Cryo-direct imaging

Three different techniques, namely FFEM [20, 22], Cryo-Direct Imaging (Cryo-DI) [104] and freeze-fracture direct imaging (FFDI) [105], can be used to visualise the structure of micro emulsions. In FFEM the samples are prepared in a protected fashion in a sandwich. They are then rapidly frozen, fractured, shadowed with metal, and replicated with a thin carbon film. The replica of the fractured surface, the morphology of which is controlled by the sample s microstructure, is then studied by a TEM. In contrast to FFEM, in Cryo-DI thin films of the sample are rapidly frozen but immediately, without replication, trans-... 

Goldraich M, Talmon Y (2000) Direct-imaging cryo-transmission electron microscopy in the study of colloids and polymer solutions. In Alexandridis P, Lindman B (eds) Amphiphilic block copolymers self assembly and applications. Elsevier, Amsterdam... 

The evolution of the solution microstructures during the formation of the hexagonal mesoporous material SBA-15 was studied by direct imaging and freeze-fracture replication cryo-TEM.[72] A continuous transformation from spherical micelles, into threadlike micelles, which become longer and stiffer, followed by the formation of bundles with dimensions similar to those found in the final material, was observed. The direct imaging... 

Belkoura, L., Stubenrauch, C. and Strey, R. (2004) Freeze fracture direct imaging A hybrid method in preparing specimen for Cryo-TEM. Langmuir, 20, 4391—4399. 

Ponsinet, V. and Talmon, Y. (1997) Direct imaging of lamellar phases by cryo-transmission electron microscopy. Langmuir, 13, 7287-7292. 

This unique phase was detected also by cryo-TEM, which provides direct structural symmetry information. The cryo-TEM image of the Ql sample exhibited highly ordered domains with cubic symmetry (arrows in the image) and was further confirmed by the fast Fourier transformations (EFT) (Eigure 4.10 [28]). The FFT transformations were fitted to the bcc or fee lattices, with points a, h, and c in the figure indexed as (2 0 0), (1 1 0), and (2 2 0) for the bcc structure, or (2 2 0), (0 2 0), and (0 4 0) for the fee phase. The lattice parameter was found to be 103 2A. 

Figure 2 Cryo-SEM images of the gel of 2 (8 mM, water/THF mixture (80 20)) at different magnifications, (a) Nanoporous structure inset vial inversion test, (b) Image at higher magnification showing the three-dimensional network of nanofibers. The smallest fibers are abont 6.1 nm in diameter (yellow arrow), (c) Whirls with diameters of 10-15(xm. (d) Directional arrangement of fibers within a microstream in the gel. (Reproduced from Ref. 9. American Chemical Society, 2009.)...

D. Danino and Y. Tahnon, Direct-Imaging and Freeze-Fracture Cryo-Transmission Electron Microscopy of Molecular Gels, ChaptCT 9 in Molecular Gels, Materials with... 

Finally, a novel technique is freeze-fracture direct imaging, where sensitive samples such as microemulsions can be studied without the need for a replica. This technique does not have a blotting step (as per cryo-TEM) that can damage micioemulsion structures (Belkoura et al, 2004 Gradzielski, 2008). 

Belkoura, L, StubenrauchC and Strey R. 2004. Freeze fracture direct imaging A new freeze fracture method for specimen preparation in cryo-transmission electron microscopy. Langmuir 4391-4399. 

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