Spectroscopic characterisation of carbonaceous nanoparticles in premixed flames

This work deals with the characterisation of the carbonaceous aerosols produced in a combustion source. These particles can be connected to the black and primary organic carbon aerosols found in the atmosphere. Premixed fuel rich laminar flames in sooting and non-sooting regimes of combustion are examined UV-visible light absorption laser-excited fluorescence, laser-induced incandescence and light scattering. The analysis of the spectroscopic measurements leads to the formulation of a model for the aerosol formed in flame consisting of a background matrix, with mono-ring sub-units connected by aliphalic bonds, that contains inclusions made of two aromatic rings and, in some cases, soot-like black carbon. With this model, the use of the scattering/absorption technique allows us to estimate the mean dimension and concentration of such particles. The most important finding of this paper is that carbon containing aerosol with typical size around 2 nm are formed also in non-luminous flames where elemental black carbon is absent and that similar particles are precursors for soot particles which are produced by their coagulation.