Search

Abstract: Bioinspired materials design aims for high‐performing composite materials based on natural biomineralization processes and biomineral architectures. A key component to the research is the bioorganic–inorganic interface, one of the most crucial parameters for controlling the material properties. In this study, genetically engineered phages expressing an inorganic‐binding peptide for the molecular recognition of a ceramic material is exploited to generate thin film multilayer assemblies, with the phage template as minority component. The bioorganic–inorganic interface in the ceramic (zinc oxide, ZnO) multilayer systems is strengthened by the ZnO‐binding motif HSSHH of a peptide to increase Young's modulus and hardness. Applying a point‐mutated version of the peptide, DSSHH, which modulates the interface forces, shows an increased fracture toughness without deteriorating the Young's modulus and the hardness. Molecular matching of the organic phase and its modulation in order to form a specific interface is shown to be important in controlling material properties like in natural biominerals. With this tool in hand, it is not only possible to imitate the structure of biominerals but also to genetically control the molecular recognition of bioorganic molecules to induce macroscopic effects in synthetic composite materials. [ABSTRACT FROM AUTHOR]

A series of Ba1−xEuxTiO3−δ (0.1 ≤x≤ 0.9) phases with ∼40 nm particle size were synthesized via a Pechini method followed by annealing and sintering under a reducing atmosphere. The effects of Eu2+ substitution on the BaTiO3 crystal structure and the thermoelectric transport properties were systematically investigated. According to synchrotron X-ray diffraction data only cubic perovskite structures were observed. On the local scale below about 20 Å (equal to ∼5 unit cells) deviations from the cubic structure model (Pm3̅m) were detected by evaluation of the pair distribution function (PDF). These deviations cannot be explained by a simple symmetry breaking model like in EuTiO3−δ. The best fit was achieved in the space group Amm2 allowing for a movement of Ti and Ba/Eu along 〈110〉 of the parent unit cell as observed for BaTiO3. Density functional calculations delivered an insight into the electronic structure of Ba1−xEuxTiO3−δ. From the obtained density of states a significant reduction of the band gap by the presence of filled Eu2+ 4f states at the top of the valence band was observed. The physical property measurements revealed that barium–europium titanates exhibit n-type semiconducting behavior and at high temperature the electrical conductivity strongly depended on the Eu2+ content. Activation energies calculated from the electrical conductivity and Seebeck coefficient data indicate that at high temperatures (800 K ＜ T ＜ 1123 K) the conduction mechanism of Ba1−xEuxTiO3−δ (0.1 ≤x≤ 0.9) is a polaron hopping when 0 ＜ x≤ 0.6 and is a thermally activated process when 0.6 ＜ x ＜ 1. Besides, the thermal conductivity increases with increasing Eu2+ concentration. Due to a remarkable improvement of the power factor, Ba0.1Eu0.9TiO3−δ showed a ZT value of 0.24 at 1123 K. [ABSTRACT FROM AUTHOR]

The distinct electronic properties, including p-type semiconducting and a wide optical band gap, renders SnO suitable for applications such as microelectronic devices, gas sensors and electrodes. However, the synthesis of SnO is rather challenging due to the instability of the oxide, which is usually obtained as a by-product of SnO 2 fabrication. In this work, we developed a bioinspired synthesis, based on a hydrothermal approach, for the direct production of SnO nanoparticles. The amount of mineralizer, inducing the precipitation, was identified, which supports a template-free formation of the nanosized SnO particles at low temperature and mild chemical conditions. Moreover, the SnO nanoparticles exhibit a shape of unique three-dimensional crosses similar to the calcite crosses present in the calcareous sponges. We demonstrated that SnO crosses are evenly distributed and embedded in an organic scaffold by an ice-templating approach, in this way closely mimicking the structure of calcareous sponges. Such scaffolds, reinforced by an active material, here SnO, could be used as filters, sensors or electrodes, where a high surface area and good accessibility are essential. This article is part of the theme issue 'Bioinspired materials and surfaces for green science and technology (part 2)'.

A series of Ba 1-x Eu x TiO 3-δ (0.1 ≤ x ≤ 0.9) phases with ∼40 nm particle size were synthesized via a Pechini method followed by annealing and sintering under a reducing atmosphere. The effects of Eu 2+ substitution on the BaTiO 3 crystal structure and the thermoelectric transport properties were systematically investigated. According to synchrotron X-ray diffraction data only cubic perovskite structures were observed. On the local scale below about 20 Å (equal to ∼5 unit cells) deviations from the cubic structure model (Pm3[combining macron]m) were detected by evaluation of the pair distribution function (PDF). These deviations cannot be explained by a simple symmetry breaking model like in EuTiO 3-δ . The best fit was achieved in the space group Amm2 allowing for a movement of Ti and Ba/Eu along 〈110〉 of the parent unit cell as observed for BaTiO 3 . Density functional calculations delivered an insight into the electronic structure of Ba 1-x Eu x TiO 3-δ . From the obtained density of states a significant reduction of the band gap by the presence of filled Eu 2+ 4f states at the top of the valence band was observed. The physical property measurements revealed that barium-europium titanates exhibit n-type semiconducting behavior and at high temperature the electrical conductivity strongly depended on the Eu 2+ content. Activation energies calculated from the electrical conductivity and Seebeck coefficient data indicate that at high temperatures (800 K < T < 1123 K) the conduction mechanism of Ba 1-x Eu x TiO 3-δ (0.1 ≤ x ≤ 0.9) is a polaron hopping when 0 < x ≤ 0.6 and is a thermally activated process when 0.6 < x < 1. Besides, the thermal conductivity increases with increasing Eu 2+ concentration. Due to a remarkable improvement of the power factor, Ba 0.1 Eu 0.9 TiO 3-δ showed a ZT value of 0.24 at 1123 K.