The inherent structure of two-dimensional, 2D, materials encompasses a regime where surface and edge chemistry affect properties. Phosphorene, the 2D form of black phosphorus, is a crystalline semi-conductor with intriguing optoelectronic properties, but it is not stable in ambient conditions. In a study published in ACS Applied Materials and Interfaces, researchers in the Warren lab studied the role of oxygen and water in the oxidation mechanism of 2D black phosphorus and explored the potential to control the surface and edge chemistry of the material by oxidation.
Phosphorene was exposed to pure oxygen, pure water, or a mixture of water and oxygen and then illuminated. The resulting oxide compositions were characterized and spatially observed through microscopy. Pure oxygen led to a relatively uniform oxide on the basal surface of the 2D black phosphorus, while pure water resulted in preferential oxidation at defect sites, such as edges, steps, and grain boundaries. Mixtures of water and oxygen resulted in accelerated oxidation of the surface and edges of the material.
With these observations, the opportunity to selectively oxidize the basal surface or edge states of phosphorene is feasible. Control of the surface and edge chemistry of 2D black phosphorus opens avenues to new surface reaction chemistries, such as covalent functionalization or passivation of defect sites."