Surface Species in Graphene Liquid Cells for Transmission Electron Microscopy*

The behavior of nanoparticles in liquid is important to a wide variety of fields, from medical to environmental. The aggregation of such particles is an important factor for nanoparticle removal during processes such as water purification. However, due to their size, nanoparticles in solution are difficult to characterize directly by optical or x-ray based methods. An effective method to observe nanoparticles in liquid is using the scanning transmission electron microscope(STEM) combined with graphene-based liquid cells(GLC).
The preparation of GLC’s usually requires wet chemical etching steps which often leave surface species on the etched graphene. This may change the properties of the water-graphene interface depending on the chemicals used for the etching process, and the surface species produced from the reactions. In this contribution we examine the presence of such species using a combination of STEM, energy dispersive x-ray analysis(EDX), and Raman spectroscopy to analyze the molecular species present at the graphene interface in the GLC’s and how certain surface species affect liquid cells containing gold nanoparticles.