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Shivram M.,Jawaharlal Nehru Technological University Anantapur | Prashantha S.C.,East West Institute of Technology | Nagabhushana H.,Tumkur University | Sharma S.C.,BMS College of Engineering | And 2 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy

Nanoparticles of Eu3+ doped (1-9 mol%) CaTiO3 were prepared using low temperature (500 C) solution combustion technique using metal nitrates as precursors and urea as fuel. The powder X-ray diffraction patterns of the as-formed products show single orthorhombic phase. The crystallite size was estimated using Scherrer's method and found to be in the range 40-45 nm. The effect of Eu3+ ions on luminescence characteristics of CaTiO 3 was studied and the results were discussed in detail. The phosphors exhibit bright red emission upon 398 nm excitation. The characteristic emission peaks recorded at ∼540, 593, 615, 653, 696 and 706 nm (5D 0 → 7Fj=0,1,2,3,4,5) were attributed to Eu3+ ions. The electronic transition corresponding to 5D0 → 7F2 (615 nm) was stronger than the magnetic dipole transition 5D0 → 7F1 of Eu3+ ions (596 nm). The CIE chromaticity co-ordinates were calculated from emission spectra, the values (x,y) very close to NTSC standard value of red emission. Therefore, the present phosphors were highly useful for display applications. © 2013 Elsevier B.V. All rights reserved. Source

Khader K.K.A.,Bharathidasan University | Sajith A.M.,Kannur University | Padusha M.S.A.,Bharathidasan University | Nagaswarupa H.P.,East West Institute of Technology | Muralidharan A.,Kannur University
New Journal of Chemistry

Microwave-mediated, palladium catalyzed C-N bond forming reactions with activated cycloalkenyl nonaflates and enolizable heterocycles using cesium carbonate as a base and a catalytic system employing Pd(OAc)2/ Xantphos or Pd(OAc)2/dppp were found to be effective in driving the reactions to completion. This method resulted in good to excellent yields of the coupled products (22 examples, 25-90%) in short reaction time (30-60 min). Under optimum conditions, cycloalkenyl nonaflates were found to be an effective alternative to analogous triflates in C-N bond forming processes due to their increased stability under the reaction conditions. The use of tetrabutylammonium bromide (Bu4NBr) as an additive in these transformations proved to be effective and resulted in better yields of the coupled products. © 2014 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique. Source

Jnaneshwara D.M.,Tumkur University | Jnaneshwara D.M.,SJB Institute of Technology | Jnaneshwara D.M.,Rashtreeya Vidyalaya College of Engineering | Avadhani D.N.,Rashtreeya Vidyalaya College of Engineering | And 6 more authors.
Journal of Alloys and Compounds

Zinc substituted cobalt ferrite powders {Co(1- x)ZnxFe2O4} (0.0 ≤ x ≤ 0.5) were prepared by the solution combustion method. The structural, morphological, magnetic and electrical properties of as synthesized samples were studied. Powder X-ray diffraction patterns reveals single phase, cubic spinel structure with space group No. Fd3̄m (2 2 7). As zinc concentration increases, the lattice constant increases and the crystallite size decreases. The minimum crystallite size of ∼12 nm was observed for x = 0.5 composition. The synthesized ferrite compounds show ferrimagnetic behavior, with coercivity value of 10779 Oe (Hard ferrite) at 20 K and 1298 Oe (soft ferrite) at room temperature (RT). The maximum saturation magnetization recorded for the Co 0.5Zn0.5Fe2O4 composition was 99.78 emu g-1 and 63.83 emu g-1 at 20 K and RT respectively. The dielectric parameters such as dielectric constant, loss tangent and AC conductivity were determined as a function of frequency at RT. The magnetic and dielectric properties of the samples illustrates that the materials were quite useful for the fabrication of nanoelectronic devices. © 2013 Elsevier B.V. All rights reserved. Source

Malleshappa J.,Tumkur University | Nagabhushana H.,Tumkur University | Prashantha S.C.,East West Institute of Technology | Sharma S.C.,Chhattisgarh Swami Vivekananda Technical University | And 3 more authors.
Journal of Alloys and Compounds

The investigation involves preparation and photoluminescence properties of CeO2:Eu3+ (1-11 mol%) nano phosphors by eco-friendly green combustion route using Euphorbia tirucalli plant latex as fuel. The final product was characterized by powder X-ray diffraction (PXRD), Scanning electron microcopy (SEM) and Transmission electron microscopy (TEM). The PXRD and SEM results reveals cubic fluorite phase with flaky structure. The crystallite size obtained from TEM was found to be ∼20-25 nm, which was comparable to W-H plots and Scherrer's method. Photoluminescence (PL) emission of all the Eu 3+ doped samples shows characteristic bands arising from the transitions of 5D0 → 5FJ (J = 0, 1, 2, 3, 4) manifolds under excitation at 373 and 467 nm excitation. The 5D0 → 7F2 (613 nm) transition often dominate the emission spectra, indicating that the Eu3+ cations occupy a site without inversion center. The highest PL intensity was recorded for 9 mol% Eu3+ ions with 5 ml latex. PL quenching was observed upon further increase in Eu3+ concentration. The international commission on illumination (CIE) chromaticity co-ordinates were calculated from emission spectra, the values (x, y) were very close to national television system committee (NTSC) standard values of pure red emission. The results demonstrate that the synthesized phosphor material could be very useful for display applications. Further, the phosphor material prepared by this method was found to be non toxic, environmental friendly and could be a potential alternative to economical routes. © 2014 Elsevier Inc. All rights reserved. Source

Prashantha S.C.,Bangalore University | Prashantha S.C.,East West Institute of Technology | Lakshminarasappa B.N.,Bangalore University | Singh F.,Inter University Accelerator Center
Journal of Luminescence

Nanoparticles of Mg 2SiO 4:Eu 3 have been prepared by the solution combustion technique and the grain size estimated by PXRD is found to be in the range 40-50 nm. Ionoluminescence (IL) studies of Mg 2SiO 4:Eu 3 pellets bombarded with 100 MeV Si 8 ions with fluences in the range 1.124-22.48×10 12 ions cm -2 are carried out at IUAC, New Delhi, India. Five prominent IL bands with peaks at 580 nm, 590 nm, 612 nm, 655 nm and 705 nm are recorded. These characteristic emissions are attributed to the luminescence centers activated by Eu 3 cations. It is found that IL intensity decreases rapidly in the beginning. Later on, the intensity decreases slowly with further increase of ion fluence. The reduction in the ionoluminescence intensity with increase of ion fluence might be attributed to degradation of Si-O (ν 3) and Si-O (2ν 3) bonds present on the surface of the sample. The red emission with peak at 612 nm is due to characteristic emission of 5D 0→ 7F 2 of the Eu 3 cations. Thermoluminescence (TL) studies of Mg 2SiO 4:Eu 3 pellets bombarded with 100 MeV Si 8 cations with fluences in the range 5×10 11 ions cm -2 to 5×10 13 ions cm -2 are made at RT. Two prominent and well resolved TL glows with peaks at ∼220 °C and ∼370°C are observed. It is observed that TL intensity increases with increase of ion fluence. This might be due to creation of new traps during swift heavy ion irradiation. © 2012 Elsevier B.V. All rights reserved. Source

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