Large-Scale synthesis of crystalline phosphorus nanosheets with superior air-water stability and flame-retardancy ability

Black phosphorus (BP) has spurred exploration of two-dimensional phosphorus allotropes but its inferior stability in air and water as well as complex exfoliation routes hinder large-scale application. Herein, crystalline phosphorus nanosheets (cryst-P NSs) are synthesized by a solvothermal technique using amorphous red phosphorus and amine as the raw materials. The one-pot production weight of the cryst-P NSs with an average lateral size of 200 nm and thickness of 15 nm can be increased to 100 g with a high yield over 95 %. The underlying mechanism of the amine promoted structure and transformation from amorphous to crystalline is systemically investigated, and an active amine screening model is proposed from the macroscopic perspective. The cryst-P NSs exhibit superior stability in different environments, including ambient conditions, humid air, aqueous solution, and light irradiation due to their weak surface hydrophilicity. Compared to emerging efficient flame retardant BP NSs, the cryst-P NSs possess better fire retarding properties. The amine-driven structural transformation paves the way for low-cost and large-scale production of nanomaterials, and the stable phosphorus allotrope is expected to have application in many and broader fields.