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Item Amelioration of opto - Electronic response of thiophene - Imidazo[2,1- b] [1,3,4]thiadiazole based organic semiconductors(American Institute of Physics Inc. subs@aip.org, 2019) Kakekochi, K.; Udayakumar, U.Two new donor-acceptor (D - A) type organic semiconductors V-1 and V-2 containing thiophene as the donor unit were designed and synthesized following Knoevenagel condensation reaction. The structures of the synthesized molecules were characterized by mass spectroscopy and 1H NMR spectroscopy. The photophysical properties were investigated by UV-vis spectroscopy and fluorescence spectroscopy. The electrochemical properties were studied by cyclic voltammetry. The density functions theory (DFT) studies were performed to examine the frontier molecular orbital energy states. Both electrochemical analysis and DFT studies revealed that the HOMO of V-2 is shifted to higher energy compared to that of V-1 due to the stronger electron donating ability of methoxy group in V-2 compared to that of methyl group in V-1. The optical and electrochemical results revealed that the synthesized organic semiconductors are suitable donor materials for bulk hetero - junction solar cells. © 2018 Author(s).Item Synthesis and characterization of thiophene and fluorene based donor-acceptor conjugated polymer containing 1,3,4-oxadiazole units for light-emitting diodes(2012) Murali, M.G.; Naveen, P.; Udayakumar, U.; Yadav, V.; Srivastava, R.A new donor-acceptor (D-A) conjugated polymer (PDTOF) containing 3,4-didodecyloxythiophene, fluorene and 1,3,4-oxadiazole units is synthesized by using Wittig reaction methodology. The synthesized polymer is characterized by 1H NMR, FTIR, GPC, and elemental analysis. The optical energy band gap of the polymer is found to be 2.42 eV as calculated from the onset absorption edge. The electrochemical studies of PDTOF reveal that, the HOMO and LUMO energy levels of the polymer are -5.45 eV and -3.58 eV, respectively. The polymer is thermally stable up to 320 °C. Polymer light-emitting diode devices are fabricated with a configuration of ITO/PEDOT: PSS/PDTOF/Al using PDTOF as the emissive layer. The electroluminescence (EL) spectrum of the device showed green emission with CIE coordinate values (0.34, 0.47). By current density-voltage characteristics, threshold voltage of the PLED device is found to be 6.5 V. © 2011 Elsevier Ltd. All rights reserved.Item Synthesis, characterization, and nonlinear optical properties of donor-acceptor conjugated polymers and polymer/Ag nanocomposites(2012) Murali, M.G.; Udayakumar, U.; Sridharan, K.Two new donor-acceptor (D-A) conjugated polymers P1 and P2 containing 3,4-didodecyloxythiophene and 1,3,4-oxadiazole units are synthesized via Wittig reaction methodology. Cyclic voltammetry studies reveal that the polymers are both p and n dopable, and possess low-lying LUMO energy levels (-3.34 eV for P1 and -3.46 eV for P2) and high-lying HOMO energy levels (-5.34 eV for P1 and -5.27 eV for P2). The optical band gap of the polymers is in the range of 2.25-2.29 eV, calculated from the onset absorption edge. The polymers emit orange to yellow light in the film state when irradiated with a UV light. The synthesized polymers are used to prepare polymer nanocomposites with different wt% of silver nanoparticles. The polymer nanocomposites are characterized by UV-Vis absorption spectroscopy, field emission scanning electron microscopy, and thermogravimetric analysis. Both polymers and polymer/ Ag nanocomposites show good thermal stability with onset decomposition temperature around 300 °C under nitrogen atmosphere. The nonlinear optical properties of polymers and polymer/Ag nanocomposites are measured by Z-scan technique. Both polymers and polymer nanocomposites show a good optical limiting behavior. Nearly five times enhancement in the nonlinear optical properties is observed for polymer/Ag nanocomposites. The value of effective two-photon absorption coefficient (?) is in the order of 10 -10-10 -11 m/W. These results indicate that the synthesized polymers (P1 and P2) and their Ag nanocomposites are expected to be good candidates for application in photonic devices. © Springer Science+Business Media, LLC 2012.Item New thiophene-based donor-acceptor conjugated polymers carrying fluorene or cyanovinylene units: Synthesis, characterization, and electroluminescent properties(John Wiley and Sons Inc, 2013) Murali, M.G.; Udayakumar, U.; Yadav, V.; Srivastava, R.Two new thiophene-based donor-acceptor (D-A) conjugated polymers, PDTOFV and PDTOCN, are synthesized and characterized. The polymers are readily soluble in common organic solvents and exhibit good thermal stability with onset decomposition temperature (Td) in the range 310-330°C. Cyclic voltammetry studies revealed that polymers possess low-lying highest occupied molecular orbital (HOMO) energy