Thermal oxidation profiling of single-walled carbon nanotubes

The use of thermal oxidation profiling (TOP) to monitor the properties of single-walled carbon nanotube (SWNT)-containing samples at incremental temperature intervals has been developed. Specifically, the thermal decomposition of raw and acid-refluxed SWNT samples is evaluated by a systematic series of oxidative thermal treatments with concomitant purity assessment to ascertain the SWNT mass retention. The TOP results, supported by Raman spectroscopy, indicate that the SWNT decomposition coincides with the onset of raw soot combustion. The temperature for this SWNT combustion onset is equivalent to pure metal-catalyst oxidation, particularly for the highly exothermic Co metal. Thus, there are no discernible regions of a raw soot thermogravimetric analysis (TGA) curve that can be ascribed to SWNT combustion independent of metal impurity influence. In contrast, the acid-refluxed SWNT sample shows that chemical oxidation of the metal can enable optimization of SWNT retention during thermal purification. The established understanding between time and temperature on thermal oxidation allows for purification efficiencies (the highest purity at the maximum retention) of 75% w/w to be achieved in laser-produced SWNTs, without modification to the diameter distribution.