Graphene-plasmonic hybrid platforms have attracted an enormous amount of interest in surface-enhanced Raman scattering (SERS); however, the mechanism of employing graphene is still ambiguous, so clarification about the complex interaction among molecules, graphene, and plasmon processes is urgently needed. We report that the number of graphene layers controlled the plasmon-driven, surface-catalyzed reaction that converts para-aminothiophenol (PATP)-to-p,p′-dimercaptoazobenzene (DMAB) on chemically inert, graphene-coated, silver bowtie nanoantenna arrays. The catalytic reaction was monitored by SERS, which revealed that the catalytic reaction occurred on the chemical inertness monolayer graphene (1G)-coated silver nanostructures. The introduction of 1G enhances the plasmon-driven surface-catalyzed reaction of the conversion of PATP-to-p,p′-DMAB. The chemical reaction is suppressed by bilayer graphene. In the process of the catalytic reaction, the electron transfer from the PATP molecule to 1G-coated silver nanostructures. Subsequently, the transferred electrons on the graphene recombine with the hot-hole produced by the localized surface plasmon resonance of silver nanostructures. Then, a couple of PATP molecules lost electrons are catalyzed into the p,p′-DMAB molecule on the graphene surface. The experimental results were further supported by the finite-difference time-domain method and quantum chemical calculations.

Low-cost, stabilized and ultrasensitive three-dimensional (3D) hierarchical surface-enhanced Raman scattering substrates (“sunflower-like” nanoarrays decorated with Ag nanoparticles, denoted as SLNAs-Ag) have been obtained by fabricating binary colloidal crystals and then decorating with Ag nanoparticles. In order to provide a larger density of hot spots within the laser-illumination area, the silica sphere arrays were chosen as the island-type platform for the polystyrene (PS) nanosphere deposition, and the distances between the PS nanospheres were tuned by etching for different durations. Compared with conventional 2D planar systems, the as-fabricated 3D SLNAs-Ag exhibited extremely high SERS sensitivity ascribed to the larger SERS active regions. Quantitative detection of molecules with an extremely low incident laser power was achieved on the “sunflower-like” nanoarrays in which the PS nanospheres were etched for 5 minutes and decorated with Ag nanoparticles, and the corresponding analytical enhancement factor is calculated to be 2 × 10¹⁴ with the concentration of rhodamine 6G down to 10⁻¹⁵ M. Based on the achieved SERS substrates, we have further demonstrated the highly sensitive detection of molecules such as melamine for food safety inspection.

β-NaYF₄ UCMPs were synthesized on a large-scale and the UCMPs fluorescence inks-based screen-printing patterns applied for anti-counterfeit applications.