Simple electrochemical synthesis of an Au-Ag-Cu trimetallic nanodendrite and its use as a SERS substrate

Abstract

An Au-Ag-Cu trimetallic nanodendrite was constructed by simple electrochemical methods and was evaluated as a surface enhanced Raman scattering (SERS) substrate. The motivation was to harmonize the individual merits of each SERS-active metal, the higher SERS efficiency of Ag, good surface stability of Au, and structural stability of Cu, in a single structure. For the fabrication, a Cu flower-like nanostructure was initially constructed by reduction of Cu2+ (electrodeposition). Next, a galvanic replacement reaction (GRR) was performed on the Cu framework in a solution of Ag+ to build Ag nanodendrites with coincidental release of Cu atoms into the solution as Cu2+. As the Ag nanodendrite grew, released Cu2+ redeposited, so a Ag-Cu bimetallic nanodendrite started to form. Next, a second GRR was performed with the newly prepared Ag-Cu nanodendrite in Au3+ solution to partially replace Ag and Cu by Au to construct the Au-Ag-Cu trimetallic nanodendrite. Based on examination of Raman peaks of rhodamine 6G (R6G, a reporter molecule), the Ag-Cu nanodendrite resulted in approximately 2.6 fold higher peak intensity compared to a Ag nanodendrite. Subsequent Au incorporation into the Ag-Cu nanodendrite greatly improved the stability of SERS measurements as well as increased the peak intensity further by 7.6 fold, thereby enabling the observation of Raman peaks of a 10(-10) M R6G sample.