Hierarchical metal-dielectric-metal nanostructures as SERS sensors for sensitive detection of polycyclic aromatic hydrocarbons.

[Display omitted] • A metal-dielectric-metal system composed by thiol modified Au nanospheres-graphene oxide-Ag nanowires hierarchical nanostructures was fabricated. • The dielectric layer composed of mercaptan and GO was sandwiched by the top Au nanospheres and the bottom Ag nanowires. • PAHs were exactly absorbed by hydrophobic interaction of mercaptan and π-π stacking interaction of GO in the enhanced EM field area. • The hierarchical system was able to identify various types of PAHs in single and multi-component mixture as well as in real water environment. Due to the wide variety, inaccessible self-degradation, high mutagenicity and carcinogenicity of polycyclic aromatic hydrocarbons (PAHs), it still remains challenging to efficiently identify them, especially in real environment. Herein, we develop a bottom-up self-assembly strategy to construct a sandwich-like hierarchical metal-dielectric-metal system composed of mercaptan-modified Au nanospheres-graphene oxide (GO)-Ag nanowires as surface-enhanced Raman spectroscopy (SERS) sensors for sensitive detection of PAHs. The synergistic integration of metallic layers and the organic mercaptan and GO layer not only provides localized enhanced electromagnetic field region which is induced by the nanogap between the top Au nanospheres and the bottom Ag nanowires, but also effectively traps PAHs in the middle layer through hydrophobic interaction of mercaptan and π-π stacking interaction of GO. By rationally optimizing the SERS substrates, the lowest detection concentrations of pyrene, anthracene, phenanthrene and benzo[a]pyrene could be reached, respectively, at 10−8 M, 10−8 M, 10−8 M and 10−7 M. The hierarchical system shows excellent uniformity, reproducibility and is able to identify various types of PAHs in multi-component mixtures as well as in real water environment. This strategy can provide a general platform to identify hazardous pollutants that are hydrophobic or contain benzene rings, such as pesticides, dyes and polychlorinated biphenyls. [ABSTRACT FROM AUTHOR]