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Graphene surface structure in aqueous media : evidence for an air-bubble layer and ion adsorption
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Zhou, Liangzhi, Islas, Luisa, Taylor, Nicholas, Bikondoa, Oier, Robles, Eric and Briscoe, Wuge H. (2019) Graphene surface structure in aqueous media : evidence for an air-bubble layer and ion adsorption. Carbon, 143 . pp. 97-105. doi:10.1016/j.carbon.2018.10.093
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Official URL: https://doi.org/10.1016/j.carbon.2018.10.093
Abstract
Understanding graphene surface structure in aqueous media is essential for its biotechnological applications. Here, using synchrotron X-ray reflectivity (energy 14 keV), AFM imaging, and contact angle measurements, we have investigated the surface structure of CVD graphene on SiO 2 /Si in water and phosphate buffered saline (PBS) at 25-60 ºC. We found a diffuse layer immediately adjacent to graphene with a scattering length density (SLD) of 6.72×10 -6 Å -2 , attributed to the presence of air bubbles on graphene under water. AFM imaging was indicative of interfacial inhomogeneity, but did not provide conclusive topography information on the bubble-covered graphene-water interface. The diffuse layer diminished after the graphene was submerged in water for 24 h at 25 ºC. This is also evident from its enhanced wettability, with the water contact angle on graphene decreasing from 84.9±0.4° to 55.6±0.4° after submergence. An additional layer atop graphene appeared after soaking, with a thickness 10.1 Å, and a higher SLD of 19.5×10 -6 Å -2 at 25 ºC, which increased to 11.8 Å and 21.8×10 -6 Å -2 at 60 ºC in PBS, respectively. We discuss this observation in terms of ion mobility, possible form ation of a silanol layer on the SiO 2 substrate, and water structure disruption at higher temperatures.
| Item Type: | Journal Article | ||||||||||||||||||||||||
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| Subjects: | T Technology > TA Engineering (General). Civil engineering (General) T Technology > TP Chemical technology |
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| Divisions: | Faculty of Science > Physics | ||||||||||||||||||||||||
| Library of Congress Subject Headings (LCSH): | Graphene -- Surfaces, Biotechnology, Ion exchange | ||||||||||||||||||||||||
| Journal or Publication Title: | Carbon | ||||||||||||||||||||||||
| Publisher: | Pergamon | ||||||||||||||||||||||||
| ISSN: | 0008-6223 | ||||||||||||||||||||||||
| Official Date: | March 2019 | ||||||||||||||||||||||||
| Dates: |
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| Volume: | 143 | ||||||||||||||||||||||||
| Page Range: | pp. 97-105 | ||||||||||||||||||||||||
| DOI: | 10.1016/j.carbon.2018.10.093 | ||||||||||||||||||||||||
| Status: | Peer Reviewed | ||||||||||||||||||||||||
| Publication Status: | Published | ||||||||||||||||||||||||
| Access rights to Published version: | Restricted or Subscription Access | ||||||||||||||||||||||||
| RIOXX Funder/Project Grant: |
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