Large-area Co(OH)2 nanoflower array films decorated with Ag nanoparticles as sensitive SERS substrates

Abstract

Large-area three-dimensional (3D) well-ordered Co(OH)₂ nanoflower array films decorated with Ag nanoparticles (Ag NPs) with a novel structure were designed as sensitive SERS substrates for trace detection of pesticides. Co(OH)₂ nanoflowers were electrodeposited on the surface of molded polyacrylonitrile (PAN) films with ordered nanopillar arrays and then Ag NPs were sputtered onto of the surface of each Co(OH)₂ nanoflower. The SERS performance of the as-prepared films can be optimized by tuning the Ag-sputtering duration and the morphology of the Co(OH)₂ nanoflower arrays. Owing to the formation of high-density SERS “hotspots” created in the nanogaps between the adjacent Ag NPs located on the same and neighbouring Co(OH)₂ nanosheets, the optimized substrates show SERS activity for probe molecules. As a result, 10⁻¹¹ M rhodamine 6G and 10⁻⁹ M 4-aminothiophenol can be SERS recognized, respectively. To verify their practical application, the optimized SERS substrates were employed for trace detection of thiram (a type of pesticide), and 10⁻⁹ M thiram can be recognized, showing great potential in pesticide detection.