Tracking single atoms in a liquid environment

TL;DR

This paper introduces a novel liquid cell platform for transmission electron microscopy that enables real-time imaging of single metal atoms in liquids, revealing their dynamic behavior and environmental effects at atomic resolution.

Contribution

The authors develop a double liquid cell based on 2D heterostructures for in situ TEM imaging of single atoms in liquids, overcoming vacuum limitations and enabling atomic-scale studies.

Findings

Single platinum atoms exhibit different resting sites in liquid compared to vacuum.

Atomic hopping behavior is significantly influenced by the liquid environment.

In situ liquid imaging reveals chemical activity not observable under vacuum conditions.

Abstract

The chemical behaviour of single metal atoms largely depends on the local coordination environment, including interactions with the substrate and with the surrounding gas or liquid. However, the key instrumentation for studying such systems at the atomic scale generally requires high vacuum conditions, limiting the degree to which the aforementioned environmental parameters can be investigated. Here we develop a new platform for transmission electron microscopy investigation of single metal atoms in liquids and study the dynamic behaviour of individual platinum atoms on the surface of a single layer MoS2 crystal in water. To achieve the record single atom resolution, we introduce a double liquid cell based on a 2D material heterostructure, which allows us to submerge an atomically thin membrane with liquid on both sides while maintaining the total specimen thickness of only ~ 70 nm. By comparison with an identical specimen imaged under high vacuum conditions, we reveal drastic differences in the single atom resting sites and atomic hopping behaviour, demonstrating that in situ imaging conditions are essential to gain complete understanding of the chemical activity of individual atoms. These findings pave the way for in situ liquid imaging of chemical processes with single atom precision.