35 results on '"Sharma, S."'
Search Results
2. Photometric Investigation of Eu3+ Doped BaGd2O4 Phosphor for Solid-State Lighting Devices
- Author
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Manisha, Sharma, S. K., Chaari, Fakher, Series Editor, Gherardini, Francesco, Series Editor, Ivanov, Vitalii, Series Editor, Haddar, Mohamed, Series Editor, Cavas-Martínez, Francisco, Editorial Board Member, di Mare, Francesca, Editorial Board Member, Kwon, Young W., Editorial Board Member, Trojanowska, Justyna, Editorial Board Member, Xu, Jinyang, Editorial Board Member, Mukherjee, Rabibrata, editor, Janiak, Christoph, editor, Khan, Ziyauddin, editor, Chatterjee, Somak, editor, Roy, Banasri, editor, Ghosh, Sarbani, editor, and Etika, Krishna, editor
- Published
- 2023
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3. Probing the luminescence behavior of Dy3+/Eu3+ co-doped gadolinium molybdate phosphors under the impact of swift heavy ions.
- Author
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Dutta, Somrita, Som, Sudipta, Meena, Mohan Lal, and Sharma, S. K.
- Subjects
PHOTOLUMINESCENCE ,HEAVY ions ,LUMINESCENCE ,LINEAR energy transfer ,PHOSPHORS ,DOPING agents (Chemistry) ,IRRADIATION ,SILVER clusters - Abstract
This study delves into the impact of lithium (Li
3+ ) and silver (Ag7+ ) ion irradiation on the structure and luminescence of Dy3+ doped and Dy3+ /Eu3+ co-doped Gd2 MoO6 phosphors, synthesized via the hydrothermal method. To explore the influence of ions with varied mass and energy, 30 MeV Li3+ and 100 MeV Ag7+ ions were employed at different fluences. We elucidate the induced effects based on defect formation and the role of these ions' linear energy transfer (LET) within the irradiated material. SRIM software estimates the depth profile of the ions. Irradiation of the Gd2 MoO6 phosphors with Li3+ and Ag7+ ions resulted in the formation of disordered lattices or tracks, modifying their structural, optical, and luminescence properties, which were analyzed by various techniques, including X-ray diffraction, scanning electron microscopy, diffuse reflectance, and photoluminescence. Thermoluminescence (TL) tests and calculations of trapping parameters were conducted to evaluate the dosimetric potential. The findings reveal a more pronounced effect of silver ions compared to lithium ions on the structural and luminescence behavior of doped and codoped Gd2 MoO6 phosphors due to their higher atomic weight. [ABSTRACT FROM AUTHOR]- Published
- 2024
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4. Fabricated CeO2 nanopowders as a novel sensing platform for advanced forensic, electrochemical and photocatalytic applications
- Author
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Rohini, B. S., Nagabhushana, H., Darshan, G. P., Basavaraj, R. B., Sharma, S. C., and Sudarmani, R.
- Published
- 2017
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5. Calculation of Spectral Parameters for Doped/Codoped MWO4 (M = Ba2+/Ca2+) Phosphors
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Ambast, A. K. and Sharma, S. K.
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- 2017
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6. Unclonable fluorescence of MgO‐ZrO2:Tb3+ nanocomposite for versatile applications in data security, dermatoglyphics.
- Author
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Swathi, B. N., Krushna, B. R. Radha, Daruka Prasad, B., Sharma, S. C., Subramanian, Balanehru, and Nagabhushana, H.
- Abstract
Latent fingerprints (LFPs) are one among the most important types of evidences at crime scenes because of the distinctiveness and tenacity of the friction ridges in fingerprints (FPs). Therefore, it is essential in forensic science to develop a reliable method to detect LFPs. Traditional detection methods still face a number of difficulties, such as limited sensitivity, low contrast, strong background, and complex processing stages. In this study, MgO‐ZrO2:Tb3+ (1–5 mol%) (MZ:Tb) nanocomposites (NCs) were prepared via a simple solution combustion (SC) method at low temperature. The photoluminescence (PL) investigation demonstrates that when excited at 379 nm, the produced NCs emits distinctive emission peaks of terbium ions (Tb3+). According to the photometric results, the NCs can be employed as warm light NCs and emit light in the green portion of the colour spectrum. The estimated optical band gap from diffuse reflectance spectra is found to be in the range 4.84–4.97 eV. Regardless of the type of surface being used, the optimized MgO‐ZrO2:Tb3+ (4 mol%) (MZ:4Tb) NCs has a strong ability to minimize background fluorescence interference. With high contrast LFP and I–V type of cheiloscopy, these NCs present a flexible fluorescent mark for the identification of levels 1–3 details in forensic investigation. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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- View/download PDF
7. One material, many possibilities via enrichment of luminescence in La2Zr2O7:Tb3+ nanophosphors for forensic stimuli aided applications.
- Author
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Lavanya, D. R., Darshan, G. P., Malleshappa, J., Premkumar, H. B., Sharma, S. C., Hariprasad, S. A., and Nagabhushana, H.
