Plasmonic coupling of silver nanospheres loaded on cobalt–iron layered double hydroxides: a robust SERS probe for 4-nitrophenol detection

Abstract

The development of surface enhanced Raman spectroscopy (SERS) substrates capable of sensing organic pollutants at low concentrations with high sensitivity has always been demanding. Herein, we developed and fabricated a robust SERS sensor based on plasmonic noble-metal silver nanospheres (Ag NSs) and semiconducting cobalt–iron layered double hydroxides (CoFe-LDHs) for the analysis of 4-nitrophenol (4-NP). A Ag-NSs/CoFe-LDHs nanocomposite was synthesized by chemical reduction, hydrothermal method, and physical mixing. The characterization of the synthesized Ag-NSs/CoFe-LDHs nanocomposite was meticulously scrutinized by various microscopic and spectroscopic techniques. The Ag-NSs/CoFe-LDHs nanocomposite shows superior SERS response for 4-NP detection with an ultra-low detection limit of 2.36 × 10⁻¹⁴ M and a high enhancement factor of 5.65 × 10¹¹. The enormous Raman signal enhancement is attributed to the synergistic action of the electromagnetic mechanism from Ag NSs and the charge transfer mechanism from CoFe-LDHs. The Ag-NSs/CoFe-LDHs SERS substrate exhibits good uniformity, high reproducibility, and long-term stability. Furthermore, the Ag-NSs/CoFe-LDHs SERS substrate shows good detection performance for actual environmental samples with a desirable recovery range from 93 to 95%. This work would open a new way for further development to fabricate SERS platforms with plasmonic action and interfacial charge transfer in metal/semiconductor nanocomposites.