C. N. R. Rao

Jawaharlal Nehru Centre for Advanced Scientific Research, Bengalūru, Karnataka, India

Are you C. N. R. Rao?

Claim your profile

Publications (806)2369.3 Total impact

  • Sunita Dey, B S Naidu, C N R Rao
    [Show abstract] [Hide abstract]
    ABSTRACT: Perovskite oxides of the Ln0.5 A0.5 MnO3 (Ln=lanthanide, A=Sr, Ca) family have been investigated for the thermochemical splitting of H2 O and CO2 to produce H2 and CO respectively. The amounts of O2 and CO produced strongly depend on the size of the rare earth ions and alkaline earth ions. The manganite with the smallest rare earth possessing the highest distortion and size disorder as well as the smallest tolerance factor, gives out the maximum amount of O2 , and, hence, the maximum amount of CO. Thus, the best results are found with Y0.5 Sr0.5 MnO3 , which possesses the highest distortion and size disorder. Y0.5 Sr0.5 MnO3 shows remarkable fuel production activity even at the reduction and oxidation temperatures as low as 1200 °C and 900 °C, respectively. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Chemistry - A European Journal 03/2015; DOI:10.1002/chem.201500442 · 5.93 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The recent discovery of non-saturating giant positive magnetoresistance in Td-WTe2 has aroused great interest in this material. We have studied the structural, electronic and vibrational properties of bulk and few-layer Td-WTe2 experimentally and theoretically. Spin-orbit coupling is found to govern the semi-metallic character of Td-WTe2. Its structural link with the metallic 1T form provides an understanding of its structural stability. We observe a metal to insulator transition and a change in the sign of the Seebeck coefficient around 373 K. Lattice vibrations in Td-WTe2 have been analyzed by first principle calculations. Out of the 33 possible zone-center Raman active modes, five distinct Raman bands are observed around 112, 118, 134, 165 and 212 cm-1 in bulk Td-WTe2. Based on symmetry analysis and the calculated Raman tensors, we assign the intense bands at 165 cm-1 and 212 cm-1 to the A_1^' and A_1^" modes respectively. We have examined the effect of temperature and the number of layers on the Raman spectrum. Most of the bands of Td-WTe2 stiffen, and the ratio of the integrated intensities of the A_1^" to A_1^' bands decreases in the few-layer sample, while all the bands soften in both bulk and few-layer samples with increasing temperature.
  • Source
    [Show abstract] [Hide abstract]
    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; DOI:10.1039/C4CP04578E · 4.20 Impact Factor
  • [Show abstract] [Hide abstract]
    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 · 1.99 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Chemical doping of graphene becomes necessary to create a band gap which is useful for various applications. Furthermore, chemical doping of elements like boron and nitrogen in graphene gives rise to useful properties. Since chemically doped graphene is both of academic and technical importance, we have prepared this article on the present status of various aspects of this important class of materials. In doing so, we have covered the recent literature on this subject citing all the major references. Some of the aspects that we have covered are the synthesis of chemically doped graphene followed by properties and applications. The applications discussed relate to gas adsorption, lithium batteries, supercapacitors, oxygen reduction reaction, field emission and photochemical water splitting. Characterization of chemically doped graphene also included. We believe that the article will be useful to all those interested in graphene and related materials and provides the present status of the subject.
    Nano Today 06/2014; 9(3). DOI:10.1016/j.nantod.2014.04.010 · 18.43 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: It is no exaggeration to state that the energy crisis is the most serious challenge that we face today. Among the strategies to gain access to reliable, renewable energy, the use of solar energy has clearly emerged as the most viable option. A promising direction in this context is artificial photosynthesis. In this article, we briefly describe the essential features of artificial photosynthesis in comparison with natural photosynthesis and point out the modest success that we have had in splitting water to produce oxygen and hydrogen, specially the latter.
    Current science 01/2014; 106(4):518-527. · 0.83 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Two sorts of MoS2 : A single-layer, metallic form of MoS2 (1T-MoS2 ) and a nanocomposite of a second form of MoS2 (few-layer 2H-MoS2 ) with heavily nitrogenated reduced graphene oxide (NRGO; N content ca. 15 %) show outstanding performance in the production of H2 under visible-light illumination.
    Angewandte Chemie International Edition 12/2013; 52(49). DOI:10.1002/anie.201306918 · 11.34 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Photocatalytic generation of hydrogen by using the hybrid nanostructures, ZnO/Pt/CdS, ZnO/Pt/Cd1-xZnxS and ZnO/Pt/CdS1-xSex, has been studied under UV-visible and visible irradiation by employing Na2S and Na2SO3 as hole scavengers. Good H2 evolution rates up to 17.4 mmol h-1g-1 and an apparent quantum yield (AQY) of 11.1 % were obtained with ZnO/Pt/CdS under UV-visible irradiation. With the visible irradiation alone, the rate of H2 production was slower. With 20% Zn substitution in place of Cd in CdS, the rate of H2 generation was 31.2 mmol h-1g-1 and 12.5 mmol h-1g-1 respectively with UV-visible and visible irradiations, the corresponding AQY values being 23.1 % and 18%. With 50% substitution of S by Se in CdS, the hydrogen generation was at 19 mmol h-1g-1 and 16 mmol h-1g-1 with UV-visible and visible irradiations respectively, but the AQY values were in the 8-9 % region. Replacing Na2S and Na2SO3 by benzyl alcohol as the scavenger improves the catalytic activity of ZnO/Pt/CdS yielding H2 at the rate of 31.6 mmol h-1g-1 and AQY of 34.5 % under visible irradiation. The results were even more remarkable with ZnO/Pt/Cd0.8Zn0.2S where the rate was 36.5 mmol h-1g-1 and the AQY reached 50.4% with visible irradiation. A noteworthy feature of the present study is that the hybrid nanostructures were prepared by simple solution processing involving sequential addition of reagents to ZnO nanoparticles in methanol medium.
