Dynamic behaviour of fluorescence quenchers in cetyltrimethylammonium chloride micelles

Abstract

The kinetics of quenching of the fluorescence of pyrene solubilized in cetyltrimethylammonium chloride (CTAC) micelles by three different types of quenchers [pyrene or cetylpyridinium chloride (immobile quenchers), dodecylpyridinium chloride (mobile, hydrophobic quencher) and iodide ion (mobile, hydrophilic quencher)] has been investigated by means of time-resolved fluorescence measurements. The results obtained with the two immobile quenchers have permitted the first determination of the mean micellar aggregation number N of CTAC at high concentration up to 1.2 mol dm^–3. These N-values have then been used for a quantitative evaluation of the kinetic and equilibrium quenching parameters for the other two types of quenchers. The results concerning the quenching by the iodide ion are discussed on the basis of the available models proposed for this type of quenching. They appear to favour the electrostatic model of Almgren et al.