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- 저자 : L. Vijayalakshmi (검색결과 4 건)
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( K Naveen Kumar ),( L. Vijayalakshmi ),강미숙 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1
We have synthesized Eu<sup>3+</sup>: PVA, Gd<sup>3+</sup>: PVA, Gd<sup>3+</sup>+Eu<sup>3+</sup>: PVA and Gd<sup>3+</sup>+Eu<sup>3+</sup>+ TiO<sub>2</sub> nanoparticles: PVA polymer films by solution casting method. Eu<sup>3+</sup> doped PVA polymer films displayed a red emission at 618 nm (<sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>2</sub>) under 396 nm (<sup>7</sup>F<sub>0</sub>→<sup>5</sup>L<sub>6</sub>) of excitation. Upon co-doping with Gd<sup>3+</sup> to Eu<sup>3+</sup>: PVA polymer film, it exhibits enriched red emission than singly doped Eu<sup>3+</sup>: PVA under 270 nm of excitation due to energy transfer from Gd<sup>3+</sup> to Eu<sup>3+</sup> ions. After dispersion of TiO<sub>2</sub> NPs in the co-doped Gd<sup>3+</sup>+Eu<sup>3+</sup>: PVA polymer films, the PL properties of Eu<sup>3+</sup> are remarkably enhanced. Red emission of Eu<sup>3+</sup> is significantly enhanced though an efficient ET process from Gd<sup>3+</sup> to Eu<sup>3+</sup> and TiO<sub>2</sub> NPs to Eu<sup>3+</sup>. These polymer nanocomposite films could be suggested as promising candidates for red luminescent photonic devices.
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Kumar, K. Naveen,Vijayalakshmi, L.,Choi, Jungwook,Kim, Jong Su Elsevier 2019 Journal of alloys and compounds Vol.787 No.-
<P><B>Abstract</B></P> <P>Individually and doubly doped Ce<SUP>3+</SUP>/Eu<SUP>3+</SUP>:CaLa<SUB>2</SUB>ZnO<SUB>5</SUB> (CLZO) phosphors were synthesized by a conventional sol-gel method as highly efficient luminescence-based phosphor materials. X-ray diffraction and field-emission scanning electron microscope were used to analyze the structural and morphological properties. The elements and their ionic states were determined by energy-dispersive spectroscopy and X-ray photoelectron spectroscopy studies, respectively. The assignment of the functional groups was analyzed using Fourier-transform infrared spectral studies. Bright red emission was obtained from Eu<SUP>3+</SUP>-doped CLZO phosphors due to its hypersensitive transition of <SUP>5</SUP>D<SUB>0</SUB>→<SUP>7</SUP>F<SUB>2</SUB> at 626 nm with a royal blue excitation source. By increasing the Eu<SUP>3+</SUP> content, the emission features were rapidly enhanced. Moreover, the red emission related to Eu<SUP>3+</SUP> was further increased by the addition Ce<SUP>3+</SUP> ions as a co-dopant along with Eu<SUP>3+</SUP> in the CLZO matrix due to energy transfer. The energy migration from Ce<SUP>3+</SUP> to Eu<SUP>3+</SUP> is systematically illustrated by several fluorescent approaches, such as photoluminescence analysis, spectral overlap, CIE coordinates, lifetime dynamics, luminescence quantum yields, and color purity. Surprisingly, the CIE coordinates were very close to the NTSC coordinate values. Based on the results, these phosphors could be suitable materials for luminescence-based optoelectronic devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dazzling red emission is obtained from Ce<SUP>3+</SUP>/Eu<SUP>3+</SUP>: CaLa<SUB>2</SUB>ZnO<SUB>5</SUB> phosphors. </LI> <LI> Red emission of Eu<SUP>3+</SUP> was remarkably enhanced by co-doping with Ce<SUP>3+</SUP>. </LI> <LI> Effective sensitization of Ce<SUP>3+</SUP> ions and enhanced quantum yield have been elucidated. </LI> <LI> Energy transfer from Ce<SUP>3+</SUP> to Eu<SUP>3+</SUP> ions by several fluorescence dynamics. </LI> <LI> Meritorious CCT, CIE coordinates and high red color purity have obtained. </LI> </UL> </P>
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K. Naveen Kumar,R. Padma,L. Vijayalakshmi,강미숙 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.45 No.-
Red emission was obtained from rare earth doped polymer nanocomposites, namely, composites ofpolyvinyl-alcohol (PVA) co-doped with Gd3+ and Eu3+ and embedded with TiO2 nanoparticles (TiO2NP),under ultraviolet (UV) excitation. We successfully synthesized Eu3+: PVA, Gd3+: PVA, (Gd3+ + Eu3+): PVA,and (Gd3+ + Eu3+ + TiO2NP): PVAfilms by solution casting method. From X-ray diffraction patterns andFourier-transform infrared spectral profiles, the structural details of thefilms and the ion–polymerinteraction mechanism responsible for their formation were systematically analyzed. The thermalstability and decomposition dynamics of the prepared samples were evaluated by thermogravimetry anddifferential thermal analysis. Pertinent optical absorption bands related to Eu3+ and Gd3+ ions in thepolymer composites were observed and assigned to the corresponding electronic transitions. The PVAfilm containing different concentrations of the Eu3+ dopant displayed red emission at 618 nm (5D0!7F2)under UV excitation at 396 nm (7F0!5L6). Upon co-doping with Gd3+ to form the (Gd3+ + Eu3+): PVAfilm,it exhibited red emission that was stronger than that from the singly doped Eu3+: PVAfilm under 270 nmexcitation because of the energy transfer from Gd3+ to Eu3+ ions. After the TiO2 nanoparticles were evenlydispersed in the co-doped (Gd3+ + Eu3+): PVAfilms, the photoluminescence properties were remarkablyenhanced and prominent red emission was observed under 274 nm excitation. The red emission of Eu3+was significantly enhanced through an efficient energy-transfer process from the Gd3+ ions to Eu3+ ionsand from the TiO2 nanoparticles to Eu3+ ions. A possible energy-transfer mechanism was clearlydemonstrated by severalfluorescent methods and lifetime decay dynamics. Based on the above results,these polymer compositefilms are promising candidates for red luminescent photonic devices.
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