Quantitative Analysis of Scanning Tunneling Microscopy Images of Mixed-Ligand-Functionalized Nanoparticles
Quantitative Analysis of Scanning Tunneling Microscopy Images of Mixed-Ligand-Functionalized Nanoparticles
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DOI：
10.1021/la403546c
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发表时间：
2013-11-12
期刊：
影响因子：
3.9
通讯作者：
Stellacci, Francesco
中科院分区：
文献类型：
--
作者：
Biscarini, Fabio;Ong, Quy Khac;Stellacci, Francesco
配体保护的金纳米颗粒表现出较大的局部曲率、小尺度上快速变化的特征以及化学异质性。原则上，通过扫描隧道显微镜 (STM) 进行的成像可以提供有关配体外壳结构的直接信息，但 STM 图像需要费力的分析，并且难以解释。在这里，我们报告了一种简单、稳健且严格的方法，用于定量分析由沉积在金/云母上的功能化金纳米颗粒组成的样品的 STM 图像中包含的多尺度特征。该方法依赖于地形功率谱密度 (PSD) 的分析，使我们能够提取 STM 图像中纳米颗粒所表现出的特征的特征长度尺度。对于此处分析的混合配体保护的金纳米颗粒，特征长度尺度为 1.2 +/- 0.1 nm，而对于同源配体 Au 纳米粒子，该尺度为 0.75 +/- 0.05 nm。这些长度尺度代表独立于扫描参数的空间相关性，因此 PSD 中的特征可以归因于配体保护的纳米粒子的 STM 对比度的指纹。不同实验室使用不同显微镜和操作员记录的图像的 PSD 光谱可以在大部分频率范围内重叠，证明纳米粒子 STM 图像中的特征可以进行比较和再现。
Ligand-protected gold nanoparticles exhibit large local curvatures, features rapidly varying over small scales, and chemical heterogeneity. Their imaging by scanning tunneling microscopy (STM) can, in principle, provide direct information on the architecture of their ligand shell, yet STM images require laborious analysis and are challenging to interpret. Here, we report a straightforward, robust, and rigorous method for the quantitative analysis of the multiscale features contained in STM images of samples consisting of functionalized Au nanoparticles deposited onto Au/mica. The method relies on the analysis of the topographical power spectral density (PSD) and allows us to extract the characteristic length scales of the features exhibited by nanoparticles in STM images. For the mixed-ligand-protected Au nanoparticles analyzed here, the characteristic length scale is 1.2 +/- 0.1 nm, whereas for the homoligand Au NPs this scale is 0.75 +/- 0.05 nm. These length scales represent spatial correlations independent of scanning parameters, and hence the features in the PSD can be ascribed to a fingerprint of the STM contrast of ligand-protected nanoparticles. PSD spectra from images recorded at different laboratories using different microscopes and operators can be overlapped across most of the frequency range, proving that the features in the STM images of nanoparticles can be compared and reproduced.