Ratiometric fluorescent and colorimetric dual-signal nanoprobe for the detection of Cu2+ and Fe3+ in industrial ethylene glycol

Iron and copper ions has been confirmed to be an impurity generated during the production of coal-based ethylene glycol. Therefore, a highly sensitive fluorescent probe based on N-doped carbon dots (N-CDs) is constructed by two different mechanisms for the independent detection of Cu 2+ and Fe 3+ in ethylene glycol. In this method, Cu 2+ undergoes an oxidation-reduction reaction with o -phenylenediamine (OPD), leading to the formation of 2,3-diaminophenazine (oxOPD). oxOPD emits a fluorescence signal, and simultaneously, fluorescence resonance energy transfer (FRET) occurs between N-CDs and oxOPD, resulting in the quenching of the fluorescence intensity of N-CDs. Owing to the selective oxidation reaction and colorimetric response of OPD with Cu 2+ , a ratiometric fluorescent and colorimetric dual-signal probe for detecting Cu 2+ is successfully developed. Furthermore, Fe 3+ can effectively quench the fluorescence of N-CDs through the static quenching. Under optimized conditions, the probe demonstrates excellent selectivity and sensitivity to Cu 2+ and Fe 3+ , a wide linear response range and a low detection limit (LOD). The probe was applied to the detection of Cu 2+ and Fe 3+ in various types of industrial ethylene glycol (high ethylene glycol content, industrial-grade ethylene glycol and polyester-grade ethylene glycol) with satisfactory recovery rate. The probe provides a promising prospect for the routine detection of Cu 2+ and Fe 3+ in industrial ethylene glycol.