S C Sharma

Publications (13)30.16 Total impact

• Source

  Available from: Suriya Murthy

  Article: Effect of Calcination Temperature on Structural, Photoluminescence, and Thermoluminescence Properties of Y2O3:Eu3+ Nanophosphor

  R. Hari Krishna, B. M. Nagabhushana, H. Nagabhushana, N. Suriya Murthy, S. C. Sharma, C. Shivakumara, R. P. S. Chakradhar
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  ABSTRACT: ABSTRACT: Red light emitting cubic Y2O3:Eu3+ nano- phosphors have been synthesized by a low temperature solution combustion method using ethylene diamine tetra acetic acid (EDTA) as fuel. The systematic studies on the effect of calcination temperature on its structural, photo- luminescence (PL), and thermoluminescence (TL) properties were reported. The crystallinity of the samples increases, and the strain is reduced with increasing calcination temperature. SEM micrographs reveal that samples lose their porous nature with an increase in calcination temperature. Photolumines- cence (PL) spectra show that the intensity of the red emission (612 nm) is highly dependent on the calcination temperature and is found to be 10 times higher when compared to as-formed samples. The optical band gap (Eg) was found to reduce with an increase of calcination temperature due to reduction of surface defects. The thermoluminescence (TL) intensity was found to be much enhanced in the 1000 °C calcined sample. The increase of PL and TL intensity with calcination temperature is attributed to the decrease of the nonradiative recombination probability, which occurs through the elimination of quenching defects. The trap parameters(E, b, s) were estimated from Chen’s glow peak shape method and are discussed in detail for their possible usage in dosimetry.
  The Journal of Physical Chemistry C 12/2012; · 4.80 Impact Factor
• Source

  Available from: C. R. Kesavulu

  Article: Structural, EPR, optical and magnetic properties of α-Fe(2)O(3) nanoparticles.

  A A Jahagirdar, N Dhananjaya, D L Monika, C R Kesavulu, H Nagabhushana, S C Sharma, B M Nagabhushana, C Shivakumara, J L Rao, R P S Chakradhar
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  ABSTRACT: α-Fe(2)O(3) nanoparticles were synthesized by a low temperature solution combustion method. The structural, magnetic and luminescence properties were studied. Powder X-ray diffraction (PXRD) pattern of α-Fe(2)O(3) exhibits pure rhombohedral structure. SEM micrographs reveal the dumbbell shaped particles. The EPR spectrum shows an intense resonance signal at g≈5.61 corresponding to isolated Fe(3+) ions situated in axially distorted sites, whereas the g≈2.30 is due to Fe(3+) ions coupled by exchange interaction. Raman studies show A(1g) (225cm(-1)) and E(g) (293 and 409cm(-1)) phonon modes. The absorption at 300nm results from the ligand to metal charge transfer transitions whereas the 540nm peak is mainly due to the (6)A(1)+(6)A(1)→(4)T(1)(4G)+(4)T(1)(4G) excitation of an Fe(3+)-Fe(3+) pair. A prominent TL glow peak was observed at 140°C at heating rate of 5°Cs(-1). The trapping parameters namely activation energy (E), frequency factor (s) and order of kinetics (b) were evaluated and discussed.
  Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 10/2012; 104C:512-518. · 2.10 Impact Factor
• Article: CdSiO(3):Pr(3+) nanophosphor: Synthesis, characterization and thermoluminescence studies.

  D V Sunitha, C Manjunatha, C J Shilpa, H Nagabhushana, S C Sharma, B M Nagabhushana, N Dhananjaya, C Shivakumara, R P S Chakradhar
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  ABSTRACT: A series of Pr(3+) (1-9mol%) doped CdSiO(3) nanophosphors have been prepared for the first time by a low temperature solution combustion method using oxalyldihydrizide (ODH) as a fuel. The final product was characterized by Powder X-ray diffraction (PXRD), Fourier Transform Infrared Spectroscopy (FTIR), scanning electron microscopy (SEM), and UV-Vis spectroscopy. The average crystallite size was calculated using Debye-Scherrer's formula and Williamson-Hall (W-H) plots and found to be in the range 31-37nm. The optical energy band gap (E(g)) of undoped for Pr(3+) doped samples were estimated from Tauc relation which varies from 5.15-5.36eV. Thermoluminescence (TL) properties of Pr(3+) doped CdSiO(3) nanophosphor has been investigated using γ-irradiation in the dose range 1-6kGy at a heating rate of 5°Cs(-1). The phosphor shows a well resolved glow peak at ∼171°C along with shouldered peak at 223°C in the higher temperature side. It is observed that TL intensity increase with increase of Pr(3+) concentration. Further, the TL intensity at 171°C is found to be increase linearly with increase in γ-dose which is highly useful in radiation dosimetry. The kinetic parameters such as activation energy (E), frequency factor (s) and order of kinetics was estimated by Luschiks method and the results are discussed.
  Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 08/2012; 99C:279-287. · 2.10 Impact Factor
• Article: Effect of different fuels on structural, thermo and photoluminescent properties of Gd(2)O(3) nanoparticles.

