Interfacial Assembly of Graphene Oxide Sheets
Abstract
Scientific interest in graphene oxide (GO) sheets, the product of chemical oxidation and exfoliation of graphite powder, has resurged in recent years because GO is considered a promising precursor for the bulk production of graphene-based sheets for a variety of applications. In addition, GO can be viewed as an unconventional type of soft material as it is characterized by two abruptly different length scales. Its thickness is of typical molecular dimensions, measured to be about 1 nm by atomic force microscopy, but its lateral dimensions are that of common colloidal particles, ranging from nanometers to tens of microns. This high anisotropy leads to interesting fundamental colloidal interactions between the soft sheets which have practical implications in the solution processing and assembly of the material. This research therefore aims to use a variety of techniques to control these inter-sheet interactions to gain an understanding of the processing-structure relationships which ultimately determine the overall properties of the bulk GO assembly. GO is identified as a two-dimensional amphiphile with a unique edge-to-center arrangement of hydrophilic and hydrophobic groups, which has led to the demonstration of its pH- and size-dependent surface activity. The water surface is then utilized, as in the Langmuir-Blodgett technique, as an ideal substrate to tile up the GO sheets and study the interactions between them. Sheet-sheet interaction morphologies were successfully altered between wrinkled and overlapped states by pH tuning of sheet charge density, and the resulting structure-property relationships are explored. In addition, a novel flash-reduction and assembly process is described in which a simple photographic camera flash can rapidly and cleanly turn an insulating, well-stacked GO paper to a more open and fluffy conducting film. Lastly, the use of these research results as educational outreach platforms is highlighted. A variety of outlets, such as YouTube videos, laboratory tours, e-mentoring, and module creation brought this research outside the scientific community to help inspire our next generation of scientists.
- Publication:
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Ph.D. Thesis
- Pub Date:
- 2012
- Bibcode:
- 2012PhDT.......180C
- Keywords:
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- Engineering, Materials Science