EPR and Impedance Measurements of Graphene Oxide and Reduced Graphene Oxide

Kempiński, Mateusz; Łoś, Szymon; Florczak, Patryk; Kempiński, W.; Jurga, Stefan

doi:10.12693/aphyspola.132.81

Cited by 14 publications

(9 citation statements)

References 18 publications

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“…It is known that the ESR signal from GO is well observed at room temperature, but the ESR signal of reduced GO can be observed only below 100 K [18]. Since our samples of GO are reduced (contain a small amount of hydroxyl and carboxylic groups), this guarantees the absence of additional lines from our GO in the ESR spectra.…”

Section: Characterization Of the Erythrocyte Suspension Aftermentioning

confidence: 84%

Change in the Microviscosity of Erythrocyte Membranes and Proteins in Blood Plasma after Graphene Oxide Addition: The ESR Spectroscopy Study

Karachevtsev

Кartel

Іванов

et al. 2019

Journal of Spectroscopy

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The change in the microviscosity of erythrocyte membranes and the proteins in blood plasma after graphene oxide addition is studied by the ESR spectroscopy exploiting two spin probes with different lipophilic components in the structures. Experiments with charged spin probe 2 embedded into the erythrocyte membrane showed that the introduction of graphene oxide in small concentrations (∼70 μg/ml) into a suspension of erythrocytes did not lead to significant changes in the microviscosity of their membranes. Correlation times of hydrophobic spin probe 1 adsorbed to hydrophobic pockets of plasma proteins demonstrate a gradual slowdown at the graphene oxide injection into blood plasma that indicates a small deformation of the hydrophobic cavity of protein at the adsorption. However, this protein binding with graphene oxide does not cause the displacement of the spin probe from their hydrophobic cavities, which is evidence about small changes in the protein secondary structure. The obtained results indicate the insignificant cytotoxicity effect of small concentrations of graphene oxide for erythrocytes and blood plasma.

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Section: Characterization Of the Erythrocyte Suspension Aftermentioning

confidence: 84%

Change in the Microviscosity of Erythrocyte Membranes and Proteins in Blood Plasma after Graphene Oxide Addition: The ESR Spectroscopy Study

Karachevtsev

Кartel

Іванов

et al. 2019

Journal of Spectroscopy

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“…Increasing the number of the paramagnetic centers as well as growing losses due to the cyclotron motion of conduction electrons in the external magnetic field B 0 change B 1 . Moreover, due to hygroscopic properties of GO water molecules can be adsorbed on its surface [33] and the proton conductivity of this material can be observed [6,34,35]. This conductivity as well as the molecular dynamics of the functional groups on the surfaces of GO and RGO result in the non-resonant losses and can also change B 1 .…”

Section: Resultsmentioning

confidence: 99%

“…Graphene oxide (GO) is a well-known and widely used form of functionalized graphene [1,2]. Experimental studies of paramagnetic properties of this material have been reported [3][4][5][6][7][8]. The electron paramagnetic resonance (EPR) signals of GO and other graphene-related materials can be due to localized electrons, conduction electrons or their exchange coupled system [9,10].…”

Section: Introductionmentioning

confidence: 99%

Identification of a Slowly Relaxing Paramagnetic Center in Graphene Oxide

et al. 2018

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We demonstrate the existence of two types of paramagnetic centers in a pure graphene oxide. Saturation features of the electron paramagnetic resonance (EPR) spectrum in the temperature range of 4.2-300 K reveal that one of these centers has the spin-lattice relaxation time longer than 1.6 μs at room temperature. The spectrum of these centers consists of a central line and two satellite lines. The satellite lines result from the forbidden transitions in the hyperfine structure induced by protons in the vicinity of the slowly relaxing centers. The observability of the satellites can be used as a characteristic signature of graphene oxide purity. Since the number of slowly relaxing centers is reduced during chemical reduction of graphene oxide, this type of centers can be attributed to the isolated unfunctionalized carbons in the highly functionalized regions of GO. The second type of paramagnetic centers has shorter relaxation times and dominates in the reduced graphene oxide.

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“…Recently, an unusually strong temperature dependence of the intensity of the narrow EPR line in prGO was observed and explained by Anderson localization of conduction electrons in the strongly defected structure of graphene flakes . This type of localization in rGO was earlier deduced from impedance measurements in addition to the expected and more frequently observed Mott localization on graphene flakes. ,,− …”

Section: Introductionmentioning

confidence: 84%

“…Moreover, conduction electrons mediate exchange interactions between isolated magnetic moments, which can lead to magnetic ordering. The preferential ordering in the graphene layer is antiferromagnetic in nature. , In contrast to a single exchange-narrowed EPR line, two or more lines in GO and rGO have been reported. ,,,− Since at low density of conduction electrons not all PCs are exchange-coupled, uncoupled centers can manifest themselves in an overall spectrum by an additional EPR line. The observed narrower EPR line is associated with unpaired electrons localized at defects and edge states. , Attempts to distinguish between such PCs and conduction electrons were made assuming different temperature dependences of their signals in the continuous wave (CW) EPR .…”

Section: Introductionmentioning

confidence: 99%

Electron Spin Echo Studies of Hydrothermally Reduced Graphene Oxide

et al. 2021

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Ecofriendly hydrothermal reduction of graphene oxide is widely used for producing hydrogels and aerogels, but it yields partly reduced graphene oxide (prGO) containing oxygen groups and some number of paramagnetic centers (PCs). In order to identify structural changes introduced by the reduction process, these PCs are studied by electron spin echo spectroscopy in the temperature range of 5–160 K. Two types of PCs with different spin–lattice (T 1) and phase memory (T m) relaxation times observed below 20 K result from a nonuniform distribution of magnetic defects. Above 20 K, only the PCs with the shorter T 1 and T m persist. Temperature dependences of T 1 and the distribution of T 1 for each type of the PCs reveal lattice distortions around the PCs and structural disorder in prGO. The unusually strong temperature dependence of the spin echo intensity is explained by the localization of conduction electrons. The localization is destroyed at high temperature, and exchange interactions decrease the number of the observed PCs. Every such PC is created by the sp 3 defect induced by hydrogen covalently bonded to graphene. The obtained results indicate that the hydrothermal reduction is accompanied by partial hydrogenation of graphene. The presence of such hydrogen atoms is confirmed by infrared spectroscopy.

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EPR and Impedance Measurements of Graphene Oxide and Reduced Graphene Oxide

Cited by 14 publications

References 18 publications

Change in the Microviscosity of Erythrocyte Membranes and Proteins in Blood Plasma after Graphene Oxide Addition: The ESR Spectroscopy Study

Change in the Microviscosity of Erythrocyte Membranes and Proteins in Blood Plasma after Graphene Oxide Addition: The ESR Spectroscopy Study

Identification of a Slowly Relaxing Paramagnetic Center in Graphene Oxide

Electron Spin Echo Studies of Hydrothermally Reduced Graphene Oxide

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