Green Synthesis of Red Fluorescent Carbon Quantum Dots: Antioxidant, Hemolytic, Biocompatibility, and Photocatalytic Applications.

A straightforward one-step hydrothermal method is introduced for synthesizing highly efficient red fluorescence carbon dots (R-CQDs), utilizing Heena leaf (Lawsonia inermis) powder as the carbon precursor. The resulting R-CQDs exhibit excitation at 540 nm and emission at 675 nm, a high absolute photoluminescence (PL) with quantum yield of 40% in ethanol. Various physicochemical characterization was employed to confirm successful formation of R-CQDs including UV-Vis Spectroscopy, Fourier Transform Infrared (FT-IR) Spectroscopy, X-ray diffraction Spectroscopy, Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy. The optimization of synthesis parameters including synthesis method, effect of reaction temperature, effect of reaction time and effect of reaction concentration have a significant impact on the quality and quantity of synthesized R-CQDs, as well as their properties and applications. The effect of pH and UV radiation on synthesized R-CQDs exhibited excellent photo and chemical stability. Furthermore, R-CQDs had a high ability to protect cells from hydrogen peroxide-induced damage by scavenging hydroxyl radicals.In antioxidant activity, all three methods show approximately 80% of DPPH, Fenton's reaction and KMnO scavenging activity. In hemolytic assay shows no damage or destruction of red blood cells after exposure of R-CQDs. Cell viability and angiogenesis assays confirmed the biocompatibility of the R-CQDs, indicating that they might be useful as agents for cell labelling and useful for bioimaging probe. In dye degradation activity shows highest % of dye degradation in eosin and fluorescein with approximately 80% of dye degradation by using R-CQDs.