Fe-doped carbon dots with enhanced fluorescence: Facilitating Cu²⁺ detection and urea electro-oxidation

In this work, Fe-doped carbon dots (Fe-CDs) were synthesized using o-phenylenediamine as a precursor and FeCl₃·6H₂O as a metal dopant by a one-step hydrothermal method. Notably, Fe-doping not only enhances the fluorescence of CDs, but also causes a red-shift in the emission wavelength. More importantly, Fe-CDs exhibit responsive fluorescence quenching to Cu²⁺ with high selectivity, sensitivity and anti-interference ability, enabling the sensor to achieve a detection limit of 0.23 μM for Cu²⁺. The quenching mechanism is triggered by the synergistic sensing process of dynamic and static quenching. Additionally, doping Fe into CDs can effectively regulate the electron density distribution and energy gap of the CDs, significantly altering their surface active sites. This coupling effect further augments the activity of the urea oxidation reaction (UOR). When utilized to catalyze UOR, Fe-CDs can achieve a battery voltage of 1.39 V at a current density of 100 mA cm^-2 and demonstrate excellent 24-h stability. Therefore, Fe-CDs are a promising catalyst and have great significance in related fields such as energy conversion and urea treatment.