De Caro Liberato, Scattarella Francesco, Altamura Davide, Arciniegas Milena P, Siliqi Dritan, Manna Liberato, Giannini Cinzia
Istituto di Cristallografia, CNR, via Amendola 122/O, Bari, Italy.
Nanochemistry Department, Istituto Italiano di Tecnologia, via Morego 30, Genova, Italy.
J Appl Crystallogr. 2020 May 27;53(Pt 3):741-747. doi: 10.1107/S160057672000583X. eCollection 2020 Jun 1.
This work describes the application of X-ray ptychography for the inspection of complex assemblies of highly anisotropic nanocrystals embedded in a thick polymer matrix. More specifically, this case deals with CdSe/CdS octapods, with pod length = 39 ± 2 nm and pod diameter = 12 ± 2 nm, dispersed in free-standing thick films (24 ± 4 µm) of polymethyl methacrylate and polystyrene, with different molecular weights. Ptychography is the only imaging method available to date that can be used to study architectures made by these types of nanocrystals in thick polymeric films, as any other alternative direct method, such as scanning/transmission electron microscopy, can be definitively ruled out as a result of the large thickness of the free-standing films. The electron density maps of the investigated samples are reconstructed by combining iterative difference map algorithms and a maximum likelihood optimization algorithm. In addition, post image processing techniques are applied to both reduce noise and provide a better visualization of the material morphological details. Through this process, at a final resolution of 27 nm, the reconstructed maps allow us to visualize the intricate network of octapods inside the polymeric matrices.
这项工作描述了X射线叠层成像技术在检测嵌入厚聚合物基质中的高度各向异性纳米晶体复杂组件方面的应用。更具体地说，此案例涉及CdSe/CdS八足体，其足长为39±2 nm，足直径为12±2 nm，分散在不同分子量的聚甲基丙烯酸甲酯和聚苯乙烯的自支撑厚膜（24±4 µm）中。叠层成像技术是目前唯一可用于研究由这类纳米晶体在厚聚合物薄膜中构成的结构的成像方法，因为任何其他直接方法，如扫描/透射电子显微镜，由于自支撑薄膜的厚度较大而肯定不可行。通过结合迭代差分图算法和最大似然优化算法来重建所研究样品的电子密度图。此外，应用图像后处理技术来降低噪声并更好地可视化材料的形态细节。通过这个过程，在最终分辨率为27 nm时，重建的图谱使我们能够可视化聚合物基质内八足体的复杂网络。
