Abstract
Antioxidants can reduce or inhibit damage such as oxidative decay caused by elevated levels of free radicals. Therefore, pursuing antioxidants with excellent properties has attracted more and more attention. Graphene quantum dots (GQDs) are considered a promising material because of their good free radical scavenging activity, low toxicity, and excellent water solubility. However, their scavenging efficiency, antioxidant mechanism, and effective control methods need to be improved. Herein, in order to further reveal the antioxidant mechanism of GQDs, the role of electrolytes in improving the antioxidant activity of GQDs is explored. In addition, 1,1-diphenyl-2-picrazine (DPPH∙), hydroxyl (∙OH), and superoxide (∙O2−) free radicals are used to evaluate the antioxidant activity of the as-prepared GQDs. Combined with transmission electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, and cyclic volt–ampere characteristic curves, the effects of an electrolytic environment on the surface functional groups, charge transfer capability, and defect states of GQDs are obtained. The antioxidant mechanism of GQDs and how to improve their antioxidant activity are further elucidated.
Highlights
Reactive oxygen species (ROS), including free radicals such as hydroxyl (·OH), superoxide (·O2−), alkoxy (RO·), and peroxide (ROO·), are byproducts of cellular redox processes
There is no significant difference in shape or size of the samples, indicating that the three electrolytes have similar effects on Graphene quantum dots (GQDs) formation
As the reaction time increases, the absorption peaks of different GQDs near 515 nm gradually decrease, which suggests that all three GQDs have a certain antioxidant activity, but the type of electrolyte affects the antioxidant activity
Summary
Reactive oxygen species (ROS), including free radicals such as hydroxyl (·OH), superoxide (·O2−), alkoxy (RO·), and peroxide (ROO·), are byproducts of cellular redox processes. ROS play a dual role in biological systems. If they remain at a proper level, they are involved in a variety of physiological effects and many cellular signaling processes. When they are in an excessive amount, they can have deleterious effects on biological systems [5,6], such as destroying the DNA, proteins, and lipids of living organisms, leading to various inflammations and diseases [7]. Antioxidants can eliminate ROS or reduce them to a proper level, maintaining normal function of biological systems and alleviating the development of disease. Interaction between antioxidants and ROS is mainly by hydrogen atom transfer (HAT), single electron transfer (SET), and transition metal chelation [8,9]
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