Free radicals and their induced oxidative damage in living organisms are related to many diseases. Natural substances with antioxidant capacity are effective in scavenging free radicals, which could slow down aging and prevent diseases. However, the existing methods for the evaluation of antioxidant activity mostly required the use of complex instruments and operations. In this work, we proposed a unique method to determine the total antioxidant capacity (TAC) in real samples through a photosensitization-mediated oxidation system. N- and P-doped long-lived phosphorescent carbon dots (NPCDs) were developed, which exhibited the effective intersystem crossing from the singlet to the triplet state under UV light irradiation. Mechanism study confirmed that the energy of excited triplet state in NPCDs generated superoxide radicals and singlet oxygen through type I and type II photoreactions, respectively. On this basis, the quantitative determination of TAC in fresh fruits was achieved using 3,3′,5,5′-tetramethylbenzidine (TMB) as a chromogenic bridge in the photosensitization-mediated oxidation system. This demonstration will not only provide a facile way to analyze antioxidant capacity in practical samples but also broaden the applications of phosphorescent carbon dots.

中文翻译：

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长寿命磷光碳点作为总抗氧化能力测定的光敏剂

自由基及其在生物体中引起的氧化损伤与许多疾病有关。具有抗氧化能力的天然物质能有效清除自由基，延缓衰老，预防疾病。然而，现有的抗氧化活性评价方法大多需要使用复杂的仪器和操作。在这项工作中，我们提出了一种独特的方法，通过光敏介导的氧化系统来确定实际样品中的总抗氧化能力 (TAC)。开发了 N 和 P 掺杂的长寿命磷光碳点 (NPCD)，其在紫外光照射下表现出从单线态到三线态的有效系间跨越。机理研究证实，NPCDs 中激发的三重态能量分别通过 I 型和 II 型光反应产生超氧自由基和单线态氧。在此基础上，采用3,3',5,5'-四甲基联苯胺(TMB)作为光敏介导氧化体系中的显色桥，实现了新鲜水果中TAC的定量测定。该演示不仅提供了一种简便的方法来分析实际样品中的抗氧化能力，而且拓宽了磷光碳点的应用。