Dr. C Pandurangappa
@rnsit.ac.in
Associate Professor and Head of Physics
R N S Institute of Technology, Bengaluru
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
K. Nagendra, C. Pandurangappa, K.R. Sardar Pasha, N. Hanumantharaju, Karanam Madhavi, and V.C. Veeranna Gowda
Elsevier BV
H. J. Rajendra and C. Pandurangappa
Springer Science and Business Media LLC
Yashaswini, S. Pratibha, C. Pandurangappa, and G. Nagaraju
Springer Science and Business Media LLC
G. N. Venkata Reddy, C. Pandurangappa, V. J. Angadi, and L. P. Babu Reddy
Allerton Press
Abstract Er-doped calcium fluoride (CaF 2 ) nanoparticles were synthesized by co-precipitation method and characterized by PXRD, SEM, FTIR, and, after γ-irradiation, by optical absorption/photoluminescence spectra. Color centers responsible for optical absorption in γ-irradiated samples were identified. Photoluminescence spectrum of γ-rayed samples exhibited the emission bands peaked at 387, 442, 460, and 517 nm. The nature of radiation-induced optical absorption and photoluminescence was discussed in detail.
Yashaswini, C. Pandurangappa, and S. Pratibha
Elsevier BV
Abstract Herein we report the structural, morphological, photoluminescence (PL) and thermoluminescence (TL) properties of Li co-doped CaSO4:Ce3+ nanophosphors prepared successfully via co-precipitation method. The PXRD pattern confirmed the single-phase hexagonal structure with space group P3121(1 5 2) with JCPDS Card no. 76–02312. The average crystallite size was estimated by Scherrer’s and W-H methods are found to be in the range 40–90 nm. These results are well agreed with the TEM results. The SEM micrographs reveal a wire-like structure with an average size ranging from 80 to 110 nm. Under 293 nm excitation, the effective blue emission positioned at 305 and 328 nm which are characteristic of 5d → 4f (2F5/2 and 2F7/2) of Ce3+ ions. PL emission intensity is increased with an increase in Li+ ion concentration and reached a maximum of 5 mol% and then started decreasing. The results show that the addition of Li+ ions in CaSO4:Ce3+ lattice could induce a significant improvement of their PL intensity. The chromaticity coordinates and correlated color temperature of all the phosphors were studied and found to be located in the blue region. The TL response of the prepared nanophosphors to 10 Gy-5 KGy doses is studied and their kinetic parameters were discussed in detail. These outcomes specify that these phosphors are favorable material for luminescence centered optoelectronic devices.
Yashaswini, S. Pratibha, R. Lokesh, N. Dhananjaya, and C. Pandurangappa
Elsevier BV
Abstract Sucrose mediated LaAlO3: Ce3+ nanopowders were prepared by propellant chemistry technique. The preliminary characterizations were carried out using Powder X-Ray Diffraction (PXRD), Fourier Transform InfraRed spectra (FTIR), Scanning Electron Microscopy (SEM) and transmission electron microscopy (TEM) to analyse the structure and morphology of the prepared nanophosphors. PXRD studies showed pure rhombohedral single phase with average crystallite size of the order of 45-62 nm. SEM micrographs confirmed nanoparticles formation and the crystallite size agrees well with the TEM image. The optical band gap of LaAlO3: Ce3+ (1-2 mol%) nanophosphors was found to be in the range 4.5-4.93 eV. PL spectra showed broad intense band at 449 nm and 541 nm up on 330 nm excitation. Chromaticity studies exhibit the blue green color emission of the prepared phosphors. The intensity and color of Ce3+ doped LaAlO3 nanophosphors confirm that these phosphors can be a potential material for display and optical devices.
P Ravindra, C Pandurangappa, and M Sankar
IOP Publishing
K. Ashwini, C. Pandurangappa, K. Avinash, S. Srinivasan, and E. Stefanakos
Elsevier BV
Abstract Nanoparticles of zinc sulfide doped with samarium ions of different molar concentrations from 1 to 5 mol% were synthesized by co-precipitation method. Various metrological tools were used to characterize the as-synthesized nanoparticles for their structural, nanostructural, chemical, optical and photoluminescence characteristics. The results of powder x-ray diffraction pattern and high-resolution transmission electron microscopic images revealed the presence of samarium inside the zinc sulfide nanoparticles, with particle size between 3 and 7 nm. The purity of the ZnS:Sm nanoparticles were obtained from Fourier transform infrared spectral profiles. Large agglomeration of fine particles was shown by the scanning electron microscope images. The UV–Vis diffuse reflectance spectroscopy was used to study the optical absorption properties of the as-prepared ZnS:Sm sample. Photoluminescence studies of samarium doped zinc sulfide nanoparticles showed two major emission peaks when excited at 365 nm, one in the orange region (603 nm) and the other one in the red region (701 nm) due to f-f transitions of the Sm3+ in the 4f5configuration.
