Development of cysteine-doped MnO(2) quantum dots for spectrofluorimetric estimation of copper: applications in different matrices

Copper (Cu) plays a role in maintaining healthy nerve cells and the immune system. Osteoporosis is a high-risk factor for Cu deficiency. In the proposed research, unique green, fluorescent cysteine-doped MnO(2) quantum dots (Cys@MnO(2) QDs) were synthesized and assessed for the determination of Cu in different food and hair samples. The developed quantum dots were synthesized with the help of cysteine using a straightforward ultrasonic approach to create 3D fluorescent Cys@MnO(2) QDs. The resulting QDs’ morphological and optical characteristics were carefully characterized. By adding Cu ions, the intensity of fluorescence for the produced Cys@MnO(2) QDs was found to be dramatically reduced. Additionally, the applicability of Cys@MnO(2) QDs as a new luminous nanoprobe was found to be strengthened by the quenching effect grounded on the Cu–S bonding. The concentrations of Cu(2+) ions were estimated within the range of 0.06 to 7.00 µg mL(−1), with limit of quantitation equal to 33.33 ng mL(−1) and detection limit equal to 10.97 ng mL(−1). The Cys@MnO(2) QD technique was applied successfully for the quantification of Cu in a variety of foods, including chicken meat, turkey, and tinned fish, as well as in human hair samples. The chance that this novel technique could be a useful tool for figuring out the amount of cysteine in bio-samples is increased by the sensing system’s remarkable advantages, which include being rapid, simple, and economical. GRAPHICAL ABSTRACT: [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00216-023-04827-z.