Browsing by Author "Zubareva, Vera"

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    NEW PHOTOLUMINOPHORE NANOCOMPOSITE BASED ON ORGANIC COMPOUND WITH Eu3+ IONS AND COPOLYMER STYRENE-BUTYLMETHACRILATE
    (2009) Iovu, Mihail; Andrieș, Andrei; Buzurniuc, Svetlana; Verlan, Victor; Turta, Constantin; Zubareva, Vera; Caraman, Mihail
    New nanocomposite (NC) material on the base of thenoyltrifluoroacetone (TTA) coordinated with triva- lent europium ions and structured with phenantroline (Eu(TTA)3Phen) and copolymer from styrene and butylmethacrylate (1:1) (SBMA) was prepared. The visible photoluminescence spectra of composites excited with N2-laser (k = 0.337 lm) at room and T = 78 K temperatures were studied. For the Eu(TTA)3- Phen/SBMA nanocomposite material emission bands located at 578, 590, 612, 675 and 705 nm can be attributed to the spin forbidden f–f transitions 5D0 ? 7Fi (i = 0,1,2,3 and 4), respectively. The more inten- sive luminescence band situated at 612 nm with the half width of 3 nm is connected to the Eu3+ ion elec- tronic transition 5D0 ? 7F2. It was shown that the maximum intensity of photoluminescence occurs at the concentration of 15% of the Eu(TTA)3Phen in the SBMA polymer matrix.
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    PHOTOCHROMISM IN SELENE-CONTAINING POLYOXOMETALLATES
    (Academia de Ştiinţe a Moldovei, 2006) Gutsul, Tatiana; Zubareva, Vera; Chiriţa, Arcadii; Fedorov, Vladimir
    Photochromic materials are investigated in last years intensively in connection with prospect of their application in the means of optical holographic and not holographic treatment of information. The photochemistry of the polyoxometallates has been studied and described recently [1, 2]. Earlier we investigated organic-inorganic compositions on the basis of polyoxometallates (POMs) and poly(vinyl alcohol) (PVA), as media for record of the holograms having high resolving power (1000 line\mm), sensitivity 0,2 J/mm2, but poor contrast. Thus, the search of new organicinorganic compositions is of interest. By means of IR, UV and ESR spectroscopy organic -inorganic compositions obtained on the basis of a polyvinylpyrrolidone (PVP) and [Se2W21O69]4-, [Se2W18Cu3O66]12-, [Se2W19 Mo2O69]4- at the all forms of them were investigated. For all investigated compositions the absorption in range 240 nm is characteristic, for the irradiated form - the maximum of absorption is removed (shifted) in range 580-700 nm. The IR spectra of the investigated compositions show four characteristic bands of polyoxometallates in the range of 700-1000 cm-1: νas (W=O), 960 cm-1; νas (W-Ob-W), 890-870 cm-1; νas(W-Oc-W), 750-720 cm-1; νas (Se-O) 830 cm-1 and characteristic bands of polyvinylpyrrolidone (the bands at about 2933-2852, 1687, 1592-1427, corresponding to νC-H, ν C-C, ν C-O, ν O-H, respectively) and also presence of a new band of absorption at 3447 cm-1, corresponding ν (N-H). Results show that polyoxometallates interact with polyvinylpyrrolidone. The composite films exhibit photochromic properties. When irradiated with UV light, the transparent films change from colorless, green or yellow to blue. The photochromism of the composite is due to charge transfer by reduction of polyoxometallates and oxidation of polyvinylpyrrolidone. The mechanism of interaction of polyoxometallates with a polyvinylpyrrolidone as the following photochemical reaction is offered.figure.