Waste-derived graphene quantum dots on paper-based electrodes for electrochemiluminescence screening of tetracycline.

Herein, we report a paper-based electrochemiluminescence (ECL) sensor for tetracycline (TC) determination, integrating a waste-derived luminophore preparation strategy with a disposable sensing format. To establish the sensing interface, graphene quantum dots (GQDs) were synthesized from industrial waste diesel via chemical vapor deposition and electrochemical exfoliation and subsequently introduced into the reaction zone of screen-printed paper electrodes to form a low-cost analytical platform. Control experiments and spectral-overlap analysis suggest that perturbation of the sulfate-radical-dependent ECL pathway and a possible inner filter effect may both contribute to the signal attenuation. Their relative contributions were not quantitatively resolved in the present work. Under optimized conditions, the ECL intensity showed a linear relationship with the logarithm of TC concentration over 0.01-100 µM, with a calculated limit of detection of 9.57 nM. The method was preliminarily evaluated using TC spiked into a pretreated commercial milk matrix. Overall, this work provides a waste-to-value route for petrochemical by-product upcycling and a paper-based ECL strategy for trace antibiotic screening.