Deep eutectic solvent assisted synthesis of N,Cl co-doped carbon dots using longan shell waste: Applications in antioxidant, anti-inflammatory and Fe2+ detection

Herein, by using longan shell as a precursor, deep eutectic solvent (DES) which consist of ChCl and urea (molar ration, 1:2) as the solvent and dopant, new CDs (Named as N,Cl-CDs) with good antioxidant and anti-inflammatory activities were synthesized. The chemical studies showed that N,Cl-CDs contained various functional groups (e.g. COOH, OH) and doped with N and Cl. The results of free radical scavenging activity, total antioxidant activity and KMnO4 reduction activity tests showed that N,Cl-CDs had antioxidant properties. The EC50 values were separately determined as 317.26, 302.55 and 20.82 μg/mL, respectively. Because of the good antioxidant activity, N,Cl-CDs also showed redox sensing advantage for oxidants including MnO4−, Fe3+, Cr6+ and H2O2. Moreover, the classic mouse ear edema inflammation model was further employed to explore the anti-inflammatory activity of N,Cl-CDs. Compared with the normal saline (NS) gup (67.80 %), N,Cl-CDs at high dose (1.40 mg/kg) significantly reduced the percentages of inflammation (38.13 %). Besides, due to the internal filtration effect (IFE) and static quenching, N,Cl-CDs also showed good sensitivity and selectivity for Fe2+, the limit of detection (LOD) of Fe2+ was 0.3 μM. Finally, the detection of the Fe2+ in water sample was done to test the practical application value of N,Cl-CDs, and the as-developed method showed satisfactory recoveries (92.92 %–111.03 %).