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Papers by Jayabharathi Jayaraman

Research paper thumbnail of Organic-inorganic hybrids based on phenanthrene-functionalized gold nanoparticles for OLEDs

Journal of Physical Organic Chemistry, 2017

The electroluminescence intensity of the phenanthrene-functionalized gold nanoparticles, PMPT-Au ... more The electroluminescence intensity of the phenanthrene-functionalized gold nanoparticles, PMPT-Au nanoparticles/CPB: Ir(PIA) 2 (acac) film, was increased by 4.9 times compared with control device, CPB: Ir(PIA) 2 (acac) due to coupling between the excitons of emissive layer and localized surface plasmonic resonance of PMPT-Au NPs. The maximum luminous efficiencies of devices II to IV with PMPT-Au NPs were 39.2 cd A −1 (11.8 V), 40.1 cd A −1 (10.5 V), and 43.1 cd A −1 (9.0 V), respectively. The increment of current efficiency with PMPT-Au NP coated devices was strongly related to the energy transfer between the radiated light generated from CBP: Ir(PIA) 2 (acac) emissive layer and localized surface plasmonic resonance excited by PMPT-Au NP layer.

Research paper thumbnail of Nondoped blue fluorescent OLED based on cyanophenanthrimidazole-styryl-triphenylamine/carbazole materials

Journal of Physical Organic Chemistry, 2017

New 2-(4′-9H-carbazole-9-yl)-styryl-1H-phenathro[9,10-d]imidazole-1-yl)benzonitrile (SPICN-Cz) an... more New 2-(4′-9H-carbazole-9-yl)-styryl-1H-phenathro[9,10-d]imidazole-1-yl)benzonitrile (SPICN-Cz) and 4-(2-(4-(diphenylamino)phenyl-styryl-1H-phenathro[9,10-d]imidazole-1-yl)benzonitrile (SPICN-TPA) have been synthesised, and their photophysical, electrochemical, and electroluminescent properties were analysed in comparison with their cyano-free parent compounds, SPI-Cz, and SPI-TPA. Solvatochromic effects show the transformation of an excited state character from locally excited (LE) state to charge transfer (CT) state. Using time-dependent density functional theory calculation, the excited state properties of these donor-acceptor blue emissive materials have been analysed. Their excited state properties have been tuned by replacing the strong donor triphenylamine to weak donor carbazole to achieve the combination of high photoluminance efficiency locally excited (LE) component and high exciton-utilizing CT component in one excited state. Hybridization processes between LE and CT components of SPICN-Cz and SPICN-TPA in the emissive state have been discussed. The nondoped organic light emitting diode device based on SPICN-Cz exhibit better electroluminescent performances than those of SPICN-TPA-based device: high external quantum efficiency of 2.58 %, current efficiency of 2.90 cd A-1 , and power efficiency of 2.26 lm W-1 with Commission Internationale de l'Éclairage (CIE) coordinates of (0.15, 0.12). The excited state modulation and the composition of LE and CT states in the donor-acceptor system could be useful to design low-cost, high-efficiency fluorescent organic light emitting diode materials.

Research paper thumbnail of A mechanistic investigation of the oxidation of N,α-diphenylnitrones by dichloramine-T in aqueous acetonitrile medium - a non-linear Hammett plot

Journal of the Serbian Chemical Society, 2009

The kinetics of oxidation of a number of meta- and para-substituted N,?-diphenylnitrones (nitrone... more The kinetics of oxidation of a number of meta- and para-substituted N,?-diphenylnitrones (nitrone) by dichloramine-T (DCT) was investigated in the presence of alkali in aqueous acetonitrile medium. The order with respect to DCT was one and to OH- an inverse fractional order. The reaction was first order with respect to nitrone. Both electron releasing and withdrawing substituents suppress the reaction rate. The observed rate constant for the substituents were plotted against the Hammett constant, ?, and a non-linear concave downward curve was obtained. The electron withdrawing substituents fall on one side of the curve, having a negative ? value and the electron releasing substituents fall on the other side, with a positive ? value. A mechanism is proposed and the derived rate law is in conformity with the observed results.

