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Richard T Oakley - One of the best experts on this subject based on the ideXlab platform.
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semiquinone bridged bisdithiazolyl radicals as neutral radical conductors
Journal of the American Chemical Society, 2012Co-Authors: Aaron Mailman, Kristina Lekin, Abdeljalil Assoud, Craig M Robertson, Bruce C Noll, Charles F Campana, Judith A K Howard, Paul A Dube, Richard T OakleyAbstract:Semiquinone-bridged bisdithiazolyls 3 represent a new class of resonance-stabilized neutral radical for use in the design of single-component conductive materials. As such, they display electrochemical cell potentials lower than those of related pyridine-bridged bisdithiazolyls, a finding which heralds a reduced on-site Coulomb repulsion U. Crystallographic characterization of the chloro-substituted derivative 3a and its acetonitrile solvate 3a·MeCN, both of which crystallize in the polar orthorhombic space group Pna21, revealed the importance of intermolecular oxygen-to-sulfur (CO···SN) interactions in generating rigid, tightly packed radical π-stacks, including the structural motif found for 3a·MeCN in which radicals in neighboring π-stacks are locked into slipped-ribbon-like arrays. This architecture gives rise to strong intra- and interstack overlap and hence a large electronic bandwidth W. Variable-Temperature Conductivity measurements on 3a and 3a·MeCN indicated high values of σ(300 K) (>10–3 S cm–1...
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resonating valence bond ground state in a phenalenyl based neutral radical conductor
Science, 2005Co-Authors: Sushanta K Pal, M E Itkis, Fook S Tham, R W Reed, Richard T Oakley, R C HaddonAbstract:An organic material composed of neutral free radicals based on the spirobiphenalenyl system exhibits a room Temperature Conductivity of 0.3 siemens per centimeter and a high-symmetry crystal structure. It displays the Temperature-independent Pauli paramagnetism characteristic of a metal with a magnetic susceptibility that implies a density of states at the Fermi level of 15.5 states per electron volt per mole. Extended Huckel calculations indicate that the solid is a three-dimensional organic metal with a band width of ∼0.5 electron volts. However, the compound shows activated Conductivity (activation energy, 0.054 electron volts) and an optical energy gap of 0.34 electron volts. We argue that these apparently contradictory properties are best resolved in terms of the resonating valence-bond ground state originally suggested by Pauling, but with the modifications introduced by Anderson.
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resonating valence bond ground state in a phenalenyl based neutral radical conductor
Science, 2005Co-Authors: Sushanta K Pal, M E Itkis, Fook S Tham, R W Reed, Richard T Oakley, R C HaddonAbstract:An organic material composed of neutral free radicals based on the spirobiphenalenyl system exhibits a room Temperature Conductivity of 0.3 siemens per centimeter and a high-symmetry crystal structure. It displays the Temperature-independent Pauli paramagnetism characteristic of a metal with a magnetic susceptibility that implies a density of states at the Fermi level of 15.5 states per electron volt per mole. Extended Huckel calculations indicate that the solid is a three-dimensional organic metal with a band width of approximately 0.5 electron volts. However, the compound shows activated Conductivity (activation energy, 0.054 electron volts) and an optical energy gap of 0.34 electron volts. We argue that these apparently contradictory properties are best resolved in terms of the resonating valence-bond ground state originally suggested by Pauling, but with the modifications introduced by Anderson.