    Energy & Environmental Science 12/2013; 6:3589-3594. DOI:10.1039/C3EE42623H · 15.49 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Nitrogen-doped reduced graphene oxide (RGO) samples with different nitrogen content, prepared by two different methods, as well as nitrogen-doped few-layer graphene have been investigated as supercapacitor electrodes. Two electrode measurements have been carried out both in aqueous (6M KOH) and in ionic liquid media. Nitrogen-doped reduced graphene oxides exhibit satisfactory specific capacitance, the values reaching 126F/g at a scan rate of 10mV/s in aqueous medium. Besides providing supercapacitor characteristics, the study has shown the nitrogen content and surface area to be important factors. High surface-area borocarbonitrides, BxCyNz, prepared by the urea route appear to be excellent supercapacitor electrode materials. Thus, BC4.5N exhibits a specific capacitance of 169F/g at a scan rate of 10mV/s in aqueous medium. In an ionic liquid medium, nitrogen-doped RGO and BC4.5N exhibit specific capacitance values of 258F/g and 240F/g at a scan rate of 5mV/s. The ionic liquid enables a larger operating voltage range of 0.0-2.5V compared to 0.0-1V in aqueous medium.
    Solid State Communications 12/2013; 175-176:43-50. DOI:10.1016/j.ssc.2013.02.005 · 1.70 Impact Factor
  • 11/2013; xxx(xxx):xxx. DOI:10.1088/2053-1591/1/1/015001
  • [Show abstract] [Hide abstract]
    ABSTRACT: Single-walled nanohorns (SWNHs) have been prepared by sub-merged arc discharge of graphite electrodes in liquid nitrogen. The samples were examined by scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. Nitrogen and boron doped SWNHs have been prepared by the sub-merged arc discharge method using melamine and elemental boron as precursors. Intensification of Raman D-band and stiffening of G-band has been observed in the doped samples. The electrical resistance of the SWNHs varies in opposite directions with nitrogen and boron doping. Functionalization of SWNHs through amidation has been carried out for solubilizing them in non-polar solvents. Water-soluble SWNHs have been produced by acid treatment and non-covalent functionalization with a coronene salt. SWNHs have been decorated with nanoparticles of Au, Ag and Pt. Interaction of electron donor (tetrathiafulvalene, TTF) and acceptor molecules (tetracyanoethylene, TCNE) with SWNHs has been investigated by Raman spectroscopy. Progressive softening and stiffening of Raman G-band has been observed respectively with increase in the concentration of TTF and TCNE.
    Journal of Cluster Science 10/2013; xxx(1):xxx-xxx. DOI:10.1007/s10876-013-0652-6 · 1.11 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: TiO2 (anatase) codoped with nitrogen and fluorine, synthesized by a simple solid state route, using urea and ammonium fluoride as sources of nitrogen and fluorine, respectively, as well as by decomposition of (NH4)2TiF6 for comparison, has been characterized by various techniques. XPS analysis shows the composition to be TiO1.7N0.18F0.12 for urea-based method (N, F-TiO2-urea) and TiO1.9N0.04F0.06 for complex decomposition method (N, F-TiO2-complex). Both the materials are defect-free as revealed by photoluminescence spectroscopy. Thus, N, F-TiO2-urea exhibits smaller defect-induced magnetization compared to the nitrogen-doped sample. Cosubstitution of N and F is accompanied with an enhancement of the absorption of light in the visible region giving rise to yellow color and with a band gap of ∼2.2 eV in the case of N, F-TiO2-urea. It exhibits enhanced photocatalytic activity and also significant hydrogen evolution (400 μmol/g) on interaction with visible light in the absence of any cocatalyst, which is much higher compared to N, F-TiO2-complex and N-TiO2. First-principles calculations show significant local distortions on codoping TiO2 with N and F and a lowering of energy by 1.93 eV per N, F pair. With virtual negative and positive charges on nitrogen and fluorine, respectively, the dopants prefer pairwise clustering. Our calculations predict a reduction in the band gap in TiO2 cosubstituted with nitrogen and fluorine. The calculated band structure shows that nitrogen 2p states form a separate subband just above the valence band which is enhanced on incorporation of fluorine. Our calculations also indicate anomalous Born effective charges in N, F-TiO2 and predict enhanced photocatalytic activity on codoping of TiO2 by N and F.
    Inorganic Chemistry 09/2013; 52(18). DOI:10.1021/ic401426q · 4.79 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim of the contribution is to introduce a high performance anode alternative to graphite for lithium-ion batteries (LiBs). A simple process was employed to synthesize uniform graphene-like few-layer tungsten sulfide (WS2) supported on reduced graphene oxide (RGO) through a hydrothermal synthesis route. The WS2–RGO (80:20 and 70:30) composites exhibited good enhanced electrochemical performance and excellent rate capability performance when used as anode materials for lithium-ion batteries. The specific capacity of the WS2–RGO composite delivered a capacity of 400–450 mAh g−1 after 50 cycles when cycled at a current density of 100 mA g−1. At 4000 mA g−1, the composites showed a stable capacity of approximately 180–240 mAh g−1, respectively. The noteworthy electrochemical performance of the composite is not additive, rather it is synergistic in the sense that the electrochemical performance is much superior compared to both WS2 and RGO. As the observed lithiation/delithiation for WS2–RGO is at a voltage≈1.0 V (≈0.1 V for graphite, Li+/Li), the lithium-ion battery with WS2–RGO is expected to possess high interface stability, safety and management of electrical energy is expected to be more efficient and economic.
