Faculty Publications

Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736

Publications by NITK Faculty

Browse

Has files: NoSubject: search.filters.subject.Synthesis (chemical)

Search Results

Now showing 1 - 10 of 122
  • No Thumbnail Available
    Item
  • No Thumbnail Available
    Item
    The direct conversion of benzene to phenol by hydroxylation with hydrogen peroxide was carried out over catalysts containing iron impregnated on activated carbon. Iron was impregnated on various surface modified activated carbons. The catalyst that was made by treating activated carbon with nitric acid, that was treated thermally in the presence of nitrogen at 600 °C and impregnated with 5 wt.% iron, gave a phenol yield of 20%. It was found that the synergistic interactions of surface groups and the impregnated iron have enhanced the performance of these catalysts. © 2005 Elsevier B.V. All rights reserved.
    (Direct synthesis of phenol from benzene on iron-impregnated activated carbon catalysts) Choi, J.-S.; Kim, T.-H.; Choo, K.-Y.; Sung, J.-S.; Saidutta, M.B.; Ryu, S.-O.; Song, S.-D.; Badekai Ramachandra, B.; Rhee, Y.-W.
    2005
  • No Thumbnail Available
    Item
    Studies on nonlinear optical parameters of bis-chalcone derivatives doped polymer
    (Elsevier BV, 2006) Shettigar, S.; Chandrasekharan, K.; Umesh, G.; Sarojini, B.K.; Narayana, B.
    Two bis-chalcone derivatives, 1,5-[di(4-methoxyphenyl)]penta-1,4-dien-3-one and 1,5-[di(4-chlorophenyl)]penta-1,4-dien-3-one were synthesized. Their SHG conversion efficiencies are reported to be 6.0 and 5.0 times that of urea and hyper polarizabilities are 9.9×10-30 and 10.2×10-30 esu, respectively. The third-order nonlinear optical properties in PMMA matrix were studied by Z-scan technique using 7 ns laser pulses at 532 nm. The nonlinear refractive index ?, nonlinear absorption coefficient ?, magnitude of effective third order susceptibility ?(3) and the coupling factor ? have been investigated. The values obtained are of the order of 10-14 cm2/W, 1.2 cm/GW, 10-14 esu and 0.2, respectively, which are comparable with the values obtained in stilbazoleum like dyes. The experimental investigation also shows that they are very interesting optical limiting materials and their optical limiting behaviour is mainly due to two photon absorption phenomenon. © 2006 Elsevier Ltd. All rights reserved.
  • No Thumbnail Available
    Item
    Synthesis and characterization of new light-emitting copolymers containing 3,4-dialkoxythiophenes
    (2006) Udayakumar, D.; Vasudeva Adhikari, A.V.
    We report the synthesis, optical and electrochemical properties of a new series of polyoxadiazoles (P1-P3) consisting of 3,4-dialkoxythiophene and 1,4-divinylbenzene units. The polymers are prepared using the precursor polyhydrazide route. The polymers have well defined structure and exhibit good thermal stability with the onset decomposition temperature in nitrogen at around 330 °C. The optical and charge-transporting properties of the polymers are investigated by UV-vis spectroscopy, fluorescence emission spectroscopy and cyclic voltammetry. The UV-vis absorption spectra of polymers in solution showed a maximum at around 380 nm. The polymers depicted bluish-green fluorescence in solutions and green fluorescence in thin films. Cyclic voltammetry studies reveal that these copolymers have low-lying LUMO energy levels ranging from 3.25 to 3.31 eV and HOMO energy levels ranging from 5.48 to 5.56 eV, which indicated that the polymers are expected to provide enhanced charge-transporting (electron transport/hole blocking) properties for the development of efficient polymer light-emitting diodes (PLEDs). © 2006 Elsevier B.V. All rights reserved.
  • No Thumbnail Available
    Item
    Synthesis and characterization of nanocrystalline Mo-V-W-Fe-O mixed oxide catalyst and its performance in selective methanol oxidation
    (2007) Badekai Ramachandra, B.; Choi, J.-S.; Kim, T.-H.