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TERBIUM ,LUMINESCENCE ,FORENSIC fingerprinting ,SCREEN process printing ,MOLECULAR spectra ,PHOTOLUMINESCENCE - Abstract
Engineering a single material with multidirectional applications is crucial for improving productivity, low cost, flexibility, least power consumption, etc. To achieve these requirements, novel design structures and high-performance materials are in urgent need. Lanthanide-doped nanophosphors have the greatest strengths and ability in order to tune their applications in various dimensions. However, applications of nanophosphor in latent fingerprints visualization, anti-counterfeiting, and luminescent gels/films are still in their infancy. This study demonstrated a simple strategy to enhance the luminescence of Tb
3+ (1–11 mol %) doped La2 Zr2 O7 nanophosphors by conjugating various fluxes via a simple solution combustion route. The photoluminescence emission spectra reveal intense peaks at ~ 491, 546, 587, and 622 nm, which arises from5 D4 →7 FJ (J = 6, 5, 4, 3) transitions of Tb3+ ions, respectively. The highest emission intensity was achieved in the NH4 Cl flux assisted nanophosphor as compared to NaBr and NH4 F assisted samples. The colorimetric images of fingerprints visualized using the optimized nanophosphor on forensic related surfaces exhibit level –III ridge details, including sweat pores, the width of the ridges, bifurcation angle, and the successive distance between sweat pores, etc. These results are decisive parameters that clearly support the statement "no two persons have ever been found to have the same fingerprints". The anti-counterfeiting security ink was formulated using optimized nanophosphor and various patterns were designed by simple screen printing and dip pen technologies. The encoded information was decrypted only under ultraviolet 254 nm light. All the designed patterns are exhibit not just what it looks/feel like and how better it works. As a synergetic contribution of enhanced luminescence of the prepared nanophosphor, the green-emissive films were fabricated, which display excellent flexibility, uniformity, and transparency in the normal and ultraviolet 254 nm light illumination. The aforementioned results revealed that the prepared NH4 Cl flux-assisted La2 Zr2 O7 : Tb3+ (7 mol %) NPs are considered to be the best candidate for multi-dimensional applications. [ABSTRACT FROM AUTHOR]- Published
- 2022
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8. Influences of Doping and Annealing on the Structural and Photoluminescence Properties of Y2O3 Nanophosphors
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Som, S., Sharma, S. K., and Shripathi, T
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- 2013
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9. Effects of Gamma Irradiation on Erbium Indiffused Lithium Niobate Substrate
- Author
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Ganguly, P., Biswas, J. C., Lahiri, S. K., Nandagoshami, M. L., Kumar, G. A., and Sharma, S. L.
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- 2005
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10. Extending the temperature sensing range using Eu3+ luminescence up to 865 K in a single crystal of EuPO4
- Author
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Sharma, S., Köhler, T., Beyer, J., Fuchs, M., Gloaguen, R., and Heitmann, J.
- Subjects
Eu3+ doping ,photoluminescence ,temperature sensing ,relative sensitivity - Abstract
The temperature evaluation through the measurement of emission intensities (intensity ratio method) require two distinct bands; one of which is used as a reference, and the emission intensity of other is monitored as a function of a change in temperature. Herein, we report the influence of excitation wavelengths, and a coupling scheme between lanthanoid and defect emission from the host lattice, to extend the temperature sensing range by using a single crystal of europium (III) phosphate. The temperature dependence of emission intensity was studied for different excitation wavelengths: 365 (intraconfigurational 4f2 excitation), 338 (defect excitation), and 254 nm (O2- →Eu3+ charge-transfer excitation), in the temperature range, 293--865 K. We determined the Boltzmann equilibrium among different coupling schemes using a linear regression model to infer that for an excitation at 338 nm wavelength, and evaluating the intensity ratio between defect emission and the Eu3+ 5D0,1 → 7FJ transitions, the temperature sensing range can be extended upto at least 865 K, with relative sensitivity in the range, 0.33-1.94%K-1 (at 750 K). The results showed resolution of < 1 K with an excellent reproducibility, suggesting that the thermometers can be used with high reliability.
- Published
- 2019
11. Non-quenching photoluminescence emission up to at least 865 K upon near-UV excitation in a single crystal of orange-red emitting SmPO4
- Author
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Sharma, S., Beyer, J., Gloaguen, R., and Heitmann, J.
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SmPO4 ,thermal quenching ,lighting ,photoluminescence - Abstract
The adjustment of photoluminescence emission spectrum and an enhancement in the thermal stability of red/orange-red emitting phosphors is an important issue for the whole lighting industry. Herein, we present our results on the luminescence spectroscopy of a single crystal sample of SmPO4 exhibiting a prominent orange-red emission at 597 nm, along with a charge-transfer absorption (O2− → Sm3+) around 200 nm. We study the temperature dependence of emission spectra in SmPO4 for excitations at 365 and 455 nm, to mimic experimental conditions for phosphor converted light emitting diodes, to show that the sample has a non-quenching photoluminescence emission up to at least 865 K for an excitation at 365 nm, and ∼865 K for an excitation at wavelength, 455 nm. The thermal stability of SmPO4 was found to be much higher than its structural analogue, EuPO4, which is also an orange-red emission phosphor, but possesses a thermal quenching temperature of 710 K (exc. 365 nm), and 735 K (exc. 455 nm). The extraordinary thermal stability of SmPO4 is a result of the energy transfer from deep defects to the Sm3+ ions at high temperatures. The color purity of SmPO4 (65%) was found to be slightly lower than the EuPO4 sample (70%), at room temperature. The results suggests that the rare earth orthophosphate, SmPO4, has a large potential for near-UV excited phosphor converted solid state lighting devices.
- Published
- 2019
12. Effect of RGO-Y2O3 and RGO-Y2O3:Cr3+ nanocomposite sensor for dopamine.
- Author
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Shashikumara, J. K., Kalaburgi, Bhimanagouda, Swamy, B. E. Kumara, Nagabhushana, H., Sharma, S. C., and Lalitha, P.
