Time-resolved Cryo-TEM Analysis
CryoTEM provides unique possibilities for quasi in situ and time-resolved analysis of biomimetic mineralization. In particular, 3D analysis in conjunction with dynamic (time resolved) approach gives new insights in (macro)molecular assembly/disassembly mechanisms and thus becomes an essential tool in nano-chemistry[1].
The plunge-freeze vitrification (plunging the system into melting ethane, T = -183 °C) at various time points, allows the quenching of the reaction and the trapping of the intermediate reaction products at precisely determined stages in the process (Figure 1). This technique yields a solid amorphous film providing a snapshot of the specimen in its solution state since all processes have been arrested[2]. Recent developments in instrumentation and automation have provided reliable and reproducible vitrification methods for the preparation of aqueous specimens for which a time resolution up to 1 ms is expected to become generally available[1].
Figure 1: Schematic representation of the setup for the preparation of cryoTEM samples from a mineralization reaction under a surfactant monolayer[3].
A quasi time resolved cryoTEM study
Figure 2: TEM pictures and SAED patterns of calcium carbonate particles grown under a surfactant in the holes of the TEM grid after reaction times of (A) 30 s, (B) 3 min, and (C) 10 min[3].
With this quasi-time-resolved analysis, we investigated the very early stages of calcium carbonate formation under Langmuir monolayers using cryoTEM in combination with selected area electron diffraction (SAED) (Figure 1 and 2)[3]. In this way, we assessed the evolution of morphology, polymorphic type, and crystallographic orientation of the calcium carbonate formed.
References
- P.M. Frederik, N.A.J.M. Sommerdijk, Spatial and temporal resolution in cryo-electron microscopy - a scope for nano-chemistry, Current Opinion in Colloid & Interface Science 10 (2005) 245-249.
- A. Dey, G. de With, N. Sommerdijk, In situ techniques in biomimetic mineralization studies of calcium carbonate, Chemical Society Reviews 39 [2] (2009) 397-409.
- B.P. Pichon, P.H.H. Bomans, P.M. Frederik, N.A.J.M. Sommerdijk, A quasi-time-resolved CryoTEM study of the nucleation of CaCO3 under Langmuir monolayers, J. American Chemical Society 130 (2008) 4034-4040.