Fig. 1. Schematic illustration of the femtosecond laser ablation system

Fig. 2. Surface-enhanced Raman spectra of the sample solution ablated with different single-pulse energies. (a) 0.04‒0.52 mJ; (b) 0.52‒1.48 mJ

Fig. 3. Ultraviolet absorption spectra of the sample solution ablated with different single-pulse energies

Fig. 4. Surface-enhanced Raman spectra. (a) Surface-enhanced Raman spectra of the sample solution ablated with 0.52 mJ single-pulse energy for different time; (b) integrated area (Asp2 and A_sp) of sp² region (1000‒1700 cm^-1) and sp region (1800‒2200 cm^-1) as a function of ablation time; (c) Raman spectra of raw single-walled carbon nanotubes (SWCNTs)

Fig. 5. Three-dimensional high-performance liquid chromatography. (a) Three-dimensional high-performance liquid chromatography of the sample solution ablated with 0.52 mJ single-pulse energy; (b)‒(d) ultraviolet absorption spectra of polyynes (C₈H₂, C₁₀H₂, and C₁₂H₂) obtained by high-performance liquid chromatography

Fig. 6. Peak intensity of ultraviolet absorption spectra. (a) Hydrogen bubble produced during the ablation; (b) peak intensity of ultraviolet absorption spectra of C₁₂H₂ from solution sample ablated under different laser power densities

Fig. 7. Femtosecond laser breaking chemical bonds of SWCNTs to form carbon atoms or C₂ free radicals

Fig. 8. Schematic illustration of polyynes forming. (a) Chemical bond of C₂ free radical; (b) the fourth bond of C₂ radical is destroyed by saturated femtosecond laser and can not form sp-orbital hybridization