Orientation Distribution of Molecules: Characterization and Experimental Determination by Means of Magnetic Resonance

Chumakova, Natalia A.; Vorobiev, Andrey Kh.

doi:10.1007/s00723-020-01249-3

Cited by 6 publications

(6 citation statements)

References 141 publications

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“…The order parameters P 20 , determined from the angular dependences of the EPR spectra recorded at T = 100 K (in the absence of mobility of probing molecules), are presented in Table 1 . These parameters were the averaged values of the second rank Legendre functions describing the orientation of Z-axes of the g-tensors of the radicals relative to the membrane surface normal [ 28 ]. For an ideally ordered sample, P 20 must be equal to 1; in the case of fully disordered sample, this parameter was equal to 0.…”

Section: Methodsmentioning

confidence: 99%

Sorption of Polar Sorbents into GO Powders and Membranes

et al. 2023

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The comparative study of sorption of polar substances acetonitrile and water into powders and membranes (>10 μm thick) of modified Hummers (HGO) and Brodie (BGO) graphite oxides was performed using isopiestic method (IM) and differential scanning calorimetry (DSC). Additional sorption data were obtained for pyridine and 1-octanol. Sorption measurements were accompanied by conventional XRD and XPS control. Electron paramagnetic resonance (EPR) was additionally used to characterize ordering of the membranes. The impact on sorption of synthetic procedure (Brodie or Hummers), method of making membranes, chemical nature of the sorbent, and method of sorption was systematically examined. It was demonstrated that variations in synthetic procedures within both Hummers and Brodie methods did not lead to changes in the sorption properties of the corresponding powders. Sorption of acetonitrile and pyridine was reduced by approximately half when switching from powders to membranes at ambient temperature. DSC measurements at a lower temperature gave equal sorption of acetonitrile into HGO powder and membranes. Water has demonstrated unique sorption properties. Equal sorption of water was measured for HGO membranes and powders at T = 298 K and at T = 273 K. It was demonstrated that lowering the orientational alignment of the membranes led to the increase of sorption. In practice this could allow one to tune sorption/swelling and transport properties of the GO membranes directly by adjusting their internal ordering without the use of any composite materials.

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Section: Methodsmentioning

confidence: 99%

Sorption of Polar Sorbents into GO Powders and Membranes

et al. 2023

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“…For the perfectly ordered system, all order parameters are equal to unity; for the unordered sample, all parameters are equal to zero. Our review provides links to many articles devoted to the study of orientational ordering of substances and materials using various optical, X-ray, and magnetic resonance techniques. The orientation of GOM can be represented as a series of Legendre functions, which are spherical functions that depend on only one angle: ρ ( β ) = ∑ j = 0 ∞ [ 1 2 a j 0 P j false( cos 0.25em β false) ] where P j (cos β) are Legendre functions; a j 0 are coefficients related to the orientational order parameters as follows P j 0 = a j 0 /(2 j + 1).…”

Section: Introductionmentioning

confidence: 99%

Orientational Ordering of Graphene Oxide Membranes by a Spin Probe Technique and SEM Image Analysis

Marnautov,

Matveev,

Gulin

et al. 2024

J. Phys. Chem. C

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This study introduces a method for the quantitative analysis of cross-section scanning electron micrographs of graphene oxide membranes. This method involves the segmentation of micrographs using a neural network built on the UNet architecture that was trained on synthetic data. Subsequently, the OrientLayer algorithm is applied to calculate the orientational order parameters of lamellae forming a membrane. The lamellae ordering was compared with the ordering of the oxidized graphene planes determined by using the spin probe technique. High prospects for the joint application of scanning electron microscopy and electron paramagnetic resonance techniques to study the internal structure of graphene oxide membranes were discussed.

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“…However, commonly only the second rank order parameter is determined and used for characterization of orientationally ordered materials and substances. 21 It is the consequence of using optical methods for the determination of ordering.…”

Section: Introductionmentioning

confidence: 99%