Polarization-Dependent Surface Enhanced Raman Scattering from Silver 1D Nanoparticle Arrays

Arrays of linear, one-dimensional (1D) silver nanoparticle rows have been synthesized that demonstrate strong surface enhanced Raman scattering (SERS) that is dependent on the polarization of the incident electromagnetic radiation. Ordered arrays of 1D rows of spherical silver nanoparticles were fabricated on highly oriented pyrolytic graphite (HOPG) by physical vapor deposition (PVD) at 400 °C. Scanning electron microscopy confirmed the formation of arrays of highly parallel rows of nanoparticles. The rows are typically hundreds of microns long with particle gaps less than 10 nm and 10-1000 nm spacing between adjacent 1D rows. The polarization dependence of the SERS was characterized using thiophenol as a Raman probe molecule that was adsorbed as a monolayer on the silver nanoparticle surfaces. When incident light is polarized along the axis of the nanoparticle rows, the intensity of the Raman-scattered light was ≈20 times stronger than Raman scattered light when the incident radiation was polarized perpendicular to the axis of the nanoparticle rows. This polarization selectivity is in good agreement with our calculations that explore the electromagnetic response of the interacting nanoparticles with an incident light field.