Fluorescence Quenching Effects of Fe3+ Ions on Carbon Dots

In this study, we examined the frequently reported "selective fluorescence quenching effects" of Fe3+ ions on carbon dots. Instead of the believed "quenching effects" by Fe3+, the strong reduction of the fluorescence of carbon dots is likely because of the inner filter effect, which is caused by the strong ultraviolet (UV) absorption of Fe3+. With the addition of Fe3+ ions, the UV absorption increases dramatically, compared to other metal ions. When Fe3+ ions coexist with carbon dots (CDs) in the solution, most of the excitation light is absorbed by Fe3+ ions, decreasing the excitation light obtained by CDs. This phenomenon leads to the "fluorescence quenching." This finding helps us gain a better understanding of the fluorescence quenching effects of metal ions on carbon dots and understand the quenching effect of metal ions on other fluorescent materials.