Metal ion-mediated carbon dot nanoprobe for fluorescent turn-on sensing of N-acetyl-l-cysteine.

In this work, carbon dots (CDs) was easily synthesized from aspartic acid through a pyrolysis method. Based on their favourable fluorescence properties, CDs were utilized to design a metal ion-mediated fluorescent probe for N-acetyl-l-cysteine (NAC) detection. The fluorescence intensity of CDs was firstly quenched by manganese ions (Mn ) through static quenching effect and subsequently restored by NAC via the combination with Mn due to the coordination effect. Therefore, the fluorescent turn-on sensing of NAC was actuated based on the fluorescence quenching stimulated by Mn and recovery induced by coordination. The fluorescence recovery efficiencies showed a proportional range to the concentration of NAC in the range 0.04-5 mmol L and the detection limit was 0.03 mmol L . Furthermore, this metal ion-mediated fluorescent nanoprobe was applied to human urine sample detection and the standard recovery rates were located in the range 97.62-102.34%. This was the first time that Mn was used to construct a fluorescent nanoprobe for NAC. Compared with other heavy metal ions, Mn with good biosecurity prevented the risk of application, which made the nanoprobe green and biopractical. The facile synthesis of CDs and novel metal ion-mediated sensing mode made it a promising method for pharmaceutical analysis.