Tri-Component Gold–Nickel–Silver Nanorods Leading to Multiple Surface Plasmon Bands

In this work, we demonstrate that surface plasmon resonance coupling can occur on elementally different three-block metal nanorods. The nanorods were composed of three sequential Au–Ni–Ag components prepared with electrochemical deposition and an anodic aluminum oxide template. We investigated the UV–vis–NIR extinction spectroscopy of colloidal nanorods in D2O liquid phase and found that surface plasmon coupling occurred on optically active Au and Ag motifs in nanorods when the middle Ni block was sufficiently short. As a result, both the longitudinal and transverse plasmon modes appeared clearly in the optical spectra of samples for the total nanorod lengths rather than for individual constituent sub-nanorods. Higher-order modes, such as quadrupole modes, also arose on the longer hybrid nanorods. Nanorods with a Ni portion longer than the corresponding Au and Ag portions could restrain coupling between the Au and Ag segments.