  N Dhananjaya, H Nagabhushana, B M Nagabhushana, B Rudraswamy, S C Sharma, D V Sunitha, C Shivakumara, R P S Chakradhar
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  ABSTRACT: Gd(2)O(3) nanoparticles (27-60nm) have been synthesized by the low temperature solution combustion method using citric acid, urea, glycine and oxalyl dihydrazide (ODH) as fuels in a short time. The structural and luminescence properties have been carried out using powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), Raman, UV-Vis, photoluminescence (PL) and thermoluminescence (TL) techniques. The optical band gap values were estimated for as formed and 800°C calcined samples. The band gap values in as-formed and calcined samples were found to be in the range 4.89-5.59eV. It is observed that, the band gap values are lower for as-formed products and it has been attributed to high degree of structural defects. However, in calcined samples, structure becomes more order with reduced structure defects. Upon 270nm excitation, deep blue UV-band at ∼390nm along with blue (420-482nm), green (532nm) and red emission (612nm) was observed. The 390nm emission peak may be attributed to recombination of delocalized electron close to the conduction band with a single charged state of surface oxygen vacancy. TL measurements were carried out on Gd(2)O(3) prepared by different fuels by irradiating with γ-rays (1kGy). A well resolved glow peak at 230°C was observed for all the samples. It is observed that TL intensity is found to be higher in for urea fuel when compared to others. From TL glow curves the kinetic parameters were estimated using Chen's peak shape method and results are discussed in detail.
  Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 05/2012; 96:532-40. · 2.10 Impact Factor
• Article: Ion beam induced amorphization and bond breaking in Zn2SiO4:Eu3+ nanocrystalline phosphor.

  D V Sunitha, H Nagabhushana, Fouran Singh, S C Sharma, N Dhananjaya, B M Nagabhushana, R P S Chakradhar
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  ABSTRACT: This paper reports on the ionoluminescence (IL) of Zn(2)SiO(4):Eu(3+) nanophosphors bombarded with 100 MeV Si(7+) ions with fluences in the range (3.91-21.48)×10(12) ions cm(-2). The prominent IL emission peaks recorded at 580, 590, 612, 650 and 705 nm are attributed to the luminescence centers activated by Eu(3+) ions. It is observed that IL intensity decreases and saturates with increase of Si(7+) ion fluence. Fourier transform infrared (FT-IR) studies confirm surface/bulk amorphization for a fluence of (3.91-21.48)×10(13) ions cm(-2). These results show degradation of SiO (2ν(3)) bonds present on the surface of the sample and/or due to lattice disorder produced by dense electronic excitation under heavy ion irradiation. These results are discussed in detail.
  Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 05/2012; 90:18-21. · 2.10 Impact Factor
• Article: YAlO(3):Cr(3+) nanophosphor: Synthesis, photoluminescence, EPR, dosimetric studies.

  H B Premkumar, D V Sunitha, H Nagabhushana, S C Sharma, B M Nagabhushana, J L Rao, Kinshuk Gupta, R P S Chakradhar
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  ABSTRACT: YAlO(3):Cr(3+) (0.1mol%) nanophosphor has been synthesized by low temperature solution combustion method. The X-ray diffraction studies reveal an orthorhombic structure. Transmission electron microscopy reveals that the particles are spherical in shape with nano-size ∼40-65nm. Electron paramagnetic resonance (EPR) spectrum shows a resonance signal with effective g value at g=1.978 which can be attributed to the exchange coupled Cr(3+) ion pairs in weakly distorted sites. The photoluminescence spectrum shows an intense doublet at 677nm and 694nm (R lines) assigned to spin-forbidden (2)E(g)→(4)A(2)(g) transition of Cr(3+) ions. EPR and PL studies reveal that the Cr(3+) ions occupy Al(3+) sites in YAlO(3). The interesting feature reported in this work concerns the linearity with gamma dose in the wide range (0.1-6kGy). Prominent TL glow peaks at 226°C and 346°C were observed for both γ and UV-rays respectively. It is observed that the peaks at 226°C and 346°C eventually show a linear response up to 5kGy which makes them a candidate for high dose dosimetry of ionizing radiation. The kinetic parameters namely activation energy (E), order of kinetics (b), frequency factor (s) of undoped and Cr doped samples were determined using Chens glow peak shape method and the results are discussed in detail.
  Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 04/2012; 96:154-62. · 2.10 Impact Factor
• Article: Synthesis, characterization, thermo-and photoluminescence properties of Bi 3+ co-doped Gd 2 O 3 :Eu 3+ nanophosphors

