Potential Application of Nitrogen-Doped Carbon Quantum Dots Synthesized by a Solvothermal Method for Detecting Silver Ions in Food Packaging

In this paper, nitrogen-doped carbon quantum dots (N-CQDs) were synthesized by a solvothermal method using 1,2,4-triaminobenzene as a carbon precursor. The surface of the synthesized N-CQDs was modified with amino functional groups. The results indicated that N-CQDs had various N-related functional groups and chemical bonds and were amorphous in structure. At the same time, the quantum yield of N-CQDs was 5.11%, and the average lifetime of fluorescence decay was 5.79 ns. The synthesized N-CQDs showed good selectivity for and sensitivity to Ag(+). A linear relationship between N-CQDs detection efficiency and Ag(+) concentration was observed for concentration ranges of Ag(+) corresponding to 0–10 μM and 10–30 μM. In addition, N-CQDs were used for the detection of trace Ag(+) in food packaging material. The silver ion content of the sample determined by the N-CQDs detection method was 1.442 mg/L, with a relative error of 6.24% with respect to flame atomic absorption spectrometry, according to which the Ag(+) content was 1.352 mg/L. This indicates that the N-CQDs detection method is reliable. Therefore, the N-CQDs prepared in this paper can detect Ag(+) rapidly, simply, and sensitively and are expected to be a promising tool for the detection of trace Ag(+) in food packaging materials.