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Alteration of nC60 in the Presence of Environmentally Relevant Carboxylates

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journal contribution
posted on 20.02.2016, 21:14 by Xiaojun Chang, Laura K. Duncan, Joerg Jinschek, Peter J. Vikesland
C60 forms colloidally stable nanoscale particles (nC60) when mixed with water for extended periods. Past studies have shown that macromolecules such as natural organic matter (NOM) and proteins accelerate nC60 formation and stabilize the resulting nanoparticles. To better elucidate the mechanisms underlying this behavior, nC60 was produced via extended mixing in the presence of sodium citrate and other carboxylates. Carboxyl groups are a predominant functional group in many environmentally relevant macromolecules, thus studies examining carboxyl–C60 interactions are merited. nC60 produced in the presence of citrate (cit/nC60) and other carboxylates differs from nC60 produced in water alone (aq/nC60), exhibiting enhanced negative surface charge, smaller particle size, and different spectroscopic characteristics. Importantly, the simultaneous detection of irregular nC60 nanoparticles and small, regularly shaped nC60 suggests that mixing-mediated “top-down” and carboxyl group-mediated “bottom-up” processes occur concurrently when nC60 is produced in the presence of carboxylates and, by extension, in the presence of carboxylate-containing macromolecules. The “bottom-up” process is expected to involve molecular C60 or small clusters of C60 molecules as an important intermediate.