Understanding Aqueous Dispersibility of Graphene Oxide and Reduced Graphene Oxide through pKa Measurements
Understanding Aqueous Dispersibility of Graphene Oxide and Reduced Graphene Oxide through pKa Measurements
复制标题
DOI：
10.1021/jz300236w
复制
发表时间：
2012-04-05
影响因子：
5.7
通讯作者：
Vasudevan, Sukumaran
中科院分区：
文献类型：
--
作者：
Konkena, Bharathi;Vasudevan, Sukumaran
氧化石墨烯（GO）和还原的氧化石墨烯（r-GO）的水溶性氧化的化学基础是用于制备可加工的石墨烯片的溶液加工技术的设计中的关键考虑。在这里，我们使用zeta电位测量，pH滴定，和红外光谱法，以建立在不同的pH值的GO和r-GO片的水溶性的化学基础。我们表明，r-GO片具有可电离的基团与一个单一的pK值（8.0），而GO片具有更酸性的基团（pK = 4.3），除了与6.6和9.0的pK值的组。红外光谱已被用来跟踪电离事件的顺序。在GO和r-GO片层中，羧基的电离是电荷积累的主要原因，但在GO片层上，紧邻羧基的酚基和羟基的存在通过稳定羧酸根阴离子降低了pK（a）值，导致上级水溶性。
The chemistry underlying the aqueous dispersibility of graphene oxide (GO) and reduced graphene oxide (r-GO) is a key consideration in the design of solution processing techniques for the preparation of processable graphene sheets. Here, we use zeta potential measurements, pH titrations, and infrared spectroscopy to establish the chemistry underlying the aqueous dispersibility of GO and r-GO sheets at different values of pH. We show that r-GO sheets have ionizable groups with a single pK value (8.0) while GO sheets have groups that are more acidic (pK = 4.3), in addition to groups with pK values of 6.6 and 9.0. Infrared spectroscopy has been used to follow the sequence of ionization events. In both GO and r-GO sheets, it is ionization of the carboxylic groups that is primarily responsible for the build up of charge, but on GO sheets, the presence of phenolic and hydroxyl groups in close proximity to the carboxylic groups lowers the pK(a) value by stabilizing the carboxylate anion, resulting in superior water dispersibility.