Pressure-induced chemical enhancement in Raman scattering from graphene–Rhodamine 6G–graphene sandwich structures

In this study, we introduce a new method to enhance the Raman signals of a graphene–Rhodamine 6G (R6G)–graphene sandwich structure by creating a magnet-induced static pressure to maximize the chemical contact between the R6G molecules and graphene. The increase in pressure in the graphene–R6G–graphene sandwich geometry plays a crucial role in enhancing the Raman signal by approximately up to 30 times in comparison to that acquired from a R6G/graphene layered film. In addition, the pressure-induced enhancement effects in the planar vibrational motion of the R6G (1200–1500 cm−1) were more recognizable than those in the low-wavenumber region and were almost comparable to the surface-induced enhancement effects in the Raman scattering signals observed from the spontaneously formed ‘folded’ pseudo-π-bonded graphene–R6G–graphene sandwich structures. The enhancement effect diminished with an increase in the number of graphene layers (on the bottom side), which was clearly discernible when graphene/glass sandwiched structures placed on top of exfoliated multilayered graphene coated with R6G were imaged.