Figure 1.
(a) A carbon nanotube. The d2 diameter indicates a single-walled material, whereas d1 indicates the total diameter of a double-walled material. Multi-walled CNTs consist of additional lattice layers, (b) A carbon Bucky Fullerene with diameter d. (c) A carbon quantum dot with diameter d. (d) A single-walled carbon nanohorn segment of diameter d which tapers at an angle towards its tip. The arrow points towards the aggregate star structure. (e) An amorphous carbon particle with hydrophilic oxygen functionalities (hydroxyl: OH, carboxylic: COOH).