Surface-Enhanced Raman Scattering on Gold Nanohole Arrays in Symmetrical Dielectric Environments Exhibiting Electric Field Extension

摘要

The electromagnetic enhancement in surface enhanced Raman scattering (SERS) caused by localized surface plasmon resonance is a near-field effect, often limiting the practicality of SERS in many applications. However, no attempts have been made to investigate field extension through symmetrical refractive index modulation in a SERS-based system. Here, we report the development and characterization of refractive index-matched SERS substrates supporting electric field extension to realize what is termed "long-range SERS" (LR-SERS). Finite-difference time-domain simulations were employed to tune the plasmonic responses and investigate electric field distributions of gold nanohole arrays (NHAs) as a function of the dielectric environment and geometric parameters. SERS substrates supporting long-range behavior were compared against "conventional" substrates without long-range behavior. SERS intensities from rhodamine 6G (R6G) aqueous solutions of 2.0 X 10(8) and 1.5 X 10(2) counts s(-1)mW(-1) were produced by the LR-SERS and conventional substrates, respectively, on the gold surface. Moreover, a signal response of 9.0 x 10(1) counts s-imlArl was produced by LR-SERS substrates with a 10 nm separation between the R6G solution and NHA, while no signal was observed from the conventional substrate. As a proof of principle study, the results demonstrate the potential to use LR-SERS substrates in applications where the target analyte is located further from the SERS-active surface.