Aqueous Liquid Crystals of Graphene Oxide

被引:589
作者
Xu, Zhen [1 ]
Gao, Chao [1 ]
机构
[1] Zhejiang Univ, Dept Polymer Sci & Engn, MOE Key Lab Macromol Synth & Functionalizat, Hangzhou 310027, Zhejiang, Peoples R China
基金
高等学校博士学科点专项科研基金; 中国国家自然科学基金;
关键词
graphene oxide; phase transition; nematic; liquid crystal; orientational ordering; CARBON NANOTUBES; DISPERSIONS; SUSPENSIONS; GRAPHITE; SHEETS; FILMS;
D O I
10.1021/nn200069w
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The formation of liquid crystals.(LCs) is the most viable approach to produce macroscopic, periodic self-assembled materials from oriented graphene sheets. Herein, we have discovered that well-soluble and single-layered graphene oxide (GO) sheets can exhibit nematic liquid crystallinity in water and first established their isotropic-nematic solid rase diagram versus mass fraction and salt concentration. The zeta potential of GO dispersion is around -64 mV, and its absolute value decreases with increasing salt concentration, implying that the electrostatic repulsive force between negatively charged GO sheets is the dominant interaction in the system of GO LCs and also explaining the salt-dependent phase behavior. For single-layer GO sheets with average diameter of 2.1 mu m and polydispersity index of 83%, the isotropic-nematic phase transition occurs at a mass concentration of similar to 0.025%, and a stable nematic phase forms at similar to 0.5%. Rheological measurements showed that GO aqueous dispersions performed as typical shear flows and confirmed the Isotropic-nematic transition. The ordering of GO sheets In aqueous dispersions and the solid state is demonstrated by the characterizations of polarized-light optical microscopy, small-angle X-ray scattering, scanning electron microscopy, and transmission electron microscopy. The direct, real-time fluorescent inspections by confocal laser microscopy further reveal that the individually dispersed fluorescent GO sheets align with orientational directions along their long axes. These novel findings shed light on the phase behaviors of diversely topological graphenes and lay the foundation for fabrication of long-range, ordered, nano-objects and macroscopically assembled graphene-based functional materials.
引用
收藏
页码:2908 / 2915
页数:8
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