Full text loading...
(a) Schematic and optical image of the GFET device. The dashed line indicates the raster scan direction, while back gate voltage, Vbg, is scanned from 50 V to −50 V. Raman signals of methylene blue (MB) are obtained throughout the scanning process. (b) The resistance of graphene at various gate voltages before/after coating MB molecules. The scan direction is indicated by arrows.
(a) Raman spectra of MB molecules on graphene at two gate voltages, 50 V and −50 V. A Raman spectrum of MB on SiO2 surface (no graphene) is included as a reference. Enhancement from graphene is evident. (b) Intensities of the 1621 cm−1 Raman peak of MB at various gate voltages. Error bar of one standard deviation is included in the plot. The laser excitation is ∼0.2 mW/μm2 and 20 s integration. †: peak from Si. *: G-band of graphene.
(a) Raman spectra of hole-doped, electron-doped, and normal graphene. Insets are stack plots to show the shifts. The laser excitation is 514 nm at ∼2 mW/μm2 and 1 s integration. (b) Raman intensity of MB molecules on the hole-doped, normal and electron-doped graphene with 647 nm excitation. The spectra are normalized according to the 520 cm−1 Si Raman peak (labeled by †) among different substrates. G-band from graphene is labeled by *.
Plot of the normalized SERS enhancement at 1621 cm−1 of MB as a function of the change in electron density in the graphene with respect to normal graphene. The enhancement is normalized to the undoped graphene value. The line serves as a visual guide.
Article metrics loading...