Abstract
Metallic nanoparticles, such as gold and silver nanoparticles, can self-assemble into highly ordered arrays known as supercrystals for potential applications in areas such as optics, electronics, and sensor platforms. Here we report the formation of self-assembled 3D faceted gold nanoparticle supercrystals with controlled nanoparticle packing and unique facet-dependent optical property by using a binary solvent diffusion method. The nanoparticle packing structures from specific facets of the supercrystals are characterized by small/wide-angle X-ray scattering for detailed reconstruction of nanoparticle translation and shape orientation from mesometric to atomic levels within the supercrystals. We discover that the binary diffusion results in hexagonal close packed supercrystals whose size and quality are determined by initial nanoparticle concentration and diffusion speed. The supercrystal solids display unique facet-dependent surface plasmonic and surface-enhanced Raman characteristics. The ease of the growth of large supercrystal solids facilitates essential correlation between structure and property of nanoparticle solids for practical integrations.
Highlights
Metallic nanoparticles, such as gold and silver nanoparticles, can self-assemble into highly ordered arrays known as supercrystals for potential applications in areas such as optics, electronics, and sensor platforms
The NPs formed hexagonal close packed symmetry as confirmed by SAXS patterns, while isotropic interactions between the NPs are revealed by WAXS measurements
The product SCs displayed highly faceted hexagonal disk shape and size up to tens of micrometers (Fig. 1b). Such morphology suggested a hexagonal packing of the constituent NPs. It was confirmed by high-resolution scanning electron microscopy (SEM) image of the SC surface (Fig. 1c), which revealed a nearly perfect hexagonal close-packing array
Summary
Metallic nanoparticles, such as gold and silver nanoparticles, can self-assemble into highly ordered arrays known as supercrystals for potential applications in areas such as optics, electronics, and sensor platforms. We report the formation of self-assembled 3D faceted gold nanoparticle supercrystals with controlled nanoparticle packing and unique facetdependent optical property by using a binary solvent diffusion method. Metallic and semiconductor nanoparticles (NPs) have been widely researched in terms of their ability to selfassemble into ordered supercrystals (SCs)[1,2,3,4,5,6,7] These SCs displayed the intrinsic characteristics which belong to individual NP building blocks and unique collective optical, electronic, and mechanical properties which are tunable by the mesostructure[8,9]. Through combined simulation and controlled kinetic investigation, we discover that the size and quality of the SCs are determined by initial NP concentration and diffusion speed These SCs are large enough to be readily manipulated and characterized by techniques designed for macroscopic specimens. Optical spectroscopy results reveal strong surface-enhanced Raman scattering (SERS) effect from the SC solids and unique facet-dependent plasmonic resonance
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