Soluble, Exfoliated Hexagonal Boron Nitride Nanosheets

Hexagonal boron nitride (h-BN), the isoelectric analogue of graphite, was functionalized using lipophilic and hydrophilic amine molecules. The functionalization induced the exfoliation of the layered structure of h-BN, resulting in few-layered and monolayered nanosheets soluble in common organic solvents and/or water. The soluble h-BN nanosheets were characterized using various solution-phase and solid-state techniques. For example, the optical extinction coefficients of the h-BN nanosheets in homogeneous dispersions were estimated to be much lower than those of graphene sheets, confirming their low-colored nature. Solution-phase NMR spectroscopy supported the mechanism that the amino groups of the functional molecules complex to the electron-deficient boron atoms on the h-BN nanosheet surfaces in terms of Lewis acid−base interactions. Results from other microscopic and spectroscopic characterizations of these functionalized two-dimensional nanomaterials are also presented, and the implications of the reported versatile and effective functionalization strategy are discussed.