Nitrogen-doped carbon quantum dots for fluorescence sensing, anti-counterfeiting and logic gate operations

The low quantum yields (QY) of carbon quantum dots (CQDs) not only limit their sensitivity as sensors, but also hinder their application in fluorescent anti-counterfeiting materials. To develop highly fluorescent CQDs, several factors, like a large conjugated double bond system, a rigid plane structure and electron-donating substituent group incorporation on the aromatic ring need to be considered. With this in mind, herein, highly fluorescent nitrogen-doped CQDs (N-CQDs) were successfully fabricated by a solvothermal method using ammonia, citric acid and phloroglucinol as precursors. The sensing platform based on the obtained N-CQDs was constructed to determine Fe3+ and ascorbic acid (AA) via the “on–off–on” fluorescence principle. The fluorescence of the N-CQDs was effectively quenched upon addition of Fe3+, and then, restored by AA. The detection limits for Fe3+ and AA were determined to be 0.28 μM and 0.81 μM within the respective ranges of 1–10 μM and 30–90 μM. It is worth noting that the proposed strategy was successfully applied to monitor AA in fruit samples with satisfactory results. In addition, we successfully applied N-CQDs to information anti-counterfeiting and molecular logic gate operations, which confirmed their great potential application prospects.