Fluorescence Quenching of Pyrene by Chromium Complexes in Sodium Dodecyl Sulfate Micelles

Abstract

Abstract The aggregation number of sodium dodecylsulfate (SDS) is known to vary with its concentration. Keeping the SDS concentration fixed at 15, 50, and 100 mM, the effect of various Cr(III) quenchers on the aggregation behavior of SDS was studied using pyrene as a probe during static and time-resolved fluorescence measurements. Cr(III) compounds, such as [Cr(en)3]Cl3, [Cr(salprn)(H2O)2]+, [Cr(phen)3](ClO4)3, and [Cr(bpy)3](ClO4)3 were used as quenchers in this investigation. Cetylpyridinium chloride (CPC) was also used as a quencher to keep the Cr(III) complexes fixed at 0.05 and 0.1 mM in order to further confirm the aggregation behavior of SDS micelles in the presence of various ligands. The aggregation numbers of SDS are very low (2 to 32) when the ligand is aliphatic, whereas they are surprisingly high (75—860) in the presence of Schiff-base and aromatic ligand environments. The aliphatic ligand acts as a structure breaker, whereas Schiff-base and aromatic ligands act as structure makers for aggregated SDS micelles, which have been further substantiated by lower and higher counterion association values, respectively, obtained from conductivity experiments.