Recent progress in fabrication of anisotropic nanostructures for surface-enhanced Raman spectroscopy.

Surface-enhanced Raman scattering (SERS) is recognized as one of the most sensitive spectroscopic tools offering highly sensitive chemical and biological detection. The fact that particle plasmon allows direct coupling of light to resonant electron plasmon oscillation has spurred tremendous efforts in the design and fabrication of highly SERS-active substrates in nanostructured films and metallic nanoparticles. Theoretical studies have shown that symmetry breaking allows for more complex plasmon propagation, potentially leading to more intense electromagnetic field generation along the structure and in gaps formed between these materials. Anisotropic metallic nanostructures have all of the characteristics that make them excellent candidates as SERS substrates. Thus, SERS is expected from anisotropic materials. This review focuses on the progress and advances in the design and fabrication of anisotropic nanostructures for SERS, with an emphasis on future challenges.