Faculty Publications
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Item Optimization of process parameters to achieve spectrally selective TiAlC/TiAlCN/TiAlSiCN/TiAlSiCO/TiAlSiO high temperature solar absorber coating(Elsevier Ltd, 2016) Jyothi, J.; Latha, S.; Bera, P.; Nagaraja, H.S.; Barshilia, H.C.TiAlC/TiAlCN/TiAlSiCN/TiAlSiCO/TiAlSiO tandem absorber was deposited on stainless steel substrate by using four cathode reactive direct current unbalanced magnetron sputtering system. The reactive gas flow rates (C2H2, N2 and O2) and thicknesses of each individual layers were varied to obtain the selective properties of the tandem absorber. The detailed effects of reactive gas flow rates and thicknesses of the individual layers on the optical properties were studied by using UV–vis–NIR spectrophotometer. Guiding factor in optimizing various process parameters was to achieve low reflectance in the solar spectrum region and high reflectance in the infrared region. The change in growth rate of the tandem absorber with reactive gas flow rate was studied using the thickness data, target voltage and target current. These results indicate a decrease in the growth rate of each individual layer of the tandem absorber with an increase in the flow rates of the reactive gases. The changes in bonding structure and chemical composition with reactive gas flow rates were studied by X-ray photoelectron spectroscopy. The optimized tandem absorber deposited on stainless steel substrate shows absorptance of 0.960 and emittance of 0.15. The thicknesses of the optimized individual layers were ?62, 18, 20, 16, 27 nm, respectively. © 2016 Elsevier LtdItem Porous nickel telluride nanostructures as bifunctional electrocatalyst towards hydrogen and oxygen evolution reaction(Elsevier Ltd, 2017) Bhat, K.S.; Barshilia, H.C.; Nagaraja, H.S.Electrochemical water splitting technology has attracted researchers for the development of next generation fuels. Herein, we report the synthesis of nanostructured porous hollow nickel telluride nanosheets and their use as bifunctional electrocatalyst towards hydrogen and oxygen evolution reaction, anticipating an enhanced performance owing to their 2D sheet like morphology, conductivity, porous nature providing larger catalytic surface for water splitting reaction. In this regard, nickel telluride nanostructures were synthesized via an anion-exchange-reaction between pre-synthesized nickel hydroxide hexagonal nanosheets and tellurium ions under hydrothermal conditions. The as-synthesized nanostructures were characterized for structural, morphological and compositional properties using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. Nickel telluride modified electrodes were tested as bifunctional electrocatalyst under acidic and alkaline conditions, through linear sweep voltammetry and constant current chronopotentiometry methods. The modified electrodes revealed an onset potential of ?422 mV and 87.4 mV dec?1 Tafel slope towards HER and overpotential of 679 mV and 151 mV dec?1 Tafel slope towards OER. The lower onset potentials are complimented with excellent electrocatalytic stability. © 2017 Hydrogen Energy Publications LLCItem Effect of isoelectronic tungsten doping on molybdenum selenide nanostructures and their graphene hybrids for supercapacitors(Elsevier Ltd, 2019) Bhat, K.S.; Nagaraja, H.S.Electrochemical supercapacitors are vital for the advancement of energy storage devices. Herein, we report the synthesis of molybdenum selenide (MoSe 2 ), tungsten-doped molybdenum selenide (W–MoSe 2 ) and their graphene (G) composites (W–MoSe 2 /G) via a facile hydrothermal method. Physiochemical properties of the as-synthesized samples are examined using X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller measurements, scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy measurements. Used as working electrodes for supercapacitors, MoSe 2 nanostructures could deliver the specific capacitance of 106 F g ?1 at 2 mV s ?1 scan rate. Further, doping with tungsten (W) demonstrates the variation of specific capacitances with 2 M % of tungsten as the optimum doping amount, delivering the maximum specific capacitance of 147 F g ?1 . Furthermore, graphene composites of these nanostructures deliver the enhanced specific capacitances of 248 F g ?1 and complimented with excellent capacitance retention capability of 102% for 20000 cycles. © 2019 Elsevier LtdItem Dual electrochemical application of r-GO wrapped ZnWO4/Sb nanocomposite(Institute of Physics Publishing helen.craven@iop.org, 2019) Brijesh, K.; Bindu, K.; Amudha, A.; Nagaraja, H.S.ZnWO4/Sb nanorods and r-GO-ZnWO4/Sb nanocomposite have been prepared using a single step solvothermal method. The prepared nanocomposites have been characterized using x-ray diffractometer (XRD), Scanning Electron Microscope (SEM), High Resolution Transmission Electron Microscope (HR-TEM), Raman and Brunauer-Emmett-Teller (BET). The x-ray photoelectron spectroscopy (XPS) technique was used to determine the elemental