Within the scope of this cumulative thesis, four aspects behind oxo-functionalized graphene (oxo-G) and thereout derived graphene (G) were examined: the mechanism behind the formation of oxo-G out of several types of graphite, the control of the size distribution of thus obtained oxo-G nanoparticles, the cell-toxicity of oxo-G and its performance to act as a carrier system for the DNA transport into cells, and finally methods to functionalize oxo-G and G to produce novel materials. This thesis could elucidate unknown material properties and possible application of this outstanding class of carbon based 2D materials in the means of a divers set of analytical tools.