Raman spectroscopy for probing covalent functionalization of single-wall carbon nanotubes bundles with gold nanoparticles

摘要

A hybrid system made of single-wall carbon nanotube bundles (average diameter of approximately 20 nm and length of several tens of nanometers) highly covered with gold nanoparticles (average diameter of 5 nm) was prepared through the functionalization of the nanotube surface with 4,4'-thiobisbenzenethiol molecules followed by the anchoring of gold nanoparticles. The decoration of single wall carbon nanotubes with gold nanoparticles was performed using two different methods, named as ex situ and in situ, which refer to the gold reduction before or during the contact with the nanotubes, respectively. Transmission electron microscopy images showed that both methods lead to a successful decoration of the single wall carbon nanotube bundles, although different density of gold nanoparticles covering the bundles was observed to depend on the reaction methods. Resonance Raman spectroscopy data were used to follow the electronic changes of the carbon nanotubes after gold nanoparticles loading and confirmed the strong interactions of the gold nanoparticles with the 4,4'-thiobisbenzenethiol molecules and the carbon nanotubes. This interaction was probed in the Raman spectrum which unveiled a surface enhancement Raman effect of the thiol molecule Raman signals, not observed before the attachment of metallic nanoparticles onto 4,4'-thiobisbenzenethiol functionalized carbon nanotubes.