Faculty Publications
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Item Enhanced hydrophilicity and salt rejection study of graphene oxide-polysulfone mixed matrix membrane(2013) Ganesh, B.M.; Isloor, A.M.; A.F., A.F.Graphene oxide (GO) dispersed polysulfone (PSf) mixed matrix membranes were prepared by wet phase inversion method. The morphology of membranes was studied using scanning electron microscope (SEM) images. The variation in hydrophilicity was studied by measuring surface wettability and water swelling experiments. The performance of membranes in terms of pure water flux and salt rejection was studied. SEM images depict enhanced macrovoids, while the contact angle data reveals that, GO incorporated membrane surface is moderately hydrophilic. Membranes exhibited improved salt rejection after GO doping. Membrane with 2000ppm GO loading has exhibited maximum of 72% Na2SO4 rejection at 4bar applied pressure. The salt rejection seems to depend on pH of the feed solution and it has been witnessed that the salt rejection showed an increasing trend with increase in the pH. © 2012 Elsevier B.V.Item Microwave assisted synthesis of rGO/ZnO composites for non-enzymatic glucose sensing and supercapacitor applications(Elsevier Ltd, 2017) Moolayadukkam, M.; Dhanush, S.; Rossignol, F.; Nagaraja, H.S.Zinc oxide (ZnO) and Graphene Oxide (GO) are known to show good electrochemical properties. In this paper, rGO/ZnO nanocomposites have been synthesised using a simple microwave assisted method. The nanocomposites are characterized using XRD, Raman, SEM and TEM. XRD reveals the wurtzite structure of ZnO and TEM shows the heterogeneous nucleation of ZnO nanocrystals anchored onto graphene sheets. The electrochemical properties of the rGO/ZnO nanocomposite enhanced significantly for applications in glucose sensors and supercapacitors. The non-enzymatic glucose sensor of this nanocomposite tested using cyclic voltammetry (CV) and chronoamperometry, exhibits high sensitivity (39.78 mA cm?2 mM?1) and a lower detection limit of 0.2 nM. The supercapacitor electrode of rGO/ZnO nanocomposite exhibits a significant increase in specific capacitance. © 2017 Elsevier Ltd and Techna Group S.r.l.Item TiO2 nanosheet-graphene oxide based photocatalytic hierarchical membrane for water purification(Elsevier B.V., 2017) Nair, A.K.; JagadeeshBabu, J.There is a rising concern over the toxicity of nanomaterials which emphasizes the need for reforms in application of nanomaterials in water treatment. A hierarchical membrane with a thin layer of photocatalyst coated on top of the membrane surface has emerged as a better alternate for immobilization of photocatalyst. Studies have revealed that nanoparticles are not pliable for synthesis of hierarchical membranes due to their smaller size and low stability after deposition. TiO2 nanosheets serve as better alternate due their thin structure which enables stable layer formation. Integrating the nanosheets with modifiers like graphene oxide can further enhance the photocatalytic activity. The sheet structure of graphene oxide enhances stable film formation and also acts as support for interconnecting TiO2 nanosheets. In the present work, TiO2 nanosheets are modified with graphene oxide and used to develop a hierarchical membrane by depositing a catalyst coating on a support membrane. The hierarchical membrane performance was studied using Congo red dye as model pollutant and the effect of catalyst loading on the permeate flux and dye removal were analyzed. © 2017 Elsevier B.V.Item Photoluminescence Quenching in Metal Ion (Cu2+, Co2+) Interacted Graphene Quantum Dots(Wiley-VCH Verlag info@wiley-vch.de, 2017) Mishra, P.; Badekai Ramachandra, B.R.Graphene quantum dots (GQD) are nanosized fragments of graphene with finite band gap. Thus, GQDs show excellent photoluminescence (PL) and also possess good electrochemical properties. In the present study, we synthesized GQDs via hydrothermal (HT) method using Graphene oxide as prepared from improved Hummer's method as a precursor with several modifications. The effect of the variation in the photoluminescence and electrochemical properties of the as-prepared GQDs were studied. Average particle size of the as-synthesized GQDs was roughly 30 nm and produced blue PL on excitation with a wavelength of 365 nm. On reacting the GQDs with Cupric Nitrate and Cobalt Nitrate in separate batches, a significant decrease in the intensity of PL was observed. This quenching of PL of GQDs has been utilized in the qualitative estimation of Metal ion (Cu2+ and Co2+) species in aqueous media. