Fourier transform infrared spectroscopy has been used to reveal the nature of functional groups on the surface of soot. Bands which showed isotopic shifts upon regenerating soot functionalities with <sup>18</sup>O<sub>2</sub> in the 1700 cm<sup>−1</sup> and 1200 cm<sup>−1</sup> regions were assigned to ketone-like carbonyl and ether-like groups on the surface, while the 1590 cm<sup>−1</sup> band, which fails to show any isotopic shift upon the reoxidation of soot with <sup>18</sup>O<sub>2</sub> at high temperature, has been assigned to a carbonyl group conjugated with aromatic ring segments. Bands in the 800 cm<sup>−1</sup> were given no definite assignments (Fig. 1). Logical origins of these bands could be the C-H out-of-plane bending of highly substituted aromatic compounds or stretching modes of peroxides or hydroperoxides. An attempt is made in this work to substantiate the origin of these bands.
J. A. Jassim, H. P. Lu, A. R. Chughtai, and D. M. Smith, "The Origin of Infrared Absorption Bands of Soot in the Region 750 to 900 cm-1," Appl. Spectrosc. 40, 113-116 (1986)