DNA-wrapped carbon nanotubes as a model rod-like colloid system

Ming Zheng (NIST)

Single-wall carbon nanotubes (SWCNTs) exhibit many fascinating physical behavior as the result of their quasi one-dimensional crystalline structures. SWCNTs can be dispersed into rod-like colloid particles by a few small molecules and polymers, among which the most effect one is single-stranded DNA (Nature Materials 2, 338, 2003). The structure of a DNA-SWCNT hybrid is controlled by both the sequence of the wrapping DNA, and the atomic configuration, or chirality, of the SWCNT (Science 302, 1545, 2003). This has been exploited by us to purify single-chirality SWCNTs from synthetic mixtures via liquid chromatography (Nature 460, 250, 2009; JACS 133, 12998, 2011). DNA-SWCNTs have well-defined surface structures, tunable aspect-ratios, and ultra-small diameters. These attributes provide unique advantages to the DNA-SWCNT colloid system in probing inter-particle interactions in crowded and high salt environment (ACS Nano 5, 8258, 2011). In this talk, I will present some recent observations we made on DNA-SWCNT clustering that shed new light on a century-old puzzle in biophysical chemistry: the Hofmeister effect. Our results suggest that strongly correlated motion of ions in a high salt solution may play an important role in the Hofmeister effect.

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