Faculty Publications
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Item Synthesis and photocatalytic properties of graphitic carbon nitride nanofibers using porous anodic alumina templates(Institute of Physics Publishing helen.craven@iop.org, 2017) Suchitra, S.M.; Udayashankar, N.K.In the present study, we describe an effective method for the synthesis of Graphitic carbon nitride (GCN) nanostructures using porous anodic alumina (AAO) membrane as template by simple thermal condensation of cyanamide. Synthesized nanostructure was fully analysed by various techniques to detect its crystalline nature, morphology, luminescent properties followed by the evaluation of its photocatalytic activity in the degradation of Methylene blue dye. Structural analysis of synthesized GCNNF was systematically carried out using x-ray powder diffraction (XRD) and scanning electron microscope (SEM), and. The results confirmed the growth of GCN inside the nanochannels of anodic alumina templates. Luminescent properties of GCNNF were studied using photoluminescence (PL) spectroscopy. PL analysis showed the presence of a strong emission peak in the wavelength range of 350-600 nm in blue region. GCNNF displays higher photocatalytic performance in the photodegradation of methylene blue compare to the bulk GCN. Highlights 1. In the present paper, we report the synthesis of graphitic carbon nitride nanofibers (GCNNF) using porous anodic aluminium oxide membranes as templates through thermal condensation of cyanamide at 500 °C. 2. The synthesis of Graphitic carbon nitride nanofibers using porous andic alumina template is the efficient approach for increasing crystallinity and surface area. 3. The high surface area of graphitic carbon nitride nanofibers has a good impact on novel optical and photocatalytic properties of the bulkGCN. 4. AAO templating of GCN is one of the versatile method to produce tailorable GCN nanostructures with higher surface area and less number of structural defects. 5. Towards photocatalytic degradation of dyes, the tuning of physical properties is very essential thing hence we are succeeded in achieving better catalytic performance of GCN nanostructures by making use of AAO templates. © 2017 IOP Publishing Ltd.Item 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.Item Defect-induced measurements of semi-organic ammonium hydrogen oxalate oxalic acid dihydrate single crystals using gamma irradiation(Taylor and Francis Ltd., 2022) Mahendra, K.; Maria Fernandes, J.; Udayashankar, N.K.The structural, optical, mechanical and electrical properties of pure and 5—20-kGy gamma-irradiated semi-organic single crystals of ammonium hydrogen oxalate oxalic acid dihydrate (NH4H3(C4O8).2H2O) are presented. The crystals were synthesized at room temperature using facile solvent evaporation technique. Powder XRD measurements indicate gradual enhancement in crystallinity and lattice defect annihilation for low radiation dosage. Radiation-induced increase in optical band gap (4.01–4.16 eV) indicates high damage threshold of the crystals. Quenching of photoluminescence is attributed to the lowering of surface defect density with radiation. The influence of gamma radiation on the functional vibrations of the crystals is studied using FTIR-Raman spectroscopy. Vickers microhardness measurements show gradual enhancement in crystal hardness with the increase in radiation. An increase in forward resistance with irradiation is observed from I–V measurements and is attributed to high transparency of the crystals. These results indicate the viability of NH4H3(C4O8) 2H2O crystals in potential space optoelectronic applications. © 2022 Informa UK Limited, trading as Taylor & Francis Group.Item Growth of octahedral structured AgBiS2 single crystals and its insights on the high performance electrocatalytic hydrogen generation(Elsevier Ltd, 2024) Jauhar, R.O.M.; Ramachandran, K.; Deepapriya, S.; Joshi, S.; Ghfar, A.A.; Rao, L.; Badekai Ramachandra, B.R.; Udayashankar, N.K.; Vadivel, V.; Raji, R.; Kim, B.C.; Rodney, J.D.Given the enormous depletion of fossil fuels and growing environmental concerns, there is an immediate need to develop alternative and clean energy sources. Hydrogen (H2), recognized for its cleanliness and renewability, is poised to meet future energy requirements. Consequently, ongoing research is focused on the development of electro-active, durable, and cost-effective catalysts to replace expensive noble metal-based electrocatalysts. In this study, microscale AgBiS2 chalcogenide derived from a single crystal is reported as promising electrocatalysts for the Hydrogen Evolution Reaction (HER) with a remarkably low overpotential. The physico-chemical characterization of the AgBiS2 catalyst has been investigated using various analytical techniques. The synthesized AgBiS2 catalyst exhibits excellent HER activity, manifesting a low overpotential of 86 mV at a current density of 10 mA cm−2 and a Tafel slope of 44 mV dec−1, along with superior stability even after 24 h in HER at a very high current density. The developed AgBiS2 also showcased stable production when subjected to a two-electrode system. The enhanced alkaline HER activity of AgBiS2 can be attributed to its phase purity, high crystallinity, and the presence of high active sites. The observed high electrochemical performance and stability position AgBiS2 as a potential electrocatalyst for the hydrogen evolution reaction. This finding holds significant promise in the quest for efficient, durable, and economically viable catalysts to drive the shift towards clean and renewable energy sources. © 2024 Hydrogen Energy Publications LLC