pH-driven physicochemical conformational changes of single-layer graphene oxide

Whitby, Raymond L. D.; Korobeinyk, Alina V.; Gun'ko, V.М.; Busquets, Rosa; Cundy, Andrew B.; László, Krisztina; Skubiszewska–Zięba, J.; Лебода, Р.; Tombácz, Etelka; Tóth, Ildikó Y.; Kovács, Krisztina; Mikhalovsky, Sergey V.

doi:10.1039/c1cc13725e

Cited by 87 publications

(80 citation statements)

References 21 publications

(22 reference statements)

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“…13 The conformational changes may explain the presence of a small hysteresis loop detected in potentiometric titrations (1d), which weakly depends on the ionic strength of the solution in the range from 0.005 to 0.5 M KCl. It has also been found that the drying of SLGO from solvents (particularly water) exerts surface tension effects on the graphitic domains; this behavior is similar to carbon nanotube systems under drying, 14 which may exacerbate folding effects.…”

Section: Resultsmentioning

confidence: 99%

Driving Forces of Conformational Changes in Single-Layer Graphene Oxide

et al. 2012

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The extensive oxygen-group functionality of single-layer graphene oxide proffers useful anchor sites for chemical functionalization in the controlled formation of graphene architecture and composites. However, the physicochemical environment of graphene oxide and its single-atom thickness facilitate its ability to undergo conformational changes due to responses to its environment, whether pH, salinity, or temperature. Here, we report experimental and molecular simulations confirming the conformational changes of single-layer graphene oxide sheets from the wet or dry state. MD, PM6, and ab initio simulations of dry SLG and dry and wetted SLGO and electron microscopy imaging show marked differences in the properties of the materials that can explain variations in previously observed results for the pH dependent behavior of SLGO and electrical conductivity of chemically modified graphene-polymer composites. Understanding the physicochemical responses of graphene and graphene oxide architecture and performing selected chemistry will ultimately facilitate greater tunability of their performance.

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Section: Resultsmentioning

confidence: 99%

Driving Forces of Conformational Changes in Single-Layer Graphene Oxide

et al. 2012

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“…These clusters and finer protrusion structure were originated from the twisted GO nanosheets, which is caused by the high reaction temperature and high pH value condition during the sol-gel process. 46,47 The crosslinking effect of PEI also can make the GO nanosheets corrugated, because PEI molecules would be unrestricted in reaction at either termini with different sites of the graphene sheet, potentially leading to intrasheet bonding, induced curvature and folding. 48 In contrast, this micro/nanoscale hierarchical structure is not observed on the surface of the LGM prepared by the filtration method; its surface is fairly smooth with only slight waves, as shown in Figure 7f.…”

Section: Effect Of the Sol-gel Process On The Membrane Microstructurementioning

confidence: 99%

Sol–gel fabrication of a non-laminated graphene oxide membrane for oil/water separation

et al. 2015

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A non-laminated graphene oxide membrane with superhydrophilic and underwater superoleophobic properties was fabricated by sol-gel process for effective oil/water separation. † Electronic Supplementary Information (ESI) available: Porosity calculation, separation apparatus, high magnification top view SEM images of LGM, sliding angle measurement of 1,2-dichloroethane (DCE) droplets on the NLGM in water, separation results for other emulsion systems, SEM images of the NLGM after oil/water emulsion separation performance test, photograph of an underwater oil droplet on the NLGM and simulated underwater drag deformation force tests after oil/water emulsion separation test and element component percentages of GO and the NLGM, and. See A non-laminated graphene oxide membrane crosslinked by polyethyleneimine was prepared via a one-step sol-gel process. In the as-prepared membrane, the GO nanosheets remain disordered as in the sol state to form a randomly arranged GO assembly structure, which results in a much higher flux compared with the general laminated GO membrane prepared via vacuum filtration or spin coating because of the lower flow resistance. Further, this random assembly of GO nanosheets give rise to a hierarchical micro/nanoscale rough structure on the membrane surface. Along with the crosslinking reaction, PEI was grafted onto the GO nanosheets to make them hydrophilic. Combining the hydrophilic surface chemistry with the micro/nanoscale hierarchical surface structure, the non-laminated GO membrane exhibited the desired superhydrophilic and underwater superoleophobic properties. We have tested the membrane to separate a series of surfactant-free and surfactant-stabilized oil-in-water emulsions. A high separation efficiency (>99%) and flux were achieved using only gravity without any extra power, much larger than commerical filtration membranes with similar permeation properties. Moreover, the membrane shows an outstanding antifouling performance for oil droplets and can be recycled easily for long-term use.

