Fig. 2: Effects of the solvent surface tension on PPC-assisted LPE.
a Surface tensions and energies of solvents used for LPE. SEsqrt denotes the square root of the surface energy. NMP, THF, and EA indicate N-methyl-2-pyrrolidone, tetrahydrofuran, and ethyl acetate, respectively. b Graphene concentration of as-exfoliated graphene solutions (Cexf) using the different solvents with and without PPC. The data with error bars present the average and standard deviation from 3 samples. c Comparison of Cexf with and without PPC in respect of (SEsqrt,G – SEsqrt,sol)2. Cexf,PPC and Cexf,ref indicate Cexf obtained with and without PPC, respectively. SEsqrt,G and SEsqer,sol imply SEsqrt for graphene and solvents, respectively. d Normalized optical absorbance of the as-exfoliated graphene solutions as a function of time for the different solvents with and without PPC. The data points are the measured absorbance at 660 nm, and the solid lines are curves generated based on the exponential decay model of Eq. (2). e A0 obtained from the exponential decay model curves. f Comparison of τ acquired from the exponential decay model curves with and without PPC in respect of (SEsqrt,G – SEsqrt,sol)2. τPPC and τref denote τ obtained with and without PPC, respectively.
