Abstract: The present invention relates a mixed functionalized graphene structure comprising a graphene surface; 1-pyrenebutanoic acid succinimidyl ester (PBASE) molecules; molecules of at least one type of polycyclic aromatic hydrocarbon (PAH) compounds; and biomolecules; wherein both the molecules of PBASE and the molecules of at least one type of PAH compounds are non-covalently linked to the graphene surface, wherein the biomolecules are linked to the PBASE molecules, and wherein the mixed functionalized graphene structure has a surface roughness (Rms) between around 0.01±1.00 ?m and around 0.25±1.00 ?m respect to the surface roughness (Rms) of non-functionalized graphene, wherein Rms is measured by atomic force microscopy (AFM). The present invention relates also to a method for preparing said mixed functionalized graphene structure, to a functionalized graphene structure obtainable by said method.