Sulfur-nitrogen doped carbon dots for Bi³⁺ ion detection and temperature sensing

• Sulfur-nitrogen doped carbon dots were prepared by a simple one-step hydrothermal method. • The N,S-CDs showed exceptional fluorescence response to Bi 3+ ions and highly sensitive detection with a limit of detection of 230 nM. • N,S-CDs had a good temperature response. • The low cytotoxicity and in vitro cellular imaging properties exhibited by this carbon dot also greatly enhance their utility. In this work, sulfur-nitrogen doped carbon dots (N,S-CDs) were synthesized through a facile one-step hydrothermal approach using 2-Mercaptopyrimidine and citric acid as precursors. The as-prepared N,S-CDs exhibited a remarkable fluorescence response towards Bi³⁺ ions, achieving highly sensitive detection in the concentration range of 0-45 μM with a detection limit of 230 nM. These findings suggest great potential for the application of N,S-CDs in the detection of real water samples. Furthermore, the N,S-CDs demonstrated an excellent temperature response, showing reversible and recoverable fluorescence characteristics within the temperature range of 25 to 65 °C. The low cytotoxicity and in vitro cellular imaging properties displayed by this carbon dot further contribute to its enhanced functionality and practicality.