteinase, MT1-MMP. Non-invasive MCF-7 breast adenocarcinoma cells were transfected with YB-1/EGFP. YB-1 protein was detected in the invadopodia of cells with a migratory phenotype. There was increased expression of MT1-MMP protein concentrated at the leading edges of motile cells, which were highly invasive in collagen three-dimensional culture. The rates of MT1-MMP protein endocytosis and recycling to the cell surface were elevated in clones expressing higher levels of YB-1 protein. Control MCF-7 cells formed nonfatal, noninvasive, differentiated adenocarcinomas in vivo. MCF-7 cells expressing a two-fold increase in YB-1 formed highly anaplastic tumors with local invasion, pulmonary metastases and high lethality. We conclude that YB-1 contributes to the development of an invasive, metastatic breast carcinoma phenotype by enhanced presentation of MT1-MMP at the sites of cellular invasion. PMID:20599698

  16. Roles of critical valence fluctuations in Ce-and Yb-based heavy fermion metals.

    PubMed

    Watanabe, Shinji; Miyake, Kazumasa

    2011-03-01

    The roles of critical valence fluctuations of Ce and Yb are discussed as a key origin of several anomalies observed in Ce- and Yb-based heavy fermion systems. Recent development of the theory has revealed that a magnetic field is an efficient control parameter to induce the critical end point of the first-order valence transition. Metamagnetism and non-Fermi liquid behavior caused by this mechanism are discussed by comparing favorably with CeIrIn5, YbAgCu4 and YbIr2Zn20. The interplay of the magnetic order and valence fluctuations offers a key concept for understanding Ce- and Yb-based systems. It is shown that suppression of the magnetic order by enhanced valence fluctuations gives rise to the coincidence of the magnetic-transition point and valence crossover point at absolute zero as a function of pressure or magnetic field. The interplay is shown to resolve the outstanding puzzle in CeRhIn5 in a unified way. The broader applicability of this newly clarified mechanism is discussed by surveying promising materials such as YbAuCu4, ?-YbAlB4 and YbRh2Si2. PMID:21339570

  17. Tuning the Kondo effect in YbFe1-xCoxZn20

    NASA Astrophysics Data System (ADS)

    Kong, Tai; Taufour, Valentin; Bud'Ko, Sergey; Canfield, Paul

    2015-03-01

    YbCo2Zn20 is a heavy fermion compound with a Sommerfeld coefficient, ? value, of about 8000 mJ/mol-K2 with an estimated single ion Kondo temperature, TK, of about 1.5 K. One the other hand, YbFe2Zn20 is less heavy with ? ~ 500 mJ/mol-K2 and TK ~ 30 K. From a generalized Kadowaki-Woods picture, degeneracies that relate to their Kondo phenomena are large while different: 8 for YbFe2Zn20 and 4 for YbCo2Zn20. In order to understand the effects of Fe-Co substitution on the Kondo effect, a family of YbFe1-xCoxZn20 were studied. We performed zero-field resistivity and specific heat measurements on single crystals of YbFe1-xCoxZn20 that were synthesized using a high-temperature solution growth technique. The Kondo characteristic temperatures do not change monotonically in between pure YbFe2Zn20andYbCo2Zn20. Data and a summarize phase diagram of characteristic temperatures as a function of Co doping will be presented and discussed. This work is supported by the US DOE, Basic Energy Sciences under Contract No. DE-AC02-07CH11358.

  18. Photoelectron spectra of thulium atoms encapsulated C82 fullerene, Tm2@C82 (III) and Tm2C2@C82 (III)

    NASA Astrophysics Data System (ADS)

    Miyazaki, Takafumi; Tokumoto, Youji; Sumii, Ryohei; Yagi, Hajime; Izumi, Noriko; Shinohara, Hisanori; Hino, Shojun

    2014-03-01

    Ultraviolet photoelectron spectra (UPS) and X-ray photoelectron spectra (XPS) of two thulium atoms and thulium-carbide cluster entrapped fullerenes, Tm2@C82 (III) and Tm2C2@C82 (III), were measured using synchrotron radiation and MgK? X-ray light sources. The UPS spectral onset energy of these endohedral fullerenes is around 0.9 eV, which is smaller than that of 1.2 eV of empty C82. The UPS of Tm2@C82 (III) and Tm2C2@C82 (III) resemble each other. Further, the UPS of Tm2@C82 (III), Y2@C82-C3v and Er2@C82-C3v are almost identical and as well as are Tm2C2@C82 (III), Y2C2@C82-C3v and Er2C2@C82-C3v. The XPS Tm4d5/2 peaks of Tm2@C82 and Tm2C2@C82 appear at higher binding energy region than that of Tm@C82, which suggests the oxidation states of Tm atoms in Tm2@C82 (III) and Tm2C2@C82 are higher than that in Tm@C82.

  19. ASTROCULTURE (TM) root metabolism and cytochemical analysis

    NASA Technical Reports Server (NTRS)

    Porterfield, D. M.; Barta, D. J.; Ming, D. W.; Morrow, R. C.; Musgrave, M. E.

    2000-01-01

    Physiology of the root system is dependent upon oxygen availability and tissue respiration. During hypoxia nutrient and water acquisition may be inhibited, thus affecting the overall biochemical and physiological status of the plant. For the Astroculture (TM) plant growth hardware, the availability of oxygen in the root zone was measured by examining the changes in alcohol dehydrogenase (ADH) activity within the root tissue. ADH activity is a sensitive biochemical indicator of hypoxic conditions in plants and was measured in both spaceflight and control roots. In addition to the biochemical enzyme assays, localization of ADH in the root tissue was examined cytochemically. The results of these analyses showed that ADH activity increased significantly as a result of spaceflight exposure. Enzyme activity increased 248% to 304% in dwarf wheat when compared with the ground controls and Brassica showed increases between 334% and 579% when compared with day zero controls. Cytochemical staining revealed no differences in ADH tissue localization in any of the dwarf wheat treatments. These results show the importance of considering root system oxygenation in designing and building nutrient delivery hardware for spaceflight plant cultivation and confirm previous reports of an ADH response associated with spaceflight exposure.

  20. Long-Range Magnetic Ordering in Pyrochlore Iridate Eu2Ir2O7

    NASA Astrophysics Data System (ADS)

    Zhao, S.; Mackie, J. M.; Maclaughlin, D. E.; Bernal, O. O.; Ohta, Y.; Nakatsuji, S.

    2010-03-01

    In the pyrochlore iridate Eu2Ir2O7 [1,,] Eu^3+ is nonmagnetic (L = S, J = 0) and S(Ir^4+) = 1/2 [1], so that it is a rare example of a frustrated S=1/2 pyrochlore. Spin-glass-like behavior at the metal-insulator transition (MIT) and no magnetic ordering down to 0.3 K have been reported for this compound [2,,]. We discuss ?SR measurements on Eu2Ir2O7 polycrystalline samples that yield strong evidence for long-range magnetic ordering. We observe well-defined muon spin precession frequencies below TM 120 K, consistent with the MIT temperature [2] but indicating long-range ordering instead of a spin-glass like transition. Significant dynamic muon spin relaxation persists to low temperatures, as is often the case in frustrated antiferromagnets. Work supported by NSF (U.S.), Grants 0801407 (UCR) and 0604105 (CSULA), and MEXT (Japan), Grants-in-Aid Nos. 17071003 and 19052003. [1] B. J. Kim et al., Phys. Rev.Lett. 101, 076402 (2008). [2] N. Taira et al., J. Phys.: Condens. Matter 13, 5527 (2001). [3] C. L. Chien and A. W. Sleight, Phys. Rev. B 18, 2031 (1978).

  1. First-principles study of one-dimensional sandwich wires [(P)?TM]? (TM = Ti, V, Cr, Mn, Fe, Co).

    PubMed

    Ma, Yandong; Dai, Ying; Li, Xinru; Li, Zhujie; Huang, Baibiao

    2013-10-01

    Since the discovery of ferrocene, many one-dimensional metallic sandwich molecular wires have been identified. However, most of the known systems are assembled from organic molecules. Suffering from many drawbacks has, however, hampered their widespread applications. With the goal of breaking this logjam, we provide a blueprint for the designing of a variety of novel sandwich molecular wires ([(P)5TM]?, TM = Ti, V, Cr, Mn, Fe, and Co) assembled from ferrocene-like inorganic molecules (P)5TM, offering evidence of the existence of inorganic molecular wires in this class. We present first-principles calculations to investigate systematically the electronic and magnetic properties of such novel inorganic sandwich molecular wires. Compared with the organic molecular wires, all the inorganic [(P)5TM]? wires are of large magnetic moment. Among them, we find that [(P)5V]?, [(P)5Cr]? and [(P)5Mn]? display ferromagnetic character, while for [(P)5Ti]?, [(P)5Fe]? and [(P)5Co]?, the magnetic coupling is antiferromagnetic. More remarkably, the TM atoms distributed in these wires show regular docking and lead to structures with ordered spin signals, which is a long-term dream of spintronics. We propose that the difference in magnetic coupling for the studied systems is related to the competition between two exchange interactions of TM atoms. Specifically, we propound that the general mechanism for the formation of stable 1D [(P)5TM]? involves the transfer of one electron from the TM atom to the P5 ligand forming [Formula: see text] and TM(+) alternating structure. PMID:24002217

  2. First-principles study of one-dimensional sandwich wires [(P)5TM]? (TM = Ti, V, Cr, Mn, Fe, Co)

    NASA Astrophysics Data System (ADS)

    Ma, Yandong; Dai, Ying; Li, Xinru; Li, Zhujie; Huang, Baibiao

    2013-10-01

    Since the discovery of ferrocene, many one-dimensional metallic sandwich molecular wires have been identified. However, most of the known systems are assembled from organic molecules. Suffering from many drawbacks has, however, hampered their widespread applications. With the goal of breaking this logjam, we provide a blueprint for the designing of a variety of novel sandwich molecular wires ([(P)5TM]?, TM = Ti, V, Cr, Mn, Fe, and Co) assembled from ferrocene-like inorganic molecules (P)5TM, offering evidence of the existence of inorganic molecular wires in this class. We present first-principles calculations to investigate systematically the electronic and magnetic properties of such novel inorganic sandwich molecular wires. Compared with the organic molecular wires, all the inorganic [(P)5TM]? wires are of large magnetic moment. Among them, we find that [(P)5V]?, [(P)5Cr]? and [(P)5Mn]? display ferromagnetic character, while for [(P)5Ti]?, [(P)5Fe]? and [(P)5Co]?, the magnetic coupling is antiferromagnetic. More remarkably, the TM atoms distributed in these wires show regular docking and lead to structures with ordered spin signals, which is a long-term dream of spintronics. We propose that the difference in magnetic coupling for the studied systems is related to the competition between two exchange interactions of TM atoms. Specifically, we propound that the general mechanism for the formation of stable 1D [(P)5TM]? involves the transfer of one electron from the TM atom to the P5 ligand forming ({P})_{5}^{-} and TM+ alternating structure.

