Probing nanoscale spatial distribution of plasmonically excited hot carriers

Bin Ren,Sen Yan,Sheng-Chao Huang,Yu-Han He,Jin-Feng Zhu,Shu Hu,Matthew M Sartin,Xiang Wang,Cha-Wei Li,Qing-Qing Zhao

doi:10.1038/s41467-020-18016-4

Abstract

Surface plasmons (SPs) of metals enable the tight focusing and strong absorption of light to realize an efficient utilization of photons at nanoscale. In particular, the SP-generated hot carriers have emerged as a promising way to efficiently drive photochemical and photoelectric processes under moderate conditions. In situ measuring of the transport process and spatial distribution of hot carriers in real space is crucial to efficiently capture the hot carriers. Here, we use electrochemical tip-enhanced Raman spectroscopy (EC-TERS) to in situ monitor an SP-driven decarboxylation and resolve the spatial distribution of hot carriers with a nanometer spatial resolution. The transport distance of about 20 nm for the reactive hot carriers is obtained from the TERS imaging result. The hot carriers with a higher energy have a shorter transport distance. These conclusions can be guides for the design and arrangement of reactants and devices to efficiently make use of plasmonic hot carriers.

Highlights

Surface plasmons (SPs) of metals enable the tight focusing and strong absorption of light to realize an efficient utilization of photons at nanoscale
We chose the decarboxylation reaction, a key step in Kolbe electrolysis reaction[26], as the model reaction for the Electrochemical tip-enhanced Raman spectroscopy (ECTERS) study (Fig. 1a). 4-mercaptobenzoic acid (4-MBA) molecules, which have no absorption at the wavelength of the excitation laser, were used as reactants
We obtained the transport distance for the reactive hot holes in real space, which is comparable to the mean free path of the hot carriers in Au

Summary

Introduction

Surface plasmons (SPs) of metals enable the tight focusing and strong absorption of light to realize an efficient utilization of photons at nanoscale. The nonradiative decay of SPs via Landau damping creates hot carriers with an energy significantly higher than that can be achieved by the thermal excitation, even when the system is kept at ambient temperature[1,2,3,4,5,6,7] These hot carriers can be transferred to semiconductors and molecules on the surface, driving the chemical processes. We use EC-TERS to in situ monitor a SP-driven decarboxylation reaction at the nanoscale and resolve the spatial distribution of reactive hot carriers beneath the plasmonic tip by fully exerting its unique advantages. We demonstrate in experiment that the hot holes with a higher energy have a shorter transport distance These conclusions can be guides for the spatial arrangement of the reactant molecules and devices to efficiently make use of the hot carriers in the design of the SP-based catalysts

Methods

Results

Conclusion