Oxidized carbon nanotubes were covered with layers of bovine serum albumin to result in so-called restricted-access carbon nanotubes(RACNTs).This material can extract Pb2þ ions directly from untreated human blood serum while excluding all the serum proteins.Th eRACNTs havea protein exclusion ca-pacity of almost 100% and amaximum Pb2þ adsorption capacity of 34.5mgg1.