Mercaptopropionic acid-capped CdZnTe Quantum dots as Fluorescence Probe for Sensitive Detection of Cr(III) ions

Although Cr(III) ions are essential for the human body, excessive amounts can lead to skin inflammation, allergic reactions, and genotoxicity. A highly sensitive fluorescence probe was developed using mercaptopropionic acid (MPA) capped CdZnTe quantum dots (QDs) synthesized via an aqueous solution heating method for precise detection of Cr(III) ions. The synthesized MPA-CdZnTe QDs had a size of 2.38 ± 0.13 nm and exhibited a zinc-blende structure, with MPA molecules effectively capping the surface through Cd-S bonds. Investigation into the effects of reflux times and solution pH on the absorption and fluorescence spectra of MPA-CdZnTe QDs revealed the occurrence of Ostwald ripening during prolonged reflux processes. The quantum yield (QY) of the synthesized CdZnTe QDs could reach 89%, and the QY was higher under acidic conditions than alkaline. Leveraging the quenching effect of Cr(III) ions on MPA-CdZnTe QDs, a robust method for the quantitative detection of trace amounts of Cr(III) ions was established. Linear quenching behavior was observed within the concentration range of 3.33 × 10^- 6 to 5.00 × 10^- 4 mol L^- 1 for Cr(III) ions, with the fluorescence quenching rate described by a linear regression equation: 1-F/F₀ = 0.218 + 829.5268C_Cr(III). The limit of detection was determined to be 2.63 × 10^- 6 mol L^- 1. The mechanism of the fluorescence behavior of MPA capped CdZnTe QDs towards Cr(III) ions was photo-induced electron transfer.