解析数百万金纳米颗粒间的非平衡形状变异
Resolving non-equilibrium shape variations amongst millions of gold nanoparticles
AI总结：
本研究利用XFEL高通量单颗粒成像技术克服了实空间与倒易空间参数化等三大挑战，成功解析数百万金纳米颗粒的非平衡形状分布，将形状表征提升至具有统计学意义的水平。
摘要：
纳米颗粒展现出与功能相关的结构异质性，处于前沿研究的核心。如今，利用X射线自由电子激光（XFEL）的高通量单颗粒成像（SPI）为恢复数百万具有功能相关结构异质性的颗粒的形状分布创造了前所未有的机遇。为实现这一潜力，必须克服三大挑战：(1) 在实空间和倒易空间中同时参数化结构变异性；(2) 高效推断每次SPI测量的潜参数；(3) 扩展$10^5$个结构模型与$10^6$次XFEL-SPI测量之间的比较规模。在此，我们描述了如何克服这三大挑战，以解析在欧洲XFEL成像的数百万金纳米颗粒内部的非平衡形状分布。这些形状分布使我们能够量化这些颗粒的不对称程度，发现纳米颗粒间相对稳定的“形状包络”，识别与控制形状的表面活性剂相关的有限尺寸效应，并将纳米颗粒的形状外推至其理想化的热力学极限。最终，这些证明表明，XFEL SPI能够帮助将纳米颗粒形状表征从轶事性的有趣观察转变为具有统计学意义的科学结论。
英文摘要：
Nanoparticles, exhibiting functionally relevant structural heterogeneity, are at the forefront of cutting-edge research. Now, high-throughput single-particle imaging (SPI) with x-ray free-electron lasers (XFELs) creates unprecedented opportunities for recovering the shape distributions of millions of particles that exhibit functionally relevant structural heterogeneity. To realize this potential, three challenges have to be overcome: (1) simultaneous parametrization of structural variability in real and reciprocal spaces; (2) efficiently inferring the latent parameters of each SPI measurement; (3) scaling up comparisons between $10^5$ structural models and $10^6$ XFEL-SPI measurements. Here, we describe how we overcame these three challenges to resolve the non-equilibrium shape distributions within millions of gold nanoparticles imaged at the European XFEL. These shape distributions allowed us to quantify the degree of asymmetry in these particles, discover a relatively stable `shape envelope' amongst nanoparticles, discern finite-size effects related to shape-controlling surfactants, and extrapolate nanoparticles' shapes to their idealized thermodynamic limit. Ultimately, these demonstrations show that XFEL SPI can help transform nanoparticle shape characterization from anecdotally interesting to statistically meaningful.
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