Anomalous nanoparticle surface diffusion in LCTEM is revealed by deep learning-assisted analysis
Anomalous nanoparticle surface diffusion in LCTEM is revealed by deep learning-assisted analysis
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DOI：
10.1073/pnas.2017616118
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发表时间：
2021-03-09
影响因子：
11.1
通讯作者：
Alivisatos, A. Paul
中科院分区：
文献类型：
--
作者：
Jamali, Vida;Hargus, Cory;Alivisatos, A. Paul
纳米粒子在表面附近的运动在物理学、生物学和化学中具有根本的重要性。液体池透射电子显微镜（LCTEM）是一种很有前途的高空间分辨率研究纳米粒子运动的技术。然而，缺乏对显微镜的电子束如何影响颗粒运动的理解阻碍了使用LCTEM在界面处原位跟踪单个纳米颗粒和大分子的进展。在这里，我们实验研究了分散在水中的金纳米颗粒的模型系统的运动，并在宽范围的电子束剂量率移动到商业LC的氮化硅膜附近。我们发现，纳米粒子表现出异常的扩散行为调制的电子束剂量率。我们使用卷积深度神经网络模型和规范统计测试来表征LCTEM中纳米颗粒的异常扩散。结果表明，纳米粒子的运动是由分数布朗运动在低剂量率，类似于在粘弹性介质中的扩散，和连续时间的随机行走在高剂量率，类似于扩散的能量景观钉扎网站。这两种行为可以解释的硅醇分子物种的氮化硅膜的表面上的存在和离子物种在溶液中形成的水在存在的电子束的辐解。
The motion of nanoparticles near surfaces is of fundamental importance in physics, biology, and chemistry. Liquid cell transmission electron microscopy (LCTEM) is a promising technique for studying motion of nanoparticles with high spatial resolution. Yet, the lack of understanding of how the electron beam of the microscope affects the particle motion has held back advancement in using LCTEM for in situ single nanoparticle and macromolecule tracking at interfaces. Here, we experimentally studied the motion of a model system of gold nanoparticles dispersed in water and moving adjacent to the silicon nitride membrane of a commercial LC in a broad range of electron beam dose rates. We find that the nanoparticles exhibit anomalous diffusive behavior modulated by the electron beam dose rate. We characterized the anomalous diffusion of nanoparticles in LCTEM using a convolutional deep neural-network model and canonical statistical tests. The results demonstrate that the nanoparticle motion is governed by fractional Brownian motion at low dose rates, resembling diffusion in a viscoelastic medium, and continuous-time random walk at high dose rates, resembling diffusion on an energy landscape with pinning sites. Both behaviors can be explained by the presence of silanol molecular species on the surface of the silicon nitride membrane and the ionic species in solution formed by radiolysis of water in presence of the electron beam.