Orange-emissive nitrogen doped carbon dots as fluorescent for rapid sensing Ag+ in food water and soil

The toxicity of silver ion (Ag + ) poses a serious threat to the environment and food safety, therefore, the accurate, economical and efficient monitoring of Ag + is crucial for protecting human health and environment. However, constructing an efficient, versatile platform that enables precise sensing of heavy metal ions remains challenging. Here, carbon dots (TN-CDs) were fabricated and optimized using p-phenylenediamine and p-toluenesulfonyl azide as precursors, with orange emission of 606 nm and quantum yield of 9.96%. The TN-CDs achieved highly sensitive, and selective detection of Ag + based on the static quenching effect, with a limit of detection (LOD) at 9.3 nM. Further, the TN-CDs extended test paper inherited the excellent sensing performance unequivocally and exhibited superior stability and accuracy with long-term storage. Thus, a smartphone-assisted strategy was developed and enabled rapid, portable Ag + detection with a convenient visual readout, accomplishing the LOD at 75.79 nM. Notably, the tests in real water samples, soil, and food samples attained excellent recoveries within 95.10–105.76%, confirming their excellent environmental tolerance and potential applicable capability. This work provided an efficient synthetic strategy for N-doped CDs with sensing capability, emphasizing their potential for application in food safety, healthcare, and environmental conservation.