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Vidya Y.S.,LBSGFGC | Anantharaju K.S.,East-West Center | Nagabhushana H.,Tumkur University | Sharma S.C.,Chhattisgarh Swami Vivekananda Technical University
Journal of Alloys and Compounds | Year: 2014

Eco-friendly, cost effective and bio template route was used for the preparation of cubic Gd2O3:Eu3+ nanophosphors using Euphorbia tirucalli (E. tirucalli) plant latex as fuel. As - formed Gd2O3:Eu3+ (7 mol%, 1-7 ml), calcined Gd2O3:Eu3+ (7 mol%, 1-7 ml) and Gd2O3:Eu3+ (1-11 mol%, 7 ml) samples were characterized using XRD, SEM and UV-Vis absorption spectrophotometer. With increase in latex concentration, the nanophosphor gets transformed from nano plates to rose - like nanoflowers with size varying from 20 to 30 nm. X-ray diffraction pattern of as - formed product shows hexagonal Gd (OH)3: Eu3+ phase and it converts to pure cubic phase of Gd2O3:Eu3+ on calcination at 600 °C for 3 h. Rietveld refinement of Gd2O3:Eu3+ (7 mol%, 7 ml) revealed the presence of cations in the 8b (0.25, 0.25, 0. 25) and 24d positions (-0.0287, 0.00, 0. 25) and the anions in the 48e positions (0.39, 0.15, 0. 37) with space group Ia-3(206). The photoluminescence intensities of transitions between different J levels depend on the symmetry of the local environment of Eu3+ ion activators and the high ratio of intensity of (5D0 → 7F2) and (5D0 → 7F1) provides the conclusion that Eu3+ ion occupies sites with a low symmetry and without an inversion centre. The chromaticity and the CIE coordinates were very close to the standard red color region. The absorption observed in the excitation spectra shows the suitability of the nanophosphor obtained in this study for getting excited in UV, NUV and visible regions for variety of display applications. Further, the Gd2O3:Eu3+ (7 mol%, 1-7 ml) samples were experimented towards the photocatalytic behavior on Congo red (CR) and correlated with emission of PL intensity. The decolorization of dye was found to decreased from 83 to 54% with increase in the plant latex concentration. © 2014 Elsevier B.V. All rights reserved.

Suresh D.,Tumkur University | Shobharani R.M.,Tumkur University | Nethravathi P.C.,Tumkur University | Pavan Kumar M.A.,Tumkur University | And 3 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2015

We report green synthesis of multifunctional ZnO nanoparticles (NPs) using Artocarpus gomezianus (AG) extract as fuel by solution combustion synthesis. The formation of NPs was confirmed by powder XRD, SEM, TEM and UV-Visible studies. The NPs were subjected for photoluminescence, photodegradative and antioxidant studies. XRD data reveals that the ZnO NPs possess wurtzite structure. UV-Visible spectrum shows absorbance maximum at 370 nm which corresponds to the energy band gap of 3.3 eV. Morphology studies indicate the highly porous nature of the NPs. PL spectra of NPs found to display very interesting blue, green and red emissions upon excitation at 325 nm. The NPs exhibit potential photocatalytic activity towards the degradation of methylene blue (MB) dye upon exposure to sun light and UV light. ZnO NPs found to have considerable antioxidant activity against DPPH (2,2-diphenyl-1-picrylhydrazyl) free radicals. The study successfully demonstrates a simple and eco-friendly method for the synthesis of efficient multifunctional ZnO nanoparticles using green synthetic approach. © 2015 Elsevier B.V. All rights reserved.

Ravikumar B.S.,Tumkur University | Nagabhushana H.,Tumkur University | Sharma S.C.,Chhattisgarh Swami Vivekananda Technical University | Vidya Y.S.,LBSGFGC | Anantharaju K.S.,East-West Center
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2015

ZnAl2O4:Cr3+ nanophosphors were synthesized for the first time by a simple and environment friendly route using Calotropis procera milk latex as fuel. The structural and surface morphological studies were carried out using powder X-ray diffraction (PXRD), scanning electron microscopy and transmission electron microscopy techniques. The photoluminescence (PL) properties of ZnAl2O4:Cr3+ as a function of dopant concentration and calcination temperature was studied in detail. The PXRD patterns and Rietveld confinement confirmed the cubic crystal system with space group Fd-3m. The crystallite size estimated from Scherrer's and W-H plots was found to be in the range of 16-26 nm. The PL spectrum shows an intense peak at ∼688 and ∼699 nm assigned to spin - forbidden 2Eg → 4A2g transition of Cr3+ ions. The PL measurements for two excitations (∼410 and 527 nm) and with respect to calcination temperature indicated no significant change in the shape and position of emission peak except PL intensity. The CIE chromaticity coordinates lies well within the white region. Thermoluminescence (TL) studies revealed well resolved glow peak at ∼212 °C with a small shoulder at 188 and 233 °C. The glow peak intensity at ∼212 °C increases linearly with γ-dose which suggest ZnAl2O4:Cr3+ is suitable candidate for radiation dosimetric applications. The activation energy (E in eV), order of kinetics (b) and Frequency factor (s) were estimated using glow peak shape method. © 2014 Elsevier B.V. All rights reserved.

Suresh D.,Tumkur University | Nethravathi P.C.,Tumkur University | Udayabhanu A.,Tumkur University | Nagabhushana H.,Tumkur University | And 2 more authors.
Ceramics International | Year: 2014

Spinach (Spinacia oleracea) leaves mediated efficient green reduction of graphene oxide (GO) was achieved to produce multifunctional reduced graphene oxide (rGO). GO was mixed with spinach juice and refluxed for 30 min at 100 °C. Powder XRD, TEM and UV-visible techniques demonstrate the formation of well-organized layered rGO. Industrially important carcinogenic Methylene blue (MB) and Malachite green (MG) dyes absorption experiments with rGO were performed under dark condition. Complete removal of MB and MG occurs in spans of 60 and 40 min respectively in the presence of 20 mg rGO. Potential antioxidant activity was exhibited by the rGO with 50% inhibitory concentration of 1590 μg/mL against the scavenging of 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radicals. Environment friendly, economical and facile reduction method is suggested for the efficient reduction of GO. © 2014 Elsevier Ltd and Techna Group S.r.l.

Suresh D.,Tumkur University | Udayabhanu,Tumkur University | Pavan Kumar M.A.,Tumkur University | Nagabhushana H.,Tumkur University | And 2 more authors.
Materials Letters | Year: 2015

Abstract A simple and efficient method of reduction for the preparation of reduced graphene oxide (rGO) from graphene oxide (GO) using Cinnamon (Cinnamomum zeylanicum) extract is reported. The reduction of GO was confirmed by XRD, TEM and UV-visible techniques. The rGO has shown to possess significantly high dye removal property of Malachite green (MG) and Methylene blue (MB) dyes in the absence of UV or Sun light. Further, it showed considerable antioxidant activity against scavenging of 1, 1-Diphenyl-2-picrylhydrazyl (DPPH) free radicals. The study illustrates an environment friendly green method for the efficient reduction of GO. © 2015 Elsevier B.V. All rights reserved.

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