One-pot solvothermal preparation of triple-emission N, Cl doped carbon quantum dots from waste traditional Chinese medicines as a fluorescent sensor for sensing water and Cr (Ⅵ)

In this research, N, Cl doped carbon quantum dots (CQDs) with triple-fluorescence centers was prepared by one-pot solvothermal method from waste traditional Chinese medicines as the raw material. The obtained N, Cl doped CQDs showed purple, yellow and red fluorescence under the 326, 380 and 578 nm excitation, respectively, of which red fluorescence was induced by the increase of concentrations and sensed rapidly water contents in 30–100% range with a limited of detection (LOD) of 0.65%. The obtained CQDs was applied for sensing Cr (Ⅵ) by triple channels, which exhibited the high selectivity and sensitivity for Cr (Ⅵ) with the LOD of 0.28, 0.87 and 0.90 μM, respectively. And its derivative materials exhibited the good linear range with 10–100 μM and 5–250 μM taking purple fluorescence as the response signal, respectively. The recoveries of N, Cl doped CQDs in tap water and sludge were in 93–110% range, suggesting a feasible avenue for accurate and rapid sensing of Cr (Ⅵ).