Fluorinated graphene films for Ultra-High sensitivity of Surface-Enhanced Raman scattering

It is of great importance to design large-area and high-quality graphene and its derivatives for the application in surface-enhanced Raman scattering (SERS) with high sensitivity and good stability. The efficiently preparation and accurately regulation of these structures remain great challenges. Herein, fluorinated graphene (fGE) for high-performance SERS is developed by a facile fluorination on a sub-centimeter graphene. With precisely controlling the nucleation density of the graphene growth by NH3-plasma assistance, this large-area graphene (GE) was obtained on Cu foil. Then GE reacted with the derived F atoms from fluorocarbon in a tube furnace at 600 degrees C. SERS results demonstrate that the fGE films exhibit extraordinary Rhodamine 6G (R6G) molecular SERS sensitivity limit as low as 10-9 mol/L (M) by tuning the F/C ratio of the fGE in range of 0.024-0.234. The Raman intensity of probe molecules adsorbed on as-prepared fGE revealed a slight decrease to 98.2 % for R6G on fGE as long as 50 days, demonstrating good stability for fluorinated-graphene-enhanced Raman scattering (FGERS). Furthermore, theoretical calculations also indicate that the energy of a specific laser matches the gap between the lowest unoccupied molecular orbital (LUMO) of as-designed probe molecule (Rhodamine 6G, Methylene Blue) and Fermi level of fGE, which favors SERS chemical enhancement. This large-scale preparation of FGERS substrates with outstanding sensitivity opens a light way for potential SERS substances.

Automated summary

Designing large-area and high-quality graphene and its derivatives for surface-enhanced Raman scattering (SERS) is crucial for achieving high sensitivity and stability. However, the efficient preparation and regulation of such structures present significant challenges. In this study, fluorinated graphene (fGE) was developed for high-performance SERS through a simple process of fluorination. By controlling the nucleation density of graphene growth with NH3-plasma assistance, large-area graphene (GE) was obtained and then reacted with fluorocarbon to produce fGE. The resulting fGE films showed exceptional molecular SERS sensitivity for Rhodamine 6G (R6G) with a limit as low as 10-9 mol/L.