Stability Of Graphene Sheets Research Articles

Graphene self-folding: Evolution of free-standing few-layer graphene in plasma synthesis

Substrate and catalyst free gas-phase plasma synthesis of freestanding few-layer graphene (FLG) flakes leads to crumpled FLG structures. In this paper, we elucidate a folding-based mechanism and structure-formation process in accordance with literature on the stability of graphene sheets. Transmission electron microscopy is applied to thermophoretically-sampled FLG at various distances from the plasma zone. Single-layer and few-layer graphene were observed, and a morphology pattern evolution could be discerned. A conceptual model of graphene formation and growth is derived, starting from initial rounded single-layer graphene of a few hundred nanometer in diameter to, eventually, self-folded and strongly crumpled FLG.

Effect of hydrocarbon polymer, feed ratio, and interfacial interaction on the liquid exfoliation of graphite

Polymer-assisted liquid exfoliation of graphite is a promising technique for the scale production of defect-free graphene. In this paper, graphene nanosheets (less than 5 layers, with lateral size about 500–1500 nm) were successfully produced by directly exfoliating graphite in low boiling point chloroform, in the presence of hydrocarbon polymers such as linear paraffin wax and hyperbranched polyethylene. The effect of polymer topological structure, molecular weight, initial graphite concentration, the ratio of polymer and graphite on the exfoliation has been investigated in detail. CH-π interaction between the hydrocarbon polymers and aromatic structure in graphite, together with the steric repulsion and solubility of absorbed polymer, facilitating the exfoliation and stabilization of graphene sheets. C–H bond involved in CH-π interaction was mainly originated from methylene (-CH2-) group, which has been revealed by nuclear magnetic resonance technique. This work is of practical importance for the understanding of mechanism in polymer-assisted liquid exfoliation of graphite.

(Invited) Graphene for Bioapplications: Toxicological Studies and Integration in 3D-Scaffolds

The biological applications of graphene materials are strongly conditioned by the need to handle these nanostructures under physiological conditions, essentially complex aqueous media. While the water stabilization of Graphene Oxide (GO) can be easily achieved, this material do not possess the electrical properties of graphene. On the other hand, the mechanical exfoliation of graphite has led to the efficient separation and stabilization of graphene sheets in water when water-soluble dispersant species are used in the exfoliation process. However, many surfactants may cause toxicity problems if they are not thoroughly removed. Our group has developed a facile and inexpensive ball milling process to exfoliate graphite and to prepare graphene dispersions in water. These aqueous suspensions can be freeze-dried, resulting in a soft powder that can be easily re-suspended in aqueous media, including cell culture media, at the desired concentration. We have also made sure that the redispersed solid retains the original properties of graphene. During this talk, we will discuss (i) studies of interaction of so-prepared solutions with cells; (ii) the use of graphene in hybrid hydrogels for drug delivery purposes and for 3D cell culture media.

Finite Element Analysis to Study the Effect of Dimensional and Geometrical Parameters on the Stability of Graphene Sheets

Finite Element Analysis to Study the Effect of Dimensional and Geometrical Parameters on the Stability of Graphene Sheets

Stabilization of Graphene Sheets by a Structured Benzene/Hexafluorobenzene Mixed Solvent

Applications requiring pristine graphene derived from graphite demand a solution stabilization method that utilizes an easily removable media. Using a combination of molecular dynamics simulations and experimental techniques, we investigate the solublization/suspension of pristine graphene sheets by an equimolar mixture of benzene and hexafluorobenzene (C(6)H(6)/C(6)F(6)) that is known to form an ordered structure solidifying at 23.7 °C. Our simulations show that the graphene surface templates the self-assembly of the mixture into periodic layers extending up to 30 Å from both sides of the graphene sheet. The solvent structuring is driven by quadrupolar interactions and consists of stacks of alternating C(6)H(6)/C(6)F(6) molecules rising from the surface of the graphene. These stacks result in density oscillations with a period of about 3.4 Å. The high affinity of the 1:1 C(6)H(6)/C(6)F(6) mixture with graphene is consistent with observed hysteresis in Wilhelmy plate measurements using highly ordered pyrolytic graphite (HOPG). AFM, SEM, and TEM techniques verify the state of the suspended material after sonication. As an example of the utility of this mixture, graphene suspensions are freeze-dried at room temperature to produce a sponge-like morphology that reflects the structure of the graphene sheets in solution.

Interfacial Engineering by Proteins: Exfoliation and Functionalization of Graphene by Hydrophobins

Simply peel off the layers: Functionalities from nature may be used to meet the demands of contemporary materials science in terms of the efficient and safe production of high-quality, versatile materials. Thus, the spontaneous absorption on graphite of small amphiphilic proteins known as hydrophobins from an aqueous phase, followed by sonication, led to the exfoliation and stabilization of graphene sheets (see picture). Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.