Wettability of Supported Monolayer Hexagonal Boron Nitride in Air

Hexagonal boron nitride (h-BN), a wide band gap monolayer crystal with structure similar to graphene, is optically transparent with exceptionally high thermal and chemical stability, and should be ideal to serve as an atomically thin coating. However, limited by the challenges in fabricating h-BN of high quality in large area, the wetting performance of h-BN has seldom been studied. Here, it is shown that the water contact angle of freshly grown h-BN film is nearly independent of the underlying materials as well as the h-BN layer number, but increases gradually to a saturated stable value in air due to the spontaneous adsorption of airborne hydrocarbon. First-principles calculations and molecular interaction modeling confirm that a monolayer h-BN coating does efficiently tune the interaction of a water molecule with different substrates to a converging level. The saturated wettability of h-BN coating is robust against variation of several factors, facilitating its practical applications.