Synthesis of superhydrophobic polydopamine-Ag microbowl/nanoparticle array substrates for highly sensitive, durable and reproducible surface-enhanced Raman scattering detection

Surface-enhanced Raman scattering (SERS) sensor allows for fingerprinting and label-free molecular detection with a high sensitivity, but the simple fabrication of SERS active substrates with a well-control over the SERS performance, e.g. an ultra-high sensitivity, superior reproducibility and long-term stability remain a great challenge. Here, we introduce an easy strategy for synthesizing polydopamine-Ag microbowl/nanoparticle array (PDA-Ag MNA) substrates with a tunable superhydrophobic surface, applicable for ultra-highly sensitive SERS detection. First, the periodically dented PDA films are prepared by polymerizing dopamine onto 2D polystyrene colloidal crystals formed at the liquid/air interface, and followed with an in-situ reduction of Ag ions to Ag nanoparticles after removing polystyrene. The surface morphology, i.e. microbowl/nanoparticle structure, is well-controlled, therefore, allowing that the SERS activity of the substrate is under control. Inspired by the superhydrophobic hierarchical surface of the rose petals, this analogous MNA surface is subsequently endowed to be superhydrophobic. This way, the SERS detection of ultra-dilute solute (10−14 M) can be achieved by concentrating analytes within a localized region. Moreover, this substrate also shows a superior reproducibility in result and durability in use. This strategy exhibits a realistic paradigm for further improving the sensitivity of the SERS technique.