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    Understanding the Role of Oxidative Debris on the Structure of Graphene Oxide Films at the Air-Water Interface: A Neutron Reflectivity Study

    Year: 2020

    Journal: ACS Appl. Mater. Interfaces, Volume 12, JUN 3, page 25453–25463

    Authors: Lopez-Diaz, D; Merchan, MD; Velazquez, MM; Maestro, A

    Organizations: European Regional Development Fund, ERDF; MINECO [CTQ2016-78895-R]; Junta de Castilla y LeonJunta de Castilla y Leon [SA256P18]; European Union project within the European Commission's Horizon 2020 Research and Innovation programme [731096]

    Keywords: graphene oxide; purified graphene oxide; oxidative debris; Langmuir films; neutron reflectivity

    We address here the role of oxidation impurities on air the structure of graphene oxide films at the air-water interface by water specular neutron reflectivity (SNR). We study films of purified graphene oxide (PGO) and nonpurified graphene oxide in the two layers close-packed state. Nonpurified graphene oxide is constituted by graphene oxide (GO) layers with oxidation impurities adsorbed on the basal plan; while in PGO sheets, impurities are eliminated. SNR measurements show that GO films are formed by well-defined bilayers constituted by 2-3 layers of GO stacked in contact with air and a second layer of impurities submerged in the aqueous subphase. In contrast, PGO films are formed by a single layer in contact with air. We show for the first time that impurities constitute a layer submerged in the aqueous subphase, decrease the elasticity, and favor the collapse of graphene oxide films. Our results allow designing the surface properties of GO trapped at fluid interfaces.
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