Nuclear modification-enhanced electrochemiluminescence of naphthalimide for copper ion detection in traditional Chinese medicine Astragalus membranaceus.

This work designs and synthesizes three core-modified naphthalimide derivatives (NCD-B, NDI-I, and NDI-H). Benefiting from efficient intramolecular charge transfer and suppressed intermolecular π-π stacking, all three compounds exhibit remarkable electrochemiluminescence (ECL) performance. In particular, NDI-H functionalized with imidazole substituents delivers a strong ECL signal up to 17 000 a.u. and excellent long-term stability with an RSD of 0.32%. An ECL sensor for Cu2+ was further constructed based on NDI-H, which displays a favorable linear response in the range of 0-5000 μM and a low detection limit of 3.56 μM. With advantages of low background interference, simple operation, low probe and instrument costs, and excellent selectivity, this method has been successfully applied to the determination of Cu2+ in Astragalus membranaceus, providing a reliable ECL analytical strategy for heavy metal monitoring in traditional Chinese medicines.