Destabilization of Aqueous Colloidal C60 Nanoparticles in the Presence of Various Organic Matter

Abstract

AbstractThe extractable fraction of aqueous colloidal C60 nanoparticles (nC60) was quantified using a liquid–liquid extraction method in the presence of five types of dissolved organic matter (DOM): Aldrich humic acid (AHA), Suwannee River fulvic acid (SFA), sodium dodecyl sulfate (SDS) micelle, liposomes composed of 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine (POPC), and bovine serum albumin (BSA). The changes in toluene extractable fraction highly depended on the type and dose of DOM. Whereas an environmentally relevant concentration of AHA, 2–20 mg L−1, was sufficient to reduce the nC60 fraction easily destabilized, much higher dose of fulvic acid was needed to result in the similar degree of stabilization. A big contrast between two types of self‐organized DOM, SDS micelle and POPC liposomes, was observed. Although SDS micelle significantly decreased the toluene extractable fraction of nC60 at the dose greater than its critical micelle concentration, no apparent decrease in toluene extractable fraction was found in the presence of POPC liposomes up to 3000 mg L−1. The toluene extractable fraction of nC60 in the presence of BSA rapidly decreases at lower doses then gradually decreased at higher doses. An equilibrium complexation model was proposed to quantitatively describe the decrease in the extractability of nC60 in the presence of DOM. The observed decrease in the extractability of nC60 was well explained by the model and the complexation of nC60 with DOM was thought to occur close to 1:1 molar ratio except for BSA. The association constants of nC60 with DOM were in the order of BSA, AHA, SFA, and SDS micelle, showing the differences in the affinity to nC60.