Multiple surface plasmon resonances in silver and copper nanorods

Single-component silver and copper nanorods were synthesized by employing the electrochemical deposition of Ag and Cu materials into the pores of anodized aluminium oxide templates. Ni blocks that were predeposited into AAO nanochannels served as a sacrificial layer for detaching the synthesized Ag and Cu nanorods from the AAO templates. Residual Ni blocks could be effectively separated from the nanorod solution by applying a magnetic field. This separation concept allows one to synthesize less noble metals like Ag and Cu into a nanorod shape using AAO electrochemical deposition methods. This paper also presents the variation in the localized surface plasmon resonance (LSPR) modes of the resulting Ag and Cu single-component nanorods as a function of the aspect ratio. Transverse and multiple longitudinal modes were observed when the aspect ratio was greater than ca. 4 for both cases. The optical property of each nanorod was calculated using the discrete dipole approximation and showed good agreement with the experimental measurements.