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Issue 8, 2012
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Edge effects control helical wrapping of carbon nanotubes by polysaccharides

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Abstract

Carbon nanotubes (CNTs) wrapped by polysaccharide chains via noncovalent interactions have been shown to be soluble and dispersed in aqueous environments, and have several potential chemical and biomedical applications. The wrapping mechanism, in particular the role played by the end of the CNT, remains, however, unknown. In this work, a hybrid complex formed by an amylose (AMYL) chain and a single-walled carbon nanotube (SWNT) has been examined by means of atomistic molecular dynamics (MD) simulations to assess its propensity toward self-assembly, alongside its structural characteristics in water. To explore edge effects, the middle and end regions of the SWNT have been chosen as two initial wrapping sites, to which two relative orientations have been assigned, i.e. parallel and orthogonal. The present results prove that AMYL can wrap spontaneously around the tubular surface, starting from the end of the SWNT and driven by both favorable van der Waals attraction and hydrophobic interactions, and resulting in a perfectly compact, helical conformation stabilized by an interlaced hydrogen-bond network. Principal component analysis carried out over the MD trajectories reveals that stepwise burial of hydrophobic faces of pyranose rings controlled by hydrophobic interactions is a key step in the formation of the helix. Conversely, if wrapping proceeds from the middle of the SWNT, self-organization into a helical structure is not observed due to strong van der Waals attractions preventing the hydrophobic faces of the AMYL chain generating enough contacts with the tubular surface.

Graphical abstract: Edge effects control helical wrapping of carbon nanotubes by polysaccharides

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Publication details

The article was received on 13 Dec 2011, accepted on 19 Feb 2012 and first published on 24 Feb 2012


Article type: Paper
DOI: 10.1039/C2NR11979J
Citation: Nanoscale, 2012,4, 2584-2589
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    Edge effects control helical wrapping of carbon nanotubes by polysaccharides

    Y. Liu, C. Chipot, X. Shao and W. Cai, Nanoscale, 2012, 4, 2584
    DOI: 10.1039/C2NR11979J

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