Inhibiting soot formation requires a fundamental understanding of the physicochemical processes from fuel to soot. At present, the polycyclic aromatic hydrocarbons (PAHs) are widely recognized to be the important precursors of soot formation . The generation of soot particles is believed to undergo four steps, including the pyrolysis of carbon fuel, PAH growth, soot nucleation, soot growth and oxidation . However, detailed chemical mechanism of PAH growth has not yet been well established and specific reaction paths leading to the PAH growth remain elusive. Furthermore, definite chemical mechanisms leading to the inception of soot from the growth of PAH is probably the least known part of soot formation process, and is highly debated .