Controlled Synthesis of Au@AgAu Yolk–Shell Cuboctahedra with Well-Defined Facets

Abstract

The synthesis of Au@AgAu yolk-shell cuboctahedra nanoparticles formed by galvanic replacement in a seed-mediated method is described. Initially, single-crystal Au seeds are used for the formation of Au@Ag core-shell nanocubes, which serve as the template material for the deposition of an external Au layer. The well-controlled synthesis yields the formation of cuboctahedra nanoparticles with smooth inner and outer Au/Ag surfaces. The deposition/oxidation process is described to understand the formation of cuboctahedra and octahedra nanoparticles. The Au core maintains the initial morphology of the seed and remains static at the center of the yolk-shell because of residual Ag. Structural analysis of the shell indicates intrinsic stacking faults (SFs) near the surface. Energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) compositional analysis show an Au-Ag nonordered alloy forming the shell. The three-dimensional structure of the nanoparticles presented open facets on the [111] as observed by electron tomography SIRT reconstruction over a stack of high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images. The geometrical model was validated by analyzing the direction of streaks in coherent nanobeam diffraction (NBD). The catalytic activity was evaluated using a model reaction based on the reduction of 4-nitrophenol (4-NTP) by NaBH4 in the presence of Au@AgAu yolk-shell nanoparticles.

Electron Tomography: A Unique Tool Solving Intricate Hollow Nanostructures

“…Hollow nanospheres themselves can also serve as building blocks to assemble suprastructure, even possibly result in [100] Copyright 2016, American Chemical Society. d-f) Reproduced with permission.…”

“…Later studies further revealed the intermediate stage of replacement through tomographic analysis, demonstrating the dissolution of Ag and deposition of Au regrading both structural and chemical characterizations. [99,100]…”

Octahedral Cu2O@Co(OH)2 Nanocages with Hierarchical Flake‐Like Walls and Yolk‐Shell Structures for Enhanced Electrocatalytic Activity

“…The synthesis of yolk‐shell nanocages therefore would be of great significance to improve the electrocatalytic activity for electrocatalysis. Unfortunately, the development of these yolk‐shell nanocages is still insufficient, especially in facile and novel strategy for fabricating the highly efficient electrocatalysts with such unique and well‐defined structures, although some yolk‐shell nanocages have been synthesized ,,,,…”

“…[4][5][6] Yolk-shell nanomaterials are unique family of these complex architectures. Substantial efforts have been devoted to the develop of this kind of nanomaterials made of carbon, [7,8] metal oxides, [9,10] noble metals, [11,12] and metal sulfides. [13,14] As for catalysis, the yolk-shell constructions have many superior properties compared to solid and core-shell counterparts, as they could provide a typical framework in a nanoreactor.…”

“…Unfortunately, the development of these yolk-shell nanocages is still insufficient, especially in facile and novel strategy for fabricating the highly efficient electrocatalysts with such unique and welldefined structures, although some yolk-shell nanocages have been synthesized. [8,11,14,18,28] In this work, we report a facile and efficient self-templated strategy to fabricate octahedral Cu 2 O@Co(OH) 2 yolk-shell nanocages with unique crystalline-amorphous heterostructure. The crystalline Cu 2 O octahedral particles as precursors are gradually etched through coordinating etching process.…”