A ratiometric electrochemiluminescent strategy for sensitive detection of dopamine based on g-C3N4/luminol-functioned carbon spheres

Ratiometric electrochemiluminescence (ECL) assays have attracted widespread attention in biosensing owing to their precise measurements by eliminating environmental interferences. In this work, g-C₃N₄, gold nanoparticles, CuO and luminol were integrated onto hollow carbon spheres (HCS) in sequence to fabricate potential-resolved ECL nanoprobes. The system consists of g-C₃N₄ as cathode ECL emitters and luminol as anode ECL emitters. The ECL of g-C₃N₄ is quenched by CuO due to the resonance energy transfer (RET). However, after adding dopamine (DA), the ECL signal is restored due to the redox reaction between CuO and DA. Meanwhile, there is a quenching effect between DA and luminol because DA interferes with the radical reaction process of luminol. Therefore, DA causes the reciprocal changes in cathodic ECL and anodic ECL. This phenomenon can be leveraged to create a ratiometric ECL signal, enabling the quantitative detection of DA. The developed ECL sensor exhibited a sensitive detection toward DA, performing a wide linearity in the range 5.0 × 10^–4 ~ 1.0 × 10^–9 M with a low detection limit of 2.3 × 10^–11 M (S/N = 3). Furthermore, this strategy exhibited a good practicality to detect DA in human urine, providing a promising strategy in ECL bioanalysis.

Graphical abstract