Gap structure effects on surface-enhanced Raman scattering intensities for gold gapped rods.
Gapped rods provide a unique platform for elucidating structure/function relationships, both for single-molecule electrochemical techniques and for surface-enhanced Raman scattering (SERS). This paper attempts to elucidate the dependence of SERS intensities on gap topography and gap distance for gold gapped rods with segment lengths varying over a wide range (40-2000 nm). Significantly, we have determined that rough gaps lead to a smaller SERS enhancement than smooth gaps for these structures even though the rough gaps have a larger total surface area. Both theory and experiment show periodic variation of SERS intensity with segment length as determined by odd-symmetry plasmon multipoles. Excitation of even-symmetry modes is dipole forbidden (for polarization along the rod axis), but this selection rule can be relaxed by roughness or, for smooth gaps, by near-field coupling between the rod segments.
Li
Shuzhou
S
Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
Pedano
María L
ML
Chang
Shih-Hui
SH
Mirkin
Chad A
CA
Schatz
George C
GC
D003198:Computer Simulation; D006046:Gold / Q000737:chemistry*; D008956:Models, Chemical; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D012542:Scattering, Radiation; D020349:Surface Plasmon Resonance / Q000379:methods*
D006046:Gold