Giant Vesicles with Anchored Tiny Gold Nanowires: Fabrication and Surface-Enhanced Raman Scattering

Sensitivity and reproducibility are two major concerns to improve the performance and extend the range of practical applications of surface-enhanced Raman scattering (SERS). A theoretical report reveals that hot spots formed by gold nanoparticles with a tip-to-tip configuration would generate the maximum electric field enhancement because of the lightning rod effect. In our present study, we constructed a giant vesicle consisting of anchored tiny gold nanowires to provide a high density of sharp tip-to-tip nanogaps for SERS application. The tiny gold nanowires were directly grown and anchored onto the surfaces of polystyrene (PS) microspheres by a seed-mediated method. Then, the removal of PS microspheres by tetrahydrofuran led to the formation of the giant gold vesicles with hierarchical cage structures, providing the sharp tips and high density of hot spots for improving SERS performance. Compared with the nonwire structure (island and inhibited nanoparticle), giant gold vesicles with tiny wires showed a higher SERS enhancement factor (9.90 × 10⁷) and quantitative SERS analysis in the range of 10^-4 to 10^-7 M. In addition, the large-scale giant gold vesicle array on the silica substrate resulted in a high reproducibility of SERS signals with the variation of intensities less than 7.6%.