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8247908 
Journal Article 
Fluorescence Probes for Critical Micelle Concentration 
Ananthapadmanabhan, KP; Goddard, ED; Turro, NJ; Kuo, PL 
1985 
1 
Langmuir
ISSN: 0743-7463
EISSN: 1520-5827 
1 
3 
352-355 
English 
21370917 
The utility of pyrene and pyrene-3-carboxaldehyde as fluorescence probes for determining the critical micelle concentration (cmc) of nonionic (Tergitol 25-L-9, Tergitol 15-S-40, Neodol 91–8), anionic (sodium decyl sulfate), and cationic (cetyltrimethylammonium bromide) surfactants was investigated. The probes were dissolved in trace amounts (<10-6 kmol/m3) in a series of aqueous solutions of these surfactants. Results obtained indicated that the surfactant concentration at which a marked decrease in the λmax parameter of pyrene-3-carboxaldehyde occurs corresponds to the cmc determined by surface tension. In contrast, the customarily used parameter, I1/I3, of pyrene undergoes a reduction at concentrations close to, but consistently lower than, the accepted cmc values of the surfactant. Thus, it appears that pyrene-3-carboxaldehyde is the more reliable probe for cmc determination. Surface tension results show, furthermore, that the probe molecules at the levels used to determine the cmc by fluorescence do not noticeably affect the surfactant properties, viz., surface tension, nor the surface tension derived cmc value. © 1985, American Chemical Society. All rights reserved.