Portable surface-enhanced raman scattering sensor for the rapid detection of polycyclic aromatic hydrocarbons in coastal seawater

To rapidly detect polycyclic aromatic hydrocarbons (PAHs) in coastal seawater, a portable surface-enhanced Raman scattering (SERS) sensor was designed and assembled. A large number of halide ions are present in seawater, and they easily combine with gold nanoparticles, which results in a significant SERS enhancement effect for PAHs. Therefore, a mixture of a gold colloid solution and NaCl solution that forms a large number of highly sensitive SERS-active clusters was used in this study. The extinction intensity of the gold colloid solution at 785 nm-that is, the SERS excitation wavelength-was greatly increased by the addition of Cl-. The SERS sensor was applied in five different coastal environments, and six or seven types of PAHs were detected without further sample processing. The seawater samples were also analyzed using a gas chromatography-flame ionization detector (GC-FID) for comparison and confirmation of the results. Ten to 13 types of PAHs were detected by GC-FID after dehydration, purification, and concentration under nitrogen, and naphthalene was not detected because of its volatility. The SERS sensor was proven to be a suitable alarm sensor for the in-situ detection of PAHs in coastal seawater and is proposed for use as a real-time qualitative and quantitative PAH monitoring sensor in the near future based on its promising improvement in sensitivity.