Highly selective circular dichroism sensor based on d-penicillamine/cysteamine‑cadmium sulfide quantum dots for copper (II) ion detection.

A highly selective circular dichroism sensor based on cysteamine-capped cadmium sulfide quantum dots (Cys-CdS QDs) was successfully developed for the determination of Cu. Basically, the Cys-CdS QDs are not active in circular dichroism spectroscopy. However, the circular dichroism probe (DPA@Cys-CdS QDs) can be simply generated in situ by mixing achiral Cys-CdS QDs with D-penicillamine. The detection principle was based on measuring the circular dichroism signal change upon the addition of Cu. The strong CD signal of the DPA@Cys-CdS QDs dramatically decreased in the presence of Cu, while other cations did not result in any spectral changes. In addition, the degree of the CD signal decrease was linearly proportional to the concentration of Cu in the range of 0.50-2.25 μM (r = 0.9919) with a detection limit of 0.34 μM. Furthermore, the proposed sensor was applied to detect Cu in drinking water samples with %recovery values of 102-114% and %RSD less than 6%.