Controllable 3D Hot-Junctions of Silver Nanoparticles Stabilized by Amphiphilic Tri-block Copolymer/Graphene Oxide Hybrid Surfactants for Use as Surface-Enhanced Raman Scattering Substrates

We herein report the manufacture of surface-enhanced Raman scattering (SERS) substrates in which silver nanoparticles (AgNPs) are well dispersed in an organic/inorganic nanohybrid surfactant consisting of an amphiphilic triblock copolymer and graphene oxide (GO). Transmission electron microscopy measurements confirmed that the resulting AgNPs had a narrow size distribution of ∼15 nm. These AgNPs were adsorbed on both sides of the GO nanosheets, forming controllable nanodispersions of the AgNPs/copolymer/GO hybrid. A facile method for fabricating the desired nanohybrid SERS films was therefore developed by immobilizing spherical AgNPs with a narrow size distribution on both sides of the 3–5 nm-thick GO nanosheets, which afforded 1–5 nm interparticle distances between the AgNPs. Furthermore, the hybrid substrate films formed three-dimensional (3D) hot-junctions and exhibited an SERS enhancement factor (EF) of 1.2 × 105 toward adenine molecules from DNA, which served as a model biomolecular target.