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Reena Mary A.P.,Cochin University of Science and Technology | Reena Mary A.P.,Government Victoria College | Suchand Sandeep C.S.,Raman Research Institute | Narayanan T.N.,Rice University | And 4 more authors.
Nanotechnology | Year: 2011

Oxide free stable metallic nanofluids have the potential for various applications such as in thermal management and inkjet printing apart from being a candidate system for fundamental studies. A stable suspension of nickel nanoparticles of ∼ 5nm size has been realized by a modified two-step synthesis route. Structural characterization by x-ray diffraction and transmission electron microscopy shows that the nanoparticles are metallic and are phase pure. The nanoparticles exhibited superparamagnetic properties. The magneto-optical transmission properties of the nickel nanofluid (Ni-F) were investigated by linear optical dichroism measurements. The magnetic field dependent light transmission studies exhibited a polarization dependent optical absorption, known as optical dichroism, indicating that the nanoparticles suspended in the fluid are non-interacting and superparamagnetic in nature. The nonlinear optical limiting properties of Ni-F under high input optical fluence were then analyzed by an open aperture z-scan technique. The Ni-F exhibits a saturable absorption at moderate laser intensities while effective two-photon absorption is evident at higher intensities. The Ni-F appears to be a unique material for various optical devices such as field modulated gratings and optical switches which can be controlled by an external magnetic field. © 2011 IOP Publishing Ltd. Source


Joseph T.,Indian National Institute for Interdisciplinary Science and Technology | Joseph T.,Government Victoria College | Uma S.,Cochin University of Science and Technology | Philip J.,Cochin University of Science and Technology | Sebastian M.T.,Indian National Institute for Interdisciplinary Science and Technology
Journal of Materials Science: Materials in Electronics | Year: 2012

Polymer/Sr 2ZnSi 2O 7 (SZS) ceramic composites suitable for substrate applications have been developed using the polymers polystyrene (PS), high density polyethylene (HDPE) and Di-Glycidyl Ether of Bisphenol A(DGEBA). The dielectric, thermal and mechanical properties of the composites are investigated as a function of various concentrations of the ceramic filler. The obtained values of relative permittivity, dielectric loss tangent, thermal conductivity and coefficient of thermal expansion of the composites are compared with the corresponding theoretical predictions. The relative permittivity of the polymer/ceramic composites increases with filler loading. The dielectric loss tangent also shows the same trend except for DGEBA/SZS composites. The major advantages of the ceramic loading are improvement in thermal conductivity and a decrease in the coefficient of thermal expansion. The tensile strength of the composites decreases with increase in filler content, whereas an improvement is observed in microhardness. The variation of relative permittivity (at 1 MHz) of the composites is also studied as afunction of temperature. © 2011 Springer Science+Business Media, LLC. Source


Rappai J.P.,Cochin University of Science and Technology | Rappai J.P.,Government Victoria College | Karthikeyan J.,Cochin University of Science and Technology | Prathapan S.,Cochin University of Science and Technology | Unnikrishnan P.A.,Cochin University of Science and Technology
Synthetic Communications | Year: 2011

The dehydration of aldoximes and amides, and oxidation of benzoin are accomplished in one-pot using in situ-generated Burgess-type reagent. © Taylor & Francis Group, LLC. Source


Natarajan R.,Cochin University of Science and Technology | Unnikrishnan P.A.,Cochin University of Science and Technology | Radhamani S.,N S S College | Rappai J.P.,Government Victoria College | Prathapan S.,Cochin University of Science and Technology
Tetrahedron Letters | Year: 2016

Starting from easily accessible nitrones and acetylenes, a simple, metal free synthesis of substituted quinolines under mild conditions with high atom efficiency has been developed. Our method is flexible enough to introduce substituents regiospecifically at the 2,3,4,6,8-positions of the quinoline product. © 2016 Elsevier Ltd. All rights reserved. Source


Radhamani S.,Cochin University of Science and Technology | Natarajan R.,Cochin University of Science and Technology | Unnikrishnan P.A.,Cochin University of Science and Technology | Prathapan S.,Cochin University of Science and Technology | Rappai J.P.,Government Victoria College
New Journal of Chemistry | Year: 2015

Depending on the nature of N- and C-substituents, nitrones exhibit diverse reactivity towards electron deficient acetylenes. Observed reactions include formal 1,3-dipolar cycloaddition and nucleophilic addition reactions. Possible involvement of zwitterionic intermediates and an unusual 1-aza-Cope rearrangement account for the generation of unexpected 1:1 adducts in the reaction of N-arylnitrones. © 2015 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique. Source

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