A purification method has been developed that provides for the removal of metal catalysts and impurity carbon from laser-oven-grown single-wall carbon nanotube (SWNT) material. The oxidation rate of SWNTs in air at elevated temperatures is correlated to the metal content of the sample. Sample purity is documented with SEM, TEM, electron microprobe analysis, Raman, and UV-vis-near-IR. We also note that the relative intensity of the electronic transitions in the near-infrared to the continuum absorption at 400 nm in the UV serves as a useful monitor of the perturbation of the sidewall π-electron density of SWNTs due to sidewall substitution and/or oxidation.

Single-walled carbon nanotubes (SWNTs) with the N-alkylidene amino groups covalently attached to their side walls have been prepared starting from colloidal solutions of fluorinated SWNTs (fluoronanotubes) in terminal alkylidene diamines followed by heating at 70−170 °C. On the basis of data from thermal gravimetric and energy-dispersive X-ray analyses, the degree of SWNT functionalization achieved was estimated to be as high as 1 in 8 to 12 sidewall carbons. The demonstrated new C−N functionalization method provides a synthetic tool for binding amino acids, DNA, and polymer matrices to the side walls of the SWNTs as well as yields sidewall amino-functionalized nanotube precursors for the preparation of nylon−SWNT polymer materials.

The role of surface chemistry on the toxicity of Ag nanoparticles is investigated using Saccharomyces cerevisiae yeast as a platform for evaluation. Combining the shape-controlled synthesis of Ag nanoparticles with a comprehensive characterization of their physicochemical properties, an understanding is formed of the correlation between the physicochemical parameters of nanoparticles and the inhibition growth of yeast cells upon the introduction of nanoparticles into the cell culture system. Capping agents, surface facets, and sample stability--the three experimental parameters that are inherent from the wet--chemical synthesis of Ag nanoparticles-have a strong impact on toxicity evaluation. Hence, it is important to characterize surface properties of Ag nanoparticles in the nature of biological media and to understand the role that surface chemistry may interplay to correlate the physicochemical properties of nanoparticles with their biological response upon exposure. This work demonstrates the great importance of surface chemistry in designing experiments for reliable toxicity evaluation and in mitigating the toxicity of Ag nanoparticles for their safe use in future commercialization.