  3. Luminescence studies on Dy3+ and Dy3+:Eu3+ co-doped boro-phosphate glasses for WLED applications

    NASA Astrophysics Data System (ADS)

    Vijayakumar, M.; Uma, V.; Arunkumar, S.; Marimuthu, K.

    2015-06-01

    Dy3+ and Dy3+:Eu3+ co-doped boro-phosphate glasses have been prepared and optically characterized using absorption, luminescence and decay measurements. The Nephelauxetic ratios (?), Bonding parameters (?) and Judd-Ofelt (JO) intensity parameters ?? (? = 2, 4 and 6) were calculated to study the nature of the environment around the RE3+ ions in the prepared glasses. The yellow to blue (Y/B) intensity ratio and the chromaticity color coordinates were calculated from the luminescence measurements. The lifetimes of the 4F9/2 excited level were measured using decay curves and is found to decrease in the Dy3+:Eu3+ co-doped glass due to the occurrence of resonant energy transfer between Dy3+-Eu3+ ions and the non-exponential decay rates have been fitted with Inokuti-Hirayama (IH) model. The decay curves are well fitted for S= 6 suggesting that the interaction between active ions for the energy transfer is of dipole-dipole nature.

  4. Formation of Yb nBa 2 nCu 3 n+1 O x ( n=3, 4) by oxidation of Yb?Ba?Cu?Ag metallic precursors

    NASA Astrophysics Data System (ADS)

    Kogure, T.; Otto, A.; Vander Sande, J. B.

    1989-01-01

    New structural variations on the 1-2-3 type high- Tc superconducting phase have been identified in oxidized Yb?Ba?Cu?Ag metallic precursors in which Yb 2Ba 4Cu 7O x (2-4-7) and Ag are the dominant phases. These new structures are generated by the placement of the copper oxide double layer in every three unit cells of the 1-2-3 structure yielding the chemical composition Yb 3Ba 6Cu 10O x or in every four unit cells yielding Yb 4Ba 8Cu 13O x. These discoveries lead to the conclusion that a large family of superconductors exists whose generic formula is Re nBa 2 nCu 3 n+1 O x, where Re represents rare-earth elements and n is between 1 and ? ( n=? generates the 1-2-3 phase).

  5. Enhancement of Tb-Yb quantum cutting emission by inverse opal photonic crystals

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Qiu, Jianbei; Song, Zhiguo; Yang, Zhengwen; Yin, Zhaoyi; Zhou, Dacheng; Wang, Siqin

    2016-04-01

    Yb3+, Tb3+ co-doped YPO4 inverse opal photonic crystal was prepared directly by sol-gel technique in combination with self-assembly method. With the influence of the photonic band gap, quantum cutting emission of Tb3+, Yb3+ was investigated in photonic crystals by photoluminescence and fluorescence lifetime. The result clearly shows that, when the spontaneous emission of donor Tb3+ is inhibited by photonic band gap, Tb3+-Yb3+ quantum cutting quantum efficiency from Tb3+ to Yb3+ could be enhanced from 131.2% to 140.5%. The mechanisms for the influence of the photonic band gap on quantum cutting process of Tb3+ and Yb3+ are discussed. We believe that the present work will be valuable for the foundational study of quantum cutting energy transfer process and application of quantum cutting optical devices in spectral modification materials for silicon solar cells.

  6. Site-selective 11B NMR studies on YbAlB4

    NASA Astrophysics Data System (ADS)

    Takano, S.; Grbic, M. S.; Kimura, K.; Yoshida, M.; Takigawa, M.; Farrell, E. C. T. O.; Kuga, K.; Nakatsuji, S.; Harima, H.

    2016-02-01

    ?-YbAlB4 is a distinctive heavy fermion superconductor that exhibits unconventional quantum criticality without tuning in a strongly intermediate valence state. In this paper, we report the result of 11B NMR measurements on the single crystals of, ?-YbAlB4 and ?- YbAlB4, the locally isostructural polymorph of ?-YbAlB4. All 11B NMR lines for both samples were successfully assigned to inequivalent crystallographic sites by comparing the experimental results and the ab-initio calculation of the electric field gradient. In both compounds, the anisotropy of the Knight shift exhibits a characteristic radial pattern, indicating approximate axial symmetry of the hybridization between the Yb-4f electrons and the conduction electrons.

  7. Output characteristics of high power cryogenic Yb:YAG TRAM laser oscillator.

    PubMed

    Furuse, Hiroaki; Kawanaka, Junji; Miyanaga, Noriaki; Chosrowjan, Haik; Fujita, Masayuki; Takeshita, Kenji; Izawa, Yasukazu

    2012-09-10

    We analyzed the output power characteristics of a cryogenically cooled Yb:YAG total-reflection active-mirror (TRAM) laser oscillator including the temperature dependence of the emission cross section and the reabsorption loss of the Yb:YAG TRAM. A CW multi-transverse mode oscillation of a 9.8 at.% doped 0.6 mm thick Yb:YAG ceramic TRAM was investigated for various pump spot sizes and compared with theoretical results. The Yb:YAG temperatures were inferred from the ratio between fluorescence intensities at 1022 nm and 1027 nm which varied significantly with temperature below 200 K. Output power calculations using evaluated temperatures were in good agreement with the experimental data measured between 77 and 200 K, and the output power suppression due to the temperature rise observed above ~140 K. To the best of our knowledge, this is the first evaluation of output power for a cryogenically cooled Yb:YAG TRAM laser. PMID:23037293

  8. Fabrication and characterization of highly transparent Yb3+: Y2O3 ceramics

    NASA Astrophysics Data System (ADS)

    Ning, Kaijie; Wang, Jun; Luo, Dewei; Ma, Jie; Zhang, Jian; Dong, Zhi Li; Kong, Ling Bing; Tang, Ding Yuan

    2015-12-01

    Highly transparent Yb3+ doped Y2O3 (Yb3+: Y2O3) ceramics was fabricated by a solid-state reaction method using ZrO2 and La2O3 as additives. The morphology of the prepared powder was investigated and the phase of the sintered Yb3+: Y2O3 ceramics sample was identified. The microstructure, transmittance spectrum, Vickers hardness and fracture toughness for the as-sintered Yb3+: Y2O3 ceramics were measured. The average grain size was about 9.11 ?m and the transmittance at the wavelength of 2000 nm was about 82.0%, which was 99% of the theoretical value. ZrO2 and La2O3 were useful additives for highly transparent Yb3+: Y2O3 ceramics fabrication and mechanical properties improvement.

  9. Resonant tandem pumping of Tm-doped fiber lasers

    NASA Astrophysics Data System (ADS)

    Creeden, Daniel; Johnson, Benjamin R.; Rines, Glen A.; Setzler, Scott D.

    2014-06-01

    We have demonstrated efficient lasing of a Tm-doped fiber when pumped with another Tm-doped fiber. In these experiments, we use a 1908 nm Tm-doped fiber laser as a pump source for another Tm-doped fiber laser, operating at a slightly longer wavelength (~2000 nm). Pumping in the 1900 nm region allows for very high optical efficiencies, low heat generation, and significant power scaling potential due to the use of fiber laser pumping. The trade-off is that the ground-state pump absorption at 1908 nm is ~37 times lower than at 795nm. However, the absorption cross-section is still sufficiently high enough to achieve effective pump absorption without exceedingly long fiber lengths. This may also be advantageous for distributing the thermal load in higher power applications.

  10. Spiral Bragg grating waveguides for TM mode silicon photonics.

    PubMed

    Chen, Zhitian; Flueckiger, Jonas; Wang, Xu; Zhang, Fan; Yun, Han; Lu, Zeqin; Caverley, Michael; Wang, Yun; Jaeger, Nicolas A F; Chrostowski, Lukas

    2015-09-21

    We demonstrate spiral Bragg grating waveguides (BGWs) on the silicon-on-insulator (SOI) platform for the fundamental transverse magnetic (TM) mode. We also compare TM spiral waveguides to equivalent transverse electric (TE) spiral waveguides and show that the TM spiral waveguides have lower propagation losses. Our spiral waveguides are space-efficient, requiring only areas of 131131 m(2) to accommodate 4 mm long BGWs, and, thus, are less susceptible to fabrication non-uniformities. Due to the lengths and reduced susceptibility to fabrication non-uniformities, we were able to obtain narrow bandwidth, large extinction ratio (ER) devices, as narrow as 0.09 nm and as large as 52 dB, respectively. Finally, we demonstrate a 4 mm long TM chirped spiral Bragg grating waveguide with a negative, average, group delay slope of -11 ps/nm. PMID:26406726

  11. Using the Hitachi TM 3000 in a middle school classroom

    NASA Astrophysics Data System (ADS)

    Wolfinger, Mary Ellen

    2013-05-01

    In this presentation, Mary Ellen Wolfinger explains how the Hitachi TM 3000 scanning electron microscope was used in her sixth grade science classroom to incorporate science, technology, engineering and mathematics (STEM) education.

  12. Observation of the second proton alignment in {sup 160}Tm

    SciTech Connect

    Lagergren, K.; Riley, M.A.; Campbell, D.B.; Simpson, J.; Appelbe, D.E.; Joss, D.T.; Bednarczyk, P.; Chandler, C.; Choy, P.T.W.; Paul, E.S.; Curien, D.

