Molecular Organization of the Swelled Graphite Oxide and the Graphite Oxide Membranes According to Spin Probe Data

Chumakova, N.A.; Rebrikova, A.T.; Vorobiev, A.K.; Korobov, M.V.; Yankova, T.S.; Matveev, M.V.; Kaplin, A.V.; Astvatsaturov, D.A.; Popov, D.S.

Авторы: Chumakova N.A., Rebrikova A.T., Vorobiev A.Kh, Korobov M.V., Yankova T.S., Matveev M.V., Kaplin A.V., Astvatsaturov D.A., Popov D.S.
Сборник: Modern Developments of Magnetic Resonance. Abstracts of international conference
Тезисы
Год издания: 2021
Место издания: АО “Информационно-издательский центр” Казань
Первая страница: 114
Последняя страница: 115
Аннотация: Graphite oxide (GO) is a layered material formed by graphene parallel planesdecorated with oxygen-containing groups (–OH, –O–, –CO, –COOH, etc.) Swelling of GO in polar liquids is accompanied by intercalation of the liquids intothe inter-plane space and increasing of the inter-plane distances from 6–7 Å to~20–25 Å. Membranes formed by GO possess highly selective permeability. Itwas established that dry GO membrane can be easily penetrated by water andhydrated ions with radii less than 4.5 Å but they are practically not penetrativeby other liquids and even gases. The cause of this unique behavior is still notclear. The hypothesis was proposed that the membrane permeability is connectedwith the molecular mobility of the intercalated water in the interplane spaces ofGO [1]. The permeability can also depend on the orientational alignment of themembrane-forming layers. At present, the study of the GO materials is largelyhindered by a lack of suitable experimental techniques. The adaptation of thewidely used spin probe method for the investigation of the molecular organization of swelled GO and GO membranes is the aim of the present work.EPR spectra of nitroxide spin probes in the systems “GO–polar liquid” includethe signals of the nitroxides with high and slow rotational mobility (rotationalcorrelation times come to ~10–9 s and ~10–7 s correspondently). The first signalwas attributed to the spin probes located in the liquid, the second one to theradicals sorbed on the inner surface of GO. For the systems “BGO (Brodiesynthetized graphite oxide) – polar liquid” it was shown that rotational mobility of the sorbed radicals changes considerably during the phase transformation.EPR spectra demonstrate that the transformation proceeds within a temperaturerange of ~30°. We suppose that this range reflects some inhomogeneity of thematerial [2].The rotational mobility of the probes located in the intercalated liquid (water,acetonitrile, methanol) was found to be just a little slowed down compared tothe rotation in the bulk liquid. This observation indicates that the intercalatedliquid form the liquid-like medium between the graphene planes. The existenceof a mobile liquid (water, acetonitrile, trifluoroethanol) in the inter-plane spaceof GO was confirmed reliably by NMR spectroscopy [3]. It was revealed thatthe spin probe method is more sensitive to a small amount of unfrozen liquidintercalated into GO than NMR spectroscopy.The spin probe method was found to be a unique technique for quantitativeestimation of the layer ordering in the graphite oxide membranes. Until now, thealignment of the GO membranes was estimated only qualitatively (visually) bycross-sectional SEM and TEM. We propose to characterize the ordering of themembranes by orientation distribution of the spin probes sorbed on inner surfaceof GO (Fig. 1). It was shown that nitroxide radicals as well as paramagneticcomplexes [Cu(NH3)4]2+ adequately reflect the alignment of the membranes.
Добавил в систему: Аствацатуров Дмитрий Александрович

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Molecular Organization of the Swelled Graphite Oxide and the Graphite Oxide Membranes According to Spin Probe Dataтезисы доклада Тезисы

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