Preparation of Thiol Modified Fe₃O₄@Ag Magnetic SERS Probe for PAHs Detection and Identification

In situ detection and identification of PAHs, a group of well-known persistent organic pollutants, presents a great challenge to environmental researchers. This work developed a novel substrate based on thiol-functionalized Fe₃O₄@Ag core–shell magnetic nanoparticles for surface enhanced Raman scattering (SERS) sensing of PAHs. The surface morphology, structure, and magnetic properties of the substrate were characterized using multiple complementary techniques including transmission electron microscopy, energy-dispersive X-ray spectroscopy, vibrating sample magnetometry analysis, and extended X-ray absorption fine structure spectroscopy. The high saturation magnetization at 48.35 emu g^–1 enabled the complete and rapid separation of the substrate from the PAH solution. Benzene, naphthalene, anthracene, phenanthrene, fluorene, pyrene, perylene, and BaP were chosen as probe molecules. Qualitative and quantitative determination of PAHs was achieved using a portable Raman spectrometer. The SERS sensitivity was positively correlated with the hydrophobic nature of PAHs. The SERS response exhibited a linear dependence on the PAHs concentration between 1 to 50 mg/L, and the detection limit in the order 10^–5 to 10^–7 M was obtained. The SERS platform with magnetic substrate provides a new way for in situ PAH monitoring.