Sensitive detection of levofloxacin and copper (II) based on fluorescence “turn on-off” of biomass carbonized polymer dots

A novel type of biomass carbonized polymer dots (CS-CPDs) with green fluorescence emission were synthesized via a one-step microwave-assisted method, using chitosan and maleic acid as the precursors. The fluorescence intensity of CS-CPDs was selectively enhanced (turn on) with increasing levofloxacin (LEV) concentration based on Aggregation Induced Emission Enhancement. The linear range of this method was 1–35 μmol/L, with the limit of detection of 0.20 μmol/L. Furthermore, we demonstrated that the fluorescence intensity of CS-CPDs/LEV was restored (turn on-off) due to the addition of copper (II), which could assemble a more stable Cu2+/LEV complex through coordination. For the first time, CS-CPDs were utilized as a selective fluorescent "turn on-off" probe for the continuous detection of LEV and Cu2+. Excellent results were also obtained in environmental water samples analysis with recoveries ranging of 91.3–99.6% and 97.7–113.4%, respectively. Moreover, the prepared CS-CPDs exhibited excellent optical stability and large Stokes shift (139 nm), which predicted broad application prospects in the field of fluorescence sensing.