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Chemical vapor deposition of graphene nanostructures
While the successful fabrication and characterization of the inherently two-dimensional graphene has pioneered a host of research into other two-dimensional materials, many of the most promising implementations of graphene involve sculpting it in three dimensions. Chemical vapor deposition (CVD) is a prominent graphene fabrication method due to the high degree of control over the quality of the resulting graphene. However, almost no research has been done exploring the processes and products of CVD of graphene on three-dimensional nanostructured catalyst, likely because nanostructures are limited from high temperature processes due to their decreased thermal stability. This is a serious void in the current research because the high quality of CVD-derived graphene coupled with the ability to very precisely control the morphology of the template could result in graphene structures with superlative properties and numerous uses. In this work, CVD is used to grow three-dimensional coatings of graphene on slanted columnar thin films (SCTFs), a material that is currently being explored for use as a chemical sensor based on birefringence changes upon adsorption. The chief drawback of SCTF-based sensors is their non-selective response to chemical adsorption, which can be remedied by adding coating of CVD graphene that allows functionalization with analyte specific binders. In order to perform CVD on nanostructures under temperatures at which the morphology of the nanostructures is maintained, acetylene is preferable to the more conventional methane as the hydrocarbon precursor due to its higher reactivity. Furthermore, it is found that graphene grown at lower temperatures can thermally protect the nanostructures from damage at higher temperatures. This enables a high-quality graphene coating to be grown over SCTFs at higher temperatures, which was then characterized optically by Mueller matrix ellipsometry. By growing a layer of carbon nanotubes (CNTs) at the interface of the SCTF and the substrate, the resulting solution-stable CNT-SCTF hybrid was able to be used for in-situ ellipsometry to monitor the functionalization of the SCTFs by pyrene attachment to the graphene coating. This demonstrates both the ability to functionalize the graphene/SCTF hybrid with analyte-specific binders, and the proof-of-concept design of an optical sensor based on graphene-coated SCTFs.
Wilson, Peter M, "Chemical vapor deposition of graphene nanostructures" (2015). ETD collection for University of Nebraska - Lincoln. AAI3738930.