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  • 1.
    Khachatourian, Malek Adrine
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Iran University of Science and Technology, Iran.
    Golestani-Fard, F.
    Sarpoolaky, H.
    Vogt, Carmen
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vasileva, Elena
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Mensi, Mounir
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Microwave synthesis of Y2O3:Eu3+ nanophosphors: A study on the influence of dopant concentration and calcination temperature on structural and photoluminescence properties2016In: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 169, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Red fluorescent emitting monodispersed spherical Y<inf>2</inf>O<inf>3</inf> nanophosphors with different Eu3+ doping concentrations (0-13 mol%) are synthesized by a novel microwave assisted urea precipitation, which is recognized as a green, fast and reproducible synthesis method. The effect of Eu3+ doping and calcination temperature on the structural characteristics and luminescence properties of particles is investigated in detail. The as prepared powders have (Y,Eu)(OH)(CO<inf>3</inf>) structure which converts to Y<inf>2</inf>O<inf>3</inf>:Eu3+ from 500 °C and become crystalline at higher temperatures. The crystallite size of nanophosphors increased from 15 nm to 25 nm as the calcination temperature increased from 700 °C to 1050 °C. The efficient incorporation of Eu3+ ions in cubic Y<inf>2</inf>O<inf>3</inf> host matrix is confirmed by the calculated X-ray Powder diffraction (XRPD) structural parameters. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs show that the as obtained and calcined particles are spherical, monodispersed and non-agglomerated. The overall size of particles increases from 61±8 nm to 86±9 nm by increasing Eu3+ concentration from 0 mol% to 13 mol%. High resolution TEM revealed polycrystalline nature of calcined particles. The particles exhibit a strong red emission under ultraviolet (UV) excitation. The photoluminescence (PL) intensity of the peaks increases proportionally with Eu3+ concentration and the calcination temperature with no luminescence quenching phenomenon observed even for Y<inf>2</inf>O<inf>3</inf>:13%Eu3+. The fluorescent emission properties combined with the monodispersity and narrow size distribution characteristics make the Y<inf>2</inf>O<inf>3</inf>:Eu3+ heavy metal free nanophosphors applicable in fluorescence cell imaging and as fluorescence biolabels.

  • 2.
    Lindgren, Mikael
    et al.
    Department of Physics, Norwegian University of Science and Technology.
    Minaev, Boris
    Department of Physics, Norwegian University of Science and Technology.
    Glimsdal, Eirik
    Department of Physics, Norwegian University of Science and Technology.
    Vestberg, Robert
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Westlund, Robert
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Electronic states and phosphorescence of dendron functionalized platinum(II) acetylides2007In: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 124, no 2, p. 302-310Article in journal (Refereed)
    Abstract [en]

    The photophysical properties of bis((4-(phenylethynyl)phenyl)ethynyl)bis(tributylphosphine) platinum(II) with 2,2-bis(methylo])propionic acid (bis-MPA) dendritic substituents were studied. The fluorescence emission decay upon excitation in the UV (typically 350-380 nm) was rapid, in the order of I ns or shorter. In oxygen-saturated tetrahydrofuran solvent, the phosphorescence decay time was in the order of 200 ns. Bright phosphorescence at 530 nm was found for dendrimers under certain conditions. The associated phosphorescence decay time considerably increased to above 100-200 mu s at higher concentrations (30-100 mu M), and in oxygen-evacuated samples. Thus, it was clarified that the strongest triplet quenching was caused by oxygen dissolved in the sample, since it was possible to reversibly go between the bright and quenched phosphorescent state by freeze-thaw pumping cycles. The bright phosphorescence formed spontaneously for the cases with the larger dendritic substituents is implying a chromophore protecting effect. From time-dependent density functional calculations, the electronic structure of a few low-lying singlet and triplet states are discussed. A new mechanism for efficient triplet state formation and phosphorescence of Pt-ethynyls is proposed. Here, a fast relaxation via internal conversion takes the excited population of the dominant pi -> pi*, excitation into a lower singlet state of ligand-to-metal charge transfer character of pi sigma* type. This allows an efficient inter system crossing to the triplet state manifold.

