Paper-based electrodes with nitrogen-doped graphene quantum dots for detection of copper ions via electrochemiluminescence

Nitrogen-doped graphene quantum dots (N-GQDs) were prepared using pyrolysis, with citric acid and urea as the carbon and nitrogen sources, respectively, to be used for Cu2+ ion detection in a paper-based ECL sensor. Existing methods for Cu2+ detection require expensive equipment, specialized experimental chambers, or complex sample pretreatment procedures, which limit their functionality. Using first principles, the electronic and optical properties of graphene quantum dots (GQDs) and N-GQDs were calculated and analyzed. The N-GQDs showed clearer green fluorescence under long-wave ultraviolet light and a better, more stable electrochemiluminescence (ECL) performance. Using first principles, the electronic and optical properties of the GQDs and N-GQDs were calculated and analyzed, and A theoretical mechanism for the observed ECL enhancement in the N-GQDs was proposed. A paper-based ECL sensor with N-GQDs was then developed, using a screen-printing technique, to detect Cu2+ ions. The results showed that the ECL intensity of the sensor increased as the Cu2+ ion concentration increased, and the sensor demonstrated a linear detection range of 0.01–1000 μM. Overall, the sensor exhibited excellent ECL stability, reproducibility, and selectivity. This simple, inexpensive, and effective monitoring technique can be used to detect Cu2+ to prevent negative effects on human health and the environment.