Hummers' method-assisted liquid-phase exfoliation enables the fabrication of few-layer borophene from bulk boron

The fabrication of few-layer borophene (BP) from bulk boron (b-B) is of great importance and still a scientific challenge due to the complex structure and crystallinity of b-B. Herein, we propose a novel technique to prepare a few-layer BP on a large scale with a large lateral size in a well-controlled manner. For this, we employed the Hummers' method-assisted liquid-phase exfoliation. In the first step, the chemical exfoliation of the b-B as a precursor was performed by the modified Hummers' method. After chemical exfoliation, mechanical delamination was employed by using an immersion sonicator. Finally, BP sheets were collected with dimensions ranging from several hundred nanometers to a few micrometers and an average thickness of 4.2 nm. We envision that the proposed low-cost, flexible, and large-scale production method will provide unique advantages for the application of few-layer BP in the realization of high-performance electronics, optoelectronics, flexible devices, sensing systems, energy conversion, and storage devices.