Colorimetric and fluorimetric dual mode detection of Fe2+ in aqueous solution based on a carbon dots/phenanthroline system

In this work, green fluorescent carbon dots with a high relative quantum yield of 74.13% were synthesized by using one-pot hydrothermal hydrolysis of m-phenylenediamine (mPD) and PEG 1500 in H2SO4 solution at 180 °C for 10 h (mPD-CDs). In the presence of mPD-CDs, Fe2+ can form a complex with 1,10-phenanthroline (Fe(II) – phenanthroline) without interference from mPD-CDs, which has an absorption peak centered at 512 nm and its absorbance is sensitive to the concentration of Fe(II) – phenanthroline. Accordingly, a colorimetric method for the detection of Fe2+ was constructed with a limit of detection (LOD) of 2.98 μM. Moreover, the absorption spectrum of the Fe (II)-phenanthroline complex is overlapping with the excitation and emission spectra of mPD-CDs located at 440 and 516 nm, respectively, resulting in an inner filter effect (IFE) which is sensitive to the concentration of Fe(II) – phenanthroline. Correspondingly, a fluorimetric method for the detection of Fe2+ based on the mPD-CDs/phenanthroline system was built with a LOD as low as 0.59 μM. Therefore, colorimetric and fluorimetric dual mode detection of Fe2+ in aqueous solution can be achieved by a carbon dots/phenanthroline system. Keywords: Carbon dots, IFE, Colorimetry, Fluorimetry, Fe2+