Electron transport properties of a carotene molecule in a metal-(single molecule)-metal junction

Ganesh K. Ramachandran, John K. Tomfohr, Jun Li, Otto F. Sankey, Xristo Zarate, Alex Primak, Yuichi Terazono, Thomas Moore, Ana Moore, Devens Gust, Larry A. Nagahara, Stuart Lindsay

Research output: Contribution to journalArticlepeer-review

108 Scopus citations


Using a recently developed method for tethering gold contacts to single molecules, we have measured current versus voltage (I-V) data for single carotenedithiol molecules with a total length of 28 carbons (18 in the conjugated alkene chain). The molecules are inserted into a docosanethiol monolayer (C22H45SH) on Au(111), and a Au nanoparticle is tethered to each molecule via the protruding thiol group. Electrical contact is made by placing a gold-coated AFM probe in contact with the nanoparticle. The I-V curves are relatively insensitive to contact probe force and cluster around integer multiples of a fundamental curve, suggesting that members of the smallest set correspond to data obtained from a single molecule. First principles calculations based on tunnel transport yield results that are remarkably close (within a factor of 4) to the measured data. The remaining small discrepancy can be well accounted for by taking account of the effects of charging caused by a probe-to-gold particle contact resistance. Thus, it appears that electron tunneling dominates transport even in this 3-nm-long molecule. The carotenoid is a better conductor than a saturated n-alkane of equivalent length by a very large factor and is significantly more conductive than 2,5-di(phenylethynyl-4′-thioacetyl)benzene, another candidate "molecular wire".

Original languageEnglish (US)
Pages (from-to)6162-6169
Number of pages8
JournalJournal of Physical Chemistry B
Issue number25
StatePublished - Jul 26 2003

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry


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