Single-walled carbon nanotube networks decorated with silver nanoparticles: a novel graded SERS substrate

We report on investigations of surface-enhanced Raman scattering (SERS) from a nanostructure of singlewalled carbon nanotubes (SWNTs) decorated with Ag nanoparticles. Ag is electrochemically deposited on a two-dimensional network of SWNTs, forming nanoparticles of graded density and size away from the contact electrode. The morphology of the Ag nanoparticles on the SWNTs is correlated to their optical properties and the degree of enhancement of the Raman spectra. A strong correlation between localized surface plasmon resonance wavelength, particle size and density, laser excitation wavelength, and SWNT Raman scattering intensity is found. This knowledge is used to increase the degree of enhancement by adjusting the nanoparticle size and density. These results demonstrate a tunable approach to controlling the enhancement of Raman scattering from SWNTs, enabling high sensitivity SERS measurements. Furthermore, the nanostructure produced has considerable potential as a generic SERS substrate for the study of a variety of target molecules in air and under solution.