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“…The textural changes affected by freezing (i.e. cryogelation) of aqueous suspensions of such solid materials as single (SLGO) and multi-layer (MLGO) graphene oxides in superhydrated state could be better studied by NMR cryoporometry [251] than by standard adsorption methods because these systems are very unstable during drying [252] similar to soft organic cryogels. Thus, structural, textural and adsorption characterisation of cryogels, especially with soft materials superhydrated in native state and unstable during drying, should be improved for deeper insight into the interfacial phenomena occurring at their surfaces or into the phenomena occurring in pores over the total size range (2 < d < 310 5 nm).…”

Section: Diffusion Of Small Molecules Polymers Proteins and Cells Wmentioning

confidence: 99%

Cryogels: Morphological, structural and adsorption characterisation

Gun'ko

Savina

Mikhalovsky

2013

Advances in Colloid and Interface Science

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*Graphical Abstract (for review)Cryotripic gelation technique allows the synthesis of solid and soft macroporous gels Textural characterisation of cryogel in native superhydrated state with noninvasive methods Adsorption and diffusion characteristics of macroporous cryogels with respect to macromolecules and cells Theoretical modelling of adsorption from aqueous media *Highlights (for review) Please find the revised manuscript entitled "Cryogels: morphological, structural and adsorption characterisation" by Vladimir M. Gun'ko, Irina N. Savina, Sergey V. Mikhalovsky to re-consider for publication in the "Advances in Colloid and Interface Science"The paper was completely edited and changed according to reviewers comments.Sincerely yours, Prof. V. M. Gun'koCover Letter ABSTRACTExperimental results on polymer, protein, and composite cryogels and data treatment methods used for morphological, textural, structural, adsorption and diffusion characterisation of the materials are analysed and compared. Treatment of microscopic images with specific software gives quantitative structural information on both native cryogels and freeze-dried materials that is useful to analyse the drying effects on their structure. A combination of cryoporometry, relaxometry, thermoporometry, small angle X-ray scattering (SAXS), equilibrium and kinetic adsorption of low and high-molecular weight compounds, diffusion breakthrough of macromolecules within macroporous cryogel membranes, studying interactions of cells with cryogels provides a consistent and comprehensive picture of textural, structural and adsorption properties of a variety of cryogels. This analysis allows us to establish certain regularities in the cryogel properties related to narrow (diameter 0.4 < d < 2 nm), middle (2 < d < 50 nm) and broad (50 < d < 100 nm) nanopores, micropores (100 nm < d < 100 m) and macropores (d > 100 m) with boundary sizes within modified life science pore classification. Particular attention is paid to water bound in cryogels in native superhydrated or freeze-dried states. At least, five states of water -free unbound, weakly bound (changes in the Gibbs free energy G < 0.5-0.8 kJ/mol) and strongly bound (G > 0.8 kJ/mol), and weakly associated (chemical shift of the proton resonance  H = 1-2 ppm) and strongly associated ( H = 3-6 ppm) waters can be distinguished in hydrated cryogels using 1 H NMR, DSC, TSDC, TG and other methods. Different software for image treatment or developed to analyse the data obtained with the adsorption, diffusion, SAXS, cryoporometry and thermoporometry methods and based on regularisation algorithms is analysed and used for the quantitative morphological, structural and adsorption characterisation of individual and composite cryogels, including polymers filled with solid nano-or microparticles.

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pH-driven physicochemical conformational changes of single-layer graphene oxide

Cited by 87 publications

References 21 publications

Driving Forces of Conformational Changes in Single-Layer Graphene Oxide

Driving Forces of Conformational Changes in Single-Layer Graphene Oxide

Sol–gel fabrication of a non-laminated graphene oxide membrane for oil/water separation

Cryogels: Morphological, structural and adsorption characterisation

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