Tea-derived carbon dots with two ratiometric fluorescence channels for the independent detection of Hg2+ and H2O

Abstract

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 Hg²⁺ and H₂O 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 Hg²⁺ 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 Hg²⁺ concentration (0–100 μM) is linear to A_{374 nm} through UV-vis assay. Otherwise, the linear determination of H₂O content (0–30%) is realized in another channel (I_green/I_blue). The good performance in the independent testing of Hg²⁺ and H₂O, demonstrate that the proposed N-CDs have potential in multifunctional detection.