DownToTen seeks to develop a reliable and robust methodology to enhance the regulatory approach in the assessment of particle number emissions in the sub 23 nm region (down to at least 10 nm), focusing on state-of-the-art automotive powertrains with direct injection gasoline engines, but also diesel engines, under real-world operation conditions. To this end, DownToTen will first investigate and quantitatively describe the nature and the characteristics of nanoparticles <23 nm (formation, origin, physical and chemical characteristics), and will set up a synthetic aerosol bench for fundamental studies at instrument level for the facilitation of metrology and evaluation purposes. Existing, proposed and under development instruments will be evaluated against rigorous criteria for the measurement of sub-23 nm particles, with emphasis on their applicability as portable emissions systems (PEMS). Beside organic aerosol, the target is to analyse solid or non-volatile particles. Inorganic particles <23 nm that are of particular environmental and toxicological interest have not been characterized so far. This deficiency results from a number of factors such as the limited availability of routine analytical techniques that allow to determine elements at ultratrace levels and the lack of sampling strategies for <23 nm particles.
For off-line chemical characterization of sub-23 nm particles several methods have been tested: Inductively coupled plasma mass spectrometry (ICP-MS), total reflection x-ray fluorescence (TXRF) or neutron activation analysis (NAA). Very little sample amount is challenging for all used methods and the appropriate filter material is of crucial importance. However, artefact-free sampling of nanoparticles is a challenge, hence we also employ online analytical techniques, which are developed within the framework of the project.
Mass spectrometry with a new ionization source from Plasmion, a high-tech start-up company founded by alumni J.-C. Wolf, allows for direct online analysis of exhaust gas. It is combined with particle size fractionation and a newly developed optical evaporation system (HELIOS, High Efficient LIght source for Optical Surface Desorption), thus allowing for the characterization of volatile and semi-volatile particles.