Cysteamine capped CdS quantum dots as a fluorescence sensor for the determination of copper ion exploiting fluorescence enhancement and long-wave spectral shifts

•A new turn-on fluorescence sensor based CdS QDs was proposed.•Fluorescence emission of CdS QDs can be turned-on with large Stokes shift by Cu2 +.•Shows good selectivity towards the detection of Cu2 +•Can be used to detect Cu2 + at very low limit of detection of 1.5 μM

We described a turn-on fluorescence sensor for the determination of Cu2 + ions, utilizing the quantum confinement effect of cadmium sulfide quantum dots capped with cysteamine (Cys-CdS QDs). The fluorescence intensity of the Cys-CdS QDs was both enhanced and red shifted (from blue-green to yellow) in the presence of Cu2 +. Fluorescence enhancement was linearly proportional to the concentration of Cu2 + in the concentration range 2 to 10 μM. Other cations at the same concentration level did not significantly change the intensity and spectral maxima of Cys-CdS QDs, except Ag+. The limit of detection was 1.5 μM. The sensor was applied to the determination of Cu2 + in (spiked) real water samples and gave satisfactory results, with recoveries ranging from 96.7 to 108.2%, and with RSDs ranging from 0.3 to 2.6%.

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