Johannes Birkenstock's research while affiliated with Universität Bremen and other places

Publications (29)

Article
Na1/2Bi1/2TiO3 (NBT) with varying Bi content has gained significant interest as a potential new material for solid-oxide fuel cells and oxygen separation membranes because of its excellent oxygen-ion conductivity. In this work, the effect of varying Bi content in NBT ceramics of compositions Na1/2BixTiO2.25+1.5x, where x = 0.485–0.510, on the tempe...
Article
The spinel LiMn2O4 (LMO) is a promising cathode material for rechargeable Li-ion batteries due to its excellent properties, including cost effectiveness, eco-friendliness, high energy density, and rate capability. The commercial application of LiMn2O4 is limited by its fast capacity fading during cycling, which lowers the electrochemical performanc...
Article
Full-text available
Single crystals of ABW-type CsAlTiO4 (CAT), CsFeTiO4 (CFT), CsGaTiO4 (CGT), and ANA-type CsTi1.1Si1.9O6.5 (CST) were grown and characterized by electron microprobe analyses, single-crystal X-ray diffraction, thermal analyses, and spindle-stage optical investigations to determine the electronic polarizability of 4-coordinated Ti⁴⁺, α([4]Ti⁴⁺). The c...
Article
Full-text available
A single crystal (∼ 20 µm × 20 µm × 330 µm) of mullite-2c, a natural polytype of mullite, was separated from a radially grown cluster of acicular crystals from Ettringer Bellerberg (Quarternary Eifel volcanic fields, Germany). The chemical composition determined from electron microprobe analysis (EMPA) is Na0.01Mg0.05Al8.52Fe0.293+Si3.13Ti0.02O19.5...
Article
The controlled dissolution kinetics of iron‐doped copper oxide nanoparticles are applied in targeted nanomedicine. In their Research Article (DOI: 10.1002/anie.201912312), L. Mädler, S. J. Soenen et al. present a model‐based approach for adjusting the dissolution kinetics and intracellular release of copper that opens a therapeutic window for cance...
Article
Die kontrollierte Auflösungskinetik Eisen‐dotierter Kupferoxid‐Nanopartikel wird in der gezielten Nanomedizin eingesetzt. In ihrem Forschungsartikel (DOI: 10.1002/ange.201912312) stellen L. Mädler, S. J. Soenen et al. einen Modell‐basierten Ansatz zur Anpassung der Auflösungskinetik und interzellulären Freigabe von Kupfer vor, der neue Krebstherapi...
Article
The progress in nanomedicine (NM) using nanoparticles (NPs) is mainly based on drug carriers for the delivery of classical chemotherapeutics. While low NM delivery rates limit therapeutic efficacy, an entirely different approach was investigated. A homologous series of engineered CuO NPs was designed for dual purpose (carrier and drug) with a direc...
Article
Full-text available
The progress in nanomedicine (NM) using nanoparticles (NPs) is mainly based on drug carriers for the delivery of classical chemotherapeutics. While low NM delivery rates limit therapeutic efficacy, an entirely different approach was investigated. A homologous series of engineered CuO NPs was designed for dual purpose (carrier and drug) with a direc...
Article
The development and industrial application of advanced lithium-based energy storage materials are directly related to the innovative production techniques and the usage of inexpensive precursor materials. The Flame spray pyrolysis (FSP) is a promising technique that overcomes the challenges in the production processes such as scalability, process c...
Article
Full-text available
Single crystals of B2O3 are needed for the precise determination of the refractive indices used to calculate the electronic polarizability α of 3-coordinated boron. The α(B) values in turn are used to predict mean refractive indices of borate minerals. Since the contribution of boron to the total polarizability of a mineral is very low, the synthet...
Article
A crystal of BaCaBO3F was grown by the Czochralski method. It shows a phase transition at 242.7 °C upon cooling where the hexagonal high-temperature modification is transformed to a monoclinic low-temperature form (space group C2, a = 17.8779(8) Å, b = 9.0596(4) Å, c = 12.9735(5) Å, β = 118.875(13)°, V = 1840.03(22) ų, Z = 18). The monoclinic phas...