    2005-11-01

    High-spin states in the doubly odd nucleus {sup 160}Tm have been investigated using the {sup 130}Te({sup 35}Cl,5n) reaction and the Euroball {gamma}-ray detector array. The previously established rotational structures in {sup 160}Tm were extended, leading to the first observation of the second (h{sub 11/2}){sup 2} proton band crossing in this nucleus. This crossing is found to occur at a higher rotational frequency in {sup 160}Tm than in lighter Tm isotopes. This trend resembles that of the first (h{sub 11/2}){sup 2} proton band crossing found in neighboring Er nuclei and is associated with a predicted increase in deformation as a function of neutron number in these isotopes.

  13. Temperature dependence of Eu 4f and Eu 5d spin magnetizations in the filled skutterudite EuFe4Sb12

    SciTech Connect

    Krishnamurthy, Vemuru; Keavney, D. J.; Haskel, D.; Lang, J. C.; Srajer, G.; Sales, Brian C; Robertson, Lee; Mandrus, David

    2009-01-01

    The element specific and shell specific magnetism of Eu in the filled skutterudite ferrimagnet Eu0.95Fe4Sb12 has been investigated using Eu M4,5 and Eu L2,3 edge x-ray magnetic circular dichroism (XMCD) spectroscopy as a function of temperature. Eu L3 edge and Eu M5 edge x-ray absorption spectroscopy clearly show that Eu is in a mixed valence state. Sum rule analysis of the Eu M4,5 edge XMCD spectrum measured at 4.9K yielded the 4f spin moment of 7.15+/-0.3uB per Eu2+ ion. By comparing the Eu L2,3 edge XMCD spectrum in the ferrimagnetic state of Eu0.95Fe4Sb12 and the divalent Eu reference compound, the clathrate Eu8Ga16Ge30, we show that the 5d magnetic moment of Eu in the skutterudite is strongly enhanced by the exchange coupling with the 3d band electrons of Fe, which were shown to have an ordered moment of -0.21uB/Fe in our earlier Fe L2,3 XMCD measurements. The temperature dependence of the ferromagnetic order parameter, determined from the Eu L3 edge XMCD intensity, yields a mean field like exponent (~0.52) in the skutterudite and a 3D Heisenberg like (~0.36) exponent in the clathrate.

  14. Study of Eu{sup 3+} → Eu{sup 2+} reduction in BaAl{sub 2}O{sub 4}:Eu prepared in different gas atmospheres

    SciTech Connect

    Rezende, Marcos V. dos S.; Valerio, Mário E.G.; Jackson, Robert A.

    2015-01-15

    Highlights: • The effect of different gas atmospheres on the Eu reduction process was studied. • The Eu reduction was monitored analyzing XANES region at the Eu L{sub III}-edge. • Hydrogen reducing agent are the most appropriate gas for Eu{sup 2+} stabilization. • Only a part of the Eu ions can be stabilized in the divalent state. • A model of Eu reduction process is proposed. - Abstract: The effect of different gas atmospheres such as H{sub 2}(g), synthetic air, carbon monoxide (CO) and nitrogen (N{sub 2}) on the Eu{sup 3+} → Eu{sup 2+} reduction process during the synthesis of Eu-doped BaAl{sub 2}O{sub 4} was studied using synchrotron radiation. The Eu{sup 3+} → Eu{sup 2+} reduction was monitored analyzing XANES region when the sample are excited at the Eu L{sub III}-edge. The results show that the hydrogen reducing agent are the most appropriate gas for Eu{sup 2+} stabilization in BaAl{sub 2}O{sub 4} and that only a part of the Eu ions can be stabilized in the divalent state. A model of Eu reduction process, based on the incorporation of charge compensation defects, is proposed.

  15. Quiet Spike (TM) Build-Up Ground Vibration Testing Approach

    NASA Technical Reports Server (NTRS)

    Spivey, Natalie D.; Herrera, Claudia; Truax, Roger; Pak, Chan-gi; Freund, Donald

    2007-01-01

    Flight tests of Gulfstream Aerospace Corporation s Quiet Spike(TM) hardware were recently completed on the NASA Dryden Flight Research Center F-15B airplane. NASA Dryden uses a modified F-15B airplane as a testbed aircraft to cost-effectively fly flight research experiments that are typically mounted underneath the F-15B airplane, along the fuselage centerline. For the Quiet Spike(TM) experiment, however, instead of a centerline mounting, a relatively long forward-pointing boom was attached to the radar bulkhead of the F-15B airplane. The Quiet Spike(TM) experiment is a stepping-stone to airframe structural morphing technologies designed to mitigate the sonic-boom strength of business jets over land. The Quiet Spike(TM) boom is a concept in which an aircraft's noseboom would be extended prior to supersonic acceleration. This morphing effectively lengthens the aircraft, thus reducing the peak sonic-boom amplitude, but is also expected to partition the otherwise strong bow shock into a series of reduced-strength, noncoalescing shocklets. Prior to flying the Quiet Spike(TM) experiment on the F-15B airplane several ground vibration tests were required to understand the Quiet Spike(TM) modal characteristics and coupling effects with the F-15B airplane. However, due to the flight hardware availability and compressed schedule requirements, a "traditional" ground vibration test of the mated F-15B Quiet Spike(TM) ready-for-flight configuration did not leave sufficient time available for the finite element model update and flutter analyses before flight testing. Therefore, a "nontraditional" ground vibration testing approach was taken. This paper provides an overview of each phase of the "nontraditional" ground vibration testing completed for the Quiet Spike(TM) project which includes the test setup details, instrumentation layout, and modal results obtained in support of the structural dynamic modeling and flutter analyses.

  16. Spectroscopic and lasing properties of Ho:Tm:LuAG

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.; Filer, Elizabeth D.; Naranjo, Felipe L.; Rodriguez, Waldo J.; Kokta, Milan R.

    1993-01-01

    Ho:Tm:LuAG has been grown, examined spectroscopically, and lased at 2.1 microns. Ho:Tm:LuAG was selected for this experimental investigation when quantum-mechanical modeling predicted that it would be a good laser material for Ho laser operation on one of the 5I7 to 5I8 transitions. Lasing was achieved at 2.100 microns, one of the three wavelengths predicted to be most probable for laser action.

  17. Flashlamp-pumped Ho:Tm:Cr:LuAG laser

    NASA Technical Reports Server (NTRS)

    Jani, Mahendra G. (Inventor); Barnes, Norman P. (Inventor); Murray, Keith E. (Inventor); Kokta, Milan R. (Inventor)

    1997-01-01

    A room temperature solid-state laser is provided. A laser crystal is disposed in a laser cavity. The laser crystal has a LuAG host material doped with a concentration of about 0.35% Ho ions, about 5.57% Tm ions and at least about 1.01% Cr ions. A broadband energizing source such as a flashlamp is disposed transversely to the laser crystal to energize the Ho ions, Tm ions and Cr ions.

  18. Measurement of the 169Tm (n ,3 n ) 167Tm cross section and the associated branching ratios in the decay of 167Tm

    NASA Astrophysics Data System (ADS)

    Champine, B.; Gooden, M. E.; Krishichayan, Norman, E. B.; Scielzo, N. D.; Stoyer, M. A.; Thomas, K. J.; Tonchev, A. P.; Tornow, W.; Wang, B. S.

    2016-01-01

    The cross section for the 169Tm(n ,3 n ) 167Tm reaction was measured from 17 to 22 MeV using quasimonoenergetic neutrons produced by the 2H(d ,n ) 3He reaction. This energy range was studied to resolve the discrepancy between previous (n ,3 n ) cross-section measurements. In addition, the absolute γ -ray branching ratios following the electron-capture decay of 167Tm were measured. These results provide more reliable nuclear data for an important diagnostic that is used at the National Ignition Facility to estimate the yield of reaction-in-flight neutrons produced via the inertial-confinement-fusion plasma in deuterium-tritium capsules.

  19. Genome-wide analysis of YB-1-RNA interactions reveals a novel role of YB-1 in miRNA processing in glioblastoma multiforme.

    PubMed

    Wu, Shuai-Lai; Fu, Xing; Huang, Jinyan; Jia, Ting-Ting; Zong, Feng-Yang; Mu, Shi-Rong; Zhu, Hong; Yan, Yong; Qiu, Shuwei; Wu, Qun; Yan, Wei; Peng, Ying; Chen, Juxiang; Hui, Jingyi

    2015-09-30

    Altered miRNA expression is believed to play a crucial role in a variety of human cancers; however, the mechanisms leading to the dysregulation of miRNA expression remain elusive. In this study, we report that the human Y box-binding protein (YB-1), a major mRNA packaging protein, is a novel modulator of miRNA processing in glioblastoma multiforme (GBM). Using individual nucleotide-resolution crosslinking immunoprecipitation coupled to deep sequencing (iCLIP-seq), we performed the first genome-wide analysis of the in vivo YB-1-RNA interactions and found that YB-1 preferentially recognizes a UYAUC consensus motif and binds to the majority of coding gene transcripts including pre-mRNAs and mature mRNAs. Remarkably, our data show that YB-1 also binds extensively to the terminal loop region of pri-/pre-miR-29b-2 and regulates the biogenesis of miR-29b-2 by blocking the recruitment of microprocessor and Dicer to its precursors. Furthermore, we show that down-regulation of miR-29b by YB-1, which is up-regulated in GBM, is important for cell proliferation. Together, our findings reveal a novel function of YB-1 in regulating non-coding RNA expression, which has important implications in tumorigenesis. PMID:26240386

  20. In-Situ Growth of Yb2O3 Layer for Sublimation Suppression for Yb14MnSb11 Thermoelectric Material for Space Power Applications

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.; Opila, Elizabeth J.; Nathal, Michael V.

