Full-length single-walled carbon nanotubes (SWNTs) were rendered soluble in common organic solvents by noncovalent (ionic) functionalization of the carboxylic acid groups present in the purified SWNTs. Atomic force microscopy (AFM) showed that the majority of the SWNTs ropes were exfoliated into small ropes (2-5 nm in diameter) and individual nanotubes with lengths of several micrometers during the dissolution process. The combination of multiwavelength laser excitation Raman scattering spectroscopy and solutionphase visible and near-infrared spectroscopies was used to characterize the library of SWNTs that is produced in current preparations. The average diameter of metallic nanotubes was found by Raman spectroscopy to be smaller than that of semiconducting nanotubes in the various types of full-length SWNT preparations. This observation sheds new light on the mechanism of SWNT formation.

The past decade has witnessed an explosion of techniques used to pattern polymers on the nano (1-100 nm) and submicrometre (100-1,000 nm) scale, driven by the extensive versatility of polymers for diverse applications, such as molecular electronics, data storage, optoelectronics, displays, sacrificial templates and all forms of sensors. Conceptually, most of the patterning techniques, including microcontact printing (soft lithography), photolithography, electron-beam lithography, block-copolymer templating and dip-pen lithography, are based on the spatially selective removal or formation/deposition of polymer. Here, we demonstrate an alternative and novel lithography technique--electrostatic nanolithography using atomic force microscopy--that generates features by mass transport of polymer within an initially uniform, planar film without chemical crosslinking, substantial polymer degradation or ablation. The combination of localized softening of attolitres (10(2)-10(5) nm3) of polymer by Joule heating, extremely non-uniform electric field gradients to polarize and manipulate the soften polymer, and single-step process methodology using conventional atomic force microscopy (AFM) equipment, establishes a new paradigm for polymer nanolithography, allowing rapid (of the order of milliseconds) creation of raised (or depressed) features without external heating of a polymer film or AFM tip-film contact.

Mechanistic aspects of the reductive dehalogenation of trichloroethylene using zerovalent iron are studied with three different surface characterization techniques. These include scanning electron microscopy, surface profilometry, and atomic force microscopy. It was found that the pretreatment of an iron surface by chloride ions causes enhancement in the initial degradation rates. This enhancement was attributed to the increased roughness of the iron surface due to crevice corrosion obtained by pretreatment. The results indicate that the “fractional active site concentration” for the reactive sorption of trichloroethylene is related to the number of defects/abnormalities present on the surface of the iron. This was elucidated with the help of atomic force microscopy. Two possible mechanisms include (1) a direct hydrogenation in the presence of defects acting as catalyst and (2) an enhancement due to the two electrochemical cells operating in proximity to each other. The result of this study has potential for further research to achieve an increase in the reaction rates by surface modifications in a practical scenario.