- Subjects
NANOCOMPOSITE materials ,DOPAMINE ,X-ray diffraction ,TRANSMISSION electron microscopy ,PHOTOLUMINESCENCE - Abstract
The RGO-Y
2 O3 and RGO-Y2 O3 : Cr3+ (5 mol %) nanocomposite (NC) synthesized by hydrothermal technique. The structure and morphology of the synthesized NCs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Y2 O3 :Cr3+ displays spherical-shaped particles. Conversely, the surface of the RGO displays a wrinkly texture connecting with the existence of flexible and ultrathin graphene sheets. The photoluminescence (PL) emission spectra showed series of sharp peaks at 490, 591, and 687 nm which corresponding to4 F9/2 →6 H15/2 ,4 F9/2 →6 H13/2, and4 F9/2 →6 H11/2 transitions and lies in the blue, orange, and red region. The prepared NCs were used for the preparation of modified carbon paste electrodes (MCPE) in the electrochemical detection of dopamine (DA) at pH 7.4. Both modified electrodes provide a good current response towards voltammetric detection of DA. Doping is an effective method to improve the conductivity of Y2 O3 :Cr3+ and developed a method for the sensor used in analytical applications. [ABSTRACT FROM AUTHOR]- Published
- 2021
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13. Photoluminescence, thermoluminescence and photocatalytic studies of sonochemical synthesis of Bi2Zr2O7:Sm3+ nanomaterials.
- Author
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Rajashekharaiah, A. S., Vidya, Y. S., Anantharaju, K. S., Darshan, G. P., Lalitha, P., Sharma, S. C., and Nagabhushana, H.
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THERMOLUMINESCENCE ,GAMMA rays ,PHOTOLUMINESCENCE ,FUEL cycle ,BISMUTH ,METHYLENE blue ,DOSIMETERS - Abstract
Novel Bi
2 Zr2 O7 :Sm3+ (1–9 mol%) nanoparticles (NPs) were synthesized via sonochemical method using Cetyltrimethylammonium bromide (CTAB) as a surfactant. The effects of primary synthesis conditions (pH, growth time, surfactant and dopant concentration) on the surface morphology have been reported for the first time. Photoluminescence (PL) studies (λex = 465 nm), CIE and CCT values revealed that the present nanophosphor could meet the needs of illumination devices and also for domestic appliances. Thermoluminescence studies show a well-resolved glow peak observed at ~ 182 °C along with a shoulder peak at ~ 116 °C be a good candidate for radiation dosimetric applications. This gamma dosimeter can be applied in the routine TL Dosimetry badge system among the gamma radiation workers involved in nuclear fuel cycle operations. Photocatalytic performance of at 5 mol% was experimented in the decolorization of Methylene Blue (MB) under natural Sunlight irradiation. [ABSTRACT FROM AUTHOR]- Published
- 2020
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14. Alpha Lead Oxide (α‐PbO): A New 2D Material with Visible Light Sensitivity
- Author
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Yaowu Hu, Sharma S. R. K. C. Yamijala, Gary J. Cheng, Jing Liu, Swapan K. Pati, Prashant Kumar, Pranay Ranjan, and Joseph Irudayaraj
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Materials science ,Photoluminescence ,Band gap ,business.industry ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Biomaterials ,Monolayer ,Photocatalysis ,Optoelectronics ,General Materials Science ,Density functional theory ,Photonics ,0210 nano-technology ,Electronic band structure ,business ,Biotechnology ,Visible spectrum - Abstract
Even though transition metal dichalcogenides (TMDCs) are deemed to be novel photonic and optoelectronic 2D materials, the visible band gap being often limited to monolayer, hampers their potential in niche applications due to fabrication challenges. Uncontrollable defects and degraded functionalities at elevated temperature and under extreme environments further restrict their prospects. To address such limitations, the discovery of a new 2D material, α-PbO is reported. Micromechanical as well as sonochemical exfoliation of 2D atomic sheets of α-PbO are demonstrated and its optical behavior is investigated. Spectroscopic investigations indicate layer dependent band gaps. In particular, even multilayered PbO sheets exhibit visible band gap > 2 eV (direct) which is rare among semiconducting 2D materials. The emission lifetime of multilayer PbO atomic sheets is 7 ns (dim light) as compared to the monolayer which gives 2.5 ns lifetime and an intense light. Density functional theory calculations of layer dependent band structure of α-PbO matches well with experimental results. Experimental findings suggest that PbO atomic sheets exhibit hydrophobic nature, thermal robustness, microwave stability, anti-corrosive behaviour and acid resistance. This new low-cost, abundant and robust 2D material is expected to find many applications in the fields of electronics, optoelectronics, sensors, photocatalysis and energy storage.
- Published
- 2018
15. Fabricated CeO nanopowders as a novel sensing platform for advanced forensic, electrochemical and photocatalytic applications.
- Author
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Sharma, S., Rohini, B., Nagabhushana, H., Basavaraj, R., Darshan, G., and Sudarmani, R.
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CERIUM oxides ,FORENSIC sciences ,HUMAN fingerprints ,PHOTOLUMINESCENCE ,LIGHT emitting diodes - Abstract
In Forensic investigation, identification of various types of ridge details are essential in order to fix the criminals associated in various crimes. Even though several methods and labeling agents are available to visualize latent finger prints (LFPs) there is still simple, accurate, cost-effective, and non-destructive tool is required. In the present work, CeO nanopowders (NPs) are prepared via simple solution combustion route using Tamarindus indica fruit extract as a fuel. The optimized NPs are utilized for visualization of LFPs on various surfaces by powder dusting method. Results revealed that visualized LFPs exhibit Level 3 features such as pores and ridge contours under normal light with high sensitivity and without background hindrance. The photometric characteristics of the prepared samples exhibit blue color emission and highly useful in warm light emitting diodes. The photocatalytic studies were carried out with different Methylene blue (MB) dye concentration and pH values. The obtained results reveal that the CeO NPs exhibits an excellent catalytic properties which can act as a good catalytic reagent. The findings demonstrate that the prepared NPs are quite useful as a labeling agent for visualization of LFPs, efficient catalysts for dye degradation as well as solid-state lighting applications. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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16. Calotropis gigantean-assisted YSO:Pr nanophosphors: Near-ultraviolet (NUV) photoluminescence and J-O analysis for solid-state lighting solutions.
