Abstract: The location of phenothiazine in SDS/BA/H2O microemulsion was investigated by cyclic voltammetric and fluorescence quenching method.In O/W microemulsion,phenothiazine has two oxidation peaks.Because the peak potentials are independent of the sweep rate ( Fig.1 ) and all the peak currents are proportional to the square root of the potential sweep rate ( Fig.2 ),the electrochemical process for phenothiazine is reversible.According to the peak separation between the peak potentials in the positive and negative scans and the Nernstian equation,the above cyclic voltammetric characteristics for all peaks are of one - electron process.Since the process of the radical cation PTZ＋•losing an electron to form PTZ2＋ needs much more energy (≈0.4 V ) and there is only about 0.13 V between the two peaks ( table 1,Fig.1 ),the two peaks are both produced by the process of PTZ molecule losing an electron.In PTZ molecules,there are two polar groups with the S and N atoms as center,respectively.Thus,the phenothiazine molecules exist in the membrane phase with its N atom or S atom extended toward the polar head in the O/W microemulsion.Further experiments found that the fluorescence quenching of anthracene by PTZ in the W/O microemulsion is rather more similar to that in the O/W microemulsion than in pure benzyl alcohol.So,the location of PTZ in the W/O microemulsion is the same as in the O/W microemulsion,i.e.,in the inner side of the membrane phase of the W/O microemulsion.

Key words: Cyclic voltammetry, Fluorescence quenching, Phenothiazine, Microemulsion