Three-dimensional superhydrophobic surface-enhanced Raman spectroscopy substrate for sensitive detection of pollutants in real environments

Despite much effort to improve the design of surface-enhanced Raman spectroscopy (SERS) substrates, it remains a great challenge to develop a general substrate that can separate, enrich, and detect diverse targets in real environments. We demonstrate a novel three-dimensional (3D) superhydrophobic SERS substrate to detect polycyclic aromatic hydrocarbon (PAH) pollutants. The unique 3D superhydrophobic SERS substrate was produced by a galvanic replacement reaction between nickel foam and auric chloride acid, followed by modification with long-chain alkyl mercaptan molecules. Owing to the 3D micro-nanoscale hierarchical structure and long-chain alkyl mercaptan molecules, the as-prepared 3D Au nanoparticles/nickel foam (Au NPs/nickel foam) exhibited superhydrophobic properties, which may be used to detect PAHs due to the hydrophobic interactions. In SERS spectra with this substrate, pyrene could be detected at concentrations as low as 10−8 M. The enhancement factor of the 3D SERS substrate for pyrene detection was calculated to be about 1.2 × 104. This 3D hydrophobic SERS substrate enables the ultrasensitive detection of various analytes with poor affinity for adsorption on conventional SERS substrates, making SERS a potential and more widely practical analytical technique. Moreover, such 3D hydrophobic SERS substrates could be applied as an oil–water separation system for the separation, enrichment and sensitive detection of pollutants in real environments.