Protecting black phosphorus with selectively adsorbed graphene quantum dot layers

Black phosphorus (BP) is an exciting material that possesses excellent electronic properties, such as high mobility, and thickness-dependent, easily tunable band gap, making it a promising candidate for applications in optoelectronics, energy storage and nano-photonics. However, the instability of mechanically exfoliated BP thin films under oxygen and humidity conditions is still a bottleneck in its practical applications. Herein, we choose a facile way to effectively protect BP by selectively adsorbing graphene quantum dots (GQDs) on its surface as a protective layer. This strategy can prevent the degradation of the thin BP layer in the presence of oxygen and humidity. We systematically investigated the impact of GQDs absorption on BP surface via atomic force microscopy, Raman spectroscopy, transmission electron microscopy and electrical measurements. Our results show that GQDs could effectively protects the BP surface from exposure to atmospheric oxidants, resulting in significantly improved stability along with enhanced mobility and on/off ratio of corresponding field-effect transistors (FETs). Importantly, the electrical properties of optimized FETs could be retained for over 24 h even under heating at 100 ℃ in ambient conditions. This work offers a facile approach to efficiently prevent BP and other air-sensitive materials from environmental oxidants for their practical applications.