Cysteamine-capped copper nanoclusters as a highly selective turn-on fluorescent assay for the detection of aluminum ions.

A new type of copper nanoclusters was synthesized by a one-pot reaction using cysteamine as a capping agent and reducing agent (Cys-CuNCs). The synthesized CuNCs exhibited a spherical shape and a monodisperse and strong fluorescent emission characteristic peak at 430nm when exciting at 330nm. The Cys-CuNCs were demonstrated as a fluorescent chemodosimeter for the selective detection of Al3+. In the presence of Al3+, the fluorescent emission of the Cys-CuNCs was considerably enhanced, while other studied metal ions did not show this phenomenon. The fluorescent intensity near 380nm linearly increased with an increasing Al3+ concentration. The proposed method provided a working range of 1-7µM with a low detection limit of 26.7nM and was applied to determine Al3+ in drinking water samples with satisfactory results.

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

We described a turn-on fluorescence sensor for the determination of Cu(2+) 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 Cu(2+). Fluorescence enhancement was linearly proportional to the concentration of Cu(2+) in the concentration range 2 to 10µM. 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 1.5µM. The sensor was applied to the determination of Cu(2+) 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%.

Selective turn-on fluorescence sensor for Ag+ using cysteamine capped CdS quantum dots: determination of free Ag+ in silver nanoparticles solution.

Cadmium sulfide quantum dots capped with cysteamine (Cys-CdS QDs) were demonstrated as a selective fluorescence probe for sensing of free trace silver ions. The fluorescence intensity of the Cys-CdS QDs can be enhanced only in the presence of free Ag(+) and the fluorescence spectrum was slightly red shift from the original spectra. In addition, the fluorescence intensities were linearly increased upon increasing Ag(+) concentration. At the optimized condition for Ag(+) detection, when adding other metal ions to the Cys-CdS QDs solution, fluorescence spectra of Cys-CdS QDs did not change significantly revealing good selectivity of the sensors towards Ag(+). The working linear concentration range was found to be 0.1-1.5 µM with LOD of 68 nM. The proposed sensor was then applied to detect free Ag(+) in the silver nanoparticles solution. The results showed that the proposed sensor can be efficiently used with good accuracy and precision providing the simple method for detection of free Ag(+) in silver nanoparticles of quality control products.