Fluorescence Quenching in Microheterogeneous Media: A Laboratory Experiment Determining Micelle Aggregation Number

In the present work we describe a simple procedure for measuring micelle aggregation numbers of surfactants, which has been designed to introduce students to heterogeneous systems and the techniques by which their physical and chemical properties may be determined. This method is based on the spectroscopic properties of molecules acting as "probes" and it provides, the student with additional experience in fluorescence spectroscopy. By using this technique, with sodium dodecyl sulfate as surfactant, cetylpiridinium chloride as quencher, and pyrene as the probe, micelle aggregation numbers in good agreement with published values can be found.