Articles written in Journal of Chemical Sciences

    • X-ray photoelectron spectra and Auger studies of the surface oxidation of cobalt

      M S Hegde A Srinivasan K Jagannathan G C Chaturvedi

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      Surface oxidation of Co has been investigated at different temperatures in the 300–600 K range at oxygen exposures upto 106 L by XPES and AES techniques. In the XPES, both the valence band and core level bands have been employed to monitor the oxidation while in the AES, metal Auger intensity ratios as well as O(KLL)/Co(L23M45M45) ratios have been examined. Only CoO is formed on the surface at high oxygen exposures at and above 500 K.

    • Dependence of metal Auger intensity ratios on the effective charge on metal atoms

      S Yashonath M S Hegde

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      Metal Auger line intensity ratios were shown by Rao and others to be directly related to the occupancy of valence states. It is now shown that these intensity ratios are more generally related to the effective charge on the metal atom. The Auger intensity ratios are also directly proportional to valence band intensities of metals. Correlations of the intensity ratios with Auger parameters have also been examined.

    • Design and fabrication of an indigenous molecular beam ultraviolet photoelectron spectrometer

      T Pradeep M S Hegde

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      An ultraviolet photoelectron spectrometer for the study of van der Waals molecules has been designed and fabricated indigenously. The spectrometer consists of an Hel discharge lamp, a molecular beam sample inlet system, an electrostatic lens, a 180° hemispherical electrostatic analyser and a channeltron detector. Performance of the spectrometer is illustrated with an example.

    • High rates of catalytic hydrogen combustion with air over Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ coated cordierite monolith


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      Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ was coated on γ -Al ₂O ₃-coated honeycomb structured cordierite monolith (AHCM) by solution combustion method using dip-dry-heat process. This is a modified conventional method to coat the catalysts on honeycomb structured cordierite monolith (HCM). Formation of Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ on AHCMwas confirmed by XRD. The XPS spectra of Pd(3d) core level confirmed Pd ion in Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ is in the form of +2 state.The surface morphology of coated catalystwas unchanged by long time exposure to hydrogencombustion reaction; i.e., H ₂ +O ₂ recombination reaction which indicated the stability of coating on monolith. Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ showed high rates of H ₂ + O ₂ recombination compared to 2 atom% Pd(metal)/γ -Al ₂O ₃, Ce ₀. ₉₈Pd ₀. ₀ ₂O₂ δ ,Ce ₀. ₉₈Pt ₀. ₀ ₂O₂ δ Ce ₀. ₇₃Zr ₀. ₂₅Pd ₀. ₀ ₂O₂ δ, Ti ₀. ₉₉Pd ₀. ₀ ₁O₂ δ and Ti ₀. ₉₈Pd ₀. ₀ ₂O₂ δ. The activation energy of H ₂ + O ₂ recombination reaction over Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ is 7.8 kcal/mol. The rates of reaction over Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ at 60◦C are in the range between 10 and 20 μmol/g/s. The rate of reaction over Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ increased with increase in the concentration of H ₂. For 50 mL of H ₂, it showed rates of the reaction around 36.45 μmol/g/s at room temperature and 230 μmol/g/s at 60◦C. It was found that the rate of reaction due was lower due to hindering effect by adsorption of other gas molecules on the catalytic site.Finally, we propose a mechanism of hydrogen and oxygen recombination reaction over Ti ₀. ₉₇Pd ₀. ₀3O ₂ δ.

    • Recyclable Pd ionic catalyst coated on cordierite monolith for high TOF Heck coupling reaction


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      Pd2+ ionic catalyst, Ti0.97Pd0.03O1.97 was coated over cordierite monolith by solution combustion method. The catalyst coated on the cordierite is nano-crystalline as seen from XRD studies. Coated catalyst was used for Heck coupling reactions with different substrates of aryl halides and olefins. Thus handling nanocrystalline catalyst powder is avoided by fixing it on a solid catalyst cartridge. Heck coupled products were characterized using 1H NMR, 13C NMR, Mass and FTIR spectroscopy. This catalyst showed high selectivity towards Heck coupling reaction. Turnover frequencies (TOF) for each of the reactions were found to be very high. The catalyst was recycled up to 7 times with total TOF 3017 h -1, which is found to be a new green technique in the Heck coupling reaction

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