Article
Full-text available
δ-Bi2O3 is one of the best oxygen ion conductors known. However, due to its limited thermal stability and complicated synthesis techniques, the applications are limited. Here, the synthesis of stable nano-sized δ-Bi2O3 using versatile and rapid flame spray pyrolysis (FSP) combined with in-situ Ti and/or Mn doping for an enhanced thermal stability i...
Article
A mineral intermediate between sillimanite and mullite, tentatively designated as “sillimullite,” was studied by electron microprobe analyses and single-crystal X-ray diffraction methods. The chemical compositions derived from the microprobe results and the crystal-structure refinement are Al7.84Fe0.18 Ti0.03Mg0.03Si3.92O19.96 and Al8.28Fe0.20Si3.5...
Article
We study the transformation that WO3 nanoparticles produced by Flame Spray Pyrolysis undergo when subjected to heating and cooling cycles by means of accurate in-situ XRD and HRTEM investigations supported by atomistic modeling at the level of Density Functional Theory. As-deposited particles, initially in the monoclinic phase, reversibly transform...
Article
Full-text available
Homogeneous and inclusion-free single crystals of 2:1 mullite (Al4.8Si1.2O9.6) grown by the Czochralski technique were examined by X-ray and neutron diffraction methods. The observed diffuse scattering together with the pattern of satellite reflections confirm previously published data and are thus inherent features of the mullite structure. The id...
Article
In Bragg–Brentano powder X-ray diffraction, incompletely filled sample holders result in a significant loss of intensity for diffraction peaks at small 2θ angles due to shadowing of the diffracted beam by the sample holder. This has to be considered in crystal structure refinements for samples with diffraction peaks in the low 2θ range when shifts...
Article
In this work, a simple method is presented to generate hierarchically structured monolithic types of foam with high specific surface areas and good catalytic activities in a one-step process. The materials prepared are platinum- and zinc/platinum-containing hybrid ceramics generated by the pyrolytic conversion of a mixture of a methyl phenyl polysi...
Article
Large crystals of Bi2M4O9 (M = Fe, Ga) were examined by single-crystal neutron diffraction at the Institut Laue Langevin (ILL) in Grenoble. The crystal structures of these bismuth metal oxides are commonly described as mullite-type compounds in space group Pbam. However, up to several hundreds of reflections were observed in both compounds with sig...
Article
Synthetic mullites (Al4+2xSi2-2xO10-x) belong to one of the most important groups of ceramic materials. Their crystal structure consists of chains of edge-sharing AlO6 octahedra interconnected by tetrahedral double chains of TO4 (T = Al, Si) tetrahedra. The occurrence of oxygen vacancies is associated with the formation of triclusters of TO4 groups...
Article
Full-text available
Tetraphenylphosphonium montmorillonite (TPP-MMT) was prepared from an aqueous solution of tetraphenylphosphonium bromide and a bentonite consisting primarily of sodium rich montmorillonite (Na-MMT) together with minor amounts of cristobalite, quartz and nontronite. The original bentonite, the TPP-MMT and mixtures of TPP-MMT with various amounts of...
Article
Flame spray pyrolysis (FSP) is a novel technique for the fabrication of nanostructured catalysts with far-reaching options to control structure and composition even in cases where complex composites need to be prepared. In this study, we took advantage of this technique to synthesize highly dispersed pure and Pd-doped iron oxide nanoparticles and i...
Article
Flame spray pyrolysis (FSP) has been employed for the syntheses of single crystalline WO3 nanoparticles using tungsten precursors with tungsten in usual (+6) and unusual (+4 and 0) oxidation states. The WO3 nanoparticles have been characterized by powder X-ray diffraction and the patterns have been refined using the Rietveld and the Le Bail method...

