Study of single-walled carbon nanotube reactivity and applications of the functionalized species
Doyle, Condell Dewayne
Tour, James M.
Doctor of Philosophy
Significant advancements have been made recently in the area of single-walled carbon nanotube (SWCNT) functionalization using diazonium salts. Specifically research using oleum and molten urea as the solvent has opened the door to potentially high volume methods that yield predominately functionalized individuals. Once functionalized, these materials can be used for a variety of applications including super capacitors, fuel cell membranes and hydrogen storage media. Aside from advancement in materials chemistry, recent insights into the mechanism of diazonium salt functionalization have yielded results that could lead to viable separation techniques. Spectrally resolved fluorescence spectroscopy of mixed SWCNT samples has been used to measure structure-dependent relative reactivities in the initial stages of these reactions. For several 4-substituted benzenediazonium salts, Ar-R (Ar = N 2 + -C 6 H 4 and R = Cl, NO 2 , OMe), reactivities at pH 10 were found to be greatest for SWCNTs having the largest band gaps. The magnitude of this band gap dependence varies according to the R-group of the sait, with R = OMe showing the strongest variation. For R = OH, acidification of the sample to pH 5.5 results in reversal of the structural trend, as smaller band gap SWCNTs show slightly greater reactivities. The derivatization reactions observed here proceed concurrently, although at different rates, for semiconducting and metallic SWCNT species.