- Author
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Ramakrishna, G., Nagabhushana, H., Basavaraj, R. B., Naik, Ramachandra, Sharma, S. C., Daruka Prasad, B., Premkumar, H. B., Anantharaju, K. S., and Prashantha, S. C.
- Subjects
CALOTROPIS ,COMBUSTION ,PHOTOLUMINESCENCE ,LIGHTING ,ULTRAVIOLET radiation - Abstract
Y2SiO5:Pr3+(1–9 mol%) nanophosphors were prepared via combustion synthesis usingCalotropis giganteaplant latex as fuel. The PXRD patterns of the sample revealed a monoclinic phase with phase group P21/Cn.14. The crystallite size was found to be in the range of 40–48 nm. The effect of Pr3+cations on the luminescence characteristics of YSO nanoparticles was studied. The CIE chromaticity coordinates were located in the yellow region. Hence, the present phosphor finds applications in light-emitting diodes and display devices. [ABSTRACT FROM PUBLISHER]
- Published
- 2017
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17. Oxygen partial pressure induced effects on the microstructure and the luminescence properties of pulsed laser deposited TiO2 thin films.
- Author
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Pereira, Mario, Gomes, M. J. M., Kunti, A. K., Sharma, S. K., and Sekhar, K. C.
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TITANIUM oxides ,PULSED lasers ,PHOTOLUMINESCENCE - Abstract
In this work, the influence of oxygen partial pressure on structural, morphological, and optical properties of TiO
2 thin films grown on fused quartz substrate at different oxygen partial pressure by pulsed laser deposition were examined. X-Ray diffraction (XRD) patterns show the formation of TiO2 anatase phase deposited at high oxygen pressure. Atomic Force Microscopy (AFM) reveals that surface roughness of the films increases with oxygen pressure. Variation of surface morphology of films with increasing oxygen partial pressure was studied by AFM. It is observed that energy band gap of the films increases from 3.27 eV to 3.52 eV with the increase of oxygen pressure and is attributed to the decrease of oxygen defects. TiO2 thin films exhibited blue emission under the excitation of 320 nm wavelength. De-convoluted photoluminescence (PL) peaks showed that defect states are responsible for visible emission in TiO2 thin films. The intensity of PL emission associated with oxygen vacancies decreases with increasing oxygen pressure. Photometric characteristic analysis shows that the films deposited 1x10-4 mbar oxygen pressure exhibited intense blue emission with high luminescence efficacy of radiation. [ABSTRACT FROM AUTHOR]- Published
- 2017
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18. Role of rhodamine-B dye encapsulated mesoporous SiO in color tuning of SrAlO:Eu,Dy composite long lasting phosphor.
- Author
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Das, Sourav, Manam, J., and Sharma, S.
- Subjects
RHODAMINE B ,MESOPOROUS silica ,SILICA nanoparticles ,PHOTOLUMINESCENCE ,PHOSPHORESCENCE ,ULTRAVIOLET lamps ,LIGHT emitting diodes - Abstract
A novel color tunable dye encapsulated mesoporous SiO/SrAlO:Eu,Dy composite long lasting phosphor (LLP) is developed. The color tuning was obtained by mixing the SrAlO:Eu,Dy (SAO) phosphor with rhodamine-B encapsulated mesoporous silica nanoparticles (MSNp-RhB) with an appropriate ratio. The photoluminescence emission spectra, phosphorescence spectra, photometric and phosphorescence decay measurement were utilized to characterize the composite phosphor. The composite LLP can be excited by UV lamp and also visible light due to broad excitation spectrum of SAO. A near white light emission was achieved with color co-ordinates (0.34, 0.39) and color temperature 5267 K. The detailed process is described here. The nature of phosphorescence decay of the composite LLP did not change with time which ensures constant and steady color during the decay process. The results indicate that the composite LLP can be potentially applicable as a new long lasting phosphor used in the field of emergency light, display, luminous paint and light emitting diode applications. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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19. A study of as-grown, poled and reduced Rh-doped KNbO3 single crystals by high-resolution X-ray diffraction, Raman scattering, photoluminescence and dielectric measurements.
- Author
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Bhagavannarayana, G., Choubey, A., Kushwaha, S. K., Sharma, S. N., Rani, R., and Vijayan, N.
- Subjects
DOPING agents (Chemistry) ,SINGLE crystals ,X-ray diffraction ,RAMAN scattering ,PHOTOLUMINESCENCE - Abstract
As-grown and chemically reduced Rh-doped (1500 p.p.m.) KnbO
3 single crystals grown by the Czochralski method have been characterized. Reduction of the grown crystals at different levels was carried out under a mixture of CO and CO2 gases as the crystals were grown with excess oxygen. The effect of reduction and poling on crystalline perfection was studied by high-resolution X-ray diffraction (HRXRD) using a multi-crystal X-ray diffractometer developed in-house. The diffraction curves of the as-grown, electrically poled, moderately reduced and heavily reduced single-crystal specimens show remarkable differences. The studies by HRXRD reveal that poling has some influence on the improvement of crystalline perfection, while chemical reduction has a great influence on crystalline perfection; at moderate reduction the crystal becomes nearly perfect, but when the reduction is very heavy the crystal quality decreases slightly, although it is still better than for unreduced samples. Asymmetry of the diffraction curves with respect to the peak position reveals that the as-grown specimens contain a high concentration of both vacancies and self-interstitials. After poling, the concentration of self-interstitial defects is lowered to some extent. When the specimen is moderately chemically reduced, the scattered intensity on both sides of the peak is greatly reduced, showing that the concentrations of both vacancies and interstitials are reduced to a great extent owing to chemical reduction. This clearly indicates that, as a result of the chemical reduction of oxygen in the crystal, crystalline perfection is enhanced significantly. However, under heavy chemical reduction, the number of vacancy defects is increased to a significant extent. Raman scattering, dielectric and photoluminescence studies also show interesting features, with excellent correlation with the degree of crystalline perfection influenced by the processes of reduction and poling. [ABSTRACT FROM AUTHOR]- Published
- 2014
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20. Combustion Synthesis of MgO Nanoparticles Using Plant Extract: Structural Characterization and Photoluminescence Studies.
