Inevitably, the growth in production of carbon nanotubes will translate into their release into our environment, yet existing information about their fate and persistence is limited. We hypothesize that indirect photochemical transformation of unfunctionalized carbon nanotubes is likely to be one of the few pathways by which these materials are altered in the environment. To this end, we examined whether indirect photo-reaction of single-walled carbon nanotubes (SWNT) occurs in aqueous media by generating hydroxyl radical through hydrogen peroxide photolysis under lamplight at wavelengths of 300-410 nm. Unfunctionalized SWNT from Southwest Nanotechnologies, containing a high fraction of semiconducting nanotubes (SG65), were used. In most of the experiments, aqueous suspensions containing sodium dodecylsulfate (used as a dispersant) were irradiated, following the reactions by UV/Vis, Raman, and near infrared fluorescence (NIRF) spectrometry, and TEM imaging. Within several days, UV/Vis absorbance bands decreased, the Raman ID band increased relative to the IG band, and fluorescence signals for (6,5) and (8,4) chiralities (dominate chiralities contained in the SG65 mixture) faded. This indicated loss in characteristic properties of the unfunctionalized nanotubes, due to reaction with hydroxyl radicals. To extrapolate overall reactivity found in our system to that expected for natural aqueous systems, the hydroxyl radial steady-state concentration, detected using p-chlorobenzoic acid (pCBA) as a molecular probe, was compared to values in typical natural systems.

Hydroxyl radical induced photo-transformation of single-walled carbon nanotubes in the aquatic environment

246th National Meeting (2013)

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