Graphene-oxide films printed on rigid and flexible substrates for a wide spectrum of applications

Structures of films produced from a water-based graphene oxide ink by 2D printing on various substrates, including those of the flexible type, are compared. It was shown that the deposition of a thin polyvinyl alcohol film making substrates hydrophilic leads not only to more uniform application of the ink, but also to a denser film structure with a shallower surface profile. The processing of a graphene-oxide suspension in a blender additionally reduces the particle size of the suspension, which results in improvement of the structure and, on the whole, a shallower surface profile of the film. Comparison of the electrical properties of films on silicon with various coatings hydrophilizing the substrates demonstrated that the properties of the structures strongly depend on the type of coatings, which can change the conductivity type of the silicon substrate and lead to doping of the graphene-oxide film. At graphene-oxide film thicknesses not exceeding 25 nm, noticeable currents ($>$ 1 $\mu$A) appear in the films at voltages higher than 1–1.5V. The graphene-oxide layers are promising for the fabrication of protective and insulating coatings and sensors and, in the case of reduction, for the deposition of transparent electrodes.