• C N R Rao

      Articles written in Journal of Chemical Sciences

    • Photoelectron spectroscopic studies of the adsorption of organic molecules with lone pair orbitals on transition metal surfaces

      S Yashonath P K Basu A Srinivasan M S Hedge C N R Rao

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      Ultraviolet and x-ray photoelectron spectroscopy have been employed to investigate the adsorption of methanol, ethanol, diethylether, acetaldehyde, acetone, methyl acetate and methylamine on surfaces of Fe, Ni and Cu. All these molecules adsorb molecularly at low temperatures (≤100 K). Lone pair orbitals of these molecules are stabilized on these metal surfaces (by 0·4–1·0eV) due to molecular chemisorption. The molecules generally undergo transformations as the temperature is raised to 120 K or above. The new species produced seems to depend on the metal surface. Some of the product species identified are methoxy species, formaldehyde and carbon monoxide in the case of methanol and methyl acetate, ethoxy species in the case of ethanol and 2-propanol in the case of acetone.

    • Foreword

      C N R Rao K Madhava Madyastha

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    • Why are certain substances metallic?

      C N R Rao P P Edwards

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      Metallic properties are by no means confined to elemental substances alone. A variety of materials, both inorganic and organic, show metallic properties. Some of these exotic substances exhibit electrical conductivities comparable to those of elemental metals like copper. A large number of systems traverse the transition from the metallic state to the nonmetallic state when there is a change in temperature, pressure or composition. Metal oxides provide a wide range of materials exhibiting metallic behaviour or going through the metal to non-metal (M-NM) transition. Alkali metal-ammonia solutions, with which chemists are all too familiar, probably constitute one of the earliest and most widely studied examples of theM-NM transition. However, a proper recognition of the metallization of ammonia in the context of the variety of solid systems exhibitingM-NM transitions has only been possible recently. Another interesting class of substances is that of expanded metals such as Hg and Cs which become non-metallic when the density is reduced below a critical value. Several organic solids, metal-chain compounds and polymers are not only metallic, but also become superconducting at low temperatures. With such a galaxy of chemical substances exhibiting metallic behaviour, the fundamental, recurring question of vital interest is “what makes a metal?”. In this contribution, we shall examine operational criteria as well as criteria derived from models to answer this question. A related question of equal interest to chemists is “how many atoms are necessary to bring about metallic properties?”.

    • HighTc superconductivity in oxides derived from La1·8Sr0·2CuO4

      P Ganguly C N R Rao

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    • Foreword

      D Balasubramanian C N R Rao

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    • Foreword

      B M Deb C N R Rao

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    • Investigations on C70H30 obtained by the Birch reduction of C70

      A Govindaraj A Rathna J Chandrasekhar C N R Rao

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      Upon Birch reduction, C70 forms C70H30 as a major product. Besides reporting spectroscopic properties, we discuss the possible structures of C70H30 and suggest that the most stable structure is derived by exclusive 1,4-addition to the corannulene units and to the central pentaphenyl belt in C70.

    • Synthesis and characterization of submicron-sized mesoporous aluminosilicate spheres

      Gautam Gundiah M Eswaramoorthy S Neeraj Srinivasan Natarajan C N R Rao

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      Mesoporous aluminosilicate spheres of 0.3–0.4 Μm diameter, with different Si/Al ratios, have been prepared by surfactant templating. Surface area of these materials is in the 510–970 m2 g-1 range and pore diameter in the 15–20 å range.

    • Remarkable photochemical HER activity of semiconducting 2H MoSe2 and MoS2 covalently linked to layers of 2D structures and of the stable metallic 1T phases prepared solvo- or hydro-thermally

      NAVIN KUMAR SINGH AMIT SONI REETENDRA SINGH UTTAM GUPTA K PRAMODA C N R RAO

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      MoS2 and MoSe2 in the stable semiconducting 2H form show negligible photocatalytic activity for the hydrogen evolution reaction (HER). By linking the layers of the dichalcogenide with layers of other 2D materials such as carbon-rich borocarbonitride (BC7N), one can enhance the photochemical HER activitysignificantly. Interestingly, such nanocomposites, MoSe2–MoSe2 and MoSe2–BCN show high photocatalytic activity even though the dichalcogenide itself is in the 2H form. This study shows the important role played by covalent cross-linking of layered compounds. Photocatalytic activity of covalently cross-linked layer of 2H-MoSe2 is higher than that of 2H-MoS2. Unlike the 2H forms, the metallic 1T forms of MoS2 and MoSe2 prepared by lithium intercalation followed by exfoliation, exhibit high photocatalytic HER activity. Unfortunately, materials prepared by lithium intercalation are unstable. The 1T forms of MoSe2 and MoS2 prepared by solvothermal or hydrothermal methods are, however, quite stable and exhibit good photochemical activity for HER. The 1T forms are generally superior to the covalently linked 2H forms. The present study shows how MoSe2 and MoS2 in both 2H and 1T forms can be exploited for photochemical HER activity by appropriate chemical manipulation.

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