Xing, C; Liu, L; Fan, D; Peng, Z; Zhang, H
Owing to the fascinating properties of graphene, the first reported two-dimensional (2D) elemental nano-unit, many other 2D elemental inorganic materials have recently been investigated. 2D pnictogens, including black phosphorus (BP), arsenic (As), antimony (Sb) and bismuth (Bi), have aroused attention especially in academic research. Their intriguing 2D flat features have endowed them with extraordinary chemical and physical properties. However, during exploration of their preparation methodology as well as potential applications, 2D pnictogens also have revealed such drawbacks as low stability in air, low dispersion stability in solvents or polymer matrices, low biocompatibility in living body and toxicity in water resources. Recently, to address these issues, covalent functionalization of 2D pnictogens, especially BP, has been of great importance owing to its controllability, adjustability and diversity. The unique structures and active lone pairs of electrons of each atom in 2D pnictogens are prerequisite conditions for their possible chemical functionalization in view of the quantum confinement effect in the 2D scales. A variety of precise surface chemical modifications of 2D pnictogens, in particular for BP, are systemically introduced. The corresponding biomedical, energy storage and conversion, and optics applications are also presented. We also outline the future prospect of 2D pnictogens and challenges that still need to be considered and overcome. © 2019 Elsevier B.V.