Application of chemical graph theory to PAH isomer enumeration and structure in laser desorption/ionization mass spectrometry studies of particulate from an ethylene diffusion flame

On the Mechanism of Soot Nucleation. III. The Fate and Facility of the E-Bridge

“…One of the remaining unknowns of the process is particle inception or nucleation, namely, the elementary mechanism of transition from gaseous PAH precursors to solid carbonaceous particles. , A purely chemical growth of aromatics, i.e., the extension of PAH size by addition of gaseous species, such as acetylene, is insufficient to explain the size of emerging soot particles; the particle size is determined by particle coagulation . The latter assertion was suggested by early transmission electron microscopy of soot particles and phenomenological analysis of their time evolution, which was later corroborated by detailed modeling. − A more recent affirmation comes from high-quality experimental observations of particle nanostructure, showing that particle constituents are largely middle-range (four-to-six-ring) − or larger (seven-to-24-ring) PAH. , …”

“…8−11 A more recent affirmation comes from high-quality experimental observations of particle nanostructure, showing that particle constituents are largely middle-range (four-to-six-ring) 12−18 or larger (seven-to-24-ring) PAH. 3,19 Assuming that the gas-to-solid transition begins with irreversible dimerization of middle-range PAH (like pyrene or coronene) allows one to numerically reproduce the evolution of soot particles in flames. 10,20,21 However, this assumption appears to be in conflict with the thermodynamic stability of such midrange PAH dimers.…”