Valorization of olive pruning lignocellulosic residues into carbon dots: A sustainable approach for discrimination of Iron species

Herein, carbon dots (CDs) obtained from biochar of olive tree pruning residues (BC-OTPR) were synthesized at varying pyrolysis temperatures (500, 600, and 700 °C). The spectroscopic features of the CDs were further explored in the context of metal ion detection, specifically focusing on the discrimination of iron species. Significant fluorescence quenching upon interaction with iron (III), compared to iron (II) and other metal ions, was observed, indicating their potential as sensitive probes. In the presence of hydrogen peroxide and via the Fenton reaction, iron (II) was quantitatively oxidized into iron (III) - the determinable form, allowing for iron speciation. Synthesized CDs were analyzed using UV-Vis spectroscopy. Transmission Electron Microscopy (TEM) images revealed the uniform spherical morphology. Using the FT-IR analysis, transformation of hemicellulose and lignin present in the BC-OTPR into CDs with unique functionalities was corroborated. The CDs exhibited excitation-dependent fluorescence behavior, showcasing their potential for spectroscopic applications. Regression modeling was employed to investigate variables influencing iron detection. Notably, the CDs displayed linear behavior spanning over a range of 1.186 μM - 7.984 μM with a low limit of detection (LOD) of 0.5 μM of iron (III). Validation of precision and accuracy confirmed CDs' efficacy for analyzing food supplements and water samples.