Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.
J Am Chem Soc. 2010 Dec 22;132(50):17667-9. doi: 10.1021/ja1078943. Epub 2010 Nov 24.
Graphene oxide (GO) nanocolloids-sheets with lateral dimension smaller than 100 nm-were synthesized by chemical exfoliation of graphite nanofibers, in which the graphene planes are coin-stacked along the length of the nanofibers. Since the upper size limit is predetermined by the diameter of the nanofiber precursor, the size distribution of the GO nanosheets is much more uniform than that of common GO synthesized from graphite powders. The size can be further tuned by the oxidation time. Compared to the micrometer-sized, regular GO sheets, nano GO has very similar spectroscopic characteristics and chemical properties but very different solution properties, such as surface activity and colloidal stability. Due to higher charge density originating from their higher edge-to-area ratios, aqueous GO nanocolloids are significantly more stable. Dispersions of GO nanocolloids can sustain high-speed centrifugation and remain stable even after chemical reduction, which would result in aggregates for regular GO. Therefore, nano GO can act as a better dispersing agent for insoluble materials (e.g., carbon nanotubes) in water, creating a more stable colloidal dispersion.
氧化石墨烯（GO）纳米片的横向尺寸小于 100nm，通过化学剥离石墨纳米纤维合成，其中的石墨烯片沿纳米纤维的长度叠合在一起。由于上尺寸限制由纳米纤维前体的直径预先确定，因此 GO 纳米片的尺寸分布比通常由石墨粉末合成的 GO 更为均匀。通过氧化时间可以进一步调整尺寸。与微米级的规则 GO 片相比，纳米 GO 具有非常相似的光谱特性和化学性质，但溶液性质却大不相同，例如表面活性和胶体稳定性。由于更高的边缘与面积比，它们具有更高的电荷密度，因此水性 GO 纳米胶体更加稳定。GO 纳米胶体的分散体可以承受高速离心，即使经过化学还原后也能保持稳定，而对于规则 GO，则会导致团聚。因此，纳米 GO 可以作为水中不溶性物质（例如碳纳米管）的更好分散剂，形成更稳定的胶体分散体。
