Liquid exfoliation of solvent-stabilized few-layer black phosphorus for applications beyond electronics

TLDR

Few‑layer black phosphorus is a promising two‑dimensional material for electronics, but its instability hampers synthesis and processing. The study demonstrates large‑scale production of high‑quality few‑layer black phosphorus nanosheets via liquid‑phase exfoliation in N‑cyclohexyl‑2‑pyrrolidone. Liquid‑phase exfoliation in CHP yields nanosheets whose dimensions can be controlled and spectroscopically estimated, while computational studies show edge‑specific water‑induced degradation. The CHP‑exfoliated nanosheets are highly stable without water and show promise for optical switches, gas sensors, and composite reinforcement.

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.