Covalent attachment of protein to the tip of a multiwalled carbon nanotube without sidewall decoration

We have demonstrated covalent bonding of protein molecules to an oxidized multiwall carbon nanotube (MWCNT) in an aqueous buffer solution. A chemical reaction using carbodi-imide forms chemical bonds between open-ended tips of MWCNTs and protein molecules. The statistical examination indicated that proteins were attached at the open-ended tip of MWCNT at a probability as high as 50% although proteins attached to the sidewall of the MWCNT were washed out after rinsing with running water.