H.J. Rajendra and C. Pandurangappa
Wiley
Cerium (Ce3+ )-doped (1, 3, and 7 mol%) yttrium vanadate phosphors were prepared using a co-precipitation technique. The structural and optical properties of the synthesized samples were studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), optical absorption, and photoluminescence (PL) spectroscopy techniques. The tetragonal structure and the formation of the nanosized crystallites in the YVO4 :Ce phosphor were confirmed using XRD analysis. HR-TEM morphology showed rod-like nanoparticles of different sizes. Optical absorption spectra demonstrated strong absorption bands at 268 and 276 nm. PL spectra showed strong peaks at 546, 574, and 691 nm following excitation at 300 nm. The calculated CIE chromaticity coordinates demonstrated that YVO4 :Ce could be used as a novel phosphor for the development of light-emitting diode lamps.
H. J. Rajendra and C. Pandurangappa
Springer Science and Business Media LLC
The phosphor YVO4:5 mol%Dy, Eu+3 (1, 3, 5 and 7 mol%) is synthesized through co-precipitation technique. The as prepared samples are characterized by powder X-ray diffraction (PXRD), Fourier change infrared red Spectroscopy (FTIR), Electron Scanning microscopy (SEM),UV absorption, Photoluminescence (PL) techniques and Study of CIE color property. The PXRD confirmed that the prepared sample has tetragonal structure. The Crystallite size was calculated using PXRD data and it is found to in the range of 7–17 nm. SEM pictures indicate that YVO4:5%Dy, Eu+3 nanocrystals are agglomerated. FTIR spectrum shows strong absorption stretching frequency peak at 805 cm−1. The PL emission spectrum showed prominent emission peaks at 481, 575, 618 and 699 nm. The calculated CIE coordinates and Correlated color temperature (CCT) indicates that this phosphor may be used for the development of LED lamps.
Yashaswini, C Pandurangappa, and N Dhananjaya
IOP Publishing
Yashaswini, C. Pandurangappa, and N. Dhananjaya
Springer Science and Business Media LLC
Abstract.The CaSO4:Ce3+ (1-9mol%) nanorods were successfully synthesized by co-precipitation method. Preliminary crystallographic, structural and optical studies of the prepared nanorods were done using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), Fourier transform infrared spectroscopy (FTIR), UV-visible absorption spectroscopy, photoluminescence (PL) and thermoluminescence (TL). The CaSO4:Ce3+ has a single phase hexagonal lattice structure with space group P3121(152). The average crystallite size was calculated using Scherrer’s formula and found to be in the range 41-62 nm which is in good agreement with TEM results. The SEM micrographs shows rod like structure with various sizes. Upon 350 nm excitation, the CaSO4:Ce3+ nanophosphor showed emission at 390, 405 and 430 nm, which is characteristic luminescence of $5{\\rm d} \\rightarrow 4{\\rm f}$5d→4f(2F5/2, 2F7/2) transitions of the Ce3+ ions. The chromaticity co-ordinates and correlated color temperature of all the phosphors were well located in blue region. TL glow curve response of the prepared nanorods with 500 Gy $\\gamma$γ-irradiated was studied. TL glow curve contains glow peak at 188 °C. Kinetic parameters was estimated for deconvoluted TL glow peaks and studied in detail.
H.J. Rajendra, C. Pandurangappa, and D.L. Monika
Elsevier BV
Abstract Trivalent dysprosium (Dy3+) activated nanocrystalline yttrium vanadate (YVO4) phosphor was synthesized via co-precipitation method. The prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), optical absorption and photoluminescence (PL) techniques. The XRD patterns reveal the tetragonal crystalline phase. SEM images reveal that Dy doped YVO4 nanocrystals are agglomerated. EDAX confirms the formation of YVO4:Dy. FTIR spectrum shows two strong absorption bands at 459 and 761 cm−1. Optical absorption spectrum showed the surface defects in the as-prepared samples. The PL emission spectrum shows two characteristic emission bands at 485 and 575 nm. The strong yellow emission peak at 575 nm is assigned to 4F9/2 → 6H13/2 hyper sensitive transition of Dy3+ ions. Study of CIE chromaticity diagram indicates the suitability of the phosphor for the development of yellow-green LEDs.
