Figure 3.

(a) Schematic of a graphene and nanohole system. Four different areas of the substrate are shown. (b) Raman mapping of 1621 cm⁻¹ methylene blue peak at the graphene edge on the nanohole array overlaying an optical micrograph of the sample. Graphene is not visible without interference effect. The dotted line shows the graphene border, as confirmed by SEM. (c) Raman spectra of methylene blue on four different areas of the substrate: glass, graphene-covered glass, Au nanoholes, and graphene-covered Au nanoholes. (d) Raman spectra for glass and graphene-glass areas, normalized to maximum intensity. The D band, G band and 2D band of graphene are indicated by *. All Raman measurements are performed with a 647 nm laser with a power of ~ 1mW/μm² on sample, 10 second integration time, and one accumulation.