Agradecimentos: Microscopy analysis was performed at the Kleberg Advanced Microscopy Center at UTSA. The authors thank the support from the Department of Defense W911NF-18-1-0439, Conacyt A1-S-35309, and The Welch Foundation #AX-1857, "Fundamental Chemical Research on Larger Molecular Noble Metal Clusters". C.K. and A.D. gratefully acknowledge support from NSF grant CHE-1255519. D.U. acknowledges financial support from CNPq (grant. 402571/2016-9) Ver menos

Abstract: Atomic pair distribution function (PDF) analysis has been widely used to investigate nanocrystalline and structurally disordered materials. Experimental PDFs retrieved from electron diffraction (ePDF) in transmission electron microscopy (TEM) represent an attractive alternative to traditional PDF obtained from synchrotron X-ray sources, particularly for studying minute samples. Nonetheless, the inelastic scattering produced by the large dynamical effects of electron diffraction may obscure the interpretation of ePDF. In the present work, precession electron diffraction (PED-TEM) has been employed to obtain the ePDF of two different samples-lipoic acid- and hexanethiolate-capped gold nanoparticles (similar to 4.5 and 4.2 nm, respectively) randomly oriented and measured at both liquid nitrogen and room temperatures. The electron diffraction data were processed to obtain ePDFs which were subsequently compared with the PDF of different ideal structure models. The results demonstrate that the PED-ePDF data are sensitive to different crystalline structures such as monocrystalline (truncated octahedra) and multiply twinned (decahedra, icosahedra) structures. The results indicate that PED reduces the residual from 46 to 29%; in addition, the combination of PED and low temperature further reduced the residual to 23%, which is comparable to X-ray PDF analysis. Furthermore, the inclusion of PED resulted in a better estimation of the coordination number from ePDF. To the best of our knowledge, the precessed electron-beam technique (PED) has not been previously applied to nanoparticles for analysis by the ePDF method Ver menos