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 (Mn2+ ) through static quenching effect and subsequently restored by NAC via the combination with Mn2+ due to the coordination effect. Therefore, the fluorescent turn-on sensing of NAC was actuated based on the fluorescence quenching stimulated by Mn2+ 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-1 and the detection limit was 0.03 mmol L-1 . 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 Mn2+ was used to construct a fluorescent nanoprobe for NAC. Compared with other heavy metal ions, Mn2+ 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.

Multiple fluorescence quenching effects mediated fluorescent sensing of captopril Based on amino Acids-Derivative carbon nanodots.

Carbon nanodots (CNDs) were facilely synthesized through a pyrolysis procedure with histamine, an amino acid rich in element carbon and nitrogen, being the precursor. Taking advantage of the favorable fluorescence performance of CNDs, a multiple fluorescence quenching effects mediated fluorescent sensor was established for captopril (CAP) detection. MnO2 NPs were firstly combined with CNDs via electrostatic attraction and subsequently quenched the fluorescence. The quenching mechanisms were concluded to be the combined effects of fluorescence resonance energy transfer (FRET) and inner filtration effect (IFE). Subsequently CAP triggered a unique redox reaction and decomposed the quencher so that renewed the fluorescence. Hence, the sensitive and selective detection of CAP was achieved through the indication of fluorescence recovery efficiency. A proportional range of 0.4 âˆ¼ 60 µmol L-1 with the LOD of 0.31 µmol L-1 was obtained. The sensor was further applied to the real sample detection and the satisfactory results revealed the practical value of CNDs. The facile synthesis of CNDs and brand-new sensing mechanism made it a novel fluorescent method and could improve the analysis of CAP.