A novel and facile synthesis of TGA-capped CdSe@Ag2Se core-shell quantum dots as a new substrate for high sensitive and selective methyldopa sensor

• The TGA-capped CdSe@Ag2Se core-shell quantum dots have been successfully synthesized.
• The influence of shell concentration in particle size and optical properties of core-shell was described.
• A novel TGA-capped CdSe@Ag2Se core-shell quantum dots modified GC-electrode as sensor was applied to determine methyldopa in biological samples without any interference.
• High electrocatalytic activity observed for redox reaction of methyldopa.
• The developed QDs sensor is rapid, sensitive and selective with high reproducibility.

In this work, we offer a new approach to synthesize the CdSe@Ag2Se core–shell fluorescent quantum dots as a novel and sensitive electrochemical sensor for methyldopa by casting of an aliquot of thioglycolic acid capped CdSe@Ag2Se on a glassy carbon electrode surface. Characterizing the CdSe@Ag2Se was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), FT-IR spectroscopy, photoluminescence spectroscopy, UV–vis and cyclic voltammetry techniques. Under the optimal experimental conditions (pH = 2), the current response of the electrochemical sensor obtained with differential pulse voltammetry was increased linearly with methyldopa concentrations in the wide range from 0.09 to 60 μmol L−1, with the detection limit of 0.04 μmol L−1. The proposed sensor was successfully used for analysis of methyldopa in biological and pharmaceutical samples without any interference from uric acid and ascorbic acid due to its high sensitivity and selectivity, good repeatability and reproducibility, and low detection limit.

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