Danushika Gimhani, Yap Pei Lay, Losic Dusan
School of Chemical Engineering, The University of Adelaide, Adelaide 5005, South Australia, Australia.
Anal Chem. 2024 Dec 10;96(49):19339-19347. doi: 10.1021/acs.analchem.4c03286. Epub 2024 Dec 1.
Graphene oxide (GO), having diverse oxygen functional groups, including carboxyl, hydroxyl, carbonyl, and epoxy groups, is a significant graphene-related 2D material (GR2M) essential for various applications. The quantification of these functional groups traditionally utilizes Boehm acid titration, which, however, does not account for epoxy groups crucial for these applications. Presently, there exists no analytical method enabling quantitative assessment of the concentration of epoxy groups in GO available in the market in different forms such as powders, pastes, and dispersions. This paper presents a new approach employing catalyst-assisted acid-water-based titration to quantify epoxy groups in GO materials. The method's efficacy was validated using a well-characterized reference GO sample and tested on commercially produced GO powders, yielding epoxy group concentrations ranging from 1.15 ± 0.047 to 1.37 ± 0.051 mmol/g with high precision and reproducibility. The method introduces two new quality parameters, including the epoxide index (EI) and the equivalent epoxide weight (EEW) not implemented for GO before. Control measurements with a commercial epoxide material of known epoxide content demonstrated excellent agreement by using the proposed approach. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used for comparative characterizations of epoxide groups in GO samples during titrations.
氧化石墨烯（GO）具有多种氧官能团，包括羧基、羟基、羰基和环氧基，是一种重要的与石墨烯相关的二维材料（GR2M），在各种应用中至关重要。传统上，这些官能团的定量分析采用 Boehm 酸滴定法，然而，该方法并未考虑到对这些应用至关重要的环氧基。目前，市场上不存在能够对不同形式（如粉末、糊剂和分散体）的 GO 中的环氧基浓度进行定量评估的分析方法。本文提出了一种采用催化剂辅助的酸水基滴定法来定量分析 GO 材料中环氧基的新方法。该方法的有效性通过使用一个经过充分表征的参考 GO 样品进行了验证，并在商业生产的 GO 粉末上进行了测试，得到的环氧基浓度范围为 1.15±0.047 至 1.37±0.051 mmol/g，具有高精度和可重复性。该方法引入了两个新的质量参数，包括环氧指数（EI）和等效环氧重量（EEW），这两个参数以前未在 GO 中使用过。使用已知环氧含量的商业环氧化合物材料进行的对照测量表明，采用所提出的方法具有极好的一致性。在滴定过程中，使用傅里叶变换红外光谱（FTIR）和 X 射线光电子能谱（XPS）对 GO 样品中的环氧基进行了对比表征。
