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Author: search.filters.author.Rajaramakrishna, R.Subject: search.filters.subject.photoluminescence

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    Eu-Doped Gd2MoB2O9 Phosphors for Latent Fingerprints Detection
    (2022-01-01)
    Chamchoi, N.
    ;
    Sangwaranatee, N.
    ;
    Rajaramakrishna, R.
    ;
    Kim, H. J.
    ;
    Chaemlek, O.
    The luminescent powders from rare-earth ions doped oxides have been successfully used for latent fingerprint detection due to high efficiency, high contrast and low background interface. The Gd<inf>2</inf>MoB<inf>2</inf>O<inf>9</inf>:Eu<sup>3+</sup> phosphors with varying compositions of Eu<sup>3+</sup>ions were synthesized by solid state reaction method. These phosphors were investigated by X-ray diffraction (XRD), diffuse reflectance spectroscopy, photoluminescence (PL), and decay curves studies. Multiphoton relaxation decay rate and coupling strength was evaluated using phonon side band spectrum showing 0.4 mol% doped samples show less non radiative decay rate. The 0.40 mol% of Eu<sup>3+</sup> ion concentration doped in the Gd<inf>2</inf>MoB<inf>2</inf>O<inf>9</inf> host lattice show highest photoluminescence emission intensity at 613 nm, in orange red region, monitored at 394 nm excitation. The Gd<inf>2</inf>MoB<inf>2</inf>O<inf>9</inf>:Eu<sup>3+</sup> phosphors samples were optimized to 900 °C sintering temperature and optimum milling time at 3 min in the present work. The latent fingerprints detection that developed from Gd<inf>2</inf>MoB<inf>2</inf>O<inf>9</inf>:Eu<sup>3+</sup> phosphors in this work exhibited clearly ridge characteristics under UV illumination. The results revealed thatGd<inf>2</inf>MoB<inf>2</inf>O<inf>9</inf>:Eu<sup>3+</sup> phosphors are potential practical forensic science applications.
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    White Emission from Li2O-BaO-Bi2O3-P2O5 Glass Doped with Dy3+ for Optical Condensed Material Applications
    (2021-01-01)
    Tongdang, J.
    ;
    Chanthima, N.
    ;
    Kiwsakunkarn, N.
    ;
    Tariwong, Y.
    ;
    Rajaramakrishna, R.
    Dy<sup>3+</sup>-doped lithium barium bismuth phosphate glasses were synthesized by the melt-quenching. The structural characteristics of the synthesized glasses were investigated by Fourier transform infrared (FTIR) spectroscopy. Symmetric and asymmetric vibrations of phosphorous oxygen groups were prominent bands in the FTIR spectra. Judd–Ofelt theory have been evaluated by the intensities of absorption bands in order to calculate oscillator strength (f). Luminescence intensity increases with increase in BaO content due to substitution of Ba<sup>2+</sup> replacing Bi<sup>3+</sup> which lead more void spaces providing enough space for Dy<sup>3+</sup> ions to fit in. The branching ratio β parameter was distinguished to be maximum for the emission transition of <sup>4</sup>F<inf>9/2</inf> → <sup>6</sup>H<inf>13/2</inf> with the values of 0.59. LBBPDy glasses reveal an ideal warm white region when observed in CIE diagram. Our investigation reveals that the synthesized glasses may be utilized as a solid-state lighting material in various technological and industrial applications.