On the Solvation Behavior of Graphene Oxide in Ethylene Glycol/Water Mixtures

© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim The self-association and solvation pattern of graphene oxide (GO) in water, ethylene glycol (EG), and their mixtures were analyzed by means of UV/Vis spectrophotometry. A careful analysis of the absorbance dependencies vs. the GO concentration shows that self-association of the GO sheets in EG occurs at higher concentration compared to that in water. It was established that depending on the mixed solvent composition, two different types of the GO solvates are formed. The results of quantum chemical calculations allow one to suggest that in the water-rich compositions, the GO oxygen-containing groups are in direct contact with water molecules while in the glycol-rich media the EG molecules fully substitute water in the GO's first solvation layer

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

© The Owner Societies 2017. One 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 0.1815 0.0010, 0.1550 0.0012 and 0.1040 0.0010 kJ g1, respectively, in full accordance with the calculated trend. Our findings provide an explanation for the well-known, but poorly understood solvent exchange phenomenon

Magneto-Optical Properties of the Magnetite-Graphene Oxide Composites in Organic Solvents

Copyright © 2018 American Chemical Society. Graphene oxide (GO) aqueous solutions are known to form liquid crystals that can switch in electric fields. Magnetic fields as external stimuli are inefficient toward GO because of its diamagnetic properties, and GO is known to be insoluble in most of the organic solvents. In this study, composites of GO with oleate-protected magnetite nanoparticles were prepared as stable colloid solutions in the mixed isopropanol-chloroform solvents. The structure of the composite particles and the optical properties of their solutions can be controlled by the ratio of the mixing parent components. The as-prepared solutions are highly responsive to external magnetic field. As the consequence, the optical transmission and the direction of light scattering can be efficiently manipulated. These systems pave the way for fabricating functional materials, such as magneto-optical switches, density-gradient materials, and micromotors. Solubility in nonpolar organic solvents broadens the scope of their potential applications

Oxidatively modified carbon as efficient material for removing radionuclides from water

© 2017 Elsevier LtdThere is a constant need to develop advantageous materials for removing radioactive waste from aqueous systems. Here we propose a new carbon-based material prepared by oxidative treatment of various natural carbon sources. The as-prepared oxidatively modified carbon (OMC) has an oxygen-rich surface, and retains its particulate granular texture. It has relatively low cost and can be used in traditional filtration columns. The sorption ability of OMC toward several metal cations is demonstrated. It is especially efficient toward Cs+ cations, the species that are among the most difficult to remove from the waters at the Fukushima nuclear plant

Longitudinal unzipping of carbon nanotubes to form graphene nanoribbons.

Published versio

Graphene re-knits its holes

Nano-holes, etched under an electron beam at room temperature in singlelayer graphene sheets as a result of their interaction with metalimpurities, are shown to heal spontaneously by filling up with either non-hexagon, graphene-like, or perfect hexagon 2D structures. Scanning transmission electron microscopy was employed to capture the healing process and study atom-by-atom the re-grown structure. A combination of these nano-scale etching and re-knitting processes could lead to new graphene tailoring approaches.Comment: 11 pages, 4 figure

Solvent-induced changes in the graphene oxide absorption spectrum. The case of dimethylsulfoxide/water mixtures

© 2019 Elsevier B.V. In the present contribution solvation pattern of graphene oxide (GO) in dimethylsulfoxide (DMSO)/H2O mixtures was investigated by means of UV–Vis absorption spectroscopy. It was shown that with increase of the DMSO content, xDMSO, the GO's n–π* transition band, appearing at 307 nm in water, blue-shifts by 34 nm in pure DMSO. Together with an observation of an isosbestic point at 320 nm this finding indicates the changes in the GO's first solvating layer. Analysis of the n–π* transition band transfer energy shows that at xDMSO ≲ 0.55 and xDMSO ≳ 0.55 the GO's groups containing C[dbnd]O fragments are preferentially solvated by H2O and DMSO molecules, respectively. In agreement with the latter, the Wallace-Katz analysis yields two absorbing species in the whole range of xDMSO and one species in water-rich and DMSO-rich regions. Quantum chemical calculations reveals formation of H-bonds between GO's carboxyl groups and both H2O and DMSO molecules. The binding energies of H2O and DMSO molecules with the GO's model basal surfaces point out at possible substitution of water molecules in the GO's first solvation layer by DMSO molecules

On the Solvation Behavior of Graphene Oxide in Ethylene Glycol/Water Mixtures

© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim The self-association and solvation pattern of graphene oxide (GO) in water, ethylene glycol (EG), and their mixtures were analyzed by means of UV/Vis spectrophotometry. A careful analysis of the absorbance dependencies vs. the GO concentration shows that self-association of the GO sheets in EG occurs at higher concentration compared to that in water. It was established that depending on the mixed solvent composition, two different types of the GO solvates are formed. The results of quantum chemical calculations allow one to suggest that in the water-rich compositions, the GO oxygen-containing groups are in direct contact with water molecules while in the glycol-rich media the EG molecules fully substitute water in the GO's first solvation layer

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

© The Owner Societies 2017. One 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 0.1815 0.0010, 0.1550 0.0012 and 0.1040 0.0010 kJ g1, respectively, in full accordance with the calculated trend. Our findings provide an explanation for the well-known, but poorly understood solvent exchange phenomenon