Electrical conduction through molecules depends critically on the delocalization of the molecular electronic orbitals and their connection to the metallic contacts. Thiolated (- SH) conjugated organic molecules are therefore considered good candidates for molecular conductors1,2: in such molecules, the orbitals are delocalized throughout the molecular backbone, with substantial weight on the sulphur–metal bonds1,2,3,4. However, their relatively small size, typically ∼1 nm, calls for innovative approaches to realize a functioning single-molecule device5,6,7,8,9,10,11. Here we report an approach for contacting a single molecule, and use it to study the effect of localizing groups within a conjugated molecule on the electrical conduction. Our method is based on synthesizing a dimer structure, consisting of two colloidal gold particles connected by a dithiolated short organic molecule12,13, and electrostatically trapping it between two metal electrodes. We study the electrical conduction through three short organic molecules: 4,4′-biphenyldithiol (BPD), a fully conjugated molecule; bis-(4-mercaptophenyl)-ether (BPE)14, in which the conjugation is broken at the centre by an oxygen atom; and 1,4-benzenedimethanethiol (BDMT), in which the conjugation is broken near the contacts by a methylene group. We find that the oxygen in BPE and the methylene groups in BDMT both suppress the electrical conduction relative to that in BPD.
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This work was supported by the Minerva foundation. We thank R. Popovitz for assistance in obtaining the TEM image (Fig. 1f).
Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.
Measurements of the conductance of single colloids shown in the Vds-Vg plane. (PDF 4836 kb)
A comparison between the conductance spectra of a single colloid and a dimer. (PDF 1516 kb)
Text to accompany the above Supplementary Figures. (DOC 19 kb)
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Dadosh, T., Gordin, Y., Krahne, R. et al. Measurement of the conductance of single conjugated molecules. Nature 436, 677–680 (2005). https://doi.org/10.1038/nature03898
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