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S. Radhakrishna

Bio: S. Radhakrishna is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Two-photon absorption & Fermi contact interaction. The author has an hindex of 3, co-authored 6 publications receiving 54 citations.

Papers
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TL;DR: In this paper, the EPR spectra of VO2+ doped KHC2O4 crystals revealed two sites with intensity ratio 2:1 and indicated two nearly parallel orientations of the ion in the lattice.

24 citations

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TL;DR: In this article, the ESR spectra of the VO2+ ion doped in oxalate, tartrate and cadmium crystals taken in the polycrystalline form are analyzed.

20 citations

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TL;DR: In this article, Ionic thermocurrents are observed in impurity doped cesium bromide crystals impurity-vacancy complex and their activation energy is compared with the activation energy values determined from other transport experiments.

9 citations

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TL;DR: In this article, the optical absorption spectrum of the Cu 2+ ion in Cd(NH 4 2 (SO 4 ) 2 ·6H 2 O (CdASH) and CdK 2(SO 4 2 · 6H 2O (cdKSH) single crystals showed four absorption bands at 300 and 80 K and has been analyzed assuming tetragonal site symmetry for the ion with spin-orbit coupling.

3 citations

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TL;DR: In this paper, the optical absorption spectra of Cd(NH 4 ) 2 (SO 4 2 ·6H 2 O doped Ni 2+ at 300 and 80 K was recorded and the transitions were assigned.

1 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the FTIR spectra of the used catalysts are altogether different from those of the fresh catalysts suggesting that the active phase has been drastically modified during the course of the reaction.
Abstract: In an earlier communication the ammoxidation activity of V2O5/TiO2 catalysts with V2O5 loadings in the range 0.4–9.9 mol% was correlated to the average oxidation number of vanadium in the catalysts. In the present work, these catalysts were characterised by SEM, FTIR, ESR, DTA techniques and chemisorption of NH3 and O2. The scanning electron micrographs of the catalysts indicate that deposition of vanadium is taking place inside the mesopores of titania (anatase) up to 3.4 mol% V2O5 corresponding to a monolayer coverage. Beyond this loading neddle-like and bulk structures of vanadia appear probably on the external surface of the catalysts. The bands at 1010–1020 cm−1 appearing in the FTIR spectra of fresh catalysts are characteristic of highly dispersed monomeric VOx units and two-dimensional structures. The FTIR spectra of the used catalysts are altogether different from those of the fresh catalysts suggesting that the active phase has been drastically modified during the course of the reaction. The ESR spectrum of 0.4 mol% V2O5 shows an eightfold well resolved hyperfine structure indicating that V4+ is in diluted conditions on anatase surface. As V2O5 content increases the hyperfine structure of ESR spectrum gets progressively smeared out due to strong coupling between V4+ dipoles. The results indicate that vanadium is in a highly dispersed distorted octahedral or square pyramidal geometry at 3.4 mol% corresponding to a monolayer coverage. The DTA curves contain endothermic peaks at 100–150°C and 630–675°C corresponding to desorption of adsorbed water and melting of vanadia particles and loss of oxygen from vanadia. Chemisorption of NH3 and O2 is observed to exhibit maximum at the monolayer V2O5 loading just as the ammoxidation activity of the catalysts.

50 citations

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TL;DR: Electronic and magnetic data proposed the octahedral structure for all complexes under investigation, except VO(2+), is a square-pyramidal geometry and TG analysis for most complexes supports the absence of solvent molecules in or out the coordination sphere through the high thermal stability observed on the thermal curves for the investigated complexes.

46 citations

Journal ArticleDOI
TL;DR: In this paper, the chelating behavior of 2,6-diacetylpyridine bis(2-aminobenzoylhydrazone) (H2dapa) towards manganese(II), cadmium(II) and oxovanadium(IV) ions has been studied by elemental analyses, conductance measurements, magnetic properties and spectral (IR, 1H NMR, UV-Vis and EPR) studies.

36 citations

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TL;DR: In this article, a new oxovanadium(IV)-cucurbit[6]uril complex is presented, which combines the catalytic properties of the metal ion with the size-excluding properties of macrocycle cavity.

34 citations

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TL;DR: It is found from the EPR analysis that the Na(+) ions are replaced with the substitutional magnetically inequivalent VO(2+) ions, and the powder spectrum also clearly indicates four different VO( 2+) complexes, confirming the single crystal analysis.

33 citations