Mosaic-like monolayer of graphene oxide sheets decorated with tetrabutylammonium ions

We report the fabrication of mosaic-like monolayers of graphene oxide (G-O) coated with tetrabutylammonium ions (TBA) using a simple spin-coating method. The TBA-coated G-O (TG-O) sheets were prepared by "spontaneous exfoliation" of graphite oxide intercalated with tetrabutylammonium hydroxide (TBAOH) in the wet state, without the need for sonication. Mosaic-like monolayers could be formed on a variety of substrates such as Si wafer (coated with the thin native oxide), SiO2/Si wafer, graphene grown by chemical vapor deposition and then transferred on SiO2/Si wafer, Au film on Si wafer, and Cu foil. The mosaic-like monolayer of TG-O was compared with monolayers of G-O and TG-O prepared using a Langmuir-Blodgett (LB) trough. The formation of the mosaic-like TG-O monolayer films was attributed to (1) weakening of the electrostatic repulsion between G-O sheets by TBA, and (2) prevention of the overlap and stacking of TG-O sheets by disruption of the hydrogen bonding between the basal plane of one sheet and the basal plane or edge of another, by adsorbed TBA. External reflection FTIR spectroscopy showed that spectral features of the mosaic-like monolayer of TG-O made by simple spin-coating were the same as those for the monolayer fabricated using the LB assembly, indicating the same spatial orientations of functional groups. This study provides a very simple route to a complete monolayer of G-O without the need for an LB trough.