Determination of IO4− and Ni2+ ions using l-cysteine-CdTe/ZnS quantum dots as pH-dependent fluorescent probes

Abstract

By using L-cysteine-CdTe/ZnS quantum dots (QDs) as pH-dependent fluorescent probes, a facile and sensitive method was proposed for the selective detection of IO₄⁻ and Ni²⁺ ions. L-cysteine-CdTe/ZnS QDs could be used as selective fluorescent probes to determine IO₄⁻ and Ni²⁺ ions at different pH conditions (pH 3.5 or 10.2, respectively). L-Cysteine-CdTe/ZnS QDs at pH 3.5 exhibited a selective response for IO₄⁻ ions with a wide linear range from 5.0 × 10⁻⁸ to 2.7 × 10⁻⁶ mol L⁻¹ and a detection limit of 3.6 × 10⁻⁹ mol L⁻¹ (single-to-noise ratio 3). Whereas in alkaline medium (pH 10.2), L-cysteine-CdTe/ZnS QDs were able to selectively detect Ni²⁺ ions at 4.0 nmol L⁻¹ with a limit of detection down to 5.9 × 10⁻¹⁰ mol L⁻¹. By analysis of UV-vis absorption and time-resolved luminescence spectra, the possible mechanisms of fluorescence quenching were discussed. The proposed method using L-cysteine-CdTe/ZnS QDs as pH-dependent fluorescent probes has been successfully used to determine IO₄⁻ and Ni²⁺ ions in environmental water samples.