SiO2 is situated at 103.3 eV, which is ascribed to the OASiAO bond [21]. Apparently, in the case of SiO2@rGO (Fig. 3d), besides the binding energy assigned to the OASiAO bond, a new binding energy of silicon for SiO2@rGO appears at 102.2 eV, indicating the existence of a covalent bond (SiAOAC). Such chemical environ- ment for Si2p is definitely different from that for the pristine SiO2. For the synthesis of GPTMS-rGO, the functional groups, such as hydroxyls, could bond with carbon atoms from rGO via dehydra- tion reaction. A schematic is proposed and is shown in the inset of Fig. 3d. Additionally, the spectrum of the N1s spectra of APES-SiO2 (Fig. 3e) indicates the existence of ANH2 bonds (399.5 eV). Note- worthily, a new binding energy of N1s for SiO2@rGO located at
401.6 eV is observed in Fig. 3f, which is attributable to the NH+
OOC ionic bonds. A corresponding schematic is also present in the inset of Fig. 3f. All of these findings suggested that SiO2@rGO has been successfully synthesized by the combination of chemical reduction and the electrostatic attraction between carboxyl (ACOO ) on the GPTMS-GO and amino (ANH+) on the APES-SiO .