Browsing by Author "Safakath, K."

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Large third-order nonlinearity of new ?-conjugated donor-acceptor polymers with substituted thiophene and 1,3,4-oxadiazole moieties
(2012) Sunitha, M.S.; Adhikari, A.V.; Vishnumurthy, K.A.; Safakath, K.; Philip, R.
We present the synthesis of two newly designed, thiophene-based conjugated polymers (P1 and P2) carrying 1,3,4-oxadiazole, 3,4-dinaphthyloxy thiophene, and 3,4-dialkoxy thiophene moieties as potential NLO active materials. Their NLO properties have been investigated both by the Z-scan and degenerate four-wave mixing (DFWM) techniques using 532nm, 7 nanosecond laser pulses. The measured ? and ?(3) values for the polymers are found to be in the range of 1011m/W and 1011esu, respectively. The results indicate that they exhibit good optical-limiting behavior and are promising materials for nonlinear optical applications due to effective two-photon absorption (TPA). 2012 Copyright Taylor and Francis Group, LLC.
Large third-order nonlinearity of new ?-conjugated donor-acceptor polymers with substituted thiophene and 1,3,4-oxadiazole moieties
(2012) Sunitha, M.S.; Vasudeva Adhikari, A.V.; Vishnumurthy, K.A.; Safakath, K.; Philip, R.
We present the synthesis of two newly designed, thiophene-based conjugated polymers (P1 and P2) carrying 1,3,4-oxadiazole, 3,4-dinaphthyloxy thiophene, and 3,4-dialkoxy thiophene moieties as potential NLO active materials. Their NLO properties have been investigated both by the Z-scan and degenerate four-wave mixing (DFWM) techniques using 532nm, 7 nanosecond laser pulses. The measured ? and ?(3) values for the polymers are found to be in the range of 1011m/W and 1011esu, respectively. The results indicate that they exhibit good optical-limiting behavior and are promising materials for nonlinear optical applications due to effective two-photon absorption (TPA). © 2012 Copyright Taylor and Francis Group, LLC.
Synthesis, characterization and third-order nonlinear optical studies of copper complexes containing 1,10-phenanthroline-5,6-dione and triphenylphosphine ligands
(2011) Rudresha, B.J.; Ramachandra, Bhat, B.; Sampath, Kumar, H.C.; Shiva, Kumar, K.I.; Safakath, K.; Philip, R.
This research article describes the synthesis, characterization and third-order nonlinear optical studies of copper(I) complexes [Cu(Br)(N,N?-C12H6N2O2) (PPh3)] and [Cu(I)(N,N?-C12H6N 2O2)(PPh3)] abbreviated as [CuBrLPPh 3] (1) and [CuILPPh3] (2) (L = 1,10-phenanthroline-5,6- dione). Nonlinear optical properties of the complexes are investigated at 532 nm using single beam Z-scan and degenerate four-wave mixing (DFWM) techniques employing nanosecond laser pulses. The complexes show optical limiting behaviour due to "effective" two-photon absorption. The values of the effective two-photon absorption (2PA) coefficients (?), third-order nonlinear susceptibilities (?(3)), and figures of merit (F), are calculated. 2010 Elsevier B.V. All rights reserved.
Synthesis, characterization and third-order nonlinear optical studies of copper complexes containing 1,10-phenanthroline-5,6-dione and triphenylphosphine ligands
(2011) Rudresha, B.J.; Badekai Ramachandra, B.; Sampath Kumar, H.C.; Shivakumar, K.I.; Safakath, K.; Philip, R.
This research article describes the synthesis, characterization and third-order nonlinear optical studies of copper(I) complexes [Cu(Br)(N,N?-C12H6N2O2) (PPh3)] and [Cu(I)(N,N?-C12H6N 2O2)(PPh3)] abbreviated as [CuBrLPPh 3] (1) and [CuILPPh3] (2) (L = 1,10-phenanthroline-5,6- dione). Nonlinear optical properties of the complexes are investigated at 532 nm using single beam Z-scan and degenerate four-wave mixing (DFWM) techniques employing nanosecond laser pulses. The complexes show optical limiting behaviour due to "effective" two-photon absorption. The values of the effective two-photon absorption (2PA) coefficients (?), third-order nonlinear susceptibilities (?(3)), and figures of merit (F), are calculated. © 2010 Elsevier B.V. All rights reserved.
Synthesis, electrochemical and optical studies of new cyanopyridine based conjugated polymers as potential fluorescent materials
(2011) Vishnumurthy, K.A.; Sunitha, M.S.; Safakath, K.; Philip, R.; Adhikari, A.V.
In this communication we describe the design and synthesis of four new conjugated polymers (P1-P4) carrying cyanopyridine in their backbone via Wittig condensation technique. Their structures were well established by FTIR, 1H NMR, elemental analysis and gel permeation chromatographic techniques. They exhibited good thermal stability with the onset decomposition temperature around 300-350 C in nitrogen atmosphere. Further, their electrochemical, linear and third-order non-linear optical properties have been investigated. The polymers showed low electrochemical band gaps in the range of 1.77-1.99 eV and displayed very good fluorescence emission property in various polar solvents. The fluorescence quantum yields of polymers P1-P4 in tetrahydrofuran (THF) were found to be 35, 42, 38 and 34%, respectively. The effective two-photon absorption coefficients (?) for the polymers were determined by Z-Scan technique and were found to be 1.34 10 -11, 1.24 10-11, 3.04 10-11 and 1.85 10-11 m/W for polymers P1-P4, respectively. 2011 Elsevier Ltd. All rights reserved.
Synthesis, electrochemical and optical studies of new cyanopyridine based conjugated polymers as potential fluorescent materials
(Elsevier Ltd, 2011) Vishnumurthy, K.A.; Sunitha, M.S.; Safakath, K.; Philip, R.; Vasudeva Adhikari, A.V.
In this communication we describe the design and synthesis of four new conjugated polymers (P1-P4) carrying cyanopyridine in their backbone via Wittig condensation technique. Their structures were well established by FTIR, 1H NMR, elemental analysis and gel permeation chromatographic techniques. They exhibited good thermal stability with the onset decomposition temperature around 300-350 °C in nitrogen atmosphere. Further, their electrochemical, linear and third-order non-linear optical properties have been investigated. The polymers showed low electrochemical band gaps in the range of 1.77-1.99 eV and displayed very good fluorescence emission property in various polar solvents. The fluorescence quantum yields of polymers P1-P4 in tetrahydrofuran (THF) were found to be 35, 42, 38 and 34%, respectively. The effective two-photon absorption coefficients (?) for the polymers were determined by Z-Scan technique and were found to be 1.34 × 10 -11, 1.24 × 10-11, 3.04 × 10-11 and 1.85 × 10-11 m/W for polymers P1-P4, respectively. © 2011 Elsevier Ltd. All rights reserved.
Thiophene-based donor-acceptor conjugated polymer as potential optoelectronic and photonic material
(2013) Murali, M.G.; Udayakumar, D.; 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.
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.