Surface-Enhanced Raman Scattering (SERS) Substrate Based on Large-Area Well-Defined Gold Nanoparticle Arrays with High SERS Uniformity and Stability

A fabrication process that combines an ultrathin alumina membrane (UTAM) surface nanopatterning technique and a physical vapor deposition method has been designed for realizing well-defined Au nanoparticle arrays for sensitive, uniform, and stable surface-enhanced Raman scattering (SERS)-active substrates. High Raman signals are obtained by adjusting the structural parameters of the metallic nanoparticles when rhodamine 6G (R6G) and 4-mercaptopyridine (4-MP) are used as the probe molecules. The corresponding estimated enhancement factors (EFs) are 6.5x10(6) (R6G) and 6.8x10(5) (4-MP), respectively. The simulated distributions of the electric field of SERS substrates coincide with the experimental results. Raman measurements at randomly selected spots on a substrate show a standard EF deviation of about 5%, which indicates a desirable SERS uniformity. An advantageous feature of our SERS substrate is its long-term stability of enhanced Raman signals. Raman measurements on a substrate after one year show almost the same magnitude of Raman signal (10(6) for R6G and 10(5) for 4-MP) as that of the original measurement. Such substrates with good SERS sensitivity, uniformity, and stability should have high potential for SERS-related applications.