An electrochemical sensor based on synergistic enhancement effects between nitrogen-doped carbon nanotubes and copper ions for ultrasensitive determination of anti-diabetic metformin.

Metformin (MET) is the primary medicine for type II diabetes, which produces carcinogenic byproducts during chlorine disinfection, so the detection of MET in aqueous environment is crucial. In this work, an electrochemical sensor based on nitrogen-doped carbon nanotubes (NCNT) has been constructed for ultrasensitive determination of MET in the presence of Cu(II) ions. The excellent conductivity and rich π-conjugated structure of NCNT facilitate the electron transfer rate of fabricated sensor and benefit the adsorption of cation ions. Cu(II) ions can chelate with MET to form MET-Cu(II) complex, which are easily accumulated on the surface of NCNT through cation-π interaction. Attributing to the synergistic enhancement effects of NCNT and Cu(II) ions, the fabricated sensor exhibits excellent analytical performances with a low detection limit of 9.6 nmol L, high sensitivity of 64.97 A mol cm and wide linear range of 0.3-10 μmol L. The sensing system has been successfully applied for rapid (20 s) and selective determination of MET in real water samples with satisfactory recoveries (90.2 %-108.8 %). This study provides a robust strategy for MET detection in aqueous environment and holds great promise for rapid risk assessment and early warning of MET.