Research paper thumbnail of Sensing Nanoparticulate ZnO with Benzimidazole Derivative by Fluorescence

Key Engineering Materials, 2013

A sensitive benzimidazole derivative fluorescent sensor for nanoparticulate ZnO has been designed... more A sensitive benzimidazole derivative fluorescent sensor for nanoparticulate ZnO has been designed and synthesized. The nanocrystalline ZnO, Ag doped ZnO and Cu doped ZnO have been synthesised by sol-gel method and characterized by powder X-ray diffraction, scanning electron microscopy (SEM) and UV-visible diffuse reflectance, photoluminescence and electrochemical impedance spectroscopies. The synthesized sensor emits fluorescence at 360 nm and this fluorescence is selectively enhanced by nanocrystalline ZnO. This technique is sensitive to detect and estimate ZnO at micro molar level. Impurities such as Ag and Cu do not hamper the sensitivity of this technique significantly. Keywords: Sensor, SEM, EDX, Impedance, Fluorescence

Research paper thumbnail of FT-Raman, FT-IR spectral and DFT studies on (E)-1-4-nitrobenzylidenethiocarbonohydrazide

Quantum mechanical calculation of optimized parameters, vibrational wavenumbers and energies of (... more Quantum mechanical calculation of optimized parameters, vibrational wavenumbers and energies of (E)-1-4-nitrobenzylidenethiocarbonohydrazide ((E)-1-4-NBTCH) was carried out using Hatree Fock (HF) with 6-31G(d,p), 6-311G(d,p) basis sets and density functional theory (DFT) with 6-31G(d,p) basis set. The optimized geometrical parameters obtained by HF and DFT are in better agreement with analogues single XRD data. The vibrational wavenumbers were calculated and the complete assignments were performed on the basis of total energy distribution (TED), calculated with scaled quantum mechanical (SQM) method. The electrical dipole moment (μ) and first hyperpolarizability (β(0)) values have been computed using ab initio and DFT quantum mechanical calculation. The calculated results (β(0)) show that the title molecule might have nonlinear optical (NLO) behaviour. The total energy, dipole moment and rotational constant are reported for the title molecule. The HOMO-LUMO energies were calculated and natural bonding orbital (NBO) analysis has also been carried out.

Research paper thumbnail of Organic-inorganic hybrids based on phenanthrene-functionalized gold nanoparticles for OLEDs

Journal of Physical Organic Chemistry, 2017

The electroluminescence intensity of the phenanthrene-functionalized gold nanoparticles, PMPT-Au ... more The electroluminescence intensity of the phenanthrene-functionalized gold nanoparticles, PMPT-Au nanoparticles/CPB: Ir(PIA) 2 (acac) film, was increased by 4.9 times compared with control device, CPB: Ir(PIA) 2 (acac) due to coupling between the excitons of emissive layer and localized surface plasmonic resonance of PMPT-Au NPs. The maximum luminous efficiencies of devices II to IV with PMPT-Au NPs were 39.2 cd A −1 (11.8 V), 40.1 cd A −1 (10.5 V), and 43.1 cd A −1 (9.0 V), respectively. The increment of current efficiency with PMPT-Au NP coated devices was strongly related to the energy transfer between the radiated light generated from CBP: Ir(PIA) 2 (acac) emissive layer and localized surface plasmonic resonance excited by PMPT-Au NP layer.

Research paper thumbnail of Nondoped blue fluorescent OLED based on cyanophenanthrimidazole-styryl-triphenylamine/carbazole materials

