Exfoliation of Stable 2D Black Phosphorus for Device Fabrication

Discovering stabilizers that protect phosphorene from oxidative degradation is critically required for dispersion processing of black phosphorus (BP). It is equally important to also find environmentally friendly, low-cost, and practical exfoliating media. Herein, we demonstrate the yield of remarkably stable phosphorene by coating with a polymer to shield the nanosheets from reaction with water and air. The polymer shell suppresses the rate of BP degradation more efficiently than previously reported systems. We present for the first time a simple kinetic model for exfoliation of BP in polyvinylpyrrolidone (PVP) ethanol solution that appears to quantitatively fit BP exfoliation data, and it illuminates mechanistic aspects of exfoliation. Exfoliated flakes consist of a high level of 51% crystalline single layers that are free from structural disorder or oxidation. A successive centrifugation and redispersion strategy is developed affording dispersions with high phophorene-to-stabilizer ratio, which is very...