FIGURE 3 Dependence of a) CGand b) CG/CG,i onCG,i .
The effect of tM on FLG exfoliation was
explored by fixing CP = 2.0 mg
mL-1 and CG,i = 50 mg
mL-1. As observed from Figure 4a,CG (thusCG/CG,i )
increases steadily from 0.092 mg mL-1 attM = 5 min to 0.33 mg
mL-1 at tM = 80 min,
showing an empirical correlation of CG ∝tM 0.57. The exponents
close to 0.5−0.7 were also noticed in sonication exfoliation and other
instances of shear exfoliation and proposed to be process-independent,
reflecting a more fundamental behavior.7,9,49 Above 80
min of tM ,CG tends to saturate. On the other hand,
extension of tM decreases the lateral
size of FLG. With tM extended from 5 to
20, 80, and 180 min, the average lateral size of FLG determined by DLS
decreases from 829 ± 218 to 713 ± 180, 583 ± 115, and 304 ± 97 nm
(Figure 4b). Larger lateral size thus higher aspect ratio is desired for
many applications of FLG, such as polymer composites. Upon systematic
consideration of FLG size, exfoliation efficiency, andCG/CG,i , the
parameter combination of CP = 2.0 mg
mL-1, CG,i = 50 mg
mL-1, and tM = 80 min
is preferred for subsequent scale-up production of FLG.