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Seeram Ramakrishna - One of the best experts on this subject based on the ideXlab platform.
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Continuous tubular nanofibers of vanadium pentoxide by electrospinning for energy storage devices
Journal of Nanoparticle Research, 2012Co-Authors: Neeta L. Lala, Rajan Jose, Mashitah M. Yusoff, Seeram RamakrishnaAbstract:Tubular nanofibers (TNFs) of vanadium pentoxide (V_2O_5) were synthesized by electrospinning technique using a single spinneret for the first time by controlling the properties of the precursor Solution. A partially miscible Polymeric Solution of vanadium oxytrihydroxide [VO(OH)_3] was produced by hydrolysis of vanadyl acetylacetonate in Poly(vinylpyrrolidone) (PVP). The phase-separated polymer Solution formed the core of the electrospun fibers whereas the VO(OH)_3 formed the shell; the core PVP has been removed by controlled heat treatment. The TNFs had an inner diameter ~60 nm and wall thickness ~±100 nm. The capacitive behavior of the V_2O_5 TNFs was studied using cyclic voltammetry and galvanostatic cycling techniques. The studies showed ideal stable supercapacitive characteristics in the electrospun V_2O_5 TNFs.
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high performance dye sensitized solar cells with record open circuit voltage using tin oxide nanoflowers developed by electrospinning
Energy and Environmental Science, 2012Co-Authors: Naveen E Kumar, Rajan Jose, P. S. Archana, Mashitah M. Yusoff, Seeram Ramakrishna, Chellappan VijilaAbstract:Flower shaped nanostructures of an architypical transparent conducting oxide, SnO2, have been synthesized by an electrospinning technique for the first time by precisely controlling the precursor concentration in a Polymeric Solution. The flowers were made up of nanofibrils of diameter ∼70–100 nm, which in turn consisted of linear arrays of single crystalline nanoparticles of size 20–30 nm. Mott–Schottkey analysis shows that flowers have an order of magnitude higher electron density compared with the fibers despite their chemical similarity. Dye-sensitized solar cells fabricated using the flowers showed a record open circuit voltage of ∼700 mV and have one of the highest photoconversion efficiencies so far achieved with SnO2 and the iodide/triiodide electrolyte. The photoaction spectra and impedance spectroscopic measurements show that the flowers are characterized by a higher electron lifetime, owing to their enhanced crystallinity, compared to the conventional fibrous structure.
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nb2o5 photoelectrodes for dye sensitized solar cells choice of the polymorph
Journal of Physical Chemistry C, 2010Co-Authors: Le A Viet, Rajan Jose, M. V. Reddy, B V R Chowdari, Seeram RamakrishnaAbstract:Nanowires of Nb2O5 were developed in three polymorphic forms, namely, pseudo-hexagonal, orthorhombic, and monoclinic, by electrospinning a Polymeric Solution and by subsequent annealing. The materials were characterized by X-ray and electron diffraction, scanning and transmission electron microscopy, BET surface area measurements, absorption spectrometry, and cyclic voltammometry. These characterizations indicate that the monoclinic phase has a higher conduction band edge compared with the other two and is likely to display higher open circuit voltage in solar cells. Dye-sensitized solar cells were fabricated using the above polymorphs, and the device performances were studied. The pseudo-hexagonal phase showed higher device performance owing to its higher specific surface area compared with the others. However, when normalized, the device performances with respect to the dye-loading, the monoclinic phase gave superior performance. Studies on the charge transport properties using electrochemical impedance...
René Guinebretière - One of the best experts on this subject based on the ideXlab platform.
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In situ time-resolved small-angle X-ray scattering observation of the fractal aggregation process into tin alkoxide Polymeric Solution
Journal of Applied Crystallography, 2016Co-Authors: Matthieu Dumoulin, Wael Hamd, Elsa Thune, Cyrille Rochas, René GuinebretièreAbstract:SnO2 transparent gels have been synthesized from alkoxide precursor in toluene‐2‐propanol solvents. The chemical reactivity of transition metal alkoxides must be controlled in order to obtain sols and gels. In tin alkoxide based systems, this control can be achieved through complexation by a chelating agent such as acetylacetone. The gelation of the sols has been studied by in situ small‐angle X‐ray scattering (SAXS) measurements at the European Synchrotron Radiation Facility in Grenoble on the BM02 beamline. After the addition of water, primary particles are created and stick progressively together to form fractal aggregates. The primary particles are continually created during the aggregation process, which causes an evolution of the fractal dimension of the aggregate during gelation. This evolution is similar whatever the chemical composition is, meaning that the aggregation is ruled by one process which has been identified as reaction‐limited cluster aggregation. Nevertheless, the final size of the aggregates is dependent on the chemical composition of the sols.
