A double-potential ratiometric electrochemiluminescence platform based on g-C₃N₄ nanosheets (g-C₃N₄ NSs) and graphene quantum dots for Cu²⁺ detection

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 x 10(-10) to 1.0 x 10(-6) mol L-1 and the detection limit was 0.37 nmol L-1 (3 sigma/S). Such a construction strategy alleviates the interference from the environment and therefore improves the detection accuracy of Cu-2(+). Compared with other methods for Cu2+ detection, this method is simpler and more sensitive.