Electroactive Self-Assembled Biferrocenyl Alkanethiol Monolayers on Au(111) Surface and on Gold Nanoclusters

The spectroscopic and electrochemical characterizations of electrochemically stable biferrocene-modified Au clusters and chemisorbed biferrocenylalkanethiols on Au(111) surface were studied. The characterizations of biferrocene-modified Au cluster using TEM, UV-vis, and NMR techniques are also reported. Two successive reversible one-electron redox waves were observed for the biferrocenylalkanethiol Au nanoclusters and biferrocenylalkanethiol monolayers on Au(111) surface in the cyclic voltammetry. Furthermore, the positive and negative current peaks for each redox wave occur at almost the same potential, and the peak current increases almost linearly with the sweep rate. Repeat scanning does not change the voltammograms, demonstrating that these monolayers are stable to electrochemical cycling. The coverages of electroactive biferrocene in the monolayers were calculated from the cyclic voltammograms. The standard electron-transfer rate constant was calculated from the splitting between the oxidation and reduction peaks.