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Electron Paramagnetic Resonance Investigation of the Structure of Graphene Oxide: pH-Dependence of the Spectroscopic Response

Wang, B, Fielding, AJ and Dryfe, RAW (2018) Electron Paramagnetic Resonance Investigation of the Structure of Graphene Oxide: pH-Dependence of the Spectroscopic Response. ACS Applied Nano Materials. ISSN 2574-0970

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Abstract

The time-dependence of the electron paramagnetic resonance (EPR) signal arising from purified graphene oxide (GO) in various solvents has been investigated. The prepared GO was sequentially base and acid (ba) treated to remove manganese impurities. The EPR signal of ba-GO was found to be pH-dependent when exposed to different aqueous solutions, which is related to the decarboxylation process the material undergoes in solution. This process involves the fragmentation of the carbonaceous framework and occurs most rapidly in alkaline conditions. Under acidic conditions, fragmentation is much slower, leading to a gradual increase in the EPR signal from ba-GO in the presence of oxygen. Inferred structural changes were correlated with those deduced from X-ray photoelectron spectroscopy to explain the observed pH- and time-dependent effects. Comparative experiments showed that the oxygen molecule was the key to the increase of unpaired electron density. Exposure to superoxide anions in situ confirmed that the scavenging ability of ba-GO was related to the oxidation of the sp2-carbon structure, which led to an increase of the EPR signal. Overall, the results demonstrate changes of the structure and stability of GO at different pH values.

Item Type: Article
Subjects: Q Science > QD Chemistry
Divisions: Pharmacy & Biomolecular Sciences
Publisher: American Chemical Society (ACS)
Date Deposited: 23 Jan 2019 09:20
Last Modified: 23 Jan 2019 22:02
DOI or Identification number: 10.1021/acsanm.8b01329
URI: http://researchonline.ljmu.ac.uk/id/eprint/9995

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