Abstract
Hybrids based on graphene decorated with plasmonic gold (Au) nanostructures are being investigated as possible materials combination to add to graphene functionalities of tunable plasmon resonance and enhanced absorption at selected wavelength in the visible-near-infrared region of the spectrum. Here, we report a solution drop-casting approach for fabricating stable hybrids based on chemical vapor deposition (CVD) graphene and Au nanorods, which are able to activate effective charge transfer from graphene. We demonstrate that CVD graphene functionalization by benzyl thiol (BZT) provides the linker to strong anchoring, via S-Au bonds, Au nanorods to graphene. Optical measurements by spectroscopic ellipsometry give evidence of the introduction of plasmon resonances at 1.85 and 2.25 eV in the Au nanorods/BZT/graphene hybrids, which enable surface enhanced Raman scattering (SERS) detection. Furthermore, an effective electron transfer from graphene to Au nanorods, resulting in an enhancement of p-type doping of graphene with a consequent decrease of its sheet resistance, is probed by Raman spectroscopy and corroborated by electrical measurements.
Highlights
The synergic combination of the extraordinary mechanical, thermal, and electronic properties of graphene (G) with the peculiar functionalities of metal [1], semiconductor [2], and oxide [3] nanostructures is an important field of research with promising technological perspectives
We demonstrate that chemical vapor deposition (CVD) graphene functionalization by benzyl thiol (BZT) provides the linker to strong anchoring, via S-Au bonds, Au nanorods to graphene
We propose benzyl thiol (BZT) as linker for stabilizing the anchoring of colloidal Au nanorods (AuNRs) on the surface of graphene obtained by chemical vapor deposition (CVD)
Summary
The synergic combination of the extraordinary mechanical, thermal, and electronic properties of graphene (G) with the peculiar functionalities of metal [1], semiconductor [2], and oxide [3] nanostructures is an important field of research with promising technological perspectives. While largely used spherical Au nanoparticles have localized surface plasmon resonance (SPR) mainly in the visible range and redshifting with the increase of radius from approximately 2.5 eV down to 2.0 eV [8], Au nanorods (AuNRs) enable more interesting functions due to their anisotropic shape, which introduces splitting of the plasmon resonance in the longitudinal (L-SPR, excitation along the major axis of the AuNRs) and transverse (T-SPR, excitation along the minor radial axis of the AuNRs) modes, with the former tunable in the near-infrared range and the latter in the visible range [9] Such peculiar tunability of AuNRs plasmonic properties in combination with graphene has demonstrated great potential for the fabrication of high sensitive and flexible surface enhanced Raman scattering (SERS) sensors [10, 11] and high-performance NIR photodetectors [9]. SERS signal provides insights into the interaction of both graphene and AuNRs with BZT molecules
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