IN-SITU QUARTZ-CRYSTAL MICROGRAVIMETRIC STUDIES OF MOLECULAR ADSORBATES CONTAINING THIOL AND HYDROQUINONE MOIETIES BOUND TO AU(111) SURFACES IN AQUEOUS-ELECTROLYTES

The microgravimetric properties of monolayers of 2,5-dihydroxythiophen ol, 2,5-dihydroxybenzyl mercaptan, and 2,5-dihydroxy-4-methylbenzyl me rcaptan adsorbed on Au(111) single crystal electrodes were examined by in situ quartz crystal microbalance techniques in aqueous perchloric acid electrolytes. The results obtained are consistent with the revers ible loss of an average of about three waters per adsorbed molecule as the layers are oxidized and subsequently reduced. These observations provide evidence for discrete changes in the extent of bound water wit hin the hydroquinone/quinone layer as the oxidation state of the monol ayer is changed.