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Yuhlang Lee - One of the best experts on this subject based on the ideXlab platform.
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Highly efficient Gel-State dye-sensitized solar cells prepared using propionitrile and poly(vinylidene fluoride-co-hexafluoropropylene)
Journal of Power Sources, 2016Co-Authors: Shanmuganathan Venkatesan, Noor Hidayati, I-ping Liu, Yuhlang LeeAbstract:Abstract Propionitrile (PPN) solvent based iodide/triiodide liquid-electrolyte is utilized to prepare highly efficient poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) polymer Gel electrolytes (PGEs) of dye-sensitized solar cells, aiming at improving the energy conversion efficiency as well as the stability of Gel-State DSSCs. The concentrations effect of the PVdF-HFP on the properties of PGEs and the performance of the corresponding cells are studied. The results show that the in-situ Gelation is performed for the PVdF-HFP concentration range of 8–18% at room temperature. However, increasing the concentration of polymer in the PGEs triggers a decrease in the diffusivity and conductivity of the PGEs, but an increase in the phase transition temperature of the PGEs. A high phase transition temperature is obtained for the PGEs with 18 wt% PVdF-HFP, which increase the long-term stability of the Gel-State DSSC. By using the 18 wt% PVdF-HFP in the presence of 5 wt% TiO2 nanofillers (NFs), Gel-State cells with an efficiency of 8.38% can be obtained, which is higher than that achieved by liquid-State cells (7.55%). After 1000 h test at room temperature (RT) and 50 °C, the cell can retain 96% and 82%, respectively, of its initial efficiency.
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Stability improvement of Gel-State dye-sensitized solar cells by utilization the co-solvent effect of propionitrile/acetonitrile and 3-methoxypropionitrile/acetonitrile with poly(acrylonitrile-co-vinyl acetate)
Journal of Power Sources, 2015Co-Authors: Shanmugam Venkatesan, Hsisheng Teng, Shon Chen Kao, Yuhlang LeeAbstract:Abstract Propionitrile (PPN) or 3-methoxypropionitrile (MPN) is mixed with acetonitrile (ACN) to prepare ACN/PPN and ACN/MPN co-solvents and used to fabricate polymer Gel electrolytes (PGEs) of dye-sensitized solar cells (DSSCs), aiming at improving the stability of Gel-State DSSCs. Co-solvents with various ratios are utilized to prepare PGEs using poly(acrylonitrile-co-vinyl acetate) (PAN-VA) as the Gelator. The ratio effects of the co-solvents on the properties of PGEs and the performances of the corresponding DSSCs are studied. The results show that in-situ Gelation of the Gel-electrolytes can still be performed at the presence of 40% PPN or 30% MPN. However, increasing the composition of PPN and MPN in the co-solvents triggers a decrease in the diffusivity and conductivity of the PGEs, but an increase in the viscosity. Therefore, the energy conversion efficiencies of the cells decrease as a result. However, the introduction of PPN and MPN elevates the Gel-to-liquid transition temperature (Tp) of the PGEs which significantly increases the stability of the Gel-State DSSCs. Comparing between the effects of the two co-solvents, PPN and MPN have similar effect on elevation of Tp, but the conductivity of PGEs and the corresponding cell efficiency are higher for the ACN/PPN system, attributed to its lower viscosity compared with ACN/MPN system. By using the ACN/PPN (60/40) co-solvent at the presence of TiO2 fillers, Gel-State cell with an efficiency of 8.3% can be achieved, which is even higher than that obtained by the liquid State cell (8%). After 500 h test at 60 °C, the cell can retain 95.4% of its initial efficiency.