  N Dhananjaya, · H Nagabhushana, · B M Nagabhushana, · S C Sharma, · B Rudraswamy, · N Suriyamurthy, · C Shivakumara, · R P S Chakradhar, Prof C N R Rao
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  ABSTRACT: Gd 2 O 3 :Eu 3+ (4 mol%) co-doped with Bi 3+ (Bi = 0, 1, 3, 5, 7, 9 and 11 mol%) ions were synthesized by a low-temperature solution combustion method. The pow-ders were calcined at 800°C and were characterized by pow-der X-ray diffraction (PXRD), transmission electron mi-croscopy (TEM), Fourier transform infrared and UV–Vis spectroscopy. The PXRD profiles confirm that the calcined products were in monoclinic with little cubic phases. The particle sizes were estimated using Scherrer's method and Williamson–Hall plots and are found to be in the ranges 40– 60 nm and 30–80 nm, respectively. The results are in good agreement with TEM results. The photoluminescence spec-tra of the synthesized phosphors excited with 230 nm show emission peaks at ∼590, 612 and 625 nm, which are due to the transitions 5 D 0 → 7 F 0 , 5 D 0 → 7 F 2 and 5 D 0 → 7 F 3 of Eu 3+ , respectively. It is observed that a significant quench-ing of Eu 3+ emission was observed under 230 nm excitation when Bi 3+ was co-doped. On the other hand, upon 350 nm excitation, the luminescent intensity of Eu 3+ ions was en-hanced by incorporation of Bi 3+ (5 mol%) ions. The in-troduction of Bi 3+ ions broadened the excitation band of Eu 3+ of which a new strong band occurred ranging from 320 to 380 nm. This has been attributed to the 6s 2 → 6s6p transition of Bi 3+ ions, implying a very efficient energy transfer from Bi 3+ ions to Eu 3+ ions. The gamma radiation response of Gd 2 O 3 :Eu 3+ exhibited a dosimetrically useful glow peak at 380°C. Using thermoluminescence glow peaks, the trap parameters have been evaluated and discussed. The observed emission characteristics and energy transfer indi-cate that Gd 2 O 3 :Eu 3+ , Bi 3+ phosphors have promising ap-plications in solid-state lighting.
  Applied Physics B 04/2012; 107:503-511. · 2.19 Impact Factor
• Article: Synthesis, characterization, thermo-and photoluminescence properties of Bi 3+ co-doped Gd 2 O 3 :Eu 3+ nanophosphors

  N Dhananjaya, · H Nagabhushana, · B M Nagabhushana, · S C Sharma, · B Rudraswamy, N.Suriyamurthy, C.Shivakumara, R.P.S.Chakradhar
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  ABSTRACT: Gd 2 O 3 :Eu 3+ (4 mol%) co-doped with Bi 3+ (Bi = 0, 1, 3, 5, 7, 9 and 11 mol%) ions were synthesized by a low-temperature solution combustion method. The pow-ders were calcined at 800°C and were characterized by pow-der X-ray diffraction (PXRD), transmission electron mi-croscopy (TEM), Fourier transform infrared and UV–Vis spectroscopy. The PXRD profiles confirm that the calcined products were in monoclinic with little cubic phases. The particle sizes were estimated using Scherrer's method and Williamson–Hall plots and are found to be in the ranges 40– 60 nm and 30–80 nm, respectively. The results are in good agreement with TEM results. The photoluminescence spec-tra of the synthesized phosphors excited with 230 nm show emission peaks at ∼590, 612 and 625 nm, which are due to the transitions 5 D 0 → 7 F 0 , 5 D 0 → 7 F 2 and 5 D 0 → 7 F 3 of Eu 3+ , respectively. It is observed that a significant quench-ing of Eu 3+ emission was observed under 230 nm excitation when Bi 3+ was co-doped. On the other hand, upon 350 nm excitation, the luminescent intensity of Eu 3+ ions was en-hanced by incorporation of Bi 3+ (5 mol%) ions. The in-troduction of Bi 3+ ions broadened the excitation band of Eu 3+ of which a new strong band occurred ranging from 320 to 380 nm. This has been attributed to the 6s 2 → 6s6p transition of Bi 3+ ions, implying a very efficient energy transfer from Bi 3+ ions to Eu 3+ ions. The gamma radiation response of Gd 2 O 3 :Eu 3+ exhibited a dosimetrically useful glow peak at 380°C. Using thermoluminescence glow peaks, the trap parameters have been evaluated and discussed. The observed emission characteristics and energy transfer indi-cate that Gd 2 O 3 :Eu 3+ , Bi 3+ phosphors have promising ap-plications in solid-state lighting.
  Applied Physics B 04/2012; 107:503-511. · 2.19 Impact Factor
• Article: Structural, EPR, optical and Raman studies of Nd2O3:Cu2+ nanophosphors.

