A Light Switch in SWNTs

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Science  19 Oct 2007:
Vol. 318, Issue 5849, pp. 363
DOI: 10.1126/science.318.5849.363a

Although most realizations of molecular electronics make use of metallic leads, single-walled carbon nanotubes (SWNTs) can also serve as contacts. Oxidative cutting leaves carboxylate-decorated ends that can be covalently linked to diamine molecules so that the SWNT is reconnected through the molecule via amide linkages. Whalley et al. now use this approach to study ethene-bridged dithiophene and dipyrrole derivatives that photoconvert from ring-opened to ring-closed forms. Ultraviolet irradiation of the ring-opened thiophene derivative created a conjugated ring-closed form that was 25 times more conductive. Unlike the case for molecules bridging gold break-junction electrodes, neither visible light exposure nor heating recovered the open isomer, which the authors attribute to the greater energy dissipation from the excited state in this system. The pyrrole derivative could be thermally switched back, and showed a staircase rise in conductance with ultraviolet light exposure that was attributed to the presence of several molecules bridging the SWNT gap. — PDS

J. Am. Chem. Soc. 129, 10.1021/ja073127y (2007).

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