Defects-assisted piezoelectric response in liquid exfoliated MoS2 nanosheets.

MoS2 is an intrinsic piezoelectric material which offers applications such as energy harvesting, sensors, actuators, flexible electronics, energy storage and more. Surprisingly, there are not any suitable, yet economical methods that can produce quality nanosheets of MoS2 in large quantities, hence limiting the possibility of commercialisation of its applications. Here, we demonstrate controlled synthesis of highly crystalline MoS2 nanosheets via liquid phase exfoliation of bulk MoS2, following which we report piezoelectric response from the exfoliated nanosheets. The method of piezo force microscopy (PFM) was employed to explore the piezo response in mono, bi, tri and multilayers of MoS2 nanosheets. The effective piezoelectric coefficient of MoS2 varies from 9.6 pm/V to 25.14 pm/V. We attribute piezoelectric response in MoS2 nanosheets to the defects formed in it during the synthesis procedure. The presence of defects is confirmed by X-ray photoelectron spectroscopy (XPS).