Fig. 3. Raman spectra of the SWNT/PL–PEG–DFO solution, before and after the addition of Fe³⁺ using a 532 nm laser (A and B). Raman spectra of the SWNT/PL–PEG–DFO solution, before and after the addition of Fe³⁺ and Al³⁺ using a 785 nm laser (C and D).