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimItem Polyimide-graphene oxide nanofiltration membrane: Characterizations and application in enhanced high concentration salt removal(Elsevier Ltd, 2018) Khairul Zaman, N.K.; Rohani, R.; Mohammad, A.W.; Isloor, A.M.A membrane usually suffers from a reduction in membrane rejection performance when exposed to a concentrated salt solution. A fabricated polyimide (PI)/graphene oxide (GO) mixed matrix membrane (MMM) was prepared at different GO/PI concentrations (ranging from 0 to 3.5 wt%) to investigate membrane performance in diluted and concentrated salt solutions. Results showed that the MMM possess nanofiltration (NF) properties with high water permeability and excellent salt rejection (99%) in diluted conditions regardless of the applied filtration pressure. The water and permeate permeability increased with the increase in GO content. Interestingly, for concentrated salt solutions, PI/GO MMM only showed at most 4% reduction in rejection, unlike in pure PI membrane, which experienced 16% reduction. A higher amorphous region of the MMM compared to the pure PI in salt solutions was found through XRD. The ionization of GO increases the amorphous structure thus enhances the effective thickness of membrane maintaining the MMM rejection performance. 0.9 wt% GO/PI in MMM showed the highest rejection (98%) in 0.15 M Na2SO4. The presence of GO with its unique properties and highly porous structure was found to retain the membrane rejection properties, especially in concentrated solution. © 2017 Elsevier LtdItem Synthesis and electrochemical properties of silver dendrites and silver dendrites/rGO composite for applications in paracetamol sensing(Elsevier Ltd, 2018) Dhanush, S.; Moolayadukkam, M.; Bindu, K.; Chowdhury, P.; Nagaraja, H.S.Electrochemical sensors are one of the important applications of electrochemistry. In this paper, synthesis, characterization and application of Silver Dendrites and Silver Dendrites/rGO sensors for simple and fast determination of Paracetamol are described. Silver dendrites and their composite with graphene oxide were synthesized by galvanic replacement method. The synthesized samples were characterized by XRD, SEM and TEM. XRD reveals the FCC structure of silver and TEM images show the formation of dendritic silver wrapped in the graphene sheets. The Electrochemical paracetamol sensing properties of these samples were tested using cyclic voltammetry and chronoamperometry. The silver dendrites exhibit a sensitivity of 2.807 × 105?A/mM/g and a lower detection limit of 2.5 ?M, whereas, the composite with graphene oxide exhibits a high sensitivity of 2.511 × 106?A /mM/g with a lower detection limit of 0.025 ?M. © 2018 Elsevier LtdItem Rapid sonochemical synthesis of copper doped ZnO grafted on graphene as a multi-component hierarchically structured visible-light-driven photocatalyst(Elsevier Ltd, 2021) Shenoy, S.; Ahmed, S.; Lo, I.M.C.; Singh, S.; Sridharan, K.Three-dimensional (3D) hierarchical structures (HSs) have demonstrated excellent properties for various applications that are attributable to their distinctive micro-sized architecture with nanoscale substructures. Recently, the ultrarapid sonochemical approach was found to be an effective strategy for synthesizing single component HSs with uniform morphologies in comparison to the direct precipitation technique. We here report the fabrication of copper doped zinc oxide grafted on graphene layers (ZnO-Cux-GOy) for exploring the capability of this ultrarapid approach for synthesizing multi-component HSs. Interestingly, the morphology of ZnO-Cux-GOy HSs studied through electron microscopy revealed the growth of ZnO HSs decorated with Cu nanoparticles and interconnected by graphene layers. ZnO-Cux-GOy HSs demonstrated three-fold higher efficiency in the photodegradation of ibuprofen (IBU) under visible light irradiation in comparison to pristine ZnO HSs, which is attributable to the combined influence of the doped Cu2+ ions and graphene, enabling improved visible light absorption and inhibiting the recombination of photogenerated charges. Thus, the novel ultrarapid sonochemical synthesis strategy demonstrated here is anticipated to open up a new horizon for the time-saving and scalable design of multi-component HSs of various materials for a myriad of applications. © 2021 Elsevier LtdItem Polyoxomolybdate-Polypyrrole-Graphene Oxide Nanohybrid Electrode for High-Power Symmetric Supercapacitors(American Chemical Society, 2021) Maity, S.; Je, M.; Biradar, B.R.; Chandewar, P.R.; Shee, D.; Das, P.P.; Mal, S.Supercapacitors have emerged as one of the most promising candidates for high-performance, safe, clean, and economical routes to store and release of nonfossil energy. Designing hybrid materials by integrating double-layer and pseudocapacitive materials is crucial to achieving high-power and high-energy storage devices simultaneously. Herein, we synthesized a polyoxomolybdate-polypyrrole-graphene