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 Air-Stable Cobalt(II) and Nickel(II) Complexes with Schiff Base Ligand for Catalyzing Suzuki–Miyaura Cross-Coupling Reaction(Pleiades journals, 2018) Ansari, R.M.; Kumar, L.M.; Badekai Ramachandra, B.R.The Co(II) complex [Co{C6H4–1,2-(N=CH–C6H4O)2}] (I) and Ni(II) complex [Ni{C6H4–1,2-(N=CH–C6H4O)2}] (II) with Schiff base of o-phenylenediamine and salicylaldehyde have been synthesized. The structure of the ligand and its complexes were derived on the basis of various techniques such as elemental analysis, mass, FT-IR, electronic spectra and magnetic susceptibility. From the Singal crystal X-ray diffraction (SCXRD) analysis techniques (CIF file CCDC no. 1498772 (II)), it has been confirmed that the Schiff base ligand (L), coordinates to the metal ion in a tetradentate fashion through the nitrogen and oxygen atom. In addition, the square planar geometry of Ni(II) complex also has been confirmed from SCXRD. Electronic spectra, mass spectra, and magnetic susceptibility measurements reveal square planar geometry for the Co(II) complex. Synthesized complexes were used in cross-coupling of arylhalides with phenylboronic acid. The transformation offers products in good yields using 0.02 mmol catalysts loading, thereby proving the efficiency of the complexes as catalysts for Suzuki–Miyaura reaction. © 2018, Pleiades Publishing, Ltd.Item 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 Simultaneous adsorption of methylene blue and heavy metals from water using Zr-MOF having free carboxylic group(Elsevier Ltd, 2021) Nimbalkar, M.N.; Badekai Ramachandra, B.R.Industrial effluents contain multiple pollutants, which affect the quality of water remediation operations. Hence, it is important to understand the outcome of the multicomponent adsorption system to develop efficient decontamination process. In this work, acid assisted hydrothermal method (reflux temperature at atmospheric pressure) was employed to synthesize zirconium based metal-organic framework (MOF) and utilized for the adsorptive removal of methylene blue (MB) dye and heavy metals (lead and cadmium) from aqueous solution. The adsorbent was characterized by powder X-ray diffraction (PXRD), which confirms the face centered cubic (FCC) crystal structure similar to previously reported UiO-66. Brunauer–Emmett–Teller (BET) and surface area analysis shows that, the MOF has surface area of 505 m2.g?1 and micropores ranging from 0.4 to 0.7 nm. Fourier transform infrared spectroscopy (FTIR) analysis corroborate the presence of free carboxylic groups at 1710 cm?1, apart from this FTIR confirms the presence of regular bands of metal-carboxylic bonds. X-ray photoelectron spectroscopy (XPS) analysis of the adsorbent was conducted to understand the nature of adsorbate-adsorbent interaction and to confirm the loading of metal ions on adsorbent after adsorption. The morphological nature of the MOF was analyzed by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). Effects of various parameters such as pH, adsorbent dosage, adsorption time and effect of initial concentration of adsorbates on adsorption were evaluated. Kinetics and isotherm studies were conducted to understand the nature and extent of adsorption. Langmuir monolayer adsorption capacity of the adsorbent for cadmium, lead and methylene blue were found to be 37 mg.g?1, 100 mg.g?1 and 169 mg.g?1 respectively. © 2021 Elsevier LtdItem Thermally stable complexes of Fe(III), Co(II), Ni(II) and Cu(II) with Schiff base derived from 4-aminoacetophenone and salicylaldehyde(Springer, 2022) Ansari, R.M.; Ramakrishna, D.; Badekai Ramachandra, B.R.The Schiff base ligand 1-(4-((2-hydroxybenzylidene)amino)phenyl)ethan-1-one, obtained from 4-aminoacetophenone and salicylaldehyde, and its complexes with Fe(III), Co(II), Ni(II) and Cu(II) have been synthesized. These complexes were characterized by FTIR spectroscopy, elemental, and SCXRD analysis. FTIR spectra of complexes show the bidentate coordination of metal ions with ligands where O and N are electron-donating sites of the azomethine group. The electronic absorption spectra of these complexes show the characteristics of absorption bands involved in the Fe, Co, and Ni complexes due to their π→π*, n→π* transitions. Further, the geometry of the complexes was deduced from the calculated magnetic moment values and single crystal XRD analysis. Graphical abstract: A Schiff base derived from the condensation reaction between 2-aminoacetophenone and salicylaldehyde was involved in the formation of four different metal complexes, i.e., with Nickel, Cobalt, Iron, and Copper. The synthetic route to forming these complexes followed an easy process, and the complexes were obtained in good yields.[Figure not available: see fulltext.] © 2022, Indian Academy of Sciences.Item Exploring the microstructural properties of hydroxypropyl-methylcellulose-based solid polymer electrolytes: a promising candidate for flexible electrical double-layer capacitor(John Wiley and Sons Ltd, 2025) Koliyoor, J.; Hegde, S.S.; Ismayil, N.; Badekai Ramachandra, B.R.This study investigates the development and characterization of solid polymer electrolytes based on hydroxypropyl methylcellulose (HPMC) for magnesium ion transport. Electrolyte films were prepared using a conventional solution casting technique, incorporating HPMC and magnesium acetate. Fourier transform infrared (FTIR) spectroscopy and XRD analyses were conducted to examine the interactions between the polymer and salt components. Impedance spectroscopy was employed to assess the electrical conductivity of the prepared electrolytes. Thermal stability was evaluated using TGA. The FTIR and XRD results indicated the formation of a complex between the polymer and salt. The electrolyte containing 30 wt% magnesium acetate exhibited a room temperature ionic conductivity of 5.88 × 10?4 S cm?1, demonstrating enhanced electrical properties. An electrical double-layer capacitor was fabricated using this high-conductivity electrolyte, and its electrochemical performance was analysed. © 2025 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. © 2025 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.