Department of Chemistry

Indian Institute of Technology Hyderabad (IITH) is a premier institute of science and technology established in 2008. IITH has been consistently ranked in the&nbsp;<a href="https://iith.ac.in/reports/" rel="noopener noreferrer">top 10 institutes</a>&nbsp;in India for Engineering&nbsp;<a href="https://www.nirfindia.org/2021/EngineeringRanking.html" rel="noopener noreferrer" target="_blank">according to NIRF</a>&nbsp;making it one of the most coveted schools for science and technology in the country.

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IIT Hyderabad

Sodium phosphate glass systems with AgCl as dopant (0 and 15 mol%) have been synthesized by melt-quenching technique. The glasses in bulk form were characterized by X-ray diffraction, FT-IR spectroscopy and their thermal and electrical properties were investigated. These glasses were deposited on glass substrates by thermal evaporation method in thin film form and annealed at 600 °C. The influence of deposition in thin film form and annealing on structure and optical properties (transmittance, absorbance and optical gap) have showed that both doped and undoped as-deposited glass films have a porous, granular structure and considerable grain coarsening and densification occur upon annealing at 600 °C. The optical transmittance of the film is found to decrease in visible region as a function of annealing and doping. The annealed 15 mol% doped film shows a prominent absorbance peak at 430 nm, which is ascribed to Ag+(5s) ← O(n) electronic transitions. © 2010 Elsevier B.V. All rights reserved.

World University root node

Optical Materials

Nanostructural features and optical properties of Na2O-P2O5-AgCl thin films

The structures of the binary complexes between phenylacetylene and several tertiary amines viz., triethylamine, 1-ethylpiperidine, 1-ethylpiperazine, 1-azabicyclo[2.2.2]octane, and 1,4-diazabicyclo[2.2.2]octane were inferred using infrared-optical double resonance spectroscopy. The IR spectra in the acetylenic C-H stretching region clearly rule out the formation of electrostatic dominated C-H⋯N hydrogen bonded complexes. The IR spectra also point to the fact that all the five tertiary amines interact with the extended π electron density of the phenylacetylene moiety, leading to the formation of multidentate C-H⋯π hydrogen bonded complexes. Additionally a very weak electrostatic C-H⋯N hydrogen bond enhances the stability of the complex marginally. The multidentate C-H⋯π hydrogen bonded complexes are stabilized by a substantial contribution from the dispersion energy. © 2010 the Owner Societies.

Fulltext

Physical Chemistry Chemical Physics

Binary complexes of tertiary amines with phenylacetylene. Dispersion wins over electrostatics

Oxidative decomposition of a model volatile organic compound (isopropanol, IP) has been carried out in a catalytic dielectric barrier discharge (DBD) reactor, where modified sintered metal fiber (SMF) filter was used as the inner electrode. The SMF was modified with Mn and Co oxides by impregnation, followed by calcination and the performance of the DBD reactor was tested for the oxidation of IP in the specific input energy range 160-720J/l by varying the high voltage and frequency. It has been observed that SMF modification by MnOx and CoOx not only improved the conversion of isopropanol, but also increased the selectivity towards total oxidation. MnOx modification showed better performance than CoOx, which may be attributed to the formation of atomic oxygen by in situ decomposition of ozone. It has been demonstrated that with MnOx/SMF it is possible to completely oxidize 100ppm of isopropanol at SIE&lt;200J/l. © 2010 Elsevier B.V.

Chemical Engineering Journal

Catalytic nonthermal plasma reactor for the abatement of low concentrations of isopropanol

A non-thermal plasma rector with a catalytic electrode made of sintered metal fibres (SMFs) was tested for the oxidative decomposition of a model VOC toluene. The input energy was varied in the range 160-295J/l by varying the applied voltage between 12.5 and 22.5kV at 200Hz. Influence of various parameters like toluene concentration, SMF modification by Mn and Co oxides, input energy and ozone formation was studied. It has been observed that plasma catalytic approach is very effective for total oxidation of toluene at low input energy, especially at toluene concentration ≤250ppm and SMF modification by transition metal oxides increased the performance of the reactor significantly. MnOx modification appears to be a better choice compared to CoOx, which may be attributed to the in situ decomposition of ozone leading to the formation of more reactive oxidants like atomic oxygen. © 2010 Elsevier B.V.

