Abstract：
A variety of scattering-based, microscopy-based, and mobility-based methods are frequently used to probe the size distributions of colloidal nanoparticles with transmission electron microscopy (TEM) often considered to be the \"gold standard\". Charge detection mass spectrometry (CDMS) is an alternative method for nanoparticle characterization that can rapidly measure the mass and charge of individual nanoparticle ions with high accuracy. Two low polydispersity, ∼100 nm diameter nanoparticle size standards with different compositions (polymethyl methacrylate/polystyrene copolymer and 100% polystyrene) were characterized using both TEM and CDMS to explore the merits and complementary aspects of both methods. Mass and diameter distributions are rapidly obtained from CDMS measurements of thousands of individual ions of known spherical shape, requiring less time than TEM sample preparation and image analysis. TEM image-to-image variations resulted in a ∼1-2 nm range in the determined mean diameters whereas the CDMS mass precision of ∼1% in these experiments leads to a diameter uncertainty of just 0.3 nm. For the 100% polystyrene nanoparticles with known density, the CDMS and TEM particle diameter distributions were in excellent agreement. For the copolymer nanoparticles with unknown density, the diameter from TEM measurements combined with the mass from CDMS measurements enabled an accurate measurement of nanoparticle density. Differing extents of charging for the two nanoparticle standards measured by CDMS show that charging is sensitive to nanoparticle surface properties. A mixture of the two samples was separated based on their different extents of charging despite having overlapping mass distributions centered at 341.5 and 331.0 MDa.
摘要：
各种基于散射的，基于显微镜，通常使用基于迁移率的方法来探测胶体纳米颗粒的尺寸分布，透射电子显微镜（TEM）通常被认为是“金标准”。电荷检测质谱（CDMS）是一种用于纳米粒子表征的替代方法，可以高精度地快速测量单个纳米粒子离子的质量和电荷。两个低的多分散性，使用TEM和CDMS表征具有不同组成（聚甲基丙烯酸甲酯/聚苯乙烯共聚物和100％聚苯乙烯）的100nm直径纳米颗粒尺寸标准，以探索两种方法的优点和互补方面。通过CDMS测量数千个已知球形的单个离子，可以快速获得质量和直径分布。需要更少的时间比TEM样品制备和图像分析。TEM图像到图像的变化导致在确定的平均直径中的~1-2nm范围，而这些实验中的CDMS质量精度~1％导致直径不确定性仅为0.3nm。对于已知密度的100%聚苯乙烯纳米颗粒，CDMS和TEM粒径分布非常吻合。对于密度未知的共聚物纳米粒子，来自TEM测量的直径与来自CDMS测量的质量相结合使得能够精确测量纳米颗粒密度。通过CDMS测量的两种纳米颗粒标准品的不同充电程度表明充电对纳米颗粒表面性质敏感。尽管具有以341.5和331.0MDa为中心的重叠质量分布,但基于它们不同的充电程度来分离两种样品的混合物。
