One-step synthesis of nitrogen-doped carbon quantum dots for paper-based electrochemiluminescence detection of Cu2+ ions

A one-step hydrothermal method using glucosamine as the carbon and nitrogen source, mixed with dipotassium hydrogen phosphate (K2HPO4) in an aqueous solution, is used to prepare nitrogen-doped carbon quantum dots (N-CQDs). Compared with carbon quantum dots (CQDs) synthesized using glucose in a similar manner, N-CQDs show a much clearer green fluorescence at the long wavelength of ultraviolet light (365 nm) and a more stable and improved electrochemiluminescence (ECL) activity. A paper-based ECL sensor is developed with N-CQDs, based on the easy-scalable screen printing technology, and K2S2O8 is used as a co-reactant to detect Cu2+ ions. The ECL strength of the N-CQDs-K2S2O8 system increases with increasing Cu2+ ions concentration. The sensor shows overall excellent ECL stability, reproducibility, and selectivity, with a wide linear relationship ranging from 0.01 to 1000 μM in the detection of Cu2+ ions. This one-step synthesis of N-CQDs provides a feasible method for preparing portable paper-based ECL sensors for future applications.