Wang Zhenzhen, Lu Zhanghui, Zhao Yuliang, Gao Xingfa
Jiangxi Inorganic Membrane Materials Engineering Research Centre, College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang, 330022, China.
Nanoscale. 2015 Feb 21;7(7):2914-25. doi: 10.1039/c4nr06633b.
Water-solubilization is the prerequisite to endow the pristinely hydrophobic fullerenes with biocompatibility and biofunctionality, which has been widely applied to derive fullerene-based nanomaterials for biomedical applications. Oxidation reactions using O2 and H2O2 are the most commonly used approaches to this end, through which fullerenols with different structural features can be obtained. Despite the progress in the syntheses and bioapplications of fullerenols, their formation mechanisms and structures at the atomic level, which substantialize their physical properties and biofunctions, have been little understood. Using density functional theory calculations, we comparatively study the mechanisms and product structures for the oxidations of C60, Gd@C60 and Gd@C82 using both O2 and H2O2 as oxidizing agents under both neutral and alkaline aqueous conditions. We predict the formation mechanisms and product structures corresponding to the different synthetic conditions. Briefly, the H2O2 oxidations of C60, Gd@C60 and Gd@C82 under neutral conditions do not occur readily at room temperature because of the high energy barriers, whereas the H2O2 oxidations can readily proceed under alkaline conditions. The oxygen-containing groups of the fullerenols obtained under these conditions include hydroxyl, carbonyl, hemiacetal and deprotonated vic-diol. In contrast, through O2 oxidation under alkaline conditions, the most probable oxygen-containing groups for C60 fullerenols are epoxide and deprotonated vic-diol, and those for Gd@C60 and Gd@C82 fullerenols are hydroxyls and carbonyls. The results explain a wide range of experimental findings reported before. More importantly, they provide atomistic-level insights into the formation mechanisms and structures for various fullerenols, which are of fundamental interest for understanding their biomedical applications in the future.
水溶性是赋予原本疏水的富勒烯生物相容性和生物功能性的前提条件，这已被广泛应用于制备用于生物医学应用的富勒烯基纳米材料。使用氧气和过氧化氢的氧化反应是实现这一目标最常用的方法，通过这些反应可以获得具有不同结构特征的富勒醇。尽管富勒醇在合成和生物应用方面取得了进展，但它们在原子水平上的形成机制和结构，即决定其物理性质和生物功能的关键因素，却鲜为人知。利用密度泛函理论计算，我们比较研究了在中性和碱性水溶液条件下，以氧气和过氧化氢作为氧化剂时，C60、Gd@C60和Gd@C82氧化的反应机制和产物结构。我们预测了对应于不同合成条件的形成机制和产物结构。简而言之，由于高能垒，C60、Gd@C60和Gd@C82在中性条件下的过氧化氢氧化在室温下不容易发生，而在碱性条件下过氧化氢氧化可以很容易地进行。在这些条件下获得的富勒醇的含氧基团包括羟基、羰基、半缩醛和去质子化的邻二醇。相比之下，在碱性条件下通过氧气氧化，C60富勒醇最可能的含氧基团是环氧化物和去质子化的邻二醇，而Gd@C60和Gd@C82富勒醇的含氧基团是羟基和羰基。这些结果解释了之前报道的一系列实验结果。更重要的是，它们为各种富勒醇的形成机制和结构提供了原子层面的见解，这对于理解它们未来的生物医学应用具有重要的基础意义。