- Author
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Kumar, Danith, Yadav, L. S. Reddy, Lingaraju, K., Manjunath, K., Suresh, D., Prasad, Daruka, Nagabhushana, H., Sharma, S. C., Naika, H. Raja, Chikkahanumantharayappa, and Nagaraju, G.
- Subjects
MAGNESIUM oxide ,METAL nanoparticles ,PHOTONIC band gap structures ,PARTHENIUM ,SOLUTION (Chemistry) ,PLANT extracts ,CRYSTAL structure ,PHOTOLUMINESCENCE - Abstract
Magnesium oxide nanoparticles (MgO Nps) have been successfully synthesized via solution combustion method using Parthenium plant extract as fuel for the first time. Powder X-ray diffraction (PXRD) pattern reveal that product belongs to the cubic phase (Periclase). FTIR spectrum shows the band at 822 cm
-1 indicates the formation of cubic periclase MgO. The optical band gap of MgO Nps estimated from UV -Vis spectrum was found to be in the range 5.40-5.45 eV. SEM images showed that, the product is agglomerated and particle in nature. Photoluminescence (PL) studies shows violet emission at 390 nm, blue emission at 470 nm and green emission at 550 nm. MgO Nps shows good photocatalytic activity for the degradation of methylene blue (MB) dye under UV/Sun light irradiation. [ABSTRACT FROM AUTHOR]- Published
- 2015
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21. Synthesis, characterization, thermo- and photoluminescence properties of Bi co-doped GdO:Eu nanophosphors.
- Author
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Dhananjaya, N., Nagabhushana, H., Nagabhushana, B., Sharma, S., Rudraswamy, B., Suriyamurthy, N., Shivakumara, C., and Chakradhar, R.
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NANOSTRUCTURED materials synthesis ,PHOTOLUMINESCENCE ,PHOSPHORS ,SEMICONDUCTOR doping ,METALLIC oxides ,LOW temperatures ,SOLUTION (Chemistry) ,COMBUSTION ,X-ray diffraction - Abstract
GdO:Eu (4 mol%) co-doped with Bi (Bi = 0, 1, 3, 5, 7, 9 and 11 mol%) ions were synthesized by a low-temperature solution combustion method. The powders were calcined at 800°C and were characterized by powder X-ray diffraction (PXRD), transmission electron microscopy (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 spectra of the synthesized phosphors excited with 230 nm show emission peaks at ∼590, 612 and 625 nm, which are due to the transitions D→F, D→F and D→F of Eu, respectively. It is observed that a significant quenching of Eu emission was observed under 230 nm excitation when Bi was co-doped. On the other hand, upon 350 nm excitation, the luminescent intensity of Eu ions was enhanced by incorporation of Bi (5 mol%) ions. The introduction of Bi ions broadened the excitation band of Eu of which a new strong band occurred ranging from 320 to 380 nm. This has been attributed to the 6s→6s6p transition of Bi ions, implying a very efficient energy transfer from Bi ions to Eu ions. The gamma radiation response of GdO:Eu 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 indicate that GdO:Eu, Bi phosphors have promising applications in solid-state lighting. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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22. STUDIES ON OPTOELECTRONIC PROPERTIES OF Eu3+ ACTIVATED LaOCl NANOPHOSPHOR.
- Author
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CHOUBEY, A., SOM, S., KUMARI, R., and SHARMA, S. K.
- Subjects
OPTOELECTRONICS ,EUROPIUM ,PHOSPHORS ,OXYCHLORIDES ,X-ray diffraction ,PARTICLE size distribution ,BAND gaps ,PHOTOLUMINESCENCE ,EDUCATION - Abstract
The 0.1 mol% europium (Eu
3+ ) activated lanthanum oxychloride nanophosphor was prepared by the liquid-phase method. The X-ray diffraction analysis of the prepared compound exhibits the tetragonal structure having the particles size in the range of 18-21 nm. The band gap of Eu3+ doped LaOCl phosphor was found to be around 5.2 eV using absorption and diffuse reflectance measurements. The photoluminescence (PL) emission spectra show the bright emission in orange-red region from 580 nm to 630 nm. The most intense emission peak at 621 nm was due to transition in energy levels5 D0 →7 F2 of Eu3+ ions. The absorption and stimulated emission cross-section of the intense peak were found to be 4.135 × 10-20 cm2 and 8.9 × 10-20 cm2 respectively. The wide band gap and high stimulated emission cross-section of prepared nanophosphor makes its possible applications as red emitting phosphor in display devices and laser system. [ABSTRACT FROM AUTHOR]- Published
- 2011
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23. Photoluminescence and Raman scattering in axial Si/Ge nanowire heterojunctions.
