Graphene derivatives are expected to be crucial for finding new properties beyond pure graphene. Selectively sensing of molecules or macromolecules is one exciting example. However, the chemical toolbox giving control over the type and degree of functionalization of graphene, on the single layer level, is far from being developed and understood. Functionalization of graphene by oxo-addends is one possibility to provide soluble graphene. With that oxo-functionalized graphene, post-functionalization reactions can be studies without the reactivity being influenced by defect sites, as it is the case for graphene oxide, a class of materials that’s properties is dominated by defects. We demonstrate in selective examples controlled chemistry of oxo-functionalized graphene, with respect to the degree of functionalization, the ability to form graphene with very little defects and the performance in devices. One example will be about the storage of charge, and therefore information, in an oxo-functionalized graphene composite that was formed by exploiting the electrostatic interaction of alkylammonium ions and sulfatesters bound on the surface of the graphene material. In this special example the benefit of controlled chemistry ,combined with state-of-the-art analysis, will be demonstrated.