Since its discovery, there has been tremendous interest in graphene, an atom-thick sheet of carbon with impressive electrical and mechanical properties. It could potentially serve as a basis for future electronics, but is not the easiest material to work with currently. For one thing, trying to build up molecular structures on it is difficult because of graphene's symmetry, but researchers at Nagoya University have found a solution.
If you were to look at graphene, it resembles chicken wire with its hexagonal pattern, which creates a problem as it has three-fold symmetry, making those three axes thermodynamically equivalent. If you want to grow structures on a graphene sheet, the molecules you deposit equally like being on any of these axes. While working with sodium dodecyl sulfate (SDS) the researchers discovered they could control the direction it would form ribbon-like structures in. It is already known to form these structures, but they grow where they wish. After injecting SDS onto the graphene surface, the researchers used an atomic force microscope (AFM) to scan it and confirm random adsorption (which is different from absorption) of the SDS. Fifteen minutes later the surface was scanned again, but now the SDS had changed their orientation.
After some more work, the researchers discovered the AFM scanning the surface caused the SDS molecules to remove themselves from their original position to and then rotate to match the scanning orientation. The more extreme the angle between the AFM scan the direction, the more easily the SDS molecules rotated and moved, while those with a smaller different changed less and acted as seed molecules for the others. This ability to control the orientation of these ribbons could lead to several advances in many fields that work with two-dimensional materials, and could even help lead to graphene-based electronics.
Source: Nagoya University
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