- Author
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Chang, H.-Y., Tsybeskov, L., Sharma, S., Kamins, T. I., Wu, X., and Lockwood, D. J.
- Subjects
SILICON ,GERMANIUM ,NANOWIRES ,HETEROJUNCTIONS ,PHOTOLUMINESCENCE ,RAMAN effect - Abstract
In crystalline, dislocation-free, Si/Ge nanowire axial heterojunctions grown using the vapor-liquid-solid technique, photoluminescence and Raman spectroscopy reveal a SiGe alloy transition layer with preferential chemical composition and strain. In addition to the lattice mismatch, strain in Si/Ge nanowires is observed from a temperature dependent study to be affected by the difference in Si and Ge thermal expansion. The conclusions are supported by analytical transmission electron microscopy measurements. [ABSTRACT FROM AUTHOR]
- Published
- 2009
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24. Study of photoluminescence behaviors and Judd-Ofelt analysis of Eu3+ doped double perovskite Ba2GdSbO6 phosphor for highly pure and strong red-light generation.
- Author
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Kumari, Chandni, Manam, Jairam, and K Sharma, S.
- Subjects
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PHOSPHORS , *PHOTOLUMINESCENCE , *BEHAVIORAL assessment , *FIELD emission electron microscopy , *LIGHT emitting diodes , *FIELD emission , *REFLECTANCE spectroscopy - Abstract
An array of Eu3+ doped Ba 2 GdSbO 6 luminescent materials have been synthesized by the conventional solid-state (high temperature) reaction route. Surface morphology has been studied via Field Emission Scanning Electron Microscopy. The structural and optical behaviors have been studied using X-Ray Diffraction (XRD), FTIR, Raman spectroscopy, Diffuse reflectance spectroscopy, Photoluminescence excitation (PLE), and Photoluminescence emission (PL) spectra. FTIR and Raman's spectra provided the chemical functional group and different vibrational levels within the samples. The calculated optical band gap was 4.40 eV and 4.47eV for pure and optimized samples respectively. Photoluminescence emission curves have been recorded for 245 nm of excitation wavelength and the highest emission peak was focused at 595 nm corresponding to 5D 0 → 7F 1. Similarly, the Photoluminescence excitation curves were monitored at the emission wavelength of 595 nm and a broad charge transfer band (CTB) was observed from 230 to 285 nm. The emission spectra show the concentration quenching effect beyond the 2 mol% Eu3+ concentration. The corresponding transitions of Eu3+ were further utilized to obtain the Judd-Ofelt (J-O) transition intensity parameters Ω λ (λ = 2, 4) for each sample. Additionally, by studying decay kinetics, the average lifetime of the red emission of the samples has been evaluated, which was 4.622 ms. The photometric study also reveals the CIE coordinates, color purity and CCT values of the proposed phosphor material. Thus, the results obtained from these characterizations, suggest that the prepared sample may behave as a potential candidate in the case of UV-excited red light-emitting phosphor material for light-emitting diodes and field emission devices. • Ba 2 GdSbO 6 : Eu3+ phosphors have been synthesized by solid-state reaction method. • Rietveld refinement has been carried out for better crystal structure analysis. • Raman studies for this host Ba 2 GdSbO 6 have been carried out for the first time. • The phosphors show intense photoluminescence emission with very high color purity. • Judd-Ofelt analysis has been done to understand the spectroscopic behavior of the proposed phosphor material. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
25. Eu3+/Tb3+-codoped Y2O3 nanophosphors: Rietveld refinement, bandgap and photoluminescence optimization.
- Author
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Som, S. and Sharma, S. K.
- Subjects
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RIETVELD refinement , *EUROPIUM , *TERBIUM , *YTTRIUM oxides , *X-ray diffraction , *FOURIER transform infrared spectroscopy , *PHOTOLUMINESCENCE - Abstract
In this work, Eu-doped, Tb-doped and Eu, Tb-codoped Y2O3 nanophosphors were synthesized by the combustion synthesis method. The prepared phosphors were characterized by x-ray diffraction (XRD), Rietveld refinement and Fourier transform infrared (FTIR) spectroscopy. XRD studies and Rietveld refinement confirmed the body-centred cubic structure of doped and codoped phosphors. FTIR studies also confirmed the formation of these compounds. Thermal analysis results indicated that there was no phase transition for all the phosphors in the studied temperature range. In the optical properties, diffuse reflectance (DR) and photoluminescence (PL) measurements were performed. DR spectra were used to determine the bandgap and it increased in the doped and codoped samples due to the crystallite size effect. A strong characteristic emission from Eu3+ and Tb3+ ions was identified and the influence of doping concentration and annealing temperature on PL properties was systematically studied. Transfer of energy was observed from Tb3+ to Eu3+ ions in the codoped phosphor at room temperature. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
26. Synthesis of multicolor emitting Sr2-xSmxCeO4 nanophosphor with compositionally tuneable photo and thermoluminescence.
