Paper test strip for fluorescence detection of iron ion based on nitrogen, zinc and copper codoped carbon dots

In this study, a test strip for fluorometric analysis of iron ion (Fe³⁺) was constructed based on nitrogen, zinc and copper codoped carbon dots (NZC-CDs) as fluorescence probes. NZC-CDs were synthesized by hydrothermal method. The morphology, size, components, crystal state and optical properties of NZC-CDs were characterized by transmission electron microscope (TEM), Fourier-transform infrared (FT-IR), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), UV-vis absorption and fluorescence spectroscopy techniques, respectively. NZC-CDs exhibited bright blue fluorescence under UV lamp with a quantum yield at 17.76%. The fluorescence of NZC-CDs was quenched by Fe³⁺possibly due to the static quenching. The possible fluorescence quenching mechanism was also discussed. The quenching fluorescence was linear with the concentration of Fe³⁺in the range of 2.5-400μM with a low detection limit of 0.5μM. For the convenient detection, the test strips based on filter paper were employed for Fe³⁺assay. Moreover, the present approach was successfully applied in the determination of Fe³⁺in real samples including black fungus, duck blood and pork liver. The sensing method had the potential application in more food analysis.