(302b) Soot Source Identification By Laser Derivitization

Combustion produced soot is highly variable with details as dependent upon combustion conditions. Our prior studies have shown soot nanostructure to be dependent upon the source via quantification of HRTEM images for nanostructural parameters. In principle this permits identification of the soot source and its contribution to any particular receptor site. Yet many structural aspects are subtle and the chemistry of and between the lamella is unaddressed. How best to bring out small differences in nanostructure and other seemingly subtle differences in chemistry? We proposed the process of pulsed laser annealing to highlight compositional and structural differences thereby distinctively and uniquely identifying the source of the soot. Our overall objective is then to develop the laser-based heating as an analytical tool and identify the process conditions and operational parameters for optimal derivitization. Specific tasks directed towards achieving this goal include 1) Identifying optimal laser operational parameters for derivitization, 2) Defining the dependence upon nanostructure and composition using model soots while also identifying variability and range of products for uniform and homogeneous starting material, 3) Demonstrating differentiation upon combustion derived soots from real engines such as diesel, gasoline, boilers, etc., and 4) Quantifying the nanostructural changes and statistical differences between the derivatives of these actual samples to formulate statistical confidence intervals for nanostructure parameters of the derivatized soots. Results will be presented accordingly.