Hayashida Misa, Kumagai Kazuhiro, Malac Marek
National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Higashi, Tsukuba, Ibaraki 305-8565, Japan; National Institute for Nanotechnology (NINT), 11421 Saskatchewan Drive, Edmonton T6G 2M9, Canada.
National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Higashi, Tsukuba, Ibaraki 305-8565, Japan.
Micron. 2015 Dec;79:53-8. doi: 10.1016/j.micron.2015.08.003. Epub 2015 Aug 18.
Polystyrene latex (PSL) nanoparticle (NP) sample is one of the most widely used standard materials. It is used for calibration of particle counters and particle size measurement tools. It has been reported that the measured NP sizes by various methods, such as Differential Mobility Analysis, dynamic light scattering (DLS), optical microscopy (OM), scanning electron microscopy (SEM) and atomic force microscopy (AFM), differ from each other. Deformation of PSL NPs on mica substrate has been reported in AFM measurements: the lateral width of PSL NPs is smaller than their vertical height. To provide a reliable calibration standard, the deformation must be measured by a method that can reliably visualize the entire three dimensional (3D) shape of the PSL NPs. Here we present a method for detailed measurement of PSL NP 3D shape by means of electron tomography in a transmission electron microscope. The observed shape of the PSL NPs with 100 nm and 50 nm diameter were not spherical, but squished in direction perpendicular to the support substrate by about 7.4% and 12.1%, respectively. The high difference in surface energy of the PSL NPs and that of substrate together with their low Young modulus appear to explain the squishing of the NPs without presence of water film.
聚苯乙烯乳胶（PSL）纳米颗粒（NP）样品是应用最广泛的标准材料之一。它用于颗粒计数器和粒度测量工具的校准。据报道，通过各种方法（如差分迁移率分析、动态光散射（DLS）、光学显微镜（OM）、扫描电子显微镜（SEM）和原子力显微镜（AFM））测量的NP尺寸彼此不同。在AFM测量中已报道PSL NPs在云母基板上会变形：PSL NPs的横向宽度小于其垂直高度。为了提供可靠的校准标准，必须通过一种能够可靠地可视化PSL NPs整个三维（3D）形状的方法来测量变形。在这里，我们提出了一种在透射电子显微镜中通过电子断层扫描详细测量PSL NP 3D形状的方法。观察到直径为100 nm和50 nm的PSL NPs的形状不是球形，而是在垂直于支撑基板的方向上分别被挤压了约7.4%和12.1%。PSL NPs与基板表面能的巨大差异以及它们较低的杨氏模量似乎解释了在没有水膜的情况下NP的挤压现象。
