Hydrogen, sp2 Carbon Hybridization, and sp2 Clustering as Pieces of the Puzzling Nanostructure of Soot: A Closer Look

This paper reviews recent results concerning specific structure-sensitive parameters of soot such as the content of hydrogen and the size and shape of sp2-hybridized carbon featuring the structure of amorphous carbons as soot. UV–visible, Fourier-transformed infrared (FTIR), and Raman spectra are described along with the methods used for obtaining the hydrogen content, the sp2 aromatic carbon content, and the size of sp2 clusters featuring soot structure. The outputs coming from spectroscopic analysis are discussed in connection to transmission electron microscopy (TEM) and high resolution TEM (HRTEM) and mass spectrometric analysis. Soot spectroscopic data were compared to those obtained from organic carbon (OC) constituting as-sampled carbon particulate matter in order to get evidence for the peculiar spectroscopic and compositional signatures, which bring together and differentiate OC and soot.