Thermally induced variation in redox chemical bonding structures of single-walled carbon nanotubes exposed to hydrazine vapor

The effect of hydrazine (N2H4) vapor on the properties of single-walled carbon nanotube (SWCNT) networks was investigated by sheet resistance measurement, scanning electron microscopy, Raman spectroscopy, ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy (XPS). Our results show that, even after an auxiliary thermal desorption treatment at 80 °C, the n-doping effect on our SWCNTs caused by N2H4 vapor still persistently remained. Further analysis on the XPS data suggests that a reactive chemical species, nitrene (NH), generated during thermal decomposition of N2H4, could react with SWCNTs by cycloaddition to form cyclic nitrogen-containing aziridine structures on SWCNTs. Our results also show that the formed nitrogen-containing bonding structures were thermally metastable and could be significantly eliminated upon further annealing at 350 °C. Moreover, it was found that the N2H4 vapor treatment could introduce nitroso groups and carbonyl groups, but not carboxyl groups, to our pristine SWCNTs. The mild oxidation could be attributed to the HNO2 and H2O2 produced from the reactions of NH and N2H4 with oxygen, respectively, when a N2H4 treatment was performed in air.