275823 “Zero Dimensional” Single Walled Carbon Nanotubes

Tuesday, October 30, 2012: 10:30 AM
311 (Convention Center )
Kaladhar Kamalasan1,2,3,4, Riccardo Gottardi1,4,5,6, Susheng Tan7, Yanan Chen8, Bhaskar Godugu8, Sam N. Rothstein1, Anna C. Balazs1, Alexander Star8 and Steven R. Little1,2,3,4, (1)Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA, (2)Department of Immunology, University of Pittsburgh, Pittsburgh, PA, (3)Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, (4)McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, (5)Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, (6)Fondazione RiMED, Palermo, Italy, (7)Department of Electrical and Computer Engineering, University of Pittsburgh, Pittsburgh, PA, (8)Department of Chemistry, University of Pittsburgh, Pittsburgh, PA

Single-walled carbon nanotubes (SWNTs) are unique, one dimensional, tubular carbon allotropes with exceptional properties. Individual and dispersible SWNTs are, however, rarely available, since their side wall hydrophobicity and disproportionate length drive them to form long bundles. These factors represent an obstacle for wet nanoscale applications of SWNTs. One approach to overcome these issues is to dramatically reduce the tube length so as to make the tube side-wall hydrophobicity and dispersibility more manageable. Herein, we report the first synthesis and characterization of SWNTs in the 2nm-5nm length range, the shortest so far achieved to our knowledge. In effect, we have reduced a long (and essentially) one dimensional material to tubes whose lengths are on the same order of their diameter, thus effectively rendering them “zero dimensional” (or “0dSWNTs”). We observe that 0dSWNT maintain the structural properties of nanotubes but possess increased dispersibility and complete water-solubilization (>3 months) following appropriate chemical (hydroxylation) functionalization. Finally, we examined 0dSWNTs by mass spectrometry, which is the first instance, to our knowledge, of positive identification of the appropriate signature of a carbon nanotube using MALDI-TOF-MS.

The 0dSWNTs may represent unique building blocks for a bottom-up approach to the exploitations of nanotubes as their production process from SWNTs can be scaled up and automatized. Furthermore, their low dimensional anisotropy renders them well dispersible in water. Furthermore, additional functionalization is also possible, such as hydroxylation (OH-0dSWNTs) rendering these tubes water soluble for long periods of time and allowing them to fly in a MALDI-TOF mass spectrometer. Alternate functionalization could also be used to direct, their self assembly, depending on the final structure required for electronics, nanofiltration, energy, materials science, or biomedical applications. In addition, as 0dSWNTs have the dimensions typical of transmembrane proteins and the alternate hydrophilic-hydrophobic pattern of a lipid layer, they could potentially insert themselves in a lipid membrane acting as an artificial channel to shuttle ions, nutrients, peptides. Such structure would be capable of performing some of the complex behaviors typical of biological cells, opening the way to new “synthetic cellular therapies”.  Proof-of-principle preliminary data will be presented that suggest that this is now a possibility.

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