The physisorption of radiolabeled I-125(-) ions from aqueous solution and the Brunauer-Emmett-Teller (BET) surface areas of various carbonaceous materials [HiPco single-wall carbon nanotubes (SWNTs), F-SWNTs, cut SWNTs, charcoal, graphite, F-graphite and C-60] have been measured and compared. By far, cut SWNTs (mainly 20-50 nm lengths) displayed the largest surface area of the materials (1180 m(2)-g(-1)), being approximately double that of uncut SWNT and charcoal. At low concentrations of I-125(-), nearly all of the I-125(-) was adsorbed from aqueous solution within 1 min at room temperature by the cut SWNTs, uncut SWNTs, and charcoal; the other materials showed much less adsorption under the same conditions. Once adsorbed, the I-125(-) wash-off rate by pure water was highly variable but was especially slow for cut SWNTs (t(1/2) approximate to 2720 h) compared to the other materials; wash-off of I-125(-) by an aqueous H2O2 solution (I-125(-) -> H2O2 I-125(2)) was even slower (t(1/2) approximate to 14 300 h). Taken together, these data demonstrate the greatly increased surface area and dramatically enhanced retention properties of cut SWNTs over uncut SWNTs.