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Despite the interest in improving the sensitivity of optical sensors using plasmonic nanoparticles (NPs) (rods, wires, and stars), the full structural characterization of complex shape nanostructures is challenging. Here, we derive from a single scanning transmission electron microscope diffraction map (4D-STEM) a detailed determination of both the 3D shape and atomic arrangement of an individual 6-branched AuAg nanostar (NS) with high-aspect-ratio legs. The NS core displays an icosahedral structure, and legs are decahedral rods attached along the 5-fold axes at the core apexes. The NS legs show an anomalous anisotropic spatial distribution (all close to a plane) due to an interplay between the icosahedral symmetry and the unzipping of the surfactant layer on the core. The results significantly improve our understanding of the star growth mechanism. This low dose diffraction mapping is promising for the atomic structure study of individual multidomain, multibranched, or multiphase NPs, even when constituted of beam-sensitive materials.

The ability to control the surface chemistry of inorganic oxides has a profound impact on numerous applications, including lubrication, antifouling, and anticorrosion. While often overlooked as potential modifying agents given their lack of traditional functional groups, siloxanes have recently been shown to react readily with and covalently attach to inorganic oxide surfaces. Herein, we examine the reactions of cyclic siloxane vapor with solid interfaces via a ring-opening polymerization (ROP) initiated by the inherent acid/base characteristics of several smooth inorganic oxide surfaces. Surfaces are characterized by ellipsometry, dynamic contact angle analysis, and X-ray photoelectron spectroscopy (XPS). This technique requires no additional solvents and very little reactant to produce nanometer-thick hydrophobic surfaces that exhibit low contact angle hysteresis. Additional studies with particulate surfaces suggest that this method prepares conformal coatings regardless of surface architecture.