• T N Misra

      Articles written in Journal of Chemical Sciences

    • Semiconductive properties of biologically important compounds: Gas adsorption effect on vitamin A (alcohol and acetate)

      Biswanath Mallik Alpana Ghosh T N Misra

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      The change in semiconductive properties of vitamin A (alcohol and acetate) after adsorption of various vapours on its crystallite surface has been studied at a constant sample temperature. A rapid enhancement in the semi-conductivity has been observed. The rise in conductivity has been found to be exponential with increasing vapour pressure of the adsorbed gas. It has been suggested that charge transfer (CT) interaction may be responsible for such conductivity change. The adsorption process being efficiently reversible this CT complex is weakly bound.

      The biological implication of these observations is discussed.

    • Two-stage adsorption and desorption processes in some nitroaromatic semiconductor-vapour systems : implications in compensation effect in dark conduction process

      K M Jain Alpana Ghosh T N Misra

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      Adsorption and desorption ofn-hexane, cyclohexane, CCl4, C6H6 ethylacetate, methanol and ethanol vapours on the crystallite surfaces of 2-nitrofluorene and three isomeric nitrobenzoic acid semiconductors have been investigated using electrical conductivity as a probe. Kinetic analysis data show that in all these vapour-semiconductor systems, the adsorption is a two-stage process. Existence of any relationship between the adsorption process and the compensation effect in dark conduction process has been examined. The compensation effect is generally observed in cases where the change in semiconduction activation energy is caused by a two-stage adsorption process.

    • Effect of adsorption of vapours on the electrical conductivity of some nitroaromatic semiconductors: adsorption and desorption kinetics

      Alpana Ghosh K M Jain T N Misra

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      On adsorption of various vapours, the electrical conductivity of nitroaromatic semiconductors 9-nitroanthracene, 1,4-dinitronaphthalene and 1,3,5-trinitrobenzene changes appreciably. This phenomenon has been used as a probe to study the adsorption and desorption processes in these nitroaromatic polycrystals. The adsorption and desorption kinetics have been found to follow the modified Roginsky-Zeldovich relation. Two adsorption processes have been identified. One, a two-stage process, the first of which gives a Lennard-Jones potential energy curve and is followed by a rate-determining transition over a potential energy barrier to the second stage of adsorption forming weakly bound complexes between the vapour molecules and the nitroaromatic crystallites. In the second process, in addition to the two stages of the first process, a third stage with a comparatively deep potential energy surface is reached by activation over a second potential barrier and strongly bound complexes are finally formed.

    • Compensation effect in the electrical conduction process in a series of pyrenyl polyenes

      A Sircar B Mallik T N Misra

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      The semiconductive properties of a series of pyrenyl polyenes of the type R-(CH=CH)n-R, are studied as a function of the adsorption of different amount of a vapour. With regard to the compensation temperature (T0) the compounds are divided into two groups. For compounds which have odd number of double bonds,T0 is infinite and in compounds having even number double bonds,T0 is finite.T0 for II2 is higher while that of II4 is lower than the experimental temperature. DifferentT0 for the compounds having odd or even number of double bonds suggests a physical basis for the compensation rule, which we believe, is related to the molecular and crystalline structure of the compounds

    • Studies onI-V characteristics of dark and photoconduction in methylbixin

      Dilip Ghosh Prabir Pal K M Jain T N Misra

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      Dark and photoconductivities in methylbixin have been studied as a function of applied field and temperature. The results suggest that a single discrete trapping level is involved in charge carrier generation and the dominant trapping level is different for dark and photoconduction. Space charge limited current theory has been used to evaluate various transport parameters. The effective drift mobility is shown to be field dependent.

    • Phonon mediation of solid state photoreaction: Photodimerization ofo-methoxy cinnamic acid

      Urmi Ghosh T N Misra

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      The solid state photodimerization reaction ofo-methoxy cinnamic acid is shown to be mediated by a lattice phonon. The phonon participation, in this case, is through a mode softening and not through strong exciton-phonon coupling as is generally observed. Raman phonon spectroscopy suggests that the reaction is heterogeneous. Infrared spectroscopy has been used to study the internal vibrations of the reactant and the product.

    • Temperature effect on the adsorption and desorption processes in retinoic acid crystals: An electrical conductivity study

      Bani Mitra T N Misra

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      Using electrical conductivity as a probe, the effect of crystal temperature on the process of adsorption and desorption of some chemical vapours on retinoic acid semiconductor has been investigated. It has been observed that a three-stage adsorption process in a sample at low temperature changes over to a two-stage process at higher temperature. Measures of activation energies of adsorption and desorption at different stages have been estimated from kinetic data analysis by using a modified Roginsky-Zeldovich equation.

    • Study of localized levels in proflavine complexes with nucleic acid bases

      D Sarkar T N Misra

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      The semiconduction activation energies of the nucleic acid bases adenine, guanine, thymine and uracil complexes with proflavine dye at various dye concentrations are measured in both the ohmic and the space-charge-limited (SCL) regions. The complexes are found to be nonextrinsic at high dye concentration but approach the extrinsic situation as the dye concentration decreases. From the SCL data analysis various transport parameters are evaluated.

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