Highly fluorescent nitrogen and boron doped carbon quantum dots for selective and sensitive detection of Fe ³⁺

Due to the essential role of Fe3+ in physiological and pathological processes, the detection of Fe3+ has drawn increasing attention in the field of disease diagnosis and environmental protection. However, most existing methods require either cumbersome sample pretreatment or sophisticated and expensive test equipment. Recently, carbon quantum dots have found a wide range of applications such as nanoprobes for Fe3+ determination, albeit with limited sensitivity and selectivity. Herein, we report core-shell carbon quantum dots B1N2CQDs via a two-step hydrothermal approach using citric acid, boric acid and ethylenediamine as precursors. The obtained B1N2CQDs exhibit excellent water solubility and remarkable stability as well as a high fluorescence quantum yield of 15.4%. In addition, the fluorescence of B1N2CQDs is quenched exclusively by Fe3+ with minimal interference from other metal ions. A linear relationship with R2 = 0.998 was observed between the fluorescence quenching capacity and the Fe3+ concentration in the range of 2-160 μM, with the limit of detection calculated to be 80 nM. Finally, the as-prepared B1N2CQDs were successfully applied as a highly efficient fluorescent probe for Fe3+ detection in river water samples and intracellular Fe3+ imaging in biological systems.