Investigation of modified basal plane pyrolytic graphite electrodes: definitive evidence for the electrocatalytic properties of the ends of carbon nanotubesElectronic supplementary information (ESI) available: the use of CNT-modified electrodes in electrochemistry, and SEM images of MWNTs before immobilisation and after modification of a basal plane pyrolytic graphite electrode. See http://www.rsc.org/suppdata/cc/b4/b406174h/