Citations

... The particle crystallite size increases with increasing Sn molar concentration, which is demonstrated by the decreasing width of the XRD peaks from 0.05 to 1 M Tin 2-EHA/Xylene solutions in Fig. 8 . The refinements of the XRD patterns were performed using BRASS program [43][44][45] . The crystallite size of these nanoparticles increase from 3, 3.6, 4.9, 5.9, 6.8, to 7.5 nm for FSP synthesis using Tin 2-EHA/Xylene solutions with Sn molar concentration increase from 0.05, 0.1, 0.25, 0.5, 0.75 to 1 mol/L, respectively. ...
... On the other hand, NOM could also act as a chelating agent to bind with the released metal ions, which might increase the dissolution of NMs. For instance, many studies have pointed out that amino acid could accelerate the dissolution of Cubased NMs due to high binding affinity between amino acids and Cu ions (Gunawan et al. 2011;Naatz et al. 2020;Wang et al. 2019b;Wang et al. 2013). Similarly, Miao et al. found that cysteine increased the dissolution of ZnO NMs (Miao et al. 2010). ...
... Over the past decades, remarkable progress has been achieved in the area of nanomaterials such as atomically precise assembled nanoclusters [13][14][15][16]. Amongst the nanoclusters, atomically precise metal nanoclusters (NCs) has explored promising potentials with fine-tuned properties [17][18][19]. ...
... The rapid dissolution of Au@CuO NPs was consistent with the previous reports owing to the complexation between Cu and amino acids. 4,16,17,38,39 In the aquatic environment, the dissolution of CuO NPs was much slower (less than 10%), 40 which suggested that CuO NPs might persist in the environment. Therefore, a much lower concentration of CuO NPs (less than mg/L) in the aquatic environment might be enough to induce the particulate effect displayed in this work. ...
... At high concentrations, the nanohybrids induced mitochondrial stress but no ROS generation, while Cu-based nano- particles are typically associated with the induction of ROS. 36,49 The lack of mitochondrial ROS also reflects a low level of dissolution of CuS. However, the observed mitochondrial stress and the increasing activity of genes related to copper suggest that free copper species are released during the bioprocessing of the nanostructures. ...
... processes (Qi et al. 2019;Lenz et al. 2019;Singh et al., 2019;Sun and Schwingenschlogl 2020). Hence, these properties are worth us exploring. ...
... The SpraySyn burner is composed of a central external-mixing twin-fluid nozzle that atomises a flammable precursor solution through a high-momentum oxygen dispersion gas flow. The precursor solution is designed according to the desired synthesised material, solution stability and cost [4,[22][23][24]. Primary and secondary atomisation processes of the precursor solution results in a spray of fine liquid droplets [14,16,17,19]. ...
... Fluoride compounds have compelling advantages which make them ideal materials for specific optical applications. A crystal of BaCaBO 3 F, a new laser material with potential for self-frequency doubling, was grown by the Czochralski method and was examined by EPMA (15 kV, 15 nA, PAP matrix correction) [439]. The researchers attempted to measure the associated boron directly but that proved unsuccessful (the measured boron content was found to be inaccurate, with too low values), so boron was included in the matrix correction assuming stoichiometry. ...
... HP studies in group-13-SOs have been conducted on the five compounds. Al2O3, also known as alumina, is by far the most studied compound [85][86][87][88][89][90][91][92][93][94][95][96][97][98][99], followed by In2O3 [100][101][102][103][104][105][106][107][108][109], Ga2O3 [107,[110][111][112][113][114], and B2O3 [115][116][117][118][119][120][121]. Finally, Tl2O3 has been the least studied compound [122]. ...
... [19][20][21][22] Spherical nanoparticles of β-Bi 2 O 3 were prepared by a hydrothermal-calcination method, solvothermal-calcination process, a single-nozzle flame spray pyrolysis method, and the Pechini method. [23][24][25][26][27] Hollow and porous microspheres of β-Bi 2 O 3 were obtained through a template-free hydrothermal method, a template-free solvothermal method, a hydrothermal synthesis method with subsequent calcination, and a thermal decomposition approach. [28][29][30][31][32] Nanosheets of β-Bi 2 O 3 were acquired by a hydrothermal-calcination method and a precipitation-calcination method. ...