Graphene-coupled nanowire hybrid plasmonic gap mode–driven catalytic reaction revealed by surface-enhanced Raman scattering

The single-layer graphene (SLG)-coupled nanowire (NW) hybrid plasmonic gap mode (PGM)-driven molecular catalytic reaction was investigated experimentally and theoretically. First, an SLG-coupled NW was constructed, then the surface-enhanced Raman scattering (SERS) effect of graphene in the hybrid plasmonic gap was studied via the normal and oblique incidence of excitation light. The SERS peaks of the D and G of graphene are more intensely enhanced by oblique incidence than by normal incidence. Furthermore, the catalytic reaction of the dimerization of the 4-nitrobenzenethiol molecule to p,p′-dimercaptoazobenzene molecule driven by PGM was carried out by SERS. It was demonstrated that the efficiency of the PGM-driven catalytic reaction is much higher for oblique incidence than that for normal incidence. The mechanism of the PGM-driven catalytic reaction was studied by a finite-difference time-domain numerical simulation. When the PGM is excited by oblique incidence with θ = 30°, the coupling between the NW and SLG/SiO2 substrate increases to the maximum value. This is clearly evidenced by the excitation of a vertical bonding dipolar plasmon mode under the dipole approximation. The theoretical and experimental results were consistent with each other. This research may open up a pathway toward controlling PGM-driven catalytic reactions through polarization changes in excitation laser incidence on single anisotropic nanostructures.