A ratiometric fluorescent and colorimetric dual-signal sensing platform based on N-doped carbon dots for selective and sensitive detection of copper(II) and pyrophosphate ion

A simple ratiometric fluorescent and colorimetric dual-signal sensing system for Cu 2+ and pyrophosphate ion (PPi) detection is established based on N-doped carbon dots (N-CDs) which are synthesized via one-step hydrothermal approach. In the strategy, 2,3-diaminophenazine (oxOPD), the oxidation product of o-phenylenediamine (OPD), can be adsorbed on the surface of N-CDs through electrostatic interaction, which efficiently quenches the fluorescence of N-CDs, meanwhile, oxOPD provides a new emission peak at 553 nm. In virtue of the selective oxidative and chromogenic reaction of OPD with Cu 2+ , a dual-readout sensing system for Cu 2+ is achieved. In addition, the redox and chromogenic reaction among them can be inhibited by PPi, which protects effectively the fluorescence of N-CDs from quenching. This sensing system exhibits good selectivity and sensitivity toward Cu 2+ and PPi over other analytes with a low detection limit of 23 nM and 0.7 μM, respectively. Furthermore, the proposed sensing system displays a prospective application for quantitative assay of Cu 2+ and PPi in practical samples.