Make it different: The plasma treated multi-walled carbon nanotubes improve electrochemical performances toward nitroaromatic compounds

Abstract

On the basis of plasma treatment method, O2-plasma-treated multi-walled carbon nanotubes (po-MWCNTs) and NH3-plasma-treated multi-walled carbon nanotubes (pn-MWCNTs) were used for electrochemical detection of nitroaromatic compounds (NACs) and showed enhanced sensitivity compared with raw MWCNTs. The difference of electrochemical response toward NACs between po-MWCNTs and pn-MWCNTs was observed and systematically compared in this work for the first time. Square wave adsorptive stripping voltammetry has been used for the detection of 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT) and 4-nitrotoluene (4-NT). By comparing the electrochemical performance toward the three different NACs, it was found that the different number of nitro groups on aromatic ring can cause different sensitivity at the po-MWCNTs and pn-MWCNTs electrodes. The detection limit (3σ method) of both the po-MWCNTs and the pn-MWCNTs electrodes was below nM level. The chemical and electrochemical parameters that exert influence on oxidation–reduction reaction of NACs, such as supporting electrolytes, pH value, and deposition time, were carefully studied. The difference between po-MWCNTs and pn-MWCNTs electrodes indicated that different functional groups on MWCNTs surface may result in the different electrochemical responses toward NACs, which enlighten the area of functionalizing the MWCNTs for detecting NACs. In addition, the possible mechanisms based on adsorption have been proposed. The electrochemical behavior and adsorption ability are closely bound up.