One-Pot Hydrothermal Method Preparation of Cerium–Nitrogen-Codoped Carbon Quantum Dots from Waste Longan Nucleus as a Fluorescent Sensor for Sensing Drug Rifampicin

[Image: see text] Currently, the large-scale application of carbon quantum dots (CQDs) is usually limited by their low quantum yield and detection limit. Herein, the abandoned longan nucleus was used as a carbon source to synthesize cerium–nitrogen-codoped carbon quantum dots (Ce/N-CQDs) with strong luminescence intensity. In this work, the fluorescent properties and fluorescent quantum yield of CQDs may be improved by the single cerium-doped carbon quantum dots (Ce-CQDs) and the single nitrogen-doped carbon quantum dots (N-CQDs). Nevertheless, the Ce/N-CQDs exhibited intense fluorescence with a high quantum yield. Compared with CQDs, the quantum yield of Ce/N-CQDs was significantly increased from 5 to 32% and showed high photostability and good water solubility. The Ce/N-CQDs can be used for the direct detection of rifampicin (RFP) in human serum. The concentration demonstrated a good linear relationship in the range of 1.0 × 10(–7)–9.0 × 10(–6) mol/L, with a detection limit of 9.6 × 10(–8) mol/L.