Mechanism of Formation and Chemical Structure of Graphene Oxide

Dimiev, Ayrat M.

doi:10.1002/9781119069447.ch2

Cited by 39 publications

(38 citation statements)

References 71 publications

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“…22 According to the common view on the GO structure, the oxidized domains contain hydroxo (tertiary alcohols) and epoxy (1,2-ethers) groups. 2,23,24 The flake edges might contain additional functional groups, but their contribution to the solubility is negligible due to their relatively small number. Today, when the general structure of GO is more or less clear, the remaining challenge is to reveal the fine chemical structure of the oxidized domains, i.e.…”

Section: Resultsmentioning

confidence: 99%

“…1 One of the main advantages of GO over its non-oxidized counterpart is its ability to form stable solutions in several solvents, by exfoliating to single-atomic-layer sheets. 2 The solution phase provides reactants easy and unimpeded access of to the GO surface, opening unlimited avenues for liquid phase processing. Such applications of GO as polymer composites, selective membranes, hydrogels, electrode materials, etc.…”

Section: Introductionmentioning

confidence: 99%

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New insights into the solubility of graphene oxide in water and alcohols

Neklyudov

Khafizov

Sedov

et al. 2017

Phys. Chem. Chem. Phys.

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132

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aOne of the main advantages of graphene oxide (GO) over its non-oxidized counterpart is its ability to form stable solutions in water and some organic solvents. At the same time, the nature of GO solutions is not completely understood; the existing data are scarce and controversial. Here, we demonstrate that the solubility of GO, and the stability of the as-formed solutions depend not just on the solute and solvent cohesion parameters, as commonly believed, but mostly on the chemical interactions at the GO/solvent interface. By the DFT and QTAIM calculations, we demonstrate that the solubility of GO is afforded by strong hydrogen bonding established between GO functional groups and solvent molecules.The main functional groups taking part in hydrogen bonding are tertiary alcohols; epoxides play only a minor role. The magnitude of the bond energy values is significantly higher than that for typical hydrogen bonding. The hydrogen bond energy between GO functional groups and solvent molecules decreases in the sequence: water 4 methanol 4 ethanol. We support our theoretical results by several experimental observations including solution calorimetry. The enthalpy of GO dissolution in water, methanol and ethanol is À0.1815 AE 0.0010, À0.1550 AE 0.0012 and À0.1040 AE 0.0010 kJ g À1 , respectively, in full accordance with the calculated trend. Our findings provide an explanation for the well-known, but poorly understood solvent exchange phenomenon.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

New insights into the solubility of graphene oxide in water and alcohols

Neklyudov

Khafizov

Sedov

et al. 2017

Phys. Chem. Chem. Phys.

Self Cite

132

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“…Graphene oxide brings oxygen-containing groups that can interact with the polymeric matrix. In addition, the oxygen-functional groups can be exploited for surface modification of the nanosheets, while the affinity of polar groups as –COOH and –OH on GO sheets with CO 2 molecules [ 45 ] has positive effects on the CO 2 /gas solubility selectivity. On the other hand, the sheeted GO structure can offer molecular sieve channels for gas permeation.…”

Section: Materials For the Analysed Mmmsmentioning

confidence: 99%

“…An increasing PEG-MEA content resulted in a significantly increased crystallinity degree of PEO in Pebax ® /PEG-MEA blend membranes, demonstrating the incorporation of PEG-MEA in the Pebax ® 1657 matrix [ 47 ]. Instead, the crystallinity of PA in Pebax ® decreased, leading to improved gas permeability for the blends [ 45 ]. Both PEO and PA crystallinity were decreased, as shown by DSC and XRD, upon the loading of GO into the Pebax/PEG-MEA blends [ 47 ].…”

Section: Main Issues In Mmms Developmentmentioning

confidence: 99%

A Review of the Recent Progress in the Development of Nanocomposites Based on Poly(ether-block-amide) Copolymers as Membranes for CO2 Separation

Clarizia

Bernardo

2021

Polymers

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An inspiring challenge for membrane scientists is to exceed the current materials’ performance while keeping the intrinsic processability of the polymers. Nanocomposites, as mixed-matrix membranes, represent a practicable response to this strongly felt need, since they combine the superior properties of inorganic fillers with the easy handling of the polymers. In the global strategy of containing the greenhouse effect by pursuing a model of sustainable growth, separations involving CO2 are some of the most pressing topics due to their implications in flue gas emission and natural gas upgrading. For this purpose, Pebax copolymers are being actively studied by virtue of a macromolecular structure that comprises specific groups that are capable of interacting with CO2, facilitating its transport with respect to other gas species. Interestingly, these copolymers show a high versatility in the incorporation of nanofillers, as proved by the large number of papers describing nanocomposite membranes based on Pebax for the separation of CO2. Since the field is advancing fast, this review will focus on the most recent progress (from the last 5 years), in order to provide the most up-to-date overview in this area. The most recent approaches for developing Pebax-based mixed-matrix membranes will be discussed, evidencing the most promising filler materials and analyzing the key-factors and the main aspects that are relevant in terms of achieving the best effectiveness of these multifaceted membranes for the development of innovative devices.

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“…Graphene oxide (GO) is a 2D material characterized with the honeycomb molecular structure. GO has gained increasing attention because of its remarkable physical, chemical and electronic properties [1]. GO contains various oxygenated functional groups such as hydroxyl, epoxy, carbonyl, and carboxyl groups.…”

Section: Introductionmentioning

confidence: 99%

Improving the proton conductivity of graphene oxide membranes by intercalating cations

et al. 2019

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Graphene oxide (GO) membrane has gained increasing attention because of its extraordinary physical and chemical properties and high proton conductivity. GO is rich in oxygenated functional groups, which can support proton transportation. However, pristine GO is unstable at high temperatures due to the removal of oxygen functional groups, resulting in a decrease in the interlayer distance of stacked GO nanosheets. Hence, we propose a modification of GO membranes via the intercalation of cations to enhance the proton conductivity. Modified self-standing GO membranes with Al 3+ and La 3+ were fabricated by a vacuum filtration method. They exhibited a larger distance of the interlayer that serves as proton hopping pathways. Furthermore, the modified GO membrane showed a higher proton conductivity than a pristine GO membrane even at 80 °C, as confirmed by Electrochemical Impedance Spectroscopy. The results demonstrate that intercalating cations in between GO nanosheets is effective in improving the practical feasibility of proton conducting GO membranes.

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Mechanism of Formation and Chemical Structure of Graphene Oxide

Cited by 39 publications

References 71 publications

New insights into the solubility of graphene oxide in water and alcohols

New insights into the solubility of graphene oxide in water and alcohols

A Review of the Recent Progress in the Development of Nanocomposites Based on Poly(ether-block-amide) Copolymers as Membranes for CO2 Separation

Improving the proton conductivity of graphene oxide membranes by intercalating cations

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