Fluorometric and colorimetric detection of cerium(IV) ion using carbon dots and bathophenanthroline-disulfonate-ferrum(II) complex

Cerium, an abundant lanthanide element, is widely used in human industry. The accumulation of Ce4+ ion, however, will damage the environment and biological organism. Therefore, its facile detection is highly needed. Herein, we design a hybrid sensing platform consisting of carbon dots (C-dots) and bathophenanthroline-disulfonate-Fe2+ complex (Bphen-Fe2+) for trace-level determination of Ce4+. Based on inner filter effect (IFE), the red-colored Bphen-Fe2+ complex severely quenches the fluorescence of C-dots. After addition of Ce4+, Fe2+ is oxidized to Fe3+, and the colorless Bphen-Fe3+ complex generates, which weakens the IFE efficiency and leads to the fluorescence recovery of C-dots. Meanwhile, due to the decreasing amount of Bphen-Fe2+ upon Ce4+ addition, the red color of the solution gradually fades, which enables visual detection of Ce4+ by the naked eyes. Under the optimized conditions, the C-dots/Bphen-Fe2+ system realizes the fluorometric and colorimetric sensing of Ce4+ in the range of 0.5–100 and 1.9–80 μM, with the limits of detection as low as 0.5 and 1.9 μM, respectively. This method also shows high selectivity over other common ions, and has an excellent applicability for monitoring of Ce4+ in real water samples.