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

Abstract

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.

Novel n–i CeO2/a-Al2O3 Heterostructure Electrolyte Derived from the Insulator a-Al2O3 for Fuel Cells

“…24−26 Meanwhile, the absence of a new peak in the Raman spectra means that no chemical bonds are formed. 27,28 The intensity of the 465 cm −1 peak becomes weaker with an increase in the a-Al 2 O 3 content, as a reflection of alumina really existing in heterostructure samples. Hence, the Raman result confirms the chemical stability of the CeO 2 /a-Al 2 O 3 heterostructure composites.…”

“…Figure S1b shows the XRD patterns of the composite before and after the test; the results show that amorphous Al 2 O 3 tested at the operating temperature (400–550 °C) of the cells did not undergo a crystallization transition of γ-Al 2 O 3 because of the high crystallization transition temperature (750–800 °C) Figure b shows the Raman spectra with a 514 nm excitation laser of pure CeO 2 and various ratios of CeO 2 /a-Al 2 O 3 composites; the pronounced characteristic peak at 465 cm –1 is attributed to the symmetrical vibration-stretching F 2g mode of Ce–O–Ce. − Meanwhile, the absence of a new peak in the Raman spectra means that no chemical bonds are formed. , The intensity of the 465 cm –1 peak becomes weaker with an increase in the a-Al 2 O 3 content, as a reflection of alumina really existing in heterostructure samples. Hence, the Raman result confirms the chemical stability of the CeO 2 /a-Al 2 O 3 heterostructure composites.…”

Graphene Nanoribbon Gap Waveguides for Dispersionless and Low-Loss Propagation with Deep-Subwavelength Confinement

“…The value of the reflection phase shift is negative for m = 0; thus, Equation (6) can still hold, which means that the fundamental mode can be guided. Significantly, the reflection phase shift can be employed to evaluate the boundary effect not only in GNRGW, but also in some other types of plasmonic waveguides with finite widths, such as the metal nanowire on a metal substrate [44,45] and the metal nanowire on graphene [46,47]. To analyze GSPPs guided by the GNRGW, the Helmholtz equation is solved using the method of separation of variables, and their dispersion equation is deduced as (see Supplementary Materials B)…”

Strong Coupling of Plasmonic Nanorods with a MoSe2 Monolayer in the Near-Infrared Shortwave Region

“…In the quantum mechanical mode, the coupling strength, which is determined as g = N μ e · E ∝ μ e N / V , (where N is the effective exciton number coherently contributing to the interaction with the cavity, μ e is exciton transition dipole moment, E is the vacuum field amplitude) is inversely proportional to the mode volume V . , To achieve a high coupling strength, a highly effective approach is to reduce the mode volume, V eff , for plasmonic nanocavities. Light can be confined to an ultrasmall volume, which promotes the light–matter interaction. − Recently, strong coupling has been achieved in different metallic nanostructures with small effective volumes, such as single hollow nanoparticles, gold nanobipyramids, nanorods, nanoprisms, nanocubes, and even the gaps between nanoparticles and mirrors. − However, the strong coupling regime has always been investigated in the optical spectrum, and research on coherent states in the near-infrared shortwave region (NIR-I) is limited. This is because tuning the plasmonic resonance peak to the NIR-I is difficult, while maintaining a small mode volume.…”