Nitrogen and Sulfur co-Doped Carbon Quantum Dots for Accurate Detection of pH in Gastric Juice

Nitrogen-sulfur co-doped carbon quantum dots with blue light, good water solubility, strong stability and high quantum yield(36. 23%) , were synthesized by one-step hydrothermal method , using salicylic acid and thiourea as raw materials. Under the excitation of 302 nm, there is a good linear relationship between the fluorescence intensity and the pH value in the range of 2. 01-5. 11 at the emission wavelength of 409 nm, and the correlation coefficient is 0. 9931. The change of pH value in gastric juice can be detected in situ and in real time. In view of the fact that the pH value of gastric juice is closely related to the diagnosis of gastric cancer and neonatal monitoring, N, S-CQDs are expected to contribute to the early diagnosis of gastric cancer and neonatal health protection. N, S-CQDs have low cytotoxicity and good biocompatibility. When microcystis aeruginosa cells as phytoplankton model are incubated with 400 mu g/mL of N , S-CQDs for 48 h , their survival ratesare 82. 8% , indicating that N , S-CQDs could be used as a environmental-friendly fluorescent probe for human gastric cells.