The Experts below are selected from a list of 6726 Experts worldwide ranked by ideXlab platform
Wonyong Lee - One of the best experts on this subject based on the ideXlab platform.
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amperometric glucose biosensor based on sol gel derived metal oxide Nafion composite films
Analytica Chimica Acta, 2005Co-Authors: Han Nim Choi, Min Ah Kim, Wonyong LeeAbstract:Abstract Amperometric glucose biosensors have been developed based on the encapsulation of glucose oxidase in the nanoporous composite films of sol–gel-derived metal oxide (titania and silica) and perfluorosulfonated ionomer, Nafion, on a platinized glassy carbon electrode. The presence of Nafion Polymer in the sol–gel-derived metal oxide not only prevents the cracking of the pure sol–gel-derived metal oxide film but also improves the sensitivity and long-term stability of the biosensor. Analytical performance of the glucose biosensor based on the titania/Nafion composite is superior to that of the biosensor based on the silica/Nafion composite in terms of response time, sensitivity, and long-term stability. The glucose biosensor based on the titania/Nafion composite film can reach 95% of steady-state current less than 2 s. The biosensor responds to glucose linearly up to 7 mM with a sensitivity of 15 μA/mM. The biosensor retained 80% of its initial activity after 4 months of storage in 0.05 M phosphate buffer at pH 7. Sol–gel-derived titania/Nafion composite can also be used for the preparation of second-generation (mediator-based) biosensor by immobilizing the positively charged mediator such as N , N ′-dimethylaminomethyl ferrocene in the composite film via electrostatic and hydrophobic interactions.
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amperometric phenol biosensor based on sol gel silicate Nafion composite film
Analytica Chimica Acta, 2003Co-Authors: Min Ah Kim, Wonyong LeeAbstract:Abstract An amperometric biosensor based on tyrosinase immobilized in silicate/Nafion composite film has been developed for the determination of phenolic compounds. The Nafion Polymer in the composite was used not only to overcome the brittleness of the pure sol–gel-derived silicate film but also to increase the long-term stability of the biosensor. Tyrosinase was immobilized by a thin film of silicate/Nafion composite on a glassy carbon electrode. Phenolic compounds were determined by the direct reduction of biocatalytically-liberated quinone species at −200 mV versus Ag/AgCl (3 M NaCl). The process parameters for the fabrication of the enzyme electrode and various experimental variables such as pH and operating potential were explored for optimum analytical performance of the enzyme electrode. The biosensor can reach 95% of steady-state current in about 15 s. The sensitivities of the biosensor for catechol and phenol were 200 and 46 mA/M, respectively. A detection limit of 0.35 mM catechol was obtained with a signal-to-noise ratio of 3. The enzyme electrode retained 74% of its initial activity after 2 weeks of storage in 50 mM phosphate buffer at pH 7.
Paisan Kongkachuichay - One of the best experts on this subject based on the ideXlab platform.
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homogeneous Polymer filler composite membrane by spraying method for enhanced direct methanol fuel cell performance
International Journal of Hydrogen Energy, 2018Co-Authors: Paweena Prapainainar, Stuart M Holmes, Chaiwat Prapainainar, Sumanut Maliwan, Kannikar Sarakham, Paisan KongkachuichayAbstract:Abstract In this work, composite membranes for a direct methanol fuel cell (DMFC) were prepared using a spraying method to improve cell performance especially at a high methanol concentration. Nafion Polymer and mordenite as a filler were used for the composite membrane preparation using a spraying method and a conventional solution casting method and the membranes from the two methods were compared. SEM images showed that a more homogeneous composite membrane could be obtained using the spraying method. The effect of mordenite content was also studied. The membranes were consequently characterized and tested in DMFC operation. The results were compared to those prepared using the solution casting method at 30, 50, and 70 °C with methanol concentrations of 2, 4, and 8 M. It was found that the membrane with 5 wt.% mordenite from the spraying method showed a vast improvement in DMFC performance. When the cell was operated at 70 °C, the maximum power density of 5 wt.% mordenite from the spraying method was higher than that of commercial membrane and 5 wt.% from the solution casting method. Power densities from the 5 wt.% sprayed membrane were higher by around 29%, 40%, and 60% at 2, 4, and 8 M methanol concentration, respectively.
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Nafion analcime and Nafion faujasite composite membranes for Polymer electrolyte membrane fuel cells
Chemical Engineering Research & Design, 2010Co-Authors: Paisan Kongkachuichay, Siraprapa PimpromAbstract:Abstract The Nafion/zeolite composite membranes were synthesized for Polymer electrolyte fuel cells (PEMFCs) by adding zeolite in the matrix of Nafion Polymer. Two kinds of zeolites, Analcime and Faujasite, having different Si/Al ratio were used. The physico-chemical properties of the composite membranes such as water uptake, ion-exchange capacity, hydrogen permeability, and proton conductivity were determined. The fabricated composite membranes showed the significant improvement of all tested properties compared to that of pure Nafion membrane. The maximum proton conductivity of 0.4373 S cm −1 was obtained from Nafion/Analcime (15%) at 80 °C which was 6.8 times of pure Nafion (0.0642 S cm −1 at 80 °C). Conclusively, Analcime exhibited higher improvement than Faujasite.
Suobo Zhang - One of the best experts on this subject based on the ideXlab platform.
