Au nanoparticles grafted on Fe3O4 as effective SERS substrates for label-free detection of the 16 EPA priority polycyclic aromatic hydrocarbons

• SERS detection of the 16 EPA priority PAHs was conducted.
• The satellite-core structure lead to high SERS enhancement by confined hotspots.
• The approach does not require expensive instrumentation or large sample volumes.
• The effective protocol is useful for the identification of hydrophobic molecules.

Several methods and materials have been explored for the sensitive and practicable detection of polycyclic aromatic hydrocarbons (PAHs). However, it is still a challenge to develop simple and cost-effective sensing techniques for PAHs. Herein we report the synthesis and construction of Fe3O4@Au SERS substrate. This magnetic substrate was composed by Fe3O4 microspheres and Au NPs. The size, morphology, and surface composition of Fe3O4@Au were characterized by multiple complimentary techniques including scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray powder diffraction. The spatial distributions of electro-magnetic field enhancement around Fe3O4@Au was calculated using finite difference time domain (FDTD) simulations. As a result of its remarkable sensitivity, the Fe3O4@Au-based SERS assay has been applied to detect the 16 EPA priority PAHs. The LODs achieved by our method (100–5 nM, 16.6–1.01 μg L−1) make it promising for the rapid screening of highly contaminated cases. As a proof-of-concept study, the substrate was applied in SERS sensing of PAHs in river matrix. The 16 PAHs could be differentiated based upon their characteristic SERS peaks. Most importantly, the detection was successfully conducted using a portable Raman spectrometer, which could be used for on-site monitoring of PAHs.

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