    2012-01-01

    The compound Yb14MnSb11 is a p-type thermoelectric material of interest to the National Aeronautics and Space Administration (NASA) as a candidate replacement for the state-of-the-art Si-Ge used in current radioisotope thermoelectric generators (RTGs). Ideally, the hot end of this leg would operate at 1000 C in the vacuum of space. Although Yb14MnSb11 shows the potential to double the value of the thermoelectric figure of merit (zT) over that of Si-Ge at 1000 C, it suffers from a high sublimation rate at elevated temperatures and would require a coating in order to survive the required RTG lifetime of 14 years. The purpose of the present work is to measure the sublimation rate of Yb14MnSb11 and to investigate sublimation suppression for this material. This paper reports on the sublimation rate of Yb14MnSb11 at 1000 C (approximately 3 x 10(exp -3) grams per square centimeter hour) and efforts to reduce the sublimation rate with an in situ grown Yb2O3 layer. Despite the success in forming thin, dense, continuous, and adherent oxide scales on Yb14MnSb11, the scales did not prove to be sublimation barriers.

  1. Genome-wide analysis of YB-1-RNA interactions reveals a novel role of YB-1 in miRNA processing in glioblastoma multiforme

    PubMed Central

    Wu, Shuai-Lai; Fu, Xing; Huang, Jinyan; Jia, Ting-Ting; Zong, Feng-Yang; Mu, Shi-Rong; Zhu, Hong; Yan, Yong; Qiu, Shuwei; Wu, Qun; Yan, Wei; Peng, Ying; Chen, Juxiang; Hui, Jingyi

    2015-01-01

    Altered miRNA expression is believed to play a crucial role in a variety of human cancers; however, the mechanisms leading to the dysregulation of miRNA expression remain elusive. In this study, we report that the human Y box-binding protein (YB-1), a major mRNA packaging protein, is a novel modulator of miRNA processing in glioblastoma multiforme (GBM). Using individual nucleotide-resolution crosslinking immunoprecipitation coupled to deep sequencing (iCLIP-seq), we performed the first genome-wide analysis of the in vivo YB-1-RNA interactions and found that YB-1 preferentially recognizes a UYAUC consensus motif and binds to the majority of coding gene transcripts including pre-mRNAs and mature mRNAs. Remarkably, our data show that YB-1 also binds extensively to the terminal loop region of pri-/pre-miR-29b-2 and regulates the biogenesis of miR-29b-2 by blocking the recruitment of microprocessor and Dicer to its precursors. Furthermore, we show that down-regulation of miR-29b by YB-1, which is up-regulated in GBM, is important for cell proliferation. Together, our findings reveal a novel function of YB-1 in regulating non-coding RNA expression, which has important implications in tumorigenesis. PMID:26240386

  2. Front-end system for Yb : YAG cryogenic disk laser

    NASA Astrophysics Data System (ADS)

    Perevezentsev, E. A.; Mukhin, I. B.; Kuznetsov, I. I.; Vadimova, O. L.; Palashov, O. V.

    2015-05-01

    A new front-end system for a cryogenic Yb : YAG laser is designed. The system consists of a femtosecond source, a stretcher and a regenerative amplifier with an output energy of 25 ?J at a pulse repetition rate of 49 kHz, a pulse duration of ~2 ns and a bandwidth of ~1.5 nm. After increasing the pump power of the regenerative amplifier, it is expected to achieve a pulse energy of ~1 mJ at the input to cryogenic amplification stages, which will allow one to obtain laser pulses with a duration of several picoseconds at the output of the cryogenic laser after compression.

  3. Characterization of Yb:YAG ceramics as laser media

    NASA Astrophysics Data System (ADS)

    Alderighi, Daniele; Pirri, Angela; Toci, Guido; Vannini, Matteo; Esposito, Laura; Costa, Anna Luisa; Piancastelli, Andreana; Serantoni, Marina

    2010-12-01

    We report the preparation and characterization of 9.8 at.% Yb 3+ doped YAG polycrystalline ceramics for laser applications. Reactive sintering of commercial powders in a clean atmosphere and under high vacuum has been used to achieve the YAG phase. The selected experimental conditions for the powder treatment, shaping and sintering are described and their influence on the optical quality of the obtained samples has been discussed. Microstructural, optical and laser characterization of the ceramics have been performed. In particular the influence of the pre-sintering (calcination) and sintering cycles has been investigated by laser characterization allowing to find unexpected loss mechanisms that cannot be revealed by standard optical characterization.

  4. Magnetostriction of the dilute amorphous alloy Yb Au

    NASA Astrophysics Data System (ADS)

    Trieu, Duong hai

    1988-11-01

    In this paper the shape magnetostriction of one percent dilute amorphous alloy of Yb in Au metal is calculated. We obtain λ ≈ -4 × 10 -5 for the case of saturated magnetization. The dominant mixing interaction ( Hmix) between the f holes and conduction holes has been taken into account. The canonical transformation is applied to the total Hamiltonian H = H0 + Hmix + Hd to obtain the expression for the magnetoelastic energy Fme. Three contributions to magnetostriction have been considered. Among them the crystal field contribution is the dominant one.

  5. Antiferromagnetic properties of EuAl 2

    NASA Astrophysics Data System (ADS)

    Wada, H.; Shiga, M.

    1994-01-01

    The magnetization, specific heat, thermal expansion and electrical resistivity have been measured for EuAl 2. Anomalies associated with the antiferromagnetic transition were observed in their temperature dependence at or below 30 K. The thermal and transport properties were analyzed by the effective Debye temperature model, in which the temperature dependence of ? D is taken into account. It is shown that the s-f exchange interaction of EuAl 2 is considerably smaller than in GdAl 2. The anomalous magnetization process of EuAl 2 is also presented and discussed.

  6. Spectral comparison of Dy, Tm and Dy/Tm in ? thermoluminescent dosimeters

    NASA Astrophysics Data System (ADS)

    Karali, T.; Rowlands, A. P.; Townsend, P. D.; Prokic, M.; Olivares, J.

    1998-03-01

    Spectrally resolved thermoluminescence of co-doped Dy:Tm:0022-3727/31/6/025/img8 shows that the maximum peak temperature for the nominal 0022-3727/31/6/025/img9C dosimetry peak differs by 0022-3727/31/6/025/img10C for Dy and Tm emission. This is interpreted as evidence that the rare earth ions form part of a complex defect which variously provides both the charge trapping and, during heating, the radiative decay. The peaks have the same activation energies but different pre-exponential factors. Modifications of the material by thermal treatments using furnace or laser pulse heating convert the state of dispersion of the rare earth ions between isolated, pair or defect clusters, which alter the dosimetry efficiency. In some cases the modified geometries are detectable via movement of the emission lines. For rapidly quenched materials, discontinuities in the thermoluminescence responses are suggested to be indicative of new microcrystalline phases. Slow cooling degrades the efficiency but also indicates the presence of further thermoluminescence glow peaks within the region of the main dosimetry signal. Pulsed laser heating with a UV laser altered the glow curve and resulted in strong signals. Mechanisms for this process are considered.

  7. Experimental evidence for the formation of divalent ytterbium in the photodarkening process of Yb-doped fiber lasers.

    PubMed

    Rydberg, S; Engholm, M

    2013-03-25

    In this work we present experimental evidence that the valence instability of the ytterbium ion play a key role for the observed photodarkening mechanism in Yb-doped fiber lasers. Luminescence and excitation spectroscopy performed on UV irradiated Yb/Al doped silica glass preforms and near-infrared diode pumped photodarkened fibers show a concentration increase of Yb(2+) ions. A concentration decrease in Yb(3+) could also be observed for the UV irradiated preform. The findings contribute to an increased understanding of the kinetic processes related to photodarkening in Yb-doped high power fiber lasers. PMID:23546049

  8. Traffic at the tmRNA Gene

    PubMed Central

    Williams, Kelly P.

    2003-01-01

    A partial screen for genetic elements integrated into completely sequenced bacterial genomes shows more significant bias in specificity for the tmRNA gene (ssrA) than for any type of tRNA gene. Horizontal gene transfer, a major avenue of bacterial evolution, was assessed by focusing on elements using this single attachment locus. Diverse elements use ssrA; among enterobacteria alone, at least four different integrase subfamilies have independently evolved specificity for ssrA, and almost every strain analyzed presents a unique set of integrated elements. Even elements using essentially the same integrase can be very diverse, as is a group with an ssrA-specific integrase of the P4 subfamily. This same integrase appears to promote damage routinely at attachment sites, which may be adaptive. Elements in arrays can recombine; one such event mediated by invertible DNA segments within neighboring elements likely explains the monophasic nature of Salmonella enterica serovar Typhi. One of a limited set of conserved sequences occurs at the attachment site of each enterobacterial element, apparently serving as a transcriptional terminator for ssrA. Elements were usually found integrated into tRNA-like sequence at the 3? end of ssrA, at subsites corresponding to those used in tRNA genes; an exception was found at the non-tRNA-like 3? end produced by ssrA gene permutation in cyanobacteria, suggesting that, during the evolution of new site specificity by integrases, tropism toward a conserved 3? end of an RNA gene may be as strong as toward a tRNA-like sequence. The proximity of ssrA and smpB, which act in concert, was also surveyed. PMID:12533482

  9. Comparative study on optical properties of Yb3+ doped LiNbO3: MgO and LiNbO3:ZnO laser crystals

    NASA Astrophysics Data System (ADS)

    Ning, Kaijie; Li, Baizhong; Zhang, Qingli; Hang, Yin; Shi, Zhenhua

    2015-08-01

    Yb3+ doped LiNbO3:MgO (Mg, Yb:LN) and Yb3+ doped LiNbO3:ZnO (Zn, Yb:LN) laser crystals were grown from congruent melt by Czochralski (Cz) method and polarized under electric field. The absorption and emission spectra, and decay curves were measured and analyzed. Zn, Yb:LN crystal shows relatively larger cross sections both for absorption and emission spectra. The comparative study indicates that Zn, Yb:LN crystal would be one better crystal on potential laser performance than Mg, Yb:LN crystal.

  10. Laser desorption/ionization mass spectrometry on nanostructured semiconductor substrates: DIOS(TM) and QuickMass(TM)

    NASA Astrophysics Data System (ADS)

    Law, K. P.

