Single gold-nanoparticle-enhanced Raman scattering of individual single-walled carbon nanotubes via atomic force microscope manipulation

Investigating the electric field distribution around individual metallic nanoparticles is of significant importance for the understanding of the electromagnetic (EM) mechanism of surface-enhanced Raman scattering (SERS). We report single gold-nanoparticle-enhanced Raman scattering of individual single-walled carbon nanotubes (SWNTs) by atomic force microscope (AFM) manipulation. The distance between the gold nanoparticle (GNP) and the SWNT can be controlled by pushing the GNP with an AFM tip. The Raman signals increase when a single GNP is moved close to an individual SWNT, and the corresponding polarization dependence to the incident laser excitation at each GNP/SWNT distance is studied. The agreement of the experimental results with the theoretical model described in this paper suggests a rational modification of the EM enhancement model of SERS for one-dimensional molecules, like nanotubes.