Superhydrophobic SERS Substrates Based on Silver-Coated Reduced Graphene Oxide Gratings Prepared by Two-Beam Laser Interference

Reported here is the fabrication of reduced graphene oxide (RGO) grating structures by two-beam laser interference (TBLI) for the development of highly efficient SERS substrates via simple physical vapor deposition (PVD) coating of silver. TBLI has been utilized to make hierarchical RGO grating structures with microscale gratings and nanoscale folders through a laser treatment induced ablation and photoreduction process. The hierarchical structures contribute to the formation of plasmonic structures after silver coating, giving rise to the formation of plenty of SERS "hot spots", while the RGO substrate would provide chemical enhancement of Raman signal through interaction with analytes molecules. The significantly increased roughness with respect to the hierarchical structures in combination with the removal of hydrophilic oxygen-containing groups endow the resultant substrates with unique superhydrophobicity, which leads to the enrichment of analytes and further lowers the detection limit. The synergistic effects make the silver coated RGO gratings a highly efficient SERS substrate; in the detection of Rhodamine B, our SERS substrates showed high SERS enhancement and good reproducibility, a detection limit of 10(-10) M has been achieved.