Air oxidation of carbon soot generated by laser ablation

Abstract Carbon soot was generated by laser ablation under oxygen-free and regulated-temperature conditions at 300 K and 1500 K. The soot was significantly oxidised by being exposed to air in darkness. The degree of oxidation was determined to be 0.038±0.012 and 0.093±0.009 for the high temperature (HT) soot and the low temperature (LT) soot, respectively, on the basis of elemental analysis, XPS and Karl-Fischer titration. Water physically absorbs on the soot in proportion to the degree of oxidation. TG, TPD and 13 C-NMR revealed that there were at least 2 kinds of oxidised states. One of them mainly contributes to CO and CO 2 emissions at 420–970 K, while another contributes to CO emission above 770 K. The former is a dominant oxide in the LT soot. On the basis of FT-IR and 13 C-NMR spectra, carbonyl groups were confirmed to be one of the major oxidised species in the soot. FT-IR and acid-base titration revealed that the LT soot adsorbed more CO 2 than the HT soot did. The adsorbed CO 2 contributes to the acidic property of the soot. The soot is paramagnetic as well as conductive. C 1s and Auger photoelectron spectra of the soot were neither graphite-like nor diamond-like. The air oxidation is discussed in relation to unique structures and formation mechanisms of the soot.