• Ravi Kumar Kanaparthi

      Articles written in Journal of Chemical Sciences

    • Ratiometric fluorescence signalling of fluoride ions by an amidophthalimide derivative

      Moloy Sarkar Raghavendra Yellampalli Bhaswati Bhattacharya Ravi Kumar Kanaparthi Anunay Samanta

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      Fluorescence behaviour of 4-benzoylamido-N-methylphthalimide (1), designed and developed for selective detection of fluoride ions, is reported. 1 displays $F^-$-induced colour change that allows its detection with the naked eye. The $F^-$ specificity of the sensor system is evident from the fact that unlike $F^-$, other halides do not affect the absorption characteristics of 1. Apart from the colorimetric response, the fluorescence output of 1 is also modulated by $F^-$ in a manner that permits ratiometric fluorescence signalling of $F^-$ as well. It is found that the system can detect $F^-$ in the concentration range of $10^-$ 60 𝜇M. The results of the experiments and theoretical calculations unambiguously suggest that the changes of the electronic absorption and fluorescence behaviour of 1, which have been exploited for signalling purpose, are due to $F^-$-induced deprotonation of the 4-amido moiety of the sensor system.

    • 𝛽-pyrrole substituted porphyrin-pyrene dyads using vinylene spacer: Synthesis, characterization and photophysical properties

      P Silviya Reeta Ravi Kumar Kanaparthi L Giribabu

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      We have designed and synthesized donor-acceptor conjugates having donor pyrene at the pyrrole-𝛽 position of either free-base porphyrin or Zn(II) porphyrin using vinylene spacer. Both the dyads have been completely characterized by elemental analysis,MALDI-MS, UV-Vis., and fluorescence (steady state and timeresolved) spectroscopies as well as cyclic voltammetry. The absorption maxima of both dyads are red-shifted by 8-12 nm. The ground state properties showed that there exist minimum 𝜋-𝜋 interaction between the aromatic subunits of these D-A systems. Quenched emission was observed in both the dyads when excited at 290 nm. The quenched emission explained in terms of intramolecular excitation energy transfer competes with the photo-induced electron transfer reaction in these D-A system.

    • Carbazole-based sensitizers for potential application to dye sensitized solar cells

      Naresh Duvva Ravi Kumar Kanaparthi Jaipal Kandhadi Gabriele Marotta Paolo Salvatori Filippo De Angelis Lingamallu Giribabu

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      Two push-pull molecules employing carbazole and alkyl thiophene (CAR-THIOHX) or carbazole and triphenylamine (CAR-TPA) as donor moieties, with the cyanoacrylic group as the acceptor, have been designed and synthesized by simple organic transformations. Photophysical and electrochemical studies revealed the potential of these two systems in dye sensitized solar cells (DSSC). Under standard irradiation conditions, CAR-TPA and CAR-THIOHX exhibited 2.12 and 1.83% of overall power conversion efficiencies respectively. The moderate photovoltaic efficiency of the sensitizers has been attributed to the poor light absorption of the sensitizers in the visible region. Density functional theory (DFT) calculations have shown a strong intramolecular charge transfer character, with the HOMOs of both the sensitizers exclusively localized on the corresponding donor moieties and LUMOs on the cyanoacrylic acid acceptor. On the other hand, the calculated high dihedral angle between the carbazole donor and the phenyl bridge for these sensitizers impedes the conjugation along the dyes backbone, and thus leads to less extended and intense absorption spectra in the visible region.

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