Coordination Funds

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Functional materials based on inorganic nanoparticles have great application potential, e.g., as highly potent energy storage devices, noble metal-free catalysts, efficient light absorbers or materials for medical diagnostics. In fact, however, in addition to the chemical composition of the primary particles formed in the synthesis process, the morphology of the secondary and tertiary structures built upon them determines their practical applicability. In order to be able to influence and utilize these structure-based properties, highly specific synthesis is required, with which composition, structure size, morphology and structurally defined material combinations can be set in a targeted and reproducible manner. For transfer into practically usable materials, gas-phase synthesis as a continuous flow process is particularly suitable due to its scalability and its ability to generate ligand-free highly active materials. This is where the research unit FOR2284 comes in: By understanding the elementary steps of precursor chemistry, particle formation, particle-particle interaction, and in situ functionalization, design rules are developed that enable tailored synthesis, modification, and structuring of nanoparticles in the gas phase. These rules involve the selection of reactants and appropriate residence time-concentration-temperature profiles, as well as the development of transferable validated models for precursor-particle interaction. Coupling a unique range of experiments (zero-dimensional in shock tubes to three-dimensional in turbulent flows) with modeling leads to the development of robust rules. Two landmark results of the second period open up unexpected possibilities in particle synthesis, which will be intensively exploited in the third period and implemented using the available extraordinary diverse interdisciplinary toolkit. These results are: (1) Occurrence of intermediate partially oxidized particle phases: Metallic iron was detected in the flame synthesis of iron oxide, and intermediate SiO particles in the synthesis of SiO2. This unexpected result provides a highly interesting approach to (strongly) sub-stoichiometric oxides. Stabilizing these by rapid reaction interruption and coating, thus making a new class of materials accessible as a product, is a central goal of the third period. (2) Existence of small-scale steep concentration gradients due to Schmidt number effects and their impact on particle growth, coating, and aggregation: Controlling these effects by a targeted variation of the degree of turbulence in the reacting flow opens up the possibility to intervene in the morphology of both the primary particles and the coated materials. One of the central tasks of the research group is to investigate and exploit this in more detail, especially on a pilot plant scale. Integrating these aspects will make it possible to produce previously unforeseeable classes of materials in continuous flow processes.