Smart Synthetic and Surface-Engineering Approaches to Functionalize 2D Black Phosphorus for Real-Setting Applications

Phosphorene or 2D black phosphorus (2D bP) has attracted increasing attention within material scientists in the last decade due to its electronic and photophysical properties as a pristine material. Furthermore, the high chemical reactivity of 2D bP enables the engineering of the outermost superficial layers. This tailored functionalization allows to obtain 2D bP-based systems such as heterostructures with multiple and/or nonstandard functional properties that can be straightforwardly exploited for real-setting applications. The aim of this review is to summarize the state of the art on the different strategies in the functionalization of 2D bP such as chemical reactivity with organic molecules, decoration with metal and metal-oxide nanoparticles, passivation with thin layers of metal oxides or polymers, van der Waals coupling with different inorganic 2D materials, blending into polymeric composites. The main physical and chemical properties of all the considered heterostructures and as-realized derivatives of 2D bP, with a particular focus on the increase of stability in air, are described. Finally, the functional characteristics of each system which are correlated to and involved in the development of specific real-setting applications, spanning from catalysis, to electronics and optoelectronics, to energy conversion and storage and biodiagnostics, are highlighted.