Laser-Based Diagnostics for Aerosolized Nanoparticles

纳米粒子的独特性质使它们在材料科学的前沿占有突出地位。例如，金属纳米粒子提高了太阳能光伏电池的性能，而石墨纳米粒子使电池更小、更轻、更持久。由于纳米颗粒的功能很大程度上取决于尺寸和形状，因此需要新的工具来测量这些属性，以控制大量纳米颗粒的产生，并了解它们的成核和生长。与此同时，越来越多的注意力集中在纳米粒子如何对人类健康和环境产生不利影响上，这种影响也在很大程度上取决于其大小和形态。*** ***科学家和工程师越来越多地转向激光诱导白炽灯（LII）和多角度弹性光散射（MAELS）来表征合成纳米颗粒。然而，这两种技术仍然存在重大问题。LII研究人员已经推导出越来越复杂的测量模型来解释数据，而不考虑模型复杂性如何影响LII导出估计的可靠性，而LII数据中一些常见的光谱特征完全无法进行物理解释。在MAELS的情况下，光散射模型中的小误差被数据反演放大为恢复参数的大偏差。这些缺陷限制了从这些诊断中得出的纳米颗粒相关数量的可靠性。******拟议的研究计划将通过改进LII和MAELS测量模型来解决这些缺点，其长期目标是开发可靠的基于激光的纳米颗粒诊断。研究将从LII光谱子模型的理论和实验研究开始，重点关注激光激发过程中可能在纳米颗粒周围形成的微等离子体。同时，申请人的团队将使用贝叶斯技术推导出金属纳米颗粒的可靠的LII和MAELS测量模型，然后将其扩展到更复杂的煤烟情况。最后，这些算法将被整合到LII-MAELS仪器中，该仪器可以同时测量雾化纳米聚集体的主要颗粒直径、体积分数、旋转半径和分形维数。******通过这项研究开发的计量技术将被加拿大新兴的纳米技术工业用于开发新产品和材料，并帮助保护加拿大的环境和加拿大人的健康。更重要的是，这项研究将提高我们对光-纳米粒子相互作用的理解，并提供一种在其他测量方式无法达到的极端温度下估计热物理性质的方法。最后，这项研究将使9名HQP具备实验、理论分析和数值模拟的技能，为他们在工业界和学术界的职业生涯做好准备。

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.