Photochemical synthesis of highly fluorescent CdTe quantum dots for “on–off–on” detection of Cu(II) ions

A novel environment-friendly photoillumination procedure was developed to produce highly fluorescent thiol-capped CdTe quantum dots (QDs). Based on it, the hydrophilic QDs were incorporated into multilayer films by layer-by-layer self-assembly. It was found that the as-prepared nanocomposite presented high photostability and allowed highly sensitive and selective determination of copper(II) ions. Under optimum conditions, the FL quenching effect of low concentrations of copper(II) ions could be well described by Langmuir-type binding isotherm in the range from 0.02 to 1.0 μM, with a detection limit of 8.0 nM. Furthermore, at low concentration levels, it was observed that the FL intensity of nanocomposite could recover to optimal level with the attenuation rate less than 5.8% for five “on–off–on” times. At high concentrations, the FL responses fitted fairly well to the typical Stern–Volmer equation range from 1.0 to 30 μM, while the quenching process turned out to be irreversible.