Fig. 1. Schematic of set-up used to produce graphene nanosheets showing laser source, reflecting mirror, rotating base, graphite target and covering liquid column.

Fig. 2. FE-SEM micrographs of FG1 (a), FG2 (b) and NG (c) surface microstructures before the laser treatment. Both of FG1 and FG2 are consisted of exfoliated graphite flakes rolled into a sheet, and NG is with irregular orientation on the surface.

Fig. 3. FE-SEM images of prepared and separated ablated species: (a) few-layer graphene by ablation of FG1 in acetone with 532?nm pulses; (b) few-layer graphene by ablation of FG2 in acetone with 532?nm pulses; (c) carbonaceous nanostructures resulted from ablation of NG in acetone with 532?nm pulses; (d) graphene sheets with residual nanoparticles produced by laser ablation of FG1 at 1064?nm (the inset shows the particles size distribution fitted with a log-normal function); (e) few-layers of graphene obtained by laser ablation of FG2 at 1064?nm in acetone (D: particle size; <D>SEM: average diameter; σD: deviation of particle size).

Fig. 4. FE-SEM images of graphene nanosheets prepared by laser ablation of FG1 in acetone (a), FG1 in DI water (b), FG1 in DMF (c), FG2 in acetone (d), FG2 in water (e) and FG2 in DMF (f).

Fig. 5. (a) XRD patterns of (a1) FG1, (a2) FG2, few-layer graphene prepared by laser ablation with the optimized parameters of (a3) FG1, and (a4) FG2 and (b) UU-Vis-NIR absorption spectra of few-layer graphene obtained by laser ablation of FG1 and FG2 with optimized parameters.

Fig. 6. Original (a-d) and deconvoluted (e-h) Raman spectra of FG1 (a, e), FG2 (b, f) and few-layer graphene prepared by laser ablation with optimized parameters for FG1 (c, g) and FG2 (d, h).

Fig. 7. TEM images of curled graphene at low (a) and high (c) magnification, and HRTEM images from cross-section (b, d) of few-layer graphene prepared by laser ablation of FG1 sample.

Fig. 8. XPS of optimized few-layer graphene sample: (a) survey scan; (b) high-resolution scan in C 1s region.

Fig. 9. FE-SEM images of surface of FG1 sample after 5?min laser ablation: (a) center of target; (b) edge of target.