Surface Plasmon Coupling on Linked Au–Pt Nanorods

This work demonstrates that surface plasmon coupling in linked Au–Pt NRs (NRs) can be controlled by adjusting the relative ratio of material segment lengths. The NRs were synthesized through an anodic aluminum oxide template assisted sequential electrochemical deposition route. Optical spectra of the NRs in solution were acquired in the UV–vis–NIR region to examine surface plasmon coupling. Analysis of the spectra indicated that effective surface plasmon coupling could occur in Au-dominated NRs but not in Pt-dominated ones. The optical properties of Au–Pt–Au three-segment NRs were also examined, and the results provided further clarification regarding the conditions that yield effective coupling of NR segments in these structures. Electrodynamics calculations on two- and three-segment NRs were performed and found to be in good agreement with experiment. These findings regarding surface plasmon coupling of linked, hybrid NRs extend the fundamental knowledge of surface plasmon coupling from single component to hybrid systems and are useful for a variety of applications that necessitate fine controllability of the plasmonic properties

Galvanically Replaced Hollow Au–Ag Nanospheres: Study of Their Surface Plasmon Resonance

We synthesized hollow Au–Ag nanospheres (NSs) by employing a galvanic replacement reaction between HAuCl₄ and Ag NSs. Uniform Ag NSs with controllable sizes were synthesized as sacrificial templates by a seed-mediated strategy. The atomic ratio of Au to Ag in Au–Ag NSs was tunable by controlling the reagent concentration. UV–vis extinction spectra acquired from well-dispersed colloidal NS solutions were used to investigate the optical properties of the solutions. In addition to a common dipole mode exhibited on most transition metal nanoparticles, we observed a quadrupole plasmon resonance mode when the diameters of the Ag and Au–Ag NSs were larger than 100 nm. The quadrupole and dipole peaks both shifted to longer wavelengths with increased Au content in Au–Ag NSs. The experimental observation of optical properties of hollow Au–Ag NSs was compared with the theoretical simulation using DDA calculation, showing a good agreement

Optical Sensitivity Comparison of Multiblock Gold–Silver Nanorods Toward Biomolecule Detection: Quadrupole Surface Plasmonic Detection of Dopamine

In this work, we tested multiblock nanorods (NRs) with Au and Ag segments for the surface plasmonic detection of dopamine (DA). A change in the quadrupole surface plasmon mode was found to be sensitive to the Au/Ag block length and relative block ratio in a single NR. The surfaces of the NRs were decorated with monoclonal antibody (Mab) against DA. By comparing the results for pure Au NRs with those obtained for multiblock Au–Ag–Au NRs, we found that the magnitude of peak-shifting for the multiblock NRs was much larger than that for pure Au NRs. This result was attributed to the higher sensitivity of Ag to a change in the dielectric constant of the surrounding medium when compared to Au and the sensitive surface plasmon coupling at the junction between Au and Ag blocks. The magnitude of peak-shifting was tuned as a function of both the length of the Ag block and the number of repeating units of Au and Ag in the NRs