A double-potential ratiometric electrochemiluminescence platform based on g-C₃N₄ nanosheets (g-C₃N₄ NSs) and graphene...

A new kind of convenient, low-cost double-potential ratiometric ECL sensing platform for the quantification of Cu²⁺ was developed with carbon nitride nanosheets (g-C₃N₄ NSs) and graphene quantum dots (GQDs) as ECL luminophores. g-C₃N₄ NSs mixed with multi-walled carbon nanotubes (MWCNTs) was immobilized on a glass carbon electrode (GCE) and produced strong cathodic ECL at a potential of -1.2 V (vs. Ag/AgCl), while GQDs in the solution gave anodic ECL at +2.5 V. MWCNTs were used here to amplify the ECL signal of g-C₃N₄ NSs. The addition of Cu²⁺ causes the cathodic ECL signal from g-C₃N₄ to decline, while the anodic ECL signal from GQDs remains unchanged. With the anodic ECL signal as an internal reference, a double-potential ratiometric ECL sensing platform for Cu²⁺ was established. The ratio of the cathodic signal intensity to anodic signal intensity showed a linear response to the Cu²⁺ concentration over a range from 5.0 × 10^-10 to 1.0 × 10^-6 mol L^-1 and the detection limit was 0.37 nmol L^-1 (3σ/S). Such a construction strategy alleviates the interference from the environment and therefore improves the detection accuracy of Cu²⁺. Compared with other methods for Cu²⁺ detection, this method is simpler and more sensitive.