http://13.232.72.61:8080/jspui/handle/123456789/1900 2026-04-04T00:23:57Z 2026-04-04T00:23:57Z Basavaraj, R. B. Malleshappa, J. Darshan, G. P. Prasad, B. Daruka Nagabhushana, H. http://13.232.72.61:8080/jspui/handle/123456789/2260 2019-05-18T09:23:10Z 2017-01-01T00:00:00Z

Title: Cationic Surfactant Assisted Sonochemical Synthesis of Nd3+ Doped Zn2SiO4 Nanostructures for Solid State Lighting Applications Authors: Basavaraj, R. B.; Malleshappa, J.; Darshan, G. P.; Prasad, B. Daruka; Nagabhushana, H. Abstract: .For the first time cationic surfactant assisted ultrasound synthesis route has been used for the preparation of pure and Nd3+ (0.5-9 mol %) doped Zn2SiO4 nanophosphors. The shape, size and morphology of the products were tuned by controlling the various experimental parameters. The final product was well characterized by sophisticated techniques viz. powder X-ray diffraction (PXRD), Ultraviolet visible spectroscopy (UV-Vis) and photoluminescence (PL). The powder X-ray diffraction patterns confirmed that the synthesized samples exhibit hexagonal phase without any impurity. The DRS spectra showed major peaks at 275, 360, 529, 586, 680, 742 and 806 nm due to the transitions of the 4f electrons of Nd3+ from the ground-state 4 I9/2 to 2 F5/2, 4 D3/2 + 4 D5/2 + 2 I11/2, 2 K13/2 + 4 G7/2 + 4 G9/2, 4 G5/2 + 2 G7/2, 4 F7/2 + 4 S3/2, 4 F5/2 + 2 H9/2 and 4 F3/2 respectively. The band energy gap (Eg) of the samples were estimated and found to be in the range 5.32 – 5.52 eV. Under 421 nm excitation, PL spectra exhibit strong near ultraviolet emission peaks at ~ 444 nm, 459 nm and 520 nm were attributed to 2 P3/2→ 4 I13/2, 2 P3/2→4 I15/2, 1 I6→3 H4, 2 P1/2→4 I9/2 and 4 G7/2→4 I9/2 transitions respectively. The photometric studies indicate that the synthesized Zn2SiO4: Nd3+ nanophosphors can be tuned from blue to pale green by varying the dopant concentration. The current synthesis route is rapid, environmentally benign, cost-effective and useful for industrial applications such as solid state lighting and display devices.

2017-01-01T00:00:00Z Suresh, C. Nagabhushana, H. Darshan, G. P. Basavaraj, R. B. Sharma, S. C. Sunitha, D. V. Prasad, B. Daruka http://13.232.72.61:8080/jspui/handle/123456789/2248 2019-05-18T07:17:44Z 2017-01-01T00:00:00Z

Title: Positron Annihilation Spectroscopy and Photoluminescence Investigation Of Laof:Tb3+ Nanophosphor Fabricated Via Ultrasound Assisted Sonochemical Route Authors: Suresh, C.; Nagabhushana, H.; Darshan, G. P.; Basavaraj, R. B.; Sharma, S. C.; Sunitha, D. V.; Prasad, B. Daruka Abstract: LaOF:Tb3+ nanophosphors were synthesized by modified sonochemical route using extracted Epigallocatechin gallate (EGCG) from green tea powder as surfactant. Powder X-ray diffraction patterns confirm the tetragonal phase of samples. Morphology of the products was tuned by changing the influential experimental parameters. Positron annihilation spectroscopy (PAS) was used to investigate the defect chemistry of the prepared samples. PAS specified the presence of defects at crystallite boundaries, vacancy clusters and large voids in the prepared compounds. Photoluminescence emission spectra consists of characteristic green emissions owing to 5 D4 ? 7 FJ (J = 6, 5, 4, 3) transitions of Tb3+ ions. The estimated critical distance between dopant ions was found to be 16.60 Å is majorly responsible for the dipole-dipole interaction and concentration quenching. The photometric study such as Commission Internationale de L’Eclairage, Correlated Color Temperature and Color purity indicates that the obtained phosphors could be a promising green component for optoelectronic applications in particular to white LEDs

