Simultaneous preconcentration and ultrasensitive on-site SERS detection of polycyclic aromatic hydrocarbons in seawater using hexanethiol-modified silver decorated graphene nanomaterials

Synthesis of high-quality metal nanoparticle (NP) decorated graphene (GN) with uniform and controllable nanostructures has attracted considerable attention due to its excellent electronic structure and optical properties. Herein, we develop a facile and robust process for tailoring hexanethiol (SH)-modified Ag NP-decorated graphene nanomaterials (Ag/GN-SH) by coupling in situ reduction and the covalent assembly technique. The as-prepared Ag/GN-SH combines adequate Raman "hot spots" among the high-density Ag NPs and the excellent adsorption performance of GN, making it an excellent surface-enhanced Raman scattering (SERS) substrate for highly selective and sensitive detection of PAHs. Moreover, the Ag/GN-SH can be used as a solid-phase extraction (SPE) adsorbent for qualitative and quantitative detection of PAHs in seawater from their discriminant SERS peaks. The Ag/GN-SH-based SPE-SERS is effective over a wide range of concentrations (0.1 nM to 0.5 mM) for PAHs, with tens of pM detection limits [signal to noise ratio (S/N) = 3], and the detection concentration deviation is less than 15% between the SPE-SERS and GC-MS. This study not only offers a new method for on-site removal of PAHs but also provides a strategy for simultaneous multiplexed detection of PAHs.