oxide nanohybrid via a one-pot reaction. The inclusion of polypyrrole enables a uniform distribution of the polyoxomolybdate clusters; it also confines the restacking of graphene oxide nanosheets. The structural and morphological analysis to unveil the nanohybrid architecture implies excellent interfacial contact, enabling fast redox reaction of polyanions, and a quick transfer of charge to the interfaces. Electrochemical characteristics tested under a two-electrode system exhibit the highest capacitance of 354 F g-1 with significantly high specific energy and power of 49.16 Wh kg-1 and 999.86 W kg-1, respectively. In addition, the cell possesses a high-rate capability and long cycle life by maintaining 96% of its capacitance over 5000 sweeping cycles. The highest specific power of ?10 »000 W kg-1 was computed with Coulombic efficiency of 92.30% at 5 A g-1 current density. Electrochemical impedance spectroscopy additionally reveals enhanced redox charge transfer due to double hybridization. Furthermore, it also demonstrates the impedance and capacitive behavior of supercapacitor cells over a definite frequency regime. ©Item Graphene oxide as nano-material in developing sustainable concrete – A brief review(Elsevier Ltd, 2022) Akarsh, P.K.; Shrinidhi, D.; Marathe, S.; Bhat, A.K.Nanomaterials are the most happening research field in material science. Hydration of cement grains and nano pore filling actions in cement matrix occurring at microscopic levels is greatly benefited by the superior surface area, aspect ratios, size, and greater mechanical characteristics of nano sized materials. Many researchers have used nanoparticles as cementitious materials in concrete. Graphene oxide (GO) is one among many nanomaterials with one of its sides in nano sized measurement and the other two sides are on a bigger scale. One of the advantages of GO over other nanoparticles is that the oxygen functionalities and can be easily dispersed under an aqueous medium. This paper sheds light on brief information about nanotechnology, nanomaterials application in concrete, characterization of GO, and various key researches in the usage of GO in producing concrete of desirable properties. Mainly, GO increases the performance of the resulting cement concrete by creating a strong covalent bond with hydration results like C-S-H. Using polycarboxylate ether and silica fumes the dispersion properties can be effectively improved without forming GO agglomerates. High-Performance cement concrete mixes can be produced by making GO form great bonds with other admixtures. © 2021Item Superior supercapacitance exhibited by acid insoluble Ni(OH)2 in the form of its nanocomposite with rGO(Elsevier Ltd, 2022) Viswanathan, A.; Acharya, M.G.; Prakashaiaha, B.G.; Nityananda Shetty, A.N.The solubility of Ni(OH)2 in acids was been the major impediment that has been preventing the usage of acid electrolytes like 1 M H2SO4 in supercapacitors and batteries that contain Ni(OH)2 as electrode material. This impediment is successfully removed and impressive energy storage characters were achieved from an electrode made up of Ni(OH)2 in the presence of acid electrolyte of 1 M H2SO4. This acid insoluble form of Ni(OH)2 was achieved by synthesizing it in situ in the presence of graphene oxide by chemical reduction method to produce the stable nanocomposite of reduced graphene oxide (rGO) and Ni(OH)2. The insolubility of Ni(OH)2 in 1 M H2SO4 was carefully studied for nearly six months and proved to be a factual observation. Remarkably, the rGO/Ni(OH)2 composite exhibited the better energy storage performance in the presence of 1 M H2SO4 in relation with conventional methods that involve basic electrolytes like NaOH and KOH for Ni(OH)2. The supercapacitor containing rGO/Ni(OH)2 composite and 1 M H2SO4, was stable in storing and delivering the energy without deterioration up to 31,500 cycles, with an uniqueness of increase in energy storage with increase in cycles of energy storage and delivery. Remarkably, two type of faradaic processes are observed to be contributing to the total energy storage of Ni(OH)2, of which one is unprecedented. The superior specific energy (E) and specific capacitance (Cs) achieved are 130.7175 W h kg−1 (comparable with Li-ion batteries of 3 V) and 653.5947 F g−1 at 1 A g−1. This superior Cs is higher than the theoretical Cs expected from this composite for this specific composition (rGO33.33 % and Ni(OH)2 66.66 %) (1571 F g−1) and higher than the theoretical Cs of Ni(OH)2 (2082 F g−1). It is expected that this study would be an inevitable attraction and take the applicability of Ni(OH)2 to higher level and make it one of the meritorious materials for future energy storage. © 2022 Elsevier Ltd
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