High-resolution low-voltage TEM for imaging the process of mineralization at the TMV/inorganic interface: Towards understanding the mechanical properties of bio/inorganic multilayer systems

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Biomineralization is the natural process of construction and induration of tissues, which outmatch several synthesized products in their physical and chemical properties. Appreciably, one tries to synthesize comparable technical relevant hybrid materials by bio-inspired mineralization. In the existing project we would like to contribute to a better understanding of the mechanism of protein based mineralization of zinc sulfide (ZnS) and zinc oxide (ZnO) on the biotemplate tobacco mosaic virus (TMV) by imaging the organic/inorganic glue line with high-resolution. The obtained insights will help to control the structure of this boundary surface, which are essential for synthesis of nano-sized functional material with tailored properties.Toward the commonly used techniques to image organic materials by negative staining of the specimen, which leads to resolutions in the range of several nanometer or embedding them in vitrified ice with a resolution up to 0.4 nm at acceleration voltages of 300 kV, we count on our newly developed low-voltage transmission electron microscope (TEM) available in spring 2016 to image the surface boundary. High resolution images of the glue line at acceleration voltages of 20-80 kV is possible due to not only spherical but also chromatic aberration correction of the objective lens. In the frame of this project elaborate sample preparation methods like graphene-sandwiching and/or deuterating the specimen will be investigated to image the organic/inorganic boundary surface. Additionally, a further goal of this project is to reveal in situ if the bio-inspired mineralization begins with heterogeneous or homogenous nucleation.In preliminary work of the Stuttgart group, mineralization procedures for selective deposition of ZnS and ZnO on tobacco mosaic virus (TMV) were accomplished. In the frame of this project multilayered nacre-like structures (MLS) on the base of TMV/ZnS and TMV/ZnO, respectively will be produced and investigated. The mechanical properties investigations of ZnO-based MLS with wildtype (wt) TMV (wt-TMV/ZnO) and the TMV mutant TMV_Cys (TMV_Cys/ZnO) and therefore with additional thiols in the boundary surface revealed that the MLS containing the mutant showed an increase in hardness compared to wt-based one. Those MLS will also be imaged with our low-voltage TEM to analyze ultrastructural disparity of the protein-mineral-boundary surface and to correlate that with mechanical properties. To gain an insight with the TEM into the mineralization at the surface as well as in the inner channel of the virus it is additionally planned to assemble small virus-like particles (VLP) and mineralized them in vertical oriented arrays.