l-Carnitine capped quantum dots as luminescent probes for cadmium ions

Luminescent and stable CdSe/ZnS core/shell quantum dots (QDs) capped with l-carnitine (LC) were firstly prepared in ethanol. The LC modifiers provided colloidal stability as well as surface passivation. LC capped QDs were sensitive to cadmium ions over other metal ions, such as Na+, K+, Mg2+, Ca2+, Ni2+, Zn2+, Fe2+, Ag+ and Pb2+. LC capped QDs were used to detect Cd2+ with a detection limit of 0.15 μM. It was found that the enhanced luminescence intensity of the LC capped QDs in a concentration of Cd2+ dependence is best described by a langmuir binding isotherm equation. The possible mechanism is discussed.