Solubilization of pyrene in aqueous micellar solutions of quaternary ammonium gemini surfactants C-12-S-C-12 center dot 2Br has been examined by UV spectra and steady fluorescence spectra at 30 degrees C. The results showed that pyrene molecules were incorporated in the palisade layers of the micelles and interacted with the quarterary ammonium head groups through cation-pi interaction, resulting in red shift of the UV absorption spectrum. C-12-S-C-12 center dot 2Br (s = 3, 4, 6) micelles have stronger ability for solubilization of pyrene than conventional surfactant C(12)TABr micelles. With increasing spacer length Of C-12-s-C-12 center dot 2Br, the micelles become more adaptable to solubilizing pyrene, which even forms the dimers as in the case of s = 3. 4, 6, while pyrene solubilizes in the micelles (s = 2) mainly in single-molecule form due to the more compact structure of the micelle in comparison with that at s > 2. (c) 2006 Elsevier Inc. All rights reserved.