Faculty Publications
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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 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 Enhanced photostability and optical nonlinearity of nickel and cobalt organometallic complexes(Elsevier B.V., 2019) Manjunatha, K.B.; Rajarao, R.; Poornesh, P.; Rudresha, B.J.; Umesh, G.; Badekai Ramachandra, B.R.Nonlinear optical and limiting properties of nickel, cobalt metal-organic complexes and ligand (L) {L = N,N?-o-phenylenebis (4-hyrdoxy-salicylideneimine)} were studied using Z-scan technique using Q-switched Nd: YAG laser with nanosecond pulses at 532 nm. The results reveal that metal complexes exhibit large negative nonlinear refractive index (n2) of the order of 10?11 esu. The metal complexes displays large nonlinearity than the ligand due to effective charge delocalization between metal ion and ligand. The magnitude of ground state absorption cross section is small compared to the effective excited-state absorption cross section implying the observed nonlinearity is due to reverse saturable absorption. Further, metal-organic complexes exhibit enhanced optical limiting behaviour at nanosecond laser pulses. © 2019 Elsevier B.V.Item Synthesis and application of Zr-metal–organic framework for simultaneous detection and rapid adsorption of p-nitrophenol from water(Institute for Ionics, 2023) Nimbalkar, M.N.; Badekai Ramachandra, B.R.The p-nitrophenol is a prime raw material in the manufacturing of pharmaceutical drugs, fungicides and insecticides. The effluents from these industries contain p-nitrophenol and are harmful to human and aquatic life. Hence, development of fast detection and efficient disposal process of p-nitrophenol in wastewater is a major concern. In this study, fluorescent active smart metal–organic framework (MOF) was employed for the simultaneous detection and adsorptive removal of p-nitrophenol from water. Photoluminescence active zirconium-based metal–organic framework having isostructural with UiO-66 framework was synthesized by using mixed ligand strategy with the replacement of BDC (1,4-Benzenedicarboxylic acid) ligand from 10 to 30 mol% with H3ntb ligand (4,4ʼ,4ʼʼ-Nitrilotrisbenzoic acid, in house synthesised fluorescence active trifunctional ligand). The powder X-ray diffraction (PXRD), analysis of the synthesised MOF confirms face centred cubic (FCC) crystal structure similar to pristine UiO-66. From Fourier transform infrared spectroscopy (FTIR), the peak at 1251 cm−1 for the tertiary amine group validated the presence of H3ntb ligand. The obtained MOFs have the surface area from 1039 m2g−1 to 949.1 m2g−1 and pore volume ranging from 0.04973 cm3g−1 to 0.05160 cm3g−1. Experimental results indicated that MOF was able to detect p-nitrophenol at low concentration (≈35 μM) and to remove rapidly (< 10 min) it from the aqueous solution. The adsorption process obeys Langmuir isotherm (monolayer adsorption capacity is 62 mgg−1) and kinetics by Elovich model indicating adsorption nature as chemisorption on a heterogeneous surface. Graphical abstract: [Figure not available: see fulltext.] © 2022, The Author(s) under exclusive licence to Iranian Society of Environmentalists (IRSEN) and Science and Research Branch, Islamic Azad University.