A superhydrophobic–superoleophilic plasmonic membrane for combined oil/water separation and highly-sensitive SERS detection of low concentrations of analytes in oil/water mixtures

Abstract

Pollutants in the real environment are mostly oil/water mixtures, therefore the oil phase and the water phase may lead to mutual interference when SERS detection is performed. The separation of pollutants from oil/water mixtures and the independent detection of the oil phase and the water phase have become emerging issues in real applications. However, it is still a challenge to detect highly diluted molecules in aqueous solution since the molecules in aqueous solution are usually far from the plasmonic sensitive surface due to the highly dispersed molecules in solution. Here, a superhydrophobic–superoleophilic plasmonic membrane for integrated oil/water separation and enhanced SERS detection is prepared. The as-fabricated plasmonic membrane can not only separate analytes in the water phase from an oil/water mixture but can also enrich analytes in the water phase into a very small area on the surface of the plasmonic membrane, where the hot spots are located. Superior SERS detection sensitivity for low concentrations of R6G (10⁻¹⁴ M) in an oil/water mixture was achieved, whereas the Raman signals of R6G (10⁻⁹ M) in an oil/water mixture on a traditional Ag nanoparticle-coated silica substrate were difficultly distinguished owing to the interference of the oil phase.