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Importance of Electrostatic Interactions in The Mobility of Cations in Nafion

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Title Importance of Electrostatic Interactions in The Mobility of Cations in Nafion
 
Creator IYER, ESS
DATTA, A
 
Subject FUEL-CELL MEMBRANES
NORMALIZED EMISSION-SPECTROSCOPY
ION-EXCHANGE MEMBRANES
STATE PROTON-TRANSFER
PERFLUORINATED IONOMER
REVERSE MICELLES
ROOM-TEMPERATURE
WATER DYNAMICS
TRANSPORT
CONDUCTIVITY
 
Description A molecular level understanding of the mobility of cations in the Nafion membrane has been attempted, using the excited state proton transfer (ESPT) process in the fluorescent probe Coumarin 102. ESPT is hindered significantly upon decreasing the water content. Using TRANES (time-resolved area normalized emission spectroscopy), the evolution of the ESPT state is clearly observed over hundreds of picoseconds in lower water content, implying that ESPT is hindered even in the nanovolume probed by the dye. Most remarkably, in the partially dried membrane, the predominant fluorescent species is the zwitterionic form, generated by excited state deprotonation of the cationic form. This implies that the molecule loses a proton from its nitrogen center in the excited state, as usual, but cannot recapture it readily at the oxygen center, at low water contents. This phenomenon is rationalized in light of an increased electrostatic attraction that is experienced by cations upon drying.
 
Publisher AMER CHEMICAL SOC
 
Date 2012-06-26T09:04:47Z
2012-06-26T09:04:47Z
2011
 
Type Article
 
Identifier JOURNAL OF PHYSICAL CHEMISTRY B,115(27)8707-8712
1520-6106
http://dx.doi.org/10.1021/jp203814b
http://dspace.library.iitb.ac.in/jspui/handle/100/14254
 
Language English