Tetracycline detection via carbon dots-Fe coordination from Chromolaena odorata using a portable device.

Tetracycline residues in aquatic ecosystems, resulting from widespread antibiotic use, pose significant risks by fostering antibiotic resistance and threatening ecological and human health. Addressing the need for rapid, sensitive, and portable tetracycline detection, this study presents a novel device utilizing iron-coordinated carbon dots (CDs-Fe) derived from Chromolaena odorata as a peroxidase-mimic nanozyme. Synthesized via a one-step hydrothermal method, the CDs-Fe nanozyme exhibits enhanced catalytic activity, enabling a colorimetric assay with 3,3',5,5'-tetramethylbenzidine (TMB) and hydrogen peroxide (H₂O₂). Tetracycline detection relies on the nanozyme's peroxidase-like activity, where tetracycline competitively inhibits TMB oxidation, reducing the absorbance at 652 nm due to surface adhesion and substrate competition. The assay achieves a detection limit of 1.34 μM and a linear range of 17 to 67 μM. A portable Arduino-based device, fabricated via 3D printing with smartphone-enabled Bluetooth data reading, was developed for on-site tetracycline monitoring in real water samples, showing recoveries of 95 to 102% and high selectivity against other antibiotics. Validated against UV-vis spectrophotometry, this green-synthesized, cost-effective system offers a sustainable and field-deployable solution for environmental water quality assessment.