R. C. Agrawal - One of the best experts on this subject based on the ideXlab platform.
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investigations on ion transport properties of hot press cast magnesium ion conducting nano composite polymer electrolyte ncpe films effect of filler particle dispersal on room Temperature Conductivity
Materials Chemistry and Physics, 2013Co-Authors: R. C. Agrawal, Dinesh K Sahu, Y K Mahipal, Rehana AshrafiAbstract:Abstract Investigations on ion transport properties of Mg2+-ion conducting Nano-Composite Polymer Electrolyte (NCPE) films: [80PEO: 20Mg (CF3SO3)2] + micro/nano sized particles of passive/active filler materials viz. SiO2, TiO2, MgO, have been reported. NCPE films have been cast by hot-press technique. Solid Polymer Electrolyte (SPE) composition: [80PEO: 20Mg (CF3SO3)2], identified as one of the high conducting films in an earlier study with room Temperature Conductivity (σrt) ∼2.77 × 10−6 S cm−1, has been used as Ist-phase host matrix and the filler particles as IInd-phase dispersoid. The effect of dispersal of different filler materials on Conductivity of NCPE films has also been investigated. NCPE films exhibiting highest room Temperature Conductivity, referred to as Optimum Conducting Composition (OCC), has been identified from the filler particle dependent Conductivity studies. The phase identification and materials characterizations on NCPE OCC film have been performed using XRD, SEM, FTIR and DSC techniques. The ion transport property has been characterized in terms of ionic Conductivity (σ) and ionic transference number i.e. total (tion) and cation (Mg2+) transference number (t+). These ionic parameters have been determined experimentally using different ac/dc techniques. The Temperature dependent Conductivity measurements have also been carried out to compute activation energy (Ea) by least square linear fitting of Arrhenius plot: ‘log σ − 1/T’.
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hot press synthesized polyethylene oxide based proton conducting nanocomposite polymer electrolyte dispersed with sio2 nanoparticles
Solid State Ionics, 2008Co-Authors: S A Hashmi, G P Pandey, R. C. AgrawalAbstract:Abstract Ion transport studies on polyethylene oxide (PEO) based nanocomposite polymer electrolyte (NCPE) membranes (PEO: NH 4 HSO 4 ) dispersed with nanosized SiO 2 particle in varying wt.(%) have been reported. NCPE films have been cast by a novel hot-press (extrusion) technique. Scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infra-red (FTIR) spectroscopy, ionic transport number ( t ion ) and electrical Conductivity ( σ ) studies have been carried out on hot-press films and the results have been compared with NCPE films prepared by the standard solution cast technique. As a consequence of dispersion of a fractional amount of nanosized SiO 2 filler particles into the polymer-salt complex (PEO: NH 4 HSO 4 ) host matrix, an enhancement of approximately an order of magnitude in the room Temperature Conductivity resulted. NCPE membranes with SiO 2 content: 5 wt.% (Solution cast) and 15 wt.% (hot-press) exhibited optimum room Temperature Conductivity ( σ ) values ~ 2.5 × 10 − 4 S cm − 1 and ~ 1.4 × 10 − 4 S cm − 1 , respectively. Two maxima appeared in the SiO 2 concentration dependent Conductivity plot for hot-pressed NCPE films which are discussed in the light of an existing two percolation threshold model.
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Solid polymer electrolytes: Materials designing and all-solid-state battery applications: An overview
Journal of Physics D: Applied Physics, 2008Co-Authors: R. C. Agrawal, Gaind P. PandeyAbstract:Polymer electrolytes are promising materials for electrochemical device applications, namely, high energy density rechargeable batteries, fuel cells, supercapacitors, electrochromic displays, etc. The area of polymer electrolytes has gone through various developmental stages, i.e. from dry solid polymer electrolyte (SPE) systems to plasticized, gels, rubbery to micro/nano-composite polymer electrolytes. The polymer gel electrolytes, incorporating organic solvents, exhibit room Temperature Conductivity as high as ~10 −3 S cm −1 , while dry SPEs still suffer from poor ionic Conductivity lower than 10 −5 S cm −1 . Several approaches have been adopted to enhance the room Temperature Conductivity in the vicinity of 10 −4 S cm −1 as well as to improve the mechanical stability and interfacial activity of SPEs. In this review, the criteria of an ideal polymer electrolyte for electrochemical device applications have been discussed in brief along with presenting an overall glimpse of the progress made in polymer electrolyte materials designing, their broad classification and the recent advancements made in this branch of materials science. The characteristic advantages of employing polymer electrolyte membranes in all-solid-state battery applications have also been discussed.
Shahzada Ahmad - One of the best experts on this subject based on the ideXlab platform.
