Localized surface plasmon resonances (LSPRs) have a broad technology potential as an attractive platform for surface-enhanced spectroscopies, non-bleaching labels, hyperthermal cancer therapy, waveguides, and so on. Most plasmonic metals studied to date are composed of either copper, silver, or gold. The former two can pose significant challenges related to oxidation, the latter is often perceived as cost-prohibitive, and all three are rare. Aluminum has emerged over the past two decades as an earth-abundant alternative; its performance in the UV is exceptional but its LSPR quality factor sharply decrease in the red region owing to losses attributed to interband transitions.
One of the newest metals for plasmonics is magnesium. It is earth-abundant, biocompatible, and has a higher plasmonic quality factor than aluminum across the visible (and than gold and copper in the blue). In the past ten years, several fabricated magnesium structures have emerged, demonstrating the optical behaviors expected of plasmonic metals. Our group has chosen a different approach: we have developed colloidal, scalable batch and flow syntheses capable of size control from ~50 to 1000 nm. This enabled to study the fascinating size and shape-dependent optical, chemical, crystallographic and catalytic properties of these novel structures.
This talk will review the advances we have made over the past four years. The unusual shapes of single crystal and twinned magnesium crystals, owing to its HCP structure, will first be discussed, followed by the formation and stability of the native oxide layer. Then, approaches to control nanoparticle shape will be presented, followed by experimental and numerical results on the plasmonic properties of colloidal magnesium, both far-field and near-field. Finally, our approach to exploiting the chemical reactivity of magnesium for galvanic replacement, and the bimetallic plasmonic-catalyst structures obtained, will be reviewed.