Carbon quantum dots: green synthesis and evaluation of their photocatalytic and cytotoxicity activity

Excellent yield of carbon quantum dots (CQDs) was produced using a facile hydrothermal green chemistry method using the Caccinia macranthera plant. The synthesized CQDs were evaluated using physicochemical methods such as Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction, ultraviolet–visible, and fluorescence spectroscopy. The investigations of CQDs confirmed the spherical morphology and the size of ∼5 nm with excellent water solubility for the change in the hydrocarbon chain due to their successful hydrothermal synthesis. Four organic dyes were employed to examine the photocatalytic activity of the CQDs. The outcomes indicated that Eriochrome Black T (EBT) dye had the most photodegradation percentage in the presence of CQDs, followed by methyl orange, methylene blue, and rhodamine B. Therefore, the effects of certain factors such as pH and amount of CQDs as photocatalysts were investigated in EBT degradation. The photocatalytic mechanism of the CQDs was studied for EBT degradation using active species trapping experiments, in which OH groups were determined as the main active species. In addition, cytotoxicity assessments were conducted on the CT26 cancer cell line, which displayed a concentration-dependent behavior by way of the IC 50 at about 1000 μg/mL.