DLS measurements on nanoparticles produced in laminar premixed flames.

In this work dynamic light scattering (DLS) is used to measure the diameter distribution function of nanoparticles produced in non-sooting zone of ethylene/air premixed flames with various combustible/oxidant ratio and collected in water. In all the exhaust flames the particles size ranges from 2 to 4 nm. We report also preliminary results of nanoparticles size distributions obtained by DLS measurement in flames for higher heights above the burner where the particles size ranges from 8 to 30 nm. These results are in agreement with the predictions of the model of fast formation of nanoparticles in flames by means of two- and three-ring polycyclic aromatic hydrocarbon functionalities. Combining the ex situ results and the in situ scattering and extinction measurements in UV, the complex refractive index of nanoparticles has been determined. 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.