Mechanically Strong, Electrically Conductive, and Biocompatible Graphene Paper

Abstract

Research on graphene was originally motivated by its peculiar electrical transport properties and the promise of future applications in nanoelectronics. [1,2] Graphene sheets, owing to their exceptional thermal and mechanical properties and high electrical conductivity, are also of great interest to serve as new nanoscale building blocks to create unique macroscopic materials. [3][4][5] Recent studies have shown that graphene sheets can be prepared in large quantity through chemical conversion from graphite, [6][7][8][9][10][11][12] which has facilitated the fabrication of graphene-based electronic devices [13,14] and has also made it possible to create new bulk materials comprising graphene sheets for a broader range of applications. [3][4][5]15,16] For example, it has been recently demonstrated that chemically modified graphene sheets can be dispersed throughout a polymeric [3] or inorganic matrix [15] to make electrically conducting composites with a percolation threshold as low as 0.1 vol %. Thin graphene films have also been used as potential transparent electrodes for solar cells. [16] More recently, Ruoff and co-workers have demonstrated that graphene oxide (GO) sheets dispersed in water can be assembled into a well-ordered structure under a directional flow, yielding ultrastrong GO paper.[4] GO paper is superior to many other paperlike materials in stiffness and strength, however, a lack of electrical conductivity limits its use. Although GO paper can be rendered conductive by thermal annealing, the structure and mechanical properties seriously deteriorate after this treatment (see below for further discussion). We have recently demonstrated that aqueous dispersions of graphene sheets can be readily produced without the need for polymeric or surfactant stabilizers. [12] This has enabled us to prepare electrically conductive graphene paper directly, using the same strategy that has been used to make carbon nanotube buckypaper and GO papers. [4,17,18] Here, we demonstrate that the resulting graphene paper displays a remarkable combination of thermal, mechanical, and electrical properties, whilst preliminary cytotoxicity tests suggest biocompatibility, making this new material attractive for many potential applications. Graphene dispersions were prepared by controlled reduction of GO dispersions with hydrazine using the procedure reported in one of our recent publications.[12] Graphene paper was then fabricated by filtration of a measured amount of graphene dispersion through an Anodisc membrane filter, followed by air drying and peeling from the filter. The samples of graphene paper were annealed at different temperatures before being cooled to room temperature for various measurements (see the Experimental section for details).We observe that as-prepared graphene paper displays a shiny metallic luster on both sides (Fig. 1A). Scanning electron microscopy (SEM) analysis reveals that the surface of the graphene paper is quite smooth (Fig. 1B) and the fracture edges of the papers exhibit a layered structure ...

Biomimetic superelastic graphene-based cellular monoliths

“…High-resolution transmission electron microscopy (HRTEM) analysis (Fig. 2a) revealed that the graphene sheets in the cell wall are well oriented in a nearly parallel manner, similar to the layered structure observed in the ultrastrong graphene paper prepared under the directional flow 35,36 .…”

Chemically converted graphene: scalable chemistries to enable processing and fabrication

“…Schniepp et al 40 observed that below 500°C, the C/O ratio for the product obtained was no more than 7, and with temperatures that reached 750°C, the C/O ratio was higher than 13. Li et al 68 observed an effect of thermal annealing of foils prepared from aqueous dispersions of CCG. Conductivity improved from~40 tõ 350 S cm − 1 after treatment at 500°C.…”

Scalable One‐Step Wet‐Spinning of Graphene Fibers and Yarns from Liquid Crystalline Dispersions of Graphene Oxide: Towards Multifunctional Textiles

“…[1,2] The extraordinary properties of this intriguing material have been used to provide advantage in numerous areas including composites, energy storage and conversion, nanoelectronics, sensors, biosensors, as a support for catalysts and transparent conducting films. [1,[3][4][5][6][7][8][9] However, in all of these studies, the performance levels obtained are limited by the ability to translate the properties inherent in graphene nanocomponents into the macroscopic structures needed for practical applications. [4] In this context, the recent discovery of liquid crystalline (LC) behavior of graphene oxide (GO) dispersions in various organic, [8] and aqueous media brings added control to the assembly of larger structures using the chemical process approach.…”

“…[1,[3][4][5][6][7][8][9] However, in all of these studies, the performance levels obtained are limited by the ability to translate the properties inherent in graphene nanocomponents into the macroscopic structures needed for practical applications. [4] In this context, the recent discovery of liquid crystalline (LC) behavior of graphene oxide (GO) dispersions in various organic, [8] and aqueous media brings added control to the assembly of larger structures using the chemical process approach. [10][11][12][13][14][15][16] The LC state can be used to direct the ordered assembly of nanocomponents in macroscopic structures via simple methods like wet-spinning.…”