C. N. R. Rao

Council of Scientific and Industrial Research (CSIR), New Delhi, New Dilli, NCT, India

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Publications (804)2313.27 Total impact

  • Ram Kumar · K. Gopalakrishnan · Irshad Ahmad · C. N. R. Rao ·

  • K Gopalakrishnan · C N R Rao ·

    09/2015; 2(9):095503. DOI:10.1088/2053-1591/2/9/095503
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    Ram Kumar · K. Gopalakrishnan · Irshad Ahmad · C. N. R. Rao ·
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    ABSTRACT: Composites of boron nitride (BN) and carboxylated graphene are prepared for the first time using covalent cross-linking employing the carbodiimide reaction. The BN1–xGx (x ≈ 0.25, 0.5, and 0.75) obtained are characterized using a variety of spectroscopic techniques and thermogravimetric analysis. The composites show composition-dependent electrical resistivity, the resistivity decreasing with increase in graphene content. The composites exhibit microporosity and the x ≈ 0.75 composite especially exhibits satisfactory performance with high stability as an electrode in supercapacitors. The x ≈ 0.75 composite is also found to be a good electrocatalyst for the oxygen reduction reaction in fuel cells.
    Advanced Functional Materials 09/2015; DOI:10.1002/adfm.201502166 · 11.81 Impact Factor

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    ABSTRACT: Electrochemical generation of hydrogen by non‐precious metal electrocatalysts at a lower overpotential is a thrust area of research directed towards sustainable energy. The exorbitant costs associated with Pt based catalysts is the major bottleneck associated with the commercial scale hydrogen generation. Hence strategies for the synthesis of cost effective and stable catalysts is craving its way for prospective 'hydrogen economy'. In this report, we highlight the novel and general strategy to enhance the electrochemical activity of molybdenum disulfide (MoS 2) in the fullerene structure (IF‐). In particular, pristine (undoped) and Rhenium‐doped nanoparticles of MoS 2 with fullerene‐like structure (IF‐MoS 2) were studied and their performance as catalysts for hydoregen evolution reaction (HER) was compared to that of 2H‐MoS 2 particles (platelets). The current density of IF‐MoS 2 is higher by one order of magnitude as compared to few‐layer (FL‐) MoS 2 due to the enhanced density of edge sites. Furthermore, Re‐doping as low as 100 ppm in IF‐MoS 2 decreases the onset potential by 60‐80 mV and increases the activity by 60 times compared to FL‐MoS 2. The combined synergistic effect of Re‐doping and the IF‐structure not only changes the intrinsic nature of MoS 2 but also increases its reactivity. This strategy highlights the potential use of IF‐structure and Re‐doping in electrocatalytic hydrogen evolution using MoS 2 based catalysts.
    Dalton Transactions 08/2015; DOI:10.1039/C5DT02562A · 4.20 Impact Factor
  • Anand Roy · S. R. Lingampalli · Sujoy Saha · C. N. R. Rao ·
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    ABSTRACT: Hydrogen can be generated by visible light irradiation of semiconductor heterostructures of the type ZnO/Pt/CdS and TiO2/Pt/CdS. In order to understand the dependence of hydrogen generation on the properties of the nanoparticles of ZnO and TiO2, we have carried out systematic studies. For this purpose, we have studied photocatalytic hydrogen generation by ZnO(TiO2)/Cd1-xZnxS and ZnO(TiO2)/Pt/Cd1-xZnxS (x = 0.0, 0.2) heterostructures with oxide nanostructures possessing different morphologies and surface areas. In the case of TiO2/Pt/Cd0.8Zn0.2S heterostructures, the highest H2 evolution rate up to1.76 mmol h-1 g -1 were obtained with H2Ti3O7 nanotubes, with the least H2 evolution rate (0.55 mmol h-1 g -1) from TiO2 powder (Degussa P25). In the case of ZnO/Pt/CdS heterostructures, the highest H2 evolution rate (6.88 mmol h-1 g -1) were obtained from ZnO nanorods1, whereas the least H2 evolution rate (2.55 mmol h-1g-1) was obtained from ZnO nanorods3. The photocatalytic activity of heterostructures generally follows the trend in BET surface areas of the oxide nanostructures, with high surface area favoring good hydrogen evolution activity.
    Chemical Physics Letters 08/2015; 637. DOI:10.1016/j.cplett.2015.08.005 · 1.90 Impact Factor
  • C.N.R. Rao · Urmimala Maitra ·

