Ultrasensitive Detection of Polycyclic Aromatic Hydrocarbons (PAHs) in Water Using Three-Dimensional SERS Substrate Based on Porous Material and pH 13 Gold Nanoparticles

Sensitivity is crucially important for surface-enhanced Raman spectroscopy (SERS) application to detect trace-level polycyclic aromatic hydrocarbons (PAHs) in the seawater. In this study, a high sensitivity three-dimensional (3-D) SERS substrate composed with syringe filter, glycidyl methacrylate-ethylene dimethacrylate (GMA-EDMA) porous material and optimal parameters (57 nm, pH 13) gold nanoparticles (AuNPs) was developed for the detection of PAHs in water. The enhancement effect and repeatability of this 3-D substrate were also explored. The Raman intensity of pyrene using 3-D SERS substrate is about 8 times higher than that of substrate only using pH 13 gold colloid solution and about 12 times higher than that of substrate using natural AuNPs and GMA-EDMA porous material, which means both the pH 13 AuNPs and the GMA-EDMA porous material are important factors for the sensitivity of this 3-D SERS substrate. Good repeatability of this optimal 3-D substrate was obtained. The relative standard deviation (RSD) is less than 8.66% on the same substrate and less than 3.69% on other different substrates. Four kinds of PAHs, i.e., phenanthrene, pyrene, benzo(a)pyrene, benzo(k)fluoranthene and their mixture, were detected at the different concentrations. Their limits of detection (LODs) are 8.3x10(-10) (phenanthrene), 2.1x10(-10) (pyrene), 3.8x10(-10) (benzo(a)pyrene) and 1.7x10(-10)mol L-1 (benzo (k)fluoranthene), respectively. In addition, these four PAHs were also detected by fluorescence spectroscopy to evaluate the sensitivity of SERS technology using this optimal 3-D SERS substrate. The results showed that the sensitivity of SERS based on the 3-D SERS substrate even using the portable Raman system was closed to that of fluorescence spectroscopy. Therefore, the SERS technology using this optimal 3-D substrate is expected to be an in-situ method for the detection of environmental PAHs.