Negatively charged 2D black phosphorus for highly efficient covalent functionalization

Two dimensional (2D) black phosphorus (BP) has attracted great attention in recent years, but its applications have been hindered by poor stability and difficulty in functionalization. In this work, we demonstrate that negatively charged BP fabricated via lithium ion intercalation exhibits much higher reactivity to diazonium modification than commonly studied neutral BP. The diazonium functionalized BP nanosheets show high surface coverage and remain stable under ambient conditions for more than 200 days. Such covalently modified BP nanosheets also provide a versatile platform for further chemical decoration toward a wide range of functionalities. As a proof of concept, we demonstrate that the highly stable and covalently functionalized 2D BP materials can be applied in nonlinear optics and catalysis. Together with the high versatility and scale-up potential, the surface functionalization method based on negatively charged 2D BP could significantly expand the applications of BP in a wide range of fields.