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

Area of Science:

• Materials Science
• Nanotechnology
• Analytical Chemistry

Background:

• Quantum dots (QDs) offer unique optical properties for sensing applications.
• Developing selective and sensitive detection methods for pharmaceuticals is crucial.
• Manganese (Mn)-modified cadmium selenide/cadmium sulfide (CdSe/CdS) core-shell QDs present novel fluorescence characteristics.

Purpose of the Study:

• To develop novel Mn-modified CdSe/CdS quantum dots.
• To investigate the interaction between these QDs and levodopa.
• To establish a sensitive fluorescence-based method for levodopa quantification.

Main Methods:

• Synthesis of citrate-capped Mn-modified CdSe/CdS quantum dots.
• Characterization of QD optical properties, including fluorescence quantum yield.
• Investigation of levodopa-induced fluorescence quenching.
• Optimization of detection parameters and validation of the quantitative method.

Main Results:

• The synthesized QDs exhibited narrow, symmetric emission and high fluorescence quantum yield (>41%).
• Levodopa selectively quenched the fluorescence intensity of the Mn-modified QDs.
• A linear correlation (R²=0.9996) was observed between quenched intensity and levodopa concentration (1–100 μM).
• A low limit of detection (2 × 10⁻⁷ M) was achieved.

Conclusions:

• A novel, sensitive, and selective fluorescence quenching method for levodopa detection was successfully developed using Mn-modified CdSe/CdS QDs.
• The method demonstrated excellent linearity and a low limit of detection.
• The proposed method accurately determined levodopa content in pharmaceutical tablets, showing good agreement with claimed values.