Graphene liquid cell allows high-resolution atomic imaging of specimens in liquid

April 10, 2012

Two sheets of graphene encapsulate a platinum growth solution (credit: KAIST)

Scientists can now observe processes occurring in liquid media at a scale less than a nanometer (billionth of a meter).

Korea Advanced Institute of Science and Technology (KAIST) scientists confined an ultra-thin liquid film between layers of graphene, for real-time and in-situ imaging of nanoscale processes in fluids, with atomic-level resolution, by a transmission electron microscope (TEM).

The graphene liquid cell (GLC) is composed of two sheets of graphene sandwiched to create a sealed chamber, where a platinum growth solution is encapsulated in the form of a thin slice. Each graphene layer has a thickness of one carbon atom, the thinnest membrane that has ever been used to fabricate a liquid cell required for TEM.

The research team was able to observe the growth and dynamics of platinum nanocrystals in solution as they coalesced into a larger size, while the graphene membrane with the encapsulated liquid remained intact.

The transmission electron microscope (TEM), first introduced in the 1930s, produces images at a significantly higher resolution than light microscopes, allowing users to examine the smallest level of physical, chemical, and biological phenomena. Observations by TEM with atomic resolution, however, have been limited to solid and/or frozen samples, and thus it has previously been impossible to study the real time fluid dynamics of liquid phases.

TEM imaging is performed in a high vacuum chamber in which a thin slice of the imaged sample is situated, and an electron beam passes through the slice to create an image. In this process, a liquid medium, unlike solid or frozen samples, evaporates, making it difficult to observe under TEM.

Ref. J. M. Yuk et al. High-Resolution EM of Colloidal Nanocrystal Growth Using Graphene Liquid Cells. Science, 2012; 336 (6077): 61 DOI: 10.1126/science.1217654