    A mixed oxide catalyst containing Mo, V, W and Fe with the composition of 63, 23, 09 and 06 wt% respectively for the selective oxidation of the methanol to formaldehyde is in reported in this paper for the first time. The characterization of the catalyst was done using BET surface analysis, X-ray diffraction (XRD), Infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Energy dispersive X-ray (EDX). The mixed oxide after calcination at 673 K in N2 which was subjected for the thermal activation in N 2flow at 813 K was used for the methanol selective oxidation. The thermal treatment shows enhanced catalytic performance. Thermal activation of the nanocrystalline Mo0.63V23W0.09Fe 0.06O x precursor oxide in nitrogen atmospheres induces partial crystallization of a Mo5O14-type oxide only in a narrow temperature range up to 813 K. XRD showed that the thermally activated mixed oxide consists of a mixture of a majority of crystalline Mo 5O14-type oxide and of small amounts of crystalline MoO3-type and MoO2-type oxides. The structural analysis suggests that the improvement of the catalytic performance of the MoVWFe oxide catalyst in the selective oxidation of methanol is related to the formation of the catalytic active site such as Mo5O14-type mixed oxide. © 2007 Springer Science+Business Media, LLC.
  • No Thumbnail Available
    Item
    Synthesis and nonlinear optical characterization of copolymers containing alternating 3,4-dialkoxythiophene and 1,3,4-oxadiazolydbenzene units
    (2007) Udayakumar, D.; Kiran, A.J.; Vasudeva Adhikari, A.V.; Chandrasekharan, K.; Shashikala, H.D.
    We report the synthesis and linear and third-order nonlinear optical (NLP) characterization of two novel copolymers containing alternating 3,4-dialkoxythiophene and 1,4-bis(1,3,4-oxadiazolyl)benzene units. The copolymers were synthesized with a precursor polyhydrazide route. Both copolymers exhibited fluorescence around 430 nm under the irradiation of UV light. The NLO measurements were made with the single-beam Z-scan technique with Nd:YAG nanosecond laser pulses at 532 nm. The nonlinear refractive index of the investigated copolymers was negative, and the magnitude was as high as 10 -10 esu. The samples exhibited strong reverse saturation absorption and very good optical limiting properties at the wavelength used. The concentration dependence of third-order NLO parameters was studied. ©2007 Wiley Periodicals, Inc.
  • No Thumbnail Available
    Item
    Third-order nonlinear optical susceptibilities of new copolymers containing alternate 3,4-dialkoxythiophene and (1,3,4-oxadiazolyl)pyridine moieties
    (Elsevier, 2009) Hegde, P.K.; Vasudeva Adhikari, A.V.; Manjunatha, M.G.; Poornesh, P.; Umesh, G.
    A new series of conjugated copolymers (P1-P3) consisting of alternate 3,4-dialkoxythiophene and (1,3,4-oxadiazolyl)pyridine moieties have been synthesized using the precursor polyhydrazide route. They have been characterized by FTIR, 1H NMR spectral and elemental analyses. These copolymers possess well defined structure and exhibit good thermal stability with the onset decomposition temperature in nitrogen at around 300 °C. Their molecular weights were determined by gel permeation chromatography (GPC). The optical and charge-transporting properties of the copolymers were investigated by UV-visible spectroscopy, fluorescence emission spectroscopy and cyclic voltammetry. Their UV-visible absorption spectra showed a ?max at around 342 nm and displayed bluish-green fluorescence in solution state. The band gaps were found to be at about 2.55 eV for all the copolymers. The third-order nonlinear optical properties (NLO) of these copolymers were studied by Z-scan technique. The measurements were performed at 532 nm with 7 ns laser pulses using a Nd:YAG laser in solution form. The real part of ?(3) were estimated to be -0.881 × 10-12, -0.901 × 10-12 and -1.030 × 10-12 esu for P1, P2 and P3 respectively. The imaginary part of ?(3) for the copolymers P1, P2 and P3 were determined to be 0.192 × 10-12, 0.253 × 10-12 and 0.272 × 10-12 esu respectively. The copolymers exhibit strong reverse saturable absorption and good optical limiting behaviour at 532 nm. © 2008 Elsevier B.V. All rights reserved.