levels (-5.94 eV for PDTOFV and -5.86 eV for PDTOCN) and low-lying lowest unoccupied molecular orbital (LUMO) energy levels (-3.35 eV for PDTOFV and -3.55 eV for PDTOCN). The optical band gap is calculated from onset absorption edge of the polymer film. The polymers exhibit green fluorescence with fluorescence quantum yields (?fl) of 38% and 42%, respectively, for PDTOFV and PDTOCN. Polymer light-emitting diodes (PLEDs) are fabricated using these polymers with a device configuration of ITO/PEDOT:PSS/polymer/Al. The device based on PDTOFV emitted green light with Commission Internationale de I'Eclairage (CIE) coordinate values of (0.25, 0.39). Whereas, the device based on PDTOCN showed white light emission with CIE coordinate values of (0.32, 0.35), which is very close to the values (0.33, 0.33) of standard white light emission. The threshold voltages of the PLEDs are determined by current density-voltage characteristics and are found to be 7.3 and 3.9 V for PDTOFV and PDTOCN, respectively. © 2012 Society of Plastics Engineers.Item Thiophene-based donor-acceptor conjugated polymer as potential optoelectronic and photonic material(2013) Murali, M.G.; Udayakumar, U.; Yadav, V.; Srivastava, R.; Safakath, K.In this paper, we report the synthesis, characterization and optical properties of a donor-acceptor conjugated polymer, PTh-CN, containing 3,4-didodecyloxythiophene and cyanovinylene units. The polymer possesses a low band gap of 1.75 eV as calculated from the onset absorption edge. From the electrochemical study, the HOMO and LUMO energy levels of the polymer are figured out to be -5.52 eV and -3.52 eV, respectively. Polymer light-emitting diodes are fabricated using PTh-CN as the emissive layer with a device configuration of ITO/PEDOT:PSS/PTh-CN/Al. The device showed stable saturated red electroluminescence with CIE coordinate values (0.65, 0.32) at 12 V, which are very close to the values for standard red demanded by the NTSC. In addition, the device showed good colour stability under different bias voltages and the threshold voltage of the PLED device is found to be as low as 3.1 V. Further, a nanocomposite of the polymer and TiO2 nanoparticles is prepared by the dispersion method. The nonlinear optical properties of PTh-CN and PTh-CN/TiO 2 nanocomposite are studied using z-scan technique. The polymer solution, polymer film and polymer/TiO2 nanocomposite film show a strong saturable absorption behaviour. The value of saturation intensity (I s) is found to be of the order 1011-1012 W/m2, indicating that the materials are useful candidates for photonic applications. [Figure not available: see fulltext.] © 2013 Indian Academy of Sciences.Item Identification and characterization of novel indole based small molecules as anticancer agents through SIRT1 inhibition(2013) Panathur, N.; Udayakumar, U.; Koushik, P.V.; Alvala, M.; Yogeeswari, P.; Sriram, D.; Kumar, V.In our pursuit to develop new potential anticancer leads, we designed a combination of structural units of indole and substituted triazole; and a library of 1-{1-methyl-2-[4-phenyl-5-(propan-2-ylsulfanyl)-4H-1,2,4-triazol-3- yl]-1H-indol-3-yl}methanamine derivatives was synthesized and characterized. Cytotoxic evaluations of these molecules over a panel of three human cancer cell lines were carried out. Few molecules exhibited potent growth inhibitory action against the treated cancer cell lines at lower micro molar concentration. An in vitro assay investigation of these active compounds using recombinant human SIRT1 enzyme showed that one of the compounds (IT-14) inhibited the deacetylation activity of the enzyme. The in vivo study of IT-14 exemplified its promising action by reducing the prostate weight to the body weight ratio in prostate hyperplasia animal models. A remarkable decrease in the disruption of histoarchitecture of the prostate tissues isolated from IT-14 treated animal compared to that of the positive control was observed. The molecular interactions with SIRT1 enzyme were also supported by molecular docking simulations. Hence this compound can act as a lead molecule to treat prostatic hyperplasia. © 2013 Elsevier Masson SAS. All rights reserved.Item Synthesis and study of optical properties of linear and hyperbranched conjugated polymers containing thiophene and triphenylamine units(2014) Prashanth Kumar, K.R.; Murali, M.G.; Udayakumar, U.We report the synthesis of solution processable donor-acceptor type conjugated monomer (M1) and polymers (P1 and P2) consisting of electron-accepting 1,3,4-oxadiazole unit and electron-donating 3,4-didecyloxythiophene, and triphenylamine units through Wittig polycondensation reaction. The linear polymer P1 is thermally stable up to 325 °C whereas the hyperbranched polymer P2 showed better thermal stability with an onset of decomposition at 375 °C. Polymer P2 showed lower band gap energy (1.96 eV) than that of P1 (2.09 eV). Polymers P1 and P2 emit yellow and orange light, respectively, under the irradiation of UV light. Electrochemical studies revealed that the polymers possess high-lying highest occupied molecular orbital and low-lying lowest unoccupied molecular orbital energy levels. Polymer light-emitting diodes are fabricated with the device configuration of ITO/PEDOT:PSS/polymer (P1 or P2)/Al. The device based on P2 showed a very low threshold voltage of 2 V. The third-order nonlinear optical properties of the polymers are studied using Z-scan technique. Both polymers showed a strong optical limiting behavior. The value of nonlinear absorption coefficient (?) of the polymers is of the order 10-10mW-1 which indicates that these materials may be accomplished for fabricating optical limiters. © 2013 Taylor & Francis.Item Indole-3-carbinol and 1,3,4-oxadiazole hybrids: Synthesis and study of anti-proliferative and anti-microbial activity(CSIRO, 2015) Gokhale, N.; Panathur, N.; Udayakumar, U.; Kumsi, M.In the present study, molecular hybrids of indole-3-carbinol and 1,3,4-oxadiazole-2-thiols have been designed and synthesized. The thiol analogues consisted of diversely substituted benzyl and alkyl groups with different electronic properties. The structures of all the newly synthesized scaffolds and target compounds were ascertained using 1H NMR, 13C NMR, mass spectrometry, and elemental analyses. All the final compounds were screened in vitro for their anti-proliferative and anti-microbial activity. Three compounds showed excellent anti-proliferative activity with more than 70% cell growth inhibition against three cancer cell lines, HepG2 (human liver hepatocellular carcinoma), HeLa (human cervix carcinoma), and MCF-7 (human breast carcinoma). In the anti-microbial studies, compounds with electron-withdrawing fluoro or nitro substituent displayed appreciable activity similar to that of standard drugs. Also, the final compounds are non-toxic to non-cancerous Vero cell line. © 2015 CSIRO.Item Synthesis and biological evaluation of new imidazo[2,1-b][1,3,4]thiadiazole-benzimidazole derivatives(Elsevier Masson SAS infos@masson.fr 62 rue Camille Desmoulins Issy les Moulineaux Cedex 92442, 2015) Ramprasad, J.; Nayak, N.; Udayakumar, U.; Yogeeswari, P.; Sriram, D.; Peethambar, S.K.; Achur, R.; Santosh Kumar, H.S.S.In this report, we describe the synthesis and biological evaluation of a new series of 2-(imidazo[2,1-b][1,3,4]thiadiazol-5-yl)-1H-benzimidazole derivatives (5a-ac). The molecules were analyzed by 1H NMR, 13C NMR, mass spectral and elemental data. The structure of one of the pre-final compounds, 6-(4-methoxyphenyl)-2-(4-methylphenyl)imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde (4d) and that of a target compound, 2-[2-methyl-6-(4-methyl phenyl) imidazo[2,1-b][1,3,4]thiadiazol-5-yl]-1H-benzimidazole (5aa) were confirmed by single crystal XRD studies. All the target compounds were screened for in vitro anti-tuberculosis activity against Mycobacterium tuberculosis H37Rv strain. Seven (5c, 5d, 5l, 5p, 5r, 5z and 5aa) out of twenty nine compounds showed potent anti-tubercular activity with a MIC of 3.125 ?g/mL. A p-substituted phenyl group (p-tolyl or p-chlorophenyl) in the imidazo[2,1-b][1,3,4]thiadiazole ring and/or a chloro group in the benzimidazole ring enhance anti-tuberculosis activity whereas a nitro group in the benzimidazole ring reduces the activity. In the antibacterial screening, compounds 5i, 5w and 5ac showed promising activity against the tested bacterial strains. Further, antifungal and antioxidant activities of these molecules were also investigated. In the cytotoxicity study, the active antitubercular compounds exhibited very low toxicity against a normal cell line. © 2015 Elsevier Masson SAS.Item New indole-isoxazolone derivatives: Synthesis, characterisation and in vitro SIRT1 inhibition studies(Elsevier Ltd, 2015) Panathur, N.; Gokhale, N.; Udayakumar, U.; Koushik, P.V.; Yogeeswari, P.; Sriram, D.A new series of indole-isoxazolone hybrids bearing substituted amide, substituted [(1,2,3-triazol-4-yl)methoxy]methyl group or substituted benzylic ether at position-2 of the indole nucleus was synthesised using a facile synthetic route and the molecules were characterised using spectroscopic techniques. The molecules were screened against three human cancer cell lines to evaluate their in vitro cytotoxic property. Most of the trifluoromethyl substituted derivatives exhibited better growth inhibition activity than their methyl substituted analogues. The SIRT1 inhibition activity of two potent molecules (I17 and I18) was investigated and the SIRT1 IC50 values are 35.25 and 37.36 ?M, respectively for I17 and I18. The molecular docking studies with SIRT1 enzyme revealed favourable interactions of the molecule I17 with the amino acids constituting the receptor enzyme. © 2015 Elsevier Ltd. All rights reserved.