Laser-Based Metrology for Engineered Aerosolized Nanoparticles

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Nanoparticles are prominent at the frontiers of material science, and are critical to Canada's manufacturing sector. Their unique mechanical, chemical, and electromagnetic properties are used to enhance a wide range of materials, and are the basis of exciting new technologies. Since their functionality depends strongly on their size, however, Canadian industry urgently needs a diagnostic that can make temporally- and spatially-resolved size measurements on aerosols of engineered nanoparticles to fully realize their commercial potential. The goal of the proposed research is to transform time-resolved laser-induced incandescence (TiRe-LII), a combustion diagnostic presently used to measure soot, into a new tool for sizing synthetic aerosolized nanoparticles. TiRe-LII uses a laser pulse to energize a sample of nanoparticles, and their spectral incandescence is recorded as they re-equilibrate with the surrounding gas. Since larger nanoparticles cool more slowly than smaller ones, the nanoparticle size distribution can be inferred from the LII signal decay. There are two challenges in extending TiRe-LII to new aerosols: first, interpreting TiRe-LII data requires an accurate model of the heat transfer between the laser-energized nanoparticles and surrounding gas; and second, inferring particle sizes from the TiRe-LII data is complicated by the fact that the LII signal is due to emission from a range of particle sizes, so inferring the particle size distribution from this data is mathematically ill-posed. The research will address these challenges by characterizing the nanoscale physics underlying heat transfer through experimental analysis and numerical simulation, and developing a mathematical algorithm for recovering nanoparticle size distributions. Knowledge gained through this research will lead to a potent new tool for Canada's nascent nanofabrication industry. This research will also train six graduate and three undergraduate students with experimental and analytical skills in nanotechnology, equipping them for careers in both industry and academe. These highly-qualified personnel are essential for Canada to remain at the forefront in nanotechnology.