Use of Cdse/ZnS quantum dots for sensitive detection and quantification of paraquat in water samples

• Analytical use of CdSe/ZnS quantum dots.
• Methodology for water solubilization of CdSe/ZnS QDs.
• Sensitive and selective reaction with paraquat herbicide.
• Application to water samples.

Based on the highly sensitive fluorescence change of water-soluble CdSe/ZnS core-shell quantum dots (QD) by paraquat herbicide, a simple, rapid and reproducible methodology was developed to selectively determine paraquat (PQ) in water samples. The methodology enabled the use of simple pretreatment procedure based on the simple water solubilization of CdSe/ZnS QDs with hydrophilic heterobifunctional thiol ligands, such as 3-mercaptopropionic acid (3-MPA), using microwave irradiation. The resulting water-soluble QDs exhibit a strong fluorescence emission at 596 nm with a high and reproducible photostability. The proposed analytical method thus satisfies the need for a simple, sensible and rapid methodology to determine residues of paraquat in water samples, as required by the increasingly strict regulations for health protection introduced in recent years. The sensitivity of the method, expressed as detection limits, was as low as 3.0 ng L−1. The lineal range was between 10–5 × 103 ng L−1. RSD values in the range of 71–102% were obtained. The analytical applicability of proposed method was demonstrated by analyzing water samples from different procedence.

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