Internal-calibration dual-potential ratiometric electrochemiluminescence sensor for tetracycline based on competitive co-reactant consumption

In this work, a dual-potential ratiometric electrochemiluminescence (RECL) sensor for the detection of tetracycline (TC) was constructed based on TiO 2 @g-C 3 N 4 (luminophore) and MWCNTs@Au NPs (promoter). The RECL signals were derived from the anodic peak (TiO 2 @g-C 3 N 4 –TPrA) and the cathodic peak (TiO 2 @g-C 3 N 4 –K 2 S 2 O 8 ). With the addition of TC, the anodic ECL signal remained unchanged and served as an internal reference, while the cathodic ECL signal decreased due to competitive co-reactant consumption. This ratiometric readout mitigates false-negative results commonly encountered in single-output ECL assays by correcting for nonspecific signal fluctuations. Under optimal conditions, a linear relationship was observed between the ratiometric signal (I a /I c ) and the logarithm of TC concentration (lgC TC ) from 1.0 × 10 −12 to 1.0 × 10 −8  mol L −1 . The linear equation was I a /I c  = 1.056 + 0.057 lgC TC (R 2  = 0.997). The detection limit was 3.3 × 10 −13  mol L −1 (S/N = 3). The proposed sensor was successfully applied to detect TC in real samples.