Laser-Based Metrology for Engineered Aerosolized Nanoparticles

纳米粒子在材料科学的前沿是突出的，对加拿大的制造业至关重要。它们独特的机械、化学和电磁特性被用于增强各种材料，并且是令人兴奋的新技术的基础。然而，由于它们的功能很大程度上取决于它们的大小，加拿大工业界迫切需要一种能够对工程纳米颗粒气溶胶进行时间和空间分辨尺寸测量的诊断方法，以充分实现其商业潜力。拟议研究的目标是将时间分辨激光诱导白炽灯（TiRe-LII），一种目前用于测量烟灰的燃烧诊断方法，转变为一种测定合成雾化纳米颗粒尺寸的新工具。TiRe-LII使用激光脉冲为纳米颗粒样品通电，当它们与周围气体重新平衡时，它们的光谱白炽被记录下来。由于较大的纳米颗粒比较小的纳米颗粒冷却得更慢，因此可以从LII信号衰减推断纳米颗粒的尺寸分布。将TiRe-LII扩展到新型气溶胶中存在两个挑战：首先，解释TiRe-LII数据需要一个激光激发的纳米颗粒与周围气体之间传热的精确模型；其次，从TiRe-LII数据推断颗粒大小是很复杂的，因为LII信号是由一系列颗粒大小的发射引起的，所以从这些数据推断颗粒大小分布在数学上是不适定的。该研究将通过实验分析和数值模拟来表征传热背后的纳米尺度物理，并开发一种恢复纳米颗粒尺寸分布的数学算法，从而解决这些挑战。通过这项研究获得的知识将为加拿大新生的纳米制造工业带来强有力的新工具。这项研究还将培训六名研究生和三名本科生，使他们具备纳米技术的实验和分析技能，为他们在工业界和学术界的职业生涯做好准备。这些高素质的人才对加拿大在纳米技术领域保持领先地位至关重要。

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.