Concentration-modulated dual-excitation fluorescence of carbon dots used for ratiometric sensing of Fe3+

The development of ratiometric fluorescence sensing platforms with simple synthetic routes and good antiinterference capacities are of great importance for their further application. Herein, hyperbranched polyethylenimine passivated carbon dots (HPEI-CDs) with concentration-modulated dual-excitation fluorescence property were synthesized. At a low concentration, HPEI-CDs only showed one fluorescence center, while at a relatively high concentration, its excitation peak around 355 nm would split into two peaks. Energy level splitting and broadening were demonstrated to be the origin of such dual-excitation behavior. Based on the dualexcitation signals, HPEI-CDs could serve as a ratiometric sensor for the detection of Fe3+ in aqueous solution. The assay exhibited a wide linear response concentration range (2?360 ?M) with a limit of detection of 0.47 ?M. Significantly, benefiting from the high concentration of HPEI-CDs, the sensor showed good selectivity and excellent anti-interference capacity. In addition, this nanosensor was successfully applied for the detection of Fe3+ in real water samples with satisfactory recoveries.

Automated summary

The study synthesized HPEI-CDs with concentration-modulated dual-excitation fluorescence property and successfully detected Fe3+ using them as a ratiometric sensor, demonstrating a wide linear response concentration range and low detection limit. The sensor showed good selectivity and anti-interference capacity due to the high concentration of HPEI-CDs.