Au Nanocucumbers with Interior Nanogap for Multiple Laser Wavelength-Compatible Surface-Enhanced Raman Scattering

It is critical to design and synthesize plasmonic nanostructures that can generate very strong and quantitative surface-enhanced Raman scattering (SERS) signals that could be amplified by multiple laser wavelengths to realize the full potential of SERS nanoprobes. Here, we report the synthesis of Au-nanobridged nanogap cucumbers (Au-NNCs) from DNA-modified Au nanorods and comparison of their SERS signals with three different Raman dyes with our recently reported Au-nanobridged nanogap spheres (Au-NNSs). Although the Au-NNSs generate highly stable and reliable signals, these spherical nanogap structures with a smooth surface produce strong SERS signals (SERS enhancement factor at ∼10⁸) only with 633 nm excitation laser. The Au-NNCs with a bumpy surface generated up to ∼3-, ∼23-, and ∼130-fold higher SERS signals with 514, 633, and 785 nm excitation laser wavelengths, respectively, compared to the Au-NNSs.