Faculty Publications
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Item A new donor-acceptor type conjugative poly{2-[4-(1-cyanoethenyl)phenyl]-3- (3,4-didodecyloxythiophen-2-yl)prop-2-enenitrile}: Synthesis and NLO studies(2010) Hegde, P.K.; Vasudeva Adhikari, A.V.; Manjunatha, M.G.; Suchand Sandeep, C.S.; Philip, R.This research article describes a technique to synthesize a new donor-acceptor type conjugated polymer carrying cyanophenylenevinylene and 3,4-didodecyloxy thiophene moieties, as an effective optical limiting material. It also includes the evaluation of its linear and nonlinear optical properties and electrochemical studies. The new polymer, viz., poly{2-[4-(1-cyanoethenyl) phenyl]-3-(3,4-didodecyloxythiophen-2-yl)prop-2-enenitrile} (P1) has been synthesized starting from 2,2?-sulfanediyldiacetic acid and diethyl ethanedioate through multistep reactions. In the final step, the polymerization was brought about by Knovenagel condensation. The newly synthesized intermediate, monomer and the polymer (P1) have been characterized by different spectroscopic techniques followed by elemental analysis. Its optical and electrochemical properties are investigated by UV-vis, fluorescence spectroscopy and cyclic voltammetric studies, respectively. The red colored polymer has a well defined structure, good thermal stability and a band gap of 1.78 eV. It emits green fluorescence both in solution and in film state. The third-order nonlinear optical property (NLO) of the polymer was studied by the Z-scan technique. The measurements were performed at 532 nm with 5 ns laser pulses using samples in solution form. An absorptive nonlinearity of the optical limiting type was found in this polymer, which is due to the combined action of saturable absorption and excited state absorption processes. These studies revealed that polymer P1 is a promising material for optical limiting applications. © 2010 Elsevier B.V.Item Nonlinear optical characterization of new thiophene-based conjugated polymers for photonic switching applications(2011) Hegde, P.K.; Vasudeva Adhikari, A.V.; Manjunatha, M.G.; Suchand Sandeep, C.S.S.; Philip, R.This research article describes a technique to synthesize new donor-acceptor-type conjugated polymers carrying 1,3,4-oxadiazolyl-naphthalene and 3,4-(ethylenedioxy/diphenyl)-thiophene moieties (P1 and P2) starting from 2,2?-sulfanediyldiacetic acid and diethyl ethanedioate through multistep reactions. The newly synthesized intermediates and the final polymers have been characterized by different spectroscopic techniques followed by elemental analysis. Their optical and electrochemical properties have been investigated by UV-visible, fluorescence spectroscopy, and cyclic voltammetric studies, respectively. Furthermore, the nonlinear optical transmission properties of these polymers have been investigated by the open aperture z-scan technique. The new polymers P1 and P2 have well-defined structures, good thermal stability, and band gaps of 1.98 and 1.88 eV, respectively. They emit bluish-green fluorescence both in solution and in film state. Interestingly, these polymers show saturable absorption behavior. The results of nonlinear optical studies reveal that they are potential candidates for photonic switching device applications. © 2011 Wiley Periodicals, Inc.Item Investigation of hole-injection in ?-NPD using capacitance and impedance spectroscopy techniques with F4TCNQ as hole-injection layer: Initial studies(Academic Press, 2014) Fernandes, J.M.; Raveendra Kiran, M.R.; Ulla, H.; Satyanarayan, M.N.; Umesh, G.The charge accumulation leading to injection at the organic interface in the sequentially doped hole-only device structure is studied using capacitance and impedance based spectroscopic techniques. In this paper, we investigate the role of p-type dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) in the charge transport properties of N,N'-Di(1-naphthyl)-N,N'-diphenyl-(1,1?-biphenyl)-4,4?-diamine (?-NPD) through sequential deposition. We show that the hole injection into ?