Département de Santé environnementale et Santé au travail, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada.
J Occup Environ Hyg. 2013;10(3):155-72. doi: 10.1080/15459624.2012.760391.
This study assessed the contribution of electron microscopy to the characterization of nanoparticles and compared the degree of variability in sizes observed within each stage when sampled by two cascade impactors: an Electrical Low Pressure Impactor (ELPI) and a Micro-Orifice Uniform Deposit Impactor (MOUDI). A TiO(2) nanoparticle (5 nm) suspension was aerosolized in an inhalation chamber. Nanoparticles sampled by the impactors were collected on aluminum substrates or TEM carbon-coated copper grids using templates, specifically designed in our laboratories, for scanning and transmission electron microscopy (SEM, TEM) analysis, respectively. Nanoparticles were characterized using both SEM and TEM. Three different types of diameters (inner, outer, and circular) were measured by image analysis based on count and volume, for each impactor stage. Electron microscopy, especially TEM, is well suited for the characterization of nanoparticles. The MOUDI, probably because of the rotation of its collection stages, which can minimize the resuspension of particles, gave more stable results and smaller geometric standard deviations per stage. Our data suggest that the best approach to estimate particle size by electron microscopy would rely on geometric means of measured circular diameters. Overall, the most reliable data were provided by the MOUDI and the TEM sampling technique on carbon-coated copper grids for this specific experiment. This study indicates interesting findings related to the assessment of impactors combined with electron microscopy for nanoparticle characterization. For future research, since cascade impactors are extensively used to characterize nano-aerosol exposure scenarios, high-performance field emission scanning electron microscopy (FESEM) should also be considered.
本研究评估了电子显微镜在纳米颗粒表征中的作用，并比较了两种级联冲击器（即电子低压冲击器（ELPI）和微孔均匀沉积冲击器（MOUDI））在采样时每个阶段观察到的粒径变化程度。将 TiO(2)纳米颗粒（5nm）悬浮液在吸入室中雾化。使用专门为扫描和透射电子显微镜（SEM、TEM）分析设计的模板，通过冲击器采集的纳米颗粒收集在铝衬底或 TEM 碳涂覆的铜网格上。使用 SEM 和 TEM 对纳米颗粒进行了表征。通过基于计数和体积的图像分析，为每个冲击器阶段测量了三种不同类型的直径（内、外和圆形）。电子显微镜，特别是 TEM，非常适合纳米颗粒的表征。MOUDI 可能由于其收集阶段的旋转，这可以最小化颗粒的再悬浮，给出了更稳定的结果和每个阶段更小的几何标准偏差。我们的数据表明，通过电子显微镜估计颗粒尺寸的最佳方法将依赖于测量圆形直径的几何平均值。总体而言，对于这种特定的实验，MOUDI 和 TEM 采样技术在涂覆有碳的铜网格上提供了最可靠的数据。这项研究表明了与评估与电子显微镜结合用于纳米颗粒表征的冲击器相关的有趣发现。对于未来的研究，由于级联冲击器广泛用于表征纳米气溶胶暴露情况，因此还应考虑高性能场发射扫描电子显微镜（FESEM）。
