Stathi Panagiota, Gournis Dimitrios, Deligiannakis Yiannis, Rudolf Petra
Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, NL-9747AG Groningen, The Netherlands.
Department of Material Science and Engineering, University of Ioannina , GR-45110 Ioannina, Greece.
Langmuir. 2015 Sep 29;31(38):10508-16. doi: 10.1021/acs.langmuir.5b01248. Epub 2015 Sep 14.
A graphene oxide-gallic acid hybrid material was synthesized by the immobilization of gallic acid (3,4,5-trihydroxobenzoic acid) on graphene oxide. The grafting was achieved via the formation of amide bonds between the amine groups on the organofunctionalized graphite oxide surface and the carboxyl groups of the gallic acid molecules. The EPR signal of the gallic acid radicals in this hybrid material remained almost unaltered over at least 500 days, with less than 3% signal decay over that period, pointing to the truly remarkable stability of these radicals. The produced material was characterized by Fourier transform infrared, X-ray photoelectron, and electron paramagnetic resonance spectroscopies as well as by thermogravimetric analysis and the Kaiser test. The stability of the radicals in the material was studied in powder form and in aqueous solution vs pH. We demonstrate that in the graphene oxide-gallic acid hybrid material a radical is favorably stabilized on the ring-O while the oxidation of the second OH is precluded, and this results in long-term stabilization of the gallic acid radicals in solid hybrid material. Thus, in applications where it will be used under O2-free and humidity-free conditions, the graphene oxide-gallic acid hybrid material is a reliable spintronics scaffold.
通过将没食子酸（3,4,5-三羟基苯甲酸）固定在氧化石墨烯上合成了一种氧化石墨烯-没食子酸杂化材料。接枝是通过在有机功能化氧化石墨表面的胺基与没食子酸分子的羧基之间形成酰胺键来实现的。这种杂化材料中没食子酸自由基的电子顺磁共振（EPR）信号在至少500天内几乎保持不变，在此期间信号衰减小于3%，这表明这些自由基具有真正显著的稳定性。所制备的材料通过傅里叶变换红外光谱、X射线光电子能谱、电子顺磁共振光谱以及热重分析和凯泽测试进行了表征。研究了该材料中自由基在粉末形式和水溶液中随pH值的稳定性。我们证明，在氧化石墨烯-没食子酸杂化材料中，一个自由基在环-O上得到了有利的稳定，同时第二个OH的氧化被阻止，这导致了没食子酸自由基在固体杂化材料中的长期稳定。因此，在无氧气和无湿度条件下使用的应用中，氧化石墨烯-没食子酸杂化材料是一种可靠的自旋电子学支架。
