Citrate-capped Mn-modified CdSe/CdS quantum dots as luminescent probes for levodopa detection in aqueous solution.

A novel kind of citrate capped Mn-modified CdSe/CdS quantum dots (QDs) was developed. The Mn-modified CdSe/CdS QDs had a narrow, symmetric emission and strong fluorescence with quantum yield over 41%. The interaction between the QDs and levodopa was investigated. The results showed that levodopa selectively quenched the fluorescence intensity of the QDs. Based on the fluorescence quenching of the synthesized QDs by levodopa, a simple, rapid and specific quantitative method for levodopa was proposed. The factors affecting the fluorescence detection for levodopa were studied. Under the optimum conditions, the quenched intensity of the fluorescence versus levodopa concentration from 1 to 100 μM gave a linear response with an excellent correlation coefficient of 0.9996, and the limit of detection (3σ/K) was 2 × 10(-7)M. The contents of levodopa in pharmaceutical tablets were determined by the proposed method and the results agreed with the claimed values.