A circular dichroism sensor for Ni2+ and Co2+ based on l-cysteine capped cadmium sulfide quantum dots

• Demonstrated a new efficient sensor platform based quantum dots.
• Used chiral quantum dots as CD sensor for the detection of heavy metal ions for the first time.
• The proposed CD sensor showed highest selectivity towards Ni2+ and Co2+.
• Low detection limits of 7.33 μM and 1.13 μM for Ni2+ and Co2+, respectively.
• Can be used in real water samples comparing with ICP-OES.

A new circular dichroism sensor for detecting Ni2+ and Co2+ was proposed for the first time using chiral chelating quantum dots. The detection principle was based on changing of circular dichroism signals of the chiral quantum dots when forming a chiral complex with Ni2+ or Co2+. l-Cysteine capped cadmium sulfide quantum dots (l-Cyst-CdS QDs) were proposed as a chiral probe. The CD spectrum of l-Cyst-CdS QDs was significantly changed in the presence of Ni2+ and Co2+. On the other hand, other studied cations did not alter the original CD spectrum. Moreover, when increasing the concentration of Ni2+ or Co2+, the intensity of the CD spectrum linearly increased as a function of concentration and could be useful for the quantitative analysis. The proposed CD sensor showed linear working concentration ranges of 10–60 μM and 4–80 μM with low detection limits of 7.33 μМ and 1.13 μM for the detection of Ni2+ and Co2+, respectively. Parameters possibly affected the detection sensitivity such as solution pH and incubation time were studied and optimized. The proposed sensor was applied to detect Ni2+ and Co2+ in real water samples, and the results agreed well with the analysis using the standard ICP-OES.

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