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in situ time resolved small angle x ray scattering observation of the fractal aggregation process in tin alkoxide Polymeric Solution
Journal of Applied Crystallography, 2016Co-Authors: Matthieu Dumoulin, Wael Hamd, Elsa Thune, Cyrille Rochas, René GuinebretièreAbstract:SnO2 transparent gels have been synthesized from alkoxide precursor in toluene-2-propanol solvents. The chemical reactivity of transition metal alkoxides must be controlled in order to obtain sols and gels. In tin alkoxide based systems, this control can be achieved through complexation by a chelating agent such as acetylacetone. The gelation of the sols has been studied by in situ small-angle X-ray scattering (SAXS) measurements at the European Synchrotron Radiation Facility in Grenoble on the BM02 beamline. After the addition of water, primary particles are created and stick progressively together to form fractal aggregates. The primary particles are continually created during the aggregation process, which causes an evolution of the fractal dimension of the aggregate during gelation. This evolution is similar whatever the chemical composition is, meaning that the aggregation is ruled by one process which has been identified as reaction-limited cluster aggregation. Nevertheless, the final size of the aggregates is dependent on the chemical composition of the sols.
Matthieu Dumoulin - One of the best experts on this subject based on the ideXlab platform.
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In situ time-resolved small-angle X-ray scattering observation of the fractal aggregation process into tin alkoxide Polymeric Solution
Journal of Applied Crystallography, 2016Co-Authors: Matthieu Dumoulin, Wael Hamd, Elsa Thune, Cyrille Rochas, René GuinebretièreAbstract:SnO2 transparent gels have been synthesized from alkoxide precursor in toluene‐2‐propanol solvents. The chemical reactivity of transition metal alkoxides must be controlled in order to obtain sols and gels. In tin alkoxide based systems, this control can be achieved through complexation by a chelating agent such as acetylacetone. The gelation of the sols has been studied by in situ small‐angle X‐ray scattering (SAXS) measurements at the European Synchrotron Radiation Facility in Grenoble on the BM02 beamline. After the addition of water, primary particles are created and stick progressively together to form fractal aggregates. The primary particles are continually created during the aggregation process, which causes an evolution of the fractal dimension of the aggregate during gelation. This evolution is similar whatever the chemical composition is, meaning that the aggregation is ruled by one process which has been identified as reaction‐limited cluster aggregation. Nevertheless, the final size of the aggregates is dependent on the chemical composition of the sols.
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in situ time resolved small angle x ray scattering observation of the fractal aggregation process in tin alkoxide Polymeric Solution
Journal of Applied Crystallography, 2016Co-Authors: Matthieu Dumoulin, Wael Hamd, Elsa Thune, Cyrille Rochas, René GuinebretièreAbstract:SnO2 transparent gels have been synthesized from alkoxide precursor in toluene-2-propanol solvents. The chemical reactivity of transition metal alkoxides must be controlled in order to obtain sols and gels. In tin alkoxide based systems, this control can be achieved through complexation by a chelating agent such as acetylacetone. The gelation of the sols has been studied by in situ small-angle X-ray scattering (SAXS) measurements at the European Synchrotron Radiation Facility in Grenoble on the BM02 beamline. After the addition of water, primary particles are created and stick progressively together to form fractal aggregates. The primary particles are continually created during the aggregation process, which causes an evolution of the fractal dimension of the aggregate during gelation. This evolution is similar whatever the chemical composition is, meaning that the aggregation is ruled by one process which has been identified as reaction-limited cluster aggregation. Nevertheless, the final size of the aggregates is dependent on the chemical composition of the sols.
B W Brooks - One of the best experts on this subject based on the ideXlab platform.
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phase behaviour of a non ionic surfactant Polymeric Solution water system during the phase inversion process
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2005Co-Authors: F Xie, B W BrooksAbstract:Abstract A phase inversion method for making colloidal polymer composites is being considered. That method requires the formation of fine and stable emulsions of polymerisable monomer containing another kind of polymer. Suitable emulsions might be produced via phase inversion. Therefore, the phase behaviour of dispersions containing non-ionic surfactant, non-aqueous polymer Solutions (polyisobutene in styrene) and was investigated. Phase inversion maps, showing the behaviour of the emulsion system as a function of hydrophilic–lipophilic balance (HLB) and water volume fraction, are developed. Two types of non-ionic surfactants, polyoxyethylene sorbitanmonolaurate (SML), or polyoxyethylene nonylphenyl ether (NPE), were used in the study. There are two types of phase inversion (catastrophic and transitional) and, in some circumstances, complex drops may be formed. Five phase inversion boundaries have been found in the NPE system. These include one transitional inversion boundary and four catastrophic inversion boundaries. Unlike the NPE system, there are two transitional phase inversion boundaries in the SML system. With the non-aqueous Solutions used here, a stable polymer emulsion with sub-micron polymer drops could not be produced by using the transitional inversion route with either surfactant. However, it was possible to produce a stable polymer emulsion with sub-micron drops by approaching the catastrophic inversion condition. A drop size of about 500 nm was obtained by using a mixture of SML surfactants. As the “unstable” catastrophic inversion region is approached closely, the complex drops increased in size and became less stable.
