After an emulsion process, it is observed that the strong (001) diffraction peak of HGOSs is weakened, possibly because the partial oxygen-containing groups and bound moisture are consumed LEE011 chemical structure through reaction with ammonia and the following water removal process. In the meantime, the (002) diffraction peak was partially recovered, suggesting that the graphene layers rearranged
during the emulsion process. After heat treatment, the diffraction peak of GO disappears, indicating that HGOSs has successfully reduced to HGSs. Figure 2b shows FTIR spectra of GO, HGOs, and HGSs. For GO, the peak at 3,405 cm-1 can be attributed to O-H stretching vibrations of adsorbed water molecules and structural OH groups, and the peak at 1,619 cm-1 can be attributed to O-H bending vibrations. The presence of carboxyl and epoxy functional groups can also be detected at around 1,724 and 1,224 and 1,053 cm-1, respectively [17, 22]. These evidences indicate that during the oxidation process of graphite with KMnO4 in the concentrated sulfuric acid, the original extended conjugated π-orbital system of graphite were destroyed, and oxygen-containing functional groups were inserted into carbon skeleton. Therefore, it is reasonable to believe that GO nanosheets should be regarded
as ‘amphiphilic molecules’ and perform a surfactant-like function in a water/oil emulsion system . Due to the introduction of acid groups
on the edge sites and basal planes of graphene sheets, GO nanosheets are well-dispersed in alkali solution. SN-38 in vivo On the basis of the experimental results, a scheme is presented to describe the formation process of nano HGOSs self-assembled by water/oil emulsion. It includes four steps: (1) the delamination of graphite after intensive oxidation; (2) the homogeneous mixture of GO nanosheets and aqueous ammonia; (3) the formation of a water-in-oil emulsion containing GO nanosheets; (4) and the removal of water and the separation of HGOSs from olive oil. When aqueous Progesterone ammonia containing GO nanosheets is mixed with olive oil by mechanical agitation, a water-in-oil system is formed. GO nanosheets were supported by the water-in-oil interface and self-assembled around water droplets under the assistance of ammonia. With the removal of aqueous ammonia, the GO nanosheets stacked and condensed at the water-in-oil interface and finally formed a shell structure around the soft template. Figure 2 XRD patterns (a) and FTIR spectra (b) of GO, HGOs, and HGSs. After a thermal treatment in H2, these functional groups derived from the intensive oxidation were eliminated, which can be proved by the disappearance of the peaks at 1,724, 1,619, 1,224, and 1,053 cm-1 while an appearance of a new peak at 1,631 cm-1 (Figure 2b) reflecting the skeletal vibration of graphene sheets [15, 22].