Abstract Submitted to the ; NANOTUBE'05 Conference:

X-ray scattering from aligned SWNT fibers swollen in anhydrous sulfuric acid provides unambiguous structural evidence for the long-conjectured partly-ordered solvent shells surrounding an ionic solute [1]. Preferred orientation of SWNT in the fibers is replicated by the diffuse scattering from partly ordered cylindrical “shells” a few molecules thick, wrapped around the SWNT. Acid supercooling and melting of random SWNT-acid suspensions (DSC) vary in temperature and enthalpy with SWNT concentration, confirming that the partly ordered molecules are a new phase. Furthermore, X-ray scattering vs. temperature shows that crystallization of bulklike acid surrounding the structured shells is templated by the aligned SWNTs, while the structured shells remain partly ordered [2]. The (2 0 0) or (2h 0 2) planes of the templated H2SO4 crystallites are parallel to the nanotube axes, from which it can be deduced that the acid molecules are preferentially oriented with a proton in contact with the SWNT surface. This provides solid evidence for the direct protonation of SWNT .
The first-ever well-aligned continuous macroscopic neat single-walled carbon nanotube (SWNT) fibers were produced using conventional spinning techniques. Neat SWNT fibers, containing no surfactant or polymer, were made by spinning dispersions of SWNTs in 102% sulfuric acid into different coagulants. The critical role of sulfuric acid in dispersing and aligning SWNTs during fiber formation has been explored. Characterization shows alignment greater than any other macroscopic neat SWNT material reported to-date while providing insight into the fundamental hierarchy and nature of SWNT fiber formation [3]. Electrical, thermal, and mechanical measurements indicate that neat SWNT fibers hold tremendous potential for future applications.
We propose that charge transfer between nanotube  electrons and highly oxidizing superacid is responsible for the unique partly ordered structure.

1. W. Zhou, P. A. Heiney and Fischer, PRB (submitted).

2. W. Zhou, P. A. Heiney, H. Fan, R. E. Smalley and J. E. Fischer, J. Am. Chem. Soc. v.127, p.1640 (2005).

3. L. M. Ericson, H. Fan, H. Peng, V. A. Davis, J. Sulpizio, Y. Wang, R. Booker, W. Zhou, J. Vavro, C. Guthy, S. Ramesh, C. Kittrell, G. Lavin, H. Schmidt, W. W. Adams, M. Pasquali, W.-F. Hwang, R. H. Hauge, J. E. Fischer and R. E. Smalley, Science 305, 1447 (2004).

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