Thermal gravimetric analysis (TGA, SDTA851e) was used to evaluate the weight loss ratio of the products.

The tests were conducted at a heating rate of 10°C/min from room temperature to 900°C under nitrogen. Scanning electron microscopy (SEM, HITACHI SU1510, Selleck GW3965 Chiyoda-ku, Japan) was employed to observe the surface morphology of various products, whose accelerating voltage was 1.0 kV. Transmission electron microscopy (TEM, H-800-1) was employed to observe the microstructure of various products, whose accelerating voltage was 20 kV. Results and discussion Fourier Selleckchem Barasertib transform infrared spectroscopy The FTIR spectra of f-GNPs, PAA-GNPs, siloxane-GNPs, and SiO2/GNPs hybrid material were presented in Figure  2. The peaks at 3,440 cm−1 (Figure  2a) which were attributed to stretching vibration of O-H groups could be observed clearly. The results indicated that GNPs had been functionalized successfully as designed. The peaks at 1,190 and 1,100 cm−1 (Figure  2b) were assigned to stretching vibration of C-O-C groups between GNPs and PAA, which indicated that PAA was grafted onto the surface

of GNPs successfully. As showed in Figure  3c, Ro 61-8048 cost the peaks at 1,556 and 3,300 cm−1 were attributed to bending vibration and stretching vibrating of N-H groups of amide, respectively. And the peak at 1,640 cm−1 (Figure  2c) was attributed to stretching vibration of C = O groups of amide. Exoribonuclease Meanwhile, the peaks at 1,121 and 1,045 cm−1 were attributed to stretching vibrating of Si-O and C-O groups of siloxane respectively. Also, the peak at 2,930 cm−1 was assigned to stretching vibration of C-H groups of alkyl groups. All these features confirmed that KH550 have linked with PAA-GNPs successfully. Figure  2d showed the spectrum of SiO2/GNPs hybrid material, compared with Figure  2c; it was clear that there appeared new stretching vibration peak of Si-O-Si groups at about 1,096 cm−1, and the peak at 796 cm−1 was attributed to the symmetric stretching of Si-O-Si groups as designed in Figure  1. All these data indicated that SiO2 fabricated on the surface of GNPs successfully. Figure 2 FTIR spectra of (a) f-GNPs, (b) PAA-GNPs,

(c) siloxane-GNPs, and (d) SiO 2 /GNPs hybrid material. Figure 3 Raman spectra of (a) f-GNPs and (b) SiO 2 /GNPs hybrid material. Raman spectra Raman spectroscopy is a powerful and useful technique to investigate the ordered or disordered crystal structures and assessing defects of graphene-based materials. It is well known that the typical features of carbon materials in Raman spectra are the G band at 1,580 cm−1 deriving from the E2g phonon of C sp2 atoms and D band at 1,350 cm−1 considered as a breathing mode of k-point photos of A1g symmetry which is assigned to local defects and disorder mostly at the edges of f-GNP platelet [33, 34]. Raman spectra of f-GNP and SiO2/GNPs hybrid material were shown in Figure  3.