- Author
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Monika, D. L., Nagabhushana, H., Sharma, S. C., Nagabhushana, B. M., and Krishna, R. Hari
- Subjects
- *
STRONTIUM compounds , *CERIUM compounds , *PHOSPHORS , *CHEMICAL synthesis , *THERMOLUMINESCENCE , *PHOTOLUMINESCENCE , *SELF-propagating high-temperature synthesis , *ENERGY transfer - Abstract
Despite extensive efforts to design a white light generating phosphor, single component phosphors which exhibit multi-color emissions are very limited. In this work we report the synthesis of novel single component colortunable strontium cerate (Sr2-xSmxCeO4) phosphor using facile low temperature solution combustion synthesis. A single-composition, color tunable phosphor is produced by doping with different concentrations of Sm3+ (0.0 to 0.11) into the Sr2CeO4 matrix. Chromaticity of Sr2-xSmxCeO4 depends on the Sm3+ concentration. This is because of energy transfer from Sr2CeO4 to Sm3+ determines the emission colors of the phosphors. At low concentration of Sm3+, Commission Internationale d'Eclairage (CIE) coordinates that are very close to white light emission (0.317, 0.303) are observed. However, at higher dopant concentration (x = 0.11 of Sm3+) the compound exhibits red emission (0.407, 0.343). Hence, a single host multi-color emitting phosphor is realized by doping and energy transfer. Thermoluminescence studies are carried out for Sr2CeO4:Sm3+ phosphor using γ-irradiation in the dose range of 0.5 to 5 kGy. The kinetic parameters, namely activation energy (E), frequency factor (s) and order of kinetics (b) were estimated by Chen's glow peak shape method and are discussed in detail for their possible usage in dosimetry. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
27. Study of defect generated visible photoluminescence in zinc oxide nano-particles prepared using PVA templates.
- Author
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Oudhia, A., Choudhary, A., Sharma, S., Aggrawal, S., and Dhoble, S. J.
- Subjects
- *
PHOTOLUMINESCENCE , *ZINC oxide , *NANOPARTICLES , *WET chemistry , *X-ray diffraction , *VISIBLE spectra - Abstract
Intrinsic defect generated photoluminescence (PL) in zinc oxide nanoparticles (NPs) obtained by a PVA template based wet-chemical process has been studied. A good controllability was achieved on the surface defects, structure and the morphology of ZnO NPs through the variation of solvents used in synthesis. The PL emission strongly depended on the defect structure and morphology. SEM, XRD, annealing and PL excitation studies were used to analyze the types of defects involved in the visible emission as well as the defect concentration. The mechanism for the blue, green and yellow emissions was proposed. The spectral content of the visible emission was controlled through generation/removal of defects through the shape transformation or annealing by focusing on defect origins and broad controls. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
28. An approach to produce single and double layer graphene from re-exfoliation of expanded graphite
- Author
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Dhakate, S.R., Chauhan, N., Sharma, S., Tawale, J., Singh, S., Sahare, P.D., and Mathur, R.B.
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GRAPHENE , *CHEMICAL peel , *GRAPHITE , *ELECTRIC double layer , *SONICATION , *ORGANIC solvents , *CENTRIFUGATION , *SCANNING electron microscopy , *PHOTOLUMINESCENCE - Abstract
Abstract: We report the production of high quality single and double layer graphene from sonication and centrifugation of re-exfoliated expanded graphite (EG) in an organic solvent. The prepared graphene-sheets are identified by Ultraviolet–visible spectroscopy and characterized using different techniques. Transmission and scanning electron microscopy observations show that the graphene-sheets have an area of ∼(12×10)μm2. The selected area electron diffraction analysis and Raman spectroscopy have confirmed the presence of single layer graphene-sheet. The I(2D)/I(G) ratio from the Raman spectrum of graphene is found to be ∼1.7 which suggests the presence of single and double layer graphene. Scanning probe microscopy studies reveals that on re-exfoliation of EG, thickness of graphene layer decreases from 6–7nm to 0.75–1.075nm. This suggests that re-exfoliation overcomes the problem of insufficient oxidation or inadequate pressure that builds-up during first thermal exfoliation of graphite intercalated compound. The photoluminescence spectrum of graphene shows the emission of blue light at ∼390nm which indicates the presence of some functional groups. These graphene-sheets should facilitate the manipulation and processing of graphene based material for various applications. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
29. Studies on hydrothermal synthesis of photolumniscent rare earth (Eu3+ & Tb3+) doped NG@FeMoO4 for enhanced visible light photodegradation of methylene blue dye.
- Author
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Singh, R., Kumar, M., Khajuria, H., Sharma, S., and Sheikh, H. Nawaz
- Subjects
- *
PHOTOLUMINESCENCE , *METHYLENE blue , *NANORODS , *GRAPHENE , *MOLYBDATES , *SEMICONDUCTOR doping - Abstract
FeMoO 4 nanorods and their rare earth (Eu 3+ and Tb 3+ ) doped composites with nitrogen doped graphene (NG) were synthesized by facile hydrothermal method in aqueous medium. X-ray diffraction (XRD) analysis of the as-synthesized samples was done to study the phase purity and crystalline nature. FTIR and Raman Spectroscopy have been studied for investigating the bonding in nanostructures. The surface morphology of the samples was investigated with field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The photolumniscent nature of the samples was investigated by the using the fluorescence spectrophotometer. The photocatalytic degradation efficiency of the prepared pure FeMoO 4 and its rare earth doped composites with nitrogen doped graphene was evaluated as function of visible light irradiation versus concentration of methylene blue (MB dye). The prepared nanocomposites show enhanced photocatalytic efficiency as compared to the bare FeMoO 4 nanorods. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
30. Green, Nonchemical Route for the Synthesis of ZnO Superstructures, Evaluation of Its Applications toward Photocatalysis, Photoluminescence, and Biosensing.
- Author
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Udayabhanu, Nagaraju, G., Nagabhushana, H., Basavaraj, R. B., Raghu, G. K., Suresh, D., Rajanaika, H., and Sharma, S. C.