  B Umesh, B Eraiah, H Nagabhushana, S C Sharma, B M Nagabhushana, C Shivakumara, J L Rao, R P S Chakradhar
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  ABSTRACT: Nanocrystalline Nd(2)O(3):Cu(2+) (2mol %) phosphors have been prepared by a low temperature solution combustion technique. Powder X-ray diffraction (PXRD) results confirm that hexagonal A-type Nd(2)O(3) (900°C, 3h) and the lattice parameters have been evaluated by Rietveld refinement. Surface morphology of as-formed and Cu(2+) doped Nd(2)O(3) phosphors show that the particles are irregular in shape and porous in nature. TEM results also confirm the nature and size of the particles. The EPR spectrum exhibits two resonance signals with effective g values at g(ǀǀ)≈2.12 and g(⊥)≈2.04. The g values indicate that the site symmetry of Cu(2+) ions is octahedral symmetry with elongated tetragonal distortion. Raman studies show major peaks, which are assigned, to F(g) and combination of A(g)+E(g) modes. It is observed that the Raman peaks and intensity have been reduced in Cu(2+) doped samples. UV-Visible absorption spectra exhibit a strong and broad absorption band at ∼240nm. Further, the absorption peak shifts to ∼14nm in Cu(2+) doped samples. The optical band gap is estimated to be 5.28eV for Cu doped Nd(2)O(3) nanoparticles which are higher than the bulk Nd(2)O(3) (4.7eV). This can be attributed to the quantum confinement effect of the nanoparticles.
  Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 03/2012; 94:365-71. · 2.10 Impact Factor
• Article: Swift heavy ion induced structural, iono and photoluminescence properties of β-CaSiO₃:Dy³⁺ nanophosphor.

  D V Sunitha, H Nagabhushana, Fouran Singh, N Dhananjaya, S C Sharma, B M Nagabhushana, C Shivakumara, R P S Chakradhar
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  ABSTRACT: CaSiO(3):Dy(3+) (1-5 mol%) nanophosphors have been prepared by a low temperature solution combustion method. The structural and luminescence (ionoluminescence; IL and photoluminescence; PL) studies have been carried out for pristine and ion irradiated samples. The XRD patterns of pristine sample show a prominent peak at (320) for the monoclinic structure of β-CaSiO(3). Upon ion irradiation, the intensity of the prominent peak is decreased at the fluence of 7.81 × 10(12)ions cm(-2) and at higher fluence of 15.62 × 10(12)ions cm(-2), the prominent peak completely vanishes. The decrease in peak intensity might be due to the stress induced point defects. On-line IL and in situ PL studies have been carried out on pelletized samples bombarded with 100 MeV Si(7+) ions with fluences in the range (7.81-15.62)×10(12)ions cm(-2). The characteristic emission peaks at 481,574, 664 and 754 nm recorded in both IL and PL are attributed to the luminescence centers activated by Dy(3+) ions. It is found that IL and PL emissions intensity decreases with increase in Si(7+) ion fluence. The decrease in intensity can be due to the destruction of Si-O-Si and O-Si-O type species present on the surface of the sample. FTIR studies also confirm the Si-O-Si and O-Si-O type species observed to be sensitive for swift heavy ion (SHI) irradiated samples.
  Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 03/2012; 93:300-5. · 2.10 Impact Factor
• Article: Combustion synthesis, structural characterization, thermo and photoluminescence studies of CdSiO₃:Dy³⁺ nanophosphor.