  • No Thumbnail Available
    Item
    Design and synthesis of new donor-acceptor type conjugated copolymers derived from thiophenes
    (2009) Manjunatha, M.G.; Vasudeva Adhikari, A.V.; Hegde, P.K.
    A new series of donor-acceptor type poly(thiophene) derivatives (P1-P3) were synthesized starting from thiodiglycolic acid and diethyl oxalate through multistep reactions. In the final step, the polymerization was carried out using Wittig reaction. This is a good synthetic route for the preparation of any desired p- and n-type copolymers. The optical and potential charge-transporting properties of the copolymers were investigated by UV-vis, fluorescence emission spectroscopy and cyclic voltammetry. The copolymers exhibited bluish-green/green fluorescence in their thin film forms. Cyclic voltammetry experiments showed that these copolymers have low-lying LUMO energy levels ranging from -2.98 to -3.11 eV and high lying HOMO energy levels ranging from -5.45 to -5.65 eV. The optical and electrochemical studies reveal that new copolymers are new promising materials for the development of efficient polymer light emitting diodes. © 2008 Elsevier Ltd. All rights reserved.
  • No Thumbnail Available
    Item
    Synthesis and nonlinear optical characterization of new poly{2,2?-(3,4-didodecyloxythiophene-2,5-diyl)bis[5-(2-thienyl)-1,3,4-oxadiazole]}
    (2009) Hegde, P.K.; Vasudeva Adhikari, A.V.; Manjunatha, M.G.; Suchand Sandeep, C.S.; Philip, R.
    A new donor-acceptor type poly{2,2?-(3,4-didodecyloxythiophene-2,5-diyl)bis[5-(2-thienyl)-1,3,4-oxadiazole]} (P) was synthesized starting from thiodiglycolic acid and diethyl oxalate through multistep reactions. The polymerization was carried out using chemical polymerization technique. The optical and charge-transporting property of the copolymer was investigated by UV-vis, fluorescence emission spectroscopic and cyclic voltammetric studies. The copolymer shows UV absorption maxima at 375 nm and displays bluish-green fluorescence in DMF solution. Its electrochemical band gap was determined to be 2.07 eV. The nonlinear optical (NLO) properties of the copolymer was investigated at 532 nm using single beam Z-scan and degenerate four-wave mixing (DFWM) techniques with nanosecond laser pulses. The copolymer exhibits strong optical limiting behavior due to effective three-photon absorption (3PA). Values of the effective 3PA coefficient (?), third-order nonlinear susceptibility (?(3)) and figure of merit (F) have been calculated. © 2009 Elsevier B.V. All rights reserved.
  • No Thumbnail Available
    Item
    Supramolecular synthons in noncovalent synthesis of a class of gelators derived from simple organic salts: Instant gelation of organic fluids at room temperature via in situ synthesis of the gelators
    (2009) Das, U.K.; Trivedi, D.R.; Adarsh, N.N.; Dastidar, P.
    (Chemical Equation Presented) The supramolecular synthon approach has been employed to synthesize noncovalently a series of low molecular mass organic gelators (LMOGs) derived from benzylammonium salts of variously substituted benzoic acids. The majority of the salts (75%) prepared showed interesting gelation properties. Instant gelation of an organic fluid, namely methyl salicylate, was achieved at room temperature by using most of the gelator salts by in situ synthesis of the gelators. Table top rheology and scanning electron microscopy (SEM) were used to characterize the gels. Single crystal X-ray diffraction studies revealed the presence of both 1D and 2D supramolecular synthons. X-ray powder diffraction (XRPD) studies indicated the presence of various crystalline phases in the fibers of the xerogels. By using these data, a structure-property correlation has been attempted and the working hypothesis for designing the gelator has been reinforced. © 2009 American Chemical Society.