-NPD increases with the increase of interlayer (F4TCNQ) thickness by correlating the current density-voltage, capacitance-voltage, capacitance-frequency and impedance measurements. © 2014 Elsevier Ltd. All rights reserved.Item Enhanced photocatalytic performance of N-doped RGO-FeWO4/Fe3O4 ternary nanocomposite in environmental applications(Elsevier Ltd, 2017) Mohamed, M.; Shenoy, U.S.; Bhat, D.K.Nitrogen doped RGO- FeWO4/Fe3O4 (NRGO-FeWO4/Fe3O4) ternary nanocomposite was synthesized by rapid single step microwave irradiation approach using iron acetate, ammonium tungstate and graphene oxide as precursors. The synthesized materials were thoroughly characterized by diffraction, microscopic and spectroscopic techniques. The materials were tested for their catalytic efficiency in photo degradation of Methylene Blue (MB) dye and in reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). MB was mineralized within 100 minutes of visible light irradiation time in the presence of the ternary composite, apart from excellent stability and efficiency even after 10 consecutive cycles. The composite also had the capacity to convert 4-NP into 4-AP within 45 seconds and showed very good catalytic activity even after 20 cycles. The results revealed that ternary composite has way more efficiency than the component materials and can act as a promising catalyst for various environmental and engineering applications. © 2017 Elsevier LtdItem A new colorimetric chemosensors for Cu2+ and Cd2+ ions detection: Application in environmental water samples and analytical method validation(Elsevier B.V., 2017) Tekuri, V.; Trivedi, D.R.A new heterocyclic thiophene-2-caboxylic acid hydrazide based chemosensor R1 to R4 were designed, synthesized and characterized by various spectroscopic techniques like FT-IR, UV-Vis, 1H NMR, 13C NMR, Mass and SC-XRD. The chemosensor R3 showed a significant color change from colorless to yellow in the presence of Cu2+ ions and chemosensor R4 showed a significant color change from colorless to yellow in the presence of Cd2+ ions over the other tested cations such as Cr3+, Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Zn2+, Ag2+, Al3+, Pb2+, Hg2+, K+, Ca2+ and Mg2+. The high selective and sensitivity of R3 towards Cu2+ and R4 towards Cd2+ ions was confirmed by UV-Vis spectroscopic study. The R3 showed a red shift in the presence of Cu2+ ions by ??max 67 nm and R4 showed a red shift in the presence of Cd2+ ions by ??max 105 nm in the absorption spectrum. The binding stoichiometric ratio of the complex between R3 - Cu2+ and R4 - Cd2+ ions have been found to be 1:1 using the B-H plot. Under optimized experimental conditions, the R3 and R4 exhibits a dynamic linear absorption response range, from 0 to 50 ?M for Cu2+ ions and 0 to 30 ?M for Cd2+ ions, with the detection limit of 2.8 × 10?6 M for Cu2+ and 2.0 × 10?7 M for Cd2+ ions. The proposed analytical method for the quantitative determination of Cu2+ and Cd2+ ions was validated and successfully applied for the environmental samples with good precision and accuracy. © 2017 Elsevier B.V.Item Multi-signaling thiocarbohydrazide based colorimetric sensors for the selective recognition of heavy metal ions in an aqueous medium(Elsevier B.V., 2017) Momidi, B.K.; Tekuri, V.; Trivedi, D.R.A series of colorimetric chemosensors R1–R6 have been developed from thiocarbohydrazide derivatives, for the selective detection of heavy metal ions. The structures of the receptors R1–R6 were well characterized by standard spectroscopic techniques like FT-IR, 1H NMR, and ESI-MS. The solid structure of receptor R1 and R2 were derived by single crystal X-ray diffraction (SC-XRD). The cation reorganization abilities of receptors R1–R6 were studied by UV–Vis spectroscopy. The receptors R1, R3 and R4 acts as a tremendous sensitive probe for heavy metal ions (Hg2 +, Cd2 + and Pb2 +) with the ?M detection (R1 for Hg2 +, 2.72, R3 for Cd2 +, 3.22, R4 for Hg2 +, Cd2 + & Pb2 +, 0.70, 0.20 & 0.30 ?M) and the receptors R2, R5 & R6 are sensitive towards Cu2 + ions with the ?M detection (3.34, 0.90 & 1.20 ?M) in an aqueous medium among all other tested cations. The receptor R4 shows a multi-color response towards Hg2 +, Cu2 +, Cd2 + and Pb2 + ions. The recognition mechanism, stoichiometric