Two-Dimensional Lead Monoxide: Facile Liquid Phase Exfoliation, Excellent Photoresponse Performance, and Theoretical Investigation

Here, we report fabrication of two-dimensional (2D) lead monoxide (PbO) nanosheets by facile liquid phase exfoliation. The as-prepared 2D PbO nanosheets have circle and cut-circle shapes with a lateral dimension range of 200-400 nm and a thickness range of 10-15 nm and exhibit dominant beta-crystals with a robust chemical stability under ambient conditions. As a building block, the 2D PbO has been developed for photoelectrochemical (PEC)-type photodetectors that exhibited excellent as well as tunable photoresponse behaviors under illuminations of ultraviolet-visible lights. The first-principles density functional theory calculations further show that the band gap (E-g) of 2D PbO can be tuned by external electric field with a significant Stark effect. Moreover, differing from most transition metal dichalcogenide (TMD) materials, the 2D PbO structure, whose lowest empty states are dominated by the lead p orbitals, is exposed, which means that orbital modification of 2D PbO is accessible. Consequently, the E-g of PbO can be decreased in the KOH electrolyte by a possible Pb OH interaction, thus, broadening its absorption range for photodetection applications. In addition, the photoresponse behavior of 2D PbO-based photodetectors has long-term stability. This work may open the way for development of 2D PbO nanomaterials with promising applications.