Catalytic non-thermal plasma reactor for abatement of toluene

We studied the electrochemical behavior of aluminum electrodes in solutions comprising ethylene carbonate (EC)-dimethyl carbonate (DMC) and lithium salts: lithium hexafluorophospate (LiPF6), lithium perchlorate (LiClO 4), or lithium bis(oxalato)borate (LiBOB). Under anodic polarization within the potential range of 3.00-4.00 V in these solutions, aluminum electrodes demonstrate a stable behavior due to their passivation by surface films. Aluminum electrodes passivate in EC-DMC/ LiPF6 and EC-DMC/LiBOB solutions both at 30 and 60°C, whereas these electrodes remain active and corrode in EC-DMC/ LiClO4 solutions. LiBOB may decompose at anodic potentials, thus forming passive films comprising B2 O 3 and metal-oxalate species on the aluminum electrodes polarized to 4.50-5.30 V. Li2 CO3, LiF and AlPO4, and LiCl species were also detected on the electrodes anodically polarized in LiBOB-, LiPF6 -, and LiClO4 -containing solutions, respectively. At some conditions, current oscillations can be developed on aluminum electrodes upon their polarization at constant potentials. These oscillations may relate to the successive formation and dissolution of the passivating surface films formed on electrodes. The development of F2 P (O) O- species due to the polarization of aluminum electrodes in EC-DMC/ LiPF6 solutions was confirmed by solution NMR studies. © 2010 The Electrochemical Society.

Journal of the Electrochemical Society

On the electrochemical behavior of aluminum electrodes in nonaqueous electrolyte solutions of lithium salts

We report temperature-dependent Raman spectra of CeFeAsO 0.9F0.1 from 4 to 300K in the spectral range of 60-1800cm- 1 and interpret them using estimates of phonon frequencies obtained from first-principles density functional calculations. We find evidence for strong coupling between the phonons and crystal field excitations; in particular the Ce3 + crystal field excitation at 432cm - 1 couples strongly with the Eg oxygen vibration at 389cm- 1. Below the superconducting transition temperature, the phonon mode near 280cm- 1 shows softening, signaling its coupling with the superconducting gap. The ratio of the superconducting gap to T c, thus estimated to be ∼ 10, suggests CeFeAsO 0.9F0.1 to be a strong coupling superconductor. In addition, two high frequency modes observed at 1342 and 1600cm- 1 are attributed to electronic Raman scattering from the (x2-y 2) to xz /yz d-orbitals of Fe. © 2010 IOP Publishing Ltd.

Journal of Physics Condensed Matter

Temperature-dependent Raman study of a CeFeAsO0.9F0.1 superconductor: Crystal field excitations, phonons and their coupling

(Chemical equation presented) A borane-borohydride and a boranemethyl zinc complex were synthesized by different synthetic pathways. In both compounds the borane molecule is κ1-coordinated to the zinc atom (see figure). © 2010 Wiley-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Chemistry - A European Journal

Unprecedented zinc-borane complexes

We successfully prepared and characterized a wide variety of group 3 metal complexes containing a dianionic or monoanionic glyoxal-based N,N′-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene (DAD) ligand using a salt metathesis reaction of group 3 metal trichlorides with the dipotassium salt of the DAD ligand or a direct reduction of the DAD ligand with 1:1 mixture of group 3 metal powders and group 3 metal halides. The DAD ligand coordinated to group 3 metal in a σ2-enediamide manner for dimeric complexes of yttrium, ytterbium, and europium complexes, whereas σ2,π-enediamide coordination was observed for the lanthanum complex, due to the different ionic radii of the metal atoms. The reaction of the dipotassium salt of the DAD ligand and ScCl3(thf)3 gave a monomeric scandium complex with the monoanionic DAD ligand. © 2010 American Chemical Society.

Organometallics

Salt metathesis and direct reduction reactions leading to group 3 metal complexes with a N, N ′-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene ligand and their solid-state structures

The effect of yttrium substitution at the lanthanum site on the superconducting properties of La1-xYxO0.9F0.1FeAs ('x' = 0, 0.10, 0.20, 0.30, 0.50 and 0.60) oxypnictides has been studied. Powder X-ray diffraction studies confirm single phases till x = 0.1 beyond which minor amount of Y2O3 is observed. The temperature dependence of resistivity measurements confirm the superconducting transition temperature (Tc) of 34.8 (±0.05) K and corresponding Meissner transition at 34.3 K in the 'x' = 0.3 composition which is higher than that reported for the parent phase (LaO0.9F0.1FeAs (Tc = 28 K)). Further increase in the concentration of yttrium leads to broadening and suppression of the superconducting transition. The value of Hc2 at zero temperature is estimated to be about 60.5 T. The Seebeck coefficient (S) shows a negative sign indicating that the major contribution to the conductivity is by electrons. The Hall coefficient (RH) also remains negative throughout the temperature range supporting the thermopower results. The lattice parameters (a and c) decreases and the charge-carrier density increases with yttrium doping. © 2010 Elsevier B.V. All rights reserved.

Physica C: Superconductivity and its Applications

Yttrium doped La1-xYxO0.9F0.1FeAs superconductors: Hall and thermopower studies

This communication explores the effect of varying substituent bulk at the N9 position of the adenine moiety and its effect in dictating the structural aspects of silver-adenine frameworks. While adenine alone or 9-benzyl substituted ligand afforded mono and dinuclear dimeric entities, n-propyl substitution at the N9 position results in the formation of a metallaquartet. Longer n-alkyl chains (hexyl and nonyl) resulted in the formation of linear polymeric chains, via N1 and N7 coordination. © The Royal Society of Chemistry 2010.