Ratiometric fluorescence nanoprobe based on nitrogen-doped carbon dots for Cu and Fe detection.

Heavy metal ions pollution in environmental waters has an increasing impact on human health. As two common metal ions, copper ions (Cu) and ferric ions (Fe) widely exist in nature and play a vital role in life process. Therefore, it is significant to design sensitive and simple detection approaches for Cu and Fe. In our work, the ratiometric fluorescence analysis method (denoted as N-CDs/OPD) was established for Cu and Fe detection. The N-CDs exhibited a Cu and Fe fluorescence quenching response properties. The o-phenylenediamine (OPD) may be oxidized to 2,3-diaminophenazine (DAP) by Cu and Fe. With addition of Cu or Fe, the fluorescence of N-CDs (436 nm) was quenched and a new peak at 556 nm (DAP) appeared, which realized fluorescent ratiometric detection of Cu and Fe. The Cu concentration shows a good linear correlation versus fluorescence ratio (F/F) in the range of 10 to 30 µM (R = 0.9981) with detection limit (LOD) of 0.86 µM. In addition, a good linear relationship between fluorescence ratio (F/F) and Fe concentration in the range of 20 to 80 µM (R = 0.9880) with LOD of 7.12 µM. This nanoprobe realizes the detection of authentic samples successfully, which is expected to serve as a testing kit for analysis in water samples.