A dual-signal sensing platform based on NCl-CQDs/DCIP fluorescence and colorimetry for the rapid detection of AA

In this study, a novel nitrogen-chlorine-codoped carbon quantum dots (NCl-CQDs) with low toxicity, thermal stability, good fluorescence properties, biocompatibility and high sensitivity was successfully prepared by hydrothermal carbonization. Based on the above advantages of NCl-CQDs, the NCl-CQDs was used to construct fluorescence sensing system for fluorescence probes. The maximum fluorescence emission wavelength was obtained at 470 nm when the excitation wavelength was 390 nm. The fluorescence signal was in the state of “ON”. The introduction of 2,6-Dichloroindophenol Sodium (DCIP) resulted in the quenching of fluorescence intensity due to photoinduced electron transfer between DCIP and NCl-CQDs. At this point, the color of the solution changed from brownish-yellow to light blue, indicating that the fluorescence signal was in an “OFF” state. Upon addition of ascorbic acid (AA) to the NCl-CQDs/DCIP system, the corresponding fluorescence signal was restored due to the special interaction between AA and DCIP. The color of the corresponding solution changed from light blue to colorless. The fluorescence signal was in the “on” state. Therefore, an “ON-OFF-ON” sensing system and colorimetric sensing system for AA was constructed using the NCl-CQD fluorescence probe. Under the optimized experimental conditions, the proposed methods exhibited satisfactory linear ranges. Specifically, the linear range for AA detection by the fluorescence sensor spanned from 1.2 μM to 180.33 μM, while that by the colorimetric sensor ranged from 1.32 μM to 166.55 μM. The corresponding detection limits were determined to be 0.68 μM and 0.55 μM, respectively. In summary, this sensing system could effectively enhance selectivity, sensitivity, and accuracy by preventing false positive detection results caused by environmental and system errors.