In this work, we report that the surface hydroxylation of C 60 molecules is the most likely mechanism for pristine C 60 fullerenes/C 60 fullerene aggregate stabilization in water, being independent of the method of C 60 fullerene aqueous solution preparation. ■ INTRODUCTIONNanocarbon materials are used in a wide variety of biomedical applications, including biosensorics, targeted drug delivery, chemotherapy, cellular imaging, and diagnostics. 1 For example, the pristine C 60 fullerenes as a unique class of carbon allotropes are able to penetrate the cell membrane, 2,3 to exhibit antioxidant properties, 4,5 and, being nontoxic (at least at low concentration), 6 to exert specific health effects (e.g., antibacterial, 7 antitumor, 8 and drug carrier 9 ).Biomedical applications require a dispersal of C 60 fullerene in a solvent, with aqueous dispersions being preferred because of biocompatibility, safety, or environmental concerns. Although pristine C 60 fullerenes have extremely low water solubility, they can form stable colloid solutions containing individual C 60 fullerenes as well as C 60 fullerene aggregates (clusters) in water when subjected to extended mixing, sonication, or solvent exchange 10−16 (to be further referred to as a C 60 fullerene aqueous colloid solution (C 60 FAS)). However, the origin of stabilization of such particles in water still remains poorly investigated.At least two approaches have been suggested in order to explain the stability of fullerene particles in water solutions. One of them 17 postulates the formation of a water shell around C 60 molecules stabilized simultaneously by the H-bonding network between the water molecules and charge transfer from water to the C 60 fullerene. Another one 18 suggests that the sonication process induces the covalent attachment of water hydroxyls to C 60 fullerene carbons, resulting in the formation of alcohol moieties that enable C 60 fullerene dissolution. The problem here is that the properties of C 60 FAS (including biological properties) as well as the mechanism of water solubility may depend on the method of preparation of C 60 fullerene aqueous solution. 13,16,17 Indeed, these two approaches differ by the underlying method of C 60 FAS preparation although the sonication step is presented in both methods. The question therefore arises as to whether the mechanism of solubility of C 60 fullerene in water depends on the method of C 60 FAS preparation. This question has been investigated in this article. ■ EXPERIMENTAL SECTIONSample Preparation. For the preparation of C 60 FAS, we used a saturated solution of pure C 60 fullerene (purity >99.99%) in toluene with a C 60 molecule concentration corresponding to maximum solubility near 2.9 mg/mL and the same amount of distilled water in an open beaker. The two phases that formed were treated in an ultrasonic bath. The procedure was continued until the toluene had completely evaporated and the water phase became yellow. Filtration of the aqueous solution allowed us to separate the product from un...

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The lithium conductivity of NASICON glass-ceramic electrolytes can be increased 5 times just by using additives, which change the glass crystallization patterns.