Objectives

Soft Matter CryoTEM

'Soft Matter', i.e. polymers, hybrid coatings, nanocomposites and biomedical materials, forms an important research area with many important applications. With the rapid developments in the field of nanotechnology and macromolecular self-assembly, the demand for nanoscopic imaging of Soft Matter increased tremendously. TEM is virtually the only technique by which the structure and morphology of Soft Matter can be analyzed at the nanometer level.

In particular for soft materials, the exposure to an electron beam can cause damage to the specimens during the imaging process. Moreover, the investigation of structures in solution traditionally involved drying and staining steps, again leading to artifacts in the investigated sample. The use of cryogenic TEM, (cryo-TEM) and the associated low dose imaging protocols not only limit specimen damage caused by the electron beam, it also allows solution specimens to be analyzed a near-native vitrified state providing both 3D and time resolved information.

The Aim of the Center

The aim of the Center is to boost the structural analysis of “soft materials” at a nano-meter level. We concentrate on the physico-chemical characterization of (macro)molecular assemblies and inorganic structures in solutions as well as at soft-hard interfaces. Using 3D and time resolved imaging in combination with structural and chemical characterization we can analyze such nano-structured materials in detail but also monitor their formation mechanisms. It is our conviction that only a precise understanding of the assembly mechanisms can lead us to the design of functional, nanoscopically structured materials with predetermined properties.

The Center's Tools

The cryoTEM analysis requires sample preparation and analysis to be performed at cryogenic temperatures [1]. By vitrification in a suitable coolant (e.g. by plunge freezing in liquid ethane) molecular movements are arrested, and the structure of the specimen is preserved such that it can be observed in its native state. To control the temperature and the solvent saturation level we use a vitrification robot (VitrobotTM) often in combination with a glovebox [2].

In particular for high-resolution 3D analysis of nano-structures and self-organizing systems, we have introduced (cryo)electron tomography [3]. We now extend this to a combination with with typical material science techniques such as EELS, Z-contrast imaging, lattice imaging and diffraction. With the latest updates on hardware and software provided by FEI company, imaging of micrometer samples is now also done using batch tomography, and dual axis (cryo) tomography.

References
  1. H. Friedrich, P.M. Frederik, G. de With, N.A.J.M. Sommerdijk, Imaging of self-assembled structures: Interpretation of TEM and Cryo-TEM images, Angewandte Chemie, International Edition, 49 [43] (2010) 7850-7858.
  2. M.R.J. Vos, P.H.H. Bomans, P.M. Frederik, N.A.J.M. Sommerdijk, The development of a glove-box/Vitrobot combination: Air-water interface events visualized by cryo-TEM, Ultramicroscopy 108 (2008) 1478-1483.
  3. F. Nudelman, G. De With, N. A.J.M. Sommerdijk, Cryo-electron tomography: 3-dimensional imaging of soft matter, Soft Matter, Advanced article, (2011), in press.