Ecofriendly hydrothermal synthesis of lemon peel derived multifunctional carbon quantum dots for biomedical and environmental sensing applications

In this study, carbon quantum dots were synthesized from lemon peel waste (LPCQDs) and were characterized by using UV-vis spectroscopy, FT-IR, HR-TEM, FE-SEM, DLS, ELS, fluorescence lifetime, quantum yield analysis, Raman spectroscopy, in-vitro cytotoxicity, and CHNS analysis. The average size of the LPCQDs synthesised in this study was 2.75 nm, with a quantum yield of 7.4% and a lifetime of 4.48 ns. In addition, the LPCQDs exhibited significant antimicrobial properties against a broad spectrum of clinical pathogens with a zone of inhibition up to 28 mm, an MIC value of 0.94 mg mL- 1 and biofilm inhibition of up to 81.72 ± 1.4%. The LPCQDs also resulted in the 96.07 ± 2.8% inhibition of protein denaturation, indicating a remarkable potential for anti-inflammatory applications. Further, LPCQDs demonstrated significant antidiabetic activity by inhibiting the activity of α-amylase by 65.8 ± 5.85%. The cytotoxicity assay results demonstrated promising biocompatibility of LPCQDs at concentrations up to 10 µg mL- 1. The LPCQDs also exhibited blue fluorescence under UV irradiation and exhibited fluorescence quenching in the presence of mercury and lead ions at concentrations as low as 700 µM, highlighting their suitability in metal ion detection systems.