    Annual Review of Materials Research 07/2015; 45(1):29-62. DOI:10.1146/annurev-matsci-070214-021141 · 11.85 Impact Factor
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    ABSTRACT: We report high-pressure Raman-scattering studies on single-crystal ReO 3 up to 26.9 GPa at room temperature, complemented by first-principles density functional calculations to assign the modes and to develop understanding of the subtle features of the low-pressure phase transition. The pressure (P) dependence of phonon frequencies (ω) reveals three phase transitions at 0.6, 3, and 12.5 GPa with characteristic splitting and changes in the slope of ω(P). Our first-principles theoretical analysis confirms the role of the rotational modes of ReO 6 , M 3 , to the lowest pressure structural transition, and shows that the transition from the P m3m to the I m3 structure is a weak first-order transition, originating from the strong anharmonic coupling of the M 3 modes with the acoustic modes (strain).
    Physical Review B 06/2015; 91(22). DOI:10.1103/PhysRevB.91.224308 · 3.74 Impact Factor
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    ABSTRACT: Unlike cation substitution, anion substitution in inorganic materials such as metal oxides and sulfides would be expected to bring about major changes in the electronic structure and properties. In order to explore this important aspect, we have carried out first-principles DFT calculations to determine the effects of substitution of P and Cl on the properties of CdS and ZnS in hexagonal and cubic structures and show that a sub-band of the trivalent phosphorus with strong bonding with the cation appears in the gap just above the valence band, causing a reduction in the gap and enhancement of dielectric properties. Experimentally, it has been possible to substitute P and Cl in hexagonal CdS and ZnS. The doping reduces the band gap significantly as predicted by theory. A similar decrease in the band gap is observed in N and F co-substituted in cubic ZnS. Such anionic substitution helps to improve hydrogen evolution from CdS semiconductor structures and may give rise to other applications as well. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Angewandte Chemie International Edition in English 04/2015; DOI:10.1002/anie.201501532R1 · 13.45 Impact Factor
  • C.N.R. Rao · Kanishka Biswas ·
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    ABSTRACT: Chemical vapor deposition (CVD) is a process commonly used to produce high-purity solid materials. This chapter gives examples of the synthesis of some of the important inorganic materials by CVD. The common gases used for CVD synthesis of SiO2 are silane and oxygen, dichlo-rosilane (SiCl2H2) and nitrous oxide (N2O), or tetraethylorthosilicate (Si(OC2H5)4). Atomic layer deposition (ALD) is a self-limiting (the amount of film material deposited in each reaction cycle is constant), sequential surface chemistry technique that deposits thin films of materials on solid substrates. The chemistry of ALD is similar to that of CVD, except that the reaction in ALD breaks the CVD reaction into two half-reactions, keeping the precursor materials separate. The chapter provides a few examples of important ALD reactions. ALD of Al2O3 is a model system. ALD of Al2O3 is usually performed using trimethylaluminum (TMA) and H2O.
  • C.N.R. Rao · Kanishka Biswas ·
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    ABSTRACT: A solid-state reaction is said to be topochemically controlled when the reactivity is controlled by the crystal structure rather than by the chemical nature of the constituents. The products obtained in many solid-state decompositions are determined by topochemical factors, especially when the reaction occurs within the solid without the separation of a new phase. In topotactic solid-state reactions, the atomic arrangement in the reactant crystal remains largely unaffected during the course of the reaction, except for changes in dimension in one or more directions. Orientational relations between the parent and the product phases are generally found. Many developments in solid-state chemistry owe much to the investigations carried out on MoO3 and WO3 (for example, crystallographic shear planes). Topochemical dehydration has been used for sometime to prepare new metastable solids (for example, the synthesis of Ti2Nb2O9 from HTiNbO5). This strategy has been extended to perovskites. Intercalation reactions of solids involve the insertion of a guest species (ion or molecule) into a solid host lattice without any major rearrangement of the solid structure. A variety of layered structures act as hosts. The general feature of these structures is that the interlayer interactions are weak while the intralayer bonding is strong. Alkali metal intercalation in dichalcogenides is achieved by direct reaction of the elements around 