  • 3.
    Linnros, Jan
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Gregorkiewicz, Tom
    Elliman, Rob
    Kimerling, Lionel
    Silicon-based photonics2006In: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 121, no 2, p. V-VArticle in journal (Other academic)
  • 4. Maeztu, Raquel
    et al.
    Gonzalez-Gaitano, Gustavo
    Tardajos, Gloria
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Chemiluminescence of phthalhydrazide derivatives in organized media: Interactions with surfactants and cyclodextrins2011In: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 131, no 4, p. 662-668Article in journal (Refereed)
    Abstract [en]

    The chemiluminescent oxidation of some phthalhydrazide derivatives, luminol (LUM), isoluminol (ISOL), N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and N-(6-aminohexyl)-N-ethylisoluminol (AHEI), has been carried out in micellar media and in the presence of natural cyclodextrins (CDs), using Co(II) as catalyst and H2O2 as oxidant. The cationic cetyltrimethylammonium bromide (CAB) and, in a lesser extent, the anionic sodium dodecyl sulfate (SDS) produce quenching in the chemiluminescence (CL) of all the luminophores at concentrations above the cmc, whereas slight enhancements are attained with the nonionic pentaethylene glycol monododecyl ether (C12E5). On the contrary, the incorporation of the CDs to the reaction produces a remarkable intensification of the CL. Binding of the luminophores to the macrocycles and the micelles has been studied by Pulsed-Gradient-Spin-Echo-NMR (PGSE-NMR) and fluorescence anisotropy. The cationic CTAB decreases the emission mainly due to charge compensation as a result of the association of the luminophores and the luminescent intermediates to the micelles. The presence of the alkyl substituents of ABEI and AHEI provides an additional hydrophobic contribution to the binding process. SDS quenches this reaction as the micelles retain Co(II) on their anionic layer. The protection and stabilization of these luminophores or their luminescent intermediates provided by the cavities of the CDs make this family of cyclic oligosaccharides much more suitable agents than the surfactants for enhancing the CL in aqueous media for this specific reaction.

  • 5. Pitois, C.
    et al.
    Hult, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lindgren, M.
    Lanthanide-cored fluorinated dendrimer complexes: synthesis and luminescence characterization2005In: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 111, no 4, p. 265-283Article in journal (Refereed)
    Abstract [en]

    Eu3+-. Tb3+- and Er3+-cored dendrimer complexes were prepared by self-assembly of three fluorinated dendrons, each with a carboxylate anion focal point, around the lanthanide ion. Energy transfer from the peripheral fluorinated phenyl moieties of the dendrons to the lanthanide cation was evidenced spectroscopically for Eu3+- and Tb3+-cored dendrimer complexes in solution. The excitation of perfluorinated aromatic groups was found to decay with ca. 0.7 ns and a longer decay time 10-13 ns was related to the coordination at the Ln(3+) focal point. Luminescence from the lanthanide core decays with lifetime in the range 1-1.5ms over a wide concentration range (mu M-mM), similar to the luminescence decay time of the corresponding acetate ion complexes in D2O. The main quenching mechanism of the lanthanide emission appears to be due to vibrations among surrounding C-H bonds of the intermediate shell of the flexible dendrimer scaffold. Antenna effect and energy harvesting from the surface of the dendrimer and transfer to the core was the main mechanism for luminescecnce in the dendrimer complexes with lanthanide cations.

  • 6.
    Sychugov, Ilya
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Lu, J.
    Elfström, Niklas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Structural imaging of a Si quantum dot: Towards combined PL and TEM characterization2006In: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 121, no 2, p. 353-Article in journal (Refereed)
    Abstract [en]

    Individual silicon quantum dots were fabricated by electron-beam lithography, plasma etching and a two-step oxidation process. This enables photoluminescence (PL) from individual dots at various temperatures to be detected and spectrally resolved using a sensitive charge-coupled device camera-imaging system, as reported previously. The regular array-like arrangement of oxidized pillars containing individual nanocrystals, in principle, enables combined transmission electron microscopy (TEM) and low-temperature PL characterization of the same Si quantum dot. To this end, a technique employing focused ion beam was developed for preparation of the pillar/nanocrystal of interest for TEM. It is shown that silicon quantum dots of several nanometers in size can be characterized using such a method.

