Hot Electrons and Electromagnetic Effects in the Broadband Au, Ag, and Ag–Au Nanocrystals: The UV, visible, and NIR Plasmons

Abstract

Energetic and optical properties of plasmonic nanocrystals strongly depend on their sizes, shapes, and composition. Whereas the use of plasmonic nanoparticles in biotesting has become routine, applications of plasmonics in energy are still early in development. Here, we investigate hot-electron (HE) generation and related electromagnetic effects in both mono-and bimetallic nanorods (NRs) and focus on a promising type of bimetallic nanocrystal−core− shell Au−Ag nanorods. The spectra of the NRs are broadband, highly tunable with their geometry, and exhibit few plasmon resonances. In this work, we provide a new quantum formalism describing the HE generation in bimetallic nanostructures. Interestingly, we observe that the HE generation rate at the UV plasmon resonance of Au−Ag NRs appears to be very high. These HEs are highly energetic and suitable for carbon-fuel reactions. Simultaneously, the HE generation at the longitudinal plasmon (L-plasmon) peaks, which can be tuned from the yellow to near-IR, depends on the near-field and electromagnetic Mie effects, limiting the HE efficiencies for long and large NRs. These properties of the L-plasmon relate to all kinds of NRs (Au, Ag, and Au−Ag). We also consider the generation of the interband d-holes in Au and Ag, since the involvement of the d-band is crucial for the energetic properties of UV plasmons. The proposed formalism is a significant development for the description of bimetallic (or trimetallic, or more complex) nanostructures, and paving the way for the efficient application of the photophysical mechanisms based on the plasmonic HEs and hot holes in sensing, nanotechnology, photocatalysis, and electrophotochemistry.

Bound States in the Continuum for Hot Electron Generation in Integrated-Resonant Metasurfaces

“…Hot electrons are typically generated near the surface of the metal and can be injected into adsorbed molecules at the interface between the silver disk and the SiO 2 layer. To quantitatively describe hot electron generation, here, we calculate the generation rate of hot electrons as ,− rate HEG = 1 4 2 π 2 e 0 2 E normalF 2 ℏ false( ℏ ω − normalΔ E b false) false( ℏ ω ) 4 ∫ false| E | 2 normald S where e 0 means electron charge, E F denotes the Fermi energy of metal, ℏ is the reduced Planck constant, and ω is the photon angular frequency. The term Δ E b , understood as an energy barrier, may represent not just the height of the electronic barrier between the plasmonic material and the semiconductor contact but also the energy gap between the Fermi level and the level of adsorbed molecules. , In this work, we set Δ E b = 1 eV as a typical energy difference for molecules that can be attached to the metal–dielectric interface.…”

Hot carrier creation in a nanoparticle dimer-molecule composite

“…1–10 These HCs can be transferred to chemically attached acceptors like molecules, which, when properly extracted, could increase the efficiency of various processes and devices like solar cells, water splitting, and photocatalysis. 11–20 For instance, Mukherjee and colleagues demonstrated that challenging chemical reactions like H 2 molecule dissociation on Au surfaces can be initiated by hot electrons (HEs). 21 The energy distribution of HCs can be tuned relative to the size, shape, and elemental composition of the nanostructure.…”