Abstract
The work presented in this PhD thesis can be divided into two main categories: 1) Syn-thesis and Langmuir-Blodgett assembly of graphene derivatives and 2) Application and characterization of graphene derivatives as an interface material in molecular electron-ics. While the first category could be divided further, the synthesis and Langmuir-Blodgett results are intertwined in such a way that it would be more confusing to pre-sent them separately. The Langmuir-Blodgett deposition also played a crucial, but more isolated, part in the investigation of graphene derivatives as interface material.
Solution processable graphene in the form of chemically derived graphene has been synthesized through the modified Hummers method with subsequent reduction into reduced graphene oxide with hydrazine. The completeness of oxidation, the effect of the refinement steps and the reduction of the graphene oxide were investigated using the Langmuir-Blodgett technique. It was found that reduction of graphene oxide back into graphene did not seem possible in solution, while still maintaining its monolayer character. Instead, an alternative route for graphene synthesis was then designed. This involved immobilization of the monolayered graphene oxide via the Langmuir-Blodgett deposition technique prior to a three step reduction scheme involving hydrazine reduc-tion, sulfuric acid de-oxygenation, and thermal annealing. This method resulted in wrin-kle-free reduced graphene oxide with a negligible oxygen content (< 0.5 wt%). Addition-ally, it was shown that the conductivity of our chemically modified graphene is limited by structural defects rather than residual oxygen groups.
By using the Langmuir-Blodgett technique, graphene oxide has been demonstrated to work as a stabilizing interface material between organic thin films and metal top elec-trodes, thereby preventing structural reorganization and metal penetration. By develop-ing a molecular test bed and incorporation of graphene oxide into vertical functional devices it was shown that graphene oxide can prevent shorts in a metal-molecule-graphene oxide-metal sandwich configuration, while functioning as a molecularly thin temperature independent tunnel barrier.
Additionally, graphene oxide has been shown to self-assemble at the air-water interface into millimeter large mosaic films in the presence of cadmium(II) ions in the subphase
Solution processable graphene in the form of chemically derived graphene has been synthesized through the modified Hummers method with subsequent reduction into reduced graphene oxide with hydrazine. The completeness of oxidation, the effect of the refinement steps and the reduction of the graphene oxide were investigated using the Langmuir-Blodgett technique. It was found that reduction of graphene oxide back into graphene did not seem possible in solution, while still maintaining its monolayer character. Instead, an alternative route for graphene synthesis was then designed. This involved immobilization of the monolayered graphene oxide via the Langmuir-Blodgett deposition technique prior to a three step reduction scheme involving hydrazine reduc-tion, sulfuric acid de-oxygenation, and thermal annealing. This method resulted in wrin-kle-free reduced graphene oxide with a negligible oxygen content (< 0.5 wt%). Addition-ally, it was shown that the conductivity of our chemically modified graphene is limited by structural defects rather than residual oxygen groups.
By using the Langmuir-Blodgett technique, graphene oxide has been demonstrated to work as a stabilizing interface material between organic thin films and metal top elec-trodes, thereby preventing structural reorganization and metal penetration. By develop-ing a molecular test bed and incorporation of graphene oxide into vertical functional devices it was shown that graphene oxide can prevent shorts in a metal-molecule-graphene oxide-metal sandwich configuration, while functioning as a molecularly thin temperature independent tunnel barrier.
Additionally, graphene oxide has been shown to self-assemble at the air-water interface into millimeter large mosaic films in the presence of cadmium(II) ions in the subphase
| Original language | English |
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| Publisher | Department of Chemistry, Faculty of Science, University of Copenhagen |
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| Number of pages | 128 |
| Publication status | Published - 2013 |