1070 K in sealed tubes. Alkali metal intercalation compounds with dichalcogenides form hydrated phases. Metal phosphorus trisulfides undergo redox intercalation reactions just as the dichalcogenides and also ion exchange reactions. Pillaring is another intercalation reaction that enables synthesis of metastable oxide material. Pillaring refers to intercalation of robust, thermally stable, molecular species that prop the layers apart and convert the two-dimensional interlayer space into micropores of molecular dimensions, similar to the pores in zeolites. Ion exchange in fast-ion conductors such as β-alumina is well known. It can be carried out in aqueous as well as molten salt media conditions. Ion exchange in inorganic solids is a general phenomenon, not restricted to fast-ion conductors alone. Kinetic and thermodynamic aspects of ion exchange in inorganic solids were examined by England. Their results reveal that ion exchange is a phenomenon that occurs even when the diffusion coefficients are as small as ˜10-12cm2/s, at temperatures far below the sintering temperatures of solids. Ion exchange occurs at a considerable rate in stoichiometric solids as well. A variety of inorganic solids have been exchanged with protons to give new phases, some of which exhibit high protonic conduction. Ion exchange chemistry of layered metal chalcogenides is not explored much compared to that of metal oxides. These are by and large limited to alkali ion-containing transition metal dichalcogenides. Use of molten salts as reactive fluxes is a non-topochemical route that enables the synthesis of metastable phases, especially at intermediate temperatures (150 to 500 degrees Celsius) between those employed in the hydrothermal route and the conventional ceramic route. Strong alkaline media, either in the form of solid fluxes or molten (or aqueous) solutions, enable the synthesis of novel oxides. The alkali flux stabilizes higher oxidation states of metals by providing an oxidizing atmosphere. Alkali carbonate fluxes have been traditionally used to prepare transition metal oxides such as LaNiO3 with Ni in the +3 state. A good example of an oxide synthesized in a strongly alkaline medium is the pyrochlore, Pb2(Ru2-xPbx)O7-y, where Pb is in the +4 state. This oxide is a bifunctional electrocatalyst. The procedure for preparation involves bubbling oxygen through a solution of Pb and Ru salts in strong KOH at 320 K. The sol-gel method has provided a very important means of preparing inorganic oxides. It is a wet chemical method and a multistep process involving both chemical and physical processes such as hydrolysis, polymerization, drying and densification. Important features of the sol-gel method are better homogeneity compared to the traditional ceramic method, high purity, lower processing temperature, more uniform phase distribution in multicomponent systems, better size and morphological control, the possibility of preparing new crystalline and non-crystalline materials and, lastly, easy preparation of thin films and coatings. The six important steps in sol-gel synthesis include: hydrolysis, polymerization, gelation, drying, dehydration and densification. The sol-gel technique has been used to prepare sub-micrometer metal oxide powders with a narrow particle size distribution and unique particle shapes. Electrochemical methods have been employed to advantage for the synthesis of many solid materials. Typical materials prepared in this manner are metal borides, carbides, suicides, oxides and sulfides. Vanadate spinels of the formula MV2O4 as well as tungsten bronzes A5WO3 have been prepared by the electrochemical route. Electrochemical oxidation has been employed to prepare oxygen-excess La2CuO4 and other related materials. Thin films of BaTiO3 and lead zirconate titanate have been prepared by cathodic reduction. Intercalation of alkali metals in host solids is readily accomplished electrochemically. In recent years, hydrothermal synthesis has been employed to prepare various inorganic materials such as metal oxides, chalcogenides, metal-organic frameworks, porous materials and nanomaterials. Hydrothermal high-pressure synthesis under closed system conditions has been employed for the preparation of higher-valence metal oxides. Solvothermal synthesis is similar to hydrothermal synthesis but uses organic solvents such as toluene, decalin and octadecene instead of water. Solvothermal reactions have been extensively employed to prepare inorganic nanocrystals. In solvothermal synthesis, the size and shape of nanocrystals are controlled by the concentration of precursors and the reaction temperature. Ionothermal synthesis involves the use of an ionic liquid as the solvent in the synthesis of novel inorganic compounds.
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    Ram Kumar · K. Gopalakrishnan · Irshad Ahmad · C. N. R. Rao ·

