Material, Size, and Environment Dependence of Plasmon-Induced Hot Carriers in Metallic Nanoparticles

Abstract

Harnessing hot electrons and holes resulting from the decay of localized surface plasmons in nanomaterials has recently led to new devices for photovoltaics, photocatalysis and optoelectronics. Properties of hot carriers are highly tunable and in this work we investigate their dependence on the material, size and environment of spherical metallic nanoparticles. In particular, we carry out theoretical calculations of hot carrier generation rates and energy distributions for six different plasmonic materials (Na, K, Al, Cu, Ag and Au). The plasmon decay into hot electron-hole pairs is described via Fermi's Golden Rule using the quasistatic approximation for optical properties and a spherical well potential for the electronic structure. We present results for nanoparticles with diameters up to 40 nm, which are embedded in different dielectric media. We find that small nanoparticles with diameters of 16 nm or less in media with large dielectric 1 arXiv:1802.05096v1 [cond-mat.mtrl-sci] 14 Feb 2018 constants produce most hot carriers. Among the different materials, Na, K and Au generate most hot carriers. We also investigate hot-carrier induced water splitting and find that simple-metal nanoparticles are useful for initiating the hydrogen evolution reaction, while transition-metal nanoparticles produce dominantly holes for the oxygen evolution reaction. Keywordshot electrons, plasmon decay, nanoparticles, water splitting, nanophotonics Energetic or "hot" electrons and holes produced by the decay of localized surface plasmons (LSP) in metallic nanostructures have recently generated much excitement. They can be harnessed in optoelectronic devices, such as photodetectors, or for solar energy conversion, i.e. in photocatalytic or photovoltaic devices. 1-8 For example, Mukherjee et al. observed that plasmon-induced hot electrons can trigger H 2 dissociation reactions on the surface of gold nanoparticles. 9 An important advantage of nanoplasmonic devices compared to traditional systems is their tunability: their optical and electronic properties depend sensitively on the nanoparticle size and shape, but also on the nanoparticle material and its environment. 10-15To guide experimental progress and identify nano-devices with favorable hot-carrier properties, a detailed theoretical understanding of the physico-chemical processes that govern hot-carrier generation is needed. However, developing such a theory is challenging because of the large size of experimentally relevant nanoparticles. Atomistic ab initio calculations are currently only feasible for metallic clusters and very small nanoparticles. 5,16,17 To model properties of experimentally relevant nanoparticles with radii of 10 nm or more, two different strategies have been employed. In many calculations, simplified models for the electronic structure of the nanoparticle are used, such as jellium models or non-interacting electron models. 18-21 For example, Manjavacas et al. employed a spherical well model to simulate hot-carrier generation in silver nanoparticles with di...

Bimetallic nanostructures: combining plasmonic and catalytic metals for photocatalysis

“…This band-structure modification also makes it difficult to predetermine the plasmonic properties of alloyed nanoparticles. There has been much progress in calculations of hot carrier generation in monometallic, traditionally plasmonic nanoparticles, but current methods cannot capture both nanoparticle size and d-band electron behavior [106,107]. A fuller theory could better inform hot carrier behavior in purely catalytic nanoparticles as well as bimetallic systems.…”

Single plasmon hot carrier generation in metallic nanoparticles

“…To model plasmon decay and hot carrier generation in nanoplasmonic systems, a semiclassical approach is usually employed 14,15 . In this approach, the metallic nanoparticle of radius R is assumed to be exposed to an incident electric field (along the z-direction) with strength E 0 .…”

“…To provide insight and guidance in this rapidly evolving field, a detailed theoretical understanding of hot electron processes, including plasmon decay, hot carrier thermalization and recombination dynamics, is needed. Using semiclassical approaches, which combine a classical description of the LSP with a quantum-mechanical description of hot carriers, several groups analyzed the distribution of hot carriers resulting from the plasmon decay and studied its dependence on the nanoparticle size, material and environment [14][15][16][17] . Providing general insight, the semiclassical approach is frequently based on a bulk dielectric function (such as a Drude model) and therefore cannot be used to describe small nanoparticles where quantum confinement effects play an important role 18,19 .…”

Plasmon‐Enhanced Photoelectrochemical Water Splitting for Efficient Renewable Energy Storage

“…[113] The generation of hot carriers has been theoretically modeled by several groups using different degrees of approximation, as discussed in detail elsewhere. [118][119][120][121][122][123][124][125] For example, Govorov and co-workers formulated a quantum theory for plasmonic hot carriers generation and injection under optical excitation. [118][119][120] Figure 9d shows an example of a nonequilibrium distribution of charge carriers in a localized plasmon wave in a metal nanostructure.…”