Journal of Physical Organic Chemistry, 2017

New 2-(4′-9H-carbazole-9-yl)-styryl-1H-phenathro[9,10-d]imidazole-1-yl)benzonitrile (SPICN-Cz) an... more New 2-(4′-9H-carbazole-9-yl)-styryl-1H-phenathro[9,10-d]imidazole-1-yl)benzonitrile (SPICN-Cz) and 4-(2-(4-(diphenylamino)phenyl-styryl-1H-phenathro[9,10-d]imidazole-1-yl)benzonitrile (SPICN-TPA) have been synthesised, and their photophysical, electrochemical, and electroluminescent properties were analysed in comparison with their cyano-free parent compounds, SPI-Cz, and SPI-TPA. Solvatochromic effects show the transformation of an excited state character from locally excited (LE) state to charge transfer (CT) state. Using time-dependent density functional theory calculation, the excited state properties of these donor-acceptor blue emissive materials have been analysed. Their excited state properties have been tuned by replacing the strong donor triphenylamine to weak donor carbazole to achieve the combination of high photoluminance efficiency locally excited (LE) component and high exciton-utilizing CT component in one excited state. Hybridization processes between LE and CT components of SPICN-Cz and SPICN-TPA in the emissive state have been discussed. The nondoped organic light emitting diode device based on SPICN-Cz exhibit better electroluminescent performances than those of SPICN-TPA-based device: high external quantum efficiency of 2.58 %, current efficiency of 2.90 cd A-1 , and power efficiency of 2.26 lm W-1 with Commission Internationale de l'Éclairage (CIE) coordinates of (0.15, 0.12). The excited state modulation and the composition of LE and CT states in the donor-acceptor system could be useful to design low-cost, high-efficiency fluorescent organic light emitting diode materials.

Research paper thumbnail of A mechanistic investigation of the oxidation of N,α-diphenylnitrones by dichloramine-T in aqueous acetonitrile medium - a non-linear Hammett plot

Journal of the Serbian Chemical Society, 2009

The kinetics of oxidation of a number of meta- and para-substituted N,?-diphenylnitrones (nitrone... more The kinetics of oxidation of a number of meta- and para-substituted N,?-diphenylnitrones (nitrone) by dichloramine-T (DCT) was investigated in the presence of alkali in aqueous acetonitrile medium. The order with respect to DCT was one and to OH- an inverse fractional order. The reaction was first order with respect to nitrone. Both electron releasing and withdrawing substituents suppress the reaction rate. The observed rate constant for the substituents were plotted against the Hammett constant, ?, and a non-linear concave downward curve was obtained. The electron withdrawing substituents fall on one side of the curve, having a negative ? value and the electron releasing substituents fall on the other side, with a positive ? value. A mechanism is proposed and the derived rate law is in conformity with the observed results.

Research paper thumbnail of Sensing Nanoparticulate ZnO with Benzimidazole Derivative by Fluorescence

Key Engineering Materials, 2013

A sensitive benzimidazole derivative fluorescent sensor for nanoparticulate ZnO has been designed... more A sensitive benzimidazole derivative fluorescent sensor for nanoparticulate ZnO has been designed and synthesized. The nanocrystalline ZnO, Ag doped ZnO and Cu doped ZnO have been synthesised by sol-gel method and characterized by powder X-ray diffraction, scanning electron microscopy (SEM) and UV-visible diffuse reflectance, photoluminescence and electrochemical impedance spectroscopies. The synthesized sensor emits fluorescence at 360 nm and this fluorescence is selectively enhanced by nanocrystalline ZnO. This technique is sensitive to detect and estimate ZnO at micro molar level. Impurities such as Ag and Cu do not hamper the sensitivity of this technique significantly. Keywords: Sensor, SEM, EDX, Impedance, Fluorescence

Research paper thumbnail of FT-Raman, FT-IR spectral and DFT studies on (E)-1-4-nitrobenzylidenethiocarbonohydrazide

Quantum mechanical calculation of optimized parameters, vibrational wavenumbers and energies of (... more Quantum mechanical calculation of optimized parameters, vibrational wavenumbers and energies of (E)-1-4-nitrobenzylidenethiocarbonohydrazide ((E)-1-4-NBTCH) was carried out using Hatree Fock (HF) with 6-31G(d,p), 6-311G(d,p) basis sets and density functional theory (DFT) with 6-31G(d,p) basis set. The optimized geometrical parameters obtained by HF and DFT are in better agreement with analogues single XRD data. The vibrational wavenumbers were calculated and the complete assignments were performed on the basis of total energy distribution (TED), calculated with scaled quantum mechanical (SQM) method. The electrical dipole moment (μ) and first hyperpolarizability (β(0)) values have been computed using ab initio and DFT quantum mechanical calculation. The calculated results (β(0)) show that the title molecule might have nonlinear optical (NLO) behaviour. The total energy, dipole moment and rotational constant are reported for the title molecule. The HOMO-LUMO energies were calculated and natural bonding orbital (NBO) analysis has also been carried out.