Nacre-like TiO 2 - and ZnO- Based Organic / Inorganic Hybrid Systems
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1007-S07-03
Nacre-like TiO2 - and ZnO - Based Organic / Inorganic Hybrid Systems Zaklina Burghard1, Luciana Pitta Bauermann1, Aleksandar Tucic2, Lars P. H. Jeurgens2, Vesna Srot2, Paul Bellina2, Peter Lipowsky2, Rudolf C. Hoffmann2, Elazar Gutmanas3, Joachim Bill1, and Fritz Aldinger2 1 Institut für Nichtmetallische Anorganische Materialien, Universität Stuttgart, Stuttgart, 70569, Germany 2 Max-Planck-Institut für Metallforschung, Stuttgart, 70569, Germany 3 Technion - Israel Institute of Technology, Haifa, 32000, Israel ABSTRACT A bioinspired approach combining chemical bath deposition (CVD) of oxides with layerby-layer (LBL) assembly of organic polymers has been used to prepare two different types of organic/inorganic multilayer composite films, whose morphology resembles that of naturally occurring nacre. Both process steps allow for a precise control of the layer thickness, thus enabling to tailor the architecture of the multilayer composites. The first type of composite films comprised of TiO2 layers, separated by organic interlayer composed of several oppositely charged polyelectrolytes, while the second type of composite films contained ZnO as the inorganic and poly (amino acids) as the organic component. AFM investigations revealed a granular structure of the inorganic layers which originates from the oxide particles. TEM investigation disclosed that the TiO2 particles are amorphous, while the ZnO particles are crystalline. Moreover, TEM cross-sectional analysis of the composite films confirmed the presence of inorganic layers that are well-separated by organic layers, although signatures of partial interpenetration have been observed at the interfaces. The hardness and Young's modulus of both types of composite films, as determined by nanoindentation testing, increased in comparison to the monolithic oxide films. The enhanced mechanical performance underlines the effectiveness of combining layers of different shear moduli into an alternate architecture. INTRODUCTION The outstanding mechanical performance of naturally occurring nacre, which originates from its highly regular structure comprised of alternating layers of aragonite platelets separated by thin organic layers such as proteins and polysaccharides [1-5], has inspired efforts to implement this design principle into artificially made composites [6]. Nacre-like architectures display an excellent combination of stiffness, strength and impact resistance, as well as a thousand-fold increase in toughness over its constituent materials [7]. To date, a range of biomimetic advanced materials [8-10] and organic-inorganic composites [11-13] have been developed following the guideline of nacre and other hard biological tissues. One particularly useful bioinspired synthesis route is the chemical-bathdeposition (CBD) method which bears similarities with the formation of natural organicinorganic nanocomposites via biomineralization [14]. Accordingly, through the combination of CBD with electrostatic assembly, compact composite films in which oxide layers are sep
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