A highly blue luminescent nitrogen doped carbon dots (N-CDs) was prepared using citric acid and l-lysine via one pot hydrothermal treatment. The method is based on the competition between selenite oxyanion with carboxylate and hydroxyl groups on the surface of N-carbon dots for europium ions binding. N-CDs could be readily quenched upon addition of europium ions owing to high affinity of carboxylate and hydroxyl groups at the surface of carbon dots to Eu3+ leading to aggregation of N-CDs (state OFF). After selenite addition, disruption of the aggregated N-CDs takes place, leading to restoration of the quenched fluorescence (State ON). The repeatability was less than 3.2% for selenite in both standard and real samples (n=3). The method provides a simple procedure enabled selective detection of selenite in the presence of 12 other coexisting anions with a linear range of 0.078 to 21.4 μg mL1 and a limit of detection of 53.0 ng mL1 (S/N=3). The accuracy and precision were evaluated based on the detection of selenite in health care products with satisfactory results. Compared with other conventional techniques, the Eu3+-adjusted N-CDs "OFF-ON" fluorescent probe is highly selective, rapid, operating simplicity, eco-friendly, and low cost for selenite determination.
