Soot differentiation by laser derivatization

Combustion produced soot is highly variable in its composition and nanostructure, both of which are dependent upon combustion conditions. Quantification of high-resolution transmission electron microscopy (HRTEM) images for nanostructure parameters shows that soot nanostructure is dependent upon its source. In principle, this permits identification of the soot and its contribution to any pollution monitoring receptor site. Many structural and chemical aspects are subtle, unaccounted for in direct nanostructure quantification. The process of pulsed laser annealing is demonstrated to enhance slight differences in nanostructure and chemical composition. Chemistry-based limitations imposed due to nanosecond heating and microsecond cooling timescales highlight these initial compositional and structural differences—as dependent upon source-specific formation conditions. This study demonstrates laser-based heating as an analytical tool for soot differentiation by formation conditions/source by identifying operational parameters for optimal derivatization. Nanostructure changes are qualitatively shown using HRTEM and quantified using image-based fringe analysis for real and model soots.