    2010-02-01

    In the era of systems biology, new analytical platforms are under demand. Desorption/ionization on silicon mass spectrometry (DIOS-MS) is a promising high throughput laser mass spectrometry approach that has attracted a lot of attention, and has been commercialized. Another substrate material manufactured by physical method has also been made commercially available under the trade name of QuickMass(TM). These two commercial substrates, DIOS(TM) and QuickMass(TM), were investigated independently from the manufacturers and were characterized by a number of advanced surface techniques. This work determined (1) the correlation between the substrate physicochemical properties and their LDI activity, (2) the feasibility of metabolic profiling from complex biological matrices and (3) the laser desorption/ionization mechanism. The DIOS(TM) substrate was characterized with a thick nano-sized porous layer, a high surface concentration of fluorocarbon and silicon oxides and super-hydrophobicity. In contrast, the QuickMass(TM) substrate consisted of a non-porous germanium thin-film. The relatively high ionization efficiency obtained from the DIOS(TM) substrate was contributed to the fluorosilane manufacturing processes and its porous morphology. Despite the QuickMass(TM) substrate being less effective, it was noted that the use of germanium affords a self-cleaning mechanism and suppresses background interference of mass spectra. The suitability of DIOS(TM) substrates for metabolic profiling of complex biological matrices was demonstrated. DIOS mass spectra of human blood plasma, human urine and animal liver tissue extracts were produced. Suitable extraction methods were found to be important, but relatively simplified approaches were sufficient. Further investigations of the DIOS desorption/ionization mechanism were carried out. The previously proposed sub-surface state reaction could be a molten-solid interfacial state reaction of the substrate and this had a significant effect toward the protonation reaction of amines.

  11. Czochralski growth of thulium gallium garnets: Tm 3(Tm xGa 2-x)Ga 3O 12

    NASA Astrophysics Data System (ADS)

    Baermann, A.; Guse, W.; Saalfeld, H.

    1982-05-01

    Large, optically-clear single crystals of Tm 3(Tm xGa 2-x)Ga 3O 12 ( x=0.09-0.15) have been grown using the Czochralski meth od for the first time. The growth direction was [001]. X-ray topography and optical methods were used to check the quality of the single crystals. Lattice constants in comparison to the melt stoichiometry are discussed, spectrographic and refractive data are presented.

  12. Ends of the line for tmRNA-SmpB

    PubMed Central

    Hudson, Corey M.; Lau, Britney Y.; Williams, Kelly P.

    2014-01-01

    Genes for the RNA tmRNA and protein SmpB, partners in the trans-translation process that rescues stalled ribosomes, have previously been found in all bacteria and some organelles. During a major update of The tmRNA Website (relocated to http://bioinformatics.sandia.gov/tmrna), including addition of an SmpB sequence database, we found some bacteria that lack functionally significant regions of SmpB. Three groups with reduced genomes have lost the central loop of SmpB, which is thought to improve alanylation and EF-Tu activation: Carsonella, Hodgkinia, and the hemoplasmas (hemotropic Mycoplasma). Carsonella has also lost the SmpB C-terminal tail, thought to stimulate the decoding center of the ribosome. We validate recent identification of tmRNA homologs in oomycete mitochondria by finding partner genes from oomycete nuclei that target SmpB to the mitochondrion. We have moreover identified through exhaustive search a small number of complete, but often highly derived, bacterial genomes that appear to lack a functional copy of either the tmRNA or SmpB gene (but not both). One Carsonella isolate exhibits complete degradation of the tmRNA gene sequence yet its smpB shows no evidence for relaxed selective constraint, relative to other genes in the genome. After loss of the SmpB central loop in the hemoplasmas, one subclade apparently lost tmRNA. Carsonella also exhibits gene overlap such that tmRNA maturation should produce a non-stop smpB mRNA. At least some of the tmRNA/SmpB-deficient strains appear to further lack the ArfA and ArfB backup systems for ribosome rescue. The most frequent neighbors of smpB are the tmRNA gene, a ratA/rnfH unit, and the gene for RNaseR, a known physical and functional partner of tmRNA-SmpB. PMID:25165464

  13. Deposition of luminescent NaCl:Tm2+ thin films with a Tm concentration gradient using RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    de Jong, M.; Kesteloo, W.; van der Kolk, E.

    2015-08-01

    Luminescent thin films were deposited using magnetron sputtering of a NaCl single crystal and Tm-metal. By using a combinatorial approach, a single film with a thickness ranging from 3.1 ?m to 6.9 ?m and a Tm to Na ratio varying from 0.05 to 0.26 was obtained. XRD shows the formation of the simple cubic NaCl structure and SEM images display a mix of 0.50-0.75 ?m and 2-3 ?m cubic and needle-like structures when the substrate is not rotating during deposition. NIR transmission spectra reveal narrow absorption lines at 1134 nm and 1218 nm caused by 4f-4f absorption of divalent and trivalent Tm, respectively. Photoluminescence excitation and UV-VIS transmission spectra show broad bands between 275 nm and 700 nm, caused by the Tm2+ 4f13 ? 4f125d1 transitions. Excitation into these bands results in 2F5/2 ? 2F7/2 line emission by Tm2+ at 1134 nm. The broad absorption range covering the entire UV and VIS part of the solar spectrum and the absence of self-absorption of the sharp emission line makes NaCl:Tm2+ a promising material for luminescent solar concentrators as thin films on glass provided light scattering can be minimised.

  14. 151Eu isomer shifts and charge transfer in Eu-base intermetallic compounds

    NASA Astrophysics Data System (ADS)

    de Vries, J. W. C.; Thiel, R. C.; Buschow, K. H. J.

    1983-07-01

    The 151Eu isomer shift found in various divalent Eu compounds have been analysed by means of the model proposed earlier for the 197Au isomer shift in Au-base materials by Miedema and Van der Woude. Relative changes of 5d and 6s electron occupation numbers due to alloying of divalent Eu with other elements were deduced from this analysis and compared with electronic properties reported for such compounds in the literature.

  15. Crystallization and photoluminescence properties of ?-RE2(WO4)3 (RE: Gd, Eu) in rare-earth tungsten borate glasses

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Honma, Tsuyoshi; Komatsu, Takayuki

    2013-03-01

    Glasses with the compositions of 22.5RE2O3-47.5WO3-30B2O3 (mol%) (RE: Gd, Eu) were prepared by a conventional melt quenching method, and ?-Gd2(WO4)3 and ?-Eu2(WO4)3 crystals were synthesized through their crystallization. The two types of WO4 tetrahedra present in ?-RE2(WO4)3 provide the Raman bands at 931-934 cm-1 for WIIO4 tetrahrdra with much distortions and at 946-950 cm-1 for WIO4 tetrahedra with a near regular symmetry. The crystallized samples containing ?-Eu2(WO4)3 exhibit strong red emissions under the excitation at 396 and 467 nm, although the base glass has no photoluminescence emission. ?-Gd2(WO4)3 and ?-Eu2(WO4)3 crystals were patterned on the glass surface by irradiations of a continuous wave Yb:YVO4 fiber laser (wavelength: 1080 nm).

  16. Antiferromagnetism in EuNiGe3

    SciTech Connect

    Goetsch, R. J.; Ananad, V. K.; Johnston, David C.

    2013-02-07

    The synthesis and crystallographic and physical properties of polycrystalline EuNiGe3 are reported. EuNiGe3 crystallizes in the noncentrosymmetric body-centered tetragonal BaNiSn3-type structure (space group I4mm), in agreement with previous reports, with the Eu atoms at the corners and body center of the unit cell. The physical property data consistently demonstrate that this is a metallic system in which Eu spins S = 7/2 order antiferromagnetically at a temperature TN = 13.6 K.Magnetic susceptibility ? data forT >TN indicate that the Eu atoms have spin 7/2 with g = 2, that the Ni atoms are nonmagnetic, and that the dominant interactions between the Eu spins are ferromagnetic. Thus we propose that EuNiGe3 has a collinear A-type antiferromagnetic structure, with the Eu ordered moments in the ab plane aligned ferromagnetically and with the moments in adjacent planes along the c axis aligned antiferromagnetically. A fit of ?(T #2; TN) by our molecular field theory is consistent with a collinear magnetic structure. Electrical resistivity ? data from TN to 350 K are fitted by the Bloch-Gruneisen model for electron-phonon scattering, yielding a Debye temperature of 265(2) K.Astrong decrease in ? occurs belowTN due to loss of spin-disorder scattering. Heat capacity data at 25 K #2; T #2; 300Kare fitted by the Debye model, yielding the same Debye temperature 268(2) K as found from ?(T ). The extracted magnetic heat capacity is consistent with S = 7/2 and shows that significant short-range dynamical spin correlations occur above TN. The magnetic entropy at TN = 13.6 K is 83% of the expected asymptotic high-T value, with the remainder recovered by 30 K.

  17. Microwave sintering of Yb:YAG transparent laser ceramics

    NASA Astrophysics Data System (ADS)

    Esposito, Laura; Piancastelli, Andreana; Bykov, Yury; Egorov, Sergei; Eremeev, Anatolii

    2013-02-01

    Reactive sintering of YAG based ceramics is generally performed under high vacuum in graphite-free furnaces in order to guarantee the elimination of pores and absence of any contamination. An alternative densification technique is the field assisted process such as spark plasma sintering and microwave sintering. Both of these methods are characterized by very fast heating rates, low sintering temperatures and short sintering times. The microwave sintering process is different from electric resistance heating since heat is generated in the bulk of the powder compact through electromagnetic radiation absorption and creates within its body uniform temperature distribution. Microwave sintering of laser ceramics is advantageously distinguished by the absence of any elements having high temperature such as electric heaters or dies which materials can contaminate the sintered parts. In addition, the inverse temperature distribution that exists within the body under volumetric microwave heating is favorable for elimination of porosity. Microwave sintering of Yb:YAG samples were tested and the obtained results are presented. The samples were sintered on a gyrotron-based system operating at a frequency of 24 GHz with microwave power up to 6 kW. Reactive sintering of YAG doped with 1.0, 5.0, and 9.8 at.% Yb2O3 was performed in different temperature-time regimes. The microstructure and the optical transmittance of the obtained samples were compared to those of samples obtained by conventional high vacuum sintering.

