Synthesis and reduction of large sized graphene oxide sheets

Dong, Lei; Yang, Jieun; Chhowalla, Manish; Loh, Kian Ping

doi:10.1039/c7cs00485k

Cited by 257 publications

(145 citation statements)

References 96 publications

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“…GO aqueous dispersions have adjustable rheology, which enable them to work as high‐performance ink for various fabrication techniques . In addition, the large lateral sized GO sheets are beneficial to achieve higher shear viscosity and storage modulus than the smaller GO sheets in aqueous solution, which help obtain printable ink at a relatively low solid content and thus favor printing of low‐density graphene structures. We experimentally found that the aqueous‐based ink with a solid content of 2.5 wt% is very promising for 3D printing (Figure S2c,d, Supporting Information).…”

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confidence: 99%

3D Printing of Ultralight Biomimetic Hierarchical Graphene Materials with Exceptional Stiffness and Resilience

et al. 2019

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Assembly of lightweight engineering and functional materials with superb mechanical performance, such as high stiffness, super resilience, and stability, is highly demanded to pave ways for their practical applications. [1] However, how to simultaneously achieve both stiffness and resilience in a man-made material at low-density remains a challenging scientific and engineering issue. Biological materials have found their way to achieve outstanding mechanical properties at low density by assembling sophisticate hierarchical structures from microscopic to macroscopic scales, and thus provide inspirations for designing and manufacturing advanced biomimetic materials. [2] Plant materials, such as plant stem [3] and wood, [4] represent an important class of lightweight natural materials with superb mechanical properties. The slender grass stems of Elytrigia repens is a representative natural material with high mechanical performance and lightweight features owing to a specially evolved hierarchical architecture with a macroscopically hollow and microscopically cellular structure. The macroscopically hollow structure combined with the cellular microstructure serves as an excellent force-bearing structure that is conducive to the dispersion of strain and stress, and thus efficiently enhances the stiffness, and resilience and reduce the density, simultaneously. [5] In recent years, the constructions of biomimetic structures have attracted extensive attention because of their potential ability to achieve high mechanical properties and lightweight artificial engineering and functional materials. [6] Despite progresses in the construction of biomimetic structures, the poor mechanical properties at low density remain as a major bottleneck in artificial biomimetic materials, which are mainly due to the lack of appropriate structures at both macro-and microlevels at the same time.The ink-based 3D printing, as a powerful additive manufacturing technique for producing 3D structures both in microscopic and macroscopic scales, [6b,7] shows great potential to assembly materials into 3D hierarchical structures. Additionally, 3D printing displays distinct advantages of high degree of freedom in structure design, which enable the ability to design and construct versatile structures for realizing the Biological materials with hierarchical architectures (e.g., a macroscopic hollow structure and a microscopic cellular structure) offer unique inspiration for designing and manufacturing advanced biomimetic materials with outstanding mechanical performance and low density. Most conventional biomimetic materials only benefit from bioinspired architecture at a single length scale (e.g., microscopic material structure), which largely limits the mechanical performance of the resulting materials. There exists great potential to maxime the mechanical performance of biomimetic materials by leveraging a bioinspired hierarchical structure. An ink-based three-dimensional (3D) printing strategy to manufacture an ultralight biomimetic hierarchical g...

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confidence: 99%

3D Printing of Ultralight Biomimetic Hierarchical Graphene Materials with Exceptional Stiffness and Resilience

et al. 2019

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“…16,17 We produced continuous GO films having a thickness of ~ 5.5 nm on UVO-treated glass (Figure S2(a)). RGO was produced from GO substrates by classical low thermal reduction of GO substrates 18,19 (Explained in detailed in Supplementary Information). RGO substrates had a blackish appearance (compared to a slight brown tint of GO), consistent with reduction of oxide groups (Figure S1) and verified with XPS (Figure 1(a) and Table 1).…”

Section: Preparation and Characterization Of Gbm Substratesmentioning

confidence: 99%

“…20,21 Upon thermal reduction more than 50% of epoxy, carbonyl and carboxyl functional groups were removed; however, the hydroxyl functional groups were almost unchanged (Figure 1(b) and Table 1). Studies have shown that highly stable hydroxyls and carbonyl groups are difficult to remove from the graphene sheet edges at low temperature reduction without inducing detects; 18,19 as a result, RGO retains 15 -25 % residual oxygen concentration upon low thermal reduction.…”

Section: Preparation and Characterization Of Gbm Substratesmentioning

confidence: 99%

Molecular control of interfacial protein structure on graphene-based substrates steers cell fate

