Functionalization of single-walled carbon nanotubes (SWCNT) plays a tremendous role in the reactivity of these materials in natural systems. In this study, two contrasting cases of reactivity have been examined. In the first case, unfunctionalized SWCNT show very low reactivity by direct reactions under solar light. However, indirect reactions may occur. In our case, we generated hydroxyl radicals from photolysis of hydrogen peroxide under solar spectrum light. Unfunctionalized SWCNT from Southwest Nanotechnologies (SG65 tubes) were used in experiments, which contain a high fraction of semiconducting tubes. Reactions in aqueous suspensions containing sodium dodecylsulfate (added to disperse the SWCTs) were following by UV/Vis and Raman spectrometry. Within several days, UV/Vis absorbance bands decreased and the Raman ID band increased relative to the IG band, indicating loss in characteristic properties of the unfunctionalized nanotubes. In the second case, the ability of carboxylated single-walled nanotubes (SWCNT-COOH) to participate in dark redox reactions was examined. Using NADH as an electron donor, the formation of superoxide anion (O2.-) in aqueous suspensions of SWCNT-COOH was observed in the absence of light within several hours at pH 7. Because hydroxyl radicals (.OH) are sometimes produced through further reactions involving electron donors, this ROS was also assayed, but not found. However, hydrogen peroxide (H2O2), an intermediate along this same pathway, was found to accumulate in the aqueous phase, suggesting it is a final product of superoxide anion decay in this simple aqueous system.

Abiotic reactions involving single-walled carbon nanotubes in the aquatic environment

246th National Meeting (2013)

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