  18. p-wave optical Feshbach resonances in {sup 171}Yb

    SciTech Connect

    Goyal, Krittika; Deutsch, Ivan; Reichenbach, Iris

    2010-12-15

    We study the use of an optical Feshbach resonance to modify the p-wave interaction between ultracold polarized {sup 171}Yb spin-1/2 fermions. A laser exciting two colliding atoms to the {sup 1}S{sub 0}+{sup 3}P{sub 1} channel can be detuned near a purely-long-range excited molecular bound state. Such an exotic molecule has an inner turning point far from the chemical binding region, and thus, three-body recombination in the Feshbach resonance will be highly suppressed in contrast to that typically seen in a ground-state p-wave magnetic Feshbach resonance. We calculate the excited molecular bound-state spectrum using a multichannel integration of the Schroedinger equation, including an external perturbation by a magnetic field. From the multichannel wave functions, we calculate the Feshbach resonance properties, including the modification of the elastic p-wave scattering volume and inelastic spontaneous scattering rate. The use of magnetic fields and selection rules for polarized light yields a highly controllable system. We apply this control to propose a toy model for three-color superfluidity in an optical lattice for spin-polarized {sup 171}Yb, where the three colors correspond to the three spatial orbitals of the first excited p band. We calculate the conditions under which tunneling and on-site interactions are comparable, at which point quantum critical behavior is possible.

  19. An Yb optical lattice clock: Current status at KRISS

    NASA Astrophysics Data System (ADS)

    Yu, Dai-Hyuk; Park, Chang Yong; Lee, Won-Kyu; Lee, Sangkyung; Park, Sang Eon; Mun, Jongchul; Lee, Sang-Bum; Kwon, Taeg Yong

    2013-08-01

    The current status of an Yb optical lattice clock at the Korea Research Institute of Standards and Science (KRISS) is reported. The systematic uncertainty of the Yb clock in the first accuracy evaluation was 1.5 10-14 [Park et al., Metrologia 50, 119 (2013)]. The uncertainty was dominated by the large uncertainties in the lattice ac Stark shift and the collisional shift, which were mainly limited by the large linewidth and jitter of the clock laser. Recently, a highly stable clock laser at 578 nm was developed with a short-term linewidth of 3.5 Hz and a frequency jitter of about 25 Hz at 1 s and 10 s measurement times, respectively. The long-term frequency drift showed only a linear dependence on time, confirming that the temperature of the super-cavity was maintained a zero coefficient of thermal expansion. The frequency of the lattice laser at 759 nm was phase locked to the optical frequency comb and could be stabilized at the "absolute" frequency of the "magic wavelength", to within a 1-MHz uncertainty. This improvement greatly reduced the fractional uncertainty due to the lattice ac Stark shift down to 2 10-16. The systematic uncertainty of the clock is currently 5.3 10-15 and is dominated by the collisional frequency shift.

  20. Optical Lattice Induced Light Shifts in an Yb Atomic Clock

    SciTech Connect

    Barber, Z. W.; Stalnaker, J. E.; Lemke, N. D.; Poli, N.; Oates, C. W.; Fortier, T. M.; Diddams, S. A.; Hollberg, L.; Hoyt, C. W.; Taichenachev, A. V.; Yudin, V. I.

    2008-03-14

    We present an experimental study of the lattice-induced light shifts on the {sup 1}S{sub 0}{yields}{sup 3}P{sub 0} optical clock transition ({nu}{sub clock}{approx_equal}518 THz) in neutral ytterbium. The 'magic' frequency {nu}{sub magic} for the {sup 174}Yb isotope was determined to be 394 799 475(35) MHz, which leads to a first order light shift uncertainty of 0.38 Hz. We also investigated the hyperpolarizability shifts due to the nearby 6s6p{sup 3}P{sub 0}{yields}6s8p{sup 3}P{sub 0}, 6s8p{sup 3}P{sub 2}, and 6s5f{sup 3}F{sub 2} two-photon resonances at 759.708, 754.23, and 764.95 nm, respectively. By measuring the corresponding clock transition shifts near these two-photon resonances, the hyperpolarizability shift was estimated to be 170(33) mHz for a linear polarized, 50 {mu}K deep, lattice at the magic wavelength. These results indicate that the differential polarizability and hyperpolarizability frequency shift uncertainties in a Yb lattice clock could be held to well below 10{sup -17}.

  1. Formation of LiYb Molecules by Photoassocation

    NASA Astrophysics Data System (ADS)

    Roy, Richard; Shrestha, Rajendra; Green, Alaina; Gupta, Subhadeep

    2015-05-01

    Combining ultracold alkali and alkaline-earth (or earth-like) gases to form ground state doublet sigma molecules offers a paramagnetic degree of freedom, which is attractive for quantum information and simulation applications and studies of controlled chemical reactions. However, the spinless ground electronic state of alkaline-earth atoms renders magnetoassociation techniques infeasible. Instead, coherent Raman techniques may be used to couple free atoms in an ultracold mixture to rovibrational states in the ground electronic manifold. To this end, we perform photoassociation (PA) spectroscopy of 6Li and multiple Yb isotopes in a dual-species MOT on the Li D line (671 nm) and resolve multiple features in the exited electronic YbLi* potentials. We plan to utilize these excited molecular states to perform 2-photon PA spectroscopy of the ground doublet sigma potential. Subsequently, the states with the most favorable Franck-Condon overlap will be targeted for coherent production of ground state molecules in a 3 dimensional optical lattice. We gratefully acknowledge funding from the NSF, AFOSR, and ARO-MURI.

  2. Valence band structure of the icosahedral Ag-In-Yb quasicrystal

    SciTech Connect

    Sharma, H. R.; Simutis, G.; Dhanak, V. R.; Nugent, P. J.; McGrath, R.; Cui, C.; Shimoda, M.; Tsai, A. P.; Ishii, Y.

    2010-03-01

    The valence band structure of the icosahedral (i) Ag-In-Yb quasicrystal, which is isostructural to the binary i-Cd-Yb system, is investigated by ultraviolet photoemission spectroscopy (UPS). Experimental results are compared with electronic-structure calculations of a cubic approximant of the same phase. UPS spectra from the fivefold, threefold, and twofold i-Ag-In-Yb surfaces reveal that the valence band near to the Fermi level is dominated by Yb 4f-derived states, in agreement with calculations. The spectra also exhibit peaks which are surface core level shifted, caused by changes in the electronic structure in surface layers. Calculations yield a pseudogap in the density of states due to a hybridization of the Yb 5d band with the Ag 5p and In 5p bands. Both experimental and calculated band features are very similar to those of Cd-Yb. The modification of the band structure after surface treatment by sputtering and by oxidation is also studied. Additionally, the work function of i-Ag-In-Yb measured from the width of UPS spectrum is found to be almost unaffected by surface orientation, but increases after sputtering or oxidation.

  3. Thermal conductivity of Y 6WO 12 and Yb 6WO 12 ceramics

    NASA Astrophysics Data System (ADS)

    Zheng, Ying; Kurosaki, Ken; Tokushima, Kazuyuki; Ohishi, Yuji; Muta, Hiroaki; Yamanaka, Shinsuke

    2011-12-01

    Y 6AnO 12 and Yb 6AnO 12 ( An: actinide elements) are potential ceramic waste forms in which various actinide elements could be immobilized stably for a prolonged period. The thermal conductivity of Y 6WO 12 and Yb 6WO 12 has been studied because Y 6WO 12 and Yb 6WO 12 have the same crystal structure as Y 6AnO 12 and Yb 6AnO 12. The high-density pellets of Y 6WO 12 and Yb 6WO 12 were prepared by spark plasma sintering (SPS), and the thermal conductivity ( ?) was examined. The ? value of Y 6WO 12 (around 6.05 W m -1 K -1 at 300 K) was higher than that of Yb 6WO 12 (around 4.59 W m -1 K -1 at 300 K). The magnitude relation of ? between Y 6WO 12 and Yb 6WO 12 was discussed based on the general lattice thermal conductivity theory.

  4. Insights into the energy transfer mechanism in Ce3+-Yb3+ codoped YAG phosphors

    NASA Astrophysics Data System (ADS)

    Yu, D. C.; Rabouw, F. T.; Boon, W. Q.; Kieboom, T.; Ye, S.; Zhang, Q. Y.; Meijerink, A.

    2014-10-01

    Two distinct energy transfer (ET) mechanisms have been proposed for the conversion of blue to near-infrared (NIR) photons in YAG:Ce3+,Yb3+. The first mechanism involves downconversion by cooperative energy transfer, which would yield two NIR photons for each blue photon excitation. The second mechanism of single-step energy transfer yields only a single NIR photon for each blue photon excitation and has been argued to proceed via a Ce4+-Yb2+ charge transfer state (CTS). If the first mechanism were operative in YAG:Ce3+,Yb3+, this material would have the potential to greatly increase the response of crystalline Si solar cells to the blue/UV part of the solar spectrum. In this work, however, we demonstrate that blue-to-NIR conversion in YAG:Ce3+,Yb3+ goes via the single-step mechanism of ET via a Ce4+-Yb2+ CTS. The photoluminescence decay dynamics of the Ce3+ excited state are inconsistent with Monte Carlo simulations of the cooperative (one-to-two photon) energy transfer, while they are well reproduced by simulations of single-step (one-to-one photon) energy transfer via a charge transfer state. Based on temperature dependent measurements of energy transfer and luminescence quenching we construct a configuration coordinate model for the Ce3+-to-Yb3+ energy transfer, which includes the Ce4+-Yb2+ charge transfer state.

  5. Thermodynamic and transport properties of single crystalline RCo2Ge2 (R=Y, LaNd, SmTm)

    SciTech Connect

    Kong, Tai; Cunningham, Charles E.; Taufour, Valentin; Budko, Sergey L.; Buffon, Malinda L.C.; Lin, Xiao; Emmons, Heather; Canfield, Paul C.

