Figure 1.

Single-walled carbon nanotubes (SWCNTs) properties. (a) A graphene sheet segment with indexed lattice points. A nanotube with a chiral index (n,m) is obtained by rolling the sheet along a roll-up vector originating at (0,0) up to (n,m). The chiral angle α (from 0 to 30°) is measured between the roll-up vector and the horizontal zigzag axis; the tube circumference is the length of the roll-up vector. Nanotubes with chiral indexes for which mod (n-m,3) = 0 are metallic, whereas the rest are semiconducting. (b) The density of electronic states of a semiconducting single-walled carbon nanotube structure. Solid arrows depict the excitation and emission transitions of interest; dashed arrows denote nonradiative relaxation. (c) Most fluorophores, such as indocyanine green (ICG), undergo rapid photobleaching upon continuous illumination (blue). SWCNT emission (red) remains photostable even under high fluence irradiation (1.3 × 10⁷ W m⁻²). (d) SWCNTs fluoresce (blue) primarily in the near–infrared regime (900–1600 nm), where blood (red) and water (black) absorbance is minimal. The figure includes tissue data adapted from Wray et al. [87], reprinted with permission from Boghossian et al. [16], and used with permission from Wiley publication. (e) Excitation–emission profile of polymer-functionalized SWCNT suspension. Reprinted with permission from Bisker et al. [89] and used with permission from Nature Communications.