C Bhaskar, L Lakshminarayanachari, and C Pandurangappa
American Scientific Publishers
K Ravindranath, K Lakshminarayanachari, and C Pandurangappa
American Scientific Publishers
P. V Nirmaladevi, K Lakshminarayanachari, and C Pandurangappa
American Scientific Publishers
Dankan V Gowda, D V Kishore, Shivashankar, A C Ramachandra, and C Pandurangappa
IEEE
Motor cycles are the common mode of transport of the middle class India. When the rider driving on the bumping road circumstances rider has to face problems results in exposure to whole body vibration. Motorcycle pitch is produced due to a sudden acceleration/sudden deceleration or whenever the vehicle hits the pot hole/bump. The goal of this research was to design of motorcycle suspension system and optimize the pitch using nonlinear controller, modeling and simulation is carried out using MATLAB and the results are compared with existing work. To give the prominent to improve the ride eminence and increase in comfort due to substantially reduced the amplitude of disturbances by presenting nonlinear controllers to decrease the effect of travelling over rough ground.
K. Ashwini, C. Pandurangappa, and K. Avinash
Elsevier BV
Abstract Solvothermal and co-precipitation method were adopted in synthesizing Pure Zinc Sulphide nanoparticles (ZnSnp’s). The PXRD data revealed that the synthesized ZnSnp’s was in wurtzite structure. Application of Debye-Scherer formula to XRD showed the particle size to be 23nm and 4-7nm for solvothermal and co-precipitation method respectively; this was in conformity with Transmission electron microscopy images. The morphological study of these nanoparticles by SEM images showed that they were agglomerated, crispy and porous. Absence of impurities was identified by FTIR measurements. The UV–Visible data showed that the synthesized nanoparticles are blue shifted when compared with bulk phase of ZnS due to its quantum confinement effect. The ZnSnp’s prepared via co-precipitation method showed enhanced PL emission intensity compared to that synthesized via solvothermal method
N.A. Yashaswini, C. Pandurangappa, N. Dhananjaya, and M.V. Murugendrappa
Inderscience Publishers
CaSO4 nanoparticles have been synthesised by co-precipitation technique. Powder X-ray diffraction (PXRD) studies reveal that the as formed product is in hexagonal phase. The scanning electron microscopy (SEM) results reveal a nano wire and belt like morphology, and energy dispersive spectroscopy (EDS) confirmed the presence of elements in the sample. Fourier transform infrared (FTIR) spectroscopy shows a strong doublet at 658 cm-1 and 600 cm-1 owing to ν4(SO2-4) bending vibrations. The band at 3798 cm-1 and 3548 cm-1 corresponds to -OH group, 2926 cm-1 corresponds to C-H stretching bands, band centred at 1629 cm-1 is associated with crystal H2O molecule on CaSO4 and 1149 cm-1 corresponds to SO2-4 stretching vibrations. The Raman spectrum exhibits an intense peak at 1010 cm-1 associated with the SO2-4 mode. Photoluminescence (PL) spectrum of the sample showed a prominent green emission band at 545 nm under the 276 nm excitation. The dielectric spectroscopic and AC conductivity have been studied in the range 100 Hz to 1 MHz in detail.
K. Ashwini, Yashaswini, and C. Pandurangappa
Elsevier BV
Abstract Europium doped zinc sulfide nanocrystals (ZnS:Eu) are prepared by solvothermal method. Crystallite size and lattice constant of the prepared samples are calculated from the X-ray diffraction patterns. The as-prepared samples are found to be a mixture of complex chemical groups. Heat treatment of the samples at 300 °C resulted in ZnS:Eu state. The crystal structure is not affected by the increase in the concentration of Eu from 1 mol% to 5 mol%. Fourier Transform Infrared Spectroscopy (FTIR) studies showed that characteristic absorption bands of hydroxyl groups and the acetate bands increased with increase in Eu concentration. The morphological results studied using Scanning Electron Microscopy (SEM) indicate agglomeration of nanoparticles and a marginal increase in the particle size. Photoluminescence (PL) spectra of the samples showed a prominent emission band peaked at ∼400 nm besides three weak ones at ∼422, 485 and 530 nm. The PL intensity increased with increase in Eu concentration.
C. Pandurangappa and B.N. Lakshminarasappa
Elsevier BV
Optical absorption spectra of gamma irradiated (γ-rayed) Strontium (Sr) doped Calcium fluoride (CaF2) single crystals showed a prominent absorption peak at ∼370 nm and two weak ones at ∼463 and 524 nm. At higher γ-dose the two weak peaks merged into a broad one at ∼520 nm. The Photoluminescence (PL) spectra showed a prominent emission at ∼394 nm when the crystals were excited at ∼240 nm. The excitation of samples at 370 nm showed strong emission at ∼530 nm with a shoulder at ∼465 nm. The optical absorption and PL intensities were found to increase with γ-dose. However, the optical absorption and PL intensities of CaF2:Sr are found to be less than those of undoped CaF2 single crystals.