Mercaptosuccinic acid modified CdTe quantum dots as a selective fluorescence sensor for Ag+ determination in aqueous solutions

Abstract

Water-soluble cadmium telluride quantum dots capped with mercaptosuccinic acid (MSA-CdTe QDs) were prepared for the selective and sensitive fluorescence probing of silver(I) ion. The fluorescence intensity of the MSA-CdTe QDs could be quenched only in the presence of Ag⁺, and the relative fluorescence intensity was decreased as a linear function of Ag⁺ concentration. Moreover, the proposed sensor was free from common interfering metal ions. The MSA-CdTe QDs were 3.0 nm in particle size and the maximum photoluminescence wavelength was 558 nm. Better sensitivity was obtained with 4.5 × 10⁻⁴ mol L⁻¹ MSA-CdTe QDs in 200 mmol L⁻¹ phosphate buffer (pH 9.0) for a reaction time of 30 min. A linear response between the relative fluorescence intensity, and the concentration of Ag⁺ was obtained over the range 0.4 to 8 μmol L⁻¹, with a relative standard deviation of 3.6% (n = 5) for 1.5 μmol L⁻¹ and a detection limit of 54 nmol L⁻¹. The proposed method was applied for the determination of Ag⁺ in two fixer samples at the μmol L⁻¹ level. The spike recovery at a spiked level of 15 μmol L⁻¹ varying from 89.4% to 92.3%, and good agreement between the results by the proposed and AAS methods proved the accuracy of the proposed method.