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Ramakrishna G.,Tumkur University | Nagabhushana H.,Tumkur University | Prasad B.D.,BMS Institute of Technology and Management | Vidya Y.S.,Lal Bahadur Shastry Government First Grade College | And 4 more authors.
Journal of Luminescence | Year: 2017

A series of Eu3+ (1–7 mol %) doped Y2SiO5 red nanophosphors were prepared by eco-friendly combustion route using Calotropis gigantea latex as a fuel. The obtained nanophosphors were calcined at 1000 °C and characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Raman studies, UV–Visible and photoluminescence (PL) spectroscopic techniques. PXRD were used to determine the structure of the phosphors, showing that the product was monoclinic phase of X1 type Y2SiO5 having a phase group P21/c n. 14. The PL properties of samples exhibited an intense broad red emission band upon excitation with 397 nm, with a peak at 612 nm, color coordinates of (0.5866, 0.4026), and average correlated color temperature ~2018.5 K. Based on Judd–Ofelt (J–O) theory, the intensity parameters (Ω2 and Ω4) were evaluated from the emission spectra of Y2SiO5: Eu3+ (1–7 mol %) nanophosphors. The registered trend (Ω2<Ω4) reveals the relatively high symmetry environment around the rare earth ion (RE) site in Y2SiO5 as compared to other host matrix. The results show that prepared samples were compared with the commercially available compound and founds as par to the commercial compound hence it may be used as a potential red phosphors for near UV excited White LEDs applications. © 2016 Elsevier B.V.


Malleshappa J.,Tumkur University | Nagabhushana H.,Tumkur University | Sharma S.C.,Dr Hari Singh Gour University | Vidya Y.S.,Lal Bahadur Shastry Government First Grade College | And 6 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2015

Spherical shaped cerium dioxide (CeO2) nanoparticles (NPs) were synthesized via bio mediated route using Leucas aspera (LA) leaf extract. The NPs were characterized by PXRD, SEM, UV-Visible techniques. Photoluminescence (PL), photocatalysis and antibacterial properties of NPs were studied. PXRD patterns and Rietveld analysis confirm cubic fluorite structure with space group Fm-3m. SEM results evident that morphology of the NPs was greatly influenced by the concentration of LA leaf extract in the reaction mixture. The band gap energy of the NPs was found to be in the range of 2.98-3.4 eV. The photocatalytic activity of NPs was evaluated by decolorization of Rhodamine-B (RhB) under UVA and Sun light irradiation. CeO2 NPs show intense blue emission with CIE coordinates (0.14, 0.22) and average color coordinated temperature value ∼148,953 K. Therefore the present NPs quite useful for cool LEDs. The superior photocatalytic activity was observed for CeO2 NPs with 20 ml LA under both UVA and Sunlight irradiation. The enhanced photocatalytic activity and photoluminescent properties were attributed to defect induced band gap engineered CeO2 NPs. Further, CeO2 with 20 ml LA exhibit significant antibacterial activity against Escherichia coli (EC) and Staphylococcus aureus (SA). These findings show great promise of CeO2 NPs as multifunctional material for various applications. © 2015 Elsevier B.V. All rights reserved.


Prasanna Kumar J.B.,GFGC Tumkur | Prasanna Kumar J.B.,Sathyabama University | Ramgopal G.,Maharanis Science College | Vidya Y.S.,Lal Bahadur Shastry Government First Grade College | And 7 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2015

