5:45 PM - 6:00 PM
[15p-B6-15] Protection of Ag particles in SERS substrates by bilayer graphene
Keywords:graphene, Surface enhanced Raman scattering, silver
Surface enhanced Raman scattering (SERS) technique is a novel method to highly sense molecular and lattice vibrations. Although nanostructured silver (Ag) surface provides the most intense SER signals, Ag is not chemically stable compared to gold which is another representative element for SERS. Graphene has very high chemical and thermal stability. We previously demonstrated that a graphene coated Ag nanoparticles show SERS with tolerance for strong acids (hydrogen chloride). Here, we report that bilayer graphene (BLG) can serve high thermal stability to nanostructured Ag surface for SERS.
A 10 nm thick Ag thin film was deposited on a quartz substrate by vacuum evaporation. Graphene, which consists of mainly single layer and partially bilayer, was grown by atmospheric pressure chemical vapor deposition on a Cu foil, and was transferred onto the Ag/quartz substrate with a polymethyl methacrylate (PMMA) supporting layer. The PMMA was removed by immersing in an organic mixture (acetone, methyl isobutyl ketone, and isopropyl alcohol) and heating in air at 350 ºC. To examine thermal durability of the graphene coated Ag on quartz (graphene/Ag/quartz), the sample was heated at 800 ºC for 10 min in vacuum (<2 Pa). Subsequently, rhodamine 6G (R6G) was loaded by dropping and drying. Raman spectra were obtained using a 532 nm laser after each step of sample preparation (removal of PMMA, heating at 800 ºC, and R6G deposition).
Enhancements of Raman peaks of graphene (D, G, and G’ peaks) were only observed in the BLG domain but not in single layer (SLG) region, and D peak was appeared in the entire graphene after the heating. These indicate that the Ag underneath BLG was remained, while the other Ag was evaporated by the heating through defects in the top layer. The BLG/Ag/quartz shows very large Raman peaks of graphene and the observed enhancement factor of G’ peak is ~ 43. The R6G/BLG/Ag shows strong Raman peaks of R6G implying that the BLG/Ag/quartz has SERS ability after high temperature heating (800 ºC) in vacuum.
A 10 nm thick Ag thin film was deposited on a quartz substrate by vacuum evaporation. Graphene, which consists of mainly single layer and partially bilayer, was grown by atmospheric pressure chemical vapor deposition on a Cu foil, and was transferred onto the Ag/quartz substrate with a polymethyl methacrylate (PMMA) supporting layer. The PMMA was removed by immersing in an organic mixture (acetone, methyl isobutyl ketone, and isopropyl alcohol) and heating in air at 350 ºC. To examine thermal durability of the graphene coated Ag on quartz (graphene/Ag/quartz), the sample was heated at 800 ºC for 10 min in vacuum (<2 Pa). Subsequently, rhodamine 6G (R6G) was loaded by dropping and drying. Raman spectra were obtained using a 532 nm laser after each step of sample preparation (removal of PMMA, heating at 800 ºC, and R6G deposition).
Enhancements of Raman peaks of graphene (D, G, and G’ peaks) were only observed in the BLG domain but not in single layer (SLG) region, and D peak was appeared in the entire graphene after the heating. These indicate that the Ag underneath BLG was remained, while the other Ag was evaporated by the heating through defects in the top layer. The BLG/Ag/quartz shows very large Raman peaks of graphene and the observed enhancement factor of G’ peak is ~ 43. The R6G/BLG/Ag shows strong Raman peaks of R6G implying that the BLG/Ag/quartz has SERS ability after high temperature heating (800 ºC) in vacuum.