Described as 'polymer carpets' by the team, the structure is highly stable and is less prone to degradation over time and could prove very promising in the development of flexible organic electronics. Also, if a layer of molybdenum disulfide is added over the 'nanocarpet', the resulting structure generates current under exposure to light
Graphene is durable, light and an electrically conductive carbon material and can be used for manufacturing solar batteries, smartphone screens and thin and flexible electronics.
Graphene should be integrated into complex structures to be used successfully, but that is challenging. According to scientists while graphene is stable, it reacts poorly with other compounds. In order to make it react with other elements graphene is usually, at least, partially destroyed but this degrades the properties of the materials obtained.
Professor Raul D. Rodriguez from the Research School for Chemistry & Applied Biomedical Sciences says: “When functionalizing graphene the unique properties of graphene are lost. Therefore, we decided to follow a different path.
“In graphene, there are inevitable nanodefects, for example, at the edges of graphene and wrinkles in the plane. Hydrogen atoms are often attached to such defects. It is this hydrogen that can interact with other chemicals.”
To modify graphene, the authors used thin metal substrates on which a graphene single-layer is then placed. The graphene is then covered with a solution of bromine-polystyrene molecules. The molecules interact with hydrogen and are attached to the existing defects, resulting in polyhexylthiophene (P3HT). Further exposed to light during the photocatalysis, a polymer begins to 'grow'.
"In the result, we obtained the samples with a structure that resembles 'polymer carpets' as we call them in the paper. Above such a 'polymer carpet' we placed molybdenum disulfide. Due to a unique combination of materials, we obtained a 'sandwich' structure' that functioned like a solar battery. That is, it generated current when exposed to light. In our experiments a strong covalent bond is established between the molecules of the polymer and graphene, that is critical for the stability of the material obtained," noted Rodriguez.
While the method for graphene modification creates a very sturdy compound it is simple and cheap to create and the method used is versatile because it makes growing very different polymers directly on graphene possible.
“The strength of the obtained hybrid material is achieved additionally because we do not destroy graphene itself but use pre-existing defects, and a strong covalent bond to polymer molecules. This allows us to consider the study as promising for the development of thin and flexible electronics when solar batteries can be attached to clothes, and when deformed they will not break,” the professor explained.
The study results were published in Journal of Materials Chemistry C.