Nanoparticles of organic carbon (NOC) formed in flames and their effect in urban atmospheres

The process by which carbonaceous nanoparticles are produced in premixed flames is reviewed. The focus of the paper is on the formation and properties of nanoparticles in laboratory laminar, premixed and diffusion flames and on the methods of sampling and detection of these particles. Particle chemical nature is analyzed from data obtained by several measurement techniques. Measurements characterizing nanoparticles in the exhausts of practical combustion systems such as engines and commercial burners are also reported. Two classes of carbonaceous material are mainly formed in combustion: nanoparticles with sizes in the range 1-5nm, and soot particles, with sizes from 10nm to 100nm. Nanoparticles show unique chemical composition and morphology; they maintain molecular characteristics in terms of chemical reactivity, but at the same time exhibit transport and surface related properties typical of particles. The emission of these particles contributes to atmospheric pollution and constitutes a serious health concern.