Figure 3. Effect of cosolvent concentration on exfoliation.

(a,d) Absorbance of exfoliated graphite (a) and MoS₂ (d) in various concentration of water–IPA cosolvent system as a function of sonication time. (b,e) Photographs of the exfoliated graphene in 5, 10, 30, 60, 100 w% IPA (b) and MoS₂ in 20, 30, 40, 60, 80 w% IPA (e) obtained after 3 h of sonication. (c,f) Absorbance of exfoliated graphene (c) and MoS₂ (f) in various cosolvent mixture plotted against surface tension (γ_lg), showing a peak around 25–30 mJ m⁻² for both graphite (c) and MoS₂ (f). The relation of γ_lgcosθ_c versus surface tension (γ_lg) is also plotted in the graph with the dotted line representing a fitting curve of γ_lgcosθ_c as a line guide to the eye.