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highly efficient Gel State dye sensitized solar cells prepared using poly acrylonitrile co vinyl acetate based polymer electrolytes
Physical Chemistry Chemical Physics, 2013Co-Authors: Ching Lun Chen, Ting Wei Chang, Hsisheng Teng, Chiayuan Chen, Yu Min Yang, Yuhlang LeeAbstract:Poly(acrylonitrile-co-vinyl acetate) (PAN-VA) is utilized as a Gelation agent to prepare Gel-State electrolytes for dye-sensitized solar cell (DSSC) applications. Based on the synergistic effect of PAN-VA and TiO2 fillers in the electrolyte, the Gel-State DSSC can achieve a conversion efficiency higher than that of a liquid counterpart. The high performance of the Gel-electrolyte is attributed to the in situ Gelation property of the Gel-electrolyte, the contribution of the PAN-VA to the charge transfer, as well as the enhancement effect of TiO2 fillers on the charge transfer at the Pt–electrolyte interface. The experimental results show that the efficiencies of the Gel-State cells have little dependence on the conductivity of the electrolytes with various contents of PAN-VA, but are closely related to the penetration situation of the electrolyte in the TiO2 film. For PAN-VA concentrations ≤15 wt%, the electrolyte can be easily injected at room temperature based on its in situ Gelation property. For higher PAN-VA concentrations, good penetration of the high viscous electrolyte can be achieved by elevating the operation temperature. By utilizing a heteroleptic ruthenium dye (coded CYC-B11), Gel-State DSSCs with an efficiency of above 10% are obtained. Acceleration tests show that the cell is stable under one-sun illumination at 60 °C.
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preparation of highly efficient Gel State dye sensitized solar cells using polymer Gel electrolytes based on poly acrylonitrile co vinyl acetate
Journal of Materials Chemistry, 2011Co-Authors: Ching Lun Chen, Hsisheng Teng, Yuhlang LeeAbstract:A highly efficient Gel-State electrolyte was fabricated by using poly(acrylonitrile -co-vinyl acetate) (PAN–VA) as the Gelator of an 3-methoxypropionitrile (MPN)-based liquid electrolyte and was applied in dye-sensitized solar cells (DSSCs). The VA segaments act to dissolve the copolymer into the electrolyte, forming a Gel-State structure. The electric conductivity of the Gel-State electrolyte is comparable to that of the liquid electrolyte, attributed to the enhancement effect of the AN segments to the dissociation of LiI and 1-propyl-2,3-dimethylimidazolium iodide (DMPII). This effect also leads to a slightly downward shift of the TiO2 conduction band edge toward positive potentials. The energy conversion efficiency of the DSSC achieved by using this Gel-electrolyte is 8.34%, which is 97% the value of the liquid-State cell (8.63%).
Zhifeng Shao - One of the best experts on this subject based on the ideXlab platform.
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gramicidin a aggregation in supported Gel State phosphatidylcholine bilayers
Biochemistry, 1996Co-Authors: Daniel M. Czajkowsky, Zhifeng ShaoAbstract:Using an atomic force microscope, supported bilayers of saturated phosphatidylcholine (in the Gel State) containing various amounts of gramicidin A (gA) were imaged in aqueous solutions and at room temperature. gA clusters were directly observed for the first time under these conditions. It was found that, at a lower gA concentration, gA aggregated into domains, composed of small clusters along with a considerable amount of lipids. This basic aggregation unit, most likely a hexamer, remained the same for acyl chain lengths from 14 to 18 carbons. These small clusters were observed to form elongated aggregates (line type) but never into extended pure gA domains. When gA concentrations were increased, for bilayers with 16 carbons or less, gA aggregated into larger domains but the basic unit remained separated by lipid molecules. At about 5 mol % gA, a percolation-like transition occurred at which the line type aggregates were connected to each other. However, for bilayers with more than 16 carbons, multiple ...
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Gramicidin A Aggregation in Supported Gel State Phosphatidylcholine Bilayers
Biochemistry, 1996Co-Authors: Jianxun Mou, Daniel M. Czajkowsky, Zhifeng ShaoAbstract:Using an atomic force microscope, supported bilayers of saturated phosphatidylcholine (in the Gel State) containing various amounts of gramicidin A (gA) were imaged in aqueous solutions and at room temperature. gA clusters were directly observed for the first time under these conditions. It was found that, at a lower gA concentration, gA aggregated into domains, composed of small clusters along with a considerable amount of lipids. This basic aggregation unit, most likely a hexamer, remained the same for acyl chain lengths from 14 to 18 carbons. These small clusters were observed to form elongated aggregates (line type) but never into extended pure gA domains. When gA concentrations were increased, for bilayers with 16 carbons or less, gA aggregated into larger domains but the basic unit remained separated by lipid molecules. At about 5 mol % gA, a percolation-like transition occurred at which the line type aggregates were connected to each other. However, for bilayers with more than 16 carbons, multiple lamellar structures were formed at higher gA fractions and the top layer had a ripple-like surface morphology. The molecular mechanism for the formation of these peculiar structures remains to be elucidated.