composition of ZWS-5 (5 mg r-GO-ZnWO4/Sb) composite. The XRD reveals the monoclinic wolframite structure of ZnWO4/Sb and r-GO-ZnWO4/Sb. SEM and HRTEM confirms that the ZnWO4/Sb has been decorated on the r-GO sheets. The electrochemical performance of the prepared samples towards the Hydrogen Evolution Reaction (HER) and dopamine sensing has been tested using electrochemical techniques. Onset potential of 265 mV @10 mA cm-2, lower Tafel slope (95 mV dec-1), high electrochemical surface area (1383.216 m2g-1) and high specific site density (18.551 06 × 1021 g-1) of ZWS-5 reveals the high electrocatalytic activity of the composite towards HER. Chronoamperometric dopamine sensing shows that ZWS-5 has the superior sensing performance with highest specific sensitivity (723 ?A ?M-1 ?g-1), lowest limit of detection (0.9624 ?M), along with a good selectivity. Results suggest that the r-GO-ZnWO4/Sb nanocomposite is a good candidate for the HER and electrochemical dopamine sensor. The incorporation of r-GO nanosheets with ZnWO4/Sb (ZWS) nanorods enhances the specific and electrochemical surface area, which accounts for the high electrocatalytic activity of the composite. © 2019 IOP Publishing Ltd.Item ZnWO4/r-GO nanocomposite as high capacity anode for lithium-ion battery(Springer, 2020) Brijesh, K.; Nagaraja, H.S.The pristine ZnWO4 and ZnWO4/r-GO nanocomposite synthesized by the facile solvothermal method were tested as anode materials for lithium-ion battery. Ex situ X-ray photoelectron spectroscopy (XPS) confirms the elemental composition of the pristine ZnWO4 and ZnWO4/r-GO nanocomposite. The ZnWO4/r-GO nanocomposite shows mesoporous nature and exhibits 50.802 m2 g?1 BET specific surface area, which is higher than that of pristine ZnWO4. In addition, the electrochemical property of the pristine ZnWO4 and ZnWO4/r-GO nanocomposite investigated using 2032 half-cell reveals that GO enhances the electrochemical property of the ZnWO4. The ZnWO4/r-GO nanocomposite not only exhibits higher discharge capacity of 1158 mAh g?1 at 100 mA g?1 but also shows longer and stable cycle life at 300 mA g?1 current density. The ZnWO4/r-GO nanocomposite exhibits 80.74% capacity retention even after 500 cycles. The synergetic effect of r-GO and ZnWO4 improves the capacity, columbic efficiency, and stability of the material. The results indicate that ZnWO4/r-GO nanocomposite is an interesting anode material for Li-ion battery with higher capacity complemented with stability compared to pristine ZnWO4. [Figure not available: see fulltext.]. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.Item ZnWO4/SnO2@r-GO nanocomposite as an anode material for high capacity lithium ion battery(Elsevier Ltd, 2020) Brijesh, K.; Vinayraj, S.; Dhanush, P.C.; Bindu, K.; Nagaraja, H.S.Lithium ion battery (LIB) is widely used energy storage device. Herein, we report the preparation of ZnWO4/SnO2 nanocomposite and ZnWO4/SnO2@r-GO nanocomposite via solvothermal method. The structural, elemental and morphological properties of the prepared samples are characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDAX), high-resolution transmission electron microscopy (HR-TEM), Brunauer-Emmett-Teller (BET) measurements, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques. The prepared samples are tested as an anode for LIB. The ZnWO4/SnO2 (5%) nanocomposite delivers initial discharge capacity of 882 mAh g?1 at a current density of 100 mA g?1, while, the specific capacity increases with the increase of SnO2 upto 10% tested in present case. Further, ZnWO4/SnO2@r-GO nanocomposite exhibits a discharge capacity of 1486 mAh g?1 which is higher than that of ZnWO4/SnO2 nanocomposite. In addition, after 500 cycles ZnWO4/SnO2@r-GO nanocomposite exhibits 89.8% cycle life and 98% of discharge capacity retention. These results indicate that, ZnWO4/SnO2@r-GO nanocomposite is a promising anode material for LIB. © 2020 Elsevier LtdItem Synergistic boost in Fe3O4 anode performance for li-ion batteries via Zn and Cu double doping and multi-walled carbon nanotube composite integration(Elsevier B.V., 2024) Kumar, A.; Mukesh, P.; Lakshmi Sagar, G.; Hegde, A.; Nagaraja, H.S.In this study, a novel nanocomposite material comprising pure Fe3O4 (FO), doped Zn0.5Cu0.5Fe2O4-3 (ZCFO-3), and Zn0.5Cu0.5Fe2O4-3@ Multi-walled carbon nanotube (ZCFO-3@MWCNT) nanocomposite material is carefully prepared using a simple one-step hydrothermal process. Comprehensive surface and morphological analysis are conducted using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), and High-resolution transmission electron microscopy (HRTEM), while compositional studies are investigated through Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The electrochemical performance is fully analyzed through Cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS), rate capability tests, discharge/charge capacity, and cyclic stability evaluations. Among these three nanomaterials, ZCFO-3@MWCNT nanocomposite at 100 mA g−1 current density reveals the best performance, with