Solvothermal-assisted liquid-phase exfoliation of large size and high quality black phosphorus

Black phosphorus (BP), especially for BP nanosheets, with unique layered structure among two dimensional (2D) materials has attracted much attention due to its outstanding physical properties, such as ultra-high mobility, in-plane anisotropic properties. However, the small horizontal-size of reported BP limits its applications in the integrated circuit or some functional devices. In this work, a solvothermal-assisted liquid-phase exfoliation technique is firstly employed for preparing large size and high-quality BP nanosheets. In the high-polar acetonitrile solvent, solvothermal treatment weakens the Van der Waals forces of block BP. Together with the subsequently ultrasonic processing, effective exfoliation of large size and high-quality BP nanosheets are realized. The TEM, AFM and Raman results indicate that the prepared BP nanosheets are high quality with an average thickness of about 2 nm, and the horizontal-size is up to 10 μm. This facile and effective method for exfoliated BP nanosheets provides a promising strategy for the exfoliation of other 2D materials.