Electrochemical Detection of Single Molecules

Science  10 Feb 1995:
Vol. 267, Issue 5199, pp. 871-874
DOI: 10.1126/science.267.5199.871


The electrochemical behavior of a single molecule can be observed by trapping a small volume of a dilute solution of the electroactive species between an ultramicroelectrode tip with a diameter of ∼ 15 nanometers and a conductive substrate. A scanning electrochemical microscope was used to adjust the tip-substrate distance (∼10 nanometers), and the oxidation of [(trimethylammonio)methyl] ferrocene (Cp2FeTMA+) to Cp2FeTMA2+ was carried out. The response was stochastic, and anodic current peaks were observed as the molecule moved into and out of the electrode-substrate gap. Similar experiments were performed with a solution containing two redox species, ferrocene carboxylate (Cp2FeCOO-) and Os(bpy)32+ (bpy is 2,2'-bipyridyl).