a discharge capacity of 1974 mAh g–1, ZCFO-3 and FO reveal 1340 mAh g–1 and 1317 mAh g–1 respectively. After 800 cycles at 500 mA g−1 current density, ZCFO-3@MWCNT stays strong with a discharge capacity of 646 mAh g–1, while ZCFO-3 manages only 362 mAh g–1 and FO only 111 mAh g–1. After 1200 cycles at 500 mA g−1, the nanocomposite still delivers 518 mAh g–1. This study suggests that ZCFO-3@MWCNT could be a promising anode material for lithium-ion batteries. © 2024 Elsevier B.V.Item A study on the influence of geometric coordination of cobalt ions on the structural, physical and optical properties of borosilicate glass(Elsevier Ltd, 2025) Raghuvanshi, V.; Rashmi, R.; Ingle, A.; Shashikala, H.D.; Nagaraja, H.S.This work explores the synthesis and characterization of cobalt oxide-added borosilicate glass using the melt-quenching technique. The glass system was investigated using various methods, including X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), density measurements, UV–vis spectroscopy, photoluminescence, and electron paramagnetic resonance (EPR) spectroscopy. XRD validated the glass's amorphous nature, while FTIR results indicated significant bonding alterations, showing a transition from BO3 to BO4 units and from B3-O-Si to B4-O-Si linkages. The increased glass density further supported the formation of BO4 units. XPS analysis verified the presence of Co2+ and Co3+ ions within the glass matrix. Optical absorption studies revealed distinct electronic transitions for Co2+ ions in both tetrahedral and octahedral coordination, and for Co3+ ions in octahedral coordination, which was corroborated by EPR spectroscopy. The paramagnetic nature of Co2+ ions was analyzed, and the g-value was determined using X-band frequency. The study also noted the narrowing of the indirect band gap with the rise in the content of Co3O4, and the examination of the metallization criterion suggested a potential metallic nature for the synthesized glasses. Notably, the 0.05 mol% Co3O4-added sample exhibited a 48 % transmission rate and the highest emission, highlighting its potential as an optical bandpass filter. These findings underscore the versatility and tunability of cobalt oxide-added borosilicate glass for various optical technologies. © 2024 Elsevier Ltd and Techna Group S.r.l.Item Influence of titanium redox states on luminescence and conductivity in TiO2 -doped borophosphate glass system(Elsevier B.V., 2025) Rashmi, R.; Ingle, A.; Raghuvanshi, V.; Shashikala, H.D.; Nagaraja, H.S.Borophosphate glasses have garnered significant interest due to their potential for optical and electronic applications. This research delves into the luminescent and conductive properties of 40P2O5–25B2O3-(35-x) BaO-xTiO2 (x = 0–5 mol%) glasses synthesized via the melt-quench method. The glass doped with 4 mol% TiO2 exhibited intense luminescence within the 400–600 nm spectrum, manifesting as a vivid blue emission and the highest Ti3+ ion concentration. Beyond this threshold, the luminescence intensity waned, highlighting the significance of Ti4+/Ti3+ ratios. Absorption spectra and X-ray photoelectron spectroscopy were utilized to study these multivalent ions. Temperature-dependent AC conductivity, exhibited a linear increase, consistent with the Correlated Barrier Hopping (CBH) model. Enhanced polaron hopping between Ti3+ and Ti4+ with increasing TiO2 content improved the dielectric constant and conductivity, peaking at 4.145×10?5 Scm?1 at 5 mol% TiO2 within the 450–530 °C range. These findings underscore the tunability of TiO2-doped glasses for optoelectronic applications. © 2024 Elsevier B.V.Item Novel Ag2Cu2O3 nanorods as stable anode material for lithium-ion battery(Elsevier B.V., 2025) Kumar, A.; Sagar G, L.; P, M.; Hegde, A.P.; Nagaraja, H.S.In this research novel Ag2Cu2O3 nanorods was prepared, for lithium-ion battery as anode, using facile co-precipitation method with four different stirring time and correspondingly Ag2Cu2O3 named ACO – 30 M, ACO – 12 H, ACO – 24 H, and ACO – 36 H. Field Emission Scanning Electron Microscopy (FESEM) and High-Resolution Transmission Electron Microscopy (HRTEM) analyze surface and morphology, while X-ray Diffraction (XRD) examines structural properties. Compositional analysis is carried out using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The electrochemical analysis is evaluated by cyclic stability, rate capability, discharge/charge capacity, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The ACO – 24 H nanomaterial demonstrates an initial discharge capacity of 943 mAh g?1 at a current density of 50 mA g?1. Among the four materials tested, ACO – 24 H shows superior cycling performance, with a discharge capacity of 174 mAh g?1 at 200 mA g?1 after 1003 cycles. In comparison, ACO – 30 M, ACO – 12 H, and ACO – 36 H exhibit capacities of 134 mAh g?1, 91 mAh g?1, and 43 mAh g?1, respectively, under the same conditions. This study suggests that ACO – 24 H is a promising anode material for lithium-ion battery applications. © 2025 Elsevier B.V.