Faculty Publications

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Effect of Erioglaucine dye dopant on the structural, optical, mechanical, electrical and nonlinear properties of ammonium dihydrogen phosphate single crystal
(Elsevier B.V., 2020) Fernandes, J.M.; Mahendra, K.; Udayashankar, N.K.
The structural, optical, mechanical, electrical and nonlinear properties of standard Ammonium Dihydrogen Phosphate (NH4H2PO4, ADP) single crystals incorporating organic Erioglaucine dye dopant are presented. The effect of Erioglaucine dye dopant at varied concentration on these properties has been investigated through measurement of powder X-Ray Diffraction (XRD), UV–Vis and photoluminescence spectroscopy, Vickers microhardness, light dependent I–V measurements and Second Harmonic Generation studies. These measurements reveal that doping with increasing dye concentration of Erioglaucine leads to change in properties of the ADP single crystals, making them suitable for optoelectronic applications. The Erioglaucine doped ADP single crystals were grown using solvent evaporation technique at room temperature. Optical properties like absorbance and emission of these crystals are determined using UV–vis and photoluminescence spectroscopy, respectively. Optical bandgap and photoluminescence of the crystals are found to increase with dye doping, indicating their suitability in photonic applications. The mechanical properties of the crystals are determined using Vickers microhardness measurement technique. Light dependent I–V measurements exhibit negative photoconductivity behavior of the ADP crystals. However, the current through the crystals is observed to increase with increase in doping concentration of the Erioglaucine dye. Second Harmonic Generation studies show enhancement in nonlinearity for doped crystals. Our experiments indicate gradual variance in the crystallinity, emission, hardness, conductivity and nonlinearity of the sample with change in dye concentration. © 2020 Elsevier B.V.
Spray-pyrolyzed rare-earth dysprosium-doped SnO2 thin films for plausible photocatalytic application
(Springer, 2023) Fernandes, J.M.; Reddivari, R.; Maharana, G.; Janbandhu, S.Y.; Jayavelu, Y.; Kovendhan, M.; Venkateswaran, C.; Sangaraju, S.; Joseph, D.P.
Rare-earth element dysprosium (Dy)-doped SnO2 plays a crucial role in optoelectronics due to its tunable emission property in the visible region. Using simple spray pyrolysis process, trivalent rare-earth Dy (0–5 wt%) is successfully incorporated into the SnO2 lattice as Dy-doped SnO2 (DTO) thin films. X-ray diffraction measurements indicate that the films are considerably textured. Binding energy and elemental charge state are explored using X-ray photoelectron spectroscopy. Optical transmittance of 88.17% and band gap of 3.99 eV is observed for 2 wt% Dy-doped (DTO2) film. Among all the doped films, DTO2 film shows higher hydrophilicity (contact angle 70.7°) due to higher surface roughness (5.71 nm), which is beneficial for photocatalytic activity. The DTO2 film also shows highest carrier concentration (1.8 × 1019 cm−3) and electrical conductivity (3.19 Scm−1). Although, the electrical sheet resistance of the DTO films is high, it can be fine-tuned by further careful optimization of several deposition and/or doping parameters. It is observed that 2 wt% Dy doping into the SnO2 lattice aids the tunability of its optical and electrical properties according to device requirements. Photocatalytic activity of all the spray-pyrolyzed thin films is investigated by degrading methylene blue (MB) dye. The degradation efficiency is found to be highest for DTO2 film (~ 86% for 240 min) under visible LED light irradiation supported by a defect mediated mechanism. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Defect-mediated time-efficient photocatalytic degradation of methylene blue and ciprofloxacin using tungsten-incorporated ternary perovskite BaSnO3 nanoparticles
(Elsevier Ltd, 2024) Jayavelu, Y.; Maharana, G.; Rajender, G.; Reddivari, R.; Divyadharshini, S.; Baby, B.H.; Kovendhan, M.; Fernandes, J.M.; Joseph, D.P.
Photocatalytic water purification has been extensively explored for its economic, eco-friendly, and sustainable aspects. In this study, tungsten (W) incorporated BaSn1-xWxO3 (x = 0 to 0.05) nanoparticles synthesized by facile hydrogen peroxide precipitation route has been demonstrated for photocatalytic degradation of methylene blue (MB) dye and ciprofloxacin (CIP) antibiotic. The structural analysis indicates the presence of hybrid composite-like nanostructures with reduced crystallinity. Optical studies reveal blueshift in bandgap and decrease in oxygen vacancy defects upon W-incorporation. Pure BaSnO3 shows overall enhanced photocatalytic activity towards MB (90.22%) and CIP (78.12%) after 240 min of white LED light and sunlight irradiation respectively. The 2 % W-incorporated BaSnO3 shows superior photocatalytic degradation of MB (26.89%) and CIP (45.14%) within first 30 min of irradiation confirming the presence of W to be beneficial in the process. The free radical study revealed the dominant role of reactive hole (h+) and oxygen radical (O2•−) species during photodegradation and their intermediates are investigated to elucidate the degradation mechanism of MB within 30 min of irradiation. This study is promising towards developing defect mediated and time-efficient photocatalysts for environmental remediation. © 2024 Elsevier Ltd

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