Multiple Surface Plasmon Modes for Gold/Silver Alloy Nanorods

Alloy nanorods consisting of bimetallic gold and silver are synthesized by employing the electrochemical codeposition of Au/Ag alloy materials into the pores of anodized aluminum oxide templates. This paper presents the variation of localized surface plasmon resonance (LSPR) modes of the Au_x/Ag_1−x alloy nanorods as a function of relative compositions of Au and Ag. Transverse and multiple longitudinal modes were observed when the length was longer than ca. 300 nm. For a given length, the transverse LSPR mode systematically blue-shifted as the Ag portion increased, while there was little variation in peak positions of the longitudinal LSPR modes. The optical properties of the Au_x/Ag_1−x alloy nanorods were calculated using the discrete dipole approximation and showed a good agreement with the experimental measurements.