Covalent functionalization of black phosphorus nanosheets via insensitive glycidyl azide polymer with durable stability

Covalent functionalization of black phosphorus nanosheets (PNs) exhibit relatively stability, but one unpaired electron still retains in the phosphorus atom, rendering unsaturated coordination state and hampering the passivation effect. Azide functionalization achieves the five-coordinate bonding of phosphorus atoms, making PNs completely passivated. But a molecule with an azide group is extremely dangerous owing to explosive and corrosive nature. Herein, insensitive glycidyl azide polymer, GAP, was the first used for covalent azide functionalization of PNs to generate GAP-PN of P=N bond with the best stability. The structure of GAP-PN was comprehensively confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), the atomic force microscopy (AFM), Raman spectra, solid-state ³¹P nuclear magnetic resonance spectroscopy (³¹P NMR), x-ray photoelectron spectroscopy (XPS) and the elemental analysis. The average statistical size and the thickness of GAP-PN is 2.46 ± 1.51um and10.4 nm.The stabilization mechanism was explored via XPS, and the mechanism was attributed to the chemical modification of the surface of PNs with P=N bond formation, which inhibits the formation of PₓOy. The stability properties of GAP-PN were evaluated by XPS and the UV/Vis spectroscopic. The experimental results show that the degradation ratio of GAP-PN decreased from 54.9 to 8.8% of PNs after 60 days. In addition, compared with PNs, the peak temperature corresponding to exothermic phase(TP) of GAP-PN decrease by 44.6 °C and heat released during the decomposition for GAP-PN is up to is 3154.9 J/g, which is 6.09 times higher than that of PNs. This work provides a novel strategy for the stability study of PNs, which is supposed to possess significant potential in the nanocomposite energetic materials applications field.