Fig. 4: Characterization of graphene exfoliated with PPC.

a Fourier-transform infrared (FTIR) spectra of graphene exfoliated with and without PPC. b Enlarged FTIR spectrum for the box in a. c Redispersion rate of graphene prepared with and without PPC in THF and A0 of the redispersed solutions for the exponential decay model of Eq. (2). The gray dotted line indicates A0 of the as-exfoliated graphene solution based on THF with PPC. d Scanning electron microscopy image of graphene after removing PPC. e Raman spectra of the graphene (black) after PPC removal and the graphite (gray) used for LPE of the graphene. f, g Thickness (f) and lateral size (g) distributions of the graphene characterized after PPC removal on Si/SiO2 by atomic force microscopy.