Thermophoretic sensors for combustion formed nanoparticles

It is well established that ultrafine carbonaceous particles represent the major source of carbon aerosols in the atmosphere, and their formation has been intensively investigated over the last decades due to their negative effects on human health and environment. Moreover, combustion-formed nanoparticles represent a broad class of compounds since they can be highly variable in terms of size, chemical composition, morphology and optical properties. In the light of the above, the development of highly sensitive, costly effective combustion aerosols sensors, capable to give both qualitative and quantitative information is needed. In this work, thermocouple particle densitometry (TPD) technique, which is based on the thermophoretic sampling principle, has been carried out to detect nanoparticles produce in a slightly sooting laminar premixed flame at different height above the burner (HAB). With this technique, the particle emissivity and the total particulate volume fraction have been obtained and results are compared with the ones determined by on-line measurements using a Scanning Mobility Particle Sizer system (SMPS). The good agreement between results obtained with the two independent measurements demonstrates that transient-thermocouple measurement is a powerful technique to detect the total particulate volume fraction, together with particle emissivity. In addition, thermophoretic sampling has been adopted for the collection and electrical characterization of combustion nanoparticles with different graphitization degree. This work demonstrates that the feasibility of such an approach can be useful for the development of conductometric combustion aerosol sensors.