Stable Dispersion of Graphene Synthesis
Taj Johnson, Cornell College, Physics Major
Mentored by Dr. Arjun Nepal
What is Graphene?
Graphene is a very thin sheet of carbon bonded in a hexagonal shape. True graphene is only an atom thick, but due to the difficulty of obtaining true graphene, there’s another type called multi-layer graphene. Multilayer graphene maintains most of graphene’s useful properties but too many layers make graphene into graphite.
Graphene has many properties: its high strength, its great conductivity, and its light weight are just a few. This material is very useful, but it is hard to work with as a powder. By dispersing it in a liquid, for this experiment it was Deionized (DI) water, it becomes easier to manage.
Experiment
Graphene does not dissolve in water by itself. Polystyrene Sulfonate (PSS) is used because it is a non-toxic surfactant capable of dispersing graphene. To use the PSS, it was dissolved in DI water with the PSS being 30% of the mass of the new PSS solution.
We used trial and error to figure out when graphene would disperse in DI water. First the graphene and PSS are measured and poured into a vial. The PSS solution is measured in percentage by volume of the solution it will be poured into. Next, they are mixed with a sonicator for 30 minutes. When the sonication is complete the vials are quickly taken out and let sit for a significant amount of time, typically close to 24 hours. When the time is up, it is checked for clumping. If a sample showed no clumps or low settlement on the bottom of the vial, it is considered a good sample.
Experimental Results
Below shows that 3mg per ml of graphene with 2% PSS was the best solution with the highest amount of graphene dispersed.
Fig. 1. Each point is tested using 30% PSS by mass in DI water. The black points are the samples that dispersed longer; the red points are samples that showed significant settlement.
Acknowledgements
I would like to thank Arjun Nepal for giving me the opportunity to research this project. I will also mention Shushil Sidgel for guiding me with how to use the tools in the laboratory. I appreciate all that Loren Greenman, JT and finally Kim Coy for putting the program together. I am grateful that the National Science Foundation provided funding for this program.