Tea-derived carbon dots with two ratiometric fluorescence channels for the independent detection of Hg 2+ and H 2 O.

Ratiometric fluorescence carbon dots (CDs) that serve as probes have attracted more attention on account of their unique optical properties, low toxicity, anti-interference, and internal reference. However, the facile fabrication of CDs with the aim of detecting multiple targets through mutually independent response channels is always a challenge. Herein, multifunctional label-free N-doped ratiometric fluorescence CDs (N-CDs) are developed from tea leaves extract and o -phenylenediamine by a mild solvothermal method. The prepared N-CDs are tailored with nitrogen- and oxygen-containing functional groups on the surface and contribute to splendid hydrophilia. Two completely independent ratiometric fluorescence channels of N-CDs, respectively, respond to Hg 2+ and H 2 O in a mutually independent manner. Based on the interactions of N-Hg and O-Hg, N-CDs achieve an excellently sensitive and selective detection for Hg 2+ in the channel of I 387 nm / I 351 nm , giving a linear relationship in the range of 0-50 μM. Also, a wide range of Hg 2+ concentration (0-100 μM) is linear to A 374 nm through UV-vis assay. Otherwise, the linear determination of H 2 O content (0-30%) is realized in another channel ( I green / I blue ). The good performance in the independent testing of Hg 2+ and H 2 O, demonstrate that the proposed N-CDs have potential in multifunctional detection.