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dye sensitized solar cells based on poly 3 4 ethylenedioxythiophene counter electrode derived from ionic liquids
Journal of Materials Chemistry, 2010Co-Authors: Shahzada Ahmad, Junho Yum, Zhang Xianxi, Michael Gratzel, Hansjurgen Butt, Mohammad Khaja NazeeruddinAbstract:Poly (3,4-ethylenedioxythiophene) (PEDOT) nanoporous layers were prepared with electro-oxidative polymerization using room Temperature hydrophobic ionic liquids as a medium. The synthesized highly porous PEDOT films exhibit room Temperature Conductivity value of 195 S cm−1 along with reproducible high cycling life. These films were used as counter electrodes in dye-sensitized solar cells yielding ∼8% power conversion efficiency, which is close to the classical platinum coated counter electrode (8.7%). The photovoltaic performance increases as we lower the PEDOT film thickness as the thin films has reasonably high catalytic properties.
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nanocomposite electrolytes with fumed silica in poly methyl methacrylate thermal rheological and Conductivity studies
Journal of Power Sources, 2005Co-Authors: Shahzada Ahmad, Sharif Ahmad, S A AgnihotryAbstract:Abstract Composite polymer electrolytes (CPEs), were prepared by adding hydrophilic fumed silica in different proportions upto 5 wt.% to gel polymeric electrolyte (GPE) comprising liquid electrolyte (1 M LiClO 4 in propylene carbonate) immobilized with 15 wt.% poly(methyl methacrylate) (PMMA). The effect of fumed silica content in the CPEs on the ionic Conductivity and viscosity over a wide Temperature range was investigated. The resultant CPEs showed room Temperature Conductivity ( σ 25 ) as high as 3.8 mS cm −1 along with viscosity value of 3700 P for 2 wt.% SiO 2 addition. Fumed silica addition both to the liquid electrolyte and to the GPE exhibits similar Conductivity behaviour and this suggests a passive role of PMMA. The shear thinning behaviour, pointing towards easy processablity, high thermal stability and low volatility, makes these CPEs potential candidates as solid-like electrolytes for electrochemical devices.
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composite gel electrolytes based on poly methylmethacrylate and hydrophilic fumed silica
Electrochimica Acta, 2004Co-Authors: S A Agnihotry, Shahzada Ahmad, Devinder Gupta, Sharif AhmadAbstract:Abstract Transparent and highly conducting (10 −3 S cm −1 ) composite gel electrolytes (cges) based on poly(methylmethacrylate) (PMMA) with 1 M LiClO 4 in propylene carbonate (PC) and hydrophilic fumed silica (SiO 2 ) added in different proportions up to 5 wt.% as the constituents were prepared. The unique property of the aggregates of surface hydroxyl groups of hydrophilic fumed silica to link together through hydrogen bonding to form a network and the interactions between various constituents, probed by FTIR spectroscopic technique, have revealed to control both the transport and rheological properties of the cges. The high mechanical and electrochemical stability of these cges makes them potential candidates as electrolytes in “All Solid State Electrochromic Windows” (ECWs). Detailed room Temperature Conductivity and viscosity measurements correlated to FTIR spectroscopic analysis of cges along with their optical and electrochemical investigations is reported in the present paper.
Avarvari Narcis - One of the best experts on this subject based on the ideXlab platform.
