Confined synthesis of phosphorus, nitrogen co-doped carbon dots with green luminescence and anion recognition performance

Carbon nanomaterials have aroused considerable interests due to excellent optical performances, but most of achieved carbon dots possess blue luminescence under UV-light irradiations. Herein, we report the preparation of phosphorus and nitrogen co-doped carbon quantum dots (PNCQDs) via hydrothermal method by employment of 1,3-phenylenediamine, citric acid and H 3 PO 4 as precursors. The particle size of the water-soluble PNCQDs is in the range between 4 and 6 nm and the average diameter is determined to be 4.75 nm. The resulted quantum dots give rise to bright green emission at 504 nm and the excitation-dependent behavior has been found. Moreover, it demonstrates luminescence stability toward a broad pH range from 1 to 10. Fluorometric titration studies reveal that close interactions occur between carbon dots and nitrite ions and a switched off effect has been achieved. In addition, prospective application of the quantum dots in tap water and live cells has also been demonstrated.