    2014-05-01

    Single crystals of RCo2Ge2 (R=Y, LaNd, SmTm) were grown using a self-flux method and were characterized by room-temperature powder X-ray diffraction; anisotropic, temperature and field dependent magnetization; temperature and field dependent, in-plane resistivity; and specific heat measurements. In this series, the majority of the moment-bearing members order antiferromagnetically; YCo2Ge2 and LaCo2Ge2 are non-moment-bearing. Ce is trivalent in CeCo2Ge2 at high temperatures, and exhibits an enhanced electronic specific heat coefficient due to the Kondo effect at low temperatures. In addition, CeCo2Ge2 shows two low-temperature anomalies in temperature-dependent magnetization and specific heat measurements. Three members (R=TbHo) have multiple phase transitions above 1.8 K. Eu appears to be divalent with total angular momentum L =0. Both EuCo2Ge2 and GdCo2Ge2 manifest essentially isotropic paramagnetic properties consistent with J =S =7/2. Clear magnetic anisotropy for rare-earth members with finite L was observed, with ErCo2Ge2 and TmCo2Ge2 manifesting planar anisotropy and the rest members manifesting axial anisotropy. The experimentally estimated crystal electric field (CEF) parameters B 20 were calculated from the anisotropic paramagnetic ? ab and ? c values and follow a trend that agrees well with theoretical predictions. The ordering temperatures, TNTN, as well as the polycrystalline averaged paramagnetic CurieWeiss temperature, ?avg, for the heavy rare-earth members deviate from the de Gennes scaling, as the magnitude of both is the highest for Tb, which is sometimes seen for extremely axial systems. Except for SmCo2Ge2, metamagnetic transitions were observed at 1.8 K for all members that ordered antiferromagnetically.

  6. Formation, optical properties, and electronic structure of thin Yb silicide films on Si(111)

    NASA Astrophysics Data System (ADS)

    Galkin, N. G.; Maslov, A. M.; Polyarnyi, V. O.

    2005-06-01

    Continuous very thin (2.5-3.0 nm) and thin (16-18 nm) ytterbium suicide films with some pinhole density (3107- 1108 cm-2) have been formed on Si(111) by solid phase epitaxy (SPE) and reactive deposition epitaxy (RDE) growth methods on templates. The stoichiometric ytterbium suicide (YbSi2) formation has shown in SPE grown films by AES and EELS data. Very thin Yb suicide films grown by RDE method had the silicon enrichment in YbSi2 suicide composition. The analysis of LEED data and AFM imaging has shown that ytterbium suicide films had non-oriented blocks with the polycrystalline structure. The analysis of scanning region length dependencies of the root mean square roughness deviation (?R(L)) for grown suicide films has shown that the formation of ytterbium suicide in SPE and RDE growth methods is determined by the surface diffusion of Yb atoms during the three-dimensional growth process. Optical functions (n, k, ?, ?1, ?2, Im ?1-1, neff, ?eff) of ytterbium silicide films grown on Si(1 1 1) have been calculated from transmittance and reflectance spectra in the energy range of 0.1-6.2 eV. Two nearly discrete absorption bands have been observed in the electronic structure of Yb silicide films with different composition, which connected with interband transitions on divalent and trivalent Yb states. It was established that the reflection coefficient minimum in R-spectra at energies higher 4.2 eV corresponds to the state density minimum in Yb suicide between divalent and trivalent Yb states. It was shown from optical data that Yb silicide films have the semi-metallic properties with low state densities at energies less 0.4 eV and high state densities at 0.5-2.5 eV.

  7. Phase stability regions in the Na 2CO 3-YbF 3-H 2O system at 190 C. Crystal structures of two new fluoride carbonates, Na 2Yb(CO 3) 2F and Na 3Yb(CO 3) 2F 2

    NASA Astrophysics Data System (ADS)

    Ben Ali, Amor; Maisonneuve, Vincent; Leblanc, Marc

    2002-11-01

    Phase stability regions in the Na 2CO 3-YbF 3-H 2O system at T=190 C, P=1110 5 Pa, t=1 h, microwave heating, and the crystal structures of two new carbonate fluorides Na 2Yb(CO 3) 2F and Na 3Yb(CO 3) 2F 2 are presented. Five phases, obtained for [YbF 3]?0.75 M and [Na]/[Yb]<30, are characterized by powder or single crystal X-ray diffraction, thermogravimetric or chemical analyses: NaYb(CO 3)F 2, Na 2Yb(CO 3) 2F, Na 3Yb(CO 3) 2F 2, Na 5Yb(CO 3) 42H 2O, and Yb(CO 3)(OH,F) xH 2O. NaYb(CO 3)F 2 ( a=6.897(7) , b=9.118(9) , c=6.219(6) ) and Na 5Yb(CO 3) 42H 2O are isostructural with NaY(CO 3)F 2 (horvathite) and Na 5Sc(CO 3) 42H 2O, respectively; the other phases were still unknown. Na 2Yb(CO 3) 2F is monoclinic, C2/ c, with a=17.440(6) , b=6.100(2) , c=11.237(1) , ?=95.64(3); V=1189.7(4) 3; Z=8 (1729 unique reflections, R=0.034, Rw=0.087). Na 2Yb(CO 3) 2F is described from infinite [001] chains [YbO 5F] ? built up from [YbO 6F] 2 dimers. Na 3Yb(CO 3) 2F 2 is noncentrosymmetric, Cc, with a=7.127(2) , b=29.916(9) , c=6.928(4) , ?=112.56(3); V=1359(4) 3; Z=8 (1838 unique reflections, R=0.074, Rw=0.235). The structure is built up from [NaYb(CO 3) 2F 2] ? layers; Yb 3+ and Na + cations are alternatively ordered and disordered in successive (010) layers which are separated by other Na + cations.

  8. Continuous wave Yb:YCOB cyan lasers with KTP as the sum-frequency converter

    NASA Astrophysics Data System (ADS)

    Lan, Ruijun; Cheng, Hao; Yang, Guang

    2015-12-01

    All-solid-state cyan laser at 500 nm range are reported based on a Yb:YCa4O(BO3)3 (Yb:YCOB) crystal and a type-II phase matched KTiOPO4 (KTP) crystal. The 503 nm cyan laser is obtained by the sum-frequency mixing (SFM) of 974 nm pump wave and 1042 nm fundamental wave. To the best of our knowledge, this is the first cyan laser demonstrated with Yb-doped YCOB crystal. A dual-wavelength laser at 505 and 525 nm is also obtained, which origins from the simultaneous SFM and self-frequency doubling.

  9. Ultralow-threshold Yb(3+):SiO(2) glass laser fabricated by the solgel process.

    PubMed

    Ostby, Eric P; Yang, Lan; Vahala, Kerry J

    2007-09-15

    A Yb-doped silica microcavity laser on a silicon chip is fabricated from a solgel thin film. The high-Q micro-toroid cavity, which has a finesse of 10,000, is evanescently coupled to an optical fiber taper. We report a threshold of 1.8 microW absorbed power that is, to the best of our knowledge, the lowest published threshold to date for any Yb-doped laser. The effect of Yb(3+) concentration on laser threshold is experimentally quantified. PMID:17873923

  10. Cold beam of isotopically pure Yb atoms by deflection using 1D-optical molasses

    NASA Astrophysics Data System (ADS)

    Rathod, K. D.; Singh, P. K.; Natarajan, Vasant

    2014-09-01

    We demonstrate generation of an isotopically pure beam of laser-cooled Yb atoms by deflection using 1D-optical molasses. Atoms in a collimated thermal beam are first slowed using a Zeeman Slower. They are then subjected to a pair of molasses beams inclined at $45^\\circ$ with respect to the slowed atomic beam. The slowed atoms are deflected and probed at a distance of 160 mm. We demonstrate selective deflection of the bosonic isotope $^{174}$Yb, and the fermionic isotope $^{171}$Yb. Using a transient measurement after the molasses beams are turned on, we find a longitudinal temperature of 41 mK.

  11. Yb:FAP and related materials, laser gain medium comprising same, and laser systems using same

    SciTech Connect

    Krupke, W.F.; Payne, S.A.; Chase, L.L.; Smith, L.K.

    1991-12-31

    An ytterbium doped laser material remarkably superior to all others, including Yb:YAG, comprises ytterbium doped apatite (Yb:Ca{sub 5}(PO{sub 4}){sub 3}F) or Yb:FAP, or ytterbium doped crystals structurally related to FAP. The new laser material is used in laser systems pumped by diode pump sources having an output near 0.905 microns or 0.98 microns, such as InGaAs and AlInGaAs, or other narrowband pump sources near 0.905 microns or 0.98 microns. The laser systems are operated in either the conventional or ground state depletion mode.

  12. Phonons in YB6 and LaB6: Effects of temperature and pressure

    NASA Astrophysics Data System (ADS)

    Ponosov, Yu. S.; Shitsevalova, N. Yu.

    2015-09-01

    Raman scattering by phonons in YB6 and LaB6 has been studied in wide temperature (8-800 K) and pressure (up to 10 GPa) ranges. Acoustic phonons in both hexaborides exhibit anomalous softening with a decrease in the temperature. The positive isothermal Grneisen coefficient of these modes in YB6 appears to be an order of magnitude lower than the absolute value of the negative isobaric coefficient, which indicates the dominating role of temperature effects. The temperature shifts of the vibration frequencies of the B sublattice in YB6 caused by phonon interactions have the opposite sign and exceed the respective shifts in LaB6.

  13. Yb:FAP and related materials, laser gain medium comprising same, and laser systems using same

    DOEpatents

    Krupke, William F. (Pleasanton, CA); Payne, Stephen A. (Castro Valley, CA); Chase, Lloyd L. (Livermore, CA); Smith, Larry K. (Salida, CA)

    1994-01-01

    An ytterbium doped laser material remarkably superior to all others, including Yb:YAG, comprises Ytterbium doped apatite (Yb:Ca.sub.5 (PO.sub.4).sub.3 F) or Yb:FAP, or ytterbium doped crystals that are structurally related to FAP. The new laser material is used in laser systems pumped by diode pump sources having an output near 0.905 microns or 0.98 microns, such as InGaAs and AlInGaAs, or other narrowband pump sources near 0.905 microns or 0.98 microns. The laser systems are operated in either the conventional or ground state depletion mode.

