One-step synthesis of nitrogen, sulfur co-doped carbon nanodots and application for Fe³⁺ detection

Carbon nanodots (CDs) are novel forms of zero-dimensional carbonaceous nanomaterials, which have attracted the attention of researchers. Long wavelength emission decreases the interference of auto-fluorescence of tissue and can also penetrate more deeply. However, it is still a challenge to develop red emissive CDs. In this work, nitrogen, sulfur co-doped CDs are synthesized with red light emission through one-step solvothermal treatment. The as-synthesized CDs exhibit excellent properties such as high chemical stability, good biocompatibility, excellent photoluminescence properties, good water solubility, and low toxicity, and also show high sensitivity and selectivity towards Fe³⁺ sensing. The detection limit is as low as 17.3 nM. In addition, the CDs are successfully utilized for monitoring Fe³⁺ in living cells, which demonstrates their promising applicability in bioimaging. Furthermore, a test paper based on the CQDs has been prepared. This developed nanosensor can detect Fe³⁺ visually and sensitively without any further steps which will make a great contribution to the development of ion sensors.