Modified Nafion

Y.-M. Zhou, Z.-Y. Wu, G.-L. Shen, and R.-Q. Yu, An amperometric immunosensor based on Nafion-modified electrode for the determination of Schistosoma japonicum antibody. Sensors and Actuators, B Chemical 89, 292-298 (2003). 

Research was done with redox systems incorporated into Nafion-modified electrodes51 because of interesting possible applications of such systems, e.g., for electron-transfer catalysis. 

Nafion modified electrodes (Section 57.3.2.1) have been shown to promote electrogenerated chemiluminescence from the [Ru(bipy)3]2+/oxalate system.44 The problem of the quenching of the eel by water was overcome in the Nafion case since sections of the electrode coating were hydro-phobic. However, aqueous systems continue to be of interest in the development of practical eel devices such as digital display units (see also Section 57.3.2.5(iv)). It has been shown that eel is... 

I. Luiz de Mattos and M. Carneiro da Cunha Areias, Automated determination of glucose in soluble coffee using Prussian Blue-glucose ox-idase-Nafion modified electrode, Talanta, 66(5) (2005) 1281-1286. 

MWCNTs-Nafion nanocomposite. The EDS patterns of MWCNTs-Nafion nanocomposite before and after electrochemical deposition of Ag nanoparticles are shown in Fig. 6.2a, b, respectively. It indicates that C is the major element which is derived from MWCNTs and Nation. The Ag element can be identified in Fig. 6.2b after the electrochemical deposition of Ag nanoparticles. The prepared Ag-MWCNTs-Nafion nanocomposite was used to detect the typical SERS active probe molecule such as R6G. For the determination, the Ag-MWCNTs-Nafion-nanocomposite-modified ITO substrates were placed on the bottom of a liquid cell with 35 mF aqueous solution. Two control experiments at the Ag-coated and Ag-carbon black (CB)-Nafion-coated ITO substrates were performed for comparison. The Raman spectra of 10 " M R6G in aqueous solution at the surfaces of MWCNTs-Nafion, Ag, Ag-CB-Nafion, and Ag-MWCNTs-Nafion-modified ITO substrates are shown in Fig. 6.3a-d, respectively. The peaks at 1,186, 1,310,... 

MWCNTs-Nafion is a suitable matrix for Ag nanoparticles loading for SERS sensor applications. Different concentrations of R6G were added into the liquid cell in order to evaluate the potential applications of the Ag-MWCNTs-Nafion-nanocomposite-film-modified ITO substrates. Raman spectra of Ag-MWCNTs-Nafion to the additions of varying concentrations of R6G in aqueous solution are shown in Fig. 6.4. It can be seen that the Raman intensities increased with successive addition of R6G. These results demonstrate that R6G can be detected with the Ag-MWCNTs-Nafion substrates. The cahbration curve of Raman peak intensity (at 1,509 cm ) at the Ag-MWCNTs-Nafion-modified ITO substrates to the addition of varying concentrations of R6G in aqueous solution is shown in the inset in Fig. 6.4. The linear range is M with a correlation factor... 

Le Gal La Salle, A. Limoges, B. Rapicault, S. Degrand, C. Brossier, P. New immunoassay techniques using Nafion-modified electrodes and cationic redox labels or enzyme labels. Anal. Chim. Acta 1995, 311, 301-308. 

However, Nafion-modified electrodes also exhibited several disadvantages. For example, the response time of the Nafion-coated sensors increases due to a reduced diffusion coefficient value in the film [7], This can pose a serious disadvantage for in vivo work where dopamine and other neurotransmitter releases often occur on a sub-second time scale. In addition, Nafion coatings perform well for applications such as stripping analysis, but their use for direct voltammetric analysis is complicated by slow equilibration of the film with solution species [5 7], Therefore, there is a need for a modification system that can allow for rapid and selective permeation of the ions of interest. 

Glucose oxidase horseradish peroxidase MWCNT-toluidine blue/ nafion modified GCE Glucose biosensor [114]... 

L. Kavan and M. Gratzel, Nafion modified Ti02 electrodes Photoresponse and sensitization by Ru(II)-bipyridyl compounds, Electrochim. Acta, 1989, 34, 1327— 1334. 

Liu, Y, Yuan, R., et al. Direct electrochemistry of horseradish peroxidase immobilized on gold coUoid/cysteine/nafion-modified platinum disk electrode. Sensors and Actuators B Chemical, 15(1), 109-115 (2006). 

Tazi and Savodogo also incorporated silicatungstic acid (SiWA) and thiophene (TH) in Nafion 117 membrane and demonstrated an improvement in the ionic conductivity and achieved a high power density (Tazi and Savodogo 2001). Water uptake in the Nafion modified with SiWA was 60% and with both SA and TH, it was 40% compared with the normal value of 27% for Nafion 117. Malhotra and Datta impregnated the Nafion membranes with a PTA solution in acetic acid or in molten salt solvent and the resultant membrane could operate up to 110°C-120°C (Malhotra and Datta 1997). 

Au, or Cu) (PDPA, Nafion) (modified electrode) CNTs—conducting component Nobie metai—cataiyst... 

Oxalate Fibre optic based sensor Ru(bpy)3 + immobhized on a Nafion modified electrode Urine, vegetables 3X10-5 M (179) (Continued)... 

Disposable TCNQ-Nafion modified screen-printed electrode coupled to differential pulse voltammetry (DPV)[12] and... 

Kim, D. W., Choi, H.-S., Lee, C., Blumstein, A., and Kang, Y, 2004, Investigation on methanol permeability of Nafion modified by self-assembled clay-nanocomposite multilayers, Electrochim. Acta 50 659-662. 

Trogadas and Ramani summarized the modification of PEM membranes, including Nafion modified by zirconium phosphates, heteropolyacids, hydrogen sulfates, metal oxides, and silica. Membranes with sulfonated non-fluorinated backbones were also described. The base polymers polysulfone, poly(ether sulfone), poly(ether ether ketone), polybenzimidazole, and polyimide. Another interesting category is acid-base polymer blend membranes. This review also paid special attention to electrode designs based on catalyst particles bound by a hydrophobic poly-tetrafluoroethylene (PTFE) structure or hydrophilic Nafion, vacuum deposition, and electrodeposition method. Issues related to the MEA were presented. In then-study on composite membranes, the effects of particle sizes, cation sizes, number of protons, etc., of HPA were correlated with the fuel cell performance. To promote stability of the PTA within the membrane matrix, the investigators have employed PTA supported on metal oxides such as silicon dioxide as additives to Nafion. 

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