Abstract: The aggregation behavior of a steroidal surfactant--sodium deoxycholate (SDOC) inaqueous solution was studied by extrinsic fluorescent probe [via twisted intramolecular charge transfer (TICT) fluorescence characteristics of p-N,N-dimethylamminobenzaldehyde, DMABA], optical rotation, conductivity, and pHmeasurement.TICTfluorescence band of DMABAshifts to blue and the fluorescence intensity ratio (Ia/Ib) of TICTband to LEband increases with the increase of SDOCconcentration up to 6.0× 10^-3 mol/L, then the variation trends reversed.These results indicate that the critical micelle concentration of SDOCis 6.0×10^-3 mol/Land that the SDOCmolecules don't exist in monomer but in dimer which provides a hydrophobic microenvironment less polar than that of SDOCmicelle.Fittig the conductivity data of aqueous SDOCsolution yields an average aggregation number of 8-10 for SDOCmicelle which is substantially less than that of normal micelle.Optical rotation and pHmeasurements show that SDOCmicelle has a relatively lower symmetry and stronger basicity than the dimer.

Key words: Aggregation behavior, Sodium deoxycholate, TICT fluorescent probe, Optical rotation, Conductivity