Core−Shell (Ag)Au Bimetallic Nanoparticles:  Analysis of Transmission Electron Microscopy Images

Abstract

Layered core-shell bimetallic silver-gold colloids in the size range of 10-16 nm have been prepared by the seed-growth method. Silver nuclei were covered by gold shells of various thicknesses without any stabilization agent. Interfacial (Ag)Au colloid-2,2′-bipyridine films were prepared from these bimetallic colloids and used for the purpose of analysis of transmission electron microscopy (TEM) images and electron diffraction. Both observed and calculated TEM images were used to characterize the prepared nanoparticles. On the basis of the analysis of TEM images, the calculated TEM image contrast, and results obtained by electron diffraction, energy-dispersive X-ray analysis, and other experiments, the core-shell structure of the prepared (Ag)Au nanoparticles was revealed. Particles were found to consist of a silver core and a gold shell enriched with silver.

Core-shell Au-Ag nanoparticles in dielectric nanocomposites with plasmon-enhanced fluorescence: A new paradigm in antimony glasses

“…In some cases of Au@Ag core shell NPs, where Ag 0 shell is suffi ciently thick, only the Ag 0 SPR peak is observed demonstrating their relative composition/thickness dependent optical properties [19,27,28]. Also, the TEM images of bimetallic Ag@ Au core shell NPs are known to display areas of contrasting density with the dark region attributable to gold and the light region attributable to silver [29].…”

Photon Emission Spectroscopy of Single Oxide-Supported Ag-Au Alloy Clusters

“…39 Efficient diffusion at the interface of Au shell-Ag core colloids was earlier observed by TEM and electrondiffraction experiments. 40 For Ag-coated Au particles in aqueous solution, the alloying rate was measured by x-ray absorption fine structure spectroscopy and found to be related to the presence of vacancies at the interface. 18 Optical measurements on ensembles of Ag-Au shell-core colloids in solution also revealed two extinction peaks, indicating independent plasmon excitations in shell and core of the particles.…”

Advanced Methods of Electron Microscopy in Catalysis Research

“…This has been applied successfully to image bimetallic nanoparticles down to 10 nm in diameter. Since the particles need to be in a low-index zone orientation, this method is not easy to use in practice (Srnov a-Sloufov a et al, 2000). A novel approach to study this type of particles is based on the use of an HAADF technique in a TEM, which allows the observation of the interfaces between layers of different elements due to differences in atomic number, densities, or the presence of strain fields due to differences in lattice parameters.…”