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    Sunita Dey · B. S. Naidu · A. Govindaraj · C. N. R. Rao ·
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    ABSTRACT: Perovskite oxides of the composition La1-xCaxMnO3 (LCM) have been investigated for the thermochemical splitting of H2O and CO2 to produce H2 and CO respectively. The study was carried out in comparison with La1-xSrxMnO3, CeO2 and other oxides. The LCM system exhibits superior characteristics in high-temperature evolution of oxygen, and in reducing CO2 to CO and H2O to H2. The best results are found with La0.5Ca0.5MnO3 whose performance is noteworthy compared to that of other oxides including ceria. The orthorhombic structure of LCM seems to be a crucial factor.
    Physical Chemistry Chemical Physics 11/2014; 17(1). DOI:10.1039/C4CP04578E · 4.49 Impact Factor
  • K. Pramoda · C. N. R. Rao · K. Moses ·

    10/2014; DOI:10.1680/nme.14.00021
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    ABSTRACT: The presence of nitrogen heteroatoms within the lattice of reduced graphene oxide sheets induces a remarkable increase in the thermal stability against oxidation by air. This phenomenon is represented by a nitrogen-doped (blue spheres) graphene sheet withstanding a flame. For more details, see the Communication by C. N. R. Rao, G. Tobias et al. on page 11999 ff.
    Chemistry - A European Journal 09/2014; 20(38):12324-12324. DOI:10.1002/chem.201490161 · 5.73 Impact Factor
  • S. R. Lingampalli · Anand Roy · M. Ikram · C. N. R. Rao ·
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    ABSTRACT: ZnO/NiO/Cd1-xZnxS (x= 0.0, 0.2) heterostructures have been prepared by a simple solution-based procedure using ZnO/NiO heterostructures prepared by different methods. We obtain good hydrogen evolution activity only with ZnO/NiO heterostructures and not with Zn1-yNiyO solid solutions. The hydrogen evolution activities of ZnO/NiO/CdS and ZnO/NiO/Cd1-xZnxS are 2.2 and 8.2 mmol/h/g respectively with apparent quantum yields of 2.3 and 14% under visible-light irradiation. These values of activity are comparable or superior to those obtained with ZnO/Pt/ Cd1-xZnxS and ZnO/Au/ Cd1-xZnxS heterostructures. With UV-visible irradiation, the activity found with ZnO/NiO/Cd1-xZnxS is 14-17 mmol/h/g with an apparent quantum yield in the range of 12-15%.
    Chemical Physics Letters 07/2014; 610. DOI:10.1016/j.cplett.2014.07.052 · 1.90 Impact Factor
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    Rana Saha · A. Sundaresan · C. N. R. Rao ·
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    ABSTRACT: A few oxides such as YMnO3, TbMnO3, YMn2O5 and BiFeO3 constituted the small family of well-characterized multiferroics until recently, but this area of research has been enlarged significantly due to the advent of a novel class of oxides exhibiting interesting multiferroic and magnetoelectric properties arising from magnetically induced ferroelectricity. Interestingly, these materials are simple transition metal oxides, most of them possessing the perovskite structure. In this review article, we present the significant features of multiferroic and magnetoelectric ferrites and chromites which owe their ferroelectricity to magnetic interactions. Some of the important systems discussed are BiFeO3 whose properties are affected by magnetic and electric fields, rare-earth orthoferrites LnFeO(3) (Ln = Dy, Gd and Sm) and rare-earth orthochromites LnCrO(3), where exchange-striction plays a significant role. Perovskite oxides of the type Y(A(1-x)B(x))O-3 (A, B = Fe, Cr, Mn) exhibit multiferroic properties, although the existence of these properties in YFeO3 and YCrO3 is in doubt. Such oxides with a non-magnetic rare-earth cation at the A site and two transition metal ions in the B-site permit tuning the transition temperatures by varying the B site ions and their relative proportions or the Ln ion. Multiferroic properties of simple ferrites such as Al(Ga)FeO3 where cation disorder appears to play a role are also discussed. Problems and challenges in this area of research are indicated.
    ChemInform 07/2014; 45(27). DOI:10.1002/chin.201427231
  • S. R. Lingampalli · C. N. R. Rao ·
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    ABSTRACT: The performance of ZnO/Pt/Cd1-yZnyS (y= 0.0, 0.2) heterostructures in generating hydrogen on visible light irradiation is substantially improved if ZnO is co-substituted 10 with N and F, since such anion substitution results in intense visible light absorption and decrease in the band gap.
    Journal of Materials Chemistry A 04/2014; DOI:10.1039/C4TA01445F · 7.44 Impact Factor
  • Achutharao Govindaraj · C.N.R. Rao ·
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    ABSTRACT: Graphene can be doped with boron and nitrogen as well as with other heteroatoms, B2H6 is generally used as the boron source, while NH3 or pyridine is employed as the nitrogen source for doping graphene by chemical vapor deposition and arc-dischrge techniques. Urea as a nitrogen source is also found to be very effective. Substitutional doping of graphene with boron and nitrogen brings about significant changes in their electronic structure and properties. Doping with boron and nitrogen causes marked changes in the Raman spectra of the carbon nanostructures. Such doping not only results in desirable properties but also allows manipulation of properties for specific purposes. In this chapter, we present the synthesis, characterization, and properties of graphene doped with boron, nitrogen, and other elements and also discuss their important applications.
    Functionalization of Graphene, 03/2014: pages 283-358; , ISBN: 9783527335510