Rajan Jose - One of the best experts on this subject based on the ideXlab platform.
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Continuous tubular nanofibers of vanadium pentoxide by electrospinning for energy storage devices
Journal of Nanoparticle Research, 2012Co-Authors: Neeta L. Lala, Rajan Jose, Mashitah M. Yusoff, Seeram RamakrishnaAbstract:Tubular nanofibers (TNFs) of vanadium pentoxide (V_2O_5) were synthesized by electrospinning technique using a single spinneret for the first time by controlling the properties of the precursor Solution. A partially miscible Polymeric Solution of vanadium oxytrihydroxide [VO(OH)_3] was produced by hydrolysis of vanadyl acetylacetonate in Poly(vinylpyrrolidone) (PVP). The phase-separated polymer Solution formed the core of the electrospun fibers whereas the VO(OH)_3 formed the shell; the core PVP has been removed by controlled heat treatment. The TNFs had an inner diameter ~60 nm and wall thickness ~±100 nm. The capacitive behavior of the V_2O_5 TNFs was studied using cyclic voltammetry and galvanostatic cycling techniques. The studies showed ideal stable supercapacitive characteristics in the electrospun V_2O_5 TNFs.
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high performance dye sensitized solar cells with record open circuit voltage using tin oxide nanoflowers developed by electrospinning
Energy and Environmental Science, 2012Co-Authors: Naveen E Kumar, Rajan Jose, P. S. Archana, Mashitah M. Yusoff, Seeram Ramakrishna, Chellappan VijilaAbstract:Flower shaped nanostructures of an architypical transparent conducting oxide, SnO2, have been synthesized by an electrospinning technique for the first time by precisely controlling the precursor concentration in a Polymeric Solution. The flowers were made up of nanofibrils of diameter ∼70–100 nm, which in turn consisted of linear arrays of single crystalline nanoparticles of size 20–30 nm. Mott–Schottkey analysis shows that flowers have an order of magnitude higher electron density compared with the fibers despite their chemical similarity. Dye-sensitized solar cells fabricated using the flowers showed a record open circuit voltage of ∼700 mV and have one of the highest photoconversion efficiencies so far achieved with SnO2 and the iodide/triiodide electrolyte. The photoaction spectra and impedance spectroscopic measurements show that the flowers are characterized by a higher electron lifetime, owing to their enhanced crystallinity, compared to the conventional fibrous structure.
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Electrospun metal oxides nanostructures for energy related devices
2011 IEEE Conference on Clean Energy and Technology (CET), 2011Co-Authors: Rajan Jose, P. S. Archana, A. Le Viet, M. V. Reddy, M.m. Yusoff, S. RamakrishnaAbstract:Metal oxide nanostructures of wide bandgap semiconductors with various morphologies, high degree of crystallinity and surface properties were fabricated by electrospinning a Polymeric Solution containing respective metal ions and their controlled heat treatment. The metal oxide nanostructures thus developed were tested for their application as charge separation and transport medium in solar cells, cathodes for low voltage (2 V) lithium ion batteries, and super capacitors. The solar cells thus fabricated features enhanced electron diffusion coefficient and energy storage devices featured stable electrochemical cycling thereby making electrospun metal oxide nanostructures a viable product for next generation energy industry.
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nb2o5 photoelectrodes for dye sensitized solar cells choice of the polymorph
Journal of Physical Chemistry C, 2010Co-Authors: Le A Viet, Rajan Jose, M. V. Reddy, B V R Chowdari, Seeram RamakrishnaAbstract:Nanowires of Nb2O5 were developed in three polymorphic forms, namely, pseudo-hexagonal, orthorhombic, and monoclinic, by electrospinning a Polymeric Solution and by subsequent annealing. The materials were characterized by X-ray and electron diffraction, scanning and transmission electron microscopy, BET surface area measurements, absorption spectrometry, and cyclic voltammometry. These characterizations indicate that the monoclinic phase has a higher conduction band edge compared with the other two and is likely to display higher open circuit voltage in solar cells. Dye-sensitized solar cells were fabricated using the above polymorphs, and the device performances were studied. The pseudo-hexagonal phase showed higher device performance owing to its higher specific surface area compared with the others. However, when normalized, the device performances with respect to the dye-loading, the monoclinic phase gave superior performance. Studies on the charge transport properties using electrochemical impedance...