Effect of Acid Treatment on the Structure and Electrical Properties of Nitrogen-Doped Multiwalled Carbon Nanotubes

Nitrogen-doped multiwalled carbon nanotubes (CNx MWNTs) have been cut to an average length of ∼1 μm by room-temperature acid treatment. Imaging of the surface morphology of the CNx MWNTs (x = 2−5%) after sonication in acid or in ethanol (as a control) allowed the relationship between surface structure and acid cutting to be characterized. The effect of the acid treatment on the electrical conductance of the CNx MWNTs was also determined. The conductance of acid-treated CNx MWNTs was found to vary significantly within the sample and to be lower than the value of 1.0 G0 observed for as-produced CNx MWNTs. The G−V curves reported for acid-treated CNx MWNTs had an average slope of 0.19 G0/V, which is significantly smaller than the average of 0.70 G0/V measured for as-produced CNx MWNTs. Acid-treated CNx MWNTs exhibited a more rapid electrical breakdown with larger current steps, indicating the breakdown of several MWNT layers simultaneously.