Kumar

Parekh

2020

Preprint

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The use of graphene-based materials (GBMs) for tissue-engineering applications is growing exponentially due to the seemingly endless multi-functional and tunable physicochemical properties of graphene, which can be exploited to influence cellular behaviours. Despite many demonstrations wherein cell physiology can be modulated on GBMs, a clear mechanism connecting the different physicochemical properties of different GBMs to cell fate has remained elusive. In this work, we demonstrate how different GBMs can be used to cell fate in a multi-scale studystarting from serum protein (Fibronectin) adsorption to molecular scale morphology, structure and bioactivity, and finally ending with stem cell response. By changing the surface chemistry of graphene substrates with only heating, we show that molecular conformation and morphology of surface adsorbed fibronectin controls epitope presentation, integrin binding, and stem cell attachment. Moreover, this subtle change in protein structure is found to drive increased bone differentiation of cells, suggesting that physicochemical properties of graphene substrates exert cell control by influencing adsorbed protein structure.Keywords: Graphene-based materials (GBMs), protein interaction, protein molecular structure, protein bioactivity, stem cell differentiation, identification of biochemical activity changes of insulin on graphene and GO surfaces was presented. Experiments directly probing protein molecular structure, conformation, and exposure of bioactive domains of proteins are required to unequivocally demonstrate if GBMs modulate protein structure to influence stem cell interaction. In addition, controlled experiments evaluating the effect of the adsorbed protein and its molecular features on stem cell attachment and differentiation should be done in absence and presence of serum. Providing such experiments will provide mechanistic insight on GBM-mediated stem cell response for future rational design of materials from graphene.Here, we study ECM protein adsorption, interaction, orientation and structure from the macroscale to the molecular scale on GBMs and perform stem cell culture in the presence and absence of serum to relate the physicochemistry of GBMs with protein structure and cell fate. We used GO and RGOthe two most commonly used GBMs as exemplary engineering materialsto evaluate bioactivity of GBMs having different surface chemistries by investigating the effect of GBM chemistry on fibronectin (FNa protein abundant in the ECM), adsorption, orientation, and structure. We couple these surface characterization experiments with biochemical activity assays and stem cell response experiments, allowing us to elucidate the link between physicochemical properties of GBMs, FN protein unfolding, altered biochemical activity, and stem cell differentiation.Corresponding Authors

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“…Graphene flakes exfoliated by high power sonication of graphite are also provided as dispersion for solution processing. Graphene thin films (not single layer) are also obtained from previously deposited GO films by chemical reduction with different techniques (delivering the so‐called reduced graphene oxide, rGO), but with poor quality compared with that of CVD monolayer graphene . The inverse procedure, namely, electrochemical oxidation of graphene by local anodic oxidation (LAO) appears as a suggestive patterning technique to achieve a direct integration of single layers of both materials with the highest quality, optimal control, and precision.…”

Section: Introductionmentioning

confidence: 99%

New Concepts for Production of Scalable Single Layer Oxidized Regions by Local Anodic Oxidation of Graphene

Quesada

Borrás

García-Vélez

et al. 2019

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A deep comprehension of the local anodic oxidation process in 2D materials is achieved thanks to an extensive experimental and theoretical study of this phenomenon in graphene. This requires to arrange a novel instrumental device capable to generate separated regions of monolayer graphene oxide (GO) over graphene, with any desired size, from micrometers to unprecedented mm2, in minutes, a milestone in GO monolayer production. GO regions are manufactured by overlapping lots of individual oxide spots of thousands µm2 area. The high reproducibility and circular size of the spots allows not only an exhaustive experimental characterization inside, but also establishing an original model for oxide expansion which, from classical first principles, overcomes the traditional paradigm of the water bridge, and is applicable to any 2D‐material. This tool predicts the oxidation behavior with voltage and exposure time, as well as the expected electrical current along the process. The hitherto unreported transient current is measured during oxidation, gaining insight on its components, electrochemical and transport. Just combining electrical measurements and optical imaging estimating carrier mobility and degree of oxidation is possible. X‐ray photoelectron spectroscopy reveals a graphene oxidation about 30%, somewhat lower to that obtained by Hummers' method.

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Synthesis and reduction of large sized graphene oxide sheets

Cited by 257 publications

References 96 publications

3D Printing of Ultralight Biomimetic Hierarchical Graphene Materials with Exceptional Stiffness and Resilience

3D Printing of Ultralight Biomimetic Hierarchical Graphene Materials with Exceptional Stiffness and Resilience

Molecular control of interfacial protein structure on graphene-based substrates steers cell fate

New Concepts for Production of Scalable Single Layer Oxidized Regions by Local Anodic Oxidation of Graphene

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