Correlating Catalytic Activity of Ag–Au Nanoparticleswith 3D Compositional Variations.

Significant elemental segregationis shown to exist within individualhollow silver–gold (Ag–Au) bimetallic nanoparticlesobtained from the galvanic reaction between Ag particles and AuCl4–. Three-dimensional compositional mappingusing energy dispersive X-ray (EDX) tomography within the scanningtransmission electron microscope (STEM) reveals that nanoparticlesurface segregation inverts from Au-rich to Ag-rich as Au contentincreases. Maximum Au surface coverage was observed for nanoparticleswith approximately 25 atom % Au, which correlates to the optimal catalyticperformance in a three-component coupling reaction among cyclohexanecarboxyaldehyde, piperidine, and phenylacetylene. [ABSTRACT FROM AUTHOR]