2001 Volume 69 Issue 12 Pages 980-983
Self-assembled monolayers (SAMs) of 1-mercaptoanthraquinone (AQSC0), bis(3-(1-anthraquinonylthio)propyl)disulfide (AQSC3), and bis(6-(1-anthraquinonylthio)hexyl) disulfide (AQSC6), on a gold electrode were investigated by cyclic voltammetry and surface enhanced infrared absorption spectroscopy (SEIRAS). A redox wave was observed for all the anthraquinone (AQ) derivatives studied and the redox potential shifted ca. -60 mV pH−1 in the pH region from 1 to 7. The peak separation of the voltammograms depended on the spacer length of the AQ derivatives, and the heterogeneous electron transfer rates of AQSC0, AQSC3, and AQSC6 at pH 1 were 7.5, 2.3×10−1, and 3.1×10−3 s−1, respectively. For the SEIRA spectra of AQSC0 and AQSC3, the C = 0 stretching and C - C stretching bands of the AQ ring are clearly observed, suggesting that the AQ ring plane is perpendicular or tilted to the electrode surface. The SEIRA signal of the AQ derivatives decreased with an increase in the alkyl chain length, indicating that the AQSC3 and AQSC6 molecules are adsorbed on the electrode not by the sulfide S atoms but by the thiolate S atoms.
