Preparation of Catalyst Samples for TEM

Grids with carbon films are widely used, and among the advantages is the high thermal and electrical conductivity. This feature helps to reduce the thermal expansion and loading effects during exposure of the sample to the electron beam [10]. It is important that the material is deposited on a thin film transparent to electrons the thickness may vary from about 10 to 30 nm, depending on the manufacturer. 

For high-resolution TEM analysis, the most appropriate materials are holes in the range of about 0.2-10 pm, which reduces the absorption and scattering of the electron beam and help to improve the quality of the signal. For particles with little contrast, holey films coated with an extra layer, ultrathin of carbon can improve the quality of images. The so-called lacey films are quite recommended for electron diffraction images [31]. 

The correct preparation of the sample and the use of adequate grids to support the material for analysis are important for observing two-dimensional images with high quality and resolution. However, an alternative is the ultramicrotome. The particles are embedded in a polymer resin and cut in thin sections of about 20 nm with a diamond knife. It is specially recommended for zeolite materials. The observation of these thin sections allows to observe the internal morphology of the particles and the dispersion of metals on the microporous structure material [32]. 

The careful choosing of the appropriate method of sample preparation is very important. Proper sample preparation is one of the key points for successful analysis of materials by electronic microscopy. 

Acknowledgments Thanks to Carlos Andre Perez, Ruth Leibson Martins, Deborah Vargas, Lidia 

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