Evidence and characterization of nanoparticles produced in nonsooting premixed flames

The size distribution of nanoparticles generated in nonsooting ethylene/air premixed flames and collected in water samples has been evaluated using two particle-sizing techniques that show high sensitivity to particles in the nanometer size range: dynamic light scattering and electrospray-differential mobilty analysis. A d(63) of 2.85 nm has been estimated. By combining the results of ex situ size determination and in situ scattering and extinction measurements in UV, the complex refractive index of nanoparticles has been determined. The result is in good agreement with the value we previously used for the elaboration of in situ measurements and is also consistent with the conceptual model that nanoparticles formed in flames contain 2-, 3-ring polycyclic aromatic hydrocarbon functionalities as their building blocks. This work shows that nanoparticles produced in combustion systems are partially soluble in water, which is particularly relevant for determining their possible effects on human health and climate.