Faculty Publications
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Item Structural health monitoring capabilities in ceramic-carbon nanocomposites(2014) Inam, F.; Badekai Ramachandra, B.R.; Vo, T.; Daoush, W.M.A novel method for analysing structural health of alumina nanocomposites filled with graphene nanoplatelets (GNP), carbon nanotubes (CNTs) and carbon black nano-particles (CB) is presented. All nanocomposites were prepared using novel colloidal processing and then by Spark Plasma Sintering. Good homogeneous dispersion was observed for all carbon filled materials. Nanocomposite bars were indented to produce sub-surface damage. Change in electrical conductivities were analysed after indentation to understand structural damage. For correlating change in electrical conductivity and indentation damage and understanding damage tolerance, mechanical properties were compared. Because of the systematically induced indentation damage, a sharp decrease of 86% was observed in the electrical conductivity of CNT nanocomposite as compared to 69% and 27% in the electrical conductivities of GNP nanocomposites and CB nanocomposites respectively. CNTs impart superior damage sensing capability in alumina nanocomposites, in comparison to GNP and CB, due to their fibrous nature, high aspect ratio and high electrical conductivity. © 2013 Elsevier Ltd and Techna Group S.r.l.Item Structural stability studies of graphene in sintered ceramic nanocomposites(Elsevier Ltd, 2014) Inam, F.; Vo, T.; Badekai Ramachandra, B.R.The post-sintering structural stability of graphene in alumina nanocomposites synthesised by Spark Plasma Sintering (SPS) and Hot Pressing (HP) was compared. Raman spectroscopy, thermogravimetric analyses and electrical conductivity analyses were conducted to characterise degradation of graphene due to the utilisation of different sintering techniques and conditions. Scanning Electron Microscopy confirmed good dispersion of graphene in SPSed and HPed sample. Graphene in SPSed and HPed nanocomposite samples sintered using longer durations (60 min) were found to possess higher crystallinity, thermal stability and electrical conductivity as compared to SPSed samples sintered using shorter sintering durations (10-20 min). This was attributed to the thermally induced graphitisation caused by longer sintering durations, which was lacking in SPSed samples processed using shorter sintering durations and lower temperature. No additional effect of DC pulsed current on the structural stability of graphene for nanocomposites were observed for samples prepared by SPS. © 2014 Elsevier Ltd and Techna Group S.r.l.Item Nickel-oxide multiwall carbon-nanotube/reduced graphene oxide a ternary composite for enzyme-free glucose sensing(Royal Society of Chemistry, 2016) Prasad, R.; Ganesh, V.; Badekai Ramachandra, B.R.We report a solvent-free method of preparation for a NiO-carbon nanotube/graphene ternary composite using nickel formate as a green precursor via a thermal decomposition method. In this ternary composite, NiO with an average particle size of 7 nm is regularly decorated on the surfaces of conductive carbon matrix networks such as MWCNTs and reduced graphene oxide (rGO). Here rGO serves as an ideal support for the uniform distribution of NiO nanoparticles and also functions as an efficient transducer material, whereas, MWCNTs act as a spacer between rGO, which enhances the electrical conductivity and accessibility of the active reaction sites for direct glucose oxidation. The electrochemical performances were evaluated by cyclic voltammetry and amperometric techniques. Under the optimal conditions, the 20 wt% NiO-MWCNT/rGO/GCE exhibits a sensitivity of 4223.3 ?A cm-2 mM-1 and a detection limit of 0.92 ?M over a linear glucose concentration range up to 19 mM. Furthermore, the constructed sensor is effectively employed to detect glucose in real human blood serum samples with adequate results. The modified 20 wt% NiO-MWCNT/rGO/GCE also shows a high sensitivity, greater selectivity, excellent reproducibility and long-term stability. © 2016 The Royal Society of Chemistry.Item RGO supported Co-Ni bimetallic magnetically separable nanocatalysts for the reduction of 4-Nitrophenol(Elsevier Ltd, 2016) Prasad, R.; Lolakshi, M.K.; Badekai Ramachandra, B.R.The Cobalt-Nickel-reduced graphene oxide ternary composite was prepared using eco-friendly, solvent-free and low temperature CVD method where in metal formates were used as metal precursor. The structure, composition and morphology of synthesized samples were characterized by several related techniques like X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The catalytic efficiency towards reduction of an organic pollutant such as 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) was explored and the reaction parameters like temperature, weight ratio of the composite was optimised and rate constant of the reactions were measured. The results show 8% Co-Ni-rGO are having high catalytic efficiency and can complete the reduction reaction within 250 s at 45 °C. Furthermore, catalyst being magnetically separable shows high stability after ten successive reactions. Hence, the Co-Ni-rGO composite can be a potential promising material to catalyse the reduction of 4-NP. © 2016 Elsevier B.V. All rights reserved.