As the reaction time reached 4 h (Figure  7b), SiO2 particles did not completely grow, but BIBF-1120 some little black points could be observed which were the miniatures of SiO2 particles. With the time growing, it could be seen that the surface of graphene were covered with SiO2 particles when the reaction time was 6 h (Figure  7c); SiO2 particles became larger than that of Figure  7b, but had not completely grown to round shape. Figure  7d showed that after 8-h growing, SiO2 particles

had grown fully, and the average size of SiO2 particles was 140 nm. Figure 7 TEM images of the growing process of SiO 2 /GNPs hybrid material with different times. (a) 2 h, (b) 4 h, (c) 6 h, and (d) 8 h. Analysis of orthogonal experiment According to the matrix, nine experiments were carried out and the average size of SiO2 particles was shown in Table  2. This table showed that the range of the size of SiO2 particles varies from 50 to 280 nm; these data were taken as the original data and used in the range analysis. The mean values of Ij/kj, IIj/kj, and IIIj/kj for different factors at different levels in the Pritelivir price range analysis

were shown in Table  4. For each factor, a higher mean value indicates that the level has a larger effect on the size of SiO2 particles. And the range value indicates the significance of the factor’s effect, and a larger range means the factor has a bigger impact on the size of SiO2 particles. Therefore, according to Table  4, compared with the range values of different factors, the factors’ level of significance are as follows: ammonia (103.4) > TEOS (86.7) > reaction time (43.3). The range value of ammonia is the largest, which means that the quality

of ammonia had the most important impact on the size of SiO2 particles. Table 4 Analysis of range of each other Column no. j = 1 2 3 Factors TEOS NH3 .H2O Time Ij I1 = 310 I2 = 280 I3 = 380 IIj II1 = 510 II2 = 520 II3 = 500 IIIj III1 = 570 III2 = 590 Megestrol Acetate III3 = 510 kj k1 = 3 k2 = 3 k3 = 3 Ij/kj 103.3 93.3 126.7 IIj/kj 170 173.3 166.7 IIIj/kj 190 196.7 170 Range 86.7 103.4 43.3 According to our analysis, the amount of ammonia affects the size of SiO2 particles most. With the increasing of the amount of ammonia from 0.6 to 1.8 g, the size of SiO2 particles increases continuously. The joining of ammonia can significantly see more contribute to the occurrence of hydrolysis and polycondensation reaction of TEOS. When adding NH3 .H2O to the solution, the OH anion made the silicon atoms negatively charged. As a result, Si-O bond weakened and eventually cracked. The products of hydrolysis reaction such as Si-OH and Si-OR dehydration or dealcoholation in the next polycondensation processing form Si-O-Si chain. Si-O-Si chains cross-linked continuously with each other to fabricate SiO2 particles finally. The hydrolysis rate will increase with the growing amount of ammonia, so the size of SiO2 particles also becomes larger.