Abstract Graphene oxides (GO) of highly polydisperse size distribution were prepared by the Brodie method and their dispersion stability was characterized. Exfoliation and fractionation led to well-defined particle populations in the Nano, classical Colloidal (submicron) and Micrometer size ranges, as revealed by atomic force microscopy and light scattering measurements. Time-resolved dynamic light scattering experiments revealed that aggregation processes are fully impeded in the intermediate pH regime of 3–13 in the absence of electrolytes. While the resistance against salt-induced aggregation increases with the pH due to the progressive ionization of the surface functional groups of GO sheets, their dispersions are inherently unstable at supramillimolar concentrations of strong acids and submolar concentrations of bases, in line with the DLVO theory. However, the aggregation behavior quantified by the critical coagulation concentrations (CCCs) shows surprisingly substantial platelet size dependence. The CCC of Nano Brodie-GO reaches 360 m m at pH = 12, which is one of the highest values ever reported for GO aqueous dispersions. These results provide useful quantitative information to design processable GO dispersions of pH- and size-tunable stability for future applications.

中文翻译：

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氧化石墨烯的尺寸依赖性聚集

摘要 采用Brodie法制备了高度多分散尺寸分布的氧化石墨烯（GO），并对其分散稳定性进行了表征。正如原子力显微镜和光散射测量所揭示的那样，剥离和分馏导致在纳米、经典胶体（亚微米）和微米尺寸范围内形成明确的粒子群。时间分辨动态光散射实验表明，在没有电解质的情况下，在 3-13 的中间 pH 范围内，聚集过程完全受阻。虽然由于 GO 片表面官能团的逐渐电离，对盐诱导聚集的抵抗力随着 pH 值的增加而增加，但它们的分散体在超毫摩尔浓度的强酸和亚摩尔浓度的碱下本质上是不稳定的，符合DLVO理论。然而，由临界凝血浓度 (CCC) 量化的聚集行为显示出惊人的血小板大小依赖性。Nano Brodie-GO 的 CCC 在 pH = 12 时达到 360 mm，这是 GO 水分散体有史以来报告的最高值之​​一。这些结果为设计具有 pH 和尺寸可调稳定性的可加工 GO 分散体提供了有用的定量信息，以供未来应用使用。