Black phosphorus is an allotrope of phosphorus consisting of multiple layers with two-dimensional structures. Black phosphorus is the least reactive form of phosphorus. Black phosphorus has two forms:
- alpha-black phosphorus: Alpha black phosphorus is formed when red phosphorus is heated in a sealed tube at 803K. It has opaque monoclinic or rhombohedral crystals.
- beta-black phosphorus: β-Black phosphorus is prepared by heating white phosphorus at 473 K under high pressure. It does not burn in the air up to 673 K.