Atomically thin Ag nanosheets for single-molecule SERS detection of BPF

Despite the exceptional properties and advanced functionalities of two-dimensional (2D) nanomaterials, the fabrication of freestanding, atomically thin metal nanosheets poses a considerable challenge due to the inherently omnidirectional nature of typical metallic bonds. Herein, we introduce a novel ligand-confinement strategy to prepare the atomically thin Ag nanosheets. The ultrathin 2D structure is stabilized by manipulating the coordinate ligands to construct confined spaces and lower the inherent high surface energy, thus avoiding agglomeration. The atomically thin 2D structure exhibits a distinct quantum confinement effect, inducing energy level splitting conducive to uniform hot spots on planar Ag surfaces and extraordinary surface-enhanced Raman spectroscopy (SERS) properties. Leveraging the synergistic effects of electromagnetic and chemical enhancement, our approach achieves single-molecule-level SERS detection at concentrations as low as 10⁻¹⁷ M of bisphenol F (BPF). The atomically thin noble metal-based SERS technology possesses superb merits of ultra-high sensitivity, extraordinary uniformity, and reproducibility.