Kaegi Ralf, Fierz Martin, Hattendorf Bodo
Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600Dübendorf, Switzerland.
naneos particle solutions GmbH, Dorfstr. 69, 5210Windisch, Switzerland.
Microsc Microanal. 2021 May 11:1-9. doi: 10.1017/S1431927621000398.
The quantification of the particle size and the number concentration (PNC) of nanoparticles (NPs) is key for the characterization of nanomaterials. Transmission electron microscopy (TEM) is often considered as the gold standard for assessing the size of NPs; however, the TEM sample preparation suitable for estimating the PNC based on deposited NPs is challenging. Here, we use an ultrasonic nebulizer (USN) to transfer NPs from aqueous suspensions into dried aerosols which are deposited on TEM grids in an electrostatic precipitator of an aerosol monitor. The deposition efficiency of the electrostatic precipitator was ≈2%, and the transport efficiency of the USN was ≈7%. Experiments using SiO2 NPs (50–200 nm) confirmed an even deposition of the nebulized particles in the center of the TEM grids. PNCs of the SiO2 NPs derived from TEM images underestimated the expected PNCs of the suspensions by a factor of up to three, most likely resulting from droplet coagulation and NP aggregation in the USN. Nevertheless, single particles still dominated the PNC. Our approach results in reproducible and even deposition of particles on TEM grids suitable for morphological analysis and allows an estimation of the PNC in the suspensions based on the number of particles detected by TEM.
纳米颗粒（NP）的粒径和数量浓度（PNC）的量化是纳米材料表征的关键。透射电子显微镜（TEM）通常被视为评估NP尺寸的金标准；然而，适用于基于沉积NP估计PNC的TEM样品制备具有挑战性。在这里，我们使用超声雾化器（USN）将NP从水悬浮液转移到干燥气溶胶中，这些气溶胶沉积在气溶胶监测仪静电除尘器中的TEM网格上。静电除尘器的沉积效率约为2%，USN的传输效率约为7%。使用SiO2 NP（50-200 nm）进行的实验证实了雾化颗粒在TEM网格中心的均匀沉积。从TEM图像得出的SiO2 NP的PNC低估了悬浮液预期PNC高达三倍，这很可能是由于USN中的液滴凝聚和NP聚集所致。尽管如此，单个颗粒在PNC中仍占主导地位。我们的方法能够使颗粒在适合形态分析的TEM网格上实现可重复且均匀的沉积，并允许基于TEM检测到的颗粒数量估计悬浮液中的PNC。