  • 7. Vanin, E. V.
    et al.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Khartsev, Sergiy
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101).
    Tarasenko, O.
    Johansson, Petter
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Broadband photoluminescence from pulsed laser deposited Er2O3 films2006In: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 121, no 2, p. 256-258Article in journal (Refereed)
    Abstract [en]

    Photoluminescence (PL) with the bandwidth of 45 nm (1523-1568 nm, at the level of 3 dB) was observed in amorphous Er2O3 films grown on to the quartz substrate by pulsed laser ablation of erbium oxide stoichiometric target. Optical transmission spectrum has been fitted to Swanepoel formula to determine the dispersion of refractive index and to extract resonance absorption peaks at 980 and 1535 nm. The maximum gain coefficient of 800 dB/cm at 1535 nm was estimated using McCumber theory and experimental spectrum of the resonance absorption. In 5.7mm-long waveguide amplifier a theory predicts the spectral gain of 20dB with 1.4dB peak-to-peak flatness in the bandwidth of 31 nm (1532-1563 nm) when 73% of Er3+ ions are excited from the ground state to the I-4(13/2) laser level. Strong broadband PL at room temperature and inherently flat spectral gain promise Er2O3 films for ultra-short high-gain optical waveguide amplifiers and integrated light circuits.

  • 8. Visniakova, Sigita
    et al.
    Urbanaviciute, Indre
    Dauksaite, Lauryna
    Janulevicius, Matas
    Lenkeviciute, Brone
    Sychugov, Ilya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Arlauskas, Ketutis
    Zilinskas, Albinas
    Luminescent benzo- and naphthoquinolines: Synthesis and investigation of photophysical properties2015In: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 167, p. 261-267Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to synthesise new luminescent small molecular weight benzo- and naphthoquinoline derivatives (based on already known synthons) with different substituents (chlorine, tetrazole, iminophosphorane and amine), to characterize them by ultraviolet photoelectron spectroscopy in air (UPS), luminescence and absorption photospectrometry and to investigate the changes in these properties resulted by differences of molecular structure. Measured values of the HOMO, the LUMO energy levels and optical band gap (E-g_opt) were in range E-HOMO = [ - 5, 9; - 5, 5] eV, E-LUMO = [ 3, 6; - 3] eV, E-g_opt = [2; 2, 8] eV. Most of the examined materials showed high intensity fluorescence reaching quantum yields of 49%. Fluorescence peaks of thermally evaporated layers distributed in range of lambda(Layer)=[477; 596] nm - from blue to orange colour while in chloroform solution remained in blue-green interval lambda(Solution)=[471;537] nm. Primary study results of electroluminescence indicate that the materials have a potential to be used in organic optoelectronics.

  • 9. Yang, Jia-Xiang
    et al.
    Li, Lin
    Wang, Cai-Xia
    Tian, Yu-Peng
    Wu, Fei
    Xing, Xiao-Juan
    Wang, Chuan-Kui
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Tang, Huo-Hong
    Huang, Wen-Hao
    Tao, Xu-Tang
    Jiang, Min-Hua
    Facile synthesis, optical properties and theoretical calculation of two novel two-photon absorption chromophores2010In: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 130, no 4, p. 654-659Article in journal (Refereed)
    Abstract [en]

    Two heterocycle-based derivatives that can be used as two-photon absorption chromophore, 9-butyl-3-(2,6-diphenylpyridin-4-yl)-9H-carbazole (BDPYC) and 9-butyl-3-(4-(2, 6-diphenylpyridin-4-yl)styryl)-9H-carbazole (BDPSC) have been successfully synthesized and fully characterized by elemental analysis, IR, H-1 NMR, C-13 NMR and MS. The molecules possess D-pi-A structures, but have different pi bridge. The 9-butylcarbazole is used as a donor (D), and the pyridine ring is used as an acceptor (A). One- and two-photon absorption and excited fluorescence properties in various solvents were experimentally investigated. Two-photon initiated optical data recording experiments have been carried Out under 740 nm laser radiation, and the possible mechanism of optical data storage is discussed based on theoretical calculations.

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