Facile and green route was employed for the synthesis of Y2O3:Dy3+ (1-11 mol%) nanostructures (NSs) using Aloe vera gel as fuel. The formation of different morphologies of Y2O3:Dy3+ NSs were characterized by SEM, TEM and HRTEM. PXRD data and Rietveld analysis evident the formation of single phase Y2O3 with cubic crystal structure. The influence of Dy3+ ion concentration on the structure morphology, UV absorption, PL emission and photocatalytic activity of NSs were investigated. NSs exhibited an intense warm white emission with CIE chromaticity coordinates (0.32, 0.33) and average CCT value ∼5525 K which corresponds to vertical day light. The control of Dy3+ ion on Y2O3 matrix influences the photocatalytic decolorization of Metanil Yellow as a model compound was evaluated. The enhanced photocatalytic activities of core shell structured Y2O3:Dy3+ (1 mol%) was attributed to co-operation effect of dopant concentration, crystallite size, textural properties and capability for reducing electron-hole pair recombination. Further, the recycling catalytic ability of Y2O3:Dy3+ (1 mol%) nanostructure was also evaluated and found promising photocatalytic performance with negligible decrease in decolorization efficiency even after sixth successive cyclic runs. Considering its green, facile synthesis and recyclable feature from an aqueous solution, the present Y2O3:Dy3+ (1 mol%) nanophosphor can be considered as one of the ideal photocatalyst for various potential applications. © 2015 Elsevier B.V. All rights reserved.


Kavyashree D.,Channabasaveshwara Institute of Technology | Kumari R.A.,Sree Siddaganga College for Women | Nagabhushana H.,Tumkur University | Sharma S.C.,Dr Hari Singh Gour University | And 6 more authors.
Journal of Luminescence | Year: 2015

Abstract Europium ions doped (1-11 mol%) ZnO nanoparticles (NPs) were synthesized by a facile green synthesis method using Guizotia abyssinica as fuel. The obtained ZnO:Eu3+ (1-11 mol%) NPs were characterized by using powder X-ray diffraction studies (PXRD), scanning electron microscopy (SEM) and photoluminescence (PL) techniques. The dependency of dopant concentration on the crystal structure, surface morphology and luminescence properties was discussed in detail. The particle size and the existing states of the ions within the material were analyzed by TEM and XPS respectively. The PL emission of ZnO:Eu3+ NPs shows characteristics transitions of Eu3+ ions. It has been demonstrated that intrinsic defects may act as the media in the energy transfer process from the ZnO host to Eu3+ ions. The CIE chromaticity and CCT confirms the phosphor material as orange red emitting hence it was quite useful in display applications. © 2015 Elsevier B.V.


PubMed | Dr Hari Singh Gour University, East West Institute of Technology, Dr dananda Maiya Center For Food Science Research, Lal Bahadur Shastry Government First Grade College and 2 more.
Type: | Journal: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy | Year: 2015

Green synthesis of multifunctional Zinc oxide nanoparticles (NPs) with a variety of morphologies were achieved by low temperature solution combustion route employing neem (Azadirachta indica) extract as fuel. The nanoparticles were characterized by PXRD, FTIR, XPS, Raman and UV-Visible spectroscopic studies. The Morphologies were studied by SEM and TEM analysis. The NPs were subjected for photoluminescence, photocatalytic, antibacterial and antioxidant activity studies. PXRD pattern confirmed the hexagonal wurtzite structure of the product. SEM images indicated the transformation of mushroom like hexagonal disks to bullets, buds, cones, bundles and closed pine cone structured NPs with increase in the concentration of neem extract in reaction mixture. The NPs exhibited prominent green emission due to the presence of intrinsic defect centers. The as-formed bullet shaped ZnO with 4ml of neem extract was found to decolorize Methylene blue (MB) under Sunlight and UV light irradiation. The antibacterial studies indicated that ZnO NPs of concentration 500, 750 and 1000g resulted in significant antibacterial activity on Klebsiella aerogenes and Staphylococcus aureus but not against Escherichia coli and Pseudomonas aeruginosa in agar well diffusion method. Further, ZnO NPs exhibited significant antioxidant activity against scavenging DPPH free radicals. The current investigation demonstrated green engineering method for the synthesis of multifunctional ZnO NPs with interesting morphologies using neem extract.


