Soluble short single-walled carbon nanotubes in aerated D(2)O emit in the near-infrared (NIR) region [picture: see text] with a quantum yield of (3.9+/-0.5) x10(-3) and a half-life of 7.65 micros. This emission is quenched by electron- acceptor molecules. Soluble short single-walled carbon nanotubes (sSWNT) are prepared by means of chemical fragmentation and purification of commercial SWNTs. The average length of the nanotubes, as estimated by microscopy, is 400 nm. Infrared spectroscopy studies reveal the presence of a significant population of carboxyl groups. The thermogravimetric profile of an sSWNT shows that this material is hydrophilic, contains carboxyl groups, and is almost free from inorganic impurities. In D(2)O solution, the obtained sSWNTs emit in the near-infrared (NIR) region with a quantum yield of (3.9+/-0.5)x10(-3), determined using the 1270 nm singlet oxygen emission as a reference standard. The temporal profile can be fitted with first-order kinetics and a half-life of 13.9 micros. The NIR emission is quenched through a static mechanism by 2,4,6-triphenylpyrylium (TP(+)), a typical electron acceptor.