Effect of Different CNT’s Oxidation Methods on Thiocoline Detection by Surfactant Modified Graphite Electrodes

Carbon nanotubes are regarded as promising building blocks for the construction of novel biosensors due to their unique properties like fast electron transfer, high electrocatalytic effect and good biocompatibility. In the present study, the effect of different chemical oxidation’s methods of multi-walled carbon nanotubes (MWCNTs) on the electrochemical behavior of modified graphite electrodes has been investigated. The MWCNTs were oxidized by using three kinds of oxidants: a) concentrated nitric acid (65 wt %), b) mixture of concentrated sulfuric acid (98 wt %) and nitric acid (65 wt %) (3:1), and c) hydrochloric acid (2M) followed by acid mixture of (b). The results of oxidation procedures were characterized by infrared spectroscopy. Graphite electrode surface was modified with cationic, anionic, and non-ionic surfactants. The obtained results showed that amperometric responses of functionalized CNTs were enhanced with cationic surfactant-modified electrodes. The sensitivity of nitric acid treated CNT/DTAB/graphite electrode has been enhanced by 47% and its detection limit has reduced to 0.01 mM for amperometric thiocholine detection.