Photon-gated electron transfer in two-component self-assembled monolayers

Daniel G. Walter, Dean J. Campbell, Chad A. Mirkin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

56 Scopus citations


The preparation and characterization of a photoactive, two-component self-assembled monolayer (SAM) consisting of 99:1 cis-p-(C6H5)N=N(C6H4)O(CH 2)11SH) (1) and trans-p,p,Fc(C6H4)N=N(C6H4)(CH 2)4SH (Fc = C5H4FeC5H5; 2) are reported. With this SAM, electron transfer between solution ferrocyanide and the Au substrate is forced to occur through mediating ferrocenyl sites in the film, resulting in a diode-like response. However, by photochemically converting large "footprint" cis-1 to the smaller footprint trans-1, the free volume within the film is increased, thereby allowing for direct electron transfer between the solution ferrocyanide and the electrode surface and a normal electrochemical response (i.e., ipa = ipc). All states of the film have been characterized by cyclic voltammetry, FTIR spectroscopy, and differential capacitance measurements. All data from these techniques are consistent with the conclusion that cis-trans azobenzene isomerization within the monolayer results in increased film porosity, which reduces the film's ability to block the access of solution redox-active species to the underlying Au electrode surface. This novel two-component structure establishes the concept for a new type of molecule-based electronic device, a "photoswitchable diode" that is capable of amplifying the signal associated with a photodriven event via an electrochemical response. With such a system, a small number of photons can release a relatively large number of electrons from the solution electron reservoir. Significantly, this system shows how one can regulate electron-transfer events involving SAMs through photochemical control over film structure and free volume.

Original languageEnglish (US)
Pages (from-to)402-405
Number of pages4
JournalJournal of Physical Chemistry B
Issue number3
StatePublished - Jan 21 1999

ASJC Scopus subject areas

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


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