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Localization versus Delocalization in Chiral Single Component Conductors of Gold Bis(dithiolene) Complexes
'American Chemical Society (ACS)', 2019Co-Authors: Branzea, Diana G., Auban-senzier Pascale, Canadell Enric, Pop Flavia, Clerac Rodolphe, Alemany Cahner I Pere, Avarvari NarcisAbstract:The first examples of chiral single component conductors are reported. Both (S,S) and (R,R) enantiomers of 5,6-dimethy1-5,6-dihydro-1,4-dithiin-2,3-dithiolate (dm=dddt) ligand have been used to prepare anionic metal bis(dithiOlene) complexes formulated as ([(n-Bu)(4)N][M(dm-dddt)(2)] (M = Au, Ni), which are isostructural according to single crystal X-ray analysis. Single crystal transport measurements indicate semiconducting behavior for the anionic radical Ni complexes, with low room Temperature Conductivity values and high activation energies. Electrocrystallization experiments provided neutral [M(dm-dddt)(2)] (M = Au, Ni) complexes. The neutral radical gold compounds Show intermolecular S center dot center dot center dot S inte'raction's in the solid state giving rise to layers interconnected through Weak C-H center dot center dot center dot S hydrogen bonds. The most peculiar structural feature concerns a dissymmetry between the two dithiolene moieties, while the nickel counterpart is symmetric. Single crystal resistivity measurements show thermally activated behavior for the open-shell gold complexes, with room Temperature Conductivity values of 0.02-0:04 S.cm-' and activation energies strongly influenced by hydrostatic pressure. A thorough thebretical study on nickel anion radical and gold neutral radiCal bis(dithiolene) complexes applied to the chiral complexes [M(dm-dddt)(2)] (M = Ail, Ni-) and to a series of previously reported compounds addressed, the issue of symmetry versus asymmetry from an electronic coupling perspective between the two dithiolene ligands. It results that neutral gold' complexes with dithiolene ligands without 'extended delocalization are Class II mixed-valent compounds in the Robin and Day classification, presenting an inherent tendency toward asymmetric structures,, which can be however modulated by the intermolecular organization in the solid state
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Synthesis and physical properties of purely organic BEDT-TTF-based conductors containing hetero-/homosubstituted Cl/CN-anilate derivatives
'American Chemical Society (ACS)', 2017Co-Authors: Ashoka Sahadevan Suchithra, Monni Noemi, Abhervé Alexandre, Auban-senzier Pascale, Canadell Enric, Mercuri, Maria L., Avarvari NarcisAbstract:Radical cation salts composed of a bis(ethylenedithio)tetrathiafulvalene (ET) donor with homo-/heterosubstituted Cl/CN anilic acids as purely organic molecular conducting materials formulated as [BEDT-TTF]2[HClCNAn] (1) and [BEDT-TTF][HCl2An] (2) have been prepared by electrocrystallization. Compounds 1 and 2 crystallized in the monoclinic space group P2/c for 1 and I2/a for 2, showing segregated donor-anion layers arranged in a αâ\u80²-type donor packing pattern (1) and twisted parallel columns (2), respectively. Single-crystal Conductivity measurements show that 1 is a semiconductor with room-Temperature Conductivity of 10-2S cm-1and an activation energy Eaof 1900 K
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Localization versus delocalization in chiral single component conductors of gold bis(dithiolene) complexes
'American Chemical Society (ACS)', 2016Co-Authors: Branzea, Diana G., Auban-senzier Pascale, Canadell Enric, Pop Flavia, Clerac Rodolphe, Alemany Pere, Avarvari NarcisAbstract:The first examples of chiral single component conductors are reported. Both (S,S) and (R,R) enantiomers of 5,6-dimethyl-5,6-dihydro-1,4-dithiin-2,3-dithiolate (dm-dddt) ligand have been used to prepare anionic metal bis(dithiolene) complexes formulated as ([(n-Bu)4N][M(dm-dddt)2] (M = Au, Ni), which are isostructural according to single crystal X-ray analysis. Single crystal transport measurements indicate semiconducting behavior for the anionic radical Ni complexes, with low room Temperature Conductivity values and high activation energies. Electrocrystallization experiments provided neutral [M(dm-dddt)2] (M = Au, Ni) complexes. The neutral radical gold compounds show intermolecular S···S interactions in the solid state giving rise to layers interconnected through weak C–H···S hydrogen bonds. The most peculiar structural feature concerns a dissymmetry between the two dithiolene moieties, while the nickel counterpart is symmetric. Single crystal