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Cu is an inexpensive alternative plasmonic metal with optical behaviour comparable to Au but with much poorer environmental stability. Alloying with a more stable metal can improve stability and add functionality, with potential effects on the plasmonic properties. Here we investigate the plasmonic behaviour of Cu nanorods and Cu–CuPd nanorods containing up to 46 mass percent Pd. Monochromated scanning transmission electron microscopy electron energy-loss spectroscopy first reveals the strong length dependence of multiple plasmonic modes in Cu nanorods, where the plasmon peaks redshift and narrow with increasing length. Next, we observe an increased damping (and increased linewidth) with increasing Pd content, accompanied by minimal frequency shift. These results are corroborated by and expanded upon with numerical simulations using the electron-driven discrete dipole approximation. This study indicates that adding Pd to nanostructures of Cu is a promising method to expand the scope of their plasmonic applications.
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Plasmon Hybridizations in Compound Nanorod–Nanohole Arrays
This study shows that a hybridized plasmonic mode, represented by an additional transmission peak, in a compound structure consisting of a nanorod embedded in a nanohole can be effectively described as a quasi-dipole oscillator. When two nanorods are introduced into a nanohole, these two quasi-dipoles can couple and hybridize, giving rise to two additional transmission peaks in the enhanced optical transmission spectrum. The relative intensities of these peaks can be con-trolled by adjusting the incident polarization, while their separations can be tuned by modifying the length of the nanorods. The concept of quasi-dipoles in compound nanohole structures can be further extended to predict the coupling behavior of even more complex compound configura-tions, such as multiple nanorods within nanoholes, resulting in the generation of multiple hy-bridization states. Consequently, the shape and response of the transmission peaks can be pre-cisely engineered. This strategy could be used to design nanohole-based metasurfaces for applica-tions such as ultra-thin optical filters, waveplates, polarizers, etc.
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- Award ID(s):
- 1808271
- PAR ID:
- 10434045
- Date Published:
- Journal Name:
- Nanomaterials
- ISSN:
- 2079-4991
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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