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A new scalable method for purification of single-wall carbon nanotubes (SWNTs) by using microwave heating in air is developed. The microwaves couple to the residual metal catalyst, raising significantly the local temperature leading to both the oxidation and rupturing of the carbon passivation layer over the metal catalyst particles. With this protective carbon coating weakened or removed, a mild acid treatment is then sufficient to remove most of the metal in the sample, leaving the nanotubes in tact. Using microwave processing and 4 M HCl acid reflux for 6 h we were able to remove residual metal (Ni, Y) in arc-discharge SWNTs to a level lower than 0.2 wt % (∼0.04 at. %). Results from transmission and scanning electron microscopy, Raman spectroscopy, and thermogravimetric studies were discussed.

Retaining the inherent hydrophilic character of GO (graphite-oxide) nanosheets, sp(2) domains on GO are covalently modified with thiol groups by diazonium chemistry. The surface modified GO adsorbs 6-fold higher concentration of aqueous mercuric ions than the unmodified GO. "Core-shell" adsorbent granules, readily useable in filtration columns, are synthesized by assembling aqueous GO over sand granules. The nanostructured GO-coated sand retains at least 5-fold higher concentration of heavy metal and organic dye than pure sand. The research results could open avenues for developing low-cost water purification materials for the developing economies.

A series of Fe and Fe/Mo catalysts, supported on alumina, were examined for Single-Walled Nanotube (SWNT) growth by Chemical Vapor Deposition (CVD) in methane. Molybdenum (20 wt %) was found to provide a clear synergistic benefit, lowering the growth temperature and eliminating the need for catalyst activation in hydrogen. The dependence of the carbon mass yield and sample quality on the CVD growth conditions is discussed. Catalyst activity in both the oxide and reduced (metallic) form were investigated under low methane flow (40 cm 3 /min) and in the temperature range 600 < T < 900 °C. We found that the Fe/Mo oxide catalyst was active at temperatures as low as 680 °C. Under these "soft" conditions (680 °C, 40 cm 3 /min methane), the Fe-oxide catalyst (without Mo) was not active for tube growth, but it could be activated by an in situ reduction to metal in flowing He/(10% H 2 ). Tube diameters in the range 0.7 to 1.7 nm were produced under most of the growth conditions studied, as determined by Raman scattering. In most cases, the SWNTs were produced in bundles ∼10 nm in diameter, as observed by transmission electron microscopy. No evidence for coproduction of multiwalled tubes was found.