Assaying of Cu2+ with near-infrared l-cysteine-capped CdSeTe/CdS quantum dots and its effect on cell imaging

Near-infrared (NIR) core–shell CdSeTe/CdS quantum dots (QDs) modified with l -cysteine were synthesized in aqueous solution. The QDs had a special NIR-emitting spectrum, high fluorescence stability and low cytotoxicity. In addition, they exhibited an obvious fluorescence quenching when Cu 2+ was present. An NIR nanosensor was prepared for rapidly, sensitively, and selectively determining Cu 2+ in solution quantitatively and monitoring the changes in Cu 2+ in cells with fluorescence imaging in a semiquantitative way. The linear relationship between the relative fluorescence intensity (F 0 /F) and the concentration of Cu 2+ from 5.12 × 10 −8 M to 2.56 × 10 −5 M in solution was observed using an NIR fluorescence spectrophotometer with R 2 equal to 0.9958. Moreover, in the experiment with the fluorescence microscope, F 0 /F versus the concentration of Cu 2+ from 5.00 × 10 −8 M to 7.68 × 10 −6 M also showed a good linear relationship with R 2 equal to 0.9817. Practical water sample ion detecting experiments had good accuracy and recovery rates. Cell experiments showed that the NIR imaging intensity of cells was inversely proportional to the concentration of copper ions, therefore NIR QDs have great potential for detection of metal ions in solution and in cells.