Publication Stats

20k Citations
2,313.27 Total Impact Points


  • 2011-2014
    • Council of Scientific and Industrial Research (CSIR), New Delhi
      New Dilli, NCT, India
  • 1992-2014
    • Jawaharlal Nehru Centre for Advanced Scientific Research
      • • International Centre for Materials Science (ICMS)
      • • Chemistry and Physics of Materials Unit
      • • New Chemistry Unit
      Bengalūru, Karnataka, India
  • 1996-2010
    • University of California, Santa Barbara
      • Materials Research Laboratory
      Santa Barbara, California, United States
  • 2008
    • Uppsala University
      • Department of Engineering Sciences
      Uppsala, Uppsala, Sweden
  • 1981-2003
    • Tata Institute of Fundamental Research
      • Department of Condensed Matter Physics and Materials Science
      Mumbai, Maharashtra, India
    • Indian Institute of Science
      • Department of Solid State and Structural Chemistry Unit
      Bengalūru, Karnataka, India
  • 1975-2001
    • University of Oxford
      • Inorganic Chemistry Laboratory
      Oxford, ENG, United Kingdom
  • 1995
    • Government of Karnataka, India
      Bengalūru, Karnataka, India
    • University of Birmingham
      Birmingham, England, United Kingdom
    • University of Wales
      • Department of Chemistry
      Cardiff, Wales, United Kingdom
  • 1994-1995
    • CSIR Structural Engineering Research Centre
      Chennai, Tamil Nadu, India
    • Gakushuin University
      • Department of Physics
      Edo, Tōkyō, Japan
  • 1993
    • University of Toulouse
      Tolosa de Llenguadoc, Midi-Pyrénées, France
  • 1989
    • Bhabha Atomic Research Centre
      Mumbai, Maharashtra, India
  • 1987
    • Indian Institute of Management & Research
      Jeypore, Rajasthan, India
  • 1985
    • University of Cambridge
      • Faculty of Physics and Chemistry
      Cambridge, England, United Kingdom
  • 1983
    • Solid State Scientific Corporation
      Hollis, New Hampshire, United States
  • 1977
    • Uttar Pradesh Textile Technology Institute
      Cawnpore, Uttar Pradesh, India
  • 1966-1976
    • Indian Institute of Technology Kanpur
      • Department of Chemistry
      Cawnpore, Uttar Pradesh, India
  • 1959-1968
    • Purdue University
      • Department of Chemistry
      West Lafayette, Indiana, United States