Resonant field enhancements from metal nanoparticle arrays

Theoretical and semiempirical studies of two-dimensional (2D) metal nanoparticle arrays under periodic boundary conditions yield quantitative estimates of their electromagnetic (EM) field factors, revealing a critical relationship between particle size and interparticle spacing. A new theory based on the RLC circuit analogy has been developed to produce analytical values for EM field enhancements within the arrays. Numerical and analytical calculations suggest that the average EM enhancements for Raman scattering ((G) over bar) can approach 2 x 10(11) for Ag nanodisks (5 x 10(10) for Au) and 2 x 10(9) for Ag nanosphere arrays (5 x 10(8) for Au). Radiative losses related to retardation or damping effects are less critical to the EM field enhancements from periodic arrays compared to that from other nanostructured metal substrates. These findings suggest a straightforward approach for engineering nanostructured arrays with direct application toward surf ace-enhanced Raman scattering (SERS).