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Kumar, K. Naveen,Kim, Jong Su,Cho, Migyung,Shim, Jaesool,Gupta, Bipin Kumar,Kang, Misook ELSEVIER SCIENCE 2017 Journal of Alloys and Compounds Vol.721 No.-
<P><B>Abstract</B></P> <P>A bright novel red emission was obtained from Eu<SUP>3+</SUP>: CaLa<SUB>2</SUB>ZnO<SUB>5</SUB> (CLZO) Phosphors under visible excitation. We have successfully synthesized Eu<SUP>3+</SUP>: CLZO Phosphors by the solid state reaction method. The phase formation and surface morphological studies were analyzed by X-ray diffraction and Field emission scanning electron microscopy respectively. Thermal analysis was done by TG/DTA. Photoluminescence spectral profiles reveal that the strong red emission has been noticed at 626 nm (<SUP>5</SUP>D<SUB>0</SUB>→<SUP>7</SUP>F<SUB>2</SUB>) from the Eu<SUP>3+</SUP>: CLZO Phosphors under the excitation of 467 nm. The emission and excitation spectral profiles were systematically analyzed and their bands were assigned with corresponding electronic transitions. Upon increasing the Eu<SUP>3+</SUP> concentration, the photoluminescence performance has also been increased remarkably. The optimized concentration of the Eu<SUP>3+</SUP> was noticed at 14 mol%. Upon co-doping with Dy<SUP>3+</SUP> ions to Eu<SUP>3+</SUP>: CLZO Phosphors, the red emission pertaining to Eu<SUP>3+</SUP> was appreciably enhanced through energy transfer form Dy<SUP>3+</SUP> to Eu<SUP>3+</SUP> ions. The energy transfer mechanism was substantiated by several fluorescent methods. The prominent <I>red</I> emission of the Dy<SUP>3+</SUP>/Eu<SUP>3+</SUP>: CLZO Phosphors under blue excitation which suggests that these phosphor materials could be promising candidates for red luminescent optical devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dazzling <I>red</I> emission is observed from Eu<SUP>3+</SUP>/Dy<SUP>3+</SUP>:CaLa<SUB>2</SUB>ZnO<SUB>5</SUB> Phosphors. </LI> <LI> Red emission of Eu<SUP>3+</SUP> was significantly enhanced by co-doping with Dy<SUP>3+</SUP>. </LI> <LI> Effective sensitization of Dy<SUP>3+</SUP> ions has been elucidated. </LI> <LI> The energy transfer path way was clearly demonstrated from Dy<SUP>3+</SUP> to Eu<SUP>3+</SUP>. </LI> <LI> CIE coordinates are very close to National Television Standard Committee (NTSC). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kumar, Naveen,Sharma, A.K.,Gangwar, A.K.,Maiti, S.K.,Gupta, O.P.,Kumar, N.,Mathur, R.B. Korean Carbon Society 2006 Carbon Letters Vol.7 No.2
During a 3-year period (2001-2004) 18 animals were surgically treated because of abdominal wall defects (hernia). Out of 18 animals 8 were bovines, 5 caprines and 5 canines. In each case the defect was bridged with carbon fibres. Carbon fibres were placed either in simple interrupted pattern or as mattress overlapping pattern. All the cases were successfully treated and no complication was observed up to six months postoperatively.
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>
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.
Kumar, Naveen,Sharma, A.K.,Maiti, S.K.,Gangwar, A.K.,Kumar, N. Korean Carbon Society 2007 Carbon Letters Vol.8 No.4
During a 4-year period (2001-2005) 09 animals were surgically treated because of abdominal wall defects (hernia). Out of 9 animals 8 were bovines and one caprine. In each case the defect was repaired with carbon fibre mesh. All the cases were successfully treated and no complication was observed up to six months postoperatively.
( 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.
Naveen Kumar,A.K. Sharma,S.K. Maiti,A.K. Gangwar,N. Kumar 한국탄소학회 2007 Carbon Letters Vol.8 No.4
During a 4-year period (2001-2005) 09 animals were surgically treated because of abdominal wall defects (hernia). Out of 9 animals 8 were bovines and one caprine. In each case the defect was repaired with carbon fibre mesh. All the cases were successfully treated and no complication was observed up to six months postoperatively.