Drones tag and track quarry using nanoparticle sprays

Drones tag and track quarry using nanoparticle sprays - tech - 21 August 2013 - New Scientist: 

"Interest in tagging technology has been driven in part by growing pressure on the White House over civilian deaths in US drone attacks. During a recent visit to Pakistan, US Secretary of State John Kerry stated that drone strikes there will end "very, very soon". Tagging by drones would allow people to be tracked for subsequent arrest.
Voxtel's taggants are based on quantum dots – semiconductor nanocrystals less than 50 atoms across. Because of quantum effects, they absorb and emit light at specific wavelengths. The company has demonstrated a taggant powder that, when illuminated with an invisible ultraviolet laser, can be detected by infrared cameras 2 kilometres away. The powder is delivered as an aerosol that clings to metal, glass and cloth, and batches can be engineered to have distinct spectral signatures.
The nanocrystals would be sprayed by a hand-launched drone such as the Raven (pictured). With a wingspan of less than 1.5 metres, it is quiet and has a range of several kilometres. A larger Predator drone could then illuminate the target with an ultraviolet laser and track its progress."