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7631221 
Journal Article 
DYNAMICS OF THE QUENCHING OF PYRENE FLUORESCENCE BY THE THIOSULFATE ION IN CATIONIC MICELLES 
Alonso, EO; Quina, FH; , 
1995 
Yes 
Journal of the Brazilian Chemical Society
ISSN: 0103-5053
EISSN: 1678-4790 
SOC BRASILEIRA QUIMICA 
SAO PAULO 
155-159 
WOS:A1995RF70900007 
Time resolved fluorescence decay measurements with pyrene as probe have been employed to study the dynamics of intramicellar quenching and exit of the thiosulfate counterion (S2O32-) from micelles of hexadecyltrimethylammonium chloride (CTACl) over a wide range of concentration of CTACl and added common counterion salt (NaCl). The rate constant k(q) for intramicellar quenching of an excited pyrene in a micelle containing a single S2O32- quencher counterion is 9 (+/-2) 10(6) s(-1), independent of either [CTACl] or [NaCl]. The rate constant k for micellar exit of S2O32- is governed by the micellar surface potential, the effective free energy barrier for escape of S2O32- from the CTACl micelle being equivalent to about half of the overall electrostatic work for complete transfer of the thiosulfate ion from the micelle surface to the aqueous phase.