Laser-Based Diagnostics for Aerosolized Nanoparticles

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The unique properties of nanoparticles place them prominently at the frontiers of material science. Metal nanoparticles improve the performance solar photovoltaics, for example, while graphitic nanoparticles enable smaller, lighter, and longer-lasting batteries. Since nanoparticle functionality depends strongly on size and shape, new tools that measure these attributes are needed to control bulk nanoparticle production, and to understand their nucleation and growth. At the same time, growing attention focuses on how nanoparticles adversely affect human health and the environment, also in ways that depend strongly on size and morphology. Scientists and engineers increasingly turn to laser-induced incandescence (LII) and multiangle elastic light scattering (MAELS) to characterize synthetic nanoparticles. Nevertheless, significant issues remain with both techniques. LII researchers have derived increasingly-elaborate measurement models for interpreting data without considering how model complexity impacts the reliability of LII-derived estimates, while several commonly-observed spectral features in LII data elude physical interpretation altogether. In the case of MAELS, small errors in the light scattering model are amplified by data inversion into large biases in recovered parameters. These deficiencies limit the reliability of nanoparticle-related quantities derived from these diagnostics. The proposed research program will address these shortcomings by improving the LII and MAELS measurement models, with the long-term goal of developing reliable laser-based nanoparticle diagnostics. Research will commence with a theoretical and experimental investigation of the LII spectroscopic submodel, focusing on a microplasma that may form around the nanoparticle during laser excitation. In parallel, the applicant's team will use Bayesian techniques to derive robust LII and MAELS measurement models for metal nanoparticles, which will then be extended to the more complex case of soot. Finally, these algorithms will be incorporated into a combined LII-MAELS instrument that simultaneously measures primary particle diameter, volume fraction, radius-of-gyration, and fractal dimension of aerosolized nanoaggregates. The metrology techniques developed through this research will be used by Canada's emerging nanotechnology industry to develop new products and materials, and help safeguard Canada's environment and the health of Canadians. More fundamentally, this research will improve our understanding of light-nanoparticle interactions, and provide a way to estimate thermophysical properties under extreme temperatures inaccessible to other measurement modalities. Finally, this research will equip nine HQP with skills in experimentation, theoretical analysis, and numerical simulation, preparing them for careers in both industry and academia.