Liquid exfoliation of solvent-stabilised black phosphorus: applications beyond electronics

TL;DR

This paper presents a method to produce stable, high-quality black phosphorus nanosheets via liquid exfoliation in CHP, enabling diverse applications beyond electronics, with insights into stability and degradation mechanisms.

Contribution

It introduces a scalable liquid exfoliation process for black phosphorus nanosheets and develops spectroscopic metrics for size and thickness estimation.

Findings

High-quality nanosheets can be produced in large quantities.

Nanosheets are stable unless water is introduced.

Degradation occurs at edges reacting with water, forming phosphine and phosphorous acid.

Abstract

Few layer black phosphorus is a new two-dimensional material which is of great interest for applications, mainly in electronics. However, its lack of stability severely limits our ability to synthesise and process this material. Here we demonstrate that high-quality, few-layer black phosphorus nanosheets can be produced in large quantities by liquid phase exfoliation in the solvent N-cyclohexyl-2-pyrrolidone (CHP). We can control nanosheet dimensions and have developed metrics to estimate both nanosheet size and thickness spectroscopically. When exfoliated in CHP, the nanosheets are remarkably stable unless water is intentionally introduced. Computational studies show the degradation to occur by reaction with water molecules only at the nanosheet edge, leading to the removal of phosphorus atoms and the formation of phosphine and phosphorous acid. We demonstrate that liquid exfoliated black phosphorus nanosheets are potentially useful in a range of applications from optical switches to gas sensors to fillers for composite reinforcement.