PubMed | Tumkur University, Dr Hari Singh Gour University, East-West Center, Indian Institute of Science and Lal Bahadur Shastry Government First Grade College
Type: | Journal: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy | Year: 2015

MgO:Fe(3+) (0.1-5 mol%) nanoparticles (NPs) were synthesized via eco-friendly, inexpensive and simple low temperature solution combustion route using Aloe vera gel as fuel. The final products were characterized by SEM, TEM and HRTEM. PXRD data and Rietveld analysis revealed the formation of cubic system. The influence of Fe(3+) ion concentration on the structure morphology, UV absorption, PL emission and photocatalytic activity of MgO:Fe(3+) NPs were investigated. The yellow emission with CIE chromaticity coordinates (0.44, 0.52) and average correlated color temperature value was found to be 3540 K which corresponds to warm light of NPs. The control of Fe(3+) on MgO matrix influences the photocatalytic decolorization of methylene blue (MB) under UV light. The enhanced photocatalytic activity of MgO:Fe(3+) (4 mol%) was attributed to dopant concentration, effective crystallite size, textural properties, decreased band gap and capability for reducing the electron-hole pair recombination. Further, the trends of inhibitory effect in the presence of different radical scavengers were explored. These findings open up new avenues for the exploration of Fe-doped MgO in eco-friendly water applications and in the process of display devices.


Prasanna Kumar J.B.,GFGC Tumkur | Prasanna Kumar J.B.,Sathyabama University | Ramgopal G.,Maharanis Science College | Vidya Y.S.,Lal Bahadur Shastry Government First Grade College | And 6 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2015

We report the synthesis of Y2O3: Eu3+ (1-11 mol%) nanoparticles (NPs) with different morphologies via eco-friendly, inexpensive and simple low temperature solution combustion method using Aloe Vera gel as fuel. The formation of different morphologies of Y2O3: Eu3+ NPs were characterized by PXRD, SEM, TEM, HRTEM, UV-Visible and PL techniques. The PXRD data and Rietveld analysis confirms the formation of single phase Y2O3 with cubic crystal structure. The influence of Eu3+ ion concentration on the morphology, UV-Visible absorption, PL emission and photocatalytic activity of Y2O3: Eu3+ nanostructures were investigated. Y2O3: Eu3+ NPs exhibit intense red emission with CIE chromaticity coordinates (0.50, 0.47) and correlated color temperature values at different excitation ranges from 1868 to 2600 K. The control of Eu3+ ion on Y2O3 matrix influences the photocatalytic decolorization of methylene blue (MB) as a model compound was evaluated under UVA light. Enhanced photocatalytic activity of conical shaped Y2O3: Eu3+ (1 mol%) was attributed to dopant concentration, crystallite size, textural properties and capability of reducing the electron-hole pair recombination. The trend of inhibitory effect in the presence of different radical scavengers followed the order SO4 2- > Cl- > C2H5OH > HCO3 - > CO3 2-. These findings show great promise of Y2O3: Eu3+ NPs as a red phosphor in warm white LEDs as well as eco-friendly heterogeneous photocatalysis. © 2015 Elsevier B.V. All rights reserved.


PubMed | Sathyabama University, Chhattisgarh Swami Vivekananda Technical University, East-West Center, Maharanis Science College and 4 more.
Type: | Journal: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy | Year: 2015

We report the synthesis of Y2O3: Eu(3+) (1-11 mol%) nanoparticles (NPs) with different morphologies via eco-friendly, inexpensive and simple low temperature solution combustion method using Aloe Vera gel as fuel. The formation of different morphologies of Y2O3: Eu(3+) NPs were characterized by PXRD, SEM, TEM, HRTEM, UV-Visible and PL techniques. The PXRD data and Rietveld analysis confirms the formation of single phase Y2O3 with cubic crystal structure. The influence of Eu(3+) ion concentration on the morphology, UV-Visible absorption, PL emission and photocatalytic activity of Y2O3: Eu(3+) nanostructures were investigated. Y2O3: Eu(3+) NPs exhibit intense red emission with CIE chromaticity coordinates (0.50, 0.47) and correlated color temperature values at different excitation ranges from 1868 to 2600 K. The control of Eu(3+) ion on Y2O3 matrix influences the photocatalytic decolorization of methylene blue (MB) as a model compound was evaluated under UVA light. Enhanced photocatalytic activity of conical shaped Y2O3: Eu(3+) (1 mol%) was attributed to dopant concentration, crystallite size, textural properties and capability of reducing the electron-hole pair recombination. The trend of inhibitory effect in the presence of different radical scavengers followed the order SO4(2-)>Cl(-)>C2H5OH>HCO3(-)>CO3(2-). These findings show great promise of Y2O3: Eu(3+) NPs as a red phosphor in warm white LEDs as well as eco-friendly heterogeneous photocatalysis.


