At the same time, the layer-to-layer distance of the graphene-Ag composite films has also been changed from 1.20 to 1.61 nm, indicating that some of the oxygen functional groups have been reduced. As shown, the graphene-Ag composite films have a shorter distance from 1.20 to 1.34 nm than the graphene films from 1.56 to 1.61 nm, suggesting that AgNO3 is beneficial to the reduction process and the suitable amount Selleckchem BAY 63-2521 of AgNO3 is 10 mg. Figure 6 XRD patterns of graphite, graphene oxide, and graphene-Ag composite films. (a) Graphene oxide films, (b to d)

graphene films (reduced by ascorbic acid), (e to i) graphene-Ag composite films (the amount of AgNO3 was from 2 to 300 mg in each film), and (j) graphite. The Raman scattering signals were measured on the graphite powder (Figure 7 (a)), graphene oxide films (Figure 7 (b)), the graphene films (Figure 7 (c to e)), and the graphene-Ag composite films (Figure 7 (f to j)). The Raman ARS-1620 in vivo spectra exhibit two main characteristic peaks, the D band (approximately 1,345 cm−1) and G band (approximately 1,590 cm−1). The G

band represents the plane vibrations with E 2g symmetry and is mainly sensitive to the configuration of sp 2 sites, while the D band is related to the breathing mode of κ-point phonon of A 1g symmetry. PX-478 mouse As the graphite was oxidized into graphene oxide, the G band is broadened and the D band increases substantially, indicating the decrease in size of the in-plane sp 2 sites, possibly because of the extensive oxidation and ultrasonic exfoliation [41]. When graphene oxide is reduced by ascorbic acid

for 5 h, the increase of the I D/I G intensity ratio of graphene is observed compared to that of Staurosporine the graphene oxide. Finally, when AgNO3 was used, the increase of D band also occurred. This change suggests an increase in the average size of the sp 2 sites upon reduction of graphene oxide, which indicates that the reduction reaction has taken place and agrees well with the Raman spectrum of the graphene oxide reduced by hydrazine as reported by Stankovich et al. [42]. Figure 7 Raman spectra of graphite, graphene oxide, and graphene-Ag composite films. (a) Graphite, (b) graphene oxide film, (c to e) graphene films (reduced by ascorbic acid), and (f to j) graphene-Ag composite films (the amount of AgNO3 was from 2 to 300 mg in each film). FTIR is used to characterize the functional groups in the films shown in Figure 8. When the pristine graphite powder (sample j) is oxidized, many functional groups can be introduced in the graphene oxide films (sample a), which have a peak at approximately 3,410 cm−1 arising from the -OH stretching vibrations and peak at approximately 1,730 cm−1 of carboxyl C=O, approximately 1,620 cm−1 of C-C groups, approximately 1,400 cm−1 of O-H, and 1,100 cm−1 of alkoxy C-O.