resistivity measurements show thermally activated behavior for the open-shell gold complexes, with room Temperature Conductivity values of 0.02–0.04 S·cm–1 and activation energies strongly influenced by hydrostatic pressure. A thorough theoretical study on nickel anion radical and gold neutral radical bis(dithiolene) complexes applied to the chiral complexes [M(dm-dddt)2] (M = Au, Ni–) and to a series of previously reported compounds addressed the issue of symmetry versus asymmetry from an electronic coupling perspective between the two dithiolene ligands. It results that neutral gold complexes with dithiolene ligands without extended delocalization are Class II mixed-valent compounds in the Robin and Day classification, presenting an inherent tendency toward asymmetric structures, which can be however modulated by the intermolecular organization in the solid state.This work was supported in France by the National Agency for Research (ANR Inter, ANR-12-IS07-0004-04, CREMM Project), the Region Pays de la Loire (grant for D.B.), the CNRS, the University of Angers, the University of Bordeaux and the Aquitaine Region. Work in Spain was supported by the Spanish Ministerio de Economía y Competitividad (Grants FIS2012- 37549-C05-05, FIS2015-64886-C5-4-P and CTQ2015-64579- C3-3-P) and Generalitat de Catalunya (2014SGR301 and XRQTC). E.C. acknowledges support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grant SEV-2015-0496.Peer reviewe
Narcis Avarvari - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and Physical Properties of Purely Organic BEDT-TTF-Based Conductors Containing Hetero-/Homosubstituted Cl/CN-Anilate Derivatives
2017Co-Authors: Suchithra Ashoka Sahadevan, Pascale Auban-senzier, Enric Canadell, Noemi Monni, Alexandre Abhervé, Maria Laura Mercuri, Narcis AvarvariAbstract:Radical cation salts composed of a bis(ethylenedithio)tetrathiafulvalene (ET) donor with homo-/heterosubstituted Cl/CN anilic acids as purely organic molecular conducting materials formulated as [BEDT-TTF]2[HClCNAn] (1) and [BEDT-TTF][HCl2An] (2) have been prepared by electrocrystallization. Compounds 1 and 2 crystallized in the monoclinic space group P2/c for 1 and I2/a for 2, showing segregated donor-anion layers arranged in a α′-type donor packing pattern (1) and twisted parallel columns (2), respectively. Single-crystal Conductivity measurements show that 1 is a semiconductor with room-Temperature Conductivity of 10–2 S cm–1 and an activation energy Ea of 1900 K
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Localization versus Delocalization in Chiral Single Component Conductors of Gold Bis(dithiolene) Complexes
2016Co-Authors: Diana G. Branzea, Flavia Pop, Pascale Auban-senzier, Rodolphe Clérac, Pere Alemany, Enric Canadell, Narcis AvarvariAbstract:The first examples of chiral single component conductors are reported. Both (S,S) and (R,R) enantiomers of 5,6-dimethyl-5,6-dihydro-1,4-dithiin-2,3-dithiolate (dm-dddt) ligand have been used to prepare anionic metal bis(dithiolene) complexes formulated as ([(n-Bu)4N][M(dm-dddt)2] (M = Au, Ni), which are isostructural according to single crystal X-ray analysis. Single crystal transport measurements indicate semiconducting behavior for the anionic radical Ni complexes, with low room Temperature Conductivity values and high activation energies. Electrocrystallization experiments provided neutral [M(dm-dddt)2] (M = Au, Ni) complexes. The neutral radical gold compounds show intermolecular S···S interactions in the solid state giving rise to layers interconnected through weak C–H···S hydrogen bonds. The most peculiar structural feature concerns a dissymmetry between the two dithiolene moieties, while the nickel counterpart is symmetric. Single crystal resistivity measurements show thermally activated behavior for the open-shell gold complexes, with room Temperature Conductivity values of 0.02–0.04 S·cm–1 and activation energies strongly influenced by hydrostatic pressure. A thorough theoretical study on nickel anion radical and gold neutral radical bis(dithiolene) complexes applied to the chiral complexes [M(dm-dddt)2] (M = Au, Ni–) and to a series of previously reported compounds addressed the issue of symmetry versus asymmetry from an electronic coupling perspective between the two dithiolene ligands. It results that neutral gold complexes with dithiolene ligands without extended delocalization are Class II mixed-valent compounds in the Robin and Day classification, presenting an inherent tendency toward asymmetric structures, which can be however modulated by the intermolecular organization in the solid state
