Metallic nanoparticle arrays: A common substrate for both surface-enhanced raman scattering and surface-enhanced infrared absorption

12 pages, 10 figures.-- et al.Nanoshell arrays have recently been found to possess ideal properties as a substrate for combining surface enhanced raman scattering (SERS) and surface enhanced infrared absorption (SEIRA) spectroscopies, with large field enhancements at the same spatial locations on the structure. For small interparticle distances, the multipolar plasmon resonances of individual nanoshells hybridize and form red-shifted bands, a relatively narrow band in the near-infrared (NIR) originating from quadrupolar nanoshell resonances enhancing SERS, and a very broadband in the mid-infrared (MIR) arising from dipolar resonances enhancing SEIRA. The large field enhancements in the MIR and at longer wavelengths are due to the lightning-rod effect and are well described with an electrostatic model.This work is supported by the U.S. Army Research Laboratory and the U.S. Army Research Office under contract/grant no. W911NF-04-1-0203, the Robert A. Welch Foundation under grants C-1220 and C-1222, by NSF under grants EEC-0304097, CNS-0421109, ECCS-0421108, and DMR-0705384, and by the Air Force Office of Scientific Research Grant FA9550-06-1-0021. J.A. acknowledges the friendly and hospitable atmosphere at the Rice Laboratory for Nanophotonics during a one-month-stay in the summer and financial support from the ETORTEK NANOTRON project.Peer reviewe