Plasmonic nanocrystals with complex shapes for photocatalysis and growth: Contrasting anisotropic hot-electron generation with the photothermal effect

TL;DR

This paper develops a microscopic theory to describe hot-electron generation and photothermal effects in complex-shaped plasmonic nanocrystals, revealing position-dependent anisotropic hot-carrier distributions crucial for photocatalysis.

Contribution

It introduces a formalism that captures the spatial and mechanistic details of hot-electron and photothermal generation in complex plasmonic nanostructures, advancing design principles for nanoantennas.

Findings

Hot-electron generation is strongly position-dependent and anisotropic.

Photothermal effects are nearly uniform across the nanocrystal surface.

Multiple mechanisms contribute to hot-carrier generation, reflecting nanocrystal structure.

Abstract

In plasmonics, and particularly in plasmonic photochemistry, the effect of hot-electron generation is an exciting phenomenon driving new fundamental and applied research. However, obtaining a microscopic description of the hot-electron states represents a challenging problem, limiting our capability to design efficient nanoantennas exploiting these excited carriers. This paper addresses this limitation and studies the spatial distributions of the photophysical dynamic parameters controlling the local surface photochemistry on a plasmonic nanocrystal. We found that the generation of energetic electrons and holes in small plasmonic nanocrystals with complex shapes is strongly position-dependent and anisotropic, whereas the phototemperature across the nanocrystal surface is nearly uniform. Our formalism includes three mechanisms for the generation of excited carriers: the Drude process, the surface-assisted generation of hot-electrons in the sp-band, and the excitation of interband d-holes. Our computations show that the hot-carrier generation originating from these mechanisms reflects the internal structure of hot spots in nanocrystals with complex shapes. The injection of energetic carriers and increased surface phototemperature are driving forces for photocatalytic and photo-growth processes on the surface of plasmonic nanostructures. Therefore, developing a consistent microscopic theory of such processes is necessary for designing efficient nanoantennas for photocatalytic applications.