Bifunctional Ag@Pd-Ag Nanocubes for Highly Sensitive Monitoring of Catalytic Reactions by Surface-Enhanced Raman Spectroscopy.

We report a route to the facile synthesis of Ag@Pd-Ag nanocubes by cotitrating Na2PdCl4 and AgNO3 into an aqueous suspension of Ag nanocubes at room temperature in the presence of ascorbic acid and poly(vinylpyrrolidone). With an increase in the total titration volume, we observed the codeposition of Pd and Ag atoms onto the edges, corners, and side faces of the Ag nanocubes in a site-by-site fashion. By maneuvering the Pd/Ag ratio, we could optimize the SERS and catalytic activities of the Ag@Pd-Ag nanocubes for in situ SERS monitoring of the Pd-catalyzed reduction of 4-nitrothiophenol by NaBH4.