Ultrathin Hexagonal PbO Nanosheets Induced by Laser Ablation in Water for Chemically Trapping Surface-Enhanced Raman Spectroscopy Chips and Detection of Trace Gaseous H2S

Lead oxide (PbO) nanosheets are of significance in the design of functional devices. However, facile, green, and fast fabrication of ultrathin and homogenous PbO nanosheets with a chemically clean surface is still desirable. Herein, a simple and chemically clean route is developed for fabricating such nanosheets via laser ablation of a lead target in water for a short time and then ambient aging. The obtained PbO nanosheets are (002)-oriented with microsize in planar dimension and ∼15 nm in thickness. They are mostly hexagonal in shape. Experimental observations of the morphological evolution have revealed that the formation of such PbO nanosheets can be attributed to two processes: (i) laser ablation-induced formation of ultrafine Pb and PbO nanoparticles (NPs) and (ii) PbO NP aggregation and their oriented connection growth. Importantly, a composite surface-enhanced Raman spectroscopy (SERS) chip is designed and fabricated by covering a PbO nanosheet monolayer on a Au NP film. Such a composite SERS chip can be used for the fast and trace detection of gaseous H2S in which the PbO nanosheets can effectively chemically trap H2S molecules, demonstrating a new application of these PbO nanosheets. The response of this chip to H2S can be detected within 10 s, and the detection limit is below 1 ppb. Also, this PbO nanosheet-based chip is reusable by heating after use. This study not only deepens the understanding of the NP-based formation mechanism of nanosheets but also provides the renewable SERS chips for the highly efficient detection of trace gaseous H2S.