binding ratio and detection limit (DL) have been examined by UV–Visible spectroscopic titration experiments and Benesi-Hildebrand (B-H) plot, receptor R1–R6 sowed 1:1 binding ratio with good binding constant range of 103 to 105 M? 1 with Hg2 +, Cu2 +, Cd2 + and Pb2 + ions metal ions. © 2017 Elsevier B.V.Item Colorimetric anion sensors based on positional effect of nitro group for recognition of biologically relevant anions in organic and aqueous medium, insight real-life application and DFT studies(Elsevier B.V., 2018) Singh, A.; Sahoo, S.K.; Trivedi, D.R.A new six colorimetric receptors A1-A6 were designed and synthesized, characterized by typical common spectroscopic techniques like FT-IR, UV–Visible, 1H NMR, 13C NMR and ESI-MS. The receptor A1 and A2 exhibit a significant naked-eye response towards F? and AcO? ions in DMSO. Due to presences of the NO2 group at para and ortho position with extended ?-conjugation of naphthyl group carrying –OH as a binding site. Compared to receptor A2, A1 is extremely capable of detecting F? and AcO? ions present in the form of sodium salts in an aqueous medium. This is owed to the occurrence of –NO2 group at para position induced in increasing the acidity of –OH proton. Consequently, it easily gets deprotonated in aqueous media. The detection limit of receptor A1 was turned out to be 0.40 and 0.35 ppm for F? and AcO? ions which is beneath WHO permission level (1.0 ppm). Receptor A1 shows a solitary property of solvatochromism in different aprotic solvents in presence of AcO? ion. Receptor A1 depicts high selectivity towards AcO? ion in DMSO: HEPES buffer (9:1, v/v). Receptor A1 proved itself for real life application by detecting anion in solution and solid state. The binding mechanism of receptor A1 with AcO? and F? ions was monitored from 1HNMR titration and DFT study. © 2017 Elsevier B.V.Item Photophysical and electrochemical properties of organic molecules: Solvatochromic effect and DFT studies(Elsevier B.V., 2018) Mohan, M.; Pangannaya, S.; Satyanarayan, M.N.; Trivedi, D.R.A series of five Schiff base molecules M1, M2, M3, M4 and M5 have been designed and synthesized by aldol condensation reaction. Synthesized molecules have been characterized by standard spectroscopic techniques in order to confirm their structural traits. The solvatochromic behavior of molecules M1 to M5 in solvents of varying polarity were investigated by UV–Vis, fluorescence spectroscopy and supported by TD-DFT calculations. DFT studies performed in the gas phase confirmed the energy stabilized structure of the molecules M1 to M5. Structural characteristics of molecule M2 favored higher fluorescence emission with a quantum yield of 0.35 and a solid-state emission of 512 nm. Fluorescence lifetime measurement of the molecules M1 to M5 exhibited a lifetime of order 2–5 ns. Overall, molecule M2 can find its application in organic light emitting diodes as a non-dopant emitter material. © 2018 Elsevier B.V.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 Hg 2+ induced hydrolysis of thiazole amine based Schiff base: Colorimetric and fluorogenic chemodosimeter for Hg 2+ ions in an aqueous medium(Elsevier B.V., 2019) Tekuri, V.; Sahoo, S.K.; Trivedi, D.Simple pyrene-based chemosensors 1 to 3, were synthesized from pyrene-1-carboxaldehyde and they were characterized using various spectroscopic techniques like UV–Vis, FT-IR, Mass, 1 H NMR and 13 C NMR. Among synthesized receptors, the receptor 1 shows high selectivity towards Hg 2+ ions. Further, the high selectivity of receptor 1 towards Hg 2+ ions in the presence of various other interfering metal ions like Ni 2+ , Zn 2+ , Mn 2+ , Co 2+ , Cu 2+ , Cr 3+ , Fe 3+ , Al 3+ , Ag + , Fe 2+ , Cd 2+ , Mg 2+ , Pb 2+ , Ca 2+ , Na + , K + was confirmed by UV–Vis and fluorescence methods. The detection limit for Hg 2+ ions was found to be 0.270 ?M. The chemodosimetric irreversible hydrolysis of the receptor 1 in the presence of Hg 2+ was studied by UV/Vis, fluorescence, FT-IR, LC-MS, 1 H NMR and theoretical DFT study. Further, the real life applications of receptor 1 for the determination of Hg 2+ ions were demonstrated by UV–Vis method. © 2019 Elsevier B.V.