Graphene and Other 2D Colloids: Liquid Crystals and Macroscopic Fibers

Abstract

Two-dimensional colloidal nanomaterials are running into renaissance after the enlightening researches of graphene. Macroscopic one-dimensional fiber is an optimal ordered structural form to express the in-plane merits of 2D nanomaterials, and the formation of liquid crystals (LCs) allows the creation of continuous fibers. In the correlated system from LCs to fibers, understanding their macroscopic organizing behavior and transforming them into new solid fibers is greatly significant for applications. Herein, we retrospect the history of 2D colloids and discuss about the concept of 2D nanomaterial fibers in the context of LCs, elaborating the motivation, principle and possible strategies of fabrication. Then we highlight the creation, development and typical applications of graphene fibers. Additionally, the latest advances of other 2D nanomaterial fibers are also summarized. Finally, conclusions, challenges and perspectives are provided to show great expectations of better and more fibrous materials of 2D nanomaterials. This review gives a comprehensive retrospect of the past century-long effort about the whole development of 2D colloids, and plots a clear roadmap - "lamellar solid - LCs - macroscopic fibers - flexible devices", which will certainly open a new era of structural-multifunctional application for the conventional 2D colloids.

Depletion-driven four-phase coexistences in discotic systems

“…It has been experimentally observed how addition of non-adsorbing polymers [39][40][41] or small spheres [42][43][44][45][46][47][48][49] to a colloidal platelet suspension enriches the phase behaviour. For a review, see [50].…”

Charged Carbon Nanomaterials: Redox Chemistries of Fullerenes, Carbon Nanotubes, and Graphenes

“…LC phases provide an attractive route to improve the alignment and packing of nanomaterials, in order to exploit anisotropic properties effectively. LCs of uncharged SWCNTs 416 and graphene 417 dispersions have been reviewed previously. Such systems are very effective for fiber and ordered film production in a wide range of contexts; applications of CCN-derived LCs are covered in section 8.…”

Large Graphene Oxide Flakes: From Isotopic to Nematic Liquid Crystal Phase Transition

“…This gives an aspect ratio AR = D / T higher than 1000, which is a very high value compared with the known lyotropic LCs, resulting in a very low threshold for the LC phase formation . According to Onsager's theory for disk‐like colloids, the high AR of GO flakes led to GO LC phase formation at low concentrations due to the overlap of their excluded volumes . The theory predicts that the transition from isotropic to nematic phase occurs sharply above a threshold volume fraction of disks, proportional to the inverse of the AR.…”

“…[1,9] According to Onsager's theory for disk-like colloids, the high AR of GO flakes led to GO LC phase formation at low concentrations due to the overlap of their excluded volumes. [10] The theory predicts that the transition from isotropic to nematic phase occurs sharply above a threshold volume fraction of disks, proportional to the inverse of the AR. This type of phase transition, driven by increase in the concentration of the dispersed particles in water, is characteristic of lyotropic LC systems.…”