Graphene Oxide (GO) is not functionalised GO

Reduce GO (RGO) is not functionalised GO

Where as, functionalisation means functionalised with any one of carboxylic acid, tertiary alcoholic, epoxide, primary alcoholic or primary amino groups

graphene oxide isn't functionalized graphene. Indeed It has some oxygenous groups on it's surface, but it's a whole other material than graphite. The characteristics are different, albeit not in every aspect. So it is not right to call GO a functionalized graphite

Only reduced graphene oxide (RGO) counts as functionalized graphene, as after reduction of graphene oxide (GO) you end up restoring most of the characteristics that classify it as graphene (e.g. Raman spectra), including -at least partially- its 2D structure. GO on the other hand is too wrinkled (due to all the oxygenated groups decorating the plane) to assume a true 2D formation. RGO has most of its 2D plane restored depending on the degree of reduction (different methods produce different results). This indeed has been a topic for debate, but it has been settled. For more information look at the Review article below:

http://carbon.imr.ac.cn/file/journal/2012/1330650409921.pdf

Graphene Oxide (GO) is not functionalised GO

Reduce GO (RGO) is not functionalised GO

Where as, functionalisation means functionalised with any one of carboxylic acid, tertiary alcoholic, epoxide, primary alcoholic or primary amino groups

Graphene oxide is not functionalized Graphene. Only if graphene gains certain functions by chemical or physical modification, it can be called functionalized.

Not only

Graphene Oxide (GO) is not functionalized GO

and also Reduce GO (RGO) is not functionalized GO

Are wrong terms, but also

Neither Graphene Oxide (GO) is functionalized graphite

Nor

Reduce GO (RGO) is functionalized graphite

So, based on ubiquitous literature : Functionalization is the process of adding new functions, features, capabilities, or properties to a material by changing the surface chemistry of the material, I believe that in term of "meaning and chemical concept" calling graphene oxide as functionalized graphene is wrong and might better to say that:

Graphene Oxide (GO) is the -COOH functionalization of graphite

Or

Graphene Oxide (GO) is the -COOH functionalized graphite.

Thanks