    Nano Energy 09/2013; 2(5):787-793. DOI:10.1016/j.nanoen.2013.02.001 · 10.21 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Two kinds in a box: The electronic and optical properties of ZnO substituted with nitrogen and fluorine are studied both experimentally and theoretically. The presence of fluorine enhances the incorporation of nitrogen in the lattice. Co-substitution reduces the optical band gap of ZnO significantly and increases the dielectric constant. The long-wavelength visible absorption of N, F-ZnO is reflected in its bright orange color.
    ChemPhysChem 08/2013; 14(12). DOI:10.1002/cphc.201300305 · 3.36 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: BaTiO3, with both nitrogen and fluorine substituted for oxygen, has been prepared and the properties of the doped material with the composition BaTiO2.8N0.1F0.1 have been studied. The color of the sample changes to light green on doping, accompanying a broad visible absorption band with its edge at 2.5 eV. The first-order ferroelectric transition changes to a broad transition on doping along with a decrease in the dielectric constant. We have examined the local structure, electronic structure and polar lattice dynamical properties of N and F co-substituted BaTiO3 using first-principles density functional theory-based calculations and derived the mechanism of the diffuse ferroelectric transition observed here with a broad peak in the temperature-dependent dielectric response. The calculated Born charges clearly reveal a strong disparity in the interaction of N, O and F with Ti: N being the most ferro-active, with a highly anomalous charge, and F being the least active, with an almost nominal charge. This originates from an electronic structure in which the top-most valence band is constituted of the 2p states of N, while the electronic states of F lie deep in the energy band, resulting in a local structure with short covalent Ti-N and long ionic Ti-F bonds. Disorder in these hetero ferro-active anions leads to a relaxor-like diffuse phase transition and a reduction in polarization. Calculations confirm the reduction of 0.65 eV in the bandgap of BaTiO3, which changes from indirect to direct type.
    Journal of Physics Condensed Matter 08/2013; 25(34):345901. DOI:10.1088/0953-8984/25/34/345901 · 2.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Nanoparticles of CdO2 and ZnO2 are shown to oxidize toluene primarily to benzaldehyde in the 160-180 °C range, around which temperature the nanoparticles decompose to give the oxides. The product selectivity and other features of the reaction are explained taking into account the various by products formed in the reaction. These metal peroxides also activate the C-H bonds of cyclohexane. It is possible to bring down the reaction temperature by partially substituting Zn in ZnO2 by Ni.
    ChemPlusChem 08/2013; 78:837-842. DOI:10.1002/cplu.201300114 · 3.24 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Ionothermal synthesis: Ultrathin (~4 nm) few-layer nanostructures of Bi2 Se3 and related chalcogenides have been prepared by green ionothermal synthesis. The ionic liquid acts as an intercalating and stabilizing agent in addition to being an efficient solvent for the synthesis of few-layer Bi2 Se3 . High electrical conductivity and minimal thermal conductivity optimize the thermoelectric properties of few-layer Bi2 Se3 .
    Chemistry - A European Journal 07/2013; 19(28). DOI:10.1002/chem.201300983 · 5.93 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Prompted by the early results on the catalytic activity of LiMn2O4 and related oxides in the photochemical oxidation of water, our detailed study of several manganese oxides has shown that trivalency of Mn is an important factor in determining the catalytic activity. Thus, Mn2O3, LaMnO3, and MgMn2O4 are found to be very good catalysts with turnover frequencies of 5 × 10(-4) s(-1), 4.8 × 10(-4) s(-1), and 0.8 ×10(-4) s(-1), respectively. Among the cobalt oxides, Li2Co2O4 and LaCoO3-especially the latter-exhibit excellent catalytic activity, with the turnover frequencies being 9 × 10(-4) s(-1) and 1.4 × 10(-3) s(-1), respectively. The common feature among the catalytic Mn and Co oxides is not only that Mn and Co are in the trivalent state, but Co(3+) in the Co oxides is in the intermediate t2g(5)eg(1) state whereas Mn(3+) is in the t2g(3)eg(1) state. The presence of the eg(1) electron in these Mn and Co oxides is considered to play a crucial role in the photocatalytic properties of the oxides.
    Proceedings of the National Academy of Sciences 07/2013; DOI:10.1073/pnas.1310703110 · 9.81 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Heavily nitrogenated graphene oxide containing 18 wt% nitrogen, prepared by microwave synthesis with urea as the nitrogen source, shows outstanding performance as a supercapacitor electrode material, with the specific capacitance going up to 461 F g−1.
    06/2013; 1(26):7563-7565. DOI:10.1039/C3TA11385J
  • [Show abstract] [Hide abstract]
    ABSTRACT: Soak it up: A boron-imidazolate metal-organic framework composed of a mixed ligand system acts as a precursor for the synthesis of a high-surface-area borocarbonitride (BC4 N) with remarkable H2 and CO2 storage properties. Furthermore, BC4 N has been exploited for the stabilisation of metal (Au and Pd) nanoparticles.
    Chemistry - A European Journal 05/2013; 19(22). DOI:10.1002/chem.201300054 · 5.93 Impact Factor

