A fluorescent sensor constructed from nitrogen-doped carbon nanodots (N-CDs) for pH detection in synovial fluid and urea determination

, -COOH, and -CONH- as active functional groups, which allowed the variable protonation/deprotonation of N-CDs to regulate the fluorescence emission intensities under changed pH values. Furthermore, upon combining urease-catalyzed hydrolysis of urea with increased pH values, a simple but effective fluorescence assay for urea was developed. The analytical performance for urea detection was the linear range of 0 to 10 mM with a detection limit of 0.072 mM. Additionally, the fluorescent sensor based on N-CDs was successfully applied for pH detection in synovial fluid and urea determination in serum.