Biomimetic synthesis of hierarchical 3D Ag butterfly wing scale arrays/graphene composites as ultrasensitive SERS substrates for efficient trace chemical detection

This paper reports a simple biomimetic synthesis of hierarchical three-dimensional (3D) Ag butterfly wing scale arrays/graphene composites via a synchronous reduction process. The original chitin-based scale arrays provide a new bioscaffold for decorating with Ag NPs and graphene in different dimensions to construct a 3D SERS substrate. The sizes, interparticle gaps, and the aggregation state of the Ag nanoparticles deposited on the butterfly wing scales can be well controlled by tuning the experimental parameters. The special structural features of 3D Ag butterfly wing scale arrays with redundant Ag nanoparticles make a significant contribution to SERS enhancement. Moreover, 3D Ag butterfly wing scale arrays coated with a moderate amount of graphene display a higher SERS activity. The SERS measurement results show that the optimized 3D Ag butterfly wing scale arrays/graphene composites exhibit the highest enhancement efficiency and high SERS sensitivity to crystal violet (CV) and 4-mercaptobenzoic acid (MBA) molecules. In addition, a low concentration of 10(-9) M for CV and 10(-8) M for MBA could be detected using a portable Raman instrument. And it gives good reproducibility across the entire area with relative standard deviations (RSD) less than 15%. The substrates still perform a good long-term stability on SERS intensity after 6 months. Additionally, the novel substrates can be applied to detect trace analytes, which show great potential as an effective SERS platform for rapid on-site chemical and biological sensing.