Surface functionalization of two-dimensional crystals is an attractive path to tune their physical and chemical properties. However, synthetic protocols and experimental strategies to directly probe chemical bonding in modified surfaces are scarce. This presentation will describe our research in illustrating how molecular protocols can be employed to deliberately modify the surface of exfoliated black phosphorus (bP), to directly probe the bonds formed on its surface as well as to tune its electronic properties.<br/>The nature of the chemical bonding introduced on the bP surface using photolytically generated nitrenes is investigated using a multitude of characterization techniques including vibrational, X-ray photoelectron, solid state NMR, and UV-vis spectroscopy. To directly probe the functional groups introduced on the surface, nitrene fragments were selected such that in conjunction with vibrational spectroscopy, <sup>15</sup>N-labeling experiments, and DFT methods, diagnostic P=N vibrational modes indicative of iminophosphorane units on the nanosheet surface could be conclusively identified.<br/>By using group 13 Lewis acids to modify the bP surface we demonstrate not only a remarkable enhancement in ambient stability, but also excellent transport properties in resulting single flake devices, and significant p-doping of the bP flakes. The intrinsic programmability and discrete molecular nature of the Lewis acids offers a unique opportunity for deliberate, selective tuning of surfaces. We envision this simple, yet effective protocol could be extended to other 2D materials and will be easily incorporated in the fabrication of composite, complex devices at the manufacturing stages, providing solutions currently inexistent with traditional methods.

Black phosphorus functionalization: Applying molecular strategies to probe bonding and tune electronic function

ACS Spring Meeting 2021

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