Organic-free colloidal semiconductor nanocrystals as luminescent sensors for metal ions and nitroaromatic explosives

Exposed surfaces of organic-free colloidal semiconductor nanocrystals act as generic luminescent sensors for multiple analytes. S2- capped CdSe/CdSeS/CdS core/gradient-shell/shell nanocrystals are turn-on sensors for Cd2+ ions (110 pM) in an aqueous medium with physiological pH 7.4. A similar organic-free semiconductor nanocrystal shows luminescence turn-off sensing for 2,4,6-trinitrophenol, a known explosive.