Flower-like Ag-decked non-stoichiometric Bi₂O_3-/rGO hybrid nanocomposite SERS substrates for an effective detection...

In early years, SERS-active substrates were generally noble metals. However, their practical applications were limited due to their poor biocompatibility, low uniformity and high cost. Recently, the utilization of semiconductor SERS-active substrates has greatly expanded the applications of SERS in many fields. However, metal-free SERS-active substrates have a low enhancement factor (EF), which can be overcome by adjusting their oxygen deficiency or through the effective preparation of non-stoichiometric semiconducting oxide materials. This is the key strategy and may work as an efficient and simple way to achieve high sensitivity and obtain an enhancement factor (G-factor) comparable to that of noble metals. Here, we report the preparation of flower-like rGO-Bi₂O₃/Bi₂O_2.75 and rGO-Ag-Bi₂O₃/Bi₂O_2.75 hybrid thin film nanocomposites using a liquid/liquid interface method (LLI) for the first time. In addition to the synergic effect of different enhancement mechanisms, the 3-D flower-like morphology of the substrate shows more favourable properties to improve the G-factor due to the existence of more hotspots. The rGO-Ag-Bi₂O₃/Bi₂O_2.75 hybrid thin-film nanocomposites show an EF of 1.8 × 10⁹ with a detection ability of up to 1 nM towards Rhodamine 6G (R6G), which is highly toxic to humans and the aquatic environment.