Graphene can be modified by different functional groups through various transformation processes in the environment. The toxicological activity of graphene is closely related to its ability to produce reactive oxygen species (ROS), which can be altered by surface modification. Herein, unfunctionalized graphene (u-G), carboxylated graphene (G-COOH) and aminated graphene (G-NH₂) were selected to determine their ability to photogenerate ROS in the aqueous phase. Oxidative stress (ROS concentration and superoxide dismutase activity) in Daphnia magna under simulated sunlight radiation induced by the materials was also investigated. Based on density functional theory (DFT) calculations, the photochemical pathways of ROS production were identified. G-COOH and G-NH₂ produced singlet oxygen in the aqueous phase by mediating energy transfer. G-COOH, G-NH₂ and u-G generated superoxide anions and further produced hydroxyl radicals by inducing electron transfer. By comparing the biological redox potential and the lowest occupied molecular orbital values (E_LUMO) of the substances, u-G and G-COOH were identified to have the potential to induce oxidative stress. The predictive results were validated by the significant increase of oxidative stress biomarkers in Daphnia magna. By coupling experimental observations with the theoretical predictions, the results provide mechanistic insight into understanding the photochemical activity and toxicity of graphene and its surface-functionalized derivatives.

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石墨烯及其表面官能化衍生物光诱导的活性氧和氧化应激的潜在机理

石墨烯可以通过环境中的各种转化过程由不同的官能团改性。石墨烯的毒理学活性与其产生活性氧（ROS）的能力密切相关，后者可以通过表面改性来改变。在此，选择未官能化的石墨烯（uG），羧化石墨烯（G-COOH）和胺化石墨烯（G-NH ₂）以确定它们在水相中光生ROS的能力。还研究了材料诱导的模拟日光辐射下大型蚤（Daphnia magna）的氧化应激（ROS浓度和超氧化物歧化酶活性）。基于密度泛函理论（DFT）计算，确定了ROS产生的光化学途径。G-COOH和G-NH ₂通过介导能量转移在水相中产生单线态氧。G-COOH，G-NH ₂和uG产生超氧阴离子，并通过诱导电子转移进一步产生羟基自由基。通过比较该物质的生物氧化还原电势和最低占有分子轨道值（E _LUMO），确定了uG和G-COOH具有诱发氧化应激的潜力。大型蚤（Daphnia magna）的氧化应激生物标记物的明显增加证实了预测结果。通过将实验观察与理论预测相结合，结果为了解石墨烯及其表面官能化衍生物的光化学活性和毒性提供了机械上的见识。