Environmental photochemistry of single layered graphene oxide in water
Environmental photochemistry of single layered graphene oxide in water
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DOI：
10.1039/c4en00209a
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发表时间：
2015-04
期刊：
影响因子：
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通讯作者：
Yingcan Zhao;C. Jafvert
中科院分区：
文献类型：
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作者：
Yingcan Zhao;C. Jafvert
氧化石墨烯（GO）是一种碳质纳米材料，是制备石墨烯的前体材料，由于其独特的性质，它可能会在未来用于许多工业和消费产品。尽管它的名字，它含有许多环氧，羟基和羧基官能团在其边缘和表面，使其易于悬浮在水中。然而，它是如何在自然水生环境中转化或矿化的，以及它对这些环境中自然过程的影响在很大程度上仍然未知。因此，在这项研究中，我们报告了分散在水中的单层GO的光化学反应性，并用到达地球表面水体的太阳光谱内的光（λ ≥ 300 nm）照射。照射后，5 mg L−1 GO悬浮液的可见颜色从淡褐色变为深棕色，可能表明部分π键结构得到修复;然而，拉曼光谱表明非芳香族缺陷增加。为了进一步检查GO表面的氧化或还原如何在太阳光照射时发生，我们探测了各种活性氧物质（ROS）的产生。通过使用选择性和高反应性化学探针监测ROS的产生，检测到超氧阴离子（O2 stec −）的形成，但未检测到单氧（1 O2）或羟基自由基（·OH），表明电子从GO转移到溶解的分子氧（O2）。然而，通过O2 ste −还原的进一步电子转移确实发生了，因为发现过氧化氢（H2 O2）积累，在照射4小时后在5 mg L−1 GO的悬浮液中形成3 μM H2 O2。
Graphene oxide (GO) is a carbonaceous nanomaterial that is a precursor material in the preparation of graphene, and because of its unique properties, it will likely be used in a number of industrial and consumer products in the future. Despite its name, it contains many epoxy, hydroxyl, and carboxyl functional groups on its edges and surface, making it easy to suspend in water. However, how it is transformed or mineralized in natural aquatic environments and its effects on natural processes within these environments remain largely unknown. Therefore, in this study, we report on the photochemical reactivity of single layered GO dispersed in water and irradiated with light within the solar spectrum that reaches the water bodies at the earth's surface (λ ≥ 300 nm). Upon irradiation, the visible color of a 5 mg L−1 GO suspension shifted from pale to dark brown, possibly indicating the repair of some of the π-bond structures; however, Raman spectroscopy indicated an increase in nonaromatic defects. To further examine how oxidation or reduction of the GO surface may occur upon solar light irradiation, we probed the production of various reactive oxygen species (ROS). By monitoring ROS production with selective and highly reactive chemical probes, formation of superoxide anions (O2˙−), but not single oxygen (1O2) or hydroxyl radicals (·OH), was detected, indicating electron transfer from GO to dissolved molecular oxygen (O2). However, further electron transfer through reduction of O2˙− did occur, as hydrogen peroxide (H2O2) was found to accumulate, forming 3 μM H2O2 in a suspension of 5 mg L−1 GO after 4 hours of irradiation.