- Subjects
- *
ZINC oxide synthesis , *SUSTAINABLE chemistry , *CRYSTAL structure , *PHOTOCATALYSIS , *PHOTOLUMINESCENCE , *BIOSENSORS - Abstract
In the present work, we have developed a novel, ecofriendly method for the synthesis of ZnO superstructures for the first time through the thermal decomposition of zinc nitrate precursor without using any fuel. The synthesized materials were thoroughly characterized using various analytical tools such as X-ray diffraction, Fourier-transform infrared spectrometry, UV-vis, scanning electron microscopy, and transmission electron microscopy. Further, it has been used as a photocatalyst for the degradation of one of the environmental pollutants such as methylene blue and also as a biosensor toward the detection of dopamine at trace level. The as-synthesized ZnO nanoparticles showed superior catalytic activity toward the degradation of methylene blue dye with high degree of recyclability with yellow light emitting photoluminescence. The developed sensor showed a linear range for dopamine up to 300 μM with a detection limit of 1 μM with reproduced results over periods of several months without any deviation in its electrochemical performance. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
31. Combustion synthesis of MgO nanoparticles using plant extract: Structural characterization and photoluminescence studies
- Author
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Sharma, S. [Chattisgarh Swami Vivekananda Technological University, Bhilai, Chattisgarh-490009 (India)]
- Published
- 2015
- Full Text
- View/download PDF
32. Defect correlated fluorescent quenching and electron phonon coupling in the spectral transition of Eu{sup 3+} in CaTiO{sub 3} for red emission in display application
- Author
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Sharma, S. [Department of Applied Physics, Indian School of Mines, Dhanbad 826004 (India)]
- Published
- 2014
- Full Text
- View/download PDF
33. Optical and morphological properties of graphene sheets decorated with ZnO nanowires via polyol enhancement
- Author
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Sharma, S. [Department of Physics, Govt. Women Engineering College, Ajmer- 305002 (India)]
- Published
- 2014
- Full Text
- View/download PDF
34. GdAlO3:Eu3+:Bi3+ nanophosphor: Synthesis and enhancement of red emission for WLEDs.
- Author
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Shilpa, C. J., Jayaram, Akila Kadgathur, Dhananjaya, N., Nagabhushana, H., Prashantha, S. C., Sunitha, D. V., Sharma, S. C., Shivakumara, C., and Nagabhushana, B. M.
- Subjects
- *
ALUMINUM oxide , *RARE earth ions , *LIGHT emitting diodes , *PHOSPHORS , *COMBUSTION , *SCANNING electron microscopy - Abstract
GdAlO3, GdAlO3:Eu3+ and GdAlO3:Eu3+:Bi3+ nanophosphors were synthesised by solution combustion technique. Pure orthorhombic phase was obtained from powder X-ray diffraction (PXRD) studies. Scanning electron microscopy (SEM) micrographs showed the porous, agglomerated and irregular shaped particles. The particle size obtained by transmission electron microscopy (TEM) measurement was in good agreement with the values obtained by Debye Scherrer's and W-H plots. The selected area electron diffraction (SAED) pattern show single crystalline nature of the sample. Photoluminescence (PL) measurements were carried out for GdAlO3:Eu3+ and GdAlO3:Eu3+:Bi3+ phosphors excited at a wavelength of 274nm. The characteristic emission peaks of Eu3+ ions were recorded at 590, 614, 655 and 695nm corresponding to 5D0→7FJ (J=1, 2, 3, 4) transitions respectively. However, with addition of Bi3+ ions in GdAlO3:Eu3+, PL intensity drastically enhanced. Orange red color was tuned to deep red color with the addition of Bi3+ ions in GdAlO3:Eu3+ phosphor. Therefore, the phosphor was highly useful as red component in WLEDs. A single well resoled glow peak at 225°C was recorded in GdAlO3 and GdAlO3:Eu3+. Further, with addition of Bi3+ ions, an additional peak at 300°C was recorded. TL glow curves of different UV-exposed GdAlO3:Eu3+:Bi3+ show two TL peaks at 207 and 300°C respectively. The 207°C peak show simple glow peak structure and its intensity increases linearly up to 25min and after that it decrease. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
35. Eco-friendly green synthesis, structural and photoluminescent studies of CeO2:Eu3+ nanophosphors using E. tirucalli plant latex.
- Author
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Malleshappa, J., Nagabhushana, H., Prashantha, S. C., Sharma, S. C., Dhananjaya, N., Shivakumara, C., and Nagabhushana, B. M.
- Subjects
- *
CERIUM oxides , *PHOTOLUMINESCENCE , *PHOSPHORS , *X-ray diffraction , *CHEMICAL sample preparation - Abstract
The investigation involves preparation and photoluminescence properties of CeO2:Eu3+ (1-11mol%) nano phosphors by eco-friendly green combustion route using Euphorbia tirucalli plant latex as fuel. The final product was characterized by powder X-ray diffraction (PXRD), Scanning electron microcopy (SEM) and Transmission electron microscopy (TEM). The PXRD and SEM results reveals cubic fluorite phase with flaky structure. The crystallite size obtained from TEM was found to be ~20-25nm, which was comparable to W-H plots and Scherrer's method. Photoluminescence (PL) emission of all the Eu3+ doped samples shows characteristic bands arising from the transitions of 5D0→5FJ (J=0, 1, 2, 3, 4) manifolds under excitation at 373 and 467nm excitation. The 5D0→7F2 (613nm) transition often dominate the emission spectra, indicating that the Eu3+ cations occupy a site without inversion center. The highest PL intensity was recorded for 9mol% Eu3+ ions with 5ml latex. PL quenching was observed upon further increase in Eu3+ concentration. The international commission on illumination (CIE) chromaticity co-ordinates were calculated from emission spectra, the values (x, y) were very close to national television system committee (NTSC) standard values of pure red emission. The results demonstrate that the synthesized phosphor material could be very useful for display applications. Further, the phosphor material prepared by this method was found to be non toxic, environmental friendly and could be a potential alternative to economical routes. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
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