Ultratough Hydrogen-Bond-Bridged Phosphorene Films

Abstract

The rapid development of flexible electronic devices, especially based on 2D materials, has triggered the demand for high-strength materials. Mono- or few-layer phosphorene with excellent electronic properties has attracted extensive attention. However, phosphorene is affected by its low Young's modulus when applied to flexible electronic devices. Here, a strategy via ion intercalation to significantly improve the mechanical properties of black phosphorus to generate hydrogen-bond-bridged phosphorene films with Young's modulus as high as 316 GPa is reported. This value is several times larger than the theoretical values of 166 GPa in the zigzag direction, 44 GPa in the armchair direction, and the averaged Young's modulus among all directions of 94 GPa. The impact of intercalation on mechanical properties is also explored. Experimental nanoindentation results obtained by atomic force microscopy indicate that the relationship between the ratio of intercalated ions to phosphorus atoms and the corresponding Young's modulus satisfies the formula $E=e^{a{e}^{\frac{-{\left[\ln \right(x)+b]}^2}{c}}}(0<x\le 1.80)$ . Furthermore, a flexible NO₂ gas sensor device based on this ultratough material presents excellent performance, even after 10 000 bending cycles. The results provide new insight into the potential for practical applications of black phosphorus devices.

Keywords: flexible NO 2 sensors; hydrogen bonds; mechanical properties; phosphorene.