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 Synthesis and characterization of graphene quantum dots and their size reduction using swift heavy ion beam(Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2018) Mishra, P.; Badekai Ramachandra, B.R.Graphene quantum dots (GQDs) are nanosized fragments of graphene displaying quantum confinement effect. They have shown to be prepared from various methods which include ion beam etching of graphene. However, recently the modification of the GQDs has garnered tremendous attention owing to its suitability for various applications. Here, we have studied the effect of swift ion beam irradiation on the properties of GQDs. The ion beam treatment on the GQDs exhibited the change in observed photoluminescence of GQDs as they exhibited a blue luminescence on excitation with longwave UV (?365 nm) due to the reduction in size and removal of the ethoxy (–C–O–C–) groups present on the quantum dots. This was confirmed by transmission electron microscopy, particle size analysis, and Fourier transform infrared spectroscopy. © 2018 Informa UK Limited, trading as Taylor & Francis Group.Item Cobalt Schiff Base Immobilized on a Graphene Nanosheet with N, O Linkage for Cross-Coupling Reaction(American Chemical Society, 2019) Saroja, A.; Badekai Ramachandra, B.R.A simple and direct pathway to synthesize heterogeneous catalyst by covalently immobilizing a cobalt Schiff base complex on the surface of amino functionalized graphene oxide for the cross coupling of aryl halides and arylboronic acids is reported. The as synthesized samples were characterized using various spectroscopic techniques and thermal analysis to attain their structural and functional features. The analysis confirmed that the Co bounded to the ligand using bi(N, O) linkage and the Co Schiff base complex immobilized onto the functionalized graphene oxide through its amino moiety. The catalytic investigation confirmed the product yield up to 96.5% for the Suzuki cross coupling using gas chromatography. ICP analysis shows that the central active metal is 85% in its catalyst even after the fifth iteration. High product yield, environmentally benign, easy workup, easy filtration of catalyst, and mild reaction conditions are the main facets of this catalyst. © Copyright 2018 American Chemical Society.Item Copper complex with N-,O- architecture grafted graphene oxide nanosheet as a heterogeneous catalyst for Suzuki cross coupling reaction(Taiwan Institute of Chemical Engineers, 2019) Anuma, S.; Mishra, P.; Badekai Ramachandra, B.R.We report a straight forward synthesis of a heterogeneous catalyst by covalently immobilizing copper Schiff base complex on the surface of amino functionalized graphene oxide (AGO) for the Suzuki coupling of substituted aryl halides with arylboronic acids. The as-synthesized complex and subsequent catalyst were characterized for their structural features using suitable techniques. The analysis confirmed that the Cu bound to Schiff base (L) ligand via bi(N-,O-) linkage and Cu-L immobilization on AGO was due to its amino functionality. The catalyst exhibited excellent yield of 94% for Suzuki coupling reactions as analyzed by gas chromatography. The catalyst was recycled for 5 successive reactions with insignificant loss in efficiency. ICP-AES analysis showed the catalyst retained 87.5% of its active metal center after 5th iteration. High yield, environmentally benign, easy work-up procedure, easy separation of catalyst and mild reaction conditions are some of the important facets this catalyst offer. © 2018 Taiwan Institute of Chemical EngineersItem Aggregative ways of graphene quantum dots with nitrogen-rich edges for direct emission spectrophotometric estimation of glucose(Elsevier B.V., 2019) Mishra, P.; Badekai Ramachandra, B.R.We report a facile one step in-situ synthesis of amino-functionalized graphene dots. These quantum dots were employed for the detection of glucose in both standard aqueous solutions and commercially available fruit juice to assess its practicability. The characterization of the quantum dots revealed that they were decorated with amine functionality. Additionally, the interaction between glucose and amine functionalized graphene quantum dots gave enhancement in the UV–vis absorption and photoluminescence (PL) due to aggregation of quantum dots via glucose link. Therefore, the quantum dots were able to detect the concentration of glucose in solution exhibiting linearity from 0.1 to 10 mM and 50–500 mM with a sensitivity transition from 10 mM to 50 mM. The limit of detection for the determination of glucose was found to be 10 ?M. This determination was agreed from both UV–Vis absorption and PL spectroscopy. However, the PL emission method of determination was most suited with its very high accuracy of 98.04 ± 1.96% and 97.33 ± 2.67% for the linear range of glucose concentration within 0.1–10 mM and 50–500 mM, respectively. The PL enhancement was highly selective towards glucose in mixture of other form of sugars making it suitable for determining glucose in food samples. © 2019Item Polypyrrole functionalized Cobalt oxide Graphene (COPYGO) nanocomposite for the efficient removal of dyes and heavy metal pollutants from aqueous effluents(Elsevier B.V., 2021) Anuma, S.; Mishra, P.; Badekai Ramachandra, B.R.A cobalt oxide graphene nanocomposite functionalized with polypyrrole (COPYGO) having a heterogenous porous structure was synthesized using hydrothermal method. Microscopic imaging of the COPYGO surface revealed its highly porous and ordered features. The adsorption performance of the COPYGO composite was systemically investigated for Methylene Blue (MB), Congo red (CR) dyes and toxic lead (Pb(II)) and Cadmium (Cd(II)) metals. These were selected as they are the common pollutants in industrial wastewater. The COPYGO was found to be thermally stable up to 195 oC with a specific surface area of 133 m2 g?1. Experimental data indicates that the COPYGO follows Langmuir and Temkin adsorption isotherm. The COPYGO was efficient in removing MB (92.8%), CR (92.2%), Pb(II) (93.08%) and Cd(II) (95.28%) pollutants at pH 7.2, 5.0, 5.5 and 6.1 respectively from the simulated effluents. The maximum adsorption capacity (Qmax) observed for MB 663.018 mg g-1, CR 659.056 mg g-1, Pb(II) 780.363 mg g?1 and Cd(II) 794.188 mg g?1 pollutants. The thermodynamic analysis of the COPYGO indicates that the adsorption is endothermic and spontaneous in nature. COPYGO showed very high efficient removal rate for the pollutants in simulated effluents which guaranteed its benefits and efficacy in industrial wastewater treatment. © 2021 Elsevier B.V.