Green synthesis of Taraxacum mongolicum Hand.-Mazz. extract-mediated copper oxide nanoparticles and evaluation of their degradation performance for organic dyes and antibacterial properties

Taraxacum mongolicum, also known as "Dandelion", distributes widely and is a famous medicinal plant with the functions of clearing heat-toxin and detumescence. In this study, we utilized the easily available T. mongolicum extract as both green reducing and capping agents for synthesizing copper oxide nanoparticles (CuO NPs), and the reaction took place in only one step and there was no need for an external chemical reducing reagents, which consequently enable the reaction process be simple, rapid, nontoxic, cost-effective, and eco-friendly. The obtained CuO NPs possess monoclinic crystal structure with high crystallinity, exhibit rough and irregular surface topography, and are close to spherical in shape with a particle size of similar to 30-50 nm. Degradation experiments demonstrated that the CuO NPs display excellent catalytic efficacy towards rhodamine-B (Rh-B) and malachite green (MG) dyes under both dark and light irradiation conditions, in particular for degrading MG, with the degradation efficiency after H2O2-assisted treatment reaching up to 93.81% under light irradiation within 210 min, and the degradation mechanism is relevant to the photo-assisted heterogeneous Fenton-like catalytic reaction. On this basis, the degradation kinetics of the CuO NPs on two selected dyes were also investigated. The cycling test indicated the good stability and reusability of the CuO NPs for dye degradation. Furthermore, the antibacterial properties of the CuO NPs were also examined. The results revealed that these nanoparticles are well capable of inhibiting the activity of Staphylococcus aureus and Escherichia coli, especially against Gram-positive bacteria, with the minimum inhibitory concentration (MIC) value of 400 mu g/ml. Overall, these findings suggest the green synthesized CuO NPs could be promising for use in the decontamination of dyes wastewater or employed in medical devices for the prevention or treatment of bacterial infections.