2017-01-01T00:00:00Z Suresh, C. Nagabhushana, H. Darshan, G. P. Sharma, S. C. Sunitha, D. V. Daruka Prasad, B. http://13.232.72.61:8080/jspui/handle/123456789/2129 2019-04-29T06:30:30Z 2017-01-01T00:00:00Z

Title: Positron annihilation spectroscopy and photoluminescence investigation of LaOF:Tb3+ nanophosphor fabricated via ultrasound assisted sonochemical route Authors: Suresh, C.; Nagabhushana, H.; Darshan, G. P.; Sharma, S. C.; Sunitha, D. V.; Daruka Prasad, B. Abstract: LaOF:Tb3+ nanophosphors were synthesized by modified sonochemical route using extracted Epigallocatechin gallate (EGCG) from green tea powder as surfactant. Powder X-ray diffraction patterns confirm the tetragonal phase of samples. Morphology of the products was tuned by changing the influential experimental parameters. Positron annihilation spectroscopy (PAS) was used to investigate the defect chemistry of the prepared samples. PAS specified the presence of defects at crystallite boundaries, vacancy clusters and large voids in the prepared compounds. Photoluminescence emission spectra consists of characteristic green emissions owing to 5 D4 ? 7 FJ (J = 6, 5, 4, 3) transitions of Tb3+ ions. The estimated critical distance between dopant ions was found to be 16.60 Å is majorly responsible for the dipole-dipole interaction and concentration quenching. The photometric study such as Commission Internationale de L’Eclairage, Correlated Color Temperature and Color purity indicates that the obtained phosphors could be a promising green component for optoelectronic applications in particular to white LEDs.

2017-01-01T00:00:00Z Venkataravanappaa, M. Nagabhushana, H. Darshan, G. P. Sharma, S. C. Archana, K. V. Basavaraj, R. B. Daruka Prasad, B. http://13.232.72.61:8080/jspui/handle/123456789/2060 2019-04-13T08:34:39Z 2018-01-01T00:00:00Z

Title: Facile ultrasound route for the fabrication of green emitting Ba2SiO4: Eu2+ nanophosphors for display and dosimetric applications Authors: Venkataravanappaa, M.; Nagabhushana, H.; Darshan, G. P.; Sharma, S. C.; Archana, K. V.; Basavaraj, R. B.; Daruka Prasad, B. Abstract: A series of Eu2+ (1–5 mol%) activated Ba2SiO4 nanophosphors were prepared by ecofriendly ultrasound assisted sonochemical route using Epigallocatechin gallate (EGCG) extract as bio-surfactant. The obtained nanophosphors were well characterized by Powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) etc. The average crystallite size was estimated using Debye–Scherer's formula and Williamson–Hall (W–H) plots and were found to be in the range 20–32 nm. The photoluminescence excitation spectrum exhibited two broad bands around 330 and 370 nm ascribed to the transitions of Eu2+ from 4f-ground state to 5d-excited state. The emission spectra showed broad band around 505 nm wavelength ascribed to 5d ! 4f allowed transition of Eu2+ ions. Thermoluminescence (TL) of Eu2+ doped Ba2SiO4 nanophosphors were investigated using g-irradiation in the dose range1–6 kGy at a warming rate of 5 C min 1. The phosphors show a well resolved single glow peak at 175 C. The TL intensity of 155 C glow peak increase linearly with g-dose and room temperature fading was 76% which was highly useful in radiation dosimetry. The kinetic parameters (E, s) were estimated and the results were discussed. The chromaticity co-ordinates of all the prepared phosphors were located in green region, as a result Eu2+ activated Ba2SiO4 was a promising single phased phosphor for WLEDs.

2018-01-01T00:00:00Z