Upon contact with water, under a variety of conditions, C60 spontaneously forms a stable aggregate with nanoscale dimensions (d = 25−500 nm), termed here “nano-C60”. The color, hydrophobicity, and reactivity of individual C60 are substantially altered in this aggregate form. Herein, we provide conclusive lines of evidence demonstrating that in solution these aggregates are crystalline in order and remain as underivatized C60 throughout the formation/stabilization process that can later be chemically reversed. Particle size can be affected by formation parameters such as rates and the pH of the water addition. Once formed, nano-C60 remains stable in solution at or below ionic strengths of 0.05 I for months. In addition to demonstrating aggregate formation and stability over a wide range of conditions, results suggest that prokaryotic exposure to nano-C60 at relatively low concentrations is inhibitory, indicated by lack of growth (≥0.4 ppm) and decreased aerobic respiration rates (4 ppm). This work demonstrates the fact that the environmental fate, distribution, and biological risk associated with this important class of engineered nanomaterials will require a model that addresses not only the properties of bulk C60 but also that of the aggregate form generated in aqueous media.

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Existing toxicity data indicate that industrial-scale production of C60 fullerene poses a potential threat to the environment. Evaluating the environmental impact of C60 requires careful characterization of its physicochemical properties in the natural aqueous environment. Our study aims to determine the effects of aquatic natural organic matter (NOM) on the physicochemical properties of aqueous C60 nanoparticles, nC60. Stable nC60 suspensions were formed using three different solvent exchange protocols. They were thoroughly characterized for particle size, morphology, and electrophoretic mobility in the absence or presence of two model NOM components, Suwannee River humic acid and fulvic acid. NOM caused disaggregation of nC60 crystals and aggregates under typical solution conditions of natural water, leading to significant changes in particle size and morphology. Such effect increased with increasing NOM concentration. The changes in nC060 size and morphology strongly depended on the nC60 formation pathway. Results from this study indicate that NOM may play a critical role in the transport and toxicity of C60 in the natural aqueous environment.

Doping is a common and effective approach to tailor semiconductor properties. Here, we demonstrate the growth of large-area sulfur (S)-doped graphene sheets on copper substrate via the chemical vapor deposition technique by using liquid organics (hexane in the presence of S) as the precursor. We found that S could be doped into graphene's lattice and mainly formed linear nanodomains, which was proved by elemental analysis, high resolution transmission microscopy and Raman spectra. Measurements on S-doped graphene field-effect transistors (G-FETs) revealed that S-doped graphene exhibited lower conductivity and distinctive p-type semiconductor properties compared with those of pristine graphene. Our approach has produced a new member in the family of graphene based materials and is promising for producing graphene based devices for multiple applications.

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Single-walled carbon nanotubes functionalized by phenyl groups can be sulfonated in oleum (H 2 SO 4 , 20% free SO 3 ) to give materials that exhibit high solubility in water as determined by centrifugation in conjunction with UV-vis-near-infrared measurements. Cryo-transmission electron microscopy images show that extensive debundling occurs during the sulfonation step.

Oxidation of graphite may be carried out by reaction with meta-chloroperoxybenzoic acid to yield graphite epoxide. Scanning tunneling microscopy (STM) showed that the functionalization occurs at the edges rather than on the basal plane of the graphite. Quantification of the epoxide content is possible through the deepoxidation reaction using MeReO3/PPh3.