10
views
0
recommends
+1 Recommend
1 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found
      Is Open Access

      Self-assembled films from chitosan and poly(vinyl sulfonic acid) on Nafion® for direct methanol fuel cell

      research-article

      Read this article at

      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          Chitosan/poly(vinyl sulfonic acid) (PVS) films have been prepared on Nafion® membranes by the layer-by-layer (LbL) method for use in direct methanol fuel cell (DMFC). Computational methods and Fourier transform infrared (FTIR) spectra suggest that an ionic pair is formed between the sulfonic group of PVS and the protonated amine group of chitosan, thereby promoting the growth of LbL films on the Nafion® membrane as well as partial blocking of methanol. Chronopotentiometry and potential linear scanning experiments have been carried out for investigation of methanol crossover through the Nafion® and chitosan/PVS/Nafion® membranes in a diaphragm diffusion cell. On the basis of electrical impedance measurements, the values of proton resistance of the Nafion® and chitosan/PVS/Nafion® membranes are close due to the small thickness of the LbL film. Thus, it is expected an improved DMFC performance once the additional resistance of the self-assembled film is negligible compared to the result associated with the decrease in the crossover effect.

          Translated abstract

          Filmes de quitosana/poli(ácido vinilsulfônico) (PVS) foram depositados sobre membranas de Nafion® a partir do método camada por camada (LbL), visando o seu uso em células a combustível de metanol direto (DMFC). Métodos computacionais e espectros de infravermelho com transformada de Fourier (FTIR) sugerem a formação de um par iônico entre o grupo sulfônico do PVS e o grupo amino protonado da quitosana, o qual promove o crescimento dos filmes LbL sobre a membrana de Nafion®, assim como impede parcialmente a passagem de metanol. Experimentos de cronopotenciometria e varredura linear de potencial foram realizados a fim de se investigar a passagem de metanol através das membranas de Nafion® e quitosana/PVS/Nafion® em uma célula a diafragma. Os valores de resistência iônica associada ao transporte de prótons nas membranas de Nafion® e quitosana/PVS/Nafion® são próximos, de acordo com as medidas de impedância elétrica devido à pequena espessura do filme LbL. Assim, espera-se um melhor desempenho da DMFC, uma vez que a resistência do filme automontado é insignificante comparada ao resultado associado à passagem de metanol através das membranas.

          Related collections

          Most cited references24

          • Record: found
          • Abstract: not found
          • Book: not found

          Diffusion

            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Influence of end-capping on the self-assembly of model amyloid peptide fragments.

            The influence of charge and aromatic stacking interactions on the self-assembly of a series of four model amyloid peptides has been examined. The four model peptides are based on the KLVFF motif from the amyloid β peptide, Aβ(16-20) extended at the N terminus with two β-alanine residues. We have studied NH(2)-βAβAKLVFF-COOH (FF), NH(2)-βAβAKLVF-COOH (F), CH(3)CONH-βAβAKLVFF-CONH(2) (CapF), and CH(3)CONH-βAβAKLVFF-CONH(2) (CapFF). The former two are uncapped (net charge +2) and differ by one hydrophobic phenylalanine residue; the latter two are the analogous capped peptides (net charge +1). The self-assembly characteristics of these peptides are remarkably different and strongly dependent on concentration. NMR shows a shift from carboxylate to carboxylic acid forms upon increasing concentration. Saturation transfer measurements of solvent molecules indicate selective involvement of phenylalanine residues in driving the self-assembly process of CapFF due presumably to the effect of aromatic stacking interactions. FTIR spectroscopy reveals β-sheet features for the two peptides containing two phenylalanine residues but not the single phenylalanine residue, pointing again to the driving force for self-assembly. Circular dichroism (CD) in dilute solution reveals the polyproline II conformation, except for F which is disordered. We discuss the relationship of this observation to the significant pH shift observed for this peptide when compared the calculated value. Atomic force microscopy and cryogenic-TEM reveals the formation of twisted fibrils for CapFF, as previously also observed for FF. The influence of salt on the self-assembly of the model β-sheet forming capped peptide CapFF was investigated by FTIR. Cryo-TEM reveals that the extent of twisting decreases with increased salt concentration, leading to the formation of flat ribbon structures. These results highlight the important role of aggregation-induced pK(a) shifts in the self-assembly of model β-sheet peptides.
              Bookmark
              • Record: found
              • Abstract: not found
              • Article: not found

              J. Nanosci. Nanotechnol.

                Bookmark

                Author and article information

                Contributors
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Journal
                jbchs
                Journal of the Brazilian Chemical Society
                J. Braz. Chem. Soc.
                Sociedade Brasileira de Química (São Paulo )
                1678-4790
                March 2012
                : 23
                : 3
                : 531-537
                Affiliations
                [1 ] Faculdades COC Brazil
                [2 ] Universidade de São Paulo Brazil
                Article
                S0103-50532012000300021
                10.1590/S0103-50532012000300021
                7022daa9-335f-4ac5-adf1-bed0b1d1713f

                http://creativecommons.org/licenses/by/4.0/

                History
                Product

                SciELO Brazil

                Self URI (journal page): http://www.scielo.br/scielo.php?script=sci_serial&pid=0103-5053&lng=en
                Categories
                CHEMISTRY, MULTIDISCIPLINARY

                General chemistry
                chitosan,direct methanol fuel cell,proton exchange membrane,crossover effect,methanol permeability

                Comments

                Comment on this article