Scaffolding carbon nanotubes into single-molecule circuitry
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Scaffolding carbon nanotubes into single-molecule circuitry Brett R. Goldsmith Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697
John G. Coroneus Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, California 92697
Jorge A. Lamboy Department Chemistry, University of California, Irvine, Irvine, California 92697
Gregory A. Weiss Department of Molecular Biology and Biochemistry and Department of Chemistry, University of California, Irvine, Irvine, California 92697
Philip G. Collinsa) Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697 (Received 6 November 2007; accepted 20 February 2008)
While nanowires and nanotubes have been shown to be electrically sensitive to various chemicals, not enough is known about the underlying mechanisms to control or tailor this sensitivity. By limiting the chemically sensitive region of a nanostructure to a single binding site, single molecule precision can be obtained to study the chemoresistive response. We have developed techniques using single-walledcarbon-nanotube (SWCNT) circuits that enable single-site experimentation and illuminate the dynamics of chemical interactions. Discrete changes in the circuit conductance reveal chemical processes happening in real-time and allow SWCNT sidewalls to be deterministically broken, reformed, and conjugated to target species.
I. INTRODUCTION
Chemical, biological, and even mechanical sensor prototypes are all currently being explored as possible applications for carbon nanotube (CNT) devices.1 In each case, researchers attempt to exploit the exquisite sensitivity of carbon nanotubes while directing this sensitivity toward a particular target. Because pristine CNTs and as-fabricated devices have cross sensitivities to a wide range of adsorbates, including air and water, control over selectivity is a critical research problem. CNT functionalization techniques, in which sensitizing groups are added to a CNT, provide promising solutions to both enhancing sensitivity and directing selectivity. Both noncovalent coatings and covalent sidewall modifications a)
Address all correspondence to this author. e-mail: [email protected] This paper was selected as the Outstanding Symposium Paper for the 2007 MRS Spring Meeting Symposium EE Proceedings, Vol. 1018E. DOI: 10.1557/JMR.2008.0179 J. Mater. Res., Vol. 23, No. 5, May 2008
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have been used to engineer the electronic properties and environmental sensitivities of CNTs, at least in bulk or on films of networked CNTs.2–6 While additions of chemical groups along a CNT certainly do lead to sensitivity enhancements, they also result in an ensemble measurement of the environment and do not take advantage of a CNT’s dimensionality, in particular the one-dimensional (1D) nature of singlewalled carbon nanotubes (SWCNTs). The response of a 1D conductor like a SWCNT may be dominated by a single scattering site,7–11 making such c
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