Eutectic Combinations as a Pathway to the Formation of Substrate‐Based Au‐Ge Heterodimers and Hollowed Au Nanocrescents with Tunable Optical Properties

Abstract

Pairs of immiscible elements with deep eutectics are used to synthesize periodic arrays of heterodimers and hollowed metal nanocrescents. In the devised route, substrate-immobilized Au or Ag nanostructures act as heterogeneous nucleation sites for Ge adatoms. At elevated temperatures the adatoms collect in sufficient quantities to transform each site into a AuGe liquid alloy which, upon cooling, phase separates into elemental components sharing a common interface. The so-formed Au-Ge and Ag-Ge heterodimers exhibit a complex morphology characterized by a noble metal nanocrescent which partially encapsulates one end of the Ge domain. Through the use of a selective etch the Ge component is removed, leaving behind a periodic array of hollow noble metal nanocrescents on the surface of the substrate. Optical characterization of both the heterodimers and nanocrescents indicates that the presence of Ge gives rise to a relative blue-shift in the localized surface plasmon peak, a result that is in stark contrast to the red-shifts typically observed when plasmonic nanostructures are in contact with a dielectric medium. Simulations are used to both rationalize the observed shift and show the potential for deriving unexpected behaviors when semishell-like noble metal structures are in contact with high permittivity dielectric mediums.

Layered Seed-Growth of AgGe Football-like Microspheres via Precursor-Free Picosecond Laser Synthesis in Water

“…Considering the strength and diversity of laser synthesis of alloys 53 , this ligand-free layered formation mechanism may pave the way to fabricate more nanomaterials for multiple applications in biology, catalysis and energy fields. These synthesized football-like AgGe particles may possess tunable optical properties for photonic applications 54 .…”

Photocatalytic Enhancements to the Reduction of 4-Nitrophenol by Resonantly Excited Triangular Gold–Copper Nanostructures

“…[35][36][37][38] The processing temperature is chosen such that heterogeneous nucleation at the Au nanostructure is permissible while homogeneous nucleation is forbidden. As a consequence, the composition and shape of the Au nanostructures can be fundamentally altered while inhibiting the formation of new nanostructures elsewhere on the substrate.…”

Transformation of truncated gold octahedrons into triangular nanoprisms through the heterogeneous nucleation of silver

“…Previously, we demonstrated the utility of using substrateimmobilized Au nanostructures as templates capable of directing high temperature assembly. [33][34][35] In these processes, Au nanostructures are confined between an oxide substrate and a second material from which adatoms can be sourced through sublimation. At the assembly temperature these adatoms are unable to spontaneously form stable clusters on the substrate surface.…”

“…When they encounter a Au template, however, they are readily incorporated to form a new nanostructure with its own unique properties. This strategy has been demonstrated for scenarios where Au is transformed into an alloy, 34,35 where it forms a eutectic liquid which upon cooling phase separates into a heterodimer structure 33 and where the Au template is sacrificed and replaced with a Wulffshaped Pd nanostructure. 34 Here, we demonstrate that an analogous strategy can be used to transform Wulff-shaped Au nanostructures into triangular AuAg nanoprisms.…”