Electron Microscopy Group of Materials Science

Research areas

Graphene liquid cells

Liquid cells are used to study liquids in an enclosed environment in the transmission electron microscope (TEM). The encapsulated liquids are isolated from the high vacuum (10-5 Pa) in the TEM. Typically, graphene is used to confine the liquids because of its remarkable properties like high thermal and electrical conductivity. Furthermore, graphene only adds low contrast to the recorded images.

In our lab, we prepare graphene pockets by placing a drop of liquid on a first grid with CVD graphene. Afterwards, we place a second grid with graphene on top, in order to encapsulate the liquid completly. We use the liquid cells to investigate in-situ crystallization, as it was shown in [1] for the quasi 2-dimensional CaSO4 in the anhydrite AII phase.

Figure 1: Graphene pockets with encapsulated liquids are prepared by putting two grids with CVD graphene above each other with a drop of the desired liquid in between. During the evaporation of the liquid, the grids are coming into contact and encapsulate the remaining liquids in pockets.
Figure 2: High-resolution TEM image at 80 kV of CaSO4 in the anhydrite AII phase encapsulated between two layers of graphene which can be seen in the FFT, where the reflections for graphene and the anhydrite are marked with green and red circles , respectively.

[1] Lehnert, T.; Kinyanjui, M. K.; Ladenburger, A.; Rommel, D.; Wörle, K.; Börrnert, F.; Leopold, K.; Kaiser, U. In situ Crystallization of the Insoluble Anhydrite AII Phase in Graphene Pockets. ACS Nano, 2017, 11, 7967-7973

Collaborations

Prof. K. Leopold, Ulm University

Projects / Funding

DFG and MWK Baden-Württemberg in the frame of the SALVE project