The unique one-dimensional hollow structure of SWCNTs provides an excellent template for aligning molecules in one dimension, by encapsulating them in the interior SWCNT channel. Many different molecules have been encapsulated, from water to various solvent molecules that can tune the optical properties of the SWCNTs and functional dye molecules. In particular the latter can photosensitize the SWCNTs (through energy transfer), dope the SWCNTs (through electron transfer) or can create new properties by the alignment of the molecules inside the SWCNTs (e.g. phase transitions). By changing the endohedral content of SWCNTs, their optical properties can be highly influenced, e.g. shifting the optical transitions and vibrational frequencies of the SWCNTs. This is investigated in a chirality-dependent manner.
