Monolayer Graphene Coupled to a Flexible Plasmonic Nanograting for Ultrasensitive Strain Monitoring.

Plasmonically coupled graphene structures have shown great promise for sensing applications. Their complex and cumbersome fabrication, however, has prohibited their widespread application and limited their use to rigid, planar surfaces. Here, a plasmonic sensor based on gold nanowire arrays on an elastomer with an added graphene monolayer is introduced. The stretchable plasmonic nanostructures not only significantly enhance the Raman signal from graphene, but can also be used by themselves as a sensor platform for 2D strain sensing. These nanowire arrays on an elastomer are fabricated by template-stripping based nanotransfer printing, which enables a simple and fast production of stable nanogratings. The ultrasmooth surfaces of such transferred structures facilitate reliable large-area transfers of graphene monolayers. The resulting coupled graphene-nanograting construct exhibits ultrahigh sensitivity to applied strain, which can be detected by shifts in the plasmonic-enhanced Raman spectrum. Furthermore, this sensor enables the detection of adsorbed molecules on nonplanar surfaces through graphene-assisted surface enhanced Raman spectroscopy (SERS). The simple fabrication of the plasmonic nanowire array platform and the graphene-coupled devices have the potential to trigger widespread SERS applications and open up new opportunities for high-sensitivity strain sensing applications.