Figure 3. Optical characteristics of biocompatible SWCNTs.

For all optical measurements, diluted samples (× 40) were used. (a) Optical absorption spectra of biocompatible-surfactant-coated (9,4) SWCNTs (red), semiconducting SWCNTs (grey) and pristine HiPco SWCNTs (black). The concentration of each sample was adjusted to obtain the same absorbance at ∼725 nm, corresponding to S₂₂ of (9,4) SWCNTs. The resulting mass concentrations of (9,4), semiconducting, and pristine HiPco SWCNTs were 0.17, 0.52 and 0.64 mg ml⁻¹, respectively. (b) NIR fluorescence image of the samples. (c) NIR fluorescence intensity of the samples.