Synthesis, Mass Spectrometry, and Atomic Structural Analysis of Au∼2000(SR)∼290 Nanoparticles

Metallic nanoparticles display unique optical, electronic, and chemical properties compared to their bulk counterparts. These properties are influenced by the internal structure of nanoparticles. Therefore, atomic structural characterization of nanoparticles is of paramount importance in nanotechnology. In this work, we present the synthesis, mass spectrometry, and structural characterization of highly monodisperse thiolate-protected gold nanoparticles (similar to 3.8 nm) using aberration-corrected scanning transmission electron microscopy (STEM). Mass spectrometry reveals the composition to be Au-similar to 2000(SC6H13)(similar to 290). The images registered in the high-angle annular dark field detector (HAADF-STEM) showed the presence of decahedral and single-crystal face-centered cubic (fcc) nanoparticles as well as fcc structures with multiple planar defects. We also observed nanoparticles with an inner grain boundary corresponding to a high-angle grain boundary classified as Sigma 9 under the coincidence site lattice notation. Experimental structural analysis and characterization of grain boundaries were correlated with simulated HAADF-STEM images of structural models for Sigma 9. The present report demonstrates the coexistence of two crystallites within thiolate-protected nanoparticles separated by high-angle grain boundaries.