Since Novoselov and Geim et al. in 2004 reported a simple approachto synthesize graphene films by mechanical exfoliation,71graphene72–78 has attracted great interest from scientists andbecome the most popular 2D material for SERS detectionbecause of its excellent extraordinary physical strength andextreme adsorbed species. Graphene has unique advantageswith a much wider area compared to nanotubes, and its superior adsorption capacity offers more opportunities to capturemolecules, even ions, during detection. For groundbreakingexperiments regarding the 2D material graphene, Novoselovand Geim were awarded the Nobel Prize in physics in 2010. Inthe same year, Jung et al. found that iodine anions (I3 and I5)adsorbed on single layer graphene presented strong Ramanscattering, and the Raman signals of an intercalated bromine(Br2) layer showed the same characteristics.79 As shown inFig. 4A, the increase of graphene layers induced the significantdecrease of Raman signal intensities of iodine anions (I3 and I5),and the intensities were 30 times stronger on one layer of graphenethan bulk graphite. A similar phenomenon illustrated in Fig. 4B wasdemonstrated in which the single layer intercalated bromine (Br2)Raman intensity in bulk graphite was 6 times bigger than in fourlayers of graphene.