  14. Mode-locked operation of a diode-pumped femtosecond Yb:SrF2 laser.

    PubMed

    Druon, F; Papadopoulos, D N; Boudeile, J; Hanna, M; Georges, P; Benayad, A; Camy, P; Doualan, J L; Ménard, V; Moncorgé, R

    2009-08-01

    Femtosecond mode-locked operation is demonstrated for the first time, to our knowledge, with a Yb:SrF(2) crystal. The shortest pulse duration is 143 fs for an average power of 450 mW. The highest average power is 620 mW for a pulse duration of 173 fs. Since Yb:SrF(2) corresponds to the longest-lifetime Yb-doped crystal with which the mode-locking operation has been achieved, a detailed analysis is carried out to characterize the quality of the solitonlike regime. PMID:19649095

  15. Infrared spectroscopic and density functional theoretical study of tris(cyclopentadienyl)ytterbium (YbCp3) and acetone adduct molecules of YbCp3 in low-temperature matrices

    NASA Astrophysics Data System (ADS)

    Miyazaki, Jun; Sudo, Nao; Yamada, Yasuhiro

    2015-08-01

    Tris(cyclopentadienyl)ytterbium (YbCp3) was isolated in solid argon matrices, and the monomeric structure of YbCp3 was studied by means of infrared spectroscopy and density functional theory calculations. Compared with our previous study on the structure of tris(cyclopentadienyl)scandium (ScCp3) isolated in solid argon matrices, it was apparent that the monomeric structure of YbCp3 has three ?5-Cp bonds to the Yb atom, Yb(?5-Cp)3, analogous to the structure of matrix-isolated ScCp3. In addition, the stable dimer structures of YbCp3 were also predicted using density functional theory calculations. Furthermore, we produced the acetone adduct molecules of YbCp3 for the first time by co-condensing YbCp3 and an acetone/argon mixture gas on a cold substrate at 20 K. Molecules with Ybsbnd O bonding between YbCp3 and acetone were detected in low-temperature acetone/argon matrices. By using natural bond orbital (NBO) and curve fitting analysis, the structures of the acetone adduct molecules of YbCp3 were deduced.

  16. Electronic structure of YbGa1.15Si0:85 and YbGaxGe2-x probed by resonant x-ray emission and photoelectron spectroscopies

    SciTech Connect

    Yamaoka, Hitoshi; Jarrige, Ignace; Tsujii, Naohito; Imai, Motoharu; Lin, Jung-Fu; Matsunami, Masaharu; Eguchi, Ritsuko; Arita, Masashi; Shimada, Kenya; Namatame, Hirofumi; Taniguchi, Masaki; Taguchi, Munetaka; Senba, Yasunori; Ohashi, Haruhiko; Hiraoka, Nozomu; Ishii, Hirofumi; Tsuei, Ku-Ding

    2011-03-31

    We performed an x-ray spectroscopic study combining resonant x-ray emission spectroscopy (RXES) and photoelectron spectroscopy on the superconducting ternary silicide YbGa 1.15 Si 0.85 and nonsuperconducting ternary germanide YbGax Ge2-x (x = 1.0 and 1.1). The Yb valence for all three compounds is found to be about 2.3. In YbGa1.15 Si0.85 no temperature dependence of the Yb valence is observed in the RXES spectra in the temperature range of 7–300 K, while the valence shows a drastic increase under pressure from the Yb2+ state partially including itinerant electrons to the localized Yb3+ state. Differences are observed in the valence-band spectra of the photoelectron spectroscopy between YbGa1.15 Si0.85 and YbGax Ge2-x , which may be attributed to the difference of crystal structure. We conclude that both the crystal structure of the planar GaSi layer in YbGa1.15 Si0.85 and the resultant electronic structure may have a crucial role in the occurrence of superconductivity.

  17. High-spin structure, K isomers, and state mixing in the neutron-rich isotopes 173Tm and 175Tm

    NASA Astrophysics Data System (ADS)

    Hughes, R. O.; Lane, G. J.; Dracoulis, G. D.; Byrne, A. P.; Nieminen, P. H.; Watanabe, H.; Carpenter, M. P.; Chowdhury, P.; Janssens, R. V. F.; Kondev, F. G.; Lauritsen, T.; Seweryniak, D.; Zhu, S.

    2012-11-01

    High-spin states in the odd-proton thulium isotopes 173Tm and 175Tm have been studied using deep-inelastic reactions and ?-ray spectroscopy. In 173Tm, the low-lying structure has been confirmed and numerous new states have been identified, including a three-quasiparticle K?= 19/2- isomer with a lifetime of ?=360(100) ns at 1906 keV and a five-quasiparticle K?=35/2- isomer with a lifetime of ?= 175(40) ns at 4048 keV. The K?=35/2- state is interpreted as a t-band configuration that shows anomalously fast decays. In 175Tm, the low-lying structure has been reevaluated, a candidate state for the 9/2-[514] orbital has been identified at 1175 keV, and the 7/2-[523] bandhead has been measured to have a lifetime of ?= 460(50) ns. Newly identified high-K structures in 175Tm include a K?=15/2- isomer with a lifetime of ?= 64(3) ns at 947 keV and a K?= 23/2+ isomer with a lifetime of ?= 30(20) ?s at 1518 keV. The K?=15/2- isomer shows relatively enhanced decays to the 7/2-[523] band that can be explained by chance mixing with the 15/2- member of the 7/2- band. Multiquasiparticle calculations have been performed for 173Tm and 175Tm, the results of which compare well with the experimentally observed high-spin states.

  18. Spectroscopic properties of Ho3+, Tm3+, and Ho3+/Tm3+ doped tellurite glasses for fiber laser applications

    NASA Astrophysics Data System (ADS)

    Seshadri, M.; Ferencz Junior, J. A. P.; Ratnakaram, Y. C.; Barbosa, L. C.

    2014-03-01

    Several papers were reported on spectroscopic properties of rare earth doped different host glasses. A complete knowledge of fluorescence properties of rare earth ions in laser materials is necessary to achieve efficient, compact and cheap sources of laser radiation for NIR and mid-IR region. Tellurite glasses are potentially useful for generation of NIR and mid-IR laser radiation due to its special features such as lowest phonon energy (750 cm-1) among oxide glasses, reasonably wide transmission region (0.35 - 5?m), good glass stability, good rare earth ion solubility, high linear and non-linear refractive index. In the present work, authors prepared Ho3+ and Tm3+ singly doped and Ho3+/Tm3+ co-doped tellurite glasses using conventional melt-quenching method. Spectroscopic measurements and analysis of energy transfer process in Ho3+, Tm3+ and Ho3+ /Tm3+ co-doped glasses pumped with 785nm and 451 nm excitation wavelengths have been performed. There are some spectroscopic properties which are important in understanding and modeling of rare earth doped laser materials. Using Judd-Ofelt theory, radiative transition rates (Arad), radiative lifetimes (?R) and branching ratios (?) were estimated for certain excited states of Ho3+ and Tm3+ doped tellurite glasses. The emission cross-sections and gain coefficients have been determined from the absorption spectra of Ho3+ and Tm3+ ions in tellurite glasses. The energy transfer process such as ion cross-relaxation, Tm3+-Ho3+ energy transfer and energy transfer upconversion were studied and identified to specific candidate for laser operation.

  19. Performance of Landsat TM in ship detection in turbid waters

    NASA Astrophysics Data System (ADS)

    Wu, Guofeng; de Leeuw, Jan; Skidmore, Andrew K.; Liu, Yaolin; Prins, Herbert H. T.

    2009-02-01

    The visible and near infrared bands of Landsat have limitations for detecting ships in turbid water. The potential of TM middle infrared bands for ship detection has so far not been investigated. This study analyzed the performance of the six Landsat TM visible and infrared bands for detecting dredging ships in the turbid waters of the Poyang Lake, China. A colour composite of principal components analysis (PCA) components 3, 2 and 1 of a TM image was used to randomly select 81 dredging ships. The reflectance contrast between ships and adjacent water was calculated for each ship. A z-score and related p-value were used to assess the ship detection performance of the six Landsat TM bands. The reflectance contrast was related to water turbidity to analyze how water turbidity affected the capability of ship identification. The results revealed that the TM middle infrared bands 5 and 7 better discriminated vessels from surrounding waters than the visible and near infrared bands 1-4. A significant relation between reflectance contrast and water turbidity in bands 1-4 could explain the limitations of bands 1-4; while water turbidity has no a significant relation to the reflectance contrast of bands 5 and 7. This explains why bands 5 and 7 detect ships better than bands 1-4.

  20. Pred?TM: A Novel ?-Transmembrane Region Prediction Algorithm

    PubMed Central

    Roy Choudhury, Amrita; Novi?, Marjana

    2015-01-01

    Predicting the transmembrane regions is an important aspect of understanding the structures and architecture of different ?-barrel membrane proteins. Despite significant efforts, currently available ?-transmembrane region predictors are still limited in terms of prediction accuracy, especially in precision. Here, we describe Pred?TM, a transmembrane region prediction algorithm for ?-barrel proteins. Using amino acid pair frequency information in known ?-transmembrane protein sequences, we have trained a support vector machine classifier to predict ?-transmembrane segments. Position-specific amino acid preference data is incorporated in the final prediction. The predictor does not incorporate evolutionary profile information explicitly, but is based on sequence patterns generated implicitly by encoding the protein segments using amino acid adjacency matrix. With a benchmark set of 35 ?-transmembrane proteins, Pred?TM shows a sensitivity and precision of 83.71% and 72.98%, respectively. The segment overlap score is 82.19%. In comparison with other state-of-art methods, Pred?TM provides a higher precision and segment overlap without compromising with sensitivity. Further, we applied Pred?TM to analyze the ?-barrel membrane proteins without defined transmembrane regions and the uncharacterized protein sequences in eight bacterial genomes and predict possible ?-transmembrane proteins. Pred?TM can be freely accessed on the web at http://transpred.ki.si/. PMID:26694538