# Light Entrapment by Plasmonic Chiral Lock for Enhancement of 2D Flakes Catalytic Activity

## TL;DR

This paper shows how chiral gold nanoparticles can boost the catalytic activity of 2D MoS2 for ammonia production through plasmonic effects.

## Contribution

A novel chiral plasmonic structure is introduced to enhance the catalytic performance of 2D materials via controlled light entrapment.

## Key findings

- Matching chirality of gold helicoids increases ammonia yield by two times compared to mismatched or nonchiral structures.
- Chiral plasmonic coupling enhances the electric field in the MoS2 layer, improving catalytic efficiency.
- Numerical simulations and SERS confirm the role of chirality in plasmon energy concentration.

## Abstract

Plasmon-based triggering leads to an effective increase
of material
catalytic activity in a number of relevant photoelectrochemical transformations,
including nitrogen reduction for the production of ammonia. The efficiency
of the plasmon assistance can be significantly increased through the
rational design of hybrid photoelectrodes, e.g., by placing a redox-active
material at plasmonic hot spots that may arise between two coupled
nanostructures. In this work, we describe the creation and utilization
of chiral plasmon-active hybrid structures (based on the so-called
gold helicoids) coupled with redox-active 2H-MoS2. The
chiral plasmon-active gold nanoparticles (with the same or opposite
chirality) were spatially separated by thin two-dimensional (2D) flakes
to reach mutual plasmon coupling between them. Using numerical simulations
and SERS measurements, the dependence of the local enhancement of
the electric field (EF) inside the created plasmon-active diastereomer
consisting of Au helicoid–2D MoS2–Au helicoid
“sandwich structure”, on the mutual chirality of the
nanoparticles is demonstrated. It is found that the plasmon energy
is more efficiently “concentrated” in the MoS2 space using the “chiral trap” of light energy (i.e.,
chiral plasmonic lock), even in the case where the chiral handedness
of Au nanoparticles is matching. The created hybrid structures were
subsequently used for nitrogen reduction and ammonia production proceeding
on the MoS2 surface. A clear dependence of the catalytic
activity of MoS2 on the matching or mismatching of Au helicoid
chiralities (and related local value of EF) is observed. In particular,
a two-time increase in the ammonia yield is obtained in the case of
matching chirality, compared to that in the case of mismatched configuration
or the control experiments performed with nonchiral Au nanocubes.
Hence, the utilization of chiral plasmonic nanoparticles and their
dimers (or multimers) provides an additional opportunity for even
more effective photosensibilization of redox-active materials.