A circular dichroism sensor for selective detection of Cd2+ and S2- based on the in-situ generation of chiral CdS quantum dots.

We demonstrate an advance in the fabrication of circular dichroism (CD) sensors for detection of Cd2+ and S2- based on chiral CdS quantum dots (QDs) generated by a facile in-situ reaction. The chiral quantum dots are generated in solutions composed of Cd2+, S2-, cysteamine (CA) and L-penicillamine (L-PA), with the number of the generated particles limited by either the Cd2+ or S2- concentration. We show that the magnitude of the CD signal produced by the QDs is linearly related to the initial concentration of Cd2+ and S2-, with excellent selectivity over other ions. Our sensor functions over concentration ranges of 65-200μM and 7-125μM with detection limits of 59.7 and 1.6μM for Cd2+ and S2-, respectively. The sensor is applied in real water samples with results comparing favorably with those obtained from ICP-OES (for Cd2+) and HPLC (for S2-).