Graphene oxide (GO) is one of the most popular materials applied in different research areas thanks to its unique properties. The application of GO requires well-designed protocols to introduce different functionalities on its surface, exploiting the oxygenated groups already present. Due to the complex and unstable chemical environment on the GO surface, it is recommended to perform the functionalization under mild conditions. The carboxylation of GO is a widely used method to introduce additional carboxylic acids, which could be further modified through amidation or esterification reactions. The strategy already reported in the literature requires harsh conditions (excess amount of sodium hydroxide). GO is readily reduced under basic conditions, but the reduction of GO during the carboxylation is barely studied. In this work, we performed the carboxylation using chloroacetic acid with different amounts of sodium hydroxide and characterized the functionalized GO with various techniques. The carboxylated GO was exploited to develop a double functionalization approach combining an epoxide ring opening reaction and an amidation. The results showed that strong basic conditions were necessary to derivatize GO. Nevertheless, these conditions resulted in a partial reduction of GO and some functionalities on GO were removed during the reaction, thus reducing the total efficiency of the functionalization in comparison to an epoxide ring opening reaction, indicating that carboxylation is not an efficient approach for the functionalization of GO.

中文翻译：

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羧化是氧化石墨烯功能化的有效方法吗？

氧化石墨烯 (GO) 因其独特的特性而成为在不同研究领域中应用最广泛的材料之一。GO 的应用需要精心设计的协议来在其表面引入不同的功能，利用已经存在的含氧基团。由于 GO 表面化学环境复杂且不稳定，建议在温和条件下进行功能化。GO的羧化是一种广泛使用的方法来引入额外的羧酸，可以通过酰胺化或酯化反应进一步改性。文献中已经报道的策略需要苛刻的条件（过量的氢氧化钠）。GO 在碱性条件下很容易被还原，但很少研究羧化过程中 GO 的还原。在这项工作中，我们使用氯乙酸和不同量的氢氧化钠进行羧化，并用各种技术表征了功能化的 GO。羧化 GO 被用于开发一种结合环氧化物开环反应和酰胺化的双官能化方法。结果表明，衍生GO需要强碱性条件。然而，这些条件导致 GO 的部分还原，并且在反应过程中去除了 GO 上的一些官能团，因此与环氧化物开环反应相比，降低了官能化的总效率，表明羧化不是官能化的有效方法去。