Controlled hydrophilization of black phosphorene: a reactive molecular dynamics simulation approach

Following the exceptional electrical and optical properties of black phosphorene, its wetting behavior has attracted the attention of many researchers. In the present study, reactive molecular dynamics (MD) simulations have been used to investigate the controlled wetting behavior of black phosphorene surface. In the first step, the hydrophobic behavior of the pristine black phosphorene as well as the elliptical shape of the water droplet on this surface was investigated using MD simulations which are in agreement with the recently reported experimental data. In the next step, controlled hydrophilization of black phosphorene was performed through oxidation of the pristine black phosphorene in different sizes. The simulation results showed that oxidation of the black phosphorene surface turns it into a superhydrophilic surface by increasing the number of hydrogen bonds. It was observed that, by placing water droplets on the phosphorene oxide surfaces a wide range of wettability phenomena can be created so that a wide range of contact angles can be measured. The results indicated that the placement position of water molecules on the phosphorene oxide surface leads to two different wetting patterns. Also, in agreement with the results of the energy profile of the phosphorene surface, calculations of Helmholtz free energy showed that the energy barrier in the armchair direction of the phosphorene surface is higher than that in the zigzag direction. The results could lead to new applications of phosphorene to control wettability at the nanoscale.