Robert B Moore - One of the best experts on this subject based on the ideXlab platform.
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blocky ionomers via sulfonation of poly ether ether ketone in the semicrystalline Gel State
Macromolecules, 2018Co-Authors: Lindsey J Anderson, Xijing Yuan, Gregory B Fahs, Robert B MooreAbstract:Blocky sulfonated poly(ether ether ketone) (SPEEK) ionomers were synthesized by postpolymerization functionalization in the Gel State. Matched sets of blocky and random SPEEK with ion contents betw...
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Blocky bromination of syndiotactic polystyrene via post-polymerization functionalization in the heterogeneous Gel State
Polymer Chemistry, 2018Co-Authors: Kristen F. Noble, Alexandria M. Noble, Samantha J. Talley, Robert B MooreAbstract:This work demonstrates the successful blocky bromination of syndiotactic polystyrene (sPS-co-sPS-Br) copolymers containing 6–30 mol% p-bromostyrene units, using a post-polymerization functionalization method conducted in the heterogeneous Gel State. For comparison, a matched set of randomly brominated sPS-co-sPS-Br copolymers was prepared using homogeneous (solution-State) reaction conditions. The degree of bromination and copolymer microstructure were evaluated using 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The NMR spectra of Gel-State (Blocky) and solution-State (Random) copolymers exhibit strikingly different resonance frequencies and peak intensities above 6 mol% Br and provide direct evidence that functionalization in the Gel State produces copolymers with non-random “blocky” microstructures. Quenched films of the Blocky copolymers, analyzed using ultra-small-angle X-ray scattering (USAXS) and small-angle X-ray scattering (SAXS), show micro-phase separated morphologies, which further supports that the Blocky copolymers contain distinct segments of pure sPS and segments of randomly brominated sPS unlike their completely Random analogs. Crystallization behavior of the copolymers, examined using differential scanning calorimetry (DSC), demonstrates that the Blocky copolymers are more crystallizable and crystallize faster at lower supercooling compared to their Random analogs. Computer simulations of the blocky copolymers were developed based on the semicrystalline morphology of a 10 w/v% sPS/CCl4 Gel, to rationalize the effect of heterogeneous functionalization on copolymer microstructure and crystallization behavior. The simulations were found to agree with the microstructural analysis based on the NMR results and confirm that restricting the accessibility of the brominating reagent to monomers well removed from the crystalline fraction of the Gel network produces copolymers with a greater prevalence of long, uninterrupted sPS homopolymer sequences. Thus, the blocky microstructure is advantageous for preserving desired crystallizability of the resulting blocky copolymers.
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Blocky Ionomers via Sulfonation of Poly(ether ether ketone) in the Semicrystalline Gel State
2018Co-Authors: Lindsey J. Anderson, Xijing Yuan, Gregory B Fahs, Robert B MooreAbstract:Blocky sulfonated poly(ether ether ketone) (SPEEK) ionomers were synthesized by postpolymerization functionalization in the Gel State. Matched sets of blocky and random SPEEK with ion contents between 3 and 11 mol % were prepared, and the thermal transitions and crystallization kinetics were examined using differential scanning calorimetry (DSC). At similar ion contents, the blocky SPEEK exhibited higher crystallizability and faster crystallization kinetics than random SPEEK. Reduced scattering contrast in the USAXS/SAXS/WAXD analysis of the blocky SPEEK copolymer membranes, relative to the random analogues, suggested that the ionic aggregates in blocky SPEEK were distributed in close proximity to the crystalline domains. Despite similar water uptake values for the low ion content random and blocky SPEEK membranes, the blocky SPEEK exhibited higher proton conductivities than their random analogues. At significantly higher ion contents (45 mol %), the blocky SPEEK membranes remained semicrystalline, showed controlled water uptake, and exhibited a 2.5 times higher conductivity over that of the amorphous, random analogues. Moreover, these new blocky, semicrystalline SPEEK membranes were found to exhibit a proton conductivity that was comparable to that of the benchmark 1100 EW Nafion
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Blocky Sulfonation of Syndiotactic Polystyrene: A Facile Route toward Tailored Ionomer Architecture via Postpolymerization Functionalization in the Gel State
Macromolecules, 2017Co-Authors: Gregory B Fahs, Sonya D. Benson, Robert B MooreAbstract:Blocky sulfonated syndiotactic polystyrene (SsPS) copolymers were produced using a recently developed postpolymerization functionalization procedure conducted in the Gel State. The thermal properties and crystallization behavior of a matched set of blocky and random SsPS copolymers containing 3 and 10 mol % sulfonate groups were compared using differential scanning calorimetry (DSC), which shows that the blocky functionalization architecture displays a much faster rate of crystallization even at low sulfonate contents and a higher crystallizability at high sulfonate contents. The glass transition temperature for Gel-State-functionalized copolymers was found to be independent of sulfonic acid content above 4% sulfonation, consistent with behavior observed in previous studies of sodium styrenesulfonate block copolymers. Small-angle X-ray scattering (SAXS) from the blocky copolymer indicates that the sulfonated units are distributed within the amorphous interlamellar domains. Wide-angle X-ray diffraction (WA...
Daniel M. Czajkowsky - One of the best experts on this subject based on the ideXlab platform.
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gramicidin a aggregation in supported Gel State phosphatidylcholine bilayers
Biochemistry, 1996Co-Authors: Daniel M. Czajkowsky, Zhifeng ShaoAbstract:Using an atomic force microscope, supported bilayers of saturated phosphatidylcholine (in the Gel State) containing various amounts of gramicidin A (gA) were imaged in aqueous solutions and at room temperature. gA clusters were directly observed for the first time under these conditions. It was found that, at a lower gA concentration, gA aggregated into domains, composed of small clusters along with a considerable amount of lipids. This basic aggregation unit, most likely a hexamer, remained the same for acyl chain lengths from 14 to 18 carbons. These small clusters were observed to form elongated aggregates (line type) but never into extended pure gA domains. When gA concentrations were increased, for bilayers with 16 carbons or less, gA aggregated into larger domains but the basic unit remained separated by lipid molecules. At about 5 mol % gA, a percolation-like transition occurred at which the line type aggregates were connected to each other. However, for bilayers with more than 16 carbons, multiple ...
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Gramicidin A Aggregation in Supported Gel State Phosphatidylcholine Bilayers
Biochemistry, 1996Co-Authors: Jianxun Mou, Daniel M. Czajkowsky, Zhifeng ShaoAbstract:Using an atomic force microscope, supported bilayers of saturated phosphatidylcholine (in the Gel State) containing various amounts of gramicidin A (gA) were imaged in aqueous solutions and at room temperature. gA clusters were directly observed for the first time under these conditions. It was found that, at a lower gA concentration, gA aggregated into domains, composed of small clusters along with a considerable amount of lipids. This basic aggregation unit, most likely a hexamer, remained the same for acyl chain lengths from 14 to 18 carbons. These small clusters were observed to form elongated aggregates (line type) but never into extended pure gA domains. When gA concentrations were increased, for bilayers with 16 carbons or less, gA aggregated into larger domains but the basic unit remained separated by lipid molecules. At about 5 mol % gA, a percolation-like transition occurred at which the line type aggregates were connected to each other. However, for bilayers with more than 16 carbons, multiple lamellar structures were formed at higher gA fractions and the top layer had a ripple-like surface morphology. The molecular mechanism for the formation of these peculiar structures remains to be elucidated.
E.a. Disalvo - One of the best experts on this subject based on the ideXlab platform.
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Determination of the dimerization constant of merocyanine 540 at the membrane interface of lipid vesicles in the Gel State.
Chemistry and Physics of Lipids, 1996Co-Authors: D.l. Bernik, E.a. DisalvoAbstract:Abstract In the present work, the dimerization of merocyanine 540 (MC540) at the interface of DPPC bilayers in Gel State is investigated using a method by which the amount of probe remaining in the aqueous phase is negligible. A procedure is developed in order to demonstrate that monomer-dimer equilibrium takes place only in the membrane phase. In these conditions, absorption and emission studies show that the apparent dimerization constant is strongly dependent on the volume of lipid phase present in the dispersion. The correction by volume lipid fraction brings the dimerization constants within the order of that estimated in pentanol. The corrected Kd values increase with increasing vesicle diameter, thus indicating that the lipid interface of multilamellar liposomes, large unilamellar vesicles and sonicated vesicles have different solvent properties. This is congruent with the finding that the MC 540 dimer is fluorescent in Gel State membranes suggesting that the environment for the dimer is different to that found in water or in fluid membranes in which it is non-fluorescent.
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Effect of H-Bonding Compounds on the Adsorption of Ca2+ to Lipid Membranes in the Gel State
Journal of Colloid and Interface Science, 1995Co-Authors: A.c. Biondi, J. Arroyo, S. Diaz, E.a. DisalvoAbstract:Abstract The binding of Ca 2+ to dipalmitoylphosphatidylcholine (DPPC) bilayers in the Gel State is studied by determination of the spectroscopical features of merocyanine 540. The procedure is based on the measurement of the effect produced by the extent of the binding on the membrane surface. In the range between 0 and 5 m M Ca 2+ a peak at 450 nm is obtained which disappears with the inclusion of cholesterol in a 1:1 ratio. The maximum of absorbance at 450 nm is obtained at around 2.5 m M , which is coincident with the critical concentration of Ca 2+ promoting a drastic transition in the interbilayer distance as reported in the literature. Glycerol, sucrose, glucose, and ribose decrease the intensity of the peak corresponding to the number of OH groups present in each compound. For 0.5 m M Ca 2+ , the 450 nm absorbance intensity shows a maximum at 30°C, which is absent in the presence of cholesterol. Based on the results in a previous paper (Bernik, D. L., and Disalvo, E. A., Biochim. Biophys. Acta 1146, 169, 1993) which demonstrated that the absorbance at 450 nm indicates the presence of Pβ phase in dimyristoylphatidylcholine (DMPC) bilayers, the magnitude of the 450 nm peak as a function of Ca 2+ was taken as an indication that Ca 2+ adsorption induces similar surface properties on DPPC membranes in the Gel State. This action appears to be counteracted by hydrogen bonding compounds included in the membrane or in the aqueous phase.
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Gel State surface properties of phosphatidylcholine liposomes as measured with merocyanine 540.
Biochimica et biophysica acta, 1993Co-Authors: Delia L. Bernik, E.a. DisalvoAbstract:Abstract The surface properties of liposomes composed by saturated phosphatidylcholines and their mixtures with cholesterol in the Gel State have been studied using merocyanine 540 as a fluorescent and optical probe. A new absorption peak at 450 nm and a new fluorescent band at 630 nm were observed when the dye was added to suspensions of DMPC multilamellar liposomes in the Gel State. These peaks were also observed in membranes with different lipid compositions in which the Pβ′ and the Lβ′ phases were present. The increase of temperature above the main transition temperature of DMPC or the incorporation of 35% cholesterol into DMPC bilayers at 13°C caused the disappearance of these peaks. The changes in the absorption and fluorescent spectra upon addition of cholesterol resembles very well the phase diagrams reported by Mortensen et al. ((1988) Biochim. Biophys. Acta 945, 221–245) indicating that the corrugated structures characteristic of the Lβ′ and the Pβ′ phases have different surface properties related to the partitioning of amphiphilic dies.
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Properties of Gel phase lipid-trehalose bilayers upon rehydration
Biochimica et biophysica acta, 1993Co-Authors: L.i. Viera, S. Alonso-romanowski, V. Borovyagin, M.r. Feliz, E.a. DisalvoAbstract:When dipalmitoylphosphatidylcholine bilayers dried under vacuum in different concentrations of trehalose are rehydrated in buffer without the sugar they show different physicochemical properties in the Gel State in comparison to the normal Gel State. Dry DPPC/trehalose mixtures are readily dispersed in buffer below the phase transition showing by electron microscopy a morphology similar to liposomes prepared by dispersing the lipids in buffer above the phase transition temperature. In these conditions, an increase in the peak at 570 nm of merocyanine after the dehydration-rehydration process in the presence of the sugar is observed and the water permeation increases to values comparable to those found in the fluid State as indicated by the activation energy values and the osmotic volume. The trehalose-dried liposomes rehydrated in buffer show a similar osmotic response to hypertonic gradient as DPPC liposomes without sugar near the phase transition temperature. In accordance with this behavior the trehalose-dried liposomes are lysed below the phase transition temperature by lysoderivatives. These modifications of the Gel State of hydrated phospholipids by trehalose can only be achieved if a drastic dehydration is performed in the presence of the sugar. After rehydration the changes in the Gel State can be detected after dyalizing the rehydrated membranes in media without trehalose during at least 24 h. These results suggest that trehalose is still intercalated between the phospholipids after restoring water to the dried liposomes either at temperatures below or above the phase transition.