  C Manjunatha, D V Sunitha, H Nagabhushana, B M Nagabhushana, S C Sharma, R P S Chakradhar
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  ABSTRACT: CdSiO(3):Dy(3+) (1-9mol%) nanophosphors were prepared for the first time using the solution combustion method. The process of monoclinic phase formation was investigated by PXRD, TG-DTA and FTIR. The results show that the phase formation temperature of combustion-derived monoclinic CdSiO(3) is found to be lower as compared to the powders prepared by solid-state and sol-gel methods. It was observed that the average crystallite size calculated by Debye-Scherrer's formula and Williamson-Hall (W-H) plot are well comparable and was found to be in the range of 35-70 nm. Scanning electron micrographs indicate that there exist circular microcrystalline particles. It is observed that the optical energy gap is widened with the increase of Dy(3+) ion dopant. The photoluminescence (PL) spectra exhibit characteristic transitions of Dy(3+) due to (4)F(9/2)→(6)H(15/2) (blue) and (4)F(9/2)→(6)H(13/2) (yellow) regions. The thermoluminescence (TL) glow curve of CdSiO(3):Dy(3+) nano powder exposed to UV irradiation exhibited one main peak centered at 170°C. The intensity of the main peak increases up to the dose of 20 min then it decreases. The glow curves were analyzed by the glow peak shape method and the estimated trap parameters are discussed.
  Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 03/2012; 93:140-8. · 2.10 Impact Factor
• Article: Thermoluminescence and EPR studies of nanocrystalline Nd₂O₃:Ni²⁺ phosphor.

  B Umesh, B Eraiah, H Nagabhushana, S C Sharma, D V Sunitha, B M Nagabhushana, C Shivakumara, J L Rao, R P S Chakradhar
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  ABSTRACT: Nanocrystalline Nd(2)O(3):Ni(2+) (2 mol%) phosphor has been prepared by a low temperature (∼400°C) solution combustion method, in a very short time (<5 min). Powder X-ray diffraction results confirm the single hexagonal phase of nanopowders. Scanning electron micrographs show that nanophosphor has porous nature and the particles are agglomerated. Transmission electron microscopy confirms the nanosize (20-25 nm) of the crystallites. The electron paramagnetic resonance (EPR) spectrum exhibits a symmetric absorption at g≈2.77 which suggests that the site symmetry around Ni(2+) ions is predominantly octahedral. The number of spins participating in resonance (N) and the paramagnetic susceptibility (χ) has been evaluated. Raman study show major peaks, which are assigned to F(g) and combination of A(g)+E(g) modes. Thermoluminescence (TL) studies reveal well resolved glow peaks at 169°C along with shoulder peak at around 236°C. The activation energy (E in eV), order of kinetics (b) and frequency factor (s) were estimated using glow peak shape method. It is observed that the glow peak intensity at 169°C increases linearly with γ-dose which suggest that Nd(2)O(3):Ni(2+) is suitable for radiation dosimetry applications.
  Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 03/2012; 93:228-34. · 2.10 Impact Factor
• Article: Ionoluminescence studies of natural kyanite mineral from different parts of Indian origin.

  H Nagabhushana, Fouran Singh, S C Sharma, B M Nagabhushana, R P S Chakradhar
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  ABSTRACT: Ionoluminescence (IL) studies of two natural kyanite (Al(2)SiO(5)) minerals collected from different regions of India was carried out using 120 MeV Ag(9+) ions in the fluence range of 1.50-10.5 × 10(11)ions/cm(2). Identical emission peaks were observed in both the samples at ~416, 463, 530-540 nm along with other emission peaks at ~689 nm, 706 nm (sharp) and 770 nm (broad). The sharp emission peaks at 689 nm correspond to R lines of Cr(3+) impurities and are related to transition of (2)E(g)→(4)A(2g). The sharp and broad emission peaks in the range of 706-770 nm are attributed to Fe(3+) impurities and are related to the transition of (4)T(1g)→(6)A(1g). The peak in the range of 530-540 nm is attributed to Mn(2+) impurities and is related to the transition of (4)T(1)→(6)A(1). IL peak intensity decreases with the Ag(9+) ion fluence which might be due to the thermal quenching/amorphization, caused by the ion beam irradiation. The amorphization in the sample was explained with the help of thermal spike model (TSM). These results demonstrated that IL is a very sensitive technique for impurity characterization and differentiating the origin of minerals.
  Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 08/2011; 86:15-9. · 2.10 Impact Factor