Adsorbed Molecules on the March

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Science  25 Feb 2000:
Vol. 287, Issue 5457, pp. 1365
DOI: 10.1126/science.287.5457.1365g

An electrode placed into solution is supposed to be the same potential everywhere along its surface. Terrill et al. deliberately break this rule by using thin (and hence resistive) gold films (5 to 80 nanometers thick) on glass microscope slides as electrodes. By passing current through the film, they established voltage gradients of tens of millivolts per millimeter, which they then used to create gradients in the coverage of octanethiol monolayers electrodeposited from solution. Coadsorption of 3-mercaptopropionic acid on the remaining bare surface created a gradient in surface energy. The voltage gradient itself could be shifted with a potentiostat along the gold electrode, and thus the thiol film gradient could be shifted on the film while it remained in solution (as verified by surface plasmon resonance imaging). Applications might include transporting larger supramolecular objects attached to the thiols or exploiting surface tension gradients for fluid pumping.—PDS

J. Am. Chem. Soc.122, 988 (2000).

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