Publication Stats

18k Citations
2,369.30 Total Impact Points

Institutions

  • 1992–2015
    • Jawaharlal Nehru Centre for Advanced Scientific Research
      • • New Chemistry Unit
      • • Chemistry and Physics of Materials Unit
      • • International Centre for Materials Science (ICMS)
      Bengalūru, Karnataka, India
  • 2002–2013
    • Government of Karnataka, India
      Bengalūru, Karnataka, India
  • 2011
    • Council of Scientific and Industrial Research (CSIR), New Delhi
      New Dilli, NCT, India
  • 1998–2010
    • University of California, Santa Barbara
      • Materials Research Laboratory
      Santa Barbara, California, United States
  • 2008
    • Uppsala University
      • Department of Engineering Sciences
      Uppsala, Uppsala, Sweden
  • 1984–2008
    • University of Cambridge
      • • Department of Chemistry
      • • Faculty of Physics and Chemistry
      Cambridge, England, United Kingdom
  • 1989–2005
    • Bhabha Atomic Research Centre
      • Chemistry Division
      Mumbai, Mahārāshtra, India
  • 1980–2003
    • Tata Institute of Fundamental Research
      • Department of Condensed Matter Physics and Materials Science
      Mumbai, Maharashtra, India
  • 2000
    • National Physical Laboratory - India
      Old Delhi, NCT, India
  • 1999
    • The Ohio State University
      • Department of Chemistry and Biochemistry
      Columbus, Ohio, United States
  • 1995
    • University of Wales
      • Department of Chemistry
      Cardiff, Wales, United Kingdom
  • 1993
    • University of Toulouse
      Tolosa de Llenguadoc, Midi-Pyrénées, France
  • 1983
    • Solid State Scientific Corporation
      Hollis, New Hampshire, United States
  • 1966–1978
    • Indian Institute of Technology Kanpur
      • Department of Chemistry
      Cawnpore, Uttar Pradesh, India
  • 1976
    • University of Salford
      Salford, England, United Kingdom
  • 1975
    • University of Oxford
      • Inorganic Chemistry Laboratory
      Oxford, ENG, United Kingdom
  • 1972–1973
    • Indian Institute of Technology Ropar
      • Department of Chemistry
      Rūpar, Punjab, India
  • 1959–1971
    • Purdue University
      • Department of Chemistry
      West Lafayette, IN, United States