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

Abstract

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 °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.