Browsing by Author "Srivastava, R."

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D-A conjugated polymers containing substituted thiophene, 1,3,4-oxadiazole and non-conjugation linkers: Synthesis and study of optical and electrochemical properties
(2016) Prashanth, Kumar, K.R.; Udayakumar, D.; Siji, Narendran, N.K.; Chandrasekharan, K.; Srivastava, R.
In this communication, we report synthesis and characterization of new D-A conjugated polymers (P1-P3) consisting of electron-donating (D) 3,4-didodecyloxythiophene, electron-accepting (A) 1,3,4-oxadiazole unit and non-conjugation linkers. The conjugated segment in P1-P3 contains only five aromatic rings resulting in short conjugation length, but has an alternate D-A arrangement which significantly enhances the intramolecular charge transfer (ICT) interaction within the segment. As a result, these polymers exhibited low optical band gap in the range 2.51 2.76 eV. Fluorescence emission studies revealed that the polymer thin films emit intense blue light with emission maxima in the wavelength rage 430 480 nm. All three polymers undergo both oxidation and reduction processes under electrochemical conditions. Further, these polymers (P1 P3) exhibit low-lying HOMO and LUMO levels as a result of D-A structure of the conjugated segment. Polymer light-emitting devices were fabricated using these polymers as emissive layer with a device configuration of ITO/MoO 3/polymer/LiF/Al. The test device based on P2 emitted blue light with a low threshold voltage of 5 V. Z-scan studies reveal that the polymers exhibit a strong optical limiting behavior. The value of the nonlinear absorption coefficient (?) of polymers is of the order 10 ?11m/W which indicates that these materials may be accomplished for fabricating optical limiters. [Figure not available: see fulltext.] 2016, Indian Academy of Sciences.
D-A conjugated polymers containing substituted thiophene, 1,3,4-oxadiazole and non-conjugation linkers: Synthesis and study of optical and electrochemical properties
(Springer India sanjiv.goswami@springer.co.in, 2016) Prashanth Kumar, K.R.; Udayakumar, D.; Siji Narendran, N.K.; Chandrasekharan, K.; Srivastava, R.
In this communication, we report synthesis and characterization of new D-A conjugated polymers (P1-P3) consisting of electron-donating (D) 3,4-didodecyloxythiophene, electron-accepting (A) 1,3,4-oxadiazole unit and non-conjugation linkers. The conjugated segment in P1-P3 contains only five aromatic rings resulting in short conjugation length, but has an alternate D-A arrangement which significantly enhances the intramolecular charge transfer (ICT) interaction within the segment. As a result, these polymers exhibited low optical band gap in the range 2.51–2.76 eV. Fluorescence emission studies revealed that the polymer thin films emit intense blue light with emission maxima in the wavelength rage 430–480 nm. All three polymers undergo both oxidation and reduction processes under electrochemical conditions. Further, these polymers (P1–P3) exhibit low-lying HOMO and LUMO levels as a result of D-A structure of the conjugated segment. Polymer light-emitting devices were fabricated using these polymers as emissive layer with a device configuration of ITO/MoO 3/polymer/LiF/Al. The test device based on P2 emitted blue light with a low threshold voltage of 5 V. Z-scan studies reveal that the polymers exhibit a strong optical limiting behavior. The value of the nonlinear absorption coefficient (?) of polymers is of the order 10 ?11m/W which indicates that these materials may be accomplished for fabricating optical limiters. [Figure not available: see fulltext.] © 2016, Indian Academy of Sciences.
New thiophene-based donor-acceptor conjugated polymers carrying fluorene or cyanovinylene units: Synthesis, characterization, and electroluminescent properties
(2013) Murali, M.G.; Udayakumar, D.; 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.
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.
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, D.; 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.
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.
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.