Gurushantha K.,East-West Center | Anantharaju K.S.,East-West Center | Nagabhushana H.,Tumkur University | Sharma S.C.,Chhattisgarh Swami Vivekananda Technical University | And 5 more authors.
Journal of Molecular Catalysis A: Chemical | Year: 2014

Cubic ZrO2: Fe3+ (0.5-4 mol%) nanoparticles (NPs) were synthesized via bio-inspired, inexpensive and simple route using Phyllanthus acidus as fuel. PXRD, SEM, TEM, FTIR, UV absorption and PL studies were performed to ascertain the formation of NPs. Rietveld analysis confirmed the formation of cubic structure. The influence of Fe3+ on the structure, morphology, UV absorption, PL emission and photocatalytic activity of NPs were investigated. The CIE chromaticity coordinates (0.36, 0.41) show that NPs could be a promising candidate for white LEDs. The influence of Fe3+ on ZrO2 matrix for photocatalytic degradation of AO7 was evaluated under UVA and Sunlight irradiation. The enhanced photocatalytic activity of spherical shaped ZrO2: Fe3+ (2 mol%) under UVA light was attributed to dopant concentration, crystallite size, narrow band gap, textural properties and capability for reducing the electron-hole pair recombination. The trend of inhibitory effect in the presence of different radical scavengers were followed the order SO4 2- > Cl- > C2H5OH > HCO3 - > CO3 2-. The recycling catalytic ability of the ZrO2: Fe3+ (2 mol%) was also evaluated with a negligible decrease in the degradation efficiency even after the sixth successive run. © 2014 Elsevier B.V. All rights reserved.


Vidya Y.S.,Lal Bahadur Shastry Government First Grade College | Anantharaju K.S.,East-West Center | Nagabhushana H.,Tumkur University | Sharma S.C.,Chhattisgarh Swami Vivekananda Technical University | And 4 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2015

Novel crystalline tetragonal ZrO2: Eu3+ phosphors were prepared by a facile and efficient low temperature solution combustion method at 400 ± 10 °C using oxalyl dihydrazide (ODH) as fuel. The powder X-ray diffraction patterns and Rietveld confinement of as formed ZrO 2: Eu3+ (1-11 mol%) confirmed the presence of body centered tetragonal phase. The crystallite size estimated from Scherrer's and W-H plots was found to be in the range of 7-17 nm. These results were in good agreement with transmission electron microscopy studies. The calculated microstrain in most of the planes indicated the presence of tensile stress along various planes of the particles. The observed space group (P42/nmc) revealed the presence of cations in the 2b positions (0.75, 0.25, 0.25) and the anions in the 4d positions (0.25, 0.25, 0.45). The optical band gap energies estimated from Wood and Tauc's relation was found to be in the range 4.3-4.7 eV. Photoluminescence (PL) emission was recorded under 394 and 464 nm excitation shows an intense emission peak at 605 nm along with other emission peaks at 537, 592, 605 and 713 nm. These emission peaks were attributed to the transition of 5D0 → 7FJ (J = 0, 1, 2, 3) of Eu3+ ions. The high ratio of Intensity of (5D0 → 7F2) and (5D0 → 7F1) infers that Eu3+ occupies sites with a low symmetry and without an inversion center. CIE color coordinates indicated the red regions which could meet the needs of illumination devices. © 2014 Elsevier B.V. All rights reserved..

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