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an enhanced proton conductivity and reduced methanol permeability composite membrane prepared by sulfonated covalent organic nanosheets Nafion
International Journal of Hydrogen Energy, 2019Co-Authors: Jin Yao, Ziming Zhao, Jing Guo, Weiwei Cai, Suobo ZhangAbstract:Abstract Sulfonated covalent organic nanosheets (SCONs) with a functional group (−SO3H) are effective at reducing ion channels length and facilitating proton diffusion, indicating the potential advantage of SCONs in application for proton exchange membranes (PEMs). In this study, Nafion-SCONs composite membranes were prepared by introducing SCONs into a Nafion membrane. The incorporation of SCONs not only improved proton conductivity, but also suppressed methanol permeability. This was due to the even distribution of ion channels, formed by strong electrostatic interaction between the well dispersed SCONs and Nafion Polymer molecules. Notably, Nafion-SCONs-0.6 was the best choice of composite membranes. It exhibited enhanced performance, such as high conductivity and low methanol permeability. The direct methanol fuel cell (DMFC) with Nafion-SCONs-0.6 membrane also showed higher power density (118.2 mW cm−2), which was 44% higher than the cell comprised of Nafion membrane (81.9 mW cm−2) in 2 M methanol at 60 °C. These results enabled us to work on building composite membranes with enhanced properties, made from nanomaterials and Polymer molecules.
Min Ah Kim - One of the best experts on this subject based on the ideXlab platform.
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amperometric glucose biosensor based on sol gel derived metal oxide Nafion composite films
Analytica Chimica Acta, 2005Co-Authors: Han Nim Choi, Min Ah Kim, Wonyong LeeAbstract:Abstract Amperometric glucose biosensors have been developed based on the encapsulation of glucose oxidase in the nanoporous composite films of sol–gel-derived metal oxide (titania and silica) and perfluorosulfonated ionomer, Nafion, on a platinized glassy carbon electrode. The presence of Nafion Polymer in the sol–gel-derived metal oxide not only prevents the cracking of the pure sol–gel-derived metal oxide film but also improves the sensitivity and long-term stability of the biosensor. Analytical performance of the glucose biosensor based on the titania/Nafion composite is superior to that of the biosensor based on the silica/Nafion composite in terms of response time, sensitivity, and long-term stability. The glucose biosensor based on the titania/Nafion composite film can reach 95% of steady-state current less than 2 s. The biosensor responds to glucose linearly up to 7 mM with a sensitivity of 15 μA/mM. The biosensor retained 80% of its initial activity after 4 months of storage in 0.05 M phosphate buffer at pH 7. Sol–gel-derived titania/Nafion composite can also be used for the preparation of second-generation (mediator-based) biosensor by immobilizing the positively charged mediator such as N , N ′-dimethylaminomethyl ferrocene in the composite film via electrostatic and hydrophobic interactions.
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amperometric phenol biosensor based on sol gel silicate Nafion composite film
Analytica Chimica Acta, 2003Co-Authors: Min Ah Kim, Wonyong LeeAbstract:Abstract An amperometric biosensor based on tyrosinase immobilized in silicate/Nafion composite film has been developed for the determination of phenolic compounds. The Nafion Polymer in the composite was used not only to overcome the brittleness of the pure sol–gel-derived silicate film but also to increase the long-term stability of the biosensor. Tyrosinase was immobilized by a thin film of silicate/Nafion composite on a glassy carbon electrode. Phenolic compounds were determined by the direct reduction of biocatalytically-liberated quinone species at −200 mV versus Ag/AgCl (3 M NaCl). The process parameters for the fabrication of the enzyme electrode and various experimental variables such as pH and operating potential were explored for optimum analytical performance of the enzyme electrode. The biosensor can reach 95% of steady-state current in about 15 s. The sensitivities of the biosensor for catechol and phenol were 200 and 46 mA/M, respectively. A detection limit of 0.35 mM catechol was obtained with a signal-to-noise ratio of 3. The enzyme electrode retained 74% of its initial activity after 2 weeks of storage in 50 mM phosphate buffer at pH 7.
Mu Pan - One of the best experts on this subject based on the ideXlab platform.
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a degradation study of Nafion proton exchange membrane of pem fuel cells
Journal of Power Sources, 2007Co-Authors: Haolin Tang, Shen Peikang, San Ping Jiang, Fang Wang, Mu PanAbstract:Abstract The durability and degradation behavior of the Nafion NR111 proton exchange membranes (PEMs) is investigated in detail under various mechanical, chemical and polarization conditions. It was found that the fatigue strength or the safety limit of the cyclic stress for Nafion NR111 membrane is ∼1.5 MPa that is 1/10 of the tensile strength of the membrane. The cyclic stress and dimensional change (or strain) induced by the water uptake can be substantial and are the main causes for the mechanical degradation and failure of the membrane. For example, in the case of RH cycling of water soaked state to 25% RH state, the cyclic stress of the Nafion membrane was as high as 2.23 MPa and the dimensional change was ∼11%. Both FTIR and NMR analysis indicate that the decomposition of the Nafion Polymer in the H 2 O 2 solution in the presence of trace Fe, Cr and Ni ions started from the ends of the main chain, resulting in the loss of the repeat units and the formation of voids and pinholes in the membrane. The high degradation rate of the membrane at the